1600 John F. Kennedy Blvd. Ste 1800 Philadelphia, PA 19103-2899 MUSCULOSKELETAL DISORDERS IN THE WORKPLACE: ISBN-13: 978-0-323-02622-2 PRINCIPLES AND PRACTICE ISBN-10: 0-323-02622-2 Copyright © 2007, 1997 by Mosby Inc., an affiliate of Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Health Sciences Rights Department in Philadelphia, PA, USA: phone: (+1) 215 239 3804, fax: (+1) 215 239 3805, e-mail:
[email protected]. You may also complete your request on-line via the Elsevier homepage (http://www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’. Notice Knowledge and best practice in this field are constantly changing. As new research and experience broaden our knowledge, changes in practice, treatment, and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose of formula, the method and duration of administration, and contraindications. It is the responsibility of the practitioner, relying on their own experience and knowledge of the patient, and to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the Editors assume any liability for any injury and/or damage to persons or property arising out of or related to any use of the material contained in this book. The Publisher
Library of Congress Cataloging-in-Publication Data Musculoskeletal disorders in the workplace: Principles and practice / [edited by] Margareta Nordin, Gunnar B.J. Andersson, Malcolm H. Pope. —2nd ed. p. ; cm. Includes bibliographical references and index. ISBN 0-323-02622-2 1. Musculoskeletal system—Diseases. 2. Occupational diseases. I. Nordin, Margareta. II. Pope, M. H. (Malcolm Henry), 1941- III. Andersson, Gunnar, 1942[DNLM: 1. Musculoskeletal Diseases—therapy. 2. Biomechanics. 3. Human Engineering. 4. Musculoskeletal Diseases—prevention & control. 5. Occupational Diseases—etiology, WE 140 M9854 2006] RC925.5M8783 2006 616.7—dc22 2006043830
Acquisitions Editor: Rolla Couchman Project Manager: Bryan Hayward
Printed in United States of America Last digit is the print number: 9 8 7 6 5 4 3 2 1
Foreword Workers’ health priorities are now driven by demographics. All of the First World Nations are facing a future with a rapidly diminishing work force, an aging population, and a growing number of pensioners. The prevention and efficient management of work place injuries and disabilities has become a priority. Medical professionals work in an increasingly specialized world brought on by an explosion of knowledge, the demand from society for "the very best" in services, and the need for expertise to keep pace with technological change and innovation. Modern medical history, in particular, is replete with examples of sudden bursts of information that challenged the growth of new domains and abilities. The period of World War II saw an explosion of medical knowledge, rapidly dividing General Surgery into numerous subspecialties. Similarly, the 1970s was a critical period in orthopaedic surgical practice as many subspecialties developed that allowed greater expert use of modern technology. Occupational orthopaedics is a relatively young specialty that is still evolving rapidly. As in sports medicine, we have learned that it is not sufficient to examine and treat injuries alone. After recovery, an injured football player is expected to return to the game and perform at his previous level of athletic ability. The injured industrial worker is also expected to return
to his or her previous level of performance, accomplishing a particular task within a reasonable time frame. Although the average orthopaedic surgeon may be well-versed with the conditions of the gridiron, he or she may not be familiar with the requirements and limitations of the industrial playing field. In industrial medicine, it is not only necessary to "fix" the worker; one must have an idea about how to fix the workplace to prevent further injury. Like sports medicine, the management and prevention of industrial injury demands a dedicated and knowledgeable cadre of physicians, surgeons, and therapists who are able to apply modern knowledge and expertise to a successful medical program. This volume brings together chapters authored by the most knowledgeable group of surgeons, physicians, scientists, ergonomists, and therapists currently addressing the prevention and management of workplace injury. The editors have assembled a most versatile and practical tool for the many allied-health professionals involved with work-related injuries. This updated text will have a strong impact within industry and on the management of patients well into the 21st century. Victor H. Frankel KNO, MD, PhD Professor of Orthopaedic Surgery, NYU President Emeritus, Hospital for Joint Diseases
v
Contributors K. N. An, Ph.D. John and Posy Krehbiel Professor of Orthopaedics Maylo Clinic College of Medicine Orthopaedics Biomechanics Lab Rochester, MN 55905
Amit Bhattacharya, Ph.D., C.P.E. Professor Biomechanics-Ergonomics Research Laboratories Department of Environmental Health University of Cincinnati Medical College Cincinnati, OH 45267-0056
Gunnar B. J. Andersson, M.D., Ph.D. Professor and Chairman Department of Orthopaedic Surgery Rush-PresbyterianSt. Luke’s Medical Center Chicago, IL 60612
Anthony M. Buoncristiani, M.D., L.T. Orthopaedics Department Naval Medical Center San Diego, CA 92134
Thomas J. Armstrong, Ph.D. Professor Industrial and Operations Engineering Director Center for Ergonomics University of Michigan Ann Arbor, MI 48109-2117 Federico Balagué Médecin Chef Adjoint Division of Rheumatology, Physical Medicine and Rehabilitation Hôpital Cantonal 1708 Fribourg Switzerland and Adjunct Associate Professor Department of Orthopaedic Surgery New York University School of Medicine New York, NY 10014 Michele Crites Battié, Ph.D. Professor Department of Physical Therapy University of Alberta Edmonton, Alberta T6G 2G4 Canada Jane Bear-Lehman, Ph.D., OTR, FAOTA Associate Professor New York University Steinhardt School of Education Occupational Therapy Department New York, NY 10012 David P. Beason, M.S. Research Engineer Laboratory Manager McKay Orthopaedic Research Laboratory University of Pennsylvania Philadelphia, PA 19104
Linda Carroll, M.D. Associate Professor Department of Public Health Sciences University of Alberta Edmonton, Alberta T6G 2E1 Canada J. David Cassidy, M.D. Department of Public Health Sciences University of Alberta Edmonton, Alberta T6G 2E1 Canada Christine Cedraschi Division of General Medical Rehabilitation & Multidisciplinary Pain Center Division of Clinical Pharmacology and Toxicology Geneva University Hospitals 1211 Geneva 14 Switzerland Mark S. Cohen, M.D. Department of Orthopaedic Surgery Rush-PresbyterianSt. Luke’s Medical Center Chicago, IL 60612 Pierre Côté, D.C., Ph.D. Scientist Institute for Work and Health Toronto, Ontario M5G 2E9 Canada
Craig J. Della Valle, M.D. Assistant Professor of Orthopaedic Surgery Rush-Presbyterian-St. Luke's Medical Center Chicago, IL 60612 James A. Dewees, M.S., C.P.E., C.E.E.S. ERGO Accommodations Inc P O Box 499 Union, KY 41091-0499 Jiri Dvorak, M.D., Ph.D. Department of Neurology Schulthess Hospital 8008 Zurich Switzerland Ulf Eklund M.D. Orthopedic Surgeon Department of Orthopedics Molndal Hospital Molndal, Sweden Freddie H. Fu, M.D. Department of Orthopaedic Surgery University of Pittsburgh Pittsburgh, PA 15203 Douglass Gross, Ph.D. Assistant Professor Department of Physical Therapy University of Alberta Edmonton, Alberta T6G 2G4 Canada Robert Gunzburg, M.D., Ph.D. Senior Consultant Department of Orthopaedics Centenary Clinic 2018 Antwerp Belgium
Benjamin Crane, M.D. Resident Department of Orthopaedic Surgery Rush University Medical Center Chicago, IL 60612
Daniel J. Habes, M.S.E., C.P.E. Industrial Engineer Industrial Hygiene Section Hazard Evaluations and Technical Assistance Branch Division of Surveillance, Hazard Evaluations, and Field Studies National Institute for Occupational Safety and Health Cincinnati, OH
James N. DeBritz, M.D. Assistant Instructor Department of Orthopaedics Georgetown University Hospital Washington, DC 20007
Robert H. Haralson, III, M.D., M.B.A. Executive Director of Medical Affairs American Association of Orthopaedic Surgeons Rosemont, IL 60018
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Contributors
Rudi Hiebert, B.S. Interim Director Musculoskeletal Epidemiology Unit Occupational & Industrial Orthopaedic Center NYU Hospital for Joint Diseases New York, NY 10014 Beat Hintermann, M.D. Chief Orthopaedic Clinic University of Basel Kantonsspital CH-4410 Liestal Switzerland David M. Kalainov, M.D. Clinical Assistant Professor Department of Orthopaedic Surgery Northwestern University Chicago, IL 60611 Dennis D.J. Kim, M.D. Associate Professor Department of Physical Medicine and Rehabilitation Montefiore Medical Center Bronx, NY 10467 Stephan Konz, Ph.D., P.E. Professor Department of Industrial Engineering Kansas State University Manhattan, KS 66506 Vicki Kristman, B.Sc., M.Sc. Ph.D. Candidate, Epidemiology Department of Public Health Sciences University of Toronto Research Associate Institute for Work & Health Toronto, Ontario M5F 2E9 Canada Shrawan Kumar, Ph.D., D.Sc., F.Erg.S., F.R.S.C. Professor Department of Physical Therapy Faculty of Rehabilitation Medicine University of Alberta Edmonton, Alberta T6G 2G4 Canada Marianne Magnusson, R.P.T., Dr.Med.Sci. Senior Lecturer Liberty Safe Work Research Centre Department of Economy and Technology Halmstad University SE-301 18 Halmstad Sweden Paul H. Marks, M.D. Associate Professor Department of Surgery University of Toronto Toronto, ON M4Y 1H1 Canada Ronald Moskovich, M.D. Assistant Professor Department of Orthopaedic Surgery NYU Hospital for Joint Diseases New York, NY 10003
Margareta Nordin, Dr.Sci. Professor Departments of Orthopaedics and Environmental Medicine School of Medicine New York University Program Director Program of Ergonomics and Biomechanics Graduate School of Arts and Science New York University Director Occupational and Industrial Orthopaedic Center (OIOC) NYU Hospital for Joint Diseases New York University Medical Center New York, NY 10014 Mooyeon Oh-Park, M.D. Clinical Associate Professor Department of Rehabilitation Medicine Montefiore Medical Center Bronx, NY 10467 Rita M. Patterson, Ph.D. Associate Professor and Deputy Director Orthopaedics Biomechanics Laboratory Division of Research Department of Orthopaedic Surgery and Rehabilitation University of Texas Medical Branch Galveston, TX 77555 David I. Pedowitz, M.S., M.D. Chief Resident Department of Orthopaedic Surgery University of Pennsylvania Philadelphia, PA 19004 Anthony Petrizzo, M.D c/o Ronald Moskovich, M.D. 301 East 17th Street New York, New York 10003 Derek Plausinis, M.D. Shoulder & Elbow Surgery Fellow Department of Orthopaedic Surgery NYU Hospital for Joint Diseases New York, NY 10003 Malcolm H. Pope, Dr.Med.Sci., Ph.D. Professor Liberty Safework Research Centre Department of Environmental & Occupational Health Foresterhill Aberdeen, Scotland AB 25 2ZD United Kingdom Laura Punnett, Sc.D. Professor Department of Work Environment University of Massachusetts Lowell Lowell, MA 01854 Robert G. Radwin, Ph.D. Professor and Chair Department of Biomedical Engineering University of Wisconsin Madison, WI 53706
David Rempel, M.D., M.P.H. Professor School of Medicine –Ergonomics Program Division of Occupational and Environmental Medicine University of California, San Francisco Richmond, CA 94804 Michiel Reneman, Ph.D, P.T. Center for Rehabilitation University Medical Center Groningen University of Groningen P.O. Box 30002, 9750 RA Haren The Netherlands Per A.F.H. Renström, M.D., Ph.D. Professor Department of Molecular Medicine and Surgery Section of Orthopaedics and Sports Medicine Karolinska Hospital SE-171 76 Stockholm Sweden Mana Rezai, H.B.Sc., D.C., M.H.Sc. Candidate Research Associate Institute for Work & Health University of Toronto Toronto, Ontario M5G 2E9 Canada Tonu Saartok, M.D., Ph.D. Department of Surgical Sciences Section of Sports Medicine Karolinska Institute SE-171 76 Stockholm, Sweden G. James Sammarco, M.D. The Center for Orthopaedic Care, Inc. Cincinnati, OH 45219-2906 Peter Sheehan, M.D. Director Diabetes Center of Greater New York Cabrini Medical Center New York, NY 10003 Ali Sheikhzadeh, Ph.D., C.I.E. Research Assistant Professor Departments of Orthopaedic Surgery and Environmental Medicine New York University School of Medicine Associate Director of Research Occupational and Industrial Orthopaedic Center NYU Hospital for Joint Diseases New York, NY 10014 Mary-Louise Skovron, Dr. PH. Group Director, Pharmaco-epidemiology Global Epidemiology Bristol–Myers Squibb 311 Pennington-Rocky Hill Road Pennington, NJ 09534
Contributors
Louis J. Soslowsky, Ph.D. Professor of Orthopaedic Surgery and Bioengineering Vice Chair for Research Director, McKay Orthopaedic Research Laboratory University of Pennsylvania Philadelphia, PA 19104 Dan M. Spengler, M.D. Professor and Chair Department of Orthopaedics and Rehabilitation Vanderbilt Orthopaedics Institute Nashville, TN 37232 Marek Szpalski, M.D. Associate Professor and Chair Department of Orthopaedics IRIS South Teaching Hospitals Free University of Brussels 1190 Brussels Belgium James B. Talmage M.D. Occupational Health Center Cookeville, TN 38501
Ross Taylor, M.D. Coastal Orthopaedic Associates Conway, SC 29526 Victor Valderrabano, M.D., Ph.D. Human Performance Laboratory and Orthopaedic Department University of Calgary Calgary, Alberta T2N1N4 Canada also Orthopaedic Department University Hospital of Basel 4031 Basel Switzerland Tapio Videman, M.D., D.Med.Sci. Professor Faculty of Rehabilitation Medicine University of Alberta Edmonton, Alberta T6G 2G4 Canada Sherri Weiser, Ph.D. Research Assistant Professor of Environmental Medicine Occupational & Industrial Orthopaedic Center NYU Hospital for Joint Diseases New York, NY 10014
Sam W. Wiesel, M.D. Professor and Chair Department of Orthopaedic Surgery Georgetown University Medical Center Washington, D.C. 20007 Harriët Wittink, Ph.D., M.S., P.T. Head Physical Therapy Professional Master Program Hogeschool Utrecht 3508 AD Utrecht The Netherlands Joseph D. Zuckerman, M.D. Professor and Chair Department of Orthopaedic Surgery NYU Hospital for Joint Diseases New York, NY 10003
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CHAPTER
1
Introduction to Epidemiologic Concepts in Musculoskeletal Disorders Mary Louise Skovron and Rudi Hiebert
The literature on the epidemiology of occupational musculoskeletal disorders is often confusing because of conflicting evidence on the importance of various potential risk or causal factors. This chapter describes basic epidemiologic methods so the reader can evaluate critically the published literature on occupational musculoskeletal disorders. Most examples are drawn from the literature on occupational low back pain, but the reader should be aware that similar methodologic standards must be applied to the literature on upper extremity disorders. Epidemiology is the study of the distribution and determinants of diseases and injuries in human populations. It consists of a developed methodology for testing scientific hypotheses in groups of individuals rather than in a laboratory setting. With knowledge of the intrinsic strengths and limitations of the design and execution of studies reported in the literature, it is possible to evaluate the strength of the evidence derived from these studies and even to make sense of conflicting results from different studies on the same topic. In this chapter we present an overview of the basic terminology used in epidemiology and the characteristics and generic strengths and limitations of analytic (hypothesis testing) study designs, with an emphasis on observational study designs. There are several types of epidemiologic studies. Descriptive epidemiology is a means of monitoring the health of a population, identifying health problems, and compiling information that can be used for the development of causal hypotheses. Analytic epidemiology is a set of epidemiologic study methods used to test specific hypotheses.
Health Administration (OSHA) by employers, workers’ compensation records, records of visits to the workplace health facility, and surveys of the work force.11 In clinical practice, the simple case count is usually derived by chart review (retrospectively) or by enrollment of patients seen during a given period (prospectively). The frequency of the disorder can also be expressed as a proportionate ratio, a ratio of cases of a particular disorder to cases of all disorders in the population of interest. In 1985 for example, occupational back injuries accounted for 26% of all closed compensation cases in a sample of nine states. By itself, numerator data cannot provide useful information regarding the risk or probability of acquiring the disorder. The case frequency has to be related to the underlying population that could have potentially developed the disorder. For example, the U.S. Bureau of Labor Statistics estimated 303,750 OSHAreportable occupational injuries involving the back in 2003.4 Without reference to the number of people at risk, it is not possible to estimate the risk of back injury in the population or to test hypotheses regarding risk factors for occupational back injury. For this reason, rates are used when the objective is to assess the risk of the disorder or determinants of disorders or their outcomes.
Rates and ratios Rates describe the frequency of a disorder or disorder per unit size of the population per unit time of observation. The rates commonly used in epidemiology are morbidity and mortality rates. The general form of a morbidity or mortality rate is
MEASURES OF DISORDER FREQUENCY The fundamental strategy of epidemiology is the analysis of relative and absolute measures of frequency and a comparison of the characteristics of individuals with and without disorder. The most obvious measures of frequency are case counts and their variations, which are often referred to as numerator data. They describe the frequency of the disorder without reference to the underlying population at risk. Examples of sources of case count data include back injury reports to the Occupational Safety and
Number of cases × 10 0 (1000, etc.) per unit time Number of persons at risk The most frequently used morbidity rates in epidemiologic research are the incidence rate and the prevalence rate. The incidence rate is based on new cases of a disorder or disorders (or new disorder events), whereas the prevalence rate is based on existing cases. Because they are based on new versus existing cases,
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Introduction to epidemiologic concepts in musculoskeletal disorders
incidence and prevalence rates have different uses and different limitations. In a sense, the incidence rate is a rate of change, the frequency with which people change from healthy to injured, sick, or disabled. Therefore the appropriate denominator is the population at risk of acquiring the disorder (i.e., those who are free of the disorder at the start of the time interval). The incidence rate may be quantified in a number of ways, for example, as the number of new events per 1000 persons per year, when the population is stable and the number of new events is counted each year. Alternatively, it may be quantified as the number of new events per 1000 person-years, as is done in prospective studies where a fixed population is followed until the disorder, the end of the study, or loss to follow-up occurs. In practice, although the best denominator for incidence rates is the number of people free of the disorder at the start of the time interval, surveillance incidence rates (and prevalence rates) that are based on case reports often use the total population derived from census data or from work-force estimates. The U.S. Bureau of Labor Statistics’ estimate of 303,750 OSHA-reportable occupational injuries involving the back represents an incidence of 3.46 new cases per 1000 workers.4 The prevalence rate is the number of existing cases of a disorder in a given population in a given time period. For example, the 1-year prevalence of disabling back pain is as high as 25%.14 Point prevalence is the number of cases per unit population at one moment of counting, for example, all persons receiving disability because of back pain in the work force of a metropolitan electrical utility company on January 1, 2005, expressed per 1000 population. For point prevalence, the unit of time is often not expressed because the period of time is effectively instantaneous. Period prevalence is the number of cases existing at one time or another during a definable time interval such as 1-year, 5-year, or lifetime prevalence. Some epidemiologists do not express prevalence as a rate because in practice it is often derived from surveys that are difficult to assign to a specific time interval. A number of factors other than the risk factor under study may affect the incidence and prevalence rates. These include demographic characteristics of the underlying population, most obviously age distribution6 because age is known to be associated with the onset of almost all disorders. Gender and ethnicity distributions must also be taken into account when incidence rates are interpreted. Other influences can distort the apparent incidence rate, including certain company policies, workers’ compensation claims, and health care system influences that affect the likelihood of seeking medical attention, of being diagnosed with a given disorder or disorders, or of having the disorder reported. These factors should be considered when measures of disorder frequency are evaluated, particularly when changes are assessed over time or different populations are compared. To eliminate the effects of differences in these factors, the rates may be adjusted or standardized algebraically. The adjusted rates express the risk of acquiring the disorder in the populations being compared as if they had the same age, sex, and ethnicity distributions. Alternatively, if it is not necessary to have a single summary index of disorder risk, the morbidity rates within population strata defined by age, sex, and ethnicity may be compared. The number of existing cases of a disorder or disorders at any time is a function of both the rate of new cases (incidence) and the duration of that disorder. Therefore, when a population is
stable and the duration of a disorder is also stable, it is possible to estimate prevalence from incidence and vice versa according to the following approximation: ~ incidence × duration Prevalence ~ Thus a change in prevalence may reflect changes in the incidence rate, duration, or both. For example, the prevalence of low back pain in a population may change because of alterations in individual, work-related, or other environmental risk factors affecting incidence rate or because treatment changes alter the duration of back pain episodes and risk of chronicity. It is occasionally the case that improved treatment extends the duration of a disorder, with the result that the prevalence increases in the face of a decreasing incidence, as occurred some decades ago with Down syndrome. The survival of infants with Down syndrome improved because of improved medical and surgical management of their associated disorders. The prevalence of Down syndrome increased, although the incidence declined as a result of prenatal screening programs.
DESCRIPTIVE EPIDEMIOLOGY The first step often undertaken in epidemiology is development of the descriptive epidemiology of a disorder or disorders. Descriptive epidemiology supports the development of causal hypotheses but does not in itself support conclusions about disorder causality or about any hypotheses. In descriptive epidemiology the frequency of a disorder in the population is characterized in terms of person (e.g., age, sex, ethnicity-specific incidence rates, economic, behavioral, occupational, and other factors), place (rural versus urban, type of housing, national variations, type of industry, job requirements), and time (long-term trend, seasonality, occasionally day of the week or time of day). The need to explain variation in descriptive studies drives the formulation of causal hypotheses. Drawing on current available information from various fields (such as anatomy, physiology, psychology, behavioral science, etc.), specific hypotheses are developed by inductive reasoning to explain observed patterns of variation and then evaluated using specific study designs to test these hypotheses. Studies that test specific hypotheses are called analytic. As the results of hypothesis-testing (analytic) studies are accrued, they are added to the basis for causal inference, depending on their strengths and generalizability, and hypotheses are supported, modified, or negated. In interpreting the evidence from all scientific sources, the rules of causal inference are applied.7 Briefly, the hypothesized cause must be demonstrated to have preceded the disorder by a length of time sufficient to allow disorder development and expression (time sequence of events). The disorder should be more common in those with the hypothesized cause than in those without it (increased risk in those exposed to the hypothesized cause), and as the intensity or duration of exposure to the hypothesized cause increases, the frequency of the disorder should increase (dose-response relationship). The association between the hypothesized causal factor and the disorder should be consistently demonstrated in methodologically sound studies and should be biologically plausible. In addition, the specificity of an association (i.e., the extent to which the hypothesized
Chapter 1
causal factor is associated with only one disease or disorder) adds weight to a causal hypothesis, but it is not necessary for causal inference; for example, cigarette smoking is accepted as a cause of lung cancer, although the association is not specific. Cigarette smoking is also associated with a number of other cancers, obstructive pulmonary disorder, heart disorder, and a variety of disorders, including osteoporosis, low back pain, and, in particular, herniated intervertebral disks.
ANALYTIC EPIDEMIOLOGY Analytic, or hypothesis-testing, epidemiology relies on two types of study designs: observational and experimental. In observational studies, exposure to the hypothesized causal factor and development of the disorder in the population under study occur in the natural course of events; the investigator does not cause them to occur. The study is designed and executed to maximize the extent to which it can be seen as a natural experiment, that is, the extent to which all extraneous sources of variation are eliminated and only the exposure to the putative cause and the frequency of disorder vary between populations being compared. It is often the case that once substantial observational evidence has accrued, causality is widely accepted. However, it is desirable in etiologic epidemiology and almost universally required in evaluations of treatment that the final test of the hypothesis is in interventional or experimental studies. In experimental studies, the investigator causes individuals or groups of individuals in the population to receive the treatment in question. To demonstrate ethically the causal role of a risk factor for which there is only observational evidence, the investigator would prevent exposure to the risk factor for a group of people. In both types of interventional design strategies, a comparison group that does not receive the intervention is necessary. All other factors that might influence the outcome of the study (potential confounding factors) can be eliminated or controlled by the investigator. Because the conditions of the study are much more under control of the investigator, interventional studies can more closely approximate true experiments than can observational studies. When such studies are well designed and executed, they provide very strong support (or negation) for a hypothesis. All analytic study designs have potential problems of internal and external validity that must be solved by the investigator either in the study design or in the data analysis. Internal validity is the extent to which a study is a true test of the specific hypothesis, that is, the extent to which all possible biases of measurement or information and all possible confounding variables are eliminated as explaining the observed study result. External validity is the extent to which the study results can be generalized to the population of interest, namely, whether the study subjects are representative of the population at risk. If the potential validity problems have been solved in either the design or analysis of the study, the study evidence is strengthened. Because it is not possible to study the entire universe of potentially eligible subjects, epidemiologic studies are conducted on samples of the population of interest. Even a study of an entire city or the work force of a company constitutes a sample. The method of sampling should not introduce selection biases. For example, a volunteer study is potentially susceptible to selection
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Analytic epidemiology
bias because the health behavior and health status of people who volunteer for research are well documented to be better than those of refusers. No characteristics of the individuals should affect the likelihood of selection for the study, including their knowledge of the question at issue; their beliefs about the risk factors or about the cause of the disorder being studied; or any characteristic such as age, sex, or education that could be independently associated with both the disorder and the hypothesized causal factor. It is important for the internal validity of the study results that the information collected is accurate and complete. If there is inaccuracy (measurement error) in the information collected, the ability to detect the association of interest is reduced. If the accuracy of the information is worse for one exposure group than for another, the effect on the study results may not be predictable. For this reason, an evaluation of the accuracy (or validity) of measurements is necessary for any study. Research reports should describe the validity of the sources of information. Questionnaires or reporting methods that have been validated in the study population or in similar populations or circumstances should be used. The problem of validity of information is particularly important in research on occupational musculoskeletal disorders because the methods of both case diagnosis13 and measurement of work exposure17 have substantial limitations. Before specific study designs can be discussed, the term confounding must be defined. Confounding occurs when the study results can be explained by a factor extraneous to the hypothesis being tested. A potential confounding factor must be associated with both the disorder in question and the hypothesized causal factor. That is, the proportion of persons with the disorder having the confounding exposure must be different from the proportion of persons without the disorder with the confounding exposure. It is also necessary that the proportion of those with the hypothesized causal factor who have the confounding exposure are different from the proportion of those not exposed to the hypothesized causal factor who have the confounding factor. For example, a study that found an association between job satisfaction and the risk of occupational back injury could be confounded by the physical requirements of work if heavy work was a risk factor for back injury and was also associated with lack of job satisfaction in the studied population. Potential confounding factors can be eliminated in the design of the study by restricted or matched sampling or, in the data analysis phase, by stratified or multivariate analysis, for example. If in the study just described the statistical analyses controlled for physical requirements of work or if the researchers conducted an exploratory analysis and found no association between job satisfaction and the physical requirements of work, the potential for confounding would be eliminated. In experimental studies, potential confounding should be successfully eliminated by truly random blind assignment of subjects to the different treatments under study. Comparability of the treatment groups should be confirmed by presentation of the baseline characteristics of each group on entry to the study. Confounding invalidates a study as a test of the hypothesis. The study’s results cannot be taken as evidence of causality or efficacy of treatment. Lack of generalizability, as opposed to confounding, does not invalidate a study’s results but merely restricts inference to populations similar to those under study.
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Introduction to epidemiologic concepts in musculoskeletal disorders
Observational study designs are applicable in both clinical and etiologic epidemiology. In etiologic epidemiology the researcher tests whether a hypothesized factor is a determinant or cause of disorder in previously healthy people, whereas in clinical epidemiology one tests whether particular characteristics, risk factors, or clinical interventions are determinants of the prognosis or outcome. The classic observational analytic study designs are the cohort study, the case-control study, and the cross-sectional study.
Risk factor present
Target population
Risk factor absent
Figure 1.1
Disease or outcome does not occur
Sample
Cohort study (Prognostic study) The cohort study is the observational design that, when well designed and executed, produces the soundest results in terms of incidence rates and disorder etiology or prognostic determinants of all the observational study designs. The hallmark of a cohort study is that a population initially free of the outcome of interest is identified and characterized with respect to the hypothesized risk factor, important covariates, and potential confounders. The population is observed for a period of time adequate for development of the disorder, and the new cases (incident cases) are recorded. Rates of disorder development are compared between those exposed and those not exposed to the hypothesized risk factor. A study of prognostic factors related to return to work after episodes of absence due to work-related low-back-pain sickness is an example of a cohort study. The cohort consisted of all those first presenting to an occupational health clinic at a large municipal transportation agency for medical clearance for sick leave from work because of a complaint of work-related low back pain. These individuals were asked to complete a questionnaire on function, pain, satisfaction with work, and beliefs about pain. The occupational physicians conducting the sickness absence clearance examinations included assessment of gain, posture, and distribution of painful symptoms specific for back pain. Participants in the study were followed for 3 months, at which time the participant’s return to work status was determined. To identify which factors best predicted return to work, rates of return to work were compared between those with high and low scores on clinical signs and symptoms, function, pain, work satisfaction, and pain beliefs. Predictors that showed large differences in rates of return to work were interpreted as being strongly predictive.12 Cohort studies can be prospective in nature, meaning that a disorder-free population or group is initially identified and then subsequently tracked over time (Fig. 1.1). This same model can also be used with historical records. Employment records, for example, can be used to identify a group of new employees at a company. Job status and medical records can then be linked to these employment records to identify work exposures and the development of the disorder of interest. Studies that use historical records are called retrospective. Loss to follow-up is a potential problem in cohort studies. If a substantial proportion of subjects are lost to the study for any reason, for example, having moved out of the region, it would be expected that fewer cases of the disorder in question would arise in the study than originally planned. The number of study cases may ultimately be too small to yield stable estimates of the incidence rates and, consequently, estimates of the relative risk.
Disease or outcome occurs
Disease or outcome occurs Disease or outcome does not occur
Cohort study.
In this case, the observed relative risk would need to be very large to support the causal hypothesis. For example, consider a cohort study examining the causal role of occupational repetitive motion in carpal tunnel syndrome. New workers hired in 1985 through 1990 are enrolled and followed forward for 10 years, with information on new cases of carpal tunnel syndrome coming from the company medical department records. If 30% of the workers retire, take disability pensions, die, get another job, or leave the company for other reasons, there is a substantial loss to follow-up. A bias in loss to follow-up occurs if the workers who leave the company are those with the highest exposure to repetitive work movements and those who leave because upper extremity problems consistent with preclinical carpal tunnel syndrome are making it more difficult for them to do the job. The observed relative risk is an underestimate of the true relative risk because the detected incidence of carpal tunnel syndrome among those with repetitive-motion jobs is lower than the true incidence and the detected incidence among those not exposed is not affected. Biased loss to follow-up leading to underestimates of incidence in the unexposed would produce an inflated observed relative risk. High proportions lost to follow-up or higher proportions lost in one exposure category than another (selective loss to follow-up) leave open the possibility of biased loss to follow-up with consequent distortion of the study findings. Another form of selection bias can occur. This bias, called selective survival or selective attrition, occurs when people who have both the exposure and the disorder have a different probability of dropping out of the population available to be included in the study than do people who are not exposed and get the disorder. This type of bias can easily occur in cross-sectional and case-control studies. It can also occur in a particular variant of the cohort study called the prevalent cohort study. For example, a prevalent cohort study examining occupational repetitive motion as a risk factor for carpal tunnel syndrome that enrolled workers who were first employed between 1985 and 1990 and were still actively employed in 2005 could be affected by selective attrition if carpal tunnel syndrome by and large developed within 15 years of employment and workers tended to leave the company when carpal tunnel syndrome developed.
Chapter 1
Some diseases or disorders take many years to develop after the initial exposure to the presumed causal factor or take many years of exposure. The duration of time between the time of exposure to the presumed causal risk factor and the development of disease or disorder is called latency. Another problem concerns the prevalence of the disorder in the population. If a disorder is rare, many thousands of subjects may be required to identify and collect enough cases where the disorder occurs to be suitable for statistical analysis. Consequently, the cohort study design is not optimal in situations where the disorder of interest is both very rare and also has a long latency period. It can be more efficient in terms of time and the number of subjects studied to address the hypothesis by means of a case-control study, as described in the next section.
Case-control study The essential feature of the case-control study that differentiates it from the other observational study types is that individuals are selected for the study on the basis of the presence of the disorder in question (cases) and compared with individuals selected for the study on the basis of the absence of the disorder under study (control subjects). The presence or absence of the hypothesized causal factor is then ascertained in both case and control subjects. Although this appears on its face to be a simple undertaking, case-control studies present a number of methodologic challenges that must be solved for the study results to be valid (Fig. 1.2). A study of ergonomic risk factors for work absence due to onset of low back pain–related sickness conducted among Baltimore City workers is an example of a case-control study.10 Two hundred cases of absence due to back pain–related sickness were identified from the city’s occupational health department. Four hundred individuals without back pain but matched on gender, job classification, and department served as control subjects. In-person interviews were conducted to collect data on demographics, work history, psychosocial and work organization characteristics,
Risk Factor present? Disease present? Yes
Yes Sample
Cases No
Population Yes No
Sample
Controls No
Figure 1.2
Case-control study.
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Analytic epidemiology
and ergonomic factors related to work. Data on these factors were categorized. To analyze these data, the ratio of those exposed to the risk factor to those not exposed was calculated once for those with back pain and again a second time for those without back pain. A risk factor was interpreted to be associated with the back pain when the ratio of having the risk factor was higher among those with back pain as compared with those without back pain. Case-control studies frequently suffer from information biases. For example, if information on exposure to the risk factor of interest comes from a different source for case and control subjects, biased exposure information is possible. Recall bias, in which a case subject is more or less likely to recall an event in the past than is a control subject, is also possible. There is also the problem of unbiased recall failure, in which subjects are asked to recall events or conditions that took place so long ago they cannot be remembered. Establishing that exposure to the factor of interest took place long enough before the outcome to be a biologically plausible determinant is difficult for certain types of hypotheses; for example, a case-control study examining preexisting degenerative disk disorder as a determinant of chronicity (symptom duration greater than 6 months) in workers with chronic back pain could not establish that the disk problem predated chronicity based on clinical or imaging examinations at the time of study. These problems are avoided if the case-control study uses exposure or prognostic information that was recorded, for example, in medical or prescription records, long enough before the disorder condition being studied to be a biologically plausible cause and to obviate recall problems. Well-designed and well-conducted case-control studies may provide evidence as robust as that of cohort studies at considerably less cost and in considerably less time. However, because of the difficulty in avoiding the problems just described, casecontrol studies often produce weaker causal evidence than do cohort studies.
Cross-sectional study Cross-sectional studies simultaneously ascertain exposure to risk factors (or the presence of prognostic factors) and the presence of the disorder or outcome in question in a population sampled without regard to the presence of either. This type of sampling is sometimes called naturalistic sampling. In contrast to a cohort study, which follows subjects over time and ascertains incidence, a cross-sectional study ascertains conditions present at the moment of study, that is, the prevalence of the disorder or outcome in question at the time of the study. The estimates of relative risk derived from cross-sectional studies are therefore estimates of prevalence relative risk. Population-based crosssectional studies of low back pain often address, among other factors, the association of the type of work (occupation, physical requirements, and so forth) with low back pain (Fig. 1.3).2 Cross-sectional or survey studies are often undertaken because, unlike case-control studies, they require few a priori decisions with regard to the selection of subjects and, unlike cohort studies, it is not necessary to wait for the study outcome. These advantages are offset by their susceptibility to some of the problems of both cohort and case-control studies. When uncommon
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Introduction to epidemiologic concepts in musculoskeletal disorders
Risk factor present disease present
Risk factor present disease absent Study population
Sample Risk factor absent disease present
Risk factor absent disease absent Figure 1.3
Cohort Study
Feature Selective Survival Recall bias Loss to follow-up Time sequence of events Time to complete Expense
+ + − + − −
CaseControl Study + − + − + +
CrossSectional Study − − + − + +/−
Cross-sectional study.
disorders or exposures are being studied, a large number of people must be included, as in cohort studies. If information on exposures or on determinants of interest is collected at the time of the study rather than from previously existing records, there can be recall biases, recall failure, and problems in establishing the time sequence of events, just as in case-control studies. Nevertheless, for relatively common disorders (outcomes) and risk factors (determinants), cross-sectional studies may be a useful first step in exploring a hypothesis. Because of their many limitations, however, cross-sectional studies rarely produce robust results for evaluating the importance of causal or prognostic factors. When the literature on a problem consists predominantly of cross-sectional studies, it is often the case that the analytic epidemiology of that problem is in its infancy. Until recently, much of the epidemiologic information on occupational low back pain was derived from descriptive and cross-sectional studies.16 In the past 5 or 6 years there has been a substantial advance in the quantity and quality of observational analytic studies of work-related back pain. The epidemiologic investigation of upper extremity disorders began later than that of low back pain. Consequently, knowledge of the risk factors for work-related upper extremity disorders is less developed. The intrinsic strengths and limitations of the basic observational study designs are summarized in Table 1.1.
Experimental study designs: clinical trials The distinction between observational and interventional study designs is that in observational designs the investigator does not
Randomize
Patients
Table 1.1 Strengths (+) and limitations (-) of the observational study designs
Eligible
Experimental treatment
Successes/ Failures
Agree
Figure 1.4
Standard treatment Ineligible
Refuse
cause the exposure to the causal factor or treatment for the purposes of the study, whereas in interventional designs the investigator does cause subjects to be exposed to different factors or treatments. Observational study designs are susceptible to treatment assignment biases in which the treatment the patients receive is influenced by certain patient characteristics (e.g., lifestyle or clinical severity) that can confound the results. Clinical trials, in which the treating physicians or the investigators control which treatment patients receive, are also susceptible to such biases. For this reason, randomized controlled trials, where only chance influences which treatment eligible patients receive, are the preferred method of evaluating therapeutic interventions. The validity of randomized controlled trials depends on all the methodologic features described for the observational study designs and more. The study must be confined to those patients who have agreed to participate. Comparisons of treatment outcomes in patients who agree to participate with those in patients who refuse to participate are not valid. Assignment of patients to treatments must be done by using accepted methods of randomization, which are described in the report, and the resulting comparability of the treatment groups on important covariates should be described, usually in a table summarizing the baseline characteristics of the treatment groups. On the occasions when, by chance, randomization does not result in comparable groups, potential confounding must be controlled in the statistical analysis. Figure 1.4 is a schematic representation of appropriate design in a randomized controlled trial. Ordinarily, in randomized trials the treating physician and the patient are blind to which treatment group the patient has been assigned. If this is not possible, assessment of the study
Successes/ Failures
Randomized control trial.
Chapter 1
outcome should be done by an independent evaluator to avoid observer and participant biases in assessing the outcome. This is particularly important when the outcome being assessed is subjective. Information should be collected in the same way and with the same frequency in all treatment groups. Eligibility and exclusion criteria should be described and be appropriate to the question being addressed. Treatments should be clearly described, and patient compliance, dropouts from the study, and complications should be described and equivalent in both groups. Finally, the outcomes studied should be appropriate to the treatment or condition in question. A number of general health status assessment measures are used, for example, the SF-36, a standardized multidimensional assessment instrument that includes functional capacity, pain, locomotion, mental status, and affect. There are numerous assessment instruments for back pain disability, including the Oswestry,5 the Roland-Morris questionnaire,15 the Quebec Back Pain Disability Scale,8 the MaineSeattle back pain disability questionnaire,1 and others.3
STATISTICAL ISSUES Methods of analysis The statistical analysis of any study result should be appropriate to the hypothesis and to the structure of the data collected. When, for instance, the study examines the difference in Oswestry scores associated with a conditioning program as compared with usual care for subacute low back pain, comparisons of the mean scores in the treatment groups may be appropriate. If it is necessary to control for pretreatment differences between the groups, the analysis uses multivariate methods such as analysis of covariance or multiple regression. Occasionally, because of the statistical characteristics of the outcome being assessed, it may be necessary to transform it (e.g., log transformation, square root transformation) and analyze the transformed variable. It is often the case that the outcome variable distribution or the conditions of the study do not conform to the requirements of the usual statistical hypothesis tests such as t-tests, analysis of covariance, and regression analysis. In these cases, a nonparametric method of statistical analysis such as the Wilcoxon method is appropriate. When the hypothesis addresses the relative frequency of an event such as a back injury rate, a ratio can be formed consisting of the risk of development of the disorder among those exposed to the risk factor compared with the risk of the disorder among those not exposed to the risk factor. This ratio is called a relative risk. When the relative risk is 1, then the risk of the disorder is the same among those exposed to the risk factor as those not exposed. However, when the relative risk diverges from 1, then the risk is not the same between the exposed and unexposed groups. This is interpreted as evidence for an association between the risk factor and the disorder. The relative risk may be adjusted for important covariates or to eliminate potential confounding. Relative risks can be calculated only in those studies where the entire study population is tracked or a representative sample is identified, as would be the case in a cohort study. A relative risk cannot be calculated in situations where the study sample is not representative (e.g., as would be the case in a
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Statistical Issues
case-control study). Instead, an alternative to the relative risk needs to be used. The odds ratio is a measure of association that, in certain circumstances, can be used to estimate relative risk. The odds ratio is the ratio of the odds of the disorder in those exposed to the odds of the disorder in those unexposed. It also has valuable statistical properties because it can be estimated by using logistic regression. The effects of confounding variables can be controlled or the simultaneous effects of several causal variables or covariates can be estimated by using multiple logistic regression. Another measure of association can be found in studies that examine the rate of the development of a disorder in a population over time. In these studies, the risk of developing a disorder within a cohort changes for each point in time. As members of the cohort develop a disorder, the total number of individuals in the cohort still free of the disorder becomes smaller and the calculation of risk changes. A survival curve shows the cumulative proportion of cohort members remaining free of the disorder on the vertical axis and time on the horizontal axis (Fig. 1.5). Typically, survival curves show an exponential relationship between cumulative proportion remaining free of the disorder and time. We can examine whether the survival experience is different between members of a cohort with different exposure profiles by using statistical tests specific for this type of analysis, such as the log-rank test.9 Hazard is a term that expresses the rate of change of the cumulative proportion surviving with time. In prognostic studies it is possible to compare whether the rate of change of survival (hazard) is different between exposure groups. A useful property of hazards is that this term can be modeled using logistic regression techniques. The Cox proportionate hazards model is used to evaluate differences in hazard between exposure groups. The hazard ratio is interpreted much like the relative risk or odds ratio. When the hazard ratio is equal to 1, then the survival experience is interpreted to be the same among exposure groups. When the hazard ratio is not equal to 1, the interpretation is that there is an association between exposure to the risk factor and survival experience related to the disorder of interest.9 An advantage of survival analysis is that all study subjects contribute information for as long as they remain in the study. The reader should be aware, however, that if the number of dropouts during the course of the study is substantial, estimates of the hazard ratio toward the end of the follow-up period are based on relatively small numbers and are consequently unstable.
Estimates and confidence limits Research is conducted on a sample of persons or other units of observation drawn from a target population. The results of any given study are estimates of the true means, proportions, relative risks, and so forth in the population from which the samples were drawn. The precision of a study estimate of the population value, or parameter, of a measurement is described by the standard error of estimate. The standard error (SE) is the square root of the ratio of the variance (s2), or variability of the measurement in the sample, to the number of subjects (N) in the study. For example,
SE mean =
s2 N
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Introduction to epidemiologic concepts in musculoskeletal disorders
Percent returning back to any work
100%
75%
50%
Figure 1.5 Return to any work from sick absence because of nonspecific low back pain (n = 225). (From Hiebert R, Skovron ML, Nordin M: Work restrictions and outcome of nonspecific low back pain. Spine 28(7): 722-728, 2003. Reprinted with permission.)
25%
0% 0
90
180
270
364
Time lost from work because of LBP (in days) No restrictions Some restrictions
Variance is affected by a number of factors, including interindividual variability, intraindividual variability (such as diurnal variations), and instrument variability. Designing or executing a study to reduce any of these components reduces the variance of the measurement, thus reducing the standard error and increasing the stability of the estimate of the population parameter. The larger the number of subjects on whom the estimate is based, the smaller the standard error and the more confident we can be in its representation of the population parameter. Because sample results are estimates of population parameters, it is increasingly becoming the standard of reporting to describe the precision of the estimates as a range within which the population parameter probably lies. This is the confidence limit around the estimate and is by convention expressed as the 95% confidence limit. For example, the 95% confidence limit for a mean is approximated by 95% confidence interval = mean ± 2(SEmean)
Statistical hypothesis testing Because there is always sampling error, estimates may be expected to vary from sample to sample. Consequently, study results must be subjected to statistical hypothesis testing; that is, study results must be tested to determine the probability that the observed results from a specific study could have occurred by chance alone. The statistical hypothesis test evaluates the null hypothesis that the observed study results occurred because of sampling error when there was no true association in the population from which the study subjects were sampled. The probability of making this type of error is designated as alpha (α). If the observed association is large enough that this kind of error is improbable, the null hypothesis is rejected. The investigators then accept the alternative hypothesis, that the observed estimates of relative risk
or differences between treatments reflect the true situation in the population from which the samples were drawn. By convention, the cutoff for rejecting the null hypothesis is usually set at 0.05. Then if the probability (p value) that the observed results are due to sampling error is less than 0.05, that is, less than α, the null hypothesis is rejected and the results are declared statistically significant. Thus, statistically significant results are simply results that we have decided, within an acceptable margin of error, probably did not occur by chance. Further, the larger the observed association relative to the underlying variability of the outcome being measured, the more likely that it will be declared statistically significant.
Statistical power and sample size Statistical hypothesis tests actually involve two probabilities. The probability of making a type I error by incorrectly rejecting the null hypothesis, that is, by declaring an observed association to be statistically significant when in fact it is the result of sampling error, is referred to as α, as described in the preceding paragraph. There is also the probability of incorrectly accepting the null hypothesis; that is, declaring that the study results are due to sampling error (not statistically significant) when in fact they reflect a true association in the population from which the study subjects were drawn. This is the type II error and its probability is beta (β). The complementary probability that a study will be able to correctly reject the null hypothesis when it is false, that is, correctly detect an association when there is one in the population at large, is referred to as statistical power (1 – β). Table 1.2 illustrates the different conditions and possible results of a statistical hypothesis test. In the planning phase of research the investigators should make a determination of how strong an association would be clinically significant, that is, how large an estimated relative risk
Chapter 1
Table 1.2 Population conditions, statistical hypothesis test results, error types, and designations Hypothesis Test Result
Population Condition
Accept null hypothesis NULL HYPOTHESIS TRUE No association NO ASSOCIATION Correct Reject null hypothesis Type I error (alpha) Association exists
NULL HYPOTHESIS FALSE ASSOCIATION EXISTS Type II error (beta) Correct
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References
result should be specified, the plan of statistical analysis determined, and the necessary number of study subjects defined. Study management should avoid the introduction of differential loss to follow-up, unblinding, and other potential problems. The statistical analysis should be appropriate to the structure of the data and to the hypothesis. Finally, although the discussion should place the study in the context of other work and what is already known about the question, the specific conclusions should not go beyond what was actually tested.
REFERENCES or how big a difference between treatments. Because the validity of the study requires that it be a true test of the research hypothesis, it is important to design the study so that a clinically significant association will have a good chance of being declared statistically significant, that is, so that the study has sufficient power to detect a clinically significant association. The larger the sample size, the more power the statistical test has to detect associations; in other words, as expected differences or relative risks get smaller, the number of subjects studied must increase to have adequate power to test the hypothesis. Conversely, with very large numbers of study subjects it is possible to declare trivial associations statistically significant. When studies with small sample sizes report results that are not statistically significant, they should also report how large an association would have been required for there to have good power to detect it. The reader should also evaluate whether the observed difference and its upper confidence limit, although not statistically significant, are clinically significant. When studies with huge numbers of subjects report statistically significant results, the reader should decide whether the differences are trivial in clinical terms, even though they are statistically significant.
1.
2.
3.
4. 5. 6. 7. 8. 9. 10. 11.
SUMMARY
12.
The validity of clinical research depends on a number of factors. The hypothesis must be formulated specifically enough to be testable. The appropriate study subjects should be eligible, and there should not be differential participation. The information collected should be appropriate to the hypothesis and accurate. The study design and information sources should avoid potential information biases. Potential confounders should be eliminated in the study design or controlled in the statistical analysis. At the time the study is designed, a clinically significant hypothesized
13.
14. 15.
16. 17.
Atlas SJ, Deyo RA, van den Ancker M, Singer DE, Keller RB, Patrick DL: The Maine-Seattle back questionnaire: a 12-item disability questionnaire for evaluating patients with lumbar sciatica or stenosis: results of a derivation and validation cohort analysis. Spine 28(16):1869-1876, 2003. Bernard BP, ed: Musculoskeletal disorders and workplace factors: a critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. U.S. Dept. of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention. Cincinnati, OH, 1997, National Institute for Occupational Safety and Health. Bombardier C: Outcome assessments in the evaluation of treatment of spinal disorders: summary and general recommendations. Spine 25(24):3100-3103, 2000. Bureau of Labor Statistics, US Labor Department, Annual Survey 2003, Tables R19, 22. Fairbank JC, Pynsent PB: The Oswestry Disability Index. Spine 25(22):2940-2952; discussion 2952, 2000. Gyntelberg F: One-year incidence of low back pain among male residents of Copenhagen aged 40-59. Danish Med Bull 21:30-36, 1974. Kelsey JL, Thompson D, Evans AS: Methods in observational epidemiology. New York, 1986, Oxford University Press. Kopec JA, Esdaile JM, Abrahamowicz M, et al: The Quebec Back Pain Disability Scale: measurement properties. Spine 20(3):341-352, 1995. Lee E: Statistical methods for survival data analysis. Belmont, CA, Lifetime Learning Publications, 1980, Wadsworth Inc. Myers AH, Baker SP, Li G, et al: Back injury in municipal workers: a case-control study. Am J Public Health 89(7):1036-1041, 1999. National Research Council and the Institute of Medicine. Musculoskeletal disorders and the workplace: low back and upper extremities. Panel on Musculoskeletal Disorders and the Workplace. Commission on Behavioral and Social Sciences and Education. Washington, DC, 2001, National Academy Press. Nordin MN, Skovron ML, Hiebert R, et al: Early predictors of delayed return to work in patients with low back pain. J Musculoskel Dis 5(2):5-27, 1997. van den Hoogen HM, Koes BW, van Eijk JT. On the accuracy of history, physical examination, and erythrocyte sedimentation rate in diagnosing low back pain in general practice. Spine 20:318-327, 1995. Praemer A, Furner S, Rice DP: Musculoskeletal conditions in the United States. Rosemont, IL, 1999, American Academy of Orthopaedic Surgeons. Roland M, Morris R: A study of the natural history of back pain. Part I. Development of a reliable and sensitive measure of disability in low-back pain. Spine 8(2): 141-144, 1983. Skovron ML: Epidemiology of low back pain. Baillieres Clin Rheumat 76:559-573, 1992. Winkel J, Mathiassen SE: Assessment of physical work load in epidemiologic studies: concepts, issues and operational considerations, Ergonomics 37:979-988, 1994.
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2
Psychosocial Aspects of Work-Related Musculoskeletal Disorders: Clinical Implications Sherri Weiser
Until recently, attempts to unravel the mystery of work-related musculoskeletal disorders (MSDs) concentrated on the physical demands of the job and the physical vulnerabilities of the worker. It became clear that this problem did not easily lend itself to reductionistic approaches. Although certain physical loads and tasks have been associated with the development of musculoskeletal problems, the strength of these associations has been disappointingly weak.29 Furthermore, a determination of physical vulnerability before injury is nearly impossible. Even when a physical defect such as disk herniation has been established in conjunction with a report of pain, the correspondence with actual disability is often low. Like all human conditions, MSDs can be infinitely complex. A thorough understanding of these disorders requires a consideration of influences beyond the physical. The worker’s psychologic attributes and social reality may have significant bearing on the onset, progression, and outcome of occupational MSDs. A biopsychosocial perspective offers much in the way of understanding these disorders. Adoption of the biopsychosocial model in pain and disability research has resulted in the identification of specific psychologic and social aspects of MSDs. Recently, this research has been summarized in a number of excellent review articles and treatment guidelines, conclusions from which are discussed. The biopsychosocial model implies not just the inclusion of psychologic and social considerations but a new perspective on the part of all stakeholders involved in the prevention and treatment of MSDs. This chapter describes how to achieve the goal of preventing and treating the disorder in practical terms.
THE BIOPSYCHOSOCIAL MODEL The notion of a link between the mind and body has existed throughout history. It was Walter Canon,2 however, who substantiated this idea with his scientific explanation of the “fight or flight” response. His research identified the organism’s physical reactions to psychologic stress. Selye24 later showed how these responses, if left unchecked, can over time cause severe damage
to vulnerable organs and body systems and may even cause death. Today, the relationship between the mind and the body is studied extensively. Psychologic factors have been shown to affect a spectrum of diseases involving virtually all bodily organs and systems.8 First described by Engel in 1977,5 the biopsychosocial model extends beyond mind and body to include the impact of social factors on illness. Influenced by models of stress and illness, Engel concluded that any illness must be viewed from a multidimensional perspective that takes biologic, psychologic, and social factors into consideration.5 Furthermore, these factors are not independent, as a medical model would suggest, but interrelated. It was by understanding this perspective, Engel believed, that physicians would be prepared to take on the complexities of health and illness. The biopsychosocial model soon became the prevailing view among those involved in pain research. In 1965 the gate control theory outlined the channels of pain transmission through neurologic pathways.19 This theory further asserted that pain transmission may be modulated by cognitive and affective states. This model was fundamental in explaining the disparities between physical findings and the phenomenologic experience of pain. The gate control theory laid the groundwork for modern approaches to treating chronic pain. In 1992, Waddell28 presented a detailed analysis of low back pain with the use of a biopsychosocial model (Fig. 2.1). The many levels on which pain is experienced are defined in the model. The physical injury is interpreted cognitively, resulting in a corresponding emotion. A man who believes that he has a herniated disk, for example, is more apt to be anxious and depressed than a man who believes that he has a sprain. The man with the “herniated disk” may also display more avoidance behavior initially than the man who believes he sprained his back. This process takes place within a social context that is constantly providing feedback and modifying the individual’s response. Waddell also pointed out that feedback loops exist among all levels in the model and that a change in one component affects the others. If the man with the supposed herniation sees a physician and is assured that the problem is only a sprain, his belief has changed. As a result, his affect and pain behavior will change,
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Psychosocial aspects of work-related musculoskeletal disorders
Social environment
PSYCHOLOGIC AND PSYCHOSOCIAL FACTORS ASSOCIATED WITH MSDs Illness behavior
Affective
Cognitive
Sensory
Figure 2.1 A cross-sectional analysis of the clinical findings and assessment of low back pain and disability at one point in time. (From Waddell G: Biopsychosocial analysis of low back pain. In M Nordin, TL Vischer, eds: Common low back pain: prevention of chronicity. London, 1992, Bailliere Tindall.)
and nociception may be experienced as less severe. These feedback loops are particularly important in chronic low back pain, wherein the original injury is often resolved. In these cases, psychologic and social variables are even greater determinants of functional status than in cases of acute back pain when nociception is responsible for much of the illness behavior. Occupational musculoskeletal injuries are clearly amenable to biopsychosocial analysis. They either occur at work or are believed to be its result. The cognitive, affective, behavioral, and social elements of such an injury are therefore inextricably related to the workplace. Injuries or disorders that did not occur at work may also be considered work-related if attitudes or beliefs about work affect recovery. If an injured worker fears that returning to work will exacerbate an injury, for example, recovery may be delayed. Recently, a number of studies have demonstrated the impact of psychologic and social factors on occupational musculoskeletal injuries. What has emerged is evidence that these factors have as much, and in some cases more, predictive value as physical and environmental factors. The main findings from recent critical review articles and current studies are discussed below. Most of the articles refer to nonspecific disorders of the spine; research has centered on these conditions because they account for most of the associated costs and suffering caused by the disorder. Some reviews include the upper extremities as well. To date, no high quality study of workrelated lower extremity injuries that explores psychosocial factors has been found.
Psychologic factors refer to cognitions or beliefs about pain and disability and affective or emotional responses, whereas psychosocial factors reflect an individual’s perceptions of others and the environment. Recent systematic evidence-based reviews have concluded that even when measured early in the injury, both these factors are stronger predictors than physical factors of outcomes such as work status. The Clinical Guidelines for the Management of Acute Low Back Pain, published in 2001, state that in addition to social and economic factors, psychologic factors play an important role in the development of chronic low back pain and disability and influence a patient’s response to treatment and rehabilitation.30 Specifically, beliefs that activity and work will make pain worse (fear-avoidance beliefs) and that the patient is not responsible for the pain or treatment along with behaviors intended to communicate that the patient is in pain (illness behaviors) are associated with poor outcome. Using strict inclusion criteria, in 2001 Koes et al13 published a comparison of clinical guidelines for the management of low back pain from 11 different countries that appeared from 1994 until 2000. They found that in most regards the content of the guidelines appeared to be quite similar and that all recognized the importance of psychologic and psychosocial factors, including work perceptions, in the development and maintenance of low back pain. Indeed, the New Zealand Guidelines for assessing acute low backpain, updated in 2003, likewise finds good agreement that beliefs, mood states, and behaviors, such as those identified by Waddell et al,29 consistently predict poor outcome.21 One of these is the belief that work will make the pain worse, evidence for which is so compelling that investigators have labeled this risk factor one of the “yellow flags.” Yellow flags are defined as factors that may increase the risk of developing or perpetuating long-term disability and work loss associated with low back pain. The New Zealand group recommends their assessment as early as 2 weeks after injury. Occupational health guidelines for low back pain were published in 2001. Although the effect size was small, strong evidence was found that psychosocial factors are associated with the risk of onset of low back pain in symptom-free workers. In the workplace, psychosocial factors are stronger predictors of care seeking and disability than clinical symptoms or physical work demands. Specifically, negative work perceptions were risk factors for symptom reports, health care utilization, and work loss. The most important factors associated with delayed recovery and response to treatment were beliefs that work caused the pain and expectations about recovery.29 A comparison of international occupational low back pain guidelines shows them in complete agreement that the early assessment of these risk factors was important if the patient exceeds the expected recovery time.25 Other reviews of factors affecting low back pain outcomes show similar results but call for more stringent scientific investigation of the interrelationships. For example, Hoogendoorn et al10 reviewed the literature and found that low workplace social support and low job satisfaction were related to reports of
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What is the relationship between psychosocial factors and work-related MSDs
back pain, but most studies failed to adjust for psychosocial work characteristics and physical load at work. Crook et al4 determined from their review that among other factors, psychologic distress and work environment characteristics were important prognostic factors. They noted, however, that most studies failed to investigate interactions among psychologic, social, and physical variables. Likewise, Pincus et al23 noted a lack of rigorous prospective studies that evaluated the role of psychologic factors in the development of chronicity. Of 25 publications, only 6 met their acceptability criteria for review. Depression, distress, and to a lesser extent somatization were the psychologic factors most strongly linked to low back pain disability. Catastrophizing by disabled workers as a coping strategy received weak support. The role of coping in conjunction with psychologic factors remains unclear. Although there are fewer studies on upper extremities than on back pain, thus far similar factors seem to be related to both disorders. In another review article, higher levels of perceived job demands and stress were the psychosocial factors most consistently linked to upper extremity disorders. Epidemiologic reviews revealed also that psychosocial factors unrelated to work, such as general worry/psychologic tension, depression/anxiety, general coping style, and response to pain, are likewise associated with both back and upper extremity disorders.15 Systematic reviews on this topic have not, however, been conducted. An interesting study by Ijzelenberg et al11 investigated whether individual, work-related physical, and psychosocial risk factors involved in the occurrence of musculoskeletal complaints also determined musculoskeletal sickness absence. Using a crosssectional study design and self-administered questionnaire, investigators collected data on individual and work-related risk factors and the occurrence of musculoskeletal complaints and musculoskeletal sickness absence among 373 employees of laundry-works and dry-cleaning businesses. Results show that both work-related physical factors and psychosocial factors showed strong associations with low back pain and upper extremity complaints. Workrelated physical factors did not influence sickness absence, however, whereas psychosocial factors showed some associations with it. This finding supports the notion that illness behaviors such as work absence are modified by cognitive and affective responses to physical symptoms in neck and back disorders. Linton15 systematically reviewed numerous studies of variable methodologic quality that looked at the effects of various psychologic factors on neck and back pain and concluded that there is a clear link. Prospective studies indicate, furthermore, that psychologic variables are related to the onset of pain and to all of its phases: Certain factors such as distress, anxiety, cognitive functioning, and pain behavior were found to be significant at all stages from acute to chronic pain. Still, psychologic factors account for only a portion of the variance, underscoring the importance of a multidimensional view. Luo et al16 found a variety of factors, including general stress, depression, and anxiety, to be associated with neck pain disability. Carroll et al3 confirmed the role of depression as a risk factor for pain onset. They followed a population-based random sample of adults and assessed them at 6 and 12 months. Controlling for demographic and socioeconomic factors, health status, comorbid medical conditions, and injuries to the neck or low back,
they found an independent and robust relationship between depressive symptoms and onset of a pain episode. They concluded that depression is a strong and independent predictor for the onset of an episode of intense and/or disabling neck and low back pain.
WHAT IS THE RELATIONSHIP BETWEEN PSYCHOSOCIAL FACTORS AND WORK-RELATED MSDs? There are a number of ways to explain the effect of psychosocial factors on MSDs. Perhaps the most straightforward explanation is that workers who are depressed or dissatisfied at work simply report more symptoms and disability than those who are content at their jobs. Distress in life and work may cause extra attention to be paid to symptoms, and therefore the signs are experienced as more troubling. This does not imply that workers are intentionally making more of symptoms than is warranted but that they are more likely to notice symptoms that can distract them from their daily routines. Another popular explanation is that stress results in increased muscle tension, causing spasms and ischemia, a painful condition resulting from oxygen reduction and the release of painproducing chemicals. Over time this pain may cause more distress, leading to a chronic cycle of stress and pain. Some laboratory studies have demonstrated an increase in muscle activation under stress,18 but findings have been inconsistent among patients with chronic pain. This may be because stress-induced muscle tension has a role in the development of chronic pain, but once patients are chronic their reactivity to stress becomes altered in ways that are unclear at present. The National Research Council and the Institute of Medicine reviewed evidence for the relationship between psychologic and physical factors and concluded that data exist to support a direct role of the central nervous system.20 This may help to explain how psychologic processes such as attention and emotion influence pain and its tolerance, an explanation supported by studies showing that pain is linked to a tendency to somatize or focus on symptoms.17 Other theories mentioned in the review include physiologic changes that occur under stress and result eventually in musculoskeletal pain. Stress hormones may facilitate the transmission of painful stimuli; physically stressful work tasks are associated with an increased release of stress hormones and slower recovery times. One reason for this may be that stress hormones affect the health of muscles, tendons, and ligaments and impede inflammatory or immune responses. Other factors such as behavior or life-style may moderate the effects of stress on muscle tension and biochemical changes. The concept of “work style” has been proposed to define how individuals interact with work demands.6 Originally proposed to explain work-related upper extremity disorders, work style is defined as cognitive, behavioral, and physiologic components of the stress response expressed behaviorally in movement, posture, and activity. Workers who respond to physical or psychologic workplace demands with a “high-risk” work style display excessive attempts to cope with stress and are susceptible to its negative
15
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Psychosocial aspects of work-related musculoskeletal disorders
consequences such as continuous arousal or reactivity. Similarly, Marras et al18 found that characteristic ways of responding to the environment were predictive of spinal loading. During a lifting task, introverts tend to exhibit muscle coactivation and alteration in movement patterns higher than those of extroverts. Stress-related behaviors such as these have been linked to symptom severity, functional limitations, and work disability.9 It is clear that the relationship between psychologic distress and physical responses is not simple. More research is needed to develop detailed models of the stress–pain relationship. Although various pathways have been proposed, there is a need to understand causal pathways and interactions among stresses and responses. Most likely there is no simple explanation of this relationship, and these proposed pathways are not mutually exclusive but work together in an ongoing dynamic way to result in MSDs. It is possible also that the stress pathways discussed here have variable influences in different stages of pain. What began as pain related to muscle tension, for instance, may over time develop into neuropathic pain. In addition, more clarity is needed in defining outcome measures, because different factors may moderate stress and physical complaints, sick absences, and disability.
PSYCHOSOCIAL INTERVENTIONS FOR MSDs
Physicians should share with distressed patients information about treatment philosophies and their possible outcomes. At the very least, physicians should be aware of the treatment philosophy of any facility to which they are referring patients, ideally one that adheres to current guidelines for the treatment of acute low back pain. The occupational health guidelines for the management of low back pain summarize recommendations for physicians to minimize the likelihood of chronic problems29: ● Reassure the worker and provide adequate information about the self-limiting nature and good prognosis of lower back pain. ● Advise the worker to continue normal activity and work or to return to them as soon as possible, even if there is still some pain. ● Because most workers with lower back pain manage to return to more or less normal duties quite rapidly, consider temporary adaptations of work duties or hours only when necessary. ● If a worker fails to return to work within 2-12 weeks (different guidelines vary considerably about the time scale), refer him or her to a gradually increasing exercise program or multidisciplinary rehabilitation (exercises, education, reassurance, and pain management following behavioral principles). These rehabilitation programs should be embedded in an occupational setting.
Most individuals at risk for MSDs can be effectively managed by their usual treatment provider, without the need for referral to a psychologist. Appropriate information and advice from the physician can reduce anxiety and improve patient satisfaction with care. Every encounter with health care professionals and medical management systems provides an opportunity for intervention. Waddell28 astutely observed the powerful effects a physician can have on the patient. Information that is vague, incomplete, or incomprehensible to a lay person can render the patient confused, helpless, and afraid. In the mind of a patient, the diagnosis of a herniated disk, for example, can be a sentence to disability. Diagnostic film results are often held up as proof by patients fearful of permanent disability. It is the health care provider’s responsibility to explain the implications of any diagnosis in terms the patient can understand. In the case of disk herniation, the patient needs to know that pain and disability are often self-limiting and that many people with this condition maintain their usual life-styles. Making sure that the patient has a realistic picture of the diagnosis and the prognosis is the first step. Patients who seem overly distressed can be questioned about other life circumstances. When the injury is work related, questions about work are particularly important. Often, patients feel residual anger toward the employer, sometimes believing that it is the employer’s responsibility to make sure they get well. Even if not responsible for their injuries, patients who understand the normal course of low back pain and are encouraged to take responsibility for their recovery from the onset may be spared the ordeal of becoming a compensation failure. Primary health care professionals have a responsibility also to make appropriate referrals. Information given by the physician can be reinforced or contradicted by secondary caregivers. One of the major causes of distress, contradictory information can lead to endless doctor shopping and prolongation of recovery.
Based on the conclusion that active care is superior to passive therapy, treatment guidelines recommending active and goal-oriented physical therapy should be the first course of treatment. Research has shown that the specific type of exercise prescribed is less important that the overall therapy philosophy. The objective should be to increase gradually the individual’s capacity for work with a balanced strength, flexibility, and cardiovascular program. Specific goal setting ensures that improvement is monitored, whereas positive feedback rewards productive behavior. The easiest program to implement early in treatment, a behavioral approach pioneered by Fordyce,7 consists of time-contingent care in which medication levels, exercise goals, and duration of treatment are preset and not determined by the patient. The idea is to provide environmental contingencies that reinforce “well” behavior and ignore “pain” behavior. In a benchmark study, Fordyce7 compared this approach with traditional care in which patients were told to “let pain be your guide.” Subjects with back pain for less than 10 days were randomly assigned to one of the two protocols and were followed at 6 weeks and 9 to 12 months after treatment. Although no differences were noted at 6 weeks, long-term follow-up showed significantly greater improvement in functioning for the treatment group. Like MSDs, physical therapy may be viewed from a biopsychosocial perspective. In contrast to passive modalities, an active approach shifts the responsibility to patients and provides techniques that they can use themselves to maintain fitness. As such, it increases the patient’s sense of control and may be instrumental in changing negative beliefs about pain. With improvement, the patient’s fears of returning to work should subside. After 2 weeks, patients who are not achieving weekly goals should be referred for a psychosocial evaluation. If warranted, they can begin a multidisciplinary program that addresses psychosocial issues. By their very nature these types of programs address physical, psychologic, and social concerns simultaneously.
Chapter 2
A multidisciplinary approach in treating patients with chronic pain is fairly standard,31 but the application of a biopsychosocial model in the acute and subacute phases of treatment as well is gaining popularity.
EVIDENCE No randomized controlled studies have assessed the use of psychologic interventions alone for MSDs, and high-quality studies that assess the effectiveness of multidisciplinary care for
Onset of pain • Explain the biopsychosocial model • Address concerns about pain, including the course, diagnosis, and prognosis • Emphasize the patient's role in recovery • Make appropriate referral if indicated
Four weeks after • Address concerns again, old and new • Address social factors again • Reinforce patient's role in recovery again • Refer for multidisciplinary evaluation and possible treatment Figure 2.2
●
Evidence
occupational MSDs in general are few. Nonetheless, in line with international opinion, expert panels have recommended the use of multidisciplinary team management for episodes of acute low back pain that is unresolved between 2 and 6 weeks, when patients risk chronic disability. Evidence clearly shows that multidisciplinary teams or networks are effective in managing chronic back pain,14,22,27 but their effectiveness for returning chronic patients to work remains unclear. Some studies showed good outcomes for chronic low back pain patients who are highly motivated to return to work,1 but randomized trials have yet to be done.
Two weeks after • Address concerns again, old and new • Address social factors including attitudes about work, as well as family and friends' responses to pain • Reinforce patient's role in recovery again • Make appropriate referral if indicated
Seven weeks after • Address concerns again • Address social factors again • Reinforce patient's role in recovery • Refer for multidisciplinary evaluation and treatment
Application of the biopsychosocial model: general guidelines for primary health care providers.
17
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Psychosocial aspects of work-related musculoskeletal disorders
Karjalainen et al12 conducted a Cochrane review of multidisciplinary programs for subacute low back pain patients. They concluded that “there is moderate evidence of positive effectiveness of multidisciplinary rehabilitation for subacute low back pain and that a workplace visit increases the effectiveness.” This endorsement is guarded because the only two articles that fit their inclusion criteria were only of moderate quality. However, more support for this treatment in the subacute phase was provided by van den Hout et al.26 In a randomized study, they showed that adding training in problem solving to a graded activity program improved outcome. The Work Loss Data Institute considered but did not recommend multidisciplinary or cognitive-behavioral treatment for upper extremity pain due to lack of studies.32 New studies should consider other MSDs as well. Future research would benefit also from a comprehensive multivariate causal model that would allow the assessment of interactions among psychologic, social, and physical variables. Adjustments for workload could be made when studying the effects of other factors; such a model would also permit an understanding of how these risk factors emerge during the transition from acute to chronic problems.
SUMMARY Traditional treatments for occupational MSDs have fallen short of expectations. The biopsychosocial model goes beyond physical factors to include psychologic and psychosocial elements that affect the worker before and after an injury. Investigations into the practical application of this model are most convincing. Studies have shown that psychosocial factors are at least as important as and often more important than physical factors in determining disability. Programs that have attempted to prevent injury or chronicity associated with occupational low back pain have flourished when they include a biopsychosocial framework. Though more research is needed, it is suggested that our best option is for primary health care providers and all health care practitioners to apply a biopsychosocial model in the same fashion for all MSDs that do not respond to traditional care (Fig. 2.2). Because we all share the burden of disability, we must all share in the solution. Much can be done by all medical professionals to make this process easier and more successful for everyone. For physicians, establishing a good rapport with the patient, giving clear and intelligible information, encouraging an active approach to treatment, and making appropriate referrals at the first sign of delayed recovery can go a long way toward reducing occupational MSDs. Physical therapists can follow a behavior model of active care that encourages patient responsibility for outcome and reinforces function over pain.
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Crook J, Milner R, Schultz IZ, Stringer B: Determinants of occupational disability following a low back injury: a critical review of the literature. J Occup Rehabil 12(4):277-295, 2002. Engel GL: The need for a new medical model. Science 196:129-136, 1977. Feuerstein M: Workstyle: definition, empirical support, and implications for prevention, evaluation, and rehabilitation of occupational upper-extremity disorders. In SD Moon, SL Sauter, eds: Beyond biomechanics: psychosocial aspects of musculoskeletal disorders in office work. Bristol, PA, 1996, Taylor & Francis, pp. 177-206. Fordyce WE: Acute back pain: a control group comparison of behavioral vs. traditional management methods, J Behav Med 9:127-140, 1986. Goleman D, Gurin D, eds: Mind body medicine: how to use your mind for better health. New York, 1993, Consumer Reports Books. Haufler AJ, Feuerstein M, Huang GD: Job stress, upper extremity pain and functional limitations in symptomatic computer users. Am J Ind Med 38(5):507-515, 2000. Hoogendoorn WE, van Poppel MN, Bongers PM, Koes BW, Bouter LM: Systematic review of psychosocial factors at work and private life as risk factors for back pain. Spine 25(16):2114-2125, 2000. Ijzelenberg W, Molenaar D, Burdorf A: Different risk factors for musculoskeletal complaints and musculoskeletal sickness absence. Scand J Work Environ Health 30(1):56-63, 2004. Karjalainen K, Malmivaara A, van Tulder M, et al: Multidisciplinary biopsychosocial rehabilitation for subacute low back pain among working age adults. Cochrane Database Syst Rev (3):CD002193, 2000. Koes BW, van Tulder MW, Ostelo R, Burton K, Waddell G: Clinical guidelines for the management of low back pain in primary care: international comparison. Spine 26(22):2504-2513, 2001. Koopman FS, Edelaar M, Slikker R, Reynders K, van der Woude LH, Hoozemans MJ: Effectiveness of a multidisciplinary occupational training program for chronic low back pain: a prospective cohort study. Am J Phys Med Rehabil 83(2):94-103, 2004. Linton SJ: A review of psychological risk factors in back and neck pain. Spine 25(9):1148-1156, 2001. Luo X, Edwards CL, Richardson W, Hey L: Relationships of clinical, psychologic, and individual factors with the functional status of neck pain patients. Value Health 7(1):61-69, 2004. Main CJ, Wood PL, Hollis S, Spanswick CC, Waddell G: The distress and risk assessment method: a simple patient classification to identify distress and evaluate the risk of poor outcome. Spine 17(1):42-52, 1992. Marras WS, Davis KG, Heaney CA, Maronitis AB, Allread WG: The influence of psychosocial stress, gender, and personality on mechanical loading of the lumbar spine. Spine 25(23):3045-3054, 2000. Melzack R, Wall P: Pain mechanisms: a new theory. Science 150:971-979, 1965. National Research Council and the Institute of Medicine: Musculoskeletal disorders and the workplace: low back and upper extremities. Panel on Musculoskeletal Disorders and the Workplace. Commission on Behavioral and Social Sciences and Education. Washington, DC, 2001, National Academy Press. New Zealand Guidelines Group: New Zealand acute low back pain guide. Wellington, NZ, October 2004, Accident Compensation Corporation. Patrick LE, Altmaier EM, Found EM: Long-term outcomes in multidisciplinary treatment of chronic low back pain: results of a 13-year follow-up. Spine 29(8):850-855, 2004. Pincus T, Burton AK, Vogel S, Field AP: A systematic review of psychological factors as predictors of chronicity/disability in prospective cohorts of low back pain. Spine 27(5):E109-E120, 2002. Selye H: The stress of life. New York, 1956, McGraw-Hill. Staal JB, Hlobil H, van Tulder MW, et al: Occupational health guidelines for the management of low back pain: an international comparison. Occup Environ Med 60(9):617, 2003. van den Hout JH, Vlaeyen JW, Heuts PH, Zijlema JH, Wijnen JA: Secondary prevention of work-related disability in nonspecific low back pain: does problem-solving therapy help? A randomized clinical trial. Clin J Pain 19(2):87-96, 2003. van Tulder MW, Ostelo RWJG, Vlaeyen JWS, Linton SJ, Morley SJ, Assendelft WJJ: Behavioural treatment for chronic low-back pain (Cochrane Review). In The Cochrane Library, Issue 3. Chichester, UK, 2004, John Wiley & Sons, Ltd. Waddell G: Biopsychosocial analysis of low back pain. In M Nordin, TL Vischer, eds: Common low back pain: prevention of chronicity. London, 1992, Bailliere Tindall. Waddell G, Burton AK: Occupational health guidelines for the management of low back pain at work: evidence review. Occup Med (2):124-135, 2001. Waddell G, McIntosh A, Hutchinson A, Feder G, Lewis M: The clinical guidelines for the management of acute low back pain. In Low back pain evidence review. London, December 2001, Royal College of General Practitioners. Weiser S, Cedraschi C: Psychosocial issues in the prevention of chronic low back pain: a literature review. In M Nordin, TL Vischer, eds: Common low back pain: prevention of chronicity. London, 1992, Bailliere Tindall. Work Loss Data Institute: Disorders of the neck and upper back. Occup Environ Med 60:618-626, 2003.
CHAPTER
Neck
3
CHAPTER
3a
A Review of the Epidemiology of Neck Pain in Workers: Prevalence, Incidence, and Risk Factors Pierre Côté, Linda Carroll, J. David Cassidy, Mana Rezai, Vicki Kristman, and the Scientific Secretariat of the 2000-2010 Bone and Joint Decade Task Force on Neck Pain and Its Associated Disorders*
In the past half century, the nature of work has rapidly changed. Once dependent mainly on manufacturing and resource extraction, the economy of industrialized countries increasingly relies on the service sector. This new reality has transformed the nature of work injuries and disability. The shift from manufacturing and resource-based jobs to the service industry led to a sharp reduction in acute and fatal injuries but contributed to the current epidemic of musculoskeletal disorders (MSDs).45 Today MSDs are the most burdensome ailments that affect the health and reduce the productivity of workers.56 Neck pain is one of the most prevalent MSDs in the workingage population48 and a leading source of disability and health care utilization among adults.18,19 During any 6-month period, 54% of adults suffer from neck pain and 4.6% experience significant activity limitations because of neck problems.18 Contrary to popular belief, most adults with neck pain do not experience complete permanent resolution of their discomfort; in fact, it follows an episodic course marked by periods of remission and exacerbation.20 Each year between 14.6% and 18.0% of adults develop a new episode of neck pain,20,21,48 which causes a new episode of disability in 600/100,000 adults annually.20 The etiology of neck pain in workers is complex and multifactorial. Its hypothesized risk factors include demographics, psychosocial and work-related issues, and poor general health.5,7,16,17,20 Although the etiologic contribution of work receives increasing attention, most studies remain cross-sectional and can be used only to hypothesize about the causes of neck pain.5,7 Understanding its etiology in workers is necessary to develop, test, and implement prevention strategies to reduce its burden.
PURPOSE The purpose of this chapter is to review and appraise the recent literature on the epidemiology of neck pain in workers. Specifically, we review the literature to answer the following questions: 1. What is the prevalence of neck pain in workers? We define prevalence as the proportion of workers with neck pain
*Eugene J. Carragee, Jaime Guzman, Scott Haldeman, Sheilah Hogg-Johnson, Lena Holm, Eric Hurwitz, Margareta Nordin, Paul M. Peloso, and Gabrielle van der Velde.
during a specific period of time; its measurement is useful to quantify the burden of a condition in a defined population. 2. What demographic, socioeconomic, health- and workrelated, psychosocial, and societal factors are associated with prevalent neck pain in workers? We refer to “associated factors” to describe variables that are correlated with neck pain in cross-sectional studies. Although these cannot be used to draw causal inferences about its etiology, they are useful to describe the potential risk factors for neck pain. 3. What is the incidence of neck pain in workers? We use the term incidence to describe the average risk of developing neck pain during a time period. A measure of incidence is not only useful to describe the proportion of the workers who will develop a new episode of neck pain during a specific time period but also necessary to quantify the etiologic contribution of risk factors. Incidence is measured from cohort studies. 4. What are the risk factors for neck pain in workers? Risk factors are things that may contribute to on help predict neck pain. We have collected information on risk factors—variables that increase or reduce risk—from case-control and cohort studies.
METHODS We wrote this chapter in collaboration with the members of the scientific secretariat of the 2000-2010 Bone and Joint Decade Task Force on Neck Pain and Its Associated Disorders. The Task Force includes a multidisciplinary scientific secretariat of 12 clinicians and methodologists representing rheumatology, orthopedic surgery, physical and rehabilitative medicine, neurology, physiotherapy, health psychology, chiropractic, epidemiology, clinical epidemiology, and biostatistics. A main objective was to complete a systematic search and critical review of the scientific literature on neck pain and its associated disorders. The literature reviewed in this chapter was critically appraised by members of the Task Force using a standardized critical appraisal methodology.
Definition of neck pain We define neck pain as soft tissue disorders of the cervical spine/shoulder area, including disk lesions and radiculopathy that are experienced by workers. Our definition does not assume a causal link between work and neck pain. It includes neck pain that is caused or aggravated by work, that which interferes with work, and symptomatic neck pain that does not result in disability.
Literature search Having developed our literature search strategy in collaboration with a library scientist (see Acknowledgments), we applied it to two electronic databases: MEDLINE and Embase ( January 1997 to October 2003). For the purpose of this chapter, we used a restricted portion of the exhaustive search undertaken by the Task Force. Our search was based on specific key words (neck pain, neck injury, pain, injury, epidemiology, incidence, prevalence,
26
Chapter 3a
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Prevalence, incidence, and risk factors of neck pain in workers
workplace, worker, work, meta-analysis) and text words (neck pain, cervical pain, neck ache, whiplash, pain, ache, sore, stiff, discomfort, neck, occupational, work-related, review, literature synthesis, literature review). All search terms were limited to the English and French languages and adult subjects. We excluded duplicate articles.
Article selection Each citation found in the search was screened by rotating groups of three Task Force scientific secretariat members to assess its relevance to the epidemiology of neck pain in workers. For the purpose of this review, articles were deemed relevant if they passed the following inclusion and exclusion criteria:
Inclusion criteria 1. Studies that report results relevant to neck pain in workers with or without its associated disorders, which might include radiating arm pain, upper thoracic pain, headache, and temporomandibular joint disorder pain; 2. Studies that examine the prevalence, incidence, risk, and/or prevention of neck pain with or without its associated disorders; 3. Studies of the risk or prevention of neck pain that include at least 20 human subjects at risk for neck pain with or without its associated disorders.
Exclusion criteria 1. Studies that do not include human subjects with neck pain with or without its associated disorders; 2. Studies of neck pain due to fracture, dislocation, tumor, skin lesions, throat disorders, inflammatory disorders, cervical myelopathy, and spinal cord injury; 3. Studies concerning radiating arm pain, upper thoracic pain, headaches, temporomandibular joint disorder, and thoracic outlet syndrome not associated with neck pain; 4. Opinion papers, letters to the editor, traditional narrative reviews, and papers without scientific data; 5. Single-case reports of workers with neck pain with or without its associated disorders; 6. Studies using cadavers or nonhuman subjects, such as crash test dummies, animals, or laboratory simulations; 7. Biomechanical studies without human subjects with neck pain.
to assist reviewers in understanding the impact of bias on the study results and to abstract information. Rotating pairs of scientific secretariat members independently conducted these in-depth reviews of each article, and the remaining members read the studies. The two reviewers presented their critical appraisal to a larger group of members for discussion of the scientific merit of the study. The members decided by consensus whether a study was scientifically admissible or inadmissible, the latter being one in which methodologic flaws were judged to have fatally biased the results and therefore made the paper’s conclusions scientifically invalid.
Data synthesis Each research question was answered by a best-evidence synthesis,52,53 which consists of assembling and qualitatively synthesizing the best evidence relevant to it. We described the strength of evidence for risk factors by adapting a methodology that has been used to rank studies on breast cancer, whiplash injuries, and mild traumatic brain injuries.4,13,19 The methodology distinguishes among three phases of studies. Phase I studies are hypothesis-generating investigations that descriptively explore associations between potential risk factors and disease outcomes. Phase II studies are extensive exploratory analyses that focus on particular sets of risk factors or attempt to discover which ones predict the development of neck pain. Phase III studies are large confirmatory studies of explicit prestated hypotheses that allow for focused examinations of the strength, direction, and independence of the proposed relationship between a risk factor and the development of neck pain. We present the prevalence and incidence of neck pain with 95% confidence intervals. Where these figures were not reported in the article but sufficient information was provided, we computed these estimates and report our computations. We describe the cross-sectional associations between various risk factors and neck pain as positive or negative. We report odds ratios, relative risks or hazard rate ratios, and 95% confidence intervals to describe associations between risk factors and neck pain obtained from case-control or cohort studies. When these estimates did not appear in the paper, they were computed from sufficient data. Confidence intervals for prevalence and incidence rates were calculated using the standard confidence interval formula around proportions described by Kuzma.37 All other analyses were performed using SAS.49
RESULTS
Critical review of the literature
Selection and critical appraisal of articles
All articles meeting the inclusion and exclusion criteria were critically reviewed using standard criteria and computerized critical review forms. Modified for the purpose of the 2000-2010 Task Force, the forms were similar to the ones used by the Quebec Task Force on Whiplash-Associated Disorders and the Best Evidence Synthesis on Traumatic Mild Injury (Appendix 3a.1).12,55 These criteria prompt the reviewers to appraise the methodologic merit of a study by focusing on selection bias, information bias, and confounding. Rather than provide a rating scale for determining scientific acceptability, the forms are used
The results from the literature search and selection of articles are summarized in Figure 3a.1. Overall, we retrieved 162 publications, including 152 articles from the literature search and 10 from our files. Of the 159 nonduplicate articles, 45 met the inclusion criteria and were reviewed. Fifteen articles were excluded by the scientific secretariat after they were appraised as scientifically inadmissible.10,11,15,26,31-34,36,40,41,43,61,63,64 Of the 30 accepted articles, 18 were cross-sectional studies that reported on the prevalence and factors associated with neck pain,1-3,22-25,28-30,39,42,44,46,47,58-60 and 10 reported on its incidence
Chapter 3a
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Results
1. Literature search Medline
Embase
Personal files
109
43
10
Librarian
162 articles
159 non-duplicate articles
2. Screening Scientific secretariat Inclusion criteria
114 irrelevant 45 relevant articles
3. Review Scientific Critical appraisal secretariat
15 rejected
30 articles accepted and reviewed Figure 3a.1
Results of literature search and selection of articles included in the review.
and risk factors.6,8,27,35,38,50,51,54,57,62 Two studies reported crosssectional and prospective results.9,14
Neck pain in general working populations Prevalence We accepted four cross-sectional studies that described the prevalence of neck pain in samples of workers from the general population, in this case in Europe.9,14,23,46 The source population for these studies varied from registers of general practitioners in the United Kingdom to age cohorts of workers under the supervision of occupational physicians in France, workers who participated in periodical health surveys in the Netherlands, and 34-year old workers in Sweden. Overall, these studies suggest that neck pain is highly prevalent and a common source of activity limitations. In the United Kingdom, 34% of workers reported that they experienced neck pain in the preceding year (Table 3a.1).46 During the same period, 11% of workers limited their activities because of neck pain. Overall, 20% of surveyed workers had experienced neck pain in the preceding week. In Sweden, the 1-year prevalence of neck pain was 44% and 61% in 34-year-old men and women, respectively (Table 3a.1).9 In this cohort, 26% of men and 43% of women reported symptoms that lasted more than 1 month. In France during 1990, the prevalence of chronic neck/shoulder pain lasting for at least 6 months and associated with functional limitations was 7.8% in men and 14.8% in women (Table 3a.1).14 In 1995 this same study reported that the prevalence of chronic neck/shoulder pain had increased slightly to 9.5% in men and 17.6% in women.
Factors associated with neck pain All four studies reported that the prevalence of neck pain increases with age and is more common in women (Table 3a.1).9,14,23,46 In Sweden, self-employed males had a higher prevalence of neck/shoulder symptoms in the past month than other workers.9 In the United Kingdom, workers with musculoskeletal comorbidities were more likely to report neck pain. Palmer et al46 reported that the prevalence of neck pain in the preceding week was higher in those with shoulder, elbow, wrist-hand, hip, and knee pain. Similarly, neck pain was more common in workers who had experienced troublesome low back pain in the preceding year and in those who suffered from frequent headaches, fatigue, or stress.9,46 Barnekow-Bergkvist et al9 found that workers with better flexibility of the cervical spine (rotation) reported fewer neck/shoulder symptoms in the preceding month. Three studies reported that ergonomic, physical, and psychosocial factors at work are associated with neck pain (Table 3a.1). Two studies reported on its association with lifting. In Sweden, the prevalence of neck symptoms in the preceding month was lower in workers who performed repetitive or heavy lifting,9 whereas in contrast, Palmer et al46 reported that lifting increased it. Among U.K. workers, the prevalence of neck pain was found to be higher also in workers who reached overhead for more than 1 hour per day and in those exposed to hand and arm vibration.46 Using a keyboard for 4 hours or more in an average working day was positively associated with neck pain in women but not in men.47 A positive association between monotonous work, high decision latitude, and prevalent neck/shoulder symptoms was found among female workers in the Swedish sample.9 Finally, Dutch adult workers who reported a combination of mentally and physically demanding work and those performing heavily
27
Swedish student aged 16 years in 1974
Workers under the supervision of occupational physicians from France in 1990 and 1995
Registers of 163 general practitioners in 34 general practices in England, Scotland, and Wales and members of the British armed services in 1997-1998
Dutch workers who participated in the periodical occupational health surveys between 1982 and 1993
Cassou et al, 200214
Palmer et al, 200146
De Zwart et al, 199723
(−), negative association; (+), positive association; CI, confidence interval.
Inclusion: active workers aged 16-64 years Sample size = 44,486
Regular pain or stiffness in the neck
Not applicable
1-year prevalence: Men: 44% (36-52) Women: 61% (51-71) Prevalence of symptoms > 1/month: Men: 26% (19-33) Women: 43% (33-54) Point prevalence: Men: 1990: 7.8% (7.3-8.3) 1995: 9.5% (8.9-10.1) Women: 1990: 14.8% (14.0-15.6) 1995: 17.6% (16.7-18.5) 1-year prevalence: 34% (33-35) 1-year prevalence of neck pain interfering with normal activities: 11% (10-12) 1-week prevalence: 20% (19-21)
Men: Age (+); shoulder pain (+); elbow pain (+); wrist-hand pain (+); hip pain (+); knee pain (+); low back pain (+); headaches (+); tiredness/ stress (+); working overhead (+); heavy lifting (+); use of keyboard for > 4 hours/day (−); hand-arm vibration (+) Women: Age (+); shoulder pain (+); elbow pain (+); wrist-hand pain (+); hip pain (+); knee pain (+); low back pain (+); headaches (+); tiredness/stress (+); working overhead (+); use of keyboard for > 4 hours/day (−); heavy lifting (+); hand-arm vibration (+) Prevalence varies with occupation Prevalence is higher in women than men Men: Age (+); mentally and physically demanding work (+); heavy physically demanding work (+) Women: Age (+); mentally and physically demanding work (+); heavy physically demanding work (+)
Men: Lifting (−); self-employed (+); worrying (+); neck lateral rotation (−) Women: Monotonous work posture (+); lifting (−); high decision latitude (+); hand grip performance (−); neck lateral rotation (−) Age (+); women (+)
●
Chronic neck pain: self-report of neck/ shoulder pain lasting at least 6 months with functional limitations confirmed by clinical examination Neck pain measured with Standardized Nordic Questionnaire
Neck-shoulder pain measured with Standardized Nordic Questionnaire
Associated factors (95% CI)
Chapter 3a
Inclusion: workers born in 1938, 1943, 1948, or 1953 who underwent an annual medical examination Exclusion: Individuals not employed in 1995 Sample size = 16,950 Inclusion: individuals aged 16-64 years Sample size = 12,907
Inclusion: 34-year-old subjects in 1992 who worked at least 16 hours/week at time of survey Exclusion: maternity/paternity leave, students, long-term sick leave Sample size = 238
Prevalence (95% CI)
BarnekowBergkvist et al, 19989
Case definitions
Source population
Study
Inclusion/exclusion criteria
Studies of prevalence and factors associated with neck pain in workers
Table 3a.1
28 Prevalence, incidence, and risk factors of neck pain in workers
Chapter 3a
demanding work were more likely to report regular pain or stiffness in the neck.23
Incidence Three cohort studies, two conducted in France and one in the United States, provided information about the incidence of neck pain in samples of workers from the general population. The studied populations included workers under supervision of French occupational physicians/medical departments in the early 1990s14 and those covered by the Washington State Department of Labor and Industries state fund (including employees of selfinsured employers) between 1990 and 1998.51 These studies suggested that a significant proportion of the working population experiences a new episode of neck pain each year. These cohort studies offered insights about the “high-risk” groups for the development of an episode of neck pain. In France the 6-month incidence of neck pain among workers with no prior history was 17.4%, whereas it was 44.4% in those who reported a past history of neck disorders.38 Between 1990 and 1995, 12.5% female French workers and 7.3% of male French workers developed chronic neck pain (Table 3a.2).14 In Washington State, 40.1 per 10,000 full-time equivalent workers covered by the state fund developed neck pain.51 However, the reported incidence was only 5.1 per 10,000 full-time equivalent employees in self-insured firms.
Risk factors for neck pain Four phase II studies reported on factors associated with the development of neck pain in general working populations. Three Swedish studies described risk factors for developing neck pain in the past year, and one French study reported on the risk factors for chronic neck pain. In a Swedish cohort of 16-year-old student-workers, bench press performance was negatively associated with the development of neck/shoulder pain 18 years later (Table 3a.2).9 In other words, workers who performed better while bench pressing when 16 years of age in 1974 were protected against developing neck/shoulder pain in 1992. In another study, Fredriksson et al27 found that the development of neck/shoulder pain was associated with physical and psychosocial factors at work, specifically high physical work load for men and frequent hand movement for women. The authors found, moreover, that physical and psychosocial risk factors frequently interact and modify their effects on the incidence of neck/shoulder pain in workers. A third Swedish study found that both physical and psychosocial risk factors contribute to workers seeking health care for neck/shoulder pain.57 A previous episode of neck pain that persisted for more than 3 months and a nonfixed salary strongly predicted seeking health care for this symptom. The risk factors as well as the strength and the direction of association varied between men and women, suggesting that the etiology has a gender-specific component.57 For men, exposure to psychosocial factors such as high job demands or high time pressure reduced the risk of seeking care (Table 3a.2). In women, however, exposure to other psychosocial risk factors such as high degree of hindrance with work increased the risk of seeking care for neck/shoulder pain. Tornqvist et al57 also reported that workers with multiple risk factors were more likely to seek care. In France, the risk of developing chronic neck pain and disability was associated with sociodemographic variables, workplace
●
Results
psychosocial factors, comorbidities, and health risk behaviors (Table 3a.2). In their large cohort, Cassou et al14 found that increasing age, repetitive work, and high job demands were associated with chronic neck pain. Moreover, workers with depressive symptoms and those suffering from MSDs in the preceding year were more likely to develop chronic neck pain.
Neck pain in specific occupational groups Prevalence Twelve cross-sectional studies described the prevalence and factors associated with neck pain in samples of health care workers, including dental personnel, physical therapists and nurses,1-3,22,24,39,58-60 music and nursery school teachers,25,44 and blue collar workers (sewage workers, spinning industry, forestry, and scaffolding).28-30,42 The available evidence suggests that the prevalence of neck pain varies across occupations and tends to be higher for health care workers (Table 3a.3). Among these workers, the 1-year prevalence of neck pain varies from 45.8% in nurses to 47.6% in physical therapists, 64% in dentists, and 72% in dental hygienists (Table 3a.3).1,2,22,39,58-60 In Sweden, it is estimated that 50% of dental hygienists experience neck pain in the preceding week, whereas in Norway, 22.6% of nursing aides report that they experienced intense neck pain in the preceding 2 weeks.2,24 The prevalence of chronic neck pain is 9% among the nursing staff of Greek hospitals.3 In Sweden, most music teachers (59%) experience neck pain every year, and 30% experience an episode each week.25 Similarly, one fourth to one third of Japanese nursery school teachers report neck pain each month.44 Interestingly, except for sewage workers the prevalence of neck pain is lower in industrial, forestry, and construction workers than in health care workers or teachers. In Austrian sewage workers, the annual prevalence of neck pain is 52.4%, and 20.9% of workers suffer from neck pain each day.28
Factors associated with neck pain In health care workers, the presence of neck pain was associated with demographic, ergonomic, and workplace factors. Among nurses, neck pain was more common in older workers and in those with moderate/high physical or psychologic demands.39,58-60 Nurses and nursing aides who worked long hours reported neck pain more frequently.24,39,58-60 Although neck pain was more common in those who worked under strenuous back postures, it was less so in those who used mechanical lifts or received ergonomic training.3,24,39,58-60 In physical therapists, neck pain was positively associated with the pace of work and the type of practice.22 The association between neck pain and physical/psychologic variables was observed also in Japanese nursery school teachers, among whom it was more common in those with poor supervisor support and in those caring for young children.44 Similarly, male Swedish music teachers with low social support and women teachers with high psychologic demands were more likely to report neck pain.25 Neck pain in blue collar workers was associated with age, physical work, and psychologic demands.28,30
Incidence of neck pain Five cohort studies describe the incidence of neck pain in specific occupational groups, including industrial/service companies,6,8
29
Inclusion: individuals living in Sweden in 1993, without a diagnosis of MSD in 1969 and below age 59 in 1993 Sample size = 484
Individuals from Stockholm, Sweden who participated in the REBUS-69 study in 1969
Fredriksson et al, 200027 Nested casecontrol study Phase II
Cases: neck/shoulder Not applicable pain defined by a questionnaire reporting consultation with a physician, physiotherapist, chiropractor, osteopath, or other medical professional or sick leave for more than 7 consecutive days between 1970 and 1992 Neck/shoulder pain defined as pain lasting at least 7 consecutive days during the last year Controls: Individual matched on age, gender, and index year
5-year incidence: Men: 7.3% (6.8, 7.8) Women: 12.5% (11.7, 13.3)
Incidence (95% CI)
Men: Year of birth 1938 vs. 1953 OR = 2.0 (1.6, 2.6); year of birth 1945 vs. 1953 OR = 1.5 (1.2, 1.9); repetitive work before 1990 OR = 1.3 (1.0, 1.7); awkward work OR = 1.3 (1.1, 1.7); high job demand OR = 1.2 (1.0, 1.4); depressive symptoms OR = 1.3 (1.0, 1.8); MSD in past year OR = 1.5 (1.3, 1.8); sporting activities OR = 0.8 (0.7, 0.9); smoking OR = 1.2 (1.0, 1.4) Women: Year of birth 1938 vs. 1953 OR = 1.5 (1.2, 2.0); year of birth 1945 vs. 1953 OR = 1.6 (1.3, 2.0); year of birth 1948 vs. 1953 OR = 1.2 (1.0, 1.5); repetitive work in 1990 OR = 1.3 (1.0, 1.6); repetitive work before 1990 OR = 1.2 (1.0, 1.5); high job demand OR = 1.2 (1.0, 1.4); depressive symptoms OR = 1.5 (1.2, 1.9); MSD in past year OR = 1.7 (1.5, 2.0) Risk factors in the past 5 years. Men: High physical workload index OR = 2.2 (1.1, 4.6); frequent hand/finger work during leisure time OR = 2.1 (1.0, 4.5) Significant interactions: Work with vibrating tools and frequent hand movements; frequent hand work during leisure time and high perceived workload; frequent hand work during leisure time and work with vibrating tools; precision work during leisure time and high physical workload Women: Frequent hand movements at work OR = 1.5 (1.0, 2.3) Significant interactions: High perceived workload and low influence over work condition; high perceived workload outside work and low influence over work conditions; frequent hand work during leisure time and high perceived workload; frequent hand work during leisure time and high physical workload; precision work during leisure time and few possibilities of development; precision work during leisure time and low influence over work conditions
Men: Bench press performance at 16 years old (OR = 0.30 (0.09-0.85))
Risk factors (95% CI)
●
Chronic neck pain: self-report of neck/ shoulder pain lasting at least 6 months with functional limitations confirmed by clinical examination
Neck-shoulder pain measured with Standardized Nordic Questionnaire
Case definitions
Chapter 3a
Cassou et al, 200214 Cohort study Phase II
16-year-old Inclusion: 34-year-old subjects in Swedish student- 1992 who worked at least workers in 1974 16 hours/week at time of survey Exclusion: maternity/paternity leave, students, long-term sick leave Sample size = 238 Workers under Inclusion: workers born in 1938, 1943, the supervision 1948, or 1953 who underwent of occupational an annual medical examination physicians from Exclusion: individuals not employed France in 1990 in 1995 and 1995 Sample size = 16,950
BarnekowBergkvist et al, 19989 Phase II
Inclusion/exclusion criteria
Studies of incidence and risk factors associated with neck pain in workers
Study, design, Source and phase population
Table 3a.2
30 Prevalence, incidence, and risk factors of neck pain in workers
Workers covered by the Washington State Department of Labor and Industries State Fund and employees of self-insured employers between 1990 and 1998 Workers in the municipality of Norrtälje, Sweden from Sept 1, 1994 to June 30, 1997
Silverstein et al, 200251 Cohort study
Inclusion: workers aged 20-59 years who worked more than 17 hours/ week and had worked at least 2 months during the past year Exclusion: seeking health care for neck, shoulder, or low back disorders during the 6 months before enrollment Sample size = 1903
Inclusion: accepted State Fund claims for specific diagnostic or treatment codes. Of the self-insured claims, only those with more than 3 days of lost time were included. Sample size = 392,925
Inclusion: at least 1 year of employment Exclusion: workers with sick leave for more than 3 months in the previous year, pregnancy, temporary work contract, or retirement within the following 12 months Sample size = 511
Men: Suffered from neck or shoulder symptoms > 3 months earlier in life: RR = 4.4 (2.7-7.1); work with vibrating tools: RR = 1.6 (1.0-2.3); nonfixed salary RR = 1.9 (1.1-3.1); high demands RR = 0.7 (0.4-1.0); high time pressure RR = 0.5 (0.3-1.0); high creativity/low routine work profile RR = 0.6 (0.4-1.0); high quantitative demands RR = 0.2 (0.1-0.9); low demands in relation to competence RR = 1.5 (1.0-2.4) Women: Suffered from neck or shoulder symptoms > 3 months earlier in life: RR = 4.1 (3.0-5.7); repetitive hand/finger movements RR = 1.6 (1.2-2.2); nonfixed salary RR = 2.0 (1.0-4.2); nightshift/shift work including night work RR = 1.3 (1.0-1.8); long working hours RR = 0.7 (0.5-0.9); solitary work RR = 1.8 (1.2-2.9); job strain RR = 1.4 (1.1-2.0); high degree of hindrances at work RR = 1.4 (1.0-1.9)
Among 311 workers Not applicable without prior neck pain: 6-month incidence: 17.4% (13.3-22.0) 6-month incidence of disorders that lasted > 30 days: 1.3% (0.0-3.3) Among 27 workers with a prior history neck pain: 6-month incidence: 44.4% (25.5-64.7) 6-month incidence of disorders that lasted > 30 days: 11.1% (2.4-29.2) Cumulative incidence Not applicable (per 10,000 FTE): State fund: 40.1 (39.6, 40.6) Self-insured employers: 5.1 (4.9, 5.3)
Cases were those who Not applicable sought treatment for neck-shoulder disorders Controls were randomly from the population register Control group = 1511
Accepted claims for nontraumatic neck soft tissue disorders with the neck as the primary site of injury
Neck disorder (ache, pain, discomfort) in the past 6 months defined by questionnaire and body diagram Neck disorder for more than 30 days
●
CI, confidence interval; MSD, musculoskeletal disorder; OR, odds ration; RR, relative risk.
Tornqvist et al, 200157 Case-control study Phase II
Hospital, warehouse, office, and airport workers recruited from medical departments in France in 1991
Leclerc et al, 199938 Cohort study
Chapter 3a Results 31
Source population
Dental personnel (dentists, dental hygienists, and dental assistants) from the public health services in the county of Blekinge, Sweden
Nursing staff from six hospitals in Athens, Greece between 2000 and 2001
Physical therapists registered in the state of Victoria, Australia
Norwegian nurse’s aides in 1999
˚Akesson et al, 19991 ˚Akesson et al, 20002
Alexopoulos et al, 20033
Cromie et al, 200022
Eriksen, 200324
Neck pain measured with the Standardized Nordic Questionnaire Chronic neck pain is pain lasting > 3 months Neck pain measured with the Standardized Nordic Questionnaire
Neck pain measured with the Standardized Nordic Questionnaire
Case definitions
Inclusion: vocationally active Neck pain measured Exclusion: sick leave because with the Standardized of illness or pregnancy Nordic Questionnaire Sample size = 6485
Exclusion: therapists not living in Australia Sample size = 536
Inclusion: at least one year of experience in current job Sample size = 351
Exclusion: personnel on leave (other than sick leave) and specialist dentists Sample size = 244
Inclusion/exclusion criteria
2-week prevalence: Any pain: 53.5 % (52.3-54.7) Intense pain: 22.6% (21.6-23.6)
1-year prevalence: 47.6% (43.3-51.8)
1-week prevalence: Hygienists: 50% (33, 67); male dentists: 31% (16, 45); female dentists: 27% (12, 42); general practice dental assistants: 17% (10, 24); specialist dental assistants: 16% (4, 27) 1-year prevalence: Hygienists: 72% (56, 87); male dentists: 64% (49, 79); female dentists: 64% (47, 80); general practice dental assistants: 46% (37, 55); specialist dental assistants: 34% (19, 49) Prevalence at 5-year follow-up for females. 1-week prevalence: Hygienists: 41%; dentists: 38%; dental assistants 31% 1-year prevalence: Hygienists: 73%; dentists: 54%; dental assistants 62% 1-year prevalence: 47% (42-52) Prevalence of chronic neck pain: 9% (6-12) Prevalence of sick leave: 5% (3-7)
Prevalence (95% CI)
Male (+), private practice (+), sports physical therapy (+), manual techniques (+), sedentary work (+), repetitive tasks (+), large number of patients/day (+), few rest periods (+), rest periods (+), work when injured (+), mobilization/manipulation (+), other manual treatment (+) Female (+), marital status/single (+), working >36 hours/week (+), working in old people’s home (+)
Strenuous back posture (+); moderate/bad perceived general health (+)
Not applicable
Associated factors (95% CI)
●
Study
Studies of prevalence and factors associated with neck pain in specific occupations
Chapter 3a
Table 3a.3
32 Prevalence, incidence, and risk factors of neck pain in workers
Molano Workers from a scaffolding company in the et al, 200142 Netherlands from June to September, 1998 Ono et al, Nursery school teachers in a Japanese city, 200244 in October, 1995
Workers from the spinning industry in Lithuania in 1996 Forestry workers from Norway
Exclusion: male workers, nurses, supervisors Sample size = 959
Inclusion: job involving heavy lifting or working while bent over Sample size = 255 Inclusion: production workers Sample size = 363 Inclusion: manual workers, machine operators, and administrative workers who worked for at least 10 months/year during the previous 5 years Sample size = 835 Inclusion: all workers Sample size = 323
Friedrich Sewage workers from Vienna, Austria et al, 200028
Gamperiene and Stigum, 199929 Hagen et al, 199830
Inclusion: all music teachers Sample size = 208
FjellmanMusic teachers in two Wiklund counties of Sweden in 2000 et al, 200325
1-year prevalence: 27% (22, 32)
1-year prevalence: 27.7% (21.9, 33.5)
1-year prevalence: Cumulative: 59% (52-66) Men: 52% (43-61) Women: 67% (57-77) 1-week prevalence: Cumulative: 30% (24-36) Men: 26% (18-34) Women: 36% (26-46) Lifetime prevalence: 67.5% (61.6-73.3) 1-year prevalence: 52.4% (46.0-58.5) 1-week prevalence: 25.7% (20.3-31.3) Point prevalence: 20.9 (15.8-26.0) 1-year prevalence: 16.5% (12.4, 20.8)
Neck/shoulder pain in Not applicable the previous month greater than grade 3/5 on a self-reported scale
Neck pain measured with the Standardized Nordic Questionnaire
Neck pain measured with the Standardized Nordic Questionnaire Neck/shoulder pain for at least 30 days in previous 1 year measured with the Standardized Nordic Questionnaire
Neck pain measured with the Standardized Nordic Questionnaire
Neck pain measured with the Standardized Nordic Questionnaire
Continued
10 years of experience (+); caring for children aged 0 (+); holding/lifting a child/material exceeding 20 kg (+); poor supervisor support (+)
Not applicable
Age (+); physical work (+); low intellectual discretion (+); high psychologic demands (+)
Not applicable
Age (+)
Men: Low social support (+); lifting (+); playing guitar (+) Women: High psychologic demands (+); teaching at 5-12 schools/week (+)
Chapter 3a ●
Results 33
Registers of 163 general practitioners in 34 general practices across Britain in 1997-1998
Palmer et al, 200146
Inclusion: at current job for at least 1 year Exclusion: nurses with non-work related injuries within a 3-month period before onset of workrelated neck pain Sample size = 1163
Inclusion: workers aged 16-64 years employed in nonmanual occupations Exclusion: manual occupations Sample size = 4889
Inclusion/exclusion criteria
(−), negative association; (+), positive association; CI, confidence interval.
Trinkoff et al, Licensed registered nurses from Illinois and 200259 Lipscomb New York state in 1999-2000 et al, 200239 Trinkoff et al, 200358 Trinkoff et al, 200360
Source population
Study
Neck pain measured with the Standardized Nordic Questionnaire Case: neck pain lasting ≥ 1 week and ≥ 3/5 in intensity Symptoms: neck pain without full definition of a case
Neck pain measured with Standardized Nordic Questionnaire
Case definitions 1-week prevalence: Men: Keyboard: 14.8% (12.3-17.4) No keyboard: 13.8% (12.0-15.6) Women: Keyboard: 22.9% (20.3-25.4) No keyboard: 18.3% (16.3-20.3) 1-week prevalence of disability among workers with neck pain: Men: Keyboard: 26% (18-34) No keyboard: 33% (26-39) Women: Keyboard: 33% (27-39) No keyboard: 37% (31-42) 1-year prevalence: Cumulative: 45.8% (43.0-48.7) Case: 20.4% (18.1-22.8) Symptoms: 25.4% (22.9-27.9)
Prevalence (95% CI)
Age (+); mechanical lifting devices (−); training on adjustment of work station (−); training on recognizing workplace hazards (−); working long hours (+); moderate and high physical demands (+); psychologic demands; dependents (+); working long hours (+)
Not applicable
Associated factors (95% CI)
●
Studies of prevalence and factors associated with neck pain in specific occupations—cont’d
Chapter 3a
Table 3a.3
34 Prevalence, incidence, and risk factors of neck pain in workers
Chapter 3a
municipal office workers,35 teaching hospital employees,50 female nurses from acute care hospitals,54 and workers from a large forestry industry.62 Overall, the evidence suggests that the incidence of neck pain varies across occupational group, tending to be higher for those working in hospitals and offices (Table 3a.4). In England, female nurses working in acute care hospital settings developed neck pain at a rate of 17% per year.54 In Canada, 40.5% of employees at a teaching hospital who were asymptomatic in 1996 reported to have experienced an episode of neck pain in the preceding week when followed up a year later.50 In Finnish municipal office workers, the annual incidence of neck pain with or without radiations was 34.4%. Approximately 13% had local neck pain only, and 14.4% had radiating pain without neck pain. The annual incidence of workers reporting both local and radiating neck pain was 6.7%.35 The incidence of neck pain was lower among workers in industrial/service and forestry sectors. In workers from 34 industrial/service companies located throughout the Netherlands, the 3-year incidence of neck pain was 14.4%.6,8 The overall 3-year incidence among Finnish forestry workers was a similar 15.6%62: 9.2% developed mild neck pain, and 6.4% developed severe pain.
●
Relevance
neck pain; specifically, we found its incidence to be higher for nurses and office workers.35,50,51 Studies that quantified the role of risk factors supported that neck pain is more common in workers with high quantitative job demands, low coworker support, repetitive work, nonfixed salary, increased sitting time, poor ergonomics, previous musculoskeletal pain, and depressive symptoms.5,8,14,27,35,54,57 Although we identified several risk factors for neck pain, it is important to note that only one phase III study was designed specifically to test their independence.5,8 This finding indicates that very few risk factors can be considered well established. Efforts should be devoted to designing phase III studies to confirm the results of cross-sectional observations and phase II (exploratory) studies. Moreover, future studies should pay attention to interactions among individual, psychosocial, and workplace risk factors. The growing body of evidence supporting the role of psychosocial and workplace factors in the etiology of neck pain must not be considered in isolation. Because it is very likely that the risk factors for the development of neck pain and disability vary across occupations, as demonstrated in our review, future studies should ensure that the risk profiles of various occupations are explored.
Risk factors for neck pain Two phase II and one phase I study examined the risk factors for neck pain in specific occupational groups (Table 3a.4). Among Finnish municipal workers, females and those with poor keyboard position were more likely to develop neck pain.35 In English female nurses, a new episode of neck pain was associated with previous neck and low back pain and with various physical aspects of care such as moving and transferring patients.54 Only one phase III study supported the observation that physical and psychosocial factors contribute to the development of neck pain.5,8 In their cohort study of industrial and service workers from the Netherlands, Ariens et al5,8 demonstrated that high quantitative job demands, low coworker support, and prolonged sitting are independent risk factors for a new episode of neck pain.
SUMMARY Neck pain is endemic in workers. Our best evidence synthesis demonstrates that it is highly prevalent and a common source of disability. By far, most neck pain in workers is nontraumatic. Its etiology is consequently multifaceted, and although occupational factors may be important contributors to its development, they are neither sufficient nor necessary. This reality clearly emphasizes that the development of an episode of neck pain cannot be attributed entirely to the physical and psychosocial environment of a workplace. Our review of cross-sectional studies supports the view that neck pain is more common in various subgroups of workers. It is more prevalent among older workers, women, and those with musculoskeletal comorbidities.1,2,14,23,24,28,30,39,46,54,57-60 Moreover, it varies significantly across occupations and is associated with ergonomic, physical, and psychosocial factors.3,5,8,9,14,22,23,25,27,30,35,39,44,46,54,57-60 Evidence from case-control and cohort studies confirms that certain occupations pose higher risk of developing an episode of
RELEVANCE Our review has important implications for prevention. First, intervention must target clearly modifiable risk factors. Second, the multifaceted etiology of neck pain highlights the importance of designing preventive interventions focused on multiple rather than individual risk factors. Current research has not yet identified the “necessary” causes for neck pain and disability, and very little is known about the interrelationships among risk factors. Multimodal interventions targeting multiple modifiable risks such as workplace and psychosocial factors may thus prove more promising than one-dimensional approaches targeting a specific one. Finally, the complex etiology of neck pain suggests that the roles of economic and legal factors, work organization, and health care access and delivery are important and must be studied as well.14
ACKNOWLEDGMENTS We are indebted to Emma Irvin and Stephen Greenhalgh, research librarians, for their expertise and guidance with the literature search. The Bone and Joint Decade Task Force on Neck Pain and Its Associated Disorders is supported by a grant to the University of Alberta from the National Chiropractic Mutual Insurance Company and the Canadian Chiropractic Protective Association, Jalan Pacific Inc., Länsförsäkringar Wasa, and the Insurance Bureau of Canada. This article was made possible also through the financial support of the Workplace Safety and Insurance Board of Ontario. Dr. Côté is supported by the Canadian Institutes of Health Research through a New Investigator Award and by the Institute for Work & Health by the Workplace Safety and Insurance Board of Ontario. Dr. Carroll is supported by a Health Scholar Award from the Alberta Heritage Foundation for Medical Research. Dr. Cassidy is supported by an endowed research chair from the University Health Network. Vicki Kristman is supported by a Doctoral Training Award from the Canadian Institutes of Health Research in partnership with the
35
Shannon Employees of a teaching hospital in Hamilton, et al, 200150 Cohort study Ontario, Canada from 1995 to 1997
Korhonen Finnish municipal office workers in et al, 200335 Cohort study 1998-1999 Phase II
Inclusion: workers who worked Neck pain measured by a modified at least 20 hours per week Standardized Nordic Questionnaire and worked at their current Cases were defined as regular or job for at least 1 year prolonged neck pain, with episodes that Exclusion: workers who had another lasted for at least 1 day during the paid job for any substantial previous 12 months on at least amount of time, received a work one of 3 follow-up measurements disability payment for neck pain in the preceding year, and had prolonged neck pain during the year before baseline Sample size = 977 Inclusion: full-time Incident cases were healthy subjects at employees working on baseline (those who reported local or video display units for radiating neck pain for less than 8 days more than 4 hours/week during the preceding 12 months) who Sample size = 180 reported at follow-up local or radiating neck pain for at least 8 days during the preceding 12 months. Question for local neck pain was: “Estimate the total number of days you have had local neck pain (not radiation) during the preceding 12 months: 0 days, 1-7 days, 8-30 days, >30 days but not daily, and daily.” Healthy was defined as 0-7 days, and 8 or more days defined incident neck pain. Inclusion: workers still Neck pain measured by question: “In the employed by the hospital past week, how often have you suffered at the end of the study from neck and/or shoulder pain?” Exclusion: physicians Sample size = 173
High quantitative job demands RR = 2.14 (1.28, 3.58); low coworker support RR = 2.43 (1.11, 5.29); sitting > 95% of the time RR = 2.34 (1.05-5.21)
Incidence of an episode of neck pain in the previous week: 40.5% (33.1, 47.8)
Not applicable
1-year incidence: Female OR = 2.9 (1.3-2.7); poor keyboard Local or radiating neck position OR = 2.1 (1.0-4.5) pain: 34.4% (12.5-41.3) Local and radiating neck pain: 6.7% (3.0-10.3)
1-year incidence: 5.7% (4.3, 7.2) 3-year incidence: 14.4% (12.2, 16.6)
Incidence (95% CI) Risk Factors (95% CI)
Workers from 34 industrial/service companies located throughout the Netherlands from 1994 to 1997
Case definitions
Ariens et al, 20018 Ariens et al, 20015 Cohort study Phase III
Inclusion/exclusion criteria
Source population
Study
●
Studies of incidence and risk factors associated with neck pain in specific occupations
Chapter 3a
Table 3a.4
36 Prevalence, incidence, and risk factors of neck pain in workers
Exclusion: workers with rheumatoid arthritis and part-time workers Sample size = 5180
Viikari-Juntura Workers from a large forest industry et al, 200162 Cohort study enterprise in Finland Phase II from 1992 to 1995
CI, confidence interval; HR, hazard ratio; OR, odds ratio; RR, relative risk.
Inclusion: working at same job throughout the study Exclusion: agency staff, student nurses, and community nurses Sample size = 587
Smedley Female nurses from two acute et al, 200354 Cohort study hospitals in the Phase II south of England
Radiating neck pain measured by a modified version of the Standardized Nordic Questionnaire Mild pain: 8-30 days in previous year Severe pain: >20 days in previous year
Neck pain measured with the Standardized Nordic Questionnaire
Cumulative 3-year incidence: Mild pain: 9.2% (7.9, 10.5) Severe pain: 6.4% (5.3, 7.5)
2-year incidence of neck pain: 34% (30-38)
Previous neck pain: > 1 year before baseline HR = 1.6 (1.1-2.3); < 1 year before baseline HR = 2.8 (2.0-3.9) Duration of previous neck pain: < 1 week HR = 1.7 (1.1-2.5); 1-4 weeks HR = 2.3 (1.5-3.3); > 4 weeks HR = 2.6 (1.7-4.0) Previous low back pain: >1 year before baseline HR = 1.8 (1.2-2.7); < 1 year before baseline HR = 1.9 (1.4-2.7). Duration of previous low back pain: 1-4 weeks HR = 1.8 (1.2-2.7); > 4 weeks HR = 2.3 (1.6-3.3) Assisting patients to mobilize > 4 times/shift HR = 1.6 (1.1-2.3); moving patients around > 4 times/shift HR = 1.6 (1.1-2.4); transferring patients in/out bath HR = 1.4 (1.0-2.0); washing or dressing patients while on chair > 4 times/shift HR = 1.7 (1.1-2.8); washing or dressing patients while on bed > 4 times/shift HR = 1.6 (1.0-2.5) Not applicable
Chapter 3a ●
Relevance 37
38
Chapter 3a
●
Prevalence, incidence, and risk factors of neck pain in workers
Canadian Institute for the Relief of Pain and Disability (formally known as the Physical Medicine Research Foundation) Woodbridge Grants and Awards Program and by the Institute for Work & Health by the Workplace Safety and Insurance Board of Ontario.
25.
26.
27.
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Slavin RE: Best evidence synthesis: an intelligent alternative to meta-analysis. J Clin Epidemiol 48(1):9-18, 1995. Smedley J, Inskip H, Trevelyan F, Buckle P, Cooper C, Coggon D: Risk factors for incident neck and shoulder pain in hospital nurses. Occup Environ Med 60(11):864-869, 2003. Spitzer WO, Skovron ML, Salmi LR, et al: Scientific monograph of the Quebec Task Force on Whiplash-Associated Disorders: redefining “whiplash” and its management [see comment]. [Erratum appears in Spine 20(21):2372, 1995.] Spine (8 Suppl): 1S-73S, 1990. Stewart WF, Ricci JA, Chee E, Morganstein D, Lipton R: Lost productive time and cost due to common pain conditions in the US workforce [see comment]. JAMA 290(18):2443-2454, 2003. Tornqvist EW, Kilbom A, Vingard E, et al: The influence on seeking care because of neck and shoulder disorders from work-related exposures. Epidemiology 12(5):537-545, 2001. Trinkoff AM, Brady B, Nielsen K: Workplace prevention and musculoskeletal injuries in nurses. J Nurs Admin 33(3):153-158, 2003.
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39
Appendix 3a.1
GENERAL METHODOLOGIC ISSUES USED FOR ALL STUDY DESIGN 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Research question is clearly stated Source and target population identified and described Inclusion criteria described and appropriate Exclusion criteria described and appropriate Number of excluded or refusals (before study) reported Withdrawals (during study) reported, explained, and reasonable Withdrawals equal in groups Statistical analyses appropriate Adjustment for important variables measured at entry into study Results verifiable from raw data
CRITERIA FOR THE APPRAISAL OF THE METHODOLOGIC QUALITY OF CROSS-SECTIONAL STUDIES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Similar sampling procedures for all subjects Similar ascertainment of exposure for all subjects Similar referral and diagnostic procedures for all subjects Diagnostic criteria for disease (clear, reliable, and valid) Characteristics of subjects at enrollment reported All aspects of exposure measured (level, dose, duration, etc.) Coexposures measured Recall bias controlled Data collection valid and reliable Selection bias considered Analyses controls for confounding factor
CRITERIA FOR THE APPRAISAL OF THE METHODOLOGIC QUALITY OF COHORT STUDIES 1. Zero time identified 2. Baseline comparability reported (including confounding variables)
3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
Same data collection for all cohorts Important baseline variables measured, valid, and reliable All aspects of exposure measured (dose, level, duration) Exposure adequately measured (previous, at entry, during study) Regular follow-up periods Coexposures monitored Duration of follow-up adequate Outcome(s) defined and measurable Outcome(s) valid Blind assessment of outcome(s) Analyses controls for confounding
CRITERIA FOR THE APPRAISAL OF THE METHODOLOGIC QUALITY OF CASE-CONTROL STUDIES 1. Similar population sources for cases and controls (time, place, potential for exposure) 2. Referral and sampling independent of exposure 3. Random selection of controls 4. Diagnostic criteria for cases clear, precise, and valid 5. Date of diagnosis for case operationally defined 6. Ascertainment of disease adequate for cases and controls 7. Comparison of cases and controls at enrollment reported (including confounding variables) 8. All aspects of exposure measured (level, dose, duration, etc.) 9. Exposure adequately measured (same in all groups, blinded) 10. Coexposures measured 11. Recall bias controlled 12. Data collection valid and reliable 13. Analysis according to level of exposure 14. Effect of matching assessed
CHAPTER
3b
Biomechanics of the Cervical and Thoracic Spine Jiri Dvorak and Malcolm Pope
BIOMECHANICS OF THE NECK The biomechanics of the cervical spine is determined by the shape of the vertebral bodies and the orientation of the zygapophyseal joints and can accordingly be divided into three sections: ● Upper cervical spine: occiput, atlas, axis; ● Lower cervical spine: C2-C3 to C7; ● Cervical-thoracic junction: C7 to the third thoracic vertebra (Fig. 3b.1). The primary aim of the clinician treating a patient with neck pain is to find the region or even segment responsible for pain symptoms. Because the intersegmental nerve root anastomosis
Upper cervical spine
C2
makes it almost impossible for a patient suffering from neck pain to localize the exact origin of pain,11,12,26 the clinician must base the diagnosis on functional and palpatory examinations of the cervical spine. To do this correctly requires analysis and interpretation of normal and disturbed motion patterns based on a knowledge of clinical biomechanics and an understanding of developmental anatomy. The natural aging process results in many changes in the cervical spine that must be taken into account in the clinical assessment, especially as related to range of motion. It is well established that range of motion decreases with age, mainly in the middle and lower segments of the cervical spine.4 This is due to the ongoing transformation process of the intervertebral disk and the development of uncovertebral joints14,29; later it may also be due to development of osteoarthritis of the zygapophyseal joints. In the first two decades of life, the uncovertebral spaces of the lower part of the cervical spine begin to undergo a lifelong transformation into uncovertebral joints. This transformation is a response to the compressive force of the weight of the head, which the upright posture of the body requires the cervical spine to support (Fig. 3b.2).14,28,29 The result is the formation of lateral tears of the disk annulus beginning in the second decade of life (Fig. 3b.3). These lateral tears continue to develop into the medial center part of the disk until, in the third decade, complete transverse tears commonly occur (Fig. 3b.4).28 The resulting space in the middle of the intervertebral disk partially takes over the function of the zygapophyseal joints during the second and third decades. (At this stage, the nucleus pulposus dries out, appearing on radiographs as a narrowing between the vertebrae of the lower cervical spine, which provides a convenient way for the clinician to monitor these changes.) This new space within the disk significantly reduces the loadabsorbing function of the intervertebral disk in the cervical spine. To support the load of the head, a transformation of the uncovertebral joints starts to occur.28 Instead of the original pointed shape, the uncovertebral processes now become flat
C3
C4
C5
Lower cervical spine
C6
C7
Th1
Th2
Cervical-thoracic junction
Th3
Figure 3b.1
Sections of the cervical spine.
Figure 3b.2 Drawing of the uncovertebral joints. (From Luschka H: Die Halbgelenke des menschlichen Körpers. Berlin, 1858, Reimers.)
42
Chapter 3b
●
Biomechanics of the cervical and thoracic spine
Figure 3b.3 Frontal section of the cervical spine of a 9-year-old child. Remnants of cartilage are still present. The arrow points to a space in the lateral part of the intervertebral disk at level C3-C4.
with a shape like that of a cow horn (Fig. 3b.5) and take over the load of the cranial vertebrae. The overall result is a natural transformation of the structure and shape of the uncovertebral processes that is probably responsible for much of the decreased range of motion that accompanies aging and must be taken into account in any clinical assessment of the cervical spine. In the first two decades of life, the surfaces of the articular processes are covered by a thin layer of cartilage, with the uneven surfaces filled in by a synovial fold in the joint capsule. This synovial fold has been described by Penning and Töndury21 as meniscoid. It is found within the entire cervical spine (Fig. 3b.6) and again degenerates or atrophies with increasing age.
UPPER CERVICAL SPINE: OCCIPUT/C2 The upper cervical spine, which consists of the occiput, atlas, and axis, is responsible for most of the axial rotation and some of the flexion-extension and lateral bending of the head. In addition to allowing large rotations, it must be stable enough to support the weight of the head and protect the delicate spinal cord and intervertebral arteries from injury and is therefore quite a complicated structure. Possible motion in the atlantooccipital and atlantoaxial joints is determined by the orientation of the articular processes. The occipital condyles are an oval-shaped bean-like form with a sagittal orientation of the joint axis of 28 degrees on average (Fig. 3b.7).8,10 The frontal orientation of the joint axis (Fig. 3b.8) averages 124 degrees in males and 127 degrees in females.9,27 The motion axis of the atlantooccipital joints was described by Knese9 (Fig. 3b.9). The atlantooccipital joints are described as a spheroid articulation. They are connected with a tight joint
Figure 3b.4 Frontal section of the cervical spine of a 33-year-old man. In the three lowest segments, each intervertebral disk shows a complete transverse tear; however, the upper two levels have only lateral tears. (From Töndury G, Theiler K: Entwicklungsgeschichte und Fehlbildungen der Wirbelsäule, ed 2, Stuttgart, Germany, 1990, Hippokrates-Verlag.)
capsule that limits the movements possible. The dominant movement in the atlantooccipital joint is flexion and extension of approximately 22 to 24 degrees, according to the author. Lateral bending, again according to the author, is between 5 and 10 degrees. The idea of axial rotation in this joint has long been rejected; however, newer investigations by Dvorak et al7 showed axial rotation in both in vitro and in vivo studies. A summary of movements possible in the atlantooccipital joint is shown in Table 3b.1. The atlantoaxial joint consists of four joint spaces: the two atlantoaxial lateral joints, the atlantoaxial median joint (between the anterior arch of the atlas and the dens axis), and a joint between the posterior surface of the dens and the transverse ligament, which is connected to the anterior joint space. From the medial part arises a large synovial fold in the lateral atlantoaxial joint (Fig. 3b.10).4 This joint capsule is loose, which allows for a great deal of motion. It is here that most of the axial rotation occurs. The movements possible in the atlantoaxial joints are summarized in Table 3b.2. Motion within the upper cervical spine, especially in the atlantoaxial joint, is mainly limited by ligaments that, with exception of the tectorial membrane, consist of nonstretchable collagen fibers.24,25 The tectorial membrane, which consists of elastic fibers, inserts at the great occipital foramen and distally joins the posterior longitudinal ligament. The biomechanical properties of the tectorial membrane have been studied by Oda et al,17 who documented their large elasticity.
Chapter 3b
●
Upper cervical spine: occiput/C2
Figure 3b.5 Cow horn-like shapes (arrows). Changes of the uncovertebral disks at the C4-C5 and C5-C6 levels of the same subject at the age of 47 years (A) and 49 years (B). At the same level on the lateral views, anterior and posterior osteophytes are starting to form (C and D) and narrow the intervertebral foramen at the C5-C6 level (E and F).
A
B
C
D
E
F
43
44
Chapter 3b
●
Biomechanics of the cervical and thoracic spine
Frontal orientation of joint axis 124°
Figure 3b.8 Frontal orientation of the occipital condyles according to Stoff. (From Stoff E: Verh Anat Gesch Jena 70:575, 1976.)
Y-axis
Figure 3b.6 Parasagittal section of the intervertebral joints (zygapophyseal joints) at the level of C4 and C6. The articular processes show an inclination of approximately 45 degrees. The arrow points to the synovial folds in between the intervertebral joint surfaces, which have been described by Penning and Töndury as meniscoid. (Courtesy Professor Doctor W. Rauschning, Uppsala, Sweden.)
Z-axis
X-axis
Figure 3b.9 Possible joint axis of the upper cervical spine according to Knese. (From Knese KH: Z Anat Entwickl 114:67-107, 1949.)
Table 3b.1 Possible movements in the atlantooccipital joint according to different authors Occipto-C1 joint Fick (1904) Poirer and Charpy (1926) Werne (1957)30 Penning (1978)20 Dvorak et al (1985) Clark et al (1986) Dvorak et al (1987)3 Penning and Wilmink (1987)22 Panjabi et al (1988)19
Figure 3b.7 Sagittal orientation of the occipital condyles is 28 degrees on average. (From Ingelmark BE: Acta Anat (Basel) 6:1-48, 1947.)
Flexion/extension (total) rotation Side bending (one side) (one side) Axial 50
30-40
0
50 13 35 — 22.7 —
14-40 8 10 — — —
0 0 0 5.2 4.8 4
— 24.5
— 5.5
1 7.2
Chapter 3b
A Figure 3b.10
●
Upper cervical spine: occiput/C2
B
Dissection of normal left atlantoaxial meniscoid from a fresh cadaveric specimen (A); the surface is covered with meniscoid (B).
The cruciate ligament (Fig. 3b.11) has the important function of restricting potentially dangerous anterior gliding of the atlas during flexion movement of the head while still allowing the atlas to turn freely around the dens during axial rotation. It consists of two main parts: a horizontally oriented transverse ligament and vertically oriented longitudinal fibers. The transverse ligament inserts at the medial portion of the lateral mass of the atlas. The caudal fibers are occasionally fixed at the base of the dens and may additionally stabilize the dens (Fig. 3b.12). At the level of the dens is a thin layer of cartilage covering
Table 3b.2 Summary of possible motions at the atlantoaxial joint according to various authors
C1-C2 joint Fick (1904) Poirer and Charpy (1926) Werne (1957)30 Penning (1978)20 Dvorak et al (1985) Clark et al (1986) Dvorak et al (1987)3 Penning and Wilmink (1987)22 Panjabi et al (1988)19
Flexion/ extension (total)
Side bending (one side)
Axial rotation (one side)
0
0
60
11 10 30 — 10 —
— 0 10 — — —
30-80 47 70 32.2 14.5 43.1
— 22.4
— 6.7
40.5 38.9
the transverse ligament,5 which allows the ligament to move more freely and protects it from damage caused by friction. The transverse ligament consists exclusively of collagen fibers with an interesting fiber orientation similar to a folding lattice (Fig. 3b.13). This allows extensive stretching of the ligament during axial rotation without damage to the fibers. In vitro experiments show failure of the transverse ligament to occur between 170 and 700 N.5 The main limiting structures for the upper cervical spine are the alar ligaments. Consisting exclusively of nonstretchable collagen fibers, the alar ligaments connect the dens axis with the occipital condyles and the anterior arch of the atlas (Fig. 3b.12).1,3,13 Occasionally, a loose connection is also found between the basis of the dens axis and the anterior arch of the atlas3; this has been described by Von Barrow as the atlantodental anterior ligament. According to Werne,30 alar ligaments are of great importance in limiting axial rotation (Fig. 3b.14), a belief that has been confirmed by newer investigations.5,18 In conjunction with the tectorial membrane, the alar ligaments also limit flexion of the occiput. During lateral bending (Fig. 3b.15), the alar ligament is responsible for forced rotation of the second vertebra.5,30 The apical ligament has no functional meaning and is actually a rudiment of the chorda dorsalis.10 Clinical analysis of upper cervical spine motion can be done through the use of functional radiographs. In the anteroposterior view, lateral bending can be assessed.23 Physiologic movements, gliding of the atlas in bending direction, and forced rotation of the axis are presented in Figure 3b.16 as seen on functional radiographs. Axial rotation is currently assessed through measurements of functional computed tomography and may in the future be tested by functional magnetic resonance imaging (Fig. 3b.17).2,6
45
46
Chapter 3b
●
Biomechanics of the cervical and thoracic spine
Clivus
Dura Jugular foramen
Tectorial membrane Hypoglossal canal Transverse occipital ligament Alar ligament Cruciate ligament
Atlantooccipital articulation
Atlantoaxial articulation
Posterior longitudinal ligament
Transverse ligament
Figure 3b.11 Ligaments of the upper cervical spine, posterior view. (From Lang J: Klinische Anatomie der Halswirbelsäule. New York, 1991, Georg Thieme Verlag.)
LOWER CERVICAL SPINE The anatomic structures of the motion segments of the lower cervical spine are different from those in the upper cervical spine. Their particularities include the uncovertebral joints, which support part of the axial load once the intervertebral disk loses its elasticity due to age-related transformations.14,28,29 The articular processes of the cervical spine are inclined approximately 45 degrees from the horizontal plane (Fig. 3b.18), with steeper inclinations in the lower segments. The transverse processes hide and protect the spinal nerve and vertebral artery.
Anterior atlantodental ligament Alar ligament (atlantal portion)
Alar ligament (occipital portion) Transverse ligament Figure 3b.12 Drawing of the ligaments of the upper cervical spine (axial dissection). (From Dvorak J, Froehlich D, Penning L, Baumgartner H, Panjabi MM: Spine 13(7):748-755, 1988.)
The motion segments are connected and stabilized by ligaments, anteriorly by the anterior longitudinal ligament (Fig. 3b.19) and dorsally by the posterior longitudinal ligament. The density of nociceptive and mechanoreceptive innervation of the posterior longitudinal ligament is high in comparison with other cervical spine ligaments and the disk.16 This results in a very sensitive ligament that indirectly controls the innervation of neck muscles through nociceptive and mechanoreceptive reflexes.32 The laminae are connected by the strong ligamentum flavum, which consists almost exclusively of elastic fibers and is a major limiting structure in flexion movement. The dominant motion in the lower cervical spine is flexionextension. Different parameters can be measured with flexionextension x-ray views, including segmental rotation, translatory movement, and the location of the center of rotation (Fig. 3b.20).7 Because a significant motion difference exists between actively and passively performed movements, the use of passively performed radiographs has been recommended in diagnosing segmental instability, such as can occur after trauma (Fig. 3b.21).6,7 The first description of the center of rotation in healthy adults came from Penning and Töndury’s measurements21 of flexion and extension radiographs. The center of rotation has been determined with computer-assisted methods7 and has confirmed Penning and Töndury’s findings (Fig. 3b.22). Table 3b.3 shows the relevant data on flexion-extension movements of healthy adults for in vitro and in vivo examinations. Table 3b.4 presents data on rotation, translation, and center of rotation as measured by computer-assisted methods on a healthy population.7 Lysell15 described the so-called top angle, or segmental arch, as being flat at the level of C2 and steep at the lower cervical spine. Motion of the upper segments during flexion-extension is therefore fairly horizontal, whereas motion of the lower segments is more like that of an arc (Fig. 3b.23).
Chapter 3b
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Lower cervical spine
Figure 3b.13 The orientation of the collagen fibers of the transverse ligament is similar to a folding lattice and allows extensive stretching of the ligament during flexion and axial rotation without damage to the fibers.
Figure 3b.14 Drawing of possible movements in the atlantoaxial joint during axial rotation of the head according to Werne. (From Werne S: Acta Orthop Scand Suppl 23:80, 1957.)
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Left lateral bending –∅z
y
Figure 3b.15 Function of the alar ligaments during side bending of the head. (From Dvorak J, Froehlich D, Penning L, Baumgartner H, Panjabi MM: Spine 13(7):748-755, 1988.)
Right lateral bending y y
y1
+∅z y1
C0
C1 +x
–x + ∅y
+∅y C2
Figure 3b.16 Forced rotation of the axis and gliding of the atlas in the direction of bending as seen from functional radiographs in the anteroposterior view. (From Reich C, Dvorak J: Manual Med 2, 1986.)
Figure 3b.17 Functional computed tomography of the upper cervical spine during axial rotation within the atlantoaxial and atlantooccipital joints.
Chapter 3b
Figure 3b.17
●
Lower cervical spine
Cont’d
Figure 3b.18 Orientation of the articular processes of the lower cervical spine in the frontal plane. (From White AA, Panjabi MM: Clinical biomechanics of the spine, ed 2. Philadelphia, 1990, JB Lippincott.)
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Biomechanics of the cervical and thoracic spine
Figure 3b.19 Ligaments of the anterior and posterior parts at the lower cervical spine. (From White AA, Panjabi MM: Clinical biomechanics of the spine, ed 2. Philadelphia, 1990, JB Lippincott.)
D
G F
A C B E D
H I
G. Facets F. Capsular ligament
E. Intertransverse ligament A. Anterior longitudinal ligament
I. Interspinous and superspinous ligaments
B. Anterior one-half annulus fibrosus C. Posterior one-half annulus fibrosus
H. Ligamentum flavum
D. Posterior longitudinal ligament
Y RX
BY BZ
+Y AY
+RY AZ
+RX +X +Z
+RZ CRY Z X
CRZ
Figure 3b.20 Parameters for measurement of segmental motion using computer-assisted methods. RX is the rotation about the x-axis; CRY and CRZ are the centers of rotation of the Y and Z rotations, respectively; AY, AZ, BY, and BZ are the translations of point A in the Y and Z directions and point B in the Y and Z directions, respectively.
Chapter 3b
A
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Lower cervical spine
B
D
C Figure 3b.21 Female, aged 51, 1 year after injury to the cervical spine. The examination has been performed during active and passive motion (A-D) and measured according to Penning’s method (E and F).
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Biomechanics of the cervical and thoracic spine
35
Figure 3b.21 Cont’d According to the functional diagram, there is a significant difference in segmental motion, especially as related to segments C3-C4 and C6-C7. Drawing the vertebral bodies on a transparent paper (G) makes the difference obvious. (From Dvorak J, Froehlich D, Penning L, Baumgartner H, Panjabi MM: Spine 13(7):748-755, 1988.)
Hypermobile 30 25
Passive
20 15 10 5 0 C1/C2
C2/C3
E
C3/C4
C4/C5
C5/C6
C6/C7
Average + 2 STDV Average + 1 STDV Average Average – 1 STDV Average – 2 STDV Z.A., F, 51y
35 30 25
Active
20 15 10 Hypomobile
5 0 C1/C2a
C2/C3a
F
C3/C4a
C4/C5a
Average + 2 STDV Average + 1 STDV Average Average – 1 STDV Average – 2 STDV Z.A., F, 51y
Active
Active Passive
Passive
Hypermobile
G
Z.A., f, 51Y
C5/C6a
C6/C7a
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53
Table 3b.4 Averages and standard deviations of rotations, translations, and coordinates of center of rotation as measured by computer-assisted methods Parameter* C1-C2 C2-C3 C3-C4 C4-C5 C5-C6 C6-C7 RX (deg) Male RX (deg) Female AZ (mm) AY (mm) BZ (mm) BY (mm) Penning
Dvorak
Figure 3b.22 Determination of the center of rotation by graphic method (Penning, 1960) and by using computer-assisted methods on a normal population. (From Dvorak J, Schneider E, Saldinger P, Rahn B: J Orthop Res 9:828-834, 1991.)
CRZ (mm) CRY (mm)
15.4 6.1 12.9 3.4 –3.8 1.6 6.2 2.3 –1.4 1.4 8.1 3.0 –4.1 4.2 30.0 5.6
11.7 3.1 12.3 3.0 2.4 0.9 1.8 0.8 6.9 1.7 3.0 1.3 4.0 3.5 9.4 4.8
16.0 2.5 18.3 4.7 3.2 1.0 2.3 1.0 8.5 1.8 3.6 1.2 4.3 2.7 9.7 3.4
20.1 2.8 22.1 3.9 3.6 1.2 2.9 0.7 10.0 1.9 4.2 1.0 6.0 2.2 10.4 2.8
21.5 3.9 24.1 4.0 2.9 1.1 3.2 0.8 9.8 1.9 4.3 1.0 6.4 1.8 12.9 2.5
21.0 4.0 21.8 3.5 2.0 0.9 3.1 0.8 8.4 1.9 3.9 0.9 6.4 2.5 17.2 2.1
*See Figure 3b.20 for definitions.
Table 3b.3
Summary of flexion-extension movements of healthy adults in vivo and in vitro
Flexion/Extension (Total) C2-C3 C3-C4 C4-C5 C5-C6 C6-C7
Dvorak (1988) (In Vivo/Passive)
Dvorak (1988) (In Vivo/Active)
10.0 15.0 19.0 20.0 19.0
12.0 17.0 21.0 23.0 21.0
White and Panjabi
(1978)31
8.0 13.0 12.0 17.0 16.0
Penning (1978)20 (In Vivo/Active) 12.0 18.0 20.0 20.0 15.0
C2
C4
C7
Figure 3b.23 Segmental arch of the top angle according to Lysell.9 The flatter the articular surfaces, the flatter the top angle of the motion segments and vice versa.
Left bending
Neutral
Right bending
Figure 3b.24 Coupled axial rotation during lateral bending of the head. (From White AA, Panjabi MM: Clinical biomechanics of the spine, ed 2. Philadelphia, 1990, JB Lippincott.)
Chapter 3b
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Biomechanics of the cervical and thoracic spine
Table 3b.5a Values of main lateral bending according to various authors Main side bending (one side)
Moroney (1988) (in vitro FSU)
C2-C3 C3-C4 C4-C5 C5-C6 C6-C7
4.7 4.7 4.7 4.7 4.7
Table 3b.5b Values of coupled axial rotation according to various authors
White and Penning (1978)20 Panjabi (in vivo/active) (1978)31 6.0 6.0 6.0 6.0 6.0
10.0 11.0 11.0 8.0 7.0
Coupled axial rotation (one side) C2-C3 C3-C4 C4-C5 C5-C6 C6-C7
Dvorak (1987)3 (in vivo/passive) 3.0 6.5 6.7 7.0 5.4
Penning (1978)20 (in vivo/ active) 3.0 6.5 6.8 6.9 5.4
White and Panjabi (1978)31 9.0 11.0 12.0 10.0 9.0
FSU, functional spinal unit.
Lateral bending of the cervical spine is normally coupled with axial rotation to the same side.15,31 This means that the spinal processes are moving in a direction opposite the motion (Fig. 3b.24). This coupled motion is of clinical importance because palpation of the spinal processes can serve as an indirect indicator of disturbed function in motion segments. The lateral bending of the cervical spine below the first cervical vertebra has been variously reported by different researchers. According to Penning,20 the lateral bending is 35 degrees, whereas White and Panjabi31 reported between 4 and 10 degrees per motion segment. Axial rotation, as measured with functional computed tomography, is between 3 and 7 degrees,2,22 but an in vitro study19 showed a higher result, between 8 and 12 degrees. Tables 3b.5a and 3b.5b summarize the segmental motions for lateral bending with coupled axial rotation according to various authors.
10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
20. 21.
REFERENCES
22. 23.
1. 2.
Cave AJE: On the occipito-atlanto-axial articulations. J Anat (Lond) 68:416, 1934. Dvorak J, Hayek J, Zehnder R: CT-functional diagnostics of the rotatory instability of upper cervical spine. Part 2. An evaluation on healthy adults and patients with suspected instability. Spine 12:726-731, 1987. 3. Dvorak J, Panjabi MM: Functional anatomy of the alar ligaments. Spine 12:183-189, 1987. 4. Dvorak J, Antinnes JA, Panjabi M, Loustalot D, Bonomo M: Age and gender-related normal motion of the cervical spine. Spine 17(105):5393, 1992. 5. Dvorak J, Schneider E, Saldinger P, Rahn B: Biomechanics of the craniocervical region: the alar and transverse ligaments. J Orthop Res 6:452-461, 1988. 6. Dvorak J, Froehlich D, Penning L, Baumgartner H, Panjabi MM: Functional radiographic diagnosis of the cervical spine: flexion/extension. Spine 13(7):748-755, 1988. 7. Dvorak J, Panjabi MM, Novotny JE, Antinnes JA: In vivo flexion/extension of the normal cervical spine. J Orthop Res 9:828-834, 1991. 8. Ingelmark BE: Üeber den cranicervicalen Übergang beim Menschen. Acta Anat (Basel) 6:1-48, 1947. 9. Knese KH: Kopfgelenk, Kopfhaltung und Kopfbewegung des Menschen. Z Anat Entwickl 114:67-107, 1949.
24.
25. 26. 27. 28. 29. 30. 31. 32.
Lang J: Craniocervical region, osteology and articulations. Neuroorthopedics 1:67-92, 1986. Lang J: Klinische Anatomie der Halswirbelsäule. New York, 1991, Georg Thieme Verlag. Lang J, Bartram CT: Ueber die Fila articularia der Radices ventrales et dorsales des menschlichen Rückenmarkes. Gegenbaurs Morphol 128:417-462, 1982. Ludwig K: Üeber das Lig. alare dentis. Z Anat Entwickl Gesch 116:442, 1952. Luschka H: Die Halbgelenke des menschlichen Körpers. Berlin, 1858, Reimers. Lysell E: Motion in the cervical spine. An experimental study on autopsy specimens. Acta Orthop Scand Suppl 123:1-61, 1969. Mendel T, Wink CS, Zimny ML: Neural elements in human cervical intervertebral discs. Spine 17(2):132-135, 1992. Oda T, Panjabi MM, Crisco JJ, Bueff HU, Grob D, Dvorak J: Role of tectorial membrane in the stability of the upper cervical spine. Clin Biomech 7(4):201-207, 1992. Panjabi M, Dvorak J, Crisco JJ, Oda T, Wang P, Grob D: Effects of alar ligament transection on upper cervical spine rotation. J Orthop Res 9:584-593, 1991. Panjabi MM, Dvorak J, Duranceau J, Yamamoto I, Gerber M, Rauschning W, Beuff HU: Three-dimensional movements of the upper cervical spine. Spine 13(7):726-730, 1988. Penning L: Normal movement of the cervical spine. AJR Am J Roentgenol 130: 317-326, 1978. Penning L, Töndury G: Entstehung, Bau und Funktion der meniskoiden Strukturen in den Halswirbelgelenken. Z Orthop 98:1-14, 1964. Penning L, Wilmink JT: Rotation of the cervical spine: a CT study in normal subjects. Spine 12:732-738, 1987. Reich C, Dvorak J: The functional evaluation of craniocervical ligaments in sidebending using x-rays. Manual Med 2, 1986. Saldinger PF: Histologische Untersuchung des kraniozervikalen Bandapparates im Hinblick auf Weichteilverletzungen der Halswirbelsöule. Diss. med., Bern, 1987 (Leitung J. Dvorak). Saldinger PF, Dvorak J, Rahn BA, Perren SM: Histology of the alar and transverse ligaments. Spine 15:257-261, 1990. Simmons E, Marzo J, Kallen F: Intradural connections between adjacent cervical spinal roots. Spine 12(10):964-968, 1987. Stoff E: Zur Morphometrie des oberen Kopfgelenks. Verh Anat Gesch Jena 70:575, 1976. Töndury G, Theiler K: Entwicklungsgeschichte und Fehlbildungen der Wirbelsäule, ed 1. Stuttgart, Germany, 1958, Hippokrates-Verlag. Töndury G, Theiler K: Entwicklungsgeschichte und Fehlbildungen der Wirbelsäule, ed 2. Stuttgart, Germany, 1990, Hippokrates-Verlag. Werne S: Studies in spontaneous atlas dislocation. Acta Orthop Scand Suppl 23:80, 1957. White AA, Panjabi MM: The basic kinematics of the human spine. Spine 3:12-20, 1978. Wyke B: Neurological mechanisms in the experience of pain. Acupunct Electrother Res 4:27-35, 1979.
CHAPTER
3c
Evaluation of the Neck Ronald Moskovich and Anthony Petrizzo
Neck, or cervical spine, pain with concomitant disability is a common presentation among injured workers. Neck pain, however, is less prevalent than low back pain as a cause of worker absenteeism and represents less than 2% of all workplace injuries. The 1-year prevalence rate of non–work-related neck pain in most industrialized countries is approximately 20%; the prevalence of neck pain during a 1-month period in the United Kingdom is reported to be 14%.21 In a cohort of patients with neck pain, almost half had persistent neck pain 1 year later.10 Overall, back pain is commonly cited as the second leading cause of absenteeism in workers and the primary cause of workers’ compensation claims. In the Saskatchewan working age population, 10% experience severe neck pain, with up to 5% having neck pain that severely affects their activities of daily living.4 Most of these injuries are diagnosed as either a strain or sprain. For these types of milder neck injuries, analogous to the lower spine, it is a challenge to determine the precise pathoanatomic diagnosis before the initiation of therapy.
STANDARD EXAMINATION Evaluation of the cervical spine requires a history, using standard interviewing principles; a physical examination, focused on elimination of the pertinent negatives; and utilization of functional assessment scales to measure the impact of cervical dysfunction on common daily activities. This crucial assessment of the history with specific questions is used to rule out or determine the need for an urgent workup, a static and/or dynamic physical examination, laboratory studies, and further diagnostic and prognostic evaluations. Although the approach to a patient injured at work should not differ from that of a patient who injured his or her neck during recreational activity, patients referred for work-related cervical spine injury have another aspect added to their evaluation and assessment: critical return of the patient to pre- or near preinjury function to resume prior income-related activities as soon as possible.
DISABILITY EXAMINATION The critical distinction between a standard medical examination and a disability examination or impairment evaluation, lies not only in obtaining the information, but what to do once pertinent information is obtained (Table 3c.1).5 For example, once it is determined that a patient fell at work and is diagnosed and treated for the neck injury, the patient must be further evaluated for his or her ability to attend work and function in the workplace, albeit with possible job modifications.
This is referred to as a disability evaluation or examination. A more comprehensive overview of a disability evaluation is described below.5
IMPAIRMENT EVALUATION An impairment evaluation is another type of assessment tool regarding injury in the workplace. The distinctive contribution of an impairment evaluation is the measure of functional loss or derangement of any body part, organ, or organ system. Another purpose of an impairment evaluation is to measure, define, and determine the status of the patient’s (claimant’s) general health at a particular point in time. Establishing impairment can be accomplished using different objective methods, based on guidelines set by the American Medical Association.3 A diagnosis-related estimate is an impairment method based on eight diagnosis-related categories (i.e., muscle atrophy, guarding, asymmetric motion) for each of the three spinal regions. A second approach in the diagnosis-related estimate method is the diagnosis of a fracture or dislocation of the spine that, after appropriate tests and treatment has been rendered, requires no further verification. Impairment can also be documented based on assessment of the patient’s range of motion (ROM). This method is based on loss of active range of motion (AROM) in addition to an accompanying diagnosis and a spinal nerve deficit. The AROM approach is usually reserved for instances when a diagnosisrelated estimate is not applicable.3 Interestingly, the ability to participate in work activity is not included in calculating impairment percentages. The impairment evaluation is performed after the patient is determined to have achieved the highest possible level of recovery but before they return to work-related activity. Any deviation from predetermined normal criteria or from the patient’s prior health status is translated into an impairment rating. Impairment can then be converted to impairment percentages, which reflect the degree to which the impairment decreases the individual’s ability to perform activities of daily living. The development of an impairment rating is based on clinical decision making, whereas its purpose usually is to determine financial remuneration to the claimant by a third party.5
Table 3c.1 1. 2. 3. 4. 5. 6. 7. 8.
Goals of a disability examination5
Establish a diagnosis Quantify impairment Determine if examinee is capable of performing specified tasks Determine if examinee can attend work Determine if examinee can work in the occupational environment Determine if worker poses a threat to others in the workplace Make a recommendation regarding job modifications Extrapolate into the future a. Recommend treatment(s) b. Derive a time course c. Specify how treatment(s)/time will change points 1 through 7
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Evaluation of the neck
EVIDENCE-BASED MEDICINE In recent years, there has been a shift by research and evaluative bodies to apply evidence-based medicine (EBM) techniques and outcomes as a foundation for clinical decision making.11 The U.S. Agency for Health Care Policy and Research (AHCPR), which convenes expert multidisciplinary nonfederal panels to develop clinical practice guidelines for specific conditions and treatments, has similarly embraced the EBM perspective: Comprehensive evaluation of the results from randomized control studies is the best available scientific evidence on which to base clinical decision making. The working goal of the AHCPR’s musculoskeletal panel is to determine a model for the clinical utility of various diagnostic and therapeutic interventions for low back pain.5 This model for evaluating low back pain, although not interchangeable for cervical issues, has sound principles that can be effectively applied to treat cervical spine disorders. The AHCPR promotes a change in the former paradigm for treating acute low back pain, from focusing care exclusively on the pain itself to improving patients’ activity tolerance once all red flags for critical disorders have been eliminated.1 It is our suggestion that the low back pain model, although not a blueprint for management, can be applied to effectively treat cervical disorders as well. The fact that this approach could be advantageous for both clinician and patient, at minimum, underscores the importance and necessity of excluding red flags through the history and physical examination. The fact that the patient would now be more focused on movement behavior, and perhaps earlier than with prior treatment paradigms, underscores an added relevance to work-related injury cases. An interest in consistent and well-substantiated assessment and treatment paradigms are not limited to clinical medicine settings. A landmark U.S. Supreme Court ruling, in 1993, amended the Federal Rules of Evidence to require experts giving medical depositions to have reliable data to substantiate their testimony.2 Since that ruling, concepts supporting and policies enforcing EBM have expanded through input from epidemiology, outcomes research, policy makers, and clinicians. To adopt an evidencebased approach for the care of patients with neck problems, it is important that practicing clinicians understand the process of critically evaluating the accuracy of individual studies in the literature, know the natural history of cervical spine disorders, and be able to use that knowledge and their clinical experience as a check-and-balance to their practice decisions.
HISTORY Interview A description of the injury and of the precipitating events provides indispensable information for the treating physician. The inciting incident can be acute in onset or chronic with a progressing debility. Documentation must include how and when the precipitating event occurred as well as its duration. The history should begin with the identification and essential demographics of the patient: age, sex, race, and occupation. The chief complaint(s) should be recorded, at least initially, in
the patient’s own words. History of the present illness should include the location, duration, and concise description of symptoms and the timing, setting, any aggravating or relieving factors, and associated manifestations and prior treatments, to include their effects. It is important to establish whether or not there is a relationship between the injury and symptoms and the patient’s work activities and/or work setting. This part of the history may require close attention to draw subtle but meaningful information from the patient, in part because their pain or discomfort can make this information difficult to convey or because they may not be aware of the relationship. From this type of detailed dialogue with the patient, a statement of the probability that the injury is work-related is developed. The primary cause of many injuries can be obvious, whereas causes or etiologies of the injuries require deeper evaluation. Patients commonly present with neck complaints after a vehicular injury, a fall, or rough sport contact. Workers who perform overhead activities or who carry loads that could strain the neck muscles may also develop debilitating neck or arm pain. The symptoms of cervical disease can radiate cephalad to the skull or caudal to the extremities, where repetitive light to moderate work activity may be poorly tolerated and reveal underlying existing pathologies. The presence of a radicular component to the patient’s pathology necessitates documentation of the nature and sources of each of the symptoms. The patient’s prior medical history and a review of systems provide an account of his or her general state of health. A thorough musculoskeletal history should be done to establish the presence or absence of overall joint pain, stiffness, swelling, arthritis, gout, and low back pain. All illnesses and surgeries should be recorded. A history of gastrointestinal diseases, specifically gastritis and ulcerative disorders, should be taken, because patients with cervical ailments may require treatment with nonsteroidal antiinflammatory drugs. Specific hereditary predisposing conditions for inflammatory arthropathies, such as rheumatoid arthritis, psoriatic arthritis, and ankylosis spondylitis, may be discovered in the review of family history. Details of tobacco smoking should also be incorporated into the history. Positive associations between current smoking and nonspecific back pain were found in 18 of 26 studies in men and 18 of 20 studies in women.3 Any history of accidents, at work or home, or occupational exposures must be explored, because they can reveal risky habits or hazardous conditions. Relevant workers’ compensation issues should begin to emerge through the history, but their presence or impact may continue to be revealed during care of the patient. A comprehensive psychosocial history is a valuable but often overlooked part of the evaluation. Nonphysical or psychosocial factors such as job or life satisfaction can affect disability status and treatment outcome. Key features of this review include the patient’s life-style, home situation, and vocational and recreational activities. Notably, a history of mental illness, in particular depression and anxiety, must be addressed. Patients may be reticent to disclose such information, so its importance and practical function for treatment and recovery should be carefully and objectively expressed to the patient and, if necessary, sensitively probed. Finally, a list of the patient’s current medications, including prescription, herbal, holistic, over-the-counter, and “borrowed” must be reviewed.
Chapter 3c
Table 3c.2
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Physical examination
Red flags in cervical spine evaluation
Tumor
Osteomyelitis
Spinal cord compression
Trauma
Age > 50 Cancer history Unexplained weight loss Nocturnal pain
Intravenous drug abuse History of immunosuppression History of fever, night sweats History of urinary tract infection or skin infection
Bowel/bladder dysfunction Gait dysfunction, balance problems Fine motor dysfunction, clumsiness Arm pain, weakness
Trauma in patient < 50 years Low velocity trauma in patient > 50 Corticosteroid use
Modified from Clinical Practice Guidelines, AHCPR.
Red flags After inquiring about the presenting complaint, it is appropriate to focus on “red flags,” the presence of which command urgent evaluation. These red flags include a history of trauma, tumor, or infection, among others. Patients should be questioned regarding changes in any bowel and bladder habits, specifically an inability to fully empty the bladder, a feeling of fullness after urinating, and any history of bladder or bowel incontinence. Again, these may be difficult questions for patients, and they should understand that even quite minimal changes in these behaviors may be important to follow-up if they occur with any frequency or intermittency. Even though a neurologic examination will be done, it is important to question the patient about noticing any loss of manual dexterity as well as the development of headaches. Patients should be specifically questioned regarding recent fever, weight loss, night sweats, and nocturnal pain. Table 3c.2 identifies some of the more common red flags.
PHYSICAL EXAMINATION Inspection The physical examination typically begins with a general visual inspection of the patient’s health and conditioning. It is important to inspect the skin for general and isolated color changes. Warmth and redness are common physical findings with acute musculoskeletal strain. Posture is examined for asymmetry in positions such as lateral bending or rotation and the presence of abnormal sagittal and coronal curves. Ambulation should be observed for an ataxic broad-based gait, commonly seen in myelopathy, and any inability to heel-walk or toe-walk, seen with motor weakness and ability to accomplish tandem gait (walk on a straight line), which may be compromised in myelopathy or cerebellar disorders.
Range of motion A regional evaluation of the spine is part of the overall assessment. The spine has four normal sagittal curves. There is a fixed sacral kyphosis and a primary thoracic kyphosis that are apparent at birth. Cervical lordosis develops when the infant can maintain an upright head posture. The next curve, which typically develops once a child starts to walk, is the lumbar lordosis. Between each
of the sagittal curves is a transition zone where alignment is neutral relative to the vertical sagittal axis of the body. The cervical spine is well balanced in the sagittal plane so that C1 and C7 should be centered over the weight-bearing axis, and a plumb line should descend through T12 and continue caudally through the anterior portion of S1. The cervical lordotic curve normally ranges from 25 to 50 degrees with an apex at C4 (Fig. 3c.1). Assessment of cervical ROM is important from a functional and diagnostic perspective. ROM should be assessed with an inclinometer and recorded during the examination. Inclinometers can be mechanical or electronic, and the use of even a simple home-made device is preferable to a “guestimation.” An inclinometer can easily be made by punching a small hole through the center point of a protractor, passing a string through the hole and through a washer (to act as a weight), and tying the string in a loop. The loop of string indicates the degree of inclination on the protractor scale. A plastic scoliosis protractor can be used or a paper protractor downloaded from www.eece.ksu.edu/∼hkn/ files/protractor.pdf and pasted onto a card for use. C1, C2, and C7 are atypical vertebrae with respect to morphology and function, whereas C3 to C6 are commonly described as typical cervical vertebrae. The atlantooccipital joint acts as a pivot for the flexion/extension motion of the cranium, with 13 degrees average flexion/extension and 8 degrees lateral bending, allowing only a few degrees axial rotation.6 The atlantoaxial complex (C1-C2) has a total axial rotation of approximately 80-90 degrees, coupled with a flexion and extension of approximately 10 degrees and minor lateral bending. The prominent motion of the subaxial cervical spine is flexion/extension with some segmental rotation, the latter being both facilitated and constrained by the alignment of the apophyseal joints and the presence of the uncinate processes. The C5-C6 interspace is generally found to have the greatest range of flexion and extension motion of the subaxial spine.6 Subtle secondary motion, or coupled motion, of the cervical spine occurs in response to the primary motion. The coupled pattern of the cervical spine occurs with motion in the axial, sagittal, or coronal plane, for example, the direction of axial rotation in the subaxial spine is such that the spinous processes rotate into the convexity of the spine on side bending. AROM is performed by the patient at the instruction of the examiner and is one of the cornerstones in the determination of functional limits, assessment of improvement, and demonstration of disability when evaluating permanent impairment.5 AROM is performed by the patient alone on instruction by
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Evaluation of the neck
Figure 3c.1 Lateral radiographs of the cervical spine of various individuals of different ages. Clockwise from top left: A 16-year-old girl with normal cervical spine lordosis and normal disk space. A 46-year-old woman with mild loss of the normal cervical lordosis, noted in the mid-upper cervical spine. A 51-year-old woman with multilevel cervical spondylosis manifesting as narrowing of the intervertebral disk spaces at C4-C5 and C5-C6 with endplate changes and marginal osteophytes. A 73-year-old woman with advanced spondylosis and a frank reversal of the normal cervical lordosis as a result of marked multilevel diskogenic degenerative changes.
the examiner. In passive range of motion (PROM), the patient is assisted by the examiner to reach the maximum range. Often, PROM allows for more ROM in all planes. In the absence of pain, PROM can be performed to the anatomic barrier, whereas AROM is typically hindered by a physiologic barrier created by extant pathology or patterns of disuse not related to the presenting symptoms. ROM of the cervical spine is performed by having the patient rotate the head to the right and to the left. End points of motion should be symmetric. The patient should
be able to bend the head to the right and left, as though attempting to touch the ear to the shoulder but keep the shoulder from rising at the same time. This motion is also referred to as side or lateral bending. Flexion/extension ROM is assessed by having the patient flex or touch the chin to the chest and then extend or bend the neck backward. Neck extension is generally restricted and may be painful for patients with cervical stenosis or nerve root compression, although the opposite may also occur. All these motions should be recorded in degrees using a goniometer
Chapter 3c
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Neurologic examination
or, preferably, an inclinometer. Spurling’s test (see below) may be administered at this time.
Palpation While the patient is lying down, a thorough palpatory assessment of muscle tension, tenderness, and tissue texture abnormalities from spasm or contracture of the superficial anterior and posterior musculature must be performed. The examination of the neck with the patient seated and the examination of the upper thoracic spine are often integrated. The sternocleidomastoid muscle runs obliquely from the mastoid process of the skull to the lateral border of the sternal notch and may be injured in sudden hyperextension injuries of the cervical spine. The trapezius muscle originates from the inion and the spinous processes from C1 (atlas) to T12 (last thoracic vertebra); it flares out to insert on the clavicle, acromion, and spine of the scapula. Spasm in this muscle can best be palpated on the lateral aspect of the neck. The scalene muscles are palpable in the anterior paratracheal area. They originate on the transverse processes of the cervical vertebrae and insert bilaterally on the first and second ribs. These muscles function to laterally flex the neck (side bend) and help the attached ribs elevate during forced inspiration. Within this region, three anatomic sites of neural compression have been implicated in thoracic outlet syndrome: between the anterior and middle scalenes, between the clavicle and first ribs, and between the pectoralis minor and the upper ribs. The levator scapula originates on the rib’s posterior tubercles and inserts on the upper medial border of the scapula. This muscle is tender to palpation when in spasm. Anomalous cervical ribs may be palpated and can be confirmed radiologically; they may be involved in thoracic outlet obstruction but usually exist only as an anatomic anomaly. The cervical spine has an abundant supply of superficial and deep interconnected lymphatics to return the lymph to the vascular compartment in the thorax. Palpation of the cervical lymph nodes can elicit tenderness in adenopathy caused by tumor or infection.
NEUROLOGIC EXAMINATION The neurologic examination provides both direct and indirect methods of determining damage to the spinal cord and nerves by examination of their sensory, motor, and reflex distribution. The aim is to identify an anatomic level for possible neurologic deficit.
Sensory examination and dermatome testing The sensory component for each spinal nerve originates in a dermatome, a segmental portion of the skin. Each cutaneous innervation generally follows the distribution of the underlying muscle innervation (Fig. 3c.2). However, there are exceptions and variations to this generalization in the cervical spine. The suboccipital nerve (dorsal ramus of C1) exits the spine between the skull and C1 and has no cutaneous distribution. The dorsal branch of C2 is the greater occipital nerve, which distributes
Figure 3c.2 The cervical dermatomes are indicated. The C5 to T1 dermatomes are expressed in the upper extremity and develop as the embryonic limb bud does, extending from the trunk.
cranially upto provide sensation to the vertex of the scalp. The lesser occipital nerve of the cervical plexus (ventral ramus of C2) supplies sensation to the skin of the scalp behind the ear as well as the skin of the ear. Pathologic conditions affecting the C2 nerve result in occipital neuralgia. The dorsal ramus of C3 (third occipital nerve) distributes cutaneous sensation to the upper neck and scalp. The dorsal rami (sensory) of C4-C6 provide sensation to the posterior neck in a cephalad to caudal direction. The cutaneous nerves of the upper limb, on the other hand, are derived from branches of the brachial plexus, and thus each one is comprised of more than one nerve root.24 The dermatomal pattern in the extremities is patterned on orderly embryologic limb development. Clinical differentiation between dermatomal sensory loss and a peripheral nerve deficit helps distinguish cervical radiculopathy from other neurologic problems. The upper lateral cutaneous nerve of the arm is the termination of the lower branch of the axillary nerve. Its cutaneous distribution is the lower half of the deltoid muscle and the long head of the triceps brachii. The sensory branches of the radial nerve are the posterior cutaneous nerve of the arm that distributes to the middle third of the back of the arm, the posterior cutaneous nerve of the forearm, and the superficial branch of the radial. All the above arise from the posterior cord of the brachial plexus. The lateral cutaneous nerve of the forearm distributes into the lower lateral and the anterior surface of the arm. This nerve is the cutaneous branch of the musculocutaneous nerve which arises from the lateral cord of the brachial plexus. The medial cutaneous nerve of the arm provides sensation to the posterior surface of the lower third of the arm, as low as the olecranon, and the medial cutaneous nerve of the forearm covers the ulnar aspect of the forearm down to the hand. These are sensory branches of the ulnar which arises off the medial cord of the brachial plexus. The shoulder receives its cutaneous sensation proximally from the cervical plexus, specifically from the supraclavicular nerves of C3 and C4.
Motor strength examination The dorsal and ventral rootlets at each level unite to form a mixed spinal nerve. The motor roots arise from the anterior horn
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C4 Dorsal scapular n. Suprascapular n.
Axillary n. Radial n. Median n. Ulnar n.
C8
rior ste Po
T1 l T2 ia ed M Medial Long pectoral n. thoracic n.
To subscapularis teres major latissimus dorsi
Medial cutaneous nerves to the arm and forearm
Figure 3c.3 Diagram of the brachial plexus. There is a complex interconnection of nerve tissue. Note the differentiation between the nerve roots, which arise segmentally, and the ultimate peripheral nerves, which are usually an amalgam of two or more nerve roots.
cells and thus lie ventral to the sensory rootlets; they exit the spinal cord through the foramen above the named cervical vertebrae and carry their fibers to the striated muscles. Because there are eight cervical nerves and seven cervical vertebrae, the C8 nerve root exits below the C7 body. From C5 to T1, these nerves separate and recombine to form the brachial plexus where the fibers are reconfigured into trunks, divisions, and cords before finally forming independent branches (Fig. 3c.3). The resulting nerves are thus of mixed root origin and are named musculocutaneous, axillary, radial, median, and ulnar, innervating muscles in the upper extremity. Evaluation of the efferent nerves is achieved by testing the muscles they innervate. Motor strength is objectively evaluated using a six-point grading system (Table 3c.3). Testing begins with assessment of the patient’s breathing. The phrenic nerve (C3-C5) is the motor nerve to the diaphragm, although it also contains many sensory and sympathetic fibers. If the patient is breathing adequately without the use of accessory musculature, the diaphragm is functionally intact.19 The C5 nerve root innervates the deltoid muscle, and along with C6 it also innervates the biceps muscle. The C6 nerve root also innervates the wrist extensors. The C7 motor distribution includes the triceps muscle, the wrist flexors, and finger extensors.
Table 3c.3
Reflex examination
C7
l era Lat
Musculocutaneous n.
C5 C6
Lateral pectoral n.
These demonstrate the overlapping character of upper limb innervation (Fig. 3c.4).
Evaluation of motor strength15
5 - Normal 4 - Able to overcome moderate resistance (not symmetric to contralateral side) 3 - Able to accomplish full range of motion against gravity 2 - Able to accomplish full range of motion with gravity eliminated 1 - Only trace muscle contraction 0 - Flaccid
Pathologic alterations in the basic stretch reflexes are important findings in neurologic disease. Deep tendon reflexes are a misnomer, because they are actually muscle stretch reflexes initiated by excitation of the afferent muscle spindle fibers. These 1a afferent fibers synapse directly onto the proximal dendrites and soma of the motor neurone, completeing the reflex arc, resulting in a reflex muscle contraction. These monosynaptic reflexes are helpful for localizing the level of pathology in the cervical spine or nerve root and for differentiating a lower motor neuron lesion from an upper motor neuron lesion. Although some examiners grade the intensity of reflexes on a scale of 0 to 3, we believe it is more realistic to grade them as absent or present, because there are variable individual reactions to reflex testing. Deep tendon reflexes can be influenced by age, metabolic factors, and anxiety levels in the patient. Brisk, or hyperreflexic responses, however, may be abnormal findings on reflex testing. Typically, upper motor neuron lesions involve the spinal cord and cause hyperreflexia. Lower motor neuron lesions depress reflexes. For example, the nerve of C5 mediates the biceps reflex and that of C6 can be tested through the brachioradialis reflex and C7 through the triceps reflex (Table 3c.4 and Figs. 3c.5, 3c.6, and 3c.7).
Long-tract signs After injury to the corticospinal tract of the spinal cord, abnormal reflexes, or long-tract signs, can be elicited that are not typically found in normal individuals. These reflexes suggest the presence of lesions proximal to the anterior horn cells and represent clinical signs of myelopathy. Below are select examples. ● Clonus is elicited by the examiner rapidly dorsiflexing the ankle and maintaining slight pressure while counting the pulsed contractions on resistance. Greater than four beats of clonus is considered abnormal. ● Lhermitte’s sign (a.k.a. the barber’s chair phenomenon) is a symptom of radiating shock-like sensation down the back with neck flexion. ● Babinski’s sign is an abnormal reflex elicited by stroking the lateral border of the plantar surface of the foot with a blunted pointy object, which elicits dorsiflexion of the great toe with fanning and dorsiflexion of the small toes (Fig. 3c.8). A normal response is plantar flexion of all toes. A positive Babinski sign indicates damage to the corticospinal tract or injury to the spinal cord. ● Oppenheim’s sign is indicative of disease of the pyramidal tract and is performed by sliding the pointed back of the reflex hammer up the crest of the tibia. A positive test elicits a response similar to a positive Babinski sign; the great toe extends whereas the small toes flex and splay. ● Hoffman’s sign is a pathologic reflex elicited by flicking and flexing the distal phalanx of the patient’s middle finger. When the sign is present, there is prompt adduction of the thumb and flexion of the index finger on the ipsilateral side (Fig. 3c.9).
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B
A
C
D
E
F
G
Figure 3c.4 Testing a full array of individual muscles permits the examiner to form an accurate assessment of the affected nerve roots and to assess whether the injury is due to a specific peripheral nerve injury. Comprehensive examination is necessary because of the overlapping neural supply to individual muscles. A: infraspinatus (suprascapular nerve; C5, C6): external rotation of the upper arm at the shoulder. B: deltoid (axillary nerve; C5, C6): abduction of the upper arm. C: biceps brachii (musculocutaneous nerve; C5, C6) flexion of the supinated forearm. D: triceps (radial nerve; C6, C7, C8): extension of the forearm at the elbow. E: bracioradialis (radial nerve; C5, C6): flexion of the forearm at the elbow with the forearm in neutral rotation. F: extensor carpi ulnaris (posterior interosseous nerve; C7, C8): extension and abduction of the hand at the wrist. G: extensor digitorum (posterior interosseous nerve; C7, C8): extension of the fingers at the metacarpophalangeal joints.
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H
I
J
K
L
M
Figure 3c.4 Cont’d H: Flexor carpi radialis (median nerve; C6, C7): flexion and abduction of the hand at the wrist. I: abductor pollicis brevis (median nerve; C8, T1) abduction of the thumb at right angles to the palm. J: flexor digitorum profundus I and II (anterior interosseous nerve; C7, C8): flexion of the distal phalanges of the index and middle fingers. K: third and fourth palmer interossei (ulnar nerve; C8, T1): finger adduction by the patient on the left as the examiner pulls a card. L: dorsal interosseous muscle (ulnar nerve; C8, T1): abduction of the fingers. M: abductor digiti minimi (ulnar nerve; C8, T1): abduction of the little finger.
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An inverted brachioradialis reflex is elicited by tapping the brachioradialis tendon and observing ipsilateral finger flexion. In the finger escape sign, the patient is asked to hold his or her fingers in an extended and adducted position. If the two ulnamost digits drift into abduction and flexion within 30-60 seconds, the patient is deemed to have a positive finger escape sign. In a grip and release test, the patient should be able to rapidly make and release a fist 20 times within 10 seconds.
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A scapulohumeral reflex is elicited by tapping the vertebral border of the scapula at the tip of the scapula spine or the base of the inferior angle. A normal response should be retraction of the scapula by the rhomboid muscles (C4-C5). Absence of retraction is abnormal. A pectoralis reflex is an indication of hyperreflexia. The reflex is present when tapping the pectoralis tendon elicits flexion of the elbow or dorsiflexion of the wrist (Fig. 3c.10).
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Table 3c.4
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Muscle nerve root origins
Upper extremities
Root level tested
Nerve foramen
Pectoralis Biceps Brachioradialis Triceps
C5-T1 C5-C6 C5 C7 (C8)
— C4-C6 C5-C6 C6-C7
Figure 3c.6 The brachioradialis reflex is tested by a direct tap on the muscle tendon.
Figure 3c.5 Biceps reflex: Support the forearm with the patient’s elbow at a right angle and apply light tension to the biceps tendon with your thumb, which should then be hit lightly with the reflex hammer.
Figure 3c.7 The triceps reflex can be more easily elicited if the arm is supported so that the forearm hangs freely or by supporting the arm in the horizontal gravitational plane.
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Specialized physical tests
Figure 3c.8 A positive or extensor plantar response, also known as a Babinski sign. The sole is scratched from the lateral aspect of the heel forward and then medially across the ball of the foot.
The distraction test is an example of a provocative maneuver that can relieve symptoms of spondylosis or radiculopathy. While the patient is sitting or lying down, the palm of the examiner’s dominant hand is placed under the base of the skull and the nondominant hand placed under the chin. The head is gently distracted, increasing the pressure to about 5-7 kg. A positive sign provides symptomatic relief of neck or arm pain. An axial compression test is a provocative maneuver intended to elicit the neck or arm pain a patient may be experiencing intermittently. This is performed by placing up to 5-7 kg of pressure on the top of the head, preferably while the patient is sitting. A positive response precipitates or increases the patient’s symptoms. A distraction test can be performed after this test to attempt to provide some relief. Spurling’s sign is a maneuver to provoke symptom radiation. The patient laterally flexes and extends the neck (rotating the head to the symptomatic side), after which the examiner applies axial compression to the spine. A positive result causes pain or tingling that starts on the ipsilateral side of the neck or shoulder and radiates distal to the elbow (Fig. 3c.11). Spurling’s test has been shown to have a sensitivity of 30% and a specificity of 93% when confirmed with electrodiagnostic studies.17 Pronator reflex (a.k.a., ulnar reflex) is produced by tapping the volar aspect of the distal radius, or alternatively the styloid process of the ulna, with the forearm in a neutral position and the elbow flexed. The normal response is forearm pronation and adduction of the hand. The pronator reflex represents a muscle stretch reflex of the pronator teres that would make it helpful in evaluating C6 and C7 root lesions.14 The Valsalva maneuver is a provocative test that exacerbates arm pain when a patient bears down or coughs. These symptoms result from the increase in intrathecal pressure.
Figure 3c.9 Hoffman’s sign is positive or present if the act of flicking (flexing) the distal phalanx of the index or middle finger (black arrow) elicits a flexion of the thumb (white arrow) and/or other fingers.
Chapter 3c
Figure 3c.10 Position of the examiner’s fingers over the pectoralis tendon to test for a pectoralis reflex.
Tests for thoracic outlet syndrome include maneuvers that are presumed to tighten the thoracic outlet, such as arm hyperabduction, the “elevated arm stress test,” or the Adson test, all of which may provoke the patient’s typical symptoms of pain and/or paresthesia or affect the radial pulse. The Adson test, also called Adson’s maneuver, is performed with the patient in a sitting position. The patient’s hands rest on the thighs, the examiner palpates both radial pulses as the patient rapidly fills his or her lungs by deep inspiration, and, holding his or her breath, hyperextends the neck and turns the head toward the affected side. If the radial pulse on that side is decidedly or completely obliterated, the result is considered positive. In the Allen test, which is sometimes also described in the literature as the Adson test, the arm in which the patient is experiencing symptoms is raised and rotated while the head is turned away from the affected side. If the strength of the pulse is reduced in either of these two tests, it indicates compression of the subclavian artery. All the above are nonspecific tests. If they are positive, however, there may be an indication to perform further studies.
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Evaluating the impact of neck pain
Figure 3c.11 Spurling’s test: Hold the patient’s neck in extension for a few moments. Typical symptoms of brachialgia may be elicited, and if not, the test can be augmented by adding a lateral tilt of the head toward the symptomatic side as shown above. These maneuvers increase the degree of foraminal compression.
EVALUATING THE IMPACT OF NECK PAIN The standard history and physical examination provide objective findings that support subjective complaints to develop an overall assessment of cervical spine disorders. This “standard” examination does not often assess the impact of the disability on a patient’s life quality. Functional scales can be potentially useful to measure the impact of disease on the performance of common daily activities. Defining a standard evaluation for functional disability is difficult, because functional activity can be influenced by many factors independent of symptoms and signs such as age, psychologic ability to cope with disease, and the demands of professional activity.8 Well-validated instruments for evaluating neck dysfunction are widely available (Table 3c.5). For individual patient follow-up evaluation, the Patient-Specific
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Table 3c.5 Standard instruments for evaluating neck dysfunction Medical Outcomes Study 36-Item Short Form Health Survey Neck Disability Index18 Copenhagen Neck Functional Disability Scale12 Northwick Park Neck Pain Questionnaire13 Patient Specific Functional Scale22 Neck Pain and Disability Scale23
Functional Scale has high sensitivity to change and thus represents a good choice for clinical use.16 The MOS 36-Item Short Form Health Survey (SF-36), developed for the Medical Outcomes Study, is an example of a traditional scale for functional assessment.20 This questionnaire has demonstrated an overall usefulness in the general reporting of musculoskeletal ailments; however, it does not report on specific neck pain or disability. The Neck Disability Index is a 10-item questionnaire designed to assess pain-related limitations in activities of daily living. The test is scored as a percentage of maximal pain and disability. The scale is categorized by activity; however, some questions are not pertinent for all patients. The Copenhagen Neck Functional Disability Scale is a 15-item questionnaire requiring yes, no, or occasional as responses. The Northwick Park Neck Pain Questionnaire has nine five-part questions requiring responses of 0-4. The Patient Specific Functional Scale is unique in that it requires the patient to generate a specific list of problems emphasizing the limitations most affecting the patient. The Neck Pain and Disability Scale is a unique 20-item questionnaire in which a visual analog scale is assigned to each discomfort. The 20 items measure intensity of pain and its interference with the vocational, recreational, social, and functional aspects of living and the impact of emotional factors.
SPECIAL TESTS Imaging studies of the spine After the development of a working pathologic and anatomic diagnosis, appropriate imaging studies should be selected to demonstrate and confirm the diagnosis. Routine spinal imaging is not recommended during the first month of symptoms except in the presence of red flags.
Radiographs Plain radiography is the most widely available modality for imaging the cervical spine. The cervical (C) spine series consists of anteroposterior and lateral views to visualize the entire cervical spine and an open-mouth odontoid view to assess the odontoid and C1-C2 joint (Figs. 3c.12 and 3c.13). A swimmer’s view may be required to assess the cervicothoracic junction if the C7-T1 level is obscured by the patient’s shoulders on the lateral cervical radiograph. Lateral flexion and extension radiographs should also be obtained in patients with a history of trauma and patients with extensive degenerative disease. These radiographic views permit assessment of cervical alignment, degenerative changes, assessment of bony architecture in the vertebral bodies, and gross evaluation of the soft tissues. Oblique radiographs can be used to assess encroachment of the neural foramina (Fig. 3c.14). Radiographs should be the first-line diagnostic modality for patients presenting with neck pain when any of the following red flags are present: recent significant trauma or recent mild trauma in patients over 50, prior cancer or recent infection, neck pain worse at night or worse with rest, and history of intravenous drug abuse or corticosteroid use. Radiographs are the least sensitive of the imaging modalities in predicting symptomatology once tumor, trauma, or infection is excluded. A cervical sprain or strain leave no direct radiographic
Figure 3c.12 Lateral and anteroposterior radiographs of the cervical spine of a 34-year-old patient who had a disk herniation at C6-C7 with a clinical radiculopathy. The plain lateral film shows narrowing of the C5-C6 disk space (arrow) with a bony bar between the two vertebrae. That was not appreciated on the MRI. Note also the loss of cervical lordosis. The C5-C6 uncovertebral joint is indicated by an arrow on the anteroposterior radiograph.
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evidence, nor does a herniated disk. Although the presence of degenerative disk disease can be visualized on radiographs, it cannot predict symptoms or disability status.9 As much as 25% of the population has radiographic degenerative changes by age 50, and 75% have degenerative changes by age 70.7 It is the strength of this literature that persuades against the use of routine cervical spine radiographs alone to evaluate disability.
Computed tomography
Figure 3c.13 Open mouth view: A frontal view of the atlantoaxial (C1-C2) joint can be obtained radiographically with the patient’s mouth open as the teeth no longer obscure the direct view. In this example, both right and left C1-C2 facet joints are clearly seen, the dens is clearly visualized equidistant from both facet joints, and a partial view is even obtained of the occipitocervical articulations.
Figure 3c.14 Oblique cervical radiograph: The right-sided neural foramina can be clearly visualized. The black arrow indicates the right C4-C5 intervertebral or neural foramen; the C5 nerve root traverses the foramen. The small osteophytes arising from the right C3-C4 uncovertebral joint (joint of Luschka) are identified by the white arrow. The mild foraminal stenosis can be appreciated when comparing the foraminal dimensions with the normal adjacent foramina.
Computed tomography (CT) is a noninvasive diagnostic modality that provides excellent visualization of the cervical bony anatomy, helps evaluate osseous pathology, and assesses the integrity of the spinal canal. When CTs are supplemented with myelography, one can also evaluate soft tissue structure and impingement of nerve elements. That being said, studies directly comparing magnetic resonance imaging (MRI) and CT myelogram with respect to identifying pathology can yield conflicting results. However, general consensus points to the advantage of the CT myelogram in identifying osseous pathologies such as fractures, osteophytes, and bony foraminal encroachment. MRI studies better demonstrate soft tissue impingement, spinal cord edema, and myelomalacia. The ability of current multiplanar CTs has greatly enhanced the detail of the spine but also escalates the risk of false positivity. Scans can be reconstructed electronically in any desired plane to better visualize pathoanatomy (Fig. 3c.15).
Figure 3c.15 Midsagittal reconstructions of the cervical spine of a 56-year-old man who has an os odontoideum. Note the very short dens (odontoid process) that results in multiplanar atlantoaxial instability. The anterior ring of C1 (arrow) is normally aligned in neutral; there is posterior C1-C2 subluxation in the extended position and marked anterior C1-C2 subluxation in flexion. Note the marked anterior reposition of the C1 ring in flexion resulting in the posterior arch of C1 approaching the C2 body and causing severe spinal stenosis.
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Three-dimensional multiplanar CTs are extremely useful to demonstrate the complex anatomy of fractures and spinal deformity, be it congenital or other (Fig. 3c.16).
Magnetic resonance imaging MRI uses radiofrequency pulses within a strong magnetic field to produce an image without the use of ionizing radiation. MRI is a potentially useful modality for evaluating spinal cord pathology in the presence of brachialgia. MRI is also an excellent imaging modality to assess the soft tissues in the cervical spine and their contribution to compression of the nerves and spinal cord (Figs. 3c.17, 3c.18, and 3c.19). MRI provides excellent visualization of the spinal cord for masses or lesions and cysts as well as for the myelomalacia seen in chronic compression and edema seen in various acute pathologies. Spinal pathology, such as diskitis or local abscess, can be well identified with MRI. However, many of the abnormalities seen on MR images may be incidental, resulting in the potential for over-diagnosis. Nevertheless, in the presence of many of the red flags for pathology, MRI provides indispensable information that can rapidly help confirm or rule out serious clinical problems.
Myelography Myelography uses nonionic contrast injected intradurally to indirectly visualize soft tissues in the canal. Filling defects are an
A
Figure 3c.16 Three-dimensional reconstruction of the cervical spine of a child with a congenital hemivertebra (arrow). There is also a split or butterfly vertebra at C5.
indicator of spinal cord or nerve root compression. Plain myelography is typically enhanced with the addition of a CT. Myelography is a good test for patients in whom spinal root or cord compression is suspected and for patients who have received metallic
B
Figure 3c.17 Cervical magnetic resonance imaging (MRI) of a 26-year-old woman who has a large C6-C7 disk herniation. (A) Sagittal MRI. (B) The axial image through the C6-C7 disk (D) shows the large herniation (H) and the compressed spinal cord (SC).
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A
B Figure 3c.18 Cervical magnetic resonance imaging (MRI) of a 34-year-old woman who had a left C7 radiculopathy. (A) Midsagittal and parasagittal MRIs show the apparently small disk herniation. (B) Axial MRI at C5-C6 demonstrates normal anatomy, whereas at C6-C7 there is a large disk herniation (white arrow) extending into the left neural foramen and compressing the C7 nerve root. Note the normally patent right-sided neural foramen.
implants, which render an MRI ineffective. Myelographic studies also permit acquisition of (dynamic) images of the spinal cord and nerves taken with the neck flexed, extended, laterally tilted, or rotated (Fig. 3c.20). Soft tissue or bony impingement on the neural elements may be demonstrated in positions other than neutral. Note that there are now MRI scanners that also permit a full range of movement and the opportunity to obtain dynamic scans.
Barium swallow Visualizing swallowed radiographic contrast fluoroscopically can demonstrate mechanical compression on the esophagus from anterior osteophytes and differentiate dysphagia from other pathologies.
Bone scans A bone scan uses the technique of scintigraphy (diagnostic technique of recording the distribution and uptake of radioisotopes
injected into various body systems) to gauge the chronicity of a bony lesion such as a fracture, neoplasm, or a focus of osteomyelitis and to monitor disorders affecting bones. Scintigraphy is a very sensitive imaging modality; however, it is not very specific. The bone scan detects the distribution of a radioactive agent injected throughout the venous system. After injection, a scintillation camera detects the radioisotope’s distribution in the body, most importantly its concentration in the skeleton. Areas of increased metabolic activity are imaged as increased isotope uptake on a full body scan.
Electrodiagnostic studies Examination by electrodiagnostic methods is useful to document radiculopathy and to confirm nerve root impingement. These studies additionally facilitate the diagnosis of peripheral
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A
B Figure 3c.19 Cervical magnetic resonance imaging (MRI) of a 51-year-old man who had cervical myelopathy. (A) The sagittal scans show multilevel spinal stenosis. T1- and T2-weighted scans are shown. (B) Axial scans through the disks show central spinal stenosis from C3-C4 to C6C7 with spinal cord compression.
entrapment syndromes and peripheral neuropathy. The tests commonly include needle electromyography, nerve conduction studies, and somatosensory evoked potentials.
Electromyography Measuring the electrical activity of muscle fibers at rest and when active provides diagnostic information on the degenerative or healthy status of muscles and their innervation and distinguishes neurogenic from myopathic disorders. The electromyographic evaluation in chronic cervical radiculopathy shows a
partial denervation pattern that manifests as increased amplitude and a longer duration of the motor unit potential. Fibrillations, or small-amplitude, single muscle fiber potentials, may also be present but are nonspecific and usually seen in the acute stage. Insertional activity from movement of the electrode is normal in electromyographic studies, but if it persists after electrode motion ceases, it is described as prolonged insertional activity and can be a sign of radiculopathy. When these tests are done within the first 2-3 weeks after injury, the results are falsely negative as it takes time to develop denervation.
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Figure 3c.20 Cervical myelogram. (A) Lateral (left) and anteroposterior (right) views of the cervical spine of a 56-year-old man with neck and arm pain and early signs of cervical myelopathy. Compression of the thecal sac is well seen on the lateral view at the C4-C5 and C5-C6 levels when his neck is extended. The anterior-posterior view demonstrates a paucity of contrast at those levels and truncation of the exiting nerve roots. Normal nerve root filling is noted at C6-C7 and distal levels. (B) Postmyelogram axial computed tomography images clearly demonstrate bilateral foraminal stenosis at C4-C5, whereas at C6-C7 the nerve root sleeves can be seen to fill well with the contrast (arrow).
Nerve conduction studies Using nerve conduction studies to evaluate how well nerves transmit electrical signals provides an assessment of the overall condition of both individual nerves and whole nerve structures. Measured electrical parameters are usually the signal amplitude and signal onset latency. These measured values are then compared with established normal parameters to determine the site of a compression. Nerve conduction studies are useful to evaluate acute and chronic peripheral entrapment neuropathies that mimic radiculopathy. Nerve conduction velocity and latency changes are not typically found in cervical radiculopathy unless there is extreme demyelinization of axons. The F-wave response tests electrical conduction through motor roots (Table 3c.6). The F-wave is recorded after maximal stimulation of a motor nerve. The amplitude, shape, and latency should change with each stimulation. Clinical parameters usually evaluated are response time, or latency. Because the F-wave is dependent on the integrity of the entire motor unit, it can assess proximal neuropathies. Another parameter with which to document nerve abnormalities is through the recording and measurement of sensory nerve action potentials. Abnormal sensory nerve action potentials are noted with damage to the nerve from the dorsal root ganglion while they are normal in pure radiculopathy, as the presumed lesion is proximal to the sensory ganglion. In patients with sensory deficit in the hands, recordings of sensory nerve action potentials make a differentiation between lesions of dorsal roots and peripheral nerves possible.
Somatosensory evoked potentials Somatosensory evoked potential recordings can be used to evaluate the integrity of the central nervous system and peripheral sensory neurons. Because most peripheral nerves in the upper extremity carry fibers from multiple roots, somatosensory evoked
potentials are not specific in elucidating spinal root dysfunction but can be useful in determining spinal cord abnormality that affect cord pathways.
Laboratory screening Laboratory studies provide valuable clinical evidence for patients presenting with atypical neck complaints or those suspected of tumor or infection. A complete blood count with differential can help detect a response to infection, blood dyscrasias, and medication side effects. The erythrocyte sedimentation rate and C-reactive protein are categorized as acute phase reactants commonly used in orthopedics to detect evidence of an infection or a connective tissue disorder. Although both indices serve the same primary function, clinicians often use them simultaneously, because the C-reactive protein is quicker to respond to either improvement or worsening of a clinical course. A comprehensive metabolic panel, including Ca+, phosphorus, uric acid, alkaline phosphatase, and acid phosphatase, can help detect metabolic bone disease.
CONCLUSION Evaluation of the cervical spine in workplace injuries requires a multidimensional workup that facilitates, first, ruling out serious pathology before initiating therapy for the work-related injury and, second, evaluation of the patient’s work setting relative to the patient’s recovery process for a rapid and safe return to work activity. The trend in evaluating cervical spine injuries increasingly involves more emphasis on EBM to guide treatment. Using EBM as a guide facilitates a rapid evaluation with concise elimination of red flags for spinal pathology. Returning to work
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Table 3c.6
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Evaluation of the neck
Nerve and main root supply of muscles Spinal roots
Spinal accessory nerve Trapezius C3, C4 Brachial plexus Rhomboids C4, C5 Serratus anterior C5, C6, C7 Pectoralis major Clavicular C5, C6 Sternal C6, C7, C8 Supraspinatus C5, C6 Infraspinatus C5, C6 Latissimus dorsi C6, C7, C8 Teres major C5, C6, C7 Axillary nerve Deltoid C5, C6 Musculocutaneous nerve Biceps C5, C6 Brachialis C5, C6 Radial nerve Long head Triceps Lateral head C6, C7, C8 Medial head Brachioradialis C5, C6 Extensor carpi radialis longus C5, C6 Posterior interosseous nerve Supinator C6, C7 Extensor carpi ulnaris C7, C8 Extensor digitorum C7, C8 Abductor pollicis longus C7, C8 Extensor pollicis longus C7, C8 Extensor pollicis brevis C7, C8 Extensor indicis C7, C8 Median nerve Pronator teres C6, C7 Flexor carpi radialis, C6, C7 Flexor digitorum superficialis C7, C8, T1 Abductor pollicis brevis C8, T1 Flexor pollicis brevis C8, T1 Opponens pollicis C8, T1 Lumbricals I and II C8, T1 Anterior interosseous nerve Flexor digitorum profundus I and II C7, C8 Flexor pollicis longus C7, C8 Ulnar nerve Flexor carpi ulnaris C7, C8, T1 Flexor digitorum profundus III and IV C7, C8 Hypothenar muscles C8, T1 Adductor pollicis C8, T1 Flexor pollicis brevis C8, T1 Palmar interossei C8, T1 Dorsal interossei C8, T1 Lumbricals III and IV C8, T1 Abductor digiti minimi C8, T1
See Figure 4
activity or to normal daily activities, in general, is therapeutic; if necessary, they can be modified to minimize exacerbations and maximize productivity. Once neck pain shifts from acute to subacute or chronic, there exists a comprehensive panel of tests and studies that help to continue to delineate pathology and further guide patient treatment.
REFERENCES 1.
A 2. 3.
B
4.
C
5. 6. 7.
D
8.
E
9. 10. 11.
F G
12. 13. 14. 15. 16.
H I
17. 18. 19. 20.
J
21.
22.
23.
24.
K L M
Adapted from Medical Research Council: Aids to the examination of the peripheral nervous system. London, 1980, Her Majesty’s Stationary Office.
Bigos S, Bowyer OR, Braen GR, Brown K, Deyo R, Haldeman S, et al: Acute low back problems in adults. Rockville, MD, 1994, Agency for Health Care Policy and Research, Public Health Service, U.S. Department of Health and Human Services. Bigos SJ, McKee JE: Data-driven Daubert defendable care code—activity paradigm and reliable data for back problems. Semin Spine Surg 15:68-90, 2003. Cocchiarella L, Andersson GBJ: Guides to the evaluation of permanent impairment. AMA Press, 2004. Co^té P, Cassidy JD, Carroll L: The Saskatchewan Health and Back Pain Survey. The prevalence of neck pain and related disability in Saskatchewan adults. Spine 23:1689-1698, 1998. Demeter S, Anderson G: Disability evaluation. St Louis, MO, 2003, Mosby. Dvorak J, Panjabi MM, Novotny JE, Antinnes JA: In vivo flexion/extension of the normal cervical spine. J Orthop Res 9:828-834, 1991. Friedenberg ZB, Miller WT: Degenerative disc disease of the cervical spine, J Bone Joint Surg Am 45:1171-1178, 1963. Goldberg MS, Scott SC, Mayo NE: A review of the association between cigarette smoking and the development of nonspecific back pain and related outcomes. Spine 25:995-1014, 2000. Gore DR, Sepic SB, Gardner GM: Roentgenographic findings of the cervical spine in asymptomatic people. Spine 11:521-524, 1986. Hill J, Lewis M, Papageorgiou AC, Dziedzic K, Croft P: Predicting persistent neck pain: a 1-year follow-up of a population cohort. Spine 29:1648-1654, 2004. Holland JP, et al: How to critically evaluate the clinical literature on low back problems: the foundation for an evidence-based approach to care. Semin Spine Surg 15:54-67, 2003. Jordan A, et al: The Copenhagen Neck Functional Disability Scale: a study of reliability and validity. J Manip Physiol Ther 21:520-527, 1998. Leak AM, et al: The Northwick Park Neck Pain Questionnaire, devised to measure neck pain and disability. Br J Rheumatol 33:469-474, 1994. Malanga GA, Campagnolo DI: Clarification of the pronator reflex. Am J Phys Med Rehabil 73:338-340, 1994. Medical Research Council: Aids to the examination of the peripheral nervous system. London, 1980, Her Majesty’s Stationary Office. Pietrobon R, Coeytaux RR, Carey TS, Richardson WJ, DeVellis RF: Standard scales for measurement of functional outcome for cervical pain or dysfunction: a systematic review. Spine 27:515-522, 2002. Tong HC, Haig AJ, Yamakawa K: The Spurling test and cervical radiculopathy. Spine 27:156-159, 2002. Vernon H, Mior S: The Neck Disability Index: a study of reliability and validity. J Manip Physiol Ther 14:409-415, 1991. Wagner R, Jagoda A: Spinal cord syndromes. Emerg Med Clin North Am 15:699-711, 1997. Ware JE Jr, Sherbourne CD: The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 30:473-483, 1992. Webb R, Brammah T, Lunt M, Urwin M, Allison T, Symmons D: Prevalence and predictors of intense, chronic, and disabling neck and back pain in the UK general population. Spine 28:1195-1202, 2003. Westaway MD, Stratford PW, Binkley JM: The patient-specific functional scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 27:331-338, 1998. Wheeler AH, Goolkasian P, Baird AC, Darden BV: Development of the Neck Pain and Disability Scale. Item analysis, face, and criterion-related validity. Spine 24:1290-1294, 1999. Woodburne RT, et al: The Netter Collection of Medical Illustrations: Volume 8 Musculoskeletal System. New Jersey, 1997, Novartis Pharmaceutical Corporation.
CHAPTER
3d
Treatment Options for Disorders of the Cervical Spine James N. DeBritz and Sam W. Wiesel
As with any pathophysiologic condition, treatment of neck pain depends on the proper diagnosis. Neck pain has multiple etiologies (Table 3d.1) that may result from trauma as well as from chronic atraumatic conditions. Understanding these etiologies requires detailed knowledge of both the anatomy of the cervical spine and its relationship to neurovascular structures as well as comprehension of the natural history of cervical spondylosis and myelopathy. Diagnosis of neck pain can be more easily accomplished by dividing clinical complaints into several main categories, including axial neck pain, neck pain with an associated radiculopathy, and neck pain with signs and symptoms of myelopathy. Once the proper diagnosis is established, treatment can be directed in a focused and individualized manner. This chapter summarizes some of the most common cervical spine disorders to aid in their diagnosis. The reader is instructed on how a pertinent history, directed physical examination, and diagnostic findings can be used to establish a diagnosis. Treatment options are discussed in detail, and finally a diagnostic and treatment algorithm is presented that integrates the information into a usable format.
ANATOMY A detailed understanding of the osseous and soft tissue structures of the neck is a prerequisite to fully understand the pathophysiology of neck pain and cervical spine disease. Once a pathologic process temporarily or permanently distorts the normal anatomy of the neck, a compensatory response may occur that often presents to the individual as pain. With the exception of C1, each cervical vertebra articulates with the adjacent vertebra through the facet, or zygapophyseal, joints. These are gliding joints characterized by capsules and synovial membranes in addition to ligamentous support. The facet joints are innervated by the dorsal ramus of the associated nerve roots. Axial neck pain can be produced by facet joint injections in asymptomatic individuals, providing evidence that it can originate from the facet joints themselves.2 This information can be used to direct treatment in certain cases, as discussed. The amphiarthrodial joints that join each vertebral body through intervertebral disks play an important role in the pathologic process of the spine as well. Although varying in size depending on the level of the spinal column, all intervertebral disks are identical in their structural organization. The internal portion of the disk is comprised of the nucleus pulposus that is contained around its periphery by the annulus fibrosus.
Table 3d.1 Causes of neck and neck-related pain syndromes Localized neck disorders Osteoarthritis (apophyseal joints, C1-C2-C3 levels most often) Rheumatoid arthritis (atlantoaxial) Juvenile rheumatoid arthritis Sternocleidomastoid tendinitis Acute posterior cervical strain Pharyngeal infections Cervical lymphadenitis Osteomyelitis (staphylococcal, tuberculosis) Meningitis Ankylosing spondylitis Paget disease Torticollis (congential, spasmodic, drug involved, hysterical) Neoplasms (primary or metastatic) Occipital neuralgia (greater and lesser occipital nerves) Diffuse idiopathic skeletal hyperostosis Rheumatic fever (infrequently) Gout (infrequently) Lesions producing neck and shoulder pain Postural disorders Rheumatoid arthritis Fibrositis syndromes Musculoligamentous injuries to the neck and shoulder Osteoarthritis (apophyseal and Luschka) Cervical spondylosis Intervertebral osteoarthritis Thoracic outlet syndromes Nerve injuries (serratus anterior, C3-C4 nerve root, long thoracic nerve) Lesions producing predominantly shoulder pain Rotator cuff tears and tendinitis Calcareous tendinitis Subacromial bursitis Bicipital tendinitis Adhesive capsulitis Reflex sympathetic dystrophy Frozen shoulder syndromes Acromioclavicular secondary osteoarthritis Glenohumeral arthritis Septic arthritis Tumors of the shoulder Lesions producing neck and head pain with radiation Cervical spondylosis Rheumatoid arthritis Intervertebral disk protrusion Osteoarthritis (apophyseal and Luschka joints, intervertebral disk, osteoarthritis) Spinal cord tumors Cervical neurovascular syndromes Cervical rib Scalene muscle Hyperabduction syndrome Rib-clavicle compression From Wiesel SW; Neck pain, ed 2. Charlottesville, VA, 1992, The Michie Company, pp. 60-61.
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Figure 3d.1 Cross-sectional view showing the cervical nerve root, dorsal and ventral primary rami, recurrent meningeal or sinuvertebral nerve, and sympathetic plexus. Note the proximity of the disc space, vertebral artery, and facet joints. (From Rao R: Instr Course Lect 84A(10):1872-1881, 2002.)
Both the nucleus pulposus and the annulus fibrosus share a similar composition and are comprised mainly of water, proteoglycans, and collagen. They differ, however, in their organization and in the type of collagen present. Type II collagen is found in the nucleus pulposus, and type I collagen is present in the annulus. The cervical intervertebral disks are wedge-shaped to accommodate the uncinate processes and the corresponding joints of Luschka, a bony articulation between the vertebral bodies. The blood supply and innervation of the intervertebral disks of the cervical spine have been well defined. Branches of the sympathetic plexus and the ventral nerve root form the sinuvertebral nerve that innervates the intervertebral disk, supplying portions of the annulus, the posterior longitudinal ligament, the periosteum of the vertebral body and pedicle, and the adjacent epidural veins (Fig. 3d.1). In a review of clinical findings of cervical diskography, Grubb and Kelly5 showed a correlation between reliable patterns of pain and each cervical disk. These pain patterns and axial pain patterns produced by facet joint injections are summarized in Figures 3d.2 and 3d.3, respectively. In addition to the major articulations of the cervical spine and their innervations, the soft tissue structures of the cervical spine and the neck play an important role in neck pain. The vertebrae are bound together by many ligaments. The anterior longitudinal ligament and the weaker posterior longitudinal ligament bind the vertebral bodies along the anterior and posterior surfaces, respectively, and run from the skull to the sacrum. The segmental denticulate configuration and intricate association with the intervertebral disk is characteristic of the posterior longitudinal ligament, and a prolapsed nucleus pulposus is most likely to be permitted lateral to these expansions. The ligamentum flavum is a strong elastic ligament that connects the laminae of each of the vertebrae and runs from C2 to the lumbosacral interval. A continuation of the supraspinous ligament, the ligamentum nuchae, runs from C7 to the occiput and along with the interspinous and intertransverse ligaments serves to stabilize further the spinal column architecture.
Muscles in the neck are divided into anterior and posterior groups. Anterior muscles are comprised mainly of the strap muscles and the sternocleidomastoid. The neck musculature forms several distinct layers posteriorly. From dorsal to ventral
Figure 3d.2 Axial pain patterns provoked during discography at each cervical level. A: level between second and third cervical vertebrae; B: level between third and fourth cervical vertebrae; C: level between fourth and fifth cervical vertebrae; D: level between fifth and sixth cervical vertebrae; and E: level between sixth and seventh cervical vetebrae. (From Rao R: Instr Course Lect 84A(10):1872-1881, 2002.)
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Acute herniated disk
will usually reveal only some local tenderness lateral to the bony spine. The loss of motion in individual patients is variable and tends to correspond directly with the intensity of the pain. True muscular spasm, defined as continuous muscular contraction, is rare, except in severe cases of torticollis in which the head is tilted to one side. Because radiographic studies in neck strain are usually normal, plain films are generally not warranted on the first office visit. If the pain persists for more than 2 weeks, however, a radiograph should be obtained to rule out other more serious causes of neck pain such as instability or neoplasia.
Treatment
Figure 3d.3 Composite map of axial pain patterns produced by injections into the facet joints at the second through seventh cervical levels. (From Rao R: Instr Course Lect 84A(10):1872-1881, 2002.)
are the trapezius and levator scapulae, splenius and longissimus, semispinalis, and suboccipital muscles. These muscles assist in scapular rotation (trapezius and levator scapulae) and rotation, flexion, and extension of the neck. Strain of these muscles can also contribute to neck pain.
The prognosis for patients with cervical strain is excellent because the natural history of this disorder is complete resolution of all symptoms over a period of several weeks. Therapy consists primarily of rest and immobilization, often with the use of a soft cervical orthosis. Certain medical interventions such as antiinflammatory agents and/or muscle relaxants may aid in the acute phase of pain management, but they do not appear to alter the natural course of the syndrome. Although no good randomized, prospective, clinical trials have studied their efficacy, trigger point injections do seem empirically to work well. The purpose of a trigger point injection is to decrease inflammation in a specific anatomic area, with apparently superior results the more localized the trigger point. These injections can be repeated at 1- to 3-week intervals.
ACUTE HERNIATED DISK NECK SPRAIN The condition of nonradiating neck pain with a concomitant loss of motion has been referred to incorrectly as neck sprain. Correctly termed cervical strain and one of the most common neck disorders, this often occurs in the absence of a distinct traumatic episode. Most commonly, the pain is located in the middle to lower part of the neck, and although the pain is not secondary to trauma, its onset can be acute. The pain associated with cervical strain is often a dull ache that is exacerbated by movement. In addition, a component of referred pain may be involved. This is not, however, true radicular pain secondary to mechanical compression of a nerve root. The pain is referred generally to other mesenchymal structures derived from a similar sclerotome during the process of embryogenesis. The most common referral patterns include the posterior of the shoulder, the occipital area, the scapular region, and the anterior chest wall, also known as cervical angina pectoris. The source of the pain is most commonly believed to be the ligaments and musculature of the cervical spine.14 As previously illustrated, however, both facet and disk disease can contribute to axial neck pain and should be considered as a source of the inciting complaint (Figs. 3d.2 and 3d.3). Once the precise location, frequency, and quality of the pain have been determined, careful questioning should then address the presence, if any, of subtle long-tract signs, including bowel or bladder dysfunction and gait abnormalities, to avoid missing the diagnosis of myelopathy. Physical examination of the patient
A herniated disk results when the nucleus pulposus protrudes through the fibers of the surrounding annulus fibrosus and occurs around the fourth decade of life while the nucleus pulposus remains gelatinous. Stookey15 and Rothman and Marvel13 described three types of soft disk herniations (Fig. 3d.4), with the posterolateral herniation being the most common due to the anatomy of the posterior longitudinal ligament, as previously mentioned. Herniations occurring posterolaterally produce predominantly motor signs and symptoms. As opposed to those in the lumbar region, disk herniations occurring centrally may cause myelopathy because of the presence of the cord in the cervical region. The most common levels for herniation are at the C6-C7 and C5-C6 levels. Those at the C7-Tl and C3-C4 levels are uncommon, and those at the C2-C3 level are extremely rare. Interestingly, not every disk herniation is symptomatic. The presence and severity of symptoms depend on the individual’s spinal reserve capacity, the presence or absence of associated inflammation, the size of the herniated fragment, and the presence of concomitant disease processes such as uncovertebral joint osteophytes. In general, a herniated disk affects the nerve root of the next lowest cervical level: A C3-C4 disk affects the C4 nerve root, a C4-C5 disk affects the C5 nerve root, and so on. The radicular symptoms then correspond to the involved nerve root. In addition, as previously stated, a herniated disk may cause some long-tract signs because of the presence of the spinal cord at the cervical level.
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Figure 3d.4 Types of soft disk herniations. (From Boden SD, et al: The aging spine: essentials of pathophysiology, diagnosis, and treatment. Philadelphia, 1991, WB Saunders.)
Most patients have symptoms consisting primarily of arm pain. Although it may begin in the neck region, the pain radiates down into the shoulder, arm, forearm, or hand along a clearly defined dermatome. The onset of pain may be gradual, although acute tearing or snapping sensations may occur. The arm pain may vary in intensity from a dull cramping pain in the arm with
use to pain so severe as to preclude use. In addition, attacks of sharp pain may radiate into the hand and fingers with associated paresthesias. Pain severe enough to awaken the patient at night is common. The differential diagnosis of radicular pain must be considered. Pathologies that range from tumors to nerve entrapment syndromes share the common trait of mechanically compressing a nerve root and imitating radicular symptoms. Other neurologic diseases can masquerade as a radicular process, however, and should also be contemplated. Classic differential diagnoses include a Pancoast tumor, which is an apical lung tumor often accompanied by Horner syndrome because of disruption of the sympathetic chain, and thoracic outlet syndrome, which can be diagnosed on physical examination. Physical examination may reveal some decreased motion of the neck that may be so severe as to manifest as frank torticollis. Any maneuver (such as the Valsalva maneuver) that stretches the involved nerve root may recreate the pain pattern. Spurling’s test, in which the neck is extended, may often make the pain worse by further narrowing the involved intravertebral foramina. Additionally, coughing, shoulder abduction, and axial compression tests are often positive in patients with compression radiculopathy. The axial compression test is performed by pressing down on a patient’s head while he or she is either sitting or lying down. A positive finding consists of worsening or reproduction of radicular symptoms. The shoulder abduction relief test is positive if radicular symptoms are decreased when a seated patient elevates one hand above the head with the elbow flexed and the shoulder abducted to 90 degrees. An axial manual traction test is performed with the patient supine. A positive finding consists of a decrease or complete absence of radicular symptoms when 20 to 30 pounds of axial traction is applied. The finding of a neurologic deficit on physical examination greatly aids in the diagnosis, although in the setting of a chronic radiculopathy, the neurologic examination may be normal. Because subjective sensory changes are often difficult to interpret, the neurologic examination must show a diminution of reflexes, motor weakness, or atrophy to be significant. Henderson et al6 found a diminished deep tendon reflex in 71% and a demonstrable motor deficit in 65% of 846 patients with cervical radiculopathy. The specific motor and deep tendon reflex changes noted depend on the cervical nerve root that is compressed by the herniated disk. Because the C3 and C4 nerve roots do not have a uniquely testable reflex or motor innervation, involvement of these roots corresponds to sensory changes in their respective dermatomes. The remaining cervical nerve roots do exhibit testable motor and reflex changes in addition to sensory deficits in their corresponding dermatomes (Table 3d.2). The specific motor innervation of the individual nerve roots allows the examiner to pinpoint the level of disease with good accuracy. Because plain films are most often normal they are nondiagnostic, leaving the clinician to rely on the history and physical examination to arrive at the diagnosis of an acute herniated cervical disk. Occasionally, disk space narrowing is seen at the involved interspace, or oblique films may show foraminal narrowing. Plain films are useful primarily for ruling out other causes of arm and neck pain, such as instability and neoplasia. Other diagnostic tests, such as electromyography (EMG) or myelography, are not useful as screening tests and should be
Chapter 3d
Table 3d.2
Neurology of the upper extremity
Disk
Root
Reflex
Muscles
Sensation
C4-C5
C5
Biceps reflex
C5-C6
C6
C6-C7
C7
Brachioradialis reflex (biceps reflex) Triceps reflex
Deltoid Biceps Wrist extension Biceps
Lateral arm Axillary nerve Lateral forearm Musculocutaneous nerve Middle finger
C7-T1
C8
T1-T2
T1
Wrist flexors Finger extensions Triceps Finger flexion Hand intrinsics Hand intrinsics
Medial forearm Med. Ant. Brach. Cutaneous nerve Medial arm Med. Brach. Cutaneous nerve
used more to confirm diagnoses based on a detailed history and physical examination. In addition, the routine use of computed tomography (CT) or magnetic resonance imaging (MRI) is not warranted. These sensitive studies may reveal herniated disks that are clinically insignificant: In a study of 63 asymptomatic individuals, 10% showed evidence of cervical disk herniation on MRI.1
Treatment The primary mode of treatment for an acute herniated disk is rest and immobilization. A cervical orthosis greatly improves the chance that the patient will remain at rest. The collar must fit properly and hold the head in a neutral to slightly flexed position. If the neck is held in hyperextension, the patient often is uncomfortable and therefore noncompliant in its use. Once the acute pain starts to subside, the patient should be weaned slowly from the orthosis and should likewise increase activity gradually. If the patient complies with the rest and immobilization, the use of analgesics is often not necessary, although a brief course of analgesic medicine may occasionally be required in severe cases. Benzodiazepines and muscle relaxants can act as central nervous system depressants but as such have a limited role in the treatment of acute herniated disk disease. Drug therapy does, however, have an important role in combination with rest and immobilization. Evidence now suggests that herniated disks are capable of eliciting an immune response characterized by the secretion of cytokines such as interleukin-1, interleukin-6, nitric oxide, and prostaglandins, which have multiple effects on tissues, including direct stimulation of nerve ending and sensitization of nociceptors.7 By inhibiting the production pathway of some of these mediators, antiinflammatory medications such as nonsteroidals have a role to play in symptomatic relief. Many such medications can have adverse gastrointestinal side effects but can generally be well tolerated for brief periods. The patient should be educated on these side effects, however, and should be instructed to stop taking the medication immediately if side effects occur. Routine use of oral systemic
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Cervical degenerative disk disease
steroids is not necessary but may prove useful in the more refractory cases. In this case, a tapering dose schedule over a period of 7 days can be used. Injections of local anesthetic and steroid into the cervical epidural space may provide some pain relief. This again is based on the premise that inflammation plays a significant role in the production of radicular symptoms. This procedure, however, requires considerable experience and technical competence and carries with it a risk of complications. Some authors have had limited success with this procedure, but we do not routinely use cervical epidural steroids. The prognosis for patients with an acute herniated cervical disk is generally very good. If patients are compliant with the rest and immobilization program as outlined, most are able to return to work within a period of 1 month, at least under light duty conditions. Indications for surgical intervention in the treatment of an acute herniated disk include persistent radicular pain unresponsive to at least 3 months of conservative therapy, progressive neurologic deficit, static neurologic deficit in the presence of radicular-type pain, and radiographic studies such as CT or MRI with a myelogram confirmatory of clinical signs and symptoms (Fig. 3d.5). Diskectomy for pain relief has been shown to be greater than 90% effective when performed for the proper diagnosis.
CERVICAL DEGENERATIVE DISK DISEASE Cervical degenerative disk disease can produce cervical spondylosis in isolation or in concert with a number of syndromes, including myelopathy, radiculopathy, myeloradiculopathy, and associated visceral or vascular encroachment. Radiculopathy secondary to spondylosis is not discussed separately because it does not significantly differ from radiculopathy secondary to acute herniated disk disease as previously described.
Spondylosis The human cervical spine has a high degree of mobility and flexibility. It has paid the price for this mobility with an almost universal propensity for degenerative change. Cadaveric studies have revealed that nearly everyone will demonstrate some degree of degenerative change in the cervical spine by age 55. Cervical spondylosis is a term used to describe the chronic process of degenerative changes that occur as part of natural aging. These include changes in the vertebral body, intervertebral disk, uncovertebral joints of Luschka, zygapophyseal joints, ligamentum flavum, dura, and soft tissues. The primary cause of cervical spondylosis appears to be agerelated changes that occur in the intervertebral disks, including loss of annulus fibrosus elasticity, desiccation of the nucleus pulposus, and narrowing of the disk space with or without associated disk rupture. Narrowing of the disk space creates excessive motion between vertebral segments, causing secondary changes such as osteophyte formation, facet joint and ligamentum flavum hypertrophy, inflammation of synovial joints, and possibly microfractures. Ultimately, spinal canal and lateral recess stenosis may result. These changes are seen in varying degrees in patients with spondylosis and to a lesser extent in asymptomatic
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JS
C5
A
B
Figure 3d.5 Magnetic resonance images of a 45-year-old man with unilateral C6 radiculopathy. (A) Midsagittal view showing more pathologic anatomy than a parasagittal view of the unaffected side (arrows). (B) Parasagittal view of the affected side showing hard disk pathology (arrow). (From Boden SD, Rothman RH, Wiesel SW, Laws ER, Boden SD: The aging spine: essentials of pathophysiology, diagnosis, and treatment. Philadelphia, 1991, WB Saunders.)
elderly individuals and can produce a variety of clinical signs and symptoms depending on the severity. However, not everyone has clinically symptomatic complaints. Friedenberg and Miller4 showed a lack of correlation between symptoms and degenerative changes seen on plain radiographs of the cervical spine. These changes become clinically significant only when directly related to symptoms. Historically, the typical patient with cervical spondylosis is over 40 years of age and has a complaint of neck ache. Referred pain patterns discussed above include shoulder pain, suboccipital referred pain, occipital headaches, intrascapular pain, anterior chest wall pain, or other nonspecific symptoms such as blurred vision and tinnitus. Physical examination of a patient with cervical spondylosis often reveals little in the way of objective clinical findings. Neurologic findings are generally normal in isolated spondylosis without radiculopathy or myelopathy. Some decrease in motion of the cervical spine may be evident. Point palpation may reveal some tenderness along the midline of the neck and in areas of referred pain. Plain radiographs are obtained primarily to rule out more serious causes of neck pain. Plain films in the anteroposterior, lateral, and oblique planes reveal varying degrees of change, including disk space narrowing, osteophyte formation, foraminal narrowing, facet degeneration, or instability patterns. Once again, these changes do not directly correlate with the presence or severity of clinical symptoms.
Treatment The mainstay of therapy for patients with cervical spondylosis is conservatism. In the presence of acute exacerbation of symptoms
against a background of chronic disease, rest and immobilization are generally beneficial. Aspirin or other nonsteroidal antiinflammatory medications may be helpful also for an acute exacerbation and may be needed on a chronic basis to abate symptoms. As previously described, trigger point injections may be of value also both diagnostically and therapeutically. A soft cervical orthosis may assist in resting and immobilizing the cervical spine. Cervical isometric exercises and changes in the patient’s daily activities such as work habits, sleeping positions, and automobile driving may be useful adjuvant therapies in the treatment of these chronic patients. In this patient population, the use of manipulative techniques and traction protocols should not be performed.
Spondylosis with myelopathy When the previously described degenerative changes of the cervical spine become so severe as to impinge on the spinal cord, a pathologic process termed myelopathy is produced. Spinal cord and nerve root compression produces myeloradiculopathy. Having been described already in detail in relation to acute herniated disk disease, radiculopathy is not addressed here. Those patients with developmental cervical stenosis are more prone to the development of spondylitic myelopathy at a younger age. Etiologic factors in the reduction of canal reserve volume include hypertrophy of the ligamentum flavum, facets, lamina, and dura with redundant annulus fibrosus; foraminal osteophyte compression of radicular vessels; vertebral osteophyte cord compression; tethering of the cord by dentate ligaments; and ossification of the posterior longitudinal ligament or ligamentum flavum.
Chapter 3d
A reduction in volume of the spinal canal can result in direct canal compression and intrinsic or extrinsic ischemia. Edward and LaRocca3 demonstrated that development of myelopathy with spondylosis is almost certain with canal diameters of less than 10 mm. Patients with canals 10-13 mm in diameter are at risk, and those with canals 13-17 mm are myelopathic prone. Myelopathy rarely develops with canal diameters greater than 17 mm. In addition to these static considerations, dynamic changes in the cervical spine may result in myelopathy. Penning and van der Zwaag described the pincer mechanism in 1966. In this mechanism, the spinal cord becomes compressed between the anterosuperior margin of the lamina of the inferior vertebrae and the posteroinferior osteophyte (i.e., hard disk disease) of the superior level. Flexion of the spine causes stretching of the cord over vertebral body osteophytes, with extension possibly resulting in retrolisthesis of one vertebral body on another or buckling of the hypertrophied ligamentum flavum. All these dynamic changes can cause compression of the cord as it passes through the cervical canal. Clinically, most patients are between 40 and 60 years of age when initially seen, with males affected more often. Myelopathy develops in fewer than 5% of patients with cervical spondylosis. Although a history of trauma may occasionally be given, the onset is more often insidious. Acute myelopathy generally reflects a central soft disk herniation producing a high-grade block. The natural history is one of deterioration initially, followed by a plateau in deficit lasting for several months. The exact clinical picture is variable, with a patchy distribution of deficits. This distribution depends on the number of levels involved and the severity of cord impingement at each level. Typically, patients have a gradual onset of numbness and paresthesias with associated weakness and clumsiness. Often, a history of difficulty writing is elicited. Lower extremity symptoms may precede those in the upper extremity and include gait disturbances, peculiar leg sensations, weakness, hyperreflexia, spasticity, and clonus. Upper extremity findings that may initially be unilateral often progress bilaterality. These include hyperreflexia, a brisk Hoffmann sign, and muscle atrophy, particularly of the hand intrinsics. Abnormalities in micturition are seen in approximately one third of cases and connote a more severe cord impingement. Sensory changes are a less reliable sign of myelopathy. Spinothalamic tract signs may be seen with disturbances in pain and temperature sensation in the upper extremities, thorax, or lumbar region. These may be characterized by a stocking-glove distribution. Dorsal column function can be affected with resultant vibratory and proprioceptive disturbances. Impingement on the dorsal division of the nerve root may produce unusual dermatomal sensory changes. In the event of a severe myelopathy, one of several spinal cord syndromes may develop. These include (1) Brown-Sequard syndrome with ipsilateral motor dysfunction, contralateral pain, and temperature dysfunction one to two levels below the motor involvement; (2) central cord syndrome with upper extremity involvement greater than lower extremity involvement; (3) transverse lesion syndrome, which occurs most commonly with involvement of the posterior columns, spinal thalamic tracts, and corticospinal tracts; (4) brachialgia cord syndrome with upper extremity radicular symptoms and long-tract signs; and (5) motor
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Rheumatoid arthritis
system syndrome with corticospinal tract involvement and weakness of both the upper and lower extremities. The differential diagnosis for patients with cervical spondylitic myelopathy includes such disorders as multiple sclerosis, amyotrophic lateral sclerosis, spinal cord tumors, syringomyelia, disk herniation, intracranial lesions, low-pressure hydrocephalus, and subacute combined degeneration. Each of these should be ruled out with appropriate history, physical examination, and diagnostic studies. Plain radiography in these patients generally demonstrates typical degenerative findings, including spinal canal narrowing by prominent posterior osteophytes, variable foraminal narrowing, disk space narrowing, facet joint arthrosis, and instability. MRI can demonstrate structural and parenchymal changes (Fig. 3d.6). The myelogram also is valuable in demonstrating the typical washboard appearance (Fig. 3d.7) with multiple anterior and posterior dye column defects. The posterior defects are produced by facet joint arthrosis and ligamentum flavum buckling.
Treatment Studies looking at the natural history of cervical spondylitic myelopathy are inconsistent and often difficult to compare because of the lack of a universal classification system. Some common factors, however, can be identified. The age at onset and duration of symptoms before the onset of treatment are prognostic factors. Increased age at diagnosis and delay in treatment for longer than 1 year indicates a poor prognosis. Most patients in these series had periods without progression, or plateau phases, interspersed with periods of rapid deterioration. Some patients had a steady progression of the disease with resultant severe disability. Conservative therapy rarely reverses the myelopathy, although in a patient who is a poor surgical candidate because of concomitant medical conditions, conservative measures such as immobilization and rest with a cervical orthosis are viable options. In general, however, management of patients with myelopathy requires surgical decompression of the spinal canal and prevention of further spinal cord impingement and vascular compromise. Progression of the myelopathy after surgical decompression is uncommon. Both anterior and posterior surgical procedures have been reported to lead to improvement in the myelopathy of patients with cervical spondylosis.
RHEUMATOID ARTHRITIS Approximately 2% to 3% of the general population is affected with rheumatoid arthritis. Of these, 86% show radiographic evidence of cervical spine disease, and 60% have clinical signs and symptoms of cervical spine involvement reflecting the erosive inflammatory changes characteristic of this systemic disease process. The clinical variable that is the most consistent indicator of cervical spine involvement is the presence of hand deformities.11 Involvement of the cervical spine consists of three distinct syndromes: atlantoaxial instability, basilar invagination, and subaxial instability. Although atlantoaxial instability is the most common of these syndromes, Ranawat et al12 showed that they tend to occur in combination. They found that 60% of patients had atlantoaxial instability, 16% had basilar invagination, and 60% had subaxial instability. Risk factors for the development
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Figure 3d.6 (A) A sagittal 500-ms TR/17-ms TE image in a patient who sustained a cervical extension injury. Note the disruption of the anterior longitudinal ligament at multiple levels (solid white arrows) and the traumatic disk herniations (open arrows). Pinching occurs at the C5-C6 level (black arrows). (B) A parasagittal 500-ms TR/17-ms TE image shows anterior longitudinal ligamentous disruption (arrows) and prevertebral soft tissue swelling. (C) The midline sagittal 2000-ms TR/30-ms TE 7-mm image demonstrates ligamentous disruption (white arrows), prevertebral edema (e), and pinching at C5-C6 (black arrows). The canal compromise appears more serious on this 7-mm sagittal image, most likely because of a partial volume effect from the lamina laterally. (D) A 2000-ms TR/60-ms TE midline sagittal image shows similar findings, again with prevertebral edema (e), ligamentous disruption (white arrows), and some increase in signal intensity of the spinal cord at the site of compression (black arrows). (E and F) 2000-ms TR/90- and 120-ms TE images with similar findings, although the increased signal intensity within the spinal cord secondary to edema is more obvious on those more T2-weighted scans. The absence of any significant focal areas of decreased signal intensity indicates a relative absence of intramedullary hemorrhage (contusion) and a more favorable prognosis. Despite the initially severe neurologic deficit, this patient eventually recovered significant function. (From Modic MT, Masaryk TJ, Ross JS: Magnetic resonance imaging of the spine, ed 2. St. Louis, 1994, Mosby Year Book.)
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3 4 5 6 B Figure 3d.7 (A) Lateral roentgenogram of a 43-year-old man with complaints of left shoulder pain, gait abnormality, and leg weakness. He had mild spondylotic changes and a congenitally narrow cervical canal (12 mm). (B) Lateral myelogram showing significant extradural defects at C3-C4, C4-C5, and C5-C6. (C) A computed tomography myelogram shows large uncovertebral spurs (arrows) plus soft disk material protruding at C3-C4. (D) Severe spinal cord flattening at C4-C5 from the disk and an osteophytic ridge. (From White AH, Schofferman JA: Spine care, vol. 2. St. Louis, 1995, Mosby Year Book.)
of atlantoaxial instability include prolonged systemic steroid use, long disease duration, older age, and erosive peripheral joint involvement. Patients with cervical spine involvement secondary to rheumatoid arthritis often have occipital neuralgia caused by compression of the greater occipital branch of C2. This gives the typical complaint of headaches when upright that is relieved by
recumbency. Range of motion may be limited, and crepitation or sensations of frank instability may be present, in which case Lhermitte’s sign may be elicited with motion. Neurologic changes can be variable and are often difficult to interpret in rheumatoid patients, who may have severe involvement of the upper and lower extremities. Physical examination should be performed very carefully to rule out upper motor neuron signs, such as
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hyperreflexia and spasticity, and the presence of abnormal reflexes, such as the Babinski and Hoffmann signs. Brainstem involvement by compression of the invaginated dens and/or associated pannus can result in symptoms of vertebrobasilar insufficiency. Other nonspecific findings may include the onset of bowel or bladder incontinence or retention, development of spasticity, and a change in ambulatory status. Evaluation of patients with any of these clinical symptoms should first begin with plain radiographs of the cervical spine. Common findings include osteopenia, facet erosion, disk space narrowing, and subluxation of the lower cervical spine (step ladder). Clinical management and operative indications can be defined by five radiographic measurements: (1) the anterior atlantodens interval, (2) the posterior atlantodens interval, (3) the McGregor line, (4) the Ranawat measurement, and (5) the Redlund-Johnell measurement10 (Fig. 3d.8). Basilar invagination occurs with upward migration of the odontoid process into the foramen magnum with resultant brainstem impingement. Radiographic evaluation includes a measurement of the distance from the tip of the odontoid to beyond the MacGregor line. This is seen on the lateral view of the cervical spine and represents a line drawn from the tip of the hard palate to the posterior base of the foramen magnum. Normally, the dens should not protrude more than 4.5 mm above this line. Protrusion more than 8 mm in females or 9.7 mm in males may be an indication for surgery. A CT may be helpful in determining radiographic landmarks, which tend to become more diffuse in the rheumatoid patient. Subaxial subluxations are also evaluated on dynamic flexion-extension views of the spine. Significant subluxation is defined as translation of one vertebral body on another of 3.5 mm or more or disk space angulation of 11 degrees or more.
Treatment Most of these patients can be managed conservatively despite the fact that cervical spine involvement may develop in a significant number. The mainstay of nonoperative therapy is a hard cervical orthosis (Philadelphia collar), which produces symptomatic relief without actually affecting the atlantoaxial interval. Medical treatment of these patients plays a crucial role in nonoperative management. Medications such as oral steroids, methotrexate, leflunomide, and other disease-modifying antirheumatic drugs are administered under the supervision of a rheumatologist.
Prognostically, these patients tend to do very well with conservative measures, and only a small percentage die of medullary compression from significant atlantoaxial disease. Atlantoaxial disease gradually worsens with time, with only 2% to 14% of patients exhibiting progressive neurologic symptoms. To summarize, surgical intervention should be considered in the presence of (1) more than 3.5 mm of mobile subaxial subluxation on flexion-extension views, (2) atlantoaxial subluxation greater than 8 mm in the presence of spinal cord compression on flexion-extension radiographs, or (3) cranial settling indicative of basilar invagination in the presence of radiographic evidence (MRI) of cord compression. Additionally, in the absence of these findings, the presence of a progressive neurologic deficit is a strong indication for surgical intervention.
HYPEREXTENSION INJURIES (WHIPLASH) Most hyperextension injuries to the cervical spine result from rear-end automobile accidents, which cause acceleration hyperextension injuries in the drivers of the struck cars. Falls and sports injuries contribute to the remainder of the hyperextension injuries. This injury has great economic considerations. The term whiplash injury was introduced by H. E. Crowe in 1928, and since that time it has become a major source of litigation potential. The pathophysiology behind a hyperextension injury involves the soft tissues of the neck region.9 Usually, the driver of the struck automobile is relaxed and unaware of the incipient collision. When struck from behind, the automobile accelerates forward acutely. If no headrest is present, the driver’s head is thrown back and the neck forced into hyperextension as the torso continues onward with the automobile. The sternocleidomastoid, scalenes, and longus coli muscles are extended beyond their elastic limit and are severely stretched or torn. Tears of the longus coli muscles may be associated with a concomitant tear of the sympathetic trunk and result in Homer syndrome. Further hyperextension may result in injury to the larynx or esophagus with subsequent hoarseness or difficulty in swallowing, respectively. Injury to the anterior longitudinal ligament may result in hematoma formation with cervical radiculitis or injury to the intervertebral disk. Furthermore, when the head is thrown backward, the jaw generally lags behind, resulting in injury to the temporomandibular joint as the jaw falls open. When the head recoils forward, the skull may strike the driver’s wheel or windshield, resulting in a head injury.
Figure 3d.8 (A) Measurement of anterior atlantodens interval and posterior atlantodens interval. (B) The Ranawat method for measurement of vertical setting. (C) The Redlund-Johnell method for measurement of vertical setting. (From Monsey RD: J Am Acad Orthop Surg 5:240-248, 1997.)
Chapter 3d
Hyperextension injuries in elderly patients with preexisting cervical spondylosis may acutely compress the spinal cord as the already limited spinal reserve volume is overcome. This cord compression can take the form of a frank paralysis or a central cord syndrome. Patients with a hyperextension injury are generally examined 12 to 24 hours after the initial traumatic event. It is at this point that the patient starts to feel stiffness in the neck and pain at the base of the neck made worse by motion. The pain becomes progressively worse, and eventually the slightest head or neck movement elicits severe pain. The anterior cervical musculature may be tender to palpation, and the patient may have hoarseness, dysphagia, or pain with chewing or opening the mouth. Pain may radiate into both shoulders and arms and upward into the base of the skull. Other pain patterns may include the anterior of the chest, interscapular region, and vertex of the skull. The potential for a closed-head injury even in the absence of visible head trauma should not escape the examiner. Concussion can occur secondary to mechanical deformation during the acceleration-deceleration phase of the injury. This may result in headache, photophobia, mild transient confusion, fatigue, tinnitus, or transient concentration abnormalities. Physical examination must be complete from head to toe so that other associated injuries are not overlooked. The potential for a “chance fracture” of the lumbar spine exists if the patient was wearing a lap seatbelt. The head should be examined for any evidence of a closed-head injury. A unilateral dilated pupil may suggest an injury to the sympathetic chain as it travels along the longus coli muscles with resultant Horner syndrome. It may also indicate significant intracranial pathology in a patient with an altered level of consciousness. Temporomandibular joint tenderness should be assessed as well as suboccipital tenderness, which may indicate that the head struck the top of the seat. A careful and thorough neurologic examination should be performed. Again, particular attention should be paid to elderly patients, who may have baseline spinal stenosis secondary to cervical spondylosis with resultant cord injury or central cord syndrome. If any objective neurologic deficit is identified, further diagnostic tests, including CT and/or MRI, are necessary. CT is better at providing bone detail, whereas MRI is better at demonstrating soft tissue disruption such as intervertebral disk protrusion. In most cases of hyperextension injury, only soft tissue disruption occurs. Plain radiographs should be obtained, however, to rule out unsuspected facet dislocations, facet fractures, odontoid fractures, or spinous process fractures. In most cases, these films are normal or may show some straightening of the cervical spine. As noted, other diagnostic studies such as a head CT should be obtained as the history and physical findings dictate.
Treatment Treatment involves primarily rest and immobilization. Rest consists of a soft cervical orthosis that assists in relieving muscle spasms and prevents quick movements of the head. Collar wear beyond 2 to 4 weeks should not be encouraged, because this may result in weakening of the neck musculature and, in turn,
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development of a long-term psychoneurosis. Strict bed rest may be necessary for 3 to 5 days if the symptoms are severe. Heat in the form of hot soaks or heating pads may be useful. Although narcotics should be avoided, medical therapy in the form of nonnarcotic analgesics, nonsteroidal antiinflammatory medications, and muscle relaxants is helpful. Activity should be restricted according to symptom severity. Characteristically, improvement should occur after 2 weeks of treatment as outlined earlier. If improvement does not occur, an additional 2 weeks of rest and immobilization should be prescribed with the addition of home cervical traction. Lowweight traction consisting of 7 to 10 pounds for 20 to 30 minutes per day generally gives symptomatic improvement. Persistence of symptoms past 4 weeks should alert the physician to search for another etiology. If headaches persist, a CT of the head should be obtained to rule out a closed-head injury. If arm or shoulder pain persists, CT of the spine and/or EMG should be performed. In general, symptoms should be resolving by 6 weeks, although complete resolution may take as long as 1 year.8 Persistence of symptoms beyond 6 weeks of severity equal in intensity to that in the initial period may alert the physician to secondary gain from pending litigation, and compensation neurosis should be suspected. Before assigning this diagnosis, the physician should certainly rule out any significant pathology by a careful history, physical examination, and appropriate diagnostic testing. The physician should not, however, over-treat the patient and encourage a retreat into a life of incapacitating neck pain. The point at which the patient is able to return to the work force depends on both the severity of the hyperextension injury and the type of work involved. Patients performing heavy manual labor may require 3 to 4 weeks of treatment before returning to work, whereas those in less demanding positions may be able to return after only 2 weeks. Limitations on the work performed should consist of no lifting of objects heavier than 50 pounds, no bending, and no prolonged periods of stooping. These restrictions should remain in effect for the first 3 weeks that the patient has returned to work. Depending on the severity of the injury, the prognosis is generally good for complete recovery. Occasionally, a 5% to 10% disability rating is appropriate in an honest patient in whom symptoms persist during hard manual labor.
CERVICAL SPINE TREATMENT ALGORITHM The goal for patients with neck pain is to obtain an accurate diagnosis and administer the correct therapy at the appropriate time. The previously presented clinical entities have been organized into a standardized approach,16 a graphic display of which is presented in the form of an algorithm in Figure 3d.9. The algorithm aids in establishing the proper diagnosis and guides in the delivery of the proper treatment. A summary of treatments categorized by pathology is listed in Table 3d.3. The algorithm begins with evaluation of those patients seen for neck pain with or without associated arm pain. Patients with a history of trauma and associated fractures and/or dislocations are excluded. The first task is a thorough medical history and physical examination to rule out the presence of cervical myelopathy, as discussed earlier.
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Figure 3d.9
Treatment options for disorders of the cervical spine
Cervical spine algorithm. (From Wiesel SW, et al: Neck pain. Charlottesville, VA, 1988, The Michie Company.)
Chapter 3d
Table 3d.3 Treatment options for cervical spine pathology Neck sprain
Spondylosis
Hyperextension/ whiplash Rest Soft orthosis Moist heat Activity modification Physical therapy NSAIDs Rheumatoid arthritis
Rest Soft orthosis Activity modification NSAIDs Muscle relaxants Trigger point injections Acute herniated disk Rest Soft orthosis NSAIDs Oral steroids Epidural injections ↓ Diskectomy
Rest Soft orthosis Activity modification Isometric exercises NSAIDs Trigger point injections Spondylosis with myclopathy Rest/immobilization (nonoperative candidate)
Hard orthosis Steroids/DMARDs
↓ Surgical decompression
↓ Surgical fusion
DMARDS, disease modifying antirheumatic drugs, NSAIDs, nonsteroidal antiinflammatory drugs.
If a myelopathic process is confirmed, surgical intervention should be considered in a timely fashion. The best results are obtained with only one- to two-motor unit involvement and relatively short duration of symptoms. Further studies, including myelography or MRI, should be performed to define precisely the neural compression. Adequate surgical decompression should then be performed. If cervical myelopathy is ruled out, most patients should then be started on a course of conservative management. Regardless of the etiology of the neck pain, all patients are treated equally in this regard. Initially, this nonoperative management consists primarily of immobilization and drug therapy. A well-fitted soft cervical collar should be worn for 24 hours per day to prevent awkward positioning and movements during sleep and while awake. In addition, antiinflammatory medications, analgesics, and muscle relaxants will improve patient comfort. Most patients will symptomatically improve with this protocol within approximately 10 days and should then start to be weaned over the next 2 to 3 weeks. Additionally, their level of activity should be gradually increased, and they should start a series of exercises aimed at strengthening the paravertebral musculature. If the condition remains unimproved, patients should continue full-time collar wear and pharmacologic management. If no significant improvement in symptoms is seen after 3 to 4 weeks, a trigger point injection at the point of maximum tenderness should be considered. This is performed with a combination of 10 mg of corticosteroid and 3 to 5 ml of 1% lidocaine. If this is likewise not successful at 4 to 5 weeks, a trial of home cervical traction may be considered. For patients with neck pain, a total period of 6 weeks of conservative management should be pursued. Most patients respond to this program and return within 2 months to their previous life-styles. If, on the other hand, the symptoms fail to resolve within 6 weeks of conservative therapy, the patients are
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then divided into two groups depending on whether neck or arm pain (brachialgia) is the predominant complaint. For those patients whose main complaint is neck pain and for whom conservative therapy for 6 weeks has failed, plain radiographs, including flexion-extension films, should be obtained. Several of these patients will have evidence of instability, the criteria for which include horizontal translation of one vertebra on another of 3.5 mm or an angular difference of 11 degrees between adjacent vertebrae. Most of these patients do well with nonoperative management consisting of education and bracing, but those who do not may require segmental spinal fusion. A second group of patients have changes characteristic of degenerative disease. Radiographic findings include osteophyte formation, loss of intervertebral disk height, narrowing of the neural foramina, and zygapophyseal joint osteoarthritis. As previously mentioned, degeneration of the cervical spine may be a normal part of the aging process. The difficulty arises in determining which of the degenerative changes are clinically significant. The most significant change has been found to be narrowing of the intervertebral disk height, particularly at C5-C6 and C6-C7. Treatment of these patients consists primarily of antiinflammatory agents, support braces, and trigger point injections. During quiet periods, isometric exercises should be used. Reexamination is necessary to monitor for the development of myelopathic symptoms or signs. Most patients who have normal plain films receive a preliminary diagnosis of neck strain. After failure to improve with conservative therapy, these patients should have a thorough medical evaluation and a bone scan to rule out infection, neoplasia, or inflammatory arthritis as the etiology of the neck pain. If this workup proves negative, they should then undergo psychosocial evaluation and receive treatment, if appropriate, for depression or substance dependence, both of which can frequently be found in patients with neck pain. If the psychosocial findings prove normal, the patient is considered to have a diagnosis of chronic neck pain. Treatment therefore consists of thorough education and support, detoxification from narcotics, and institution of an exercise program. Antidepressant agents may prove to be useful, and frequent reevaluations are necessary to avoid overlooking any serious pathologic process. Other large groups of patients in this algorithm are those in whom arm pain is the predominant symptom. The etiology of this pain may be either direct pressure from a herniated disk or inflammation about a nerve on hypertrophic bone (hard disk disease). Other causes of extrinsic compression of the vascular or nervous structures supplying the upper extremity, including pathologic processes of the chest and/or shoulder region, may imitate brachialgia also and must therefore be ruled out. A thorough history and physical examination, including an Adson test, shoulder examination, and Tinel’s test of the carpal, cubital, and ulnar tunnels, should be performed, with additional appropriate studies possible, based on the results. If an Adson test is positive, vascular studies and EMG should be performed to evaluate causes of thoracic outlet syndrome. Compression of the brachial plexus may occur secondary to vascular structures, cervical ribs, muscular or fibrous bands, or neoplastic processes. Additionally, an apical lung carcinoma can cause brachial plexus compression with or without Horner syndrome from sympathetic chain involvement (Pancoast tumor).
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If plain films of the chest and shoulder are negative and fail to reveal a source of extrinsic compression, EMG studies should be performed. If these indicate peripheral nerve compression, surgical decompression at the site should be performed. In the presence of radicular symptoms, a myelogram or MRI should be performed, and if the results are consistent with the neurologic deficit, history, and physical findings, surgical decompression of the nerve root should be undertaken because conservative treatment results in persistent symptoms. This algorithm is applicable to all patients with nonspecific neck or arm pain and provides a rational approach to the therapeutic and diagnostic sequence of events. The goal of this approach must always be to treat appropriately the etiology of the pain while avoiding unnecessary tests and therapeutic interventions and, most importantly, to minimize the chance of overlooking other serious pathologic processes.
REFERENCES 1.
2. 3. 4. 5. 6.
7.
8.
CONCLUSION
9. 10.
This chapter summarizes some of the major pathologic processes that affect the cervical spine. A detailed description of the anatomy and of the pathophysiology is provided to aid in the understanding of these clinical entities. In addition, the clinical workup of each disease process is discussed, covering the presenting signs and symptoms, corresponding physical examination, and pertinent diagnostic studies. A special emphasis is placed on the treatment of cervical spine disease, which is individualized for each pathologic process. Finally, a treatment algorithm is presented that provides a coherent clinical decision-making process combined with a standardized approach to treatment of cervical spine disease.
11. 12. 13. 14. 15. 16.
Boden SD, McCowin PR, Davis DO, Dina TS, Mark AS, Wiesel S: Abnormal magneticresonance scans of the cervical spine in asymptomatic subjects: a prospective investigation. J Bone Joint Surg 72(8):1178-1184, 1990. Dwyer A, Aprill C, Bogduk N: Cervical zygapophyseal joint pain patterns. I. A study in normal volunteers. Spine 15:453-457, 1990. Edward WC, LaRocca SH: The developmental segmental sagittal diameter in combined cervical and lumbar spondylosis. Spine 10:43-49, 1985. Friedenberg ZB, Miller WT: Degenerative disc disease of the cervical spine. J Bone Joint Surg 45A:1171-1178, 1963. Grubb SA, Kelly CK: Cervical discography: clinical implications of twelve years of experience. Spine 25:1382-1389, 2000. Henderson CM, Hennessy R, Shuey H: Posterolateral foraminotomy for an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. J Neurosurg 13:504-512, 1983. Kang JD, Stefanovic-Racic M, Mcintyre LA, Georgescu HI, Evans CH: Toward a biochemical understanding of human intervertebral disc degeneration and herniation: contributions of nitric oxide, interleukins, prostaglandin E2 and matrix-metallo-proteinases. Spine 22:1065-1073, 1997. McNab I: Acceleration injuries of the cervical spine. J Bone Joint Surg 46A:1797-1799, 1964. McNab I: The whiplash syndrome. Orthop Clin North Am 2:289-403, 1971. Monsey RD: Rheumatoid arthritis of the cervical spine. J Am Acad Orthop Surg 5:240-248, 1997. Oda T, Fujiwara K, Yonenobu K, Azuma B, Ochi T: Natural course of cervical spine lesions in rheumatoid arthritis. Spine 20:1128-1135, 1995. Ranawat CS, O’Leary P, Pellici P, Tsairis P, Marchisello P, Dorr L: Cervical spine fusion in rheumatoid arthritis. J Bone Joint Surg 61A:1003-1010, 1979. Rothman RH, Marvel JP: The acute cervical disc. Clin Orthop 109:59-68, 1975. Rothman RH, Marvel JP: The spine, ed 4. Philadelphia, 1999, WB Saunders. Stookey B: Compression of spinal cord and nerve roots by herniation of nucleus pulposus in the cervical region. Arch Surg 40:417-432, 1940. Wiesel S: Neck pain, ed 2. Charlottesville, VA, 1992, The Michie Company.
CHAPTER
3e
Workplace Adaptation Thomas J. Armstrong
The deviation of neck, shoulder, and elbow postures from neutral positions is associated with adverse health effects such as fatigue and chronic muscle, tendon, and nerve disorders. The effects of these disorders range from minor discomfort and degraded performance to disability. Available data suggest that the time at onset of adverse effects decreases with increasing exertion duration, frequency, and force. This does not mean, however, that some postures can or should be maintained indefinitely without interruption. Also, it does not mean that brief exposures to extreme postures are not desirable. The relationship between certain work activities and adverse health effects is referred to as the “dose-response” relationship (see Chapter 1). The dose-response relationship provides insight into how work can be designed to minimize the risk of possible adverse health effects or to facilitate the return to work of persons in whom an adverse effect may have developed. Unfortunately, sufficient data are not yet available to specify job designs that provide a specific level of risk. For example, it cannot be said how many times a group of workers can exert a horizontal force of 50 N to engage the bit of a powered screwdriver weighing 15 N at an elevation of 1.5 m before unacceptable health effects would develop in a given fraction of them. It is extremely important that the work equipment and procedures be evaluated at all stages of design and implementation. Workplace adaptation entails three basic steps14: 1. Evaluation of the proposed or existing job; 2. Specification of adaptations; 3. Evaluation of adaptations. It may be necessary to repeat one or more of these steps one or more times to achieve a desired level of control.
EVALUATION Evaluation entails documentation of the process, equipment, procedures, and environment and assessment of stressors, including posture, force, duration, and frequency.1,7 The documentation is performed from available job descriptions, time studies, workplace inspections and measurements, equipment specifications, and interviews with workers and supervisors. This information is then used to identify stressful postures and forces necessary to reach, hold, and use work objects and the duration and frequency of these exertions. Tables 3e.1 and 3e.2 and Figures 3e.1 and 3e.2 illustrate evaluation summaries of two jobs: claims processor and assembler. An assessment of stressful postures and forces entails examining each step of the operation for extreme neck, shoulder, and elbow
postures and forces (Fig. 3e.3). These elements should be recorded along with their duration, frequency, and cause. For example, in the claims processor job described in Table 3e.1, extreme reaches to the workers’ side are required 80 times per day to get unfinished files and 80 times per day to put aside finished files. Workers must reach over the files and rotate their forearms to use the keyboard 6 hours per shift. In the assembler job described in Table 3e.2, the workers must reach for parts beside and behind them 2400 times per 8-hour shift; they must elevate their elbow above shoulder height and rotate their forearm 14,400 times per shift, and so forth. The analysis should also include an inspection of infrequent or irregular elements. For example, in the claims processor job (Table 3e.1), 3 of 10 claims are set aside to await additional information that must be retrieved by telephone. In the assembler job (Table 3e.2), 1 of 12 screws is defective and requires additional movements and time to replace. By their very nature, it may be hard to identify irregular elements from existing job descriptions or observations. Often they are identified via worker and supervisor interviews.
SPECIFICATION OF ADAPTATIONS The causes of the physical stressors should be apparent from the work evaluation. The tabulation of stressors and their causes illustrated in Tables 3e.1 and 3e.2 provide a systematic format for developing possible adaptations. This format also provides insight into how the overall stressfulness of the job is affected by the proposed control measures and how one adaptation may affect other stressors. For example, in Table 3e.1 it can be seen that the claims processors are exposed to 2 hours of a stressful shoulder-neck posture per day to hold the phone handset. It can also be seen that a headset or a bracket attached to the handset could reduce this exposure. Yet another adaptation might be passing uncompleted files to another worker who does all the phoning; however, this solution could result in increased keyboard times and other undesirable effects. Reaching for documents is associated with cart location and design. It follows that locating the carts close to the workers’ side and modifying them with a fold-down side would reduce reaching. Because these reaches occur an average of only once every 3 minutes, it can be argued that this work element is by itself unlikely to produce adverse health effects; however, it can also be argued that when combined with other factors, this reaching could result in an adverse effect or could aggravate an existing case. An analysis of the low cost associated with parking the carts close to the workers versus the possible cost of medical treatment and lost work for disabled workers would support locating carts close to the workers. Such an analysis would probably also support a modification of the cart with drop sides. Workplace adaptations may involve modification of ● Work processes; ● Work standards; ● Design of methods; ● Workplace layout; ● Equipment; ● Training.
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Table 3e.1 Sample documentation and analysis of “claims processor” job for identifying and controlling shoulder and neck stressors TITLE Claims processor STANDARD Complete 80 claims per day EQUIPMENT Computer, keyboard, 13-inch color monitor and claim processor software Desk Staple remover Stapler Telephone with handset Adjustable-height chair Carts for holding files METHOD 1. Get file from cart—place on lap in front of keyboard 2. Remove staples 3. Sort documents 4. Perform keystrokes to open file 5. Perform keystrokes to update file 6. Call for information as necessary—3 calls per 10 claims 7. Perform keystrokes to close file 8. Staple documents 9. Stamp and date file 10. Place finished file in cart 11. Note: occasionally claims processor cannot finish file and will set it aside at the front of desk until someone calls back with necessary information MATERIALS Files weighing 5-50 N ENVIRONMENT Inside overhead fluorescent lights with diffusers
Work processes refer to the technologies used for completing the work objectives. In the claims processor example (Table 3e.1), the technologies are keyboards and telephones. Alternative technologies include scanners and electronic mail. In the assembler example (Table 3e.2), the technologies include threaded fasteners; alternative technologies include clips and adhesives. Work standards refer to the quantity and quality of work produced in a given time. In the claims processor example, the standard is 80 claims per 8-hour shift; in the assembler example, the standard is 2400 motor assemblies per 8-hour shift. The work standard is an important factor in how many times per day workers must assume a given posture or exert a given force. Reducing work standards is generally considered an adaptation of last resort; however, it may be shown that the lost productivity is more than offset by the reduced cost of medical treatment and lost work for a disabled worker. Work methods refer to the procedures or sequence of movements used to perform the job. In the assembler example, the method entails getting motors from a bin, placing them on the line, and driving six screws. A methods change to reduce reaching would be to unload one corner of the bin and then rotate it 90 degrees so that the workers are always working from the
WORKER Skilled male and female keyboard operators Fifth percentile female to 95th percentile male stature ERGONOMIC STRESSORS Stressor POSTURE Reaching for unfinished files (80 times per shift) Reaching over file on lap to use keyboard (6 hr/shift) Looking down at file (4 hr/shift) Extending the neck to see monitor through bifocals (2 hr/shift) Reaching to put aside finished files (80 times per shift) Inward forearm rotation and wrist deviation to position hands over keyboard (6 hr/shift) Holding phone between neck and shoulder (2 hr/shift) Proposed Adaptation Provide access for carts so that it can be positioned to minimize reaching Provide adjustable tray to hold file above keyboard Provide corrective lenses that do not require worker to extend neck Investigate variable geometry keyboard to reduce forearm rotation Provide headset for phone Investigate adjustable keyboard holder Investigate wrist rest Provide adjustable monitor holder Stressor FORCE Lifting files weighing up to 50 N from cart to lap (80 times per shift) and from lap to cart (80 times/shift) Proposed Adaptation Provide access for cart so that it can be positioned to minimize reaching Investigate drop side for cart
corner closest to them. A methods change may also require an equipment change and worker training. Workplace layout refers to the position of equipment and work objects in the workplace. In the claims processor example, the workplace layout includes the position in space of the carts with files, the keyboard, the monitor, the phone, and the active file with respect to the worker. Adaptations include repositioning the carts to reduce reaching, adding equipment to allow repositioning of the keyboard, and supplying adjustable document and monitor holders. In the assembly example, adaptations include equipment to reposition the parts bin and adjustment of the suspender so that the tool can be positioned to minimize reaching. Anthropometric data may be used to estimate reach distances.3,11 Average link length proportions can be used with population stature data to estimate vertical, horizontal, and lateral reach limits (Fig. 3e.4). Caution should be used in interpreting reach predictions based on link length data. A reach distance based on average proportions and a given percentile stature may correspond to a different percentile reach. Work locations should be made as adjustable as possible to accommodate individuals and should be tested with user trials.8,12,14 Reach data for U.S. civilian populations are available from U.S. National Health surveys.13
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Table 3e.2 Sample documentation and analysis of “assembler” job for identifying and controlling shoulder and neck stressors TITLE Assembler STANDARD Assemble 2400 motor assemblies per 8-hour shift EQUIPMENT Assembly line (1 m above floor level) Power screwdriver suspended above line Rack and bin for holding parts METHOD 1. Get motor assembly from bin (weight, 40 N) and position on subassembly 2. Get handful of screws with one hand 3. Get screwdriver with other hand 4. Position screw in screwdriver × 6 5. Drive screw (1 of 12 screws is defective and must be backed out and replaced) ENVIRONMENT Inside overhead fluorescent lights with diffusers WORKER Males and females Fifth percentile female to 95th percentile male stature ERGONOMIC STRESSORS Stressor POSTURE Reaching for motor assemblies located to side and behind worker (300 times/hr)
Equipment refers to hardware such as tools to drive fasteners or shape and smooth surfaces, containers, jigs, fixtures for holding parts, and seating to support the worker. A proposed adaptation in the claims processor example includes modification of the cart; adjustable holders for the keyboard, monitor, and files; and a headset for the phone. In the assembly example, equipment changes include an in-line screwdriver with articulating arm, an indexing assembly line, and a turntable for the parts bin. Training entails instructing workers on the hows and whys of arranging and performing their work. In the claims processor example, it should be explained to the workers where they should position the carts and why this is necessary to prevent possible shoulder problems. Follow-up training and evaluations should be performed to determine whether the workers understand and follow the specified procedures. If procedures are not followed, further evaluations should be performed to determine why they are not followed. The design of adaptations should draw on all available resources. Available resources vary from one situation to another, depending on the size and type of industry. Possible resources include ● Job designers, such as engineers, facilities people, and setup people; ● Safety and health personnel, such as doctors, nurses, industrial hygienists, and safety personnel; ● Supervisors;
Reaching for parts located to side and behind worker (300 times/hr) Reaching for screwdriver located overhead (300 times/hr) Driving 1800 screws/hr with pistol-shaped driver requires elevation of elbow and forearm rotation Reaching upstream and downstream to keep up with production line (50% of time, but 90% of time when bad screws are encountered) Proposed Adaptation Position trays close to worker and production line to minimize reaching Unload trays one corner at a time and then rotate tray 90 degrees to minimize reaching Adjust tool suspender to minimize tension and locate tool as close as possible to point of use Investigate use of in-line tool with articulating arm to control torque Investigate indexing production line in which work object stops until released by worker Position work object as close to edge of production line as possible to minimize reaching Investigate quality control program to avoid defective screws that take extra motions to try and to reject Stressor FORCE Lifting motor assemblies weighing 40 N from bin (300 times/hr) Pulling down power tool into work position (300 times/hr) Proposed Adaptation Investigate small hoist or air balancers to facilitate transferring motors to line (See above recommendations for tool suspender)
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Workers or work representatives; Purchasing; Sales and technical representatives from suppliers; Catalogs, brochures, and technical specifications; Scientific papers, books, and magazines.
In general, the team approach is the most effective way to mobilize the resources necessary to develop and implement workplace adaptations. On occasion, however, the problems are conspicuous and the solution is clear so organizing a special team is not merited. Development of adaptation is not an exact process. Consequently, all adaptations should be evaluated to ascertain their effectiveness.
EVALUATION OF ADAPTATIONS Ideally, adaptations should be evaluated in terms of their effects on upper limb disorders. Unfortunately, such evaluations are difficult. Upper limb disorders develop over long periods of time. To determine the effect of a given adaptation on the occurrence of disorders would require identification of a group of several hundred workers, implementation of the adaptation in a random subset of these people, and some kind of comparison adaptation in the others.6 The population would then have to be tracked for
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Figure 3e.1 (A) Illustration of a claims processor job. (B) Major stresses include reaching for documents, holding the telephone, reaching for the keyboard, looking down at documents, and reaching to get and put aside documents. (C) Possible claims processor job interventions include an adjustable document holder (a), adjustable monitor holder (b), adjustable keyboard holder (c), drop-side cart (d), headset for phone (e), and optically correct glasses (f).
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1 or more years. Unfortunately, such studies are extremely difficult and expensive. It is difficult to find large groups in which adaptations can be randomly assigned. Work activities are generally dictated by production schedules that may cause the work population to shrink or swell. In addition, non–health-related factors may cause a turnover in the work population. Although evaluation of health patterns is an important means of identifying workers and jobs that merit further evaluation and assessing an overall program, in most cases it provides only limited feedback about specific adaptations. Adaptations can be evaluated by using the same methods that were used for the initial job evaluations. This analysis should begin as the adaptations are developed on paper and continue through the prototype, pilot testing, and implementation phases.8 In some cases it may be possible to identify and evaluate other jobs at that work site or other work sites where the proposed
adaptations have already been implemented. In other cases it may be necessary to develop prototypes and conduct pilot testing on a small number of the proposed interventions. Worker feedback can be obtained through interviews; however, care should be taken to avoid leading questions.9 The questions should be structured in such a way as to provide guidance on how to enhance the adaptation. For example, one of the proposed adaptations for the assembly job was the use of another tool and locating it to minimize reaching. In this case, workers could be permitted to try several tools and then rank them in order of preference. They could also be asked to try the tools at several locations and rate them on a scale of 0 to 10 where 0 is “too low,” 5 is “just right,” and 10 is “too high.”2,12 Even though these measures do not ensure that future shoulder, neck, or elbow problems will not develop, they do provide a basis for selecting a work configuration that minimizes stress on the worker.
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Figure 3e.2 (A) Work station layout for an assembler. (B) Proposed interventions for the assembler example include using a narrower conveyor to reduce reaching over line “dead space,” using an indexing line so that the worker does not have to “chase” the assemblies, and using a smaller box of parts mounted on a turntable to reduce reaching to the side and behind the worker.
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Neck deviation
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Figure 3e.3 Shoulder and neck stressors include extreme neck, shoulder, and elbow postures and force. (Modified from Armstrong TJ: Hand Clin 553-565, 1986.)
Discomfort patterns can also be used to evaluate work designs before and after they are implemented.4,5,10 Workers are shown pictures of the body and asked to identify and rate areas of discomfort. Discomfort patterns provide information about many parts of the body, as well as those parts likely to be affected by the stress of concern and the proposed adaptation. Often, the variation from within and between workers is considerable, and rigorous statistical conclusions may not be possible.
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The available data are not yet sufficient to develop design specifications that can be used to achieve a given level of risk of neck, shoulder, and elbow disorders; however, the data do provide insight into some of the things that can be done to reduce risk. Control of disorders entails three basic steps: (1) evaluation of
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Figure 3e.4 (A) Average link length proportions can be used with population stature data to estimate vertical, horizontal, and lateral reach limits. (B) The outer arc represents maximum reach without bending. The inner arc represents maximum reach without bending and not flexing the shoulder more than 30 degrees to minimize loads on shoulder tissues.
Chapter 3e
the job to determine the frequency, duration, and cause of extreme reaches and forces; (2) specification of adaptations; and (3) evaluation of the adaptations. It may be necessary to repeat these steps before the desired level of control is achieved. Development of workplace adaptations should be integrated into an ongoing program that includes health surveillance, job surveys, evaluation of affected workers and jobs, medical management, training, and a team approach with participation from all levels of the organization.
5.
6. 7.
8.
9. 10.
REFERENCES
11. 12.
1. Armstrong TJ: Ergonomics and cumulative trauma disorders. Hand Clin 2(3):553-565, 1986. 2. Armstrong TJ, Punnett L, Ketner P: Subjective worker assessments of hand tools used in automobile assembly. Am Ind Hyg Assoc J 51(12):639-645, 1989. 3. Armstrong TJ, et al: Repetitive trauma disorders: job evaluation and design. Hum Factors 28(3):325-336, 1986. 4. Corlett EN, Bishop RP: The ergonomics of spot welders. Appl Ergonom Mar:23-31, 1978.
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References
Harms-Ringdahl K: On assessment of shoulder exercise and load-elicited pain in the cervical spine. Biomechanical analysis of load-EMG-methodological studies of pain provoked by extreme position. Scand J Rehab Med Suppl 14:1-40, 1986. Hennekens CH, Buring JE, Mayrent SL, eds: Epidemiology in medicine. Boston, 1987, Little, Brown. Keyserling WM, Armstrong TJ, Punnett L: Ergonomic job analysis: a structured approach for identifying risk factors associated with overexertion injuries and disorders. Appl Occup Environ Hyg 6(5):353-363, 1991. McClelland I: Product assessment and user trials. In JR Wilson, EN Corlett, eds: Evaluation of human work: a practical ergonomics methodology. New York, 1990, Taylor & Francis, pp. 218-247. McCormick E: Job and task analysis. In G Salvendy, ed: Handbook of industrial engineering. New York, 1982, John Wiley & Sons, pp. 2.4.1-2.4.21. Saldana N, et al: A computerized method for assessment of musculoskeletal discomfort in the workforce: a tool for surveillance. Ergonomics 37(6):1097-1112, 1994. Ulin SS, Armstrong TJ, Radwin RG: Use of computer aided drafting for analysis and control of posture in manual work. Appl Ergonom 21(2):143-151, 1990. Ulin SS, et al: Effect of tool shape and work location on perceived exertion for work on horizontal surfaces. Am Ind Hyg Assoc J 54(7):383-391, 1993. U.S. Department of Health, Education and Welfare: Weight and height of adults 18-74 years of age: United States, 1971-1974. Vital Health Stat 11(211), Hyattsville, MD, 1979, National Center for Health Statistics. Wilson JR: A framework and a context for ergonomics methodology. In JR Wilson, EN Corlett, eds: Evaluation of human work: a practical ergonomics methodology. London, 1990, Taylor & Francis, p. 6.
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Lower Back
4
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4a
Epidemiology: Incidence, Prevalence, and Risk Factors Michele Crites Battié, Tapio Videman, and Douglas Gross
The high prevalence and social and economic impact of low back pain and related disability are well recognized. Low back pain is one of four musculoskeletal conditions specifically targeted by the Bone and Joint Decade (2000-2010) initiative endorsed by the World Health Organization.15,106 Related to the workplace, back injury claims comprise the most expensive category of industrial injuries40,65 and are one of the most common causes of disability in adults under 45 years of age.24,90 In response to this problem, many workplace programs and medical services have been designed to prevent back problems or to minimize their negative consequences. Limited progress has been made, however, in alleviating this common condition and its consequences. When the underlying condition and risk factors for an ailment are understood, prevention and treatment strategies can be rationally based and well directed. In such situations, interventions are likely to be successful. Unfortunately, medical science still lacks information sufficient to guide the prevention and treatment of common back pain. Epidemiologic studies have sought to gain information that could be helpful in guiding these efforts. Epidemiology generally refers to the study of occurrence rates of diseases and especially factors associated with disease occurrence or nonoccurrence. A primary goal of such studies is to obtain information about the disease cause. However, challenges of the most basic nature have hindered epidemiologic studies of back problems.
CHALLENGES FACING EPIDEMIOLOGIC STUDIES OF BACK PAIN PROBLEMS Definition of the problem A central challenge of epidemiologic studies of back pain problems is that in the vast majority of cases the underlying pathology or condition is unknown.29,89 Current clinical examination methods rarely identify the underlying pathology of either acute or recurrent back pain in the absence of major trauma. Despite this reality, there is a tendency to approach back pain as though it were a specific disease or injury state. Miettinen and Caro67 cautioned that epidemiologic studies based solely on a complaint have limited value and that inferences to pathology can be misleading. A complaint is a voluntary behavior and as such can be influenced by a variety of factors other than physical pathology. Further problems encountered in studying any type of pain
include defining and quantifying the pain experience and controlling the effects of individual and cultural factors on pain perception and interpretation. Studies can be complicated also by uncertain reliability in a person’s recall of symptoms and by variations in how researchers define their presence.83 Back pain problems, moreover, are identified through numerous different reporting systems, primarily health surveys and symptom complaints noted in clinical or workplace settings. In North America, for example, in contrast to some other industrialized countries, pain in the workplace becomes known or registered through the filing of an incident report or workers’ compensation claim, and back pain is labeled a “back injury.” Taylor91 described a complex chain of events that leads to the production of industrial insurance and sickness data and makes it clear that the occurrence of back pain incidents registered in the industrial setting cannot be equated to the occurrence of morbidity. Failure to distinguish between studies of different back-related outcomes such as spine pathology, back symptom complaints, industrial injury claims, absenteeism, and long-term disability may lead to misleading generalizations and inaccurate conclusions. Along with different low back pain problem case definitions themselves are the influences and potential biases of the systems through which they are registered. An example of the potentially large effect of health system differences has been provided by Cherkin et al,23 who compared rates of back surgery in 11 developed countries and examined the association between these rates and the number of neurologic and orthopedic surgeons per capita. They found that the rate of back surgery was at least 40% greater in the United States than in any of the other countries investigated and more than four to five times that of England and Scotland. They also found that the rate of back surgery was positively correlated with the number of surgeons per capita (Fig. 4a.1).
Assessment of occupational and other relevant exposures In addition to the challenges posed by definitions, influences, and biases involved in back pain are the methodologic challenges of measuring occupational and other relevant exposures. Occupational exposures that appear frequently on lists of suspected risk factors are vehicular vibration and physical loading involving heavy lifting, bending, twisting, and sustained nonneutral postures. Virtually all inhabitants of developed countries are exposed to these factors during leisure time and work. Exposure is therefore a matter of degree and requires reliable valid methods of measurement. Unfortunately, practical tools to identify and quantify the different exposures in epidemiologic studies of large populations are not fully developed. Further complicating measurement is that for many outcomes such as structural changes of the spine, data are needed on lifetime loading rather than simply on current conditions. Most studies have used the job title as an indicator of occupational loading. This simple method of estimating occupational exposure can be highly inaccurate. The activities and environments of persons with similar job titles can vary substantially, and the loading profiles of workers who remain in one occupation for many years can change greatly. Moreover, most persons
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1.2 Back surgery rate (as compared to the United States)
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hold several different types of jobs during their working years, and their current positions may poorly reflect the physical loading experienced over their working lives. It has also been shown that workers in sedentary jobs tend to engage in more physically loading leisure-time activities than do workers with physically heavy jobs, which can confound attempts to investigate the effects of occupational loading.50 Conceptually, studies designed with the aim of understanding the effects of physical loading on back pain problems should be assessing total loading exposures both within and outside the work environment. Such studies are very seldom performed. Identifying factors associated with risk can give clues about causation, but an understanding of the basis for associations is required to formulate optimal prevention strategies. Leino58 showed that greater exercise activity was associated with fewer back symptom reports and back findings, for example, and Videman et al95 found that former elite athletes had significantly fewer back pain complaints than did nonathletes. If exercise has a protective effect and decreases the risk of back symptoms or spine pathology, then exercise participation could be expected to help prevent back pain. Exercise is also a marker for other healthy life-style behaviors, as well as higher education, higher life satisfaction, and lower occupational physical demands and psychosocial problems,85 all of which can affect back pain reporting. Because physical loading from certain forms of exercise and sports can increase spine pathology, exercise itself may not be directly beneficial and may even have some harmful effects on the spine, so that the apparent benefits are produced instead by factors not associated with exercise. If this were the case and exercise were only a risk indicator, exercise without other changes in life-style would be unlikely to decrease back troubles. Before interventions are planned, it would be important to sort out whether exercise is a beneficial factor or only an indicator of “healthier” life conditions. An odd paradox exists in perceptions of the effects of physical loading at work and at leisure. Physical loading associated with work and with leisure or sport activity share many dimensions
such as frequency, intensity, and duration, yet adaptation to loading, which is an expected result of regular exercise, receives little attention in studies of occupational loading. It is often stated that one reason for disability is that work demands exceed the capacity of the worker. The level of physical demands over prior months, however, is a primary determinant of individual capacity, which should include an adaptation of strength to routine daily work demands, as is the case with exercise training. Yet perhaps the greatest challenge in studies of the association between workplace exposures and back pain incidents and “injury” claims in the developed countries of the world is the injury model commonly used to explain the presence of back pain. Under the injury model, occupational physical loading exposures are believed to be primarily responsible for damage to the back and related pain. This belief naturally leads to greater attribution of symptoms to occupational exposures as workers search for possible causes of their problem. Attributing back pain to work activities may be further enhanced within a workers’ compensation system that offers clear benefits to causation lying with work. These inherent problems to studying back pain reporting in the workplace and its association with work activities greatly complicate, and in some cases may invalidate, study findings and their interpretation.
Causation versus exacerbation Another unresolved issue is that of back pain causation versus exacerbation. Certain occupational exposures, like heavy materials handling in bent and twisted postures, awkward sustained postures, or other forms of physical loading, play a role in the conditions underlying back symptoms that is not well understood. Whether physical loading contributes to the pathology underlying common back pain or simply exacerbates symptoms from an already present underlying condition is a matter of current controversy.
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Incidence and prevalence
high estimates, whereas low back pain that is defined as prolonged or disabling yield estimates toward the lower end of the range. What is clear is that back pain problems are ubiquitous in the general adult population. Work-related low back pain must be viewed against this high baseline. Whether or not a back “injury” has occurred at the workplace, back pain among workers is common, and many believe that their work is to blame. This is a natural and expected consequence of beliefs fostered by the injury model that back pain problems are the result of structural damage caused by physical demands. Further complicating the determination of occurrence rates is the recognition that back pain cannot be neatly categorized as acute or chronic. Instead, it is a fluctuating condition characterized by recurrences or exacerbations of varying severity and pain-free periods.103 In many cases an underlying condition appears to influence propensity for symptoms and occasional flare-ups loosely related to a variety of individual and environmental factors. This recurrent variable nature of back pain within individuals commonly leads to misclassification of the presence or absence of contributing conditions and influences occurrence rates and observed associations with suspected risk factors. Also important to the incidence and prevalence of low back pain reporting in the workplace are significant overall trends in industrial injury reporting. The mix of industrial injury claims has changed dramatically over past decades, with increasing dominance of back and other ill-defined musculoskeletal complaints over traumatic accident-induced injuries. Ostry78 clearly depicted this trend in a summary of short-term work loss claims from 1952 to 1996 in British Columbia. He presented the relative number of claims attributable to strains, which includes the categories of back strain, overexertion, and other strains and sprains, as compared with claims for impact (falls, slips, blows from objects, and so forth) and other miscellaneous injuries (Fig. 4a.2). During the years studied, a dramatic decline occurred in the proportion
Some evidence suggests that routine physical loading exposures, such as seen in occupations with heavy physical demands, may have a modest role in influencing underlying pathology and a role in exacerbating such pathology. Videman et al99 controlled for spine pathology and found that a history of back symptoms was correlated with physical loading. This finding supports the belief that loading exacerbates symptoms from existing conditions. The same study found that annular tears were more commonly found in subjects who engaged in occupations involving heavy physical loading, which suggests that it can lead also to increased risk of some structural failures. The role of occupational loading in degenerative changes and pathology, however, appears to be considerably less than previously thought.
INCIDENCE AND PREVALENCE As mentioned previously, there are no standard definitions for determining the presence or absence of back pain problems in the general population; instead, various definitions and methods for collecting such data are used. This leads to wide variations in prevalence and incidence estimates. A systematic review of the scientific literature from 1966 to 1998 presenting data on the prevalence of low back pain yielded point prevalence estimates from 12% to 33%, 1-year prevalence estimates from 22% to 65%, and lifetime prevalence estimates from 11% to 84%.102 Another review of the literature on low back pain prevalence estimated the point prevalence specifically in North America at 5.6%, but similarly broad ranges were noted in prevalence estimates as in the aforementioned review.63 These wide ranges are influenced by many factors, not the least of which is the definition of low back pain used in terms of pain severity, duration, and associated disability. Responses to such questions as “Have you ever had low back pain?” result in
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of impact injuries from over 80% of all injury claims in the late 1960s to slightly over 30% in 1996. Conversely, claims for strains rose from approximately 10% of all injury claims to 50%. Overall, in recent years occupational injury and illness rates in North America have shown a downward trend. The U.S. Survey of Occupational Injuries and Illnesses, generated by employer workplace incident logs, revealed a decline in nonfatal injuries in private industry from a high of 9.2 cases per 100 full-time workers in 1978 and 1979 to a low of 6.6 cases per 100 full-time workers in 1997, the last year for which data were analyzed.30 Similar trends were observed in Ontario, Canada from 1993 to 1998, where a 29% reduction in lost-time compensation claims was seen.72 The reasons for the decline are unclear. It has been speculated that it could be due to more effective prevention or treatment programs that influenced incidence or time loss, greater reluctance by employees or employers to report incidents, or changes in criteria for the diagnosing of some of these conditions by health care providers.12 The reduction may be due also to shifts in dominant industries and more generalized economic, social, cultural, or legislative trends that have affected injury reporting. Of the approximately 5.7 million injuries reported in 1997, representing 93% of all injuries and illnesses documented in employer records, however, the category of “strains, sprains, and tears” accounted for a disproportionately large share of cases with days away from work. Nearly half of these involved the back.30 Looking specifically at low back pain claims and associated disability and costs in North America, a downward trend has been noted since the late 1980s. Using a large sample of claims from the privately insured U.S. workers’ compensation market, Hashemi et al44 examined length of disability for low back pain claims and associated costs during the period of 1988 to 1996. As in previous studies,88 the distribution in terms of disability and costs was highly skewed. Depending on the year, 4.6-8.8% of claims with a disability duration lasting over 1 year accounted for 78-90% of the total disability days and 65-85% of the claims costs. Over the study period from 1988 to 1996, the mean length of disability decreased by 61%, whereas the mean and median cost per claim decreased by 41% and 20% respectively, suggesting that the most influential changes occurred through a reduction in long-term disability claims. Concurrently, a 34% decrease in the annual low back pain claim rate was reported in the United States from Bureau of Labor and Statistics data between 1987 and 1995, although it was noted that the trend was not monotonic. There was a sharper decrease in costs, one of 58%. Yet in 1995 the rate of low back claims in the United States was 1.8 per 100 employees, still representing a major health problem in the workers’ compensation system.71 These changes in back incident and claims rates seem to be a part of the larger trend for declines in all work-related injury and illness reporting. In Washington state, for example, there was a decrease of approximately 24% in the incidence rate of back claims from 1989 to 1996 and a similar decrease of 27% in all claims during the same period.44 Although a significant variation exists among industry sectors, Yamamoto107 reported a trend for a decline in the number of recognized occupational low back pain cases in Japan as well. In a large study of over 730,000 claims initiated from 45 U.S. states in 1989, available through a Liberty Mutual Insurance Company database, back-related claims constituted 16% of all
claims and 33% of all costs.104 Medical costs were overshadowed by indemnity costs that represented nearly 66% of total claims costs. These figures are similar to those from other studies reported from the United States at around the same time88 and somewhat lower than figures from Australia from the early 1990s.77
RISK FACTOR ASSOCIATIONS Structural pathology and tissue injury Back pain is commonly used as a synonym for spinal illness or, in the case of the workplace, spinal injury, although it is obvious that they are not the same and that the causal factors for the underlying pathology and reporting of back pain can be different. Some pain could originate from a metabolic disturbance such as muscle fatigue, which could be expected to recover fully without remaining identifiable pathology. Physical loading exceeding the tolerance of a structure produces a structural pathology with pain. This true injury and other factors, such as severe degeneration or infections, could lead to irreversible pathologic conditions, the symptoms of which could be triggered by routine or “physiologic loading.” This could be one explanation for the result that previous history of back pain is one of the most consistent predictors of later back pain.13 Commonly used “disability” scores estimate avoidance of defined functions due to back pain (the modifying effect of reported physical loading on pain). The correlations of underlying illness with sickness absenteeism, permanent disability pension, and use of health care due to back pain, however, are generally low.
Clinical relevance of spine pathology Studies of factors associated with the pathology of spinal structures have received relatively little attention, although the disk has been commonly thought to be responsible for most back symptoms and has been a primary target for diagnostic and therapeutic interventions related to spinal disorders. Knowledge of the macropathoanatomy and micropathoanatomy of the spine is consequently limited with respect to painful conditions. For example, we do not know the clinical value of osteophytes, disk space narrowing, disk bulges, end-plate changes, intervertebral foramina and spinal canal anthropometry, or facet joint degeneration. In the past decade even our understanding of the clinical relevance of disk herniation and annular ruptures has changed. Some studies have shown an association between disk pathology and back pain reporting, but degenerative findings are also common among asymptomatic subjects.14,16,99,105 Certain mechanisms have been suggested to explain associations between disk pathology and back pain. Full annular ruptures reaching innervated disk structures could be associated with back pain through several mechanisms. Annular tearing can lead to disk herniation with nerve compression, has been shown to produce pain by biochemical effects, and is the pathology allowing nerve ingrowth into the disk.5,33,34,76 Disk degeneration could make the disk mechanically incompetent, allowing abnormal motion between neighboring disks and leading to pain in innervated structures in the functional unit.73 Several other structures in the spine, such
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as muscles and tendon insertions, are possible sources of back pain. The condition underlying most back pain remains unknown, however, and the structural changes mentioned are currently of little clinical value.
Hereditary influences on disk degeneration There has been a dramatic paradigm shift over the past decade with respect to determinants of disk degeneration and pathology. This shift is clearly depicted by the contrasting conclusions of two reviews on the topic of “degenerative disk disease” written a decade apart. After an extensive review of the literature in 1992, Frymoyer35 concluded, “Among the factors associated with its occurrence are age, gender, occupation, cigarette smoking, and exposure to vehicular vibration. The contribution of other factors such as height, weight, and genetics is less certain.” A decade later in 2002, Ala-Kokko1 concluded, “Even though several environmental and constitutional risk factors have been implicated in this disease, their effects are relatively minor, and recent family and twin studies have suggested that sciatica, disk herniation and disk degeneration may be explained to a large degree by genetic factors.” Traditionally, degeneration of the spine has been viewed as an outcome of the accumulation of lifetime mechanical insults and injuries imposed on normal aging changes. During the 1990s the dominant effect of hereditary factors became clear, but the traditional view still maintains wide support.1,35 The traditional view, however, makes it difficult to explain the very high concordance in degenerative signs observed in lumbar spine magnetic resonance images in monozygotic twin pairs highly discordant for occupational exposures. In a study of determinants of disk degeneration in 115 pairs of identical twins, occupational physical loading explained from 0 to 7% of the variance in disk degeneration in the lumbar spine and age (ranging from 35 to 70 years) below 10%, whereas the combined effect of genes and shared environmental factors accounted for 30-60% of the total variance in disk degeneration.11 The observed significant individual differences at all ages in the degree of disk degeneration support a conclusion that there are crucial individual differences in predisposition to this problem. Using a classic twin study, Sambrook et al84 reported that heritability estimates explained 74% of the variance of the “overall score of disk degeneration” of the lumbar spine. The results from these twin studies suggest that heredity has a dominant role in disk degeneration compared with the importance of all commonly suspected adulthood exposures. The role of genetics has been confirmed additionally in several studies identifying gene forms associated with disk degeneration.4,51-53,97 It is likely that more genes associated with disk degeneration and symptoms will be found over the coming years, enhancing our chances to investigate so-called gene-environment interactions and leading to better understanding of the etiopathogenesis of disk degeneration.
Occupational and other influences on disk degeneration Most epidemiologic studies in the area of common spinal disorders have been of back symptoms, and the literature related to the epidemiology of spine pathology is limited. In an exceptional study of musculoskeletal findings based on 1000 consecutive autopsies, the occurrence rate of “spondylitis deformans”
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increased linearly from 0 to 72% between the ages of 39 and 70 years.45 Although these findings relate to people and work conditions around the turn of the century and the definition of “spondylosis” is not clearly stated, the rapid linear increase is notable. In a review article, Miller et al68 reported a similar increase in grades II to III disk degeneration from 0% at age 20 to about 90% at age 70 years. The authors also concluded that radiographic data are corroborated by macroscopic findings. Frymoyer et al37 compared the radiographs of three groups of men between the ages of 18 and 55 years: men with no history of back pain, men with moderate back pain, and men with severe back pain. In these three groups the frequency of Schmorl’s nodes, claw spurs, disk heights at the L3-L4 and LS-S1 levels, the disk vacuum sign, and transitional vertebrae were similar. The radiographic findings that differed in the three groups were traction spurs and/or disk space narrowing between L4 and L5, but these findings did not correlate with occupation, occupational lifting, or whole-body vibration. Specifically with respect to driving and associated whole-body vibration, findings have been somewhat conflicting, but the current weight of evidence suggests no notable effect on disk degenerative findings. Arguably the most well-controlled study to date on the subject did not find lumbar disk degeneration or pathology to be associated with lifetime driving.9 Riihimaki82 found that concrete reinforcement workers had a relative risk of 1.8 for disk “space narrowing as compared with house painters and a relative risk of 1.6 for ‘spondylophytes’.” They concluded that heavy physical work enhanced the degenerative process in the lumbar spine. An autopsy study of 86 subjects by Videman et al99 showed that occupations that involved sitting, standing, and walking without heavy physical loading were associated with the least degeneration. Workers with heavy physical loading had the highest incidence of annular ruptures, and sedentary work was associated with the highest degree of general disk degeneration. Studies using magnetic resonance imaging reported risks of 0.35 and 0.57 at the age of 20 years among asymptomatic and symptomatic subjects and 0.09 among asymptomatic subjects at the age of 11 years.79,86 In addition, Boos et al17 demonstrated histologically verified annular tears in a group of subjects aged 11-16 years and endplate cartilage pathology among 3 to 10 year olds. The adjusted disk signal intensity reflecting the water content of nucleus pulposus has been shown to change rapidly in early years between the ages of 9 and 77 years.68,98 Obviously, degeneration begins before individuals are exposed to workplace factors. All adults have disk degeneration, and only the degree of spine degeneration varies. That degenerative changes are present already in childhood further underlines our limited understanding of the etiology of spinal degeneration. Many researchers have studied spine degeneration based on radiography, which provides good measures of disk space narrowing and annular insertions to vertebrae (osteophytes), although its overall relevance for the intervertebral disk is not clear. A study of more than 15,000 adults did not show that heavy work was associated with spine degeneration in radiographs, although men had more degenerative signs than women. Lawrence56 reported that lumbar disk degeneration was most common in persons with physically heavy tasks compared with more sedentary workers, but only in men. Hult49 showed the
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prevalence of disk degeneration to be nearly 100% by age 59 in workers with heavy physical work, and similar degenerative findings were noted about 10 years later among those engaged in light work. Interestingly, however, important differences between the groups with heavy and light physical work were observed at baseline, and firm conclusions about the relative role of occupational physical loading on disk degeneration cannot be made. Conflicting findings in the scientific literature and failure to identify a dose-response relationship have not led to a convincing demonstration of the primacy of workplace factors in causing anatomic abnormalities.10,96
SUMMARY In principle, the determinants of all degenerative processes are similar. A function of individual constitutional factors, including genetics, they are modified by behaviors and extrinsic exposures. As studies progress in the area of spinal degeneration and structural variation, genetic influences appear to play a dominant role. Occupational exposures, representing different loading conditions, alone appear to have only modest affects on disk degeneration and pathology. Virtually all humans are exposed to the types of physical activities that have been suspected of accelerating lumbar degeneration during either work or leisure, with exposure being simply a matter of degree. Their influences vary due to recovery times, adaptation level, and stage of degeneration, among other factors. It is likely also that there are as yet unknown factors contributing to degeneration. In the end, both environmental and constitutional factors have some role in all degeneration, and only their relative magnitudes vary.21
Work-related back pain reporting Industrial back “injury” incident reports and claims filing involve specific definitions of back problems to be distinguished from structural pathology, symptom complaints solicited on surveys, or problems identified through health care visits. Most developed countries have systems for filing complaints of work-related injuries and illnesses with their own sets of rules, costs, and benefits. In discussing such systems in the United States, Hadler41 emphasized that filing a complaint forces the person to conform to the workers’ compensation paradigm. He stated, “By definition, work task description is causal. By inference, the illness is a manifestation of major structural damage.” As we have discussed, both of these assumptions are highly controversial. We found 13 prospective longitudinal studies that investigated predictors of industrial back pain reports.13,19,22,31,38,46,48,55,69,70,81,83,93 Early studies focused largely on physical factors, whereas more recent research attempted to account for other factors influencing back pain reports. Chaffin and Park22 performed some of the earliest prospective research in this area. In the early 1970s, they conducted a study of back incident reports in 411 men and women who engaged in manual lifting in their work at an electronics manufacturing company. The study focused on the effects of occupational lifting and mismatches between individual strength and job requirements. They reported an association between low back pain and jobs
with higher lifting strength requirements. They also found a higher incidence of back pain reporting in persons who demonstrated less strength on isometric strength testing than that deemed necessary to meet job demands, as compared with those whose strength met or exceeded demands, although the association was not statistically significant. Limitations of this study were that only 25 low back incidents were reported and controls for other factors influencing back pain reports were not undertaken. Cady et al19 later reported on physical fitness as an indicator of risk in 1652 firefighters over a 3-year period. Fitness was defined by a composite score based on aerobic capacity, strength, and flexibility measures. They found that firefighters with low “fitness” levels were about nine times more likely to report a back injury than those in the “most fit” group. The few injuries reported among the highly fit were the most serious, however, in terms of cost. Again, the effects of age, previous back pain, and other potentially confounding factors were not reported, making interpretation of the results difficult. Isokinetic lifting strength was investigated as a predictor of low back injury claims among nurses in a study by Mostardi et al,70 who concluded that lifting strength was a poor predictor of subsequent back symptoms and injury reports. Another prospective study of back injury reports in nurses reported by Ready et al81 reached similar conclusions about isometric lifting strength and other general fitness parameters. The factors that discriminated most between the nurses who did and did not report subsequent back injuries were previous receipt of compensation, smoking status, and poorer job satisfaction. In the Boeing study, a prospective cohort study of industrial back pain complaints in 3020 aircraft manufacturing workers, isometric lifting strength, maximal aerobic capacity, and lumbar range of motion were among the factors that were not associated with subsequent complaints. Other than having had current or recent back problems at the onset of the study, the strongest predictors of future back pain reports were negative perceptions of the workplace, including low job task enjoyment and social support and emotional distress.13 The only factor from the baseline physical examination that was strongly associated with future reporting was back pain elicited on straight leg raise testing, which probably represents another aspect of recent or current back problems also known to influence future risk.7 Yet in multivariable analysis, considering the numerous suspected risk factors under investigation, less than 10% of the variance in the reporting of work-related back pain was explained. The study findings underline the multifaceted nature of back pain reporting in industry and the limited predictive ability of most suspected risk factors. A later extension of the Boeing study looked specifically at back incident reports that resulted in the formal filing of industrial insurance claims. Lower job satisfaction and a poorer employee appraisal rating by the employee’s immediate supervisor were associated with back injury claims. Given the findings of the earlier analysis of back incident reports, this result was not surprising. A more notable finding of the later analysis was that these psychosocial factors were similarly associated with non–back injury claims as well. It would appear that certain psychosocial factors may predispose to the filing of injury claims, but the study did not provide evidence of significant differences between those who filed back injury claims and those who filed other types of injury claims.9 Such findings caution against
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stereotyping persons who file back injury claims as being distinctly different from those filing other injury claims with respect to “preinjury” psychosocial factors. As Leavitt57 stated, “The unfortunate problem is that stereotypes have consequences. Doubts raised by labels often shape evaluation and treatment of industrial workers in problematic ways, to the extent that their integrity and status as patients is challenged.” Since the Boeing study, researchers have continued to search for risk indicators and have expanded the investigation more fully into multiple domains including the physical, social, and psychologic. Numerous potential risk indicators, including exposure to repetitive trunk rotation, low supervisor support, and lack of control over work duties, have been reported. Many of these indicators have been found through exploratory studies, however, and few results have been taken to the next crucial stage of confirmation or replication in a separate cohort. Exploratory investigations have many inherent risks, including observing statistically significant associations by chance that do not actually exist or are biologically implausible.2 More trust can be placed in findings that have been validated through confirmation studies. Although confirmation studies in this area of research are rare, six indicators have been reported in multiple studies to increase the probability of future back pain reports: low job satisfaction,13,48,55,81,83 heavy physical work requirements,31,38,55,69 low social support at work,13,93 previous low work performance ratings,13,55,93 smoking status,8,81,93 and previous history of low back problems.13,83,93 The magnitudes of each of these associations have been relatively low, with odds or rate ratios typically ranging between 1.5 and 3.0 and accompanied by confidence intervals approaching 1.0. It is clear also that individual worker strength levels do not predict future injury.7,69,70,81 Although the above results have been substantiated in multiple investigations, it is unknown whether the associations observed indicate causal relationships, especially regarding the psychosocial and physical indicators. Although theories abound for how both psychosocial and physical stressors could result in reports of back pain, it is possible that indicators from within one domain influence indicators within the other. It has been theorized that individuals with higher workloads may be more likely to have lower job satisfaction.27 Alternatively, individuals under psychologic stress may be exposed to altered biomechanical forces through changes in posture or movement strategies.66 Further research is required to clarify the potential interactions arising between physical and psychosocial indicators. One study in which interaction effects between predictor variables were studied found independent effects of both psychosocial and physical variables, possibly indicative of unique effects for each.55 Although some work has been done to elucidate which factors are associated with industrial back pain reporting, the practical value of predictive models or preemployment screening for identifying specifically who will or will not experience or report symptoms is questionable. The magnitude of associations for individual predictor variables and overall predictive accuracy of created models has been relatively low, and practical difficulties arise when attempting to apply results from large samples to individual workers. Additionally, attempts at prevention based on knowledge of suspected risk factors such as workplace ergonomic modification have been largely unsuccessful.26,64,94 In fact, authors of one systematic review evaluating the effectiveness
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of multiple prevention strategies stated, “The results concerning prevention for subjects not seeking medical care are sobering. Only exercises provided sufficient evidence to conclude that they are an effective preventive intervention.”60
Subsequent disability Evidence suggests that back symptoms have always been present to some degree among humans and likely always will be. Episodes of these symptoms are, however, typically manageable and relatively short-lived. A systematic review of the prognosis of acute (<3 weeks) low back pain indicated that the prognosis of this condition is largely positive.80 Although back pain is a recurring phenomenon, most individuals recover from episodes quickly and experience little disability. The vast majority (68-86%) of individuals off work due to back pain returns to work within 1 month, and further improvements are seen for up to 3 months. In the small minority experiencing pain and disability for 3 consecutive months, however, little further improvement in important clinical outcomes is seen. Although some chronic back pain sufferers are able to cope with their pain and continue to work, a portion remains off work and experiences extended time loss.20 Within the workplace, it has been reported that approximately 10% of back injury claimants with extended work loss account for approximately 10% of back-related industrial insurance costs.88 Long-term disability is therefore the outcome that poses the greatest threat to the individual and the greatest cost to society. Disability is typically represented in the work environment as absenteeism. An examination of factors associated with illness absenteeism led Backenheimer6 to conclude that “absence behavior is, in considerable measure, a cultural and social phenomenon.” He claimed also that “a biological frame of reference is too narrow to explain the condition of being ill.” There is now a large body of evidence that these notions apply also to absenteeism and disability from back problems. Great variability is observed in back pain disability and work loss durations among nations and disability systems that would not be expected if disability were purely a biologic phenomenon.47,100 Long-term back pain disability is a relatively new phenomenon in the history of Western civilization, and its dramatic growth since World War II suggests that factors other than physical pathology are influencing its development. This is not to say that many working people do not genuinely experience back pain or that severe symptoms do not cause physical limitations of some duration. On the contrary, numerous health surveys indicate that back symptoms are extremely common in both developed and Third World countries.3,75,101 What appears to have changed in many societies, however, is the public perception of back pain as an “injury” or medical problem and its effect on work life in terms of disability. One striking example of the tremendous growth in back pain disability seen in many of the developed countries comes from the U.S. Social Security Disability Insurance System, where from 1957 to 1976 the incidence of disability awards increased by approximately 270%, a rate 14 times that of the population growth (Fig. 4a.3).87 Similarly striking increases in the incidence of disability awards have occurred in Finland, Sweden, and England.74 Although there is some evidence that the increasing
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Figure 4a.3 Social Security Disability Insurance awards by diagnosis: percent increase from 1957 to 1976. (From Fordyce WE: Back pain, compensation, and public policy. In JC Rosen, LJ Solomon, eds: Prevention in health psychology. Hanover, NH, 1985, University Press of New England.)
trends have leveled or reversed, disability associated with back pain remains widespread.71 Factors other than just the presence of back symptoms influence back symptom reporting and long-term disability. Multiple literature reviews have been published examining what factors are related to prolonged disability or work loss.25,59,92 Consistently, a multifactorial model of disability incorporating factors from physical, social, psychologic, and occupational domains is advocated. Of likely importance to the onset and persistence of disability are cultural norms; socioeconomic conditions, including unemployment rates and opportunities for compensation; and physical and psychosocial work environments.25,54,59,101 Many studies seeking to identify predictors of prolonged disability have enrolled subjects already in subacute or chronic states, however, thus confounding results and reducing generalizability to more acute cases. The authors of a systematic review of acute back pain prognosis reported identifying only one study of high methodologic quality that included a clinically relevant predictor.80 Clearly, further research is needed to accurately identify acute back pain patients at risk of developing chronic conditions. Compensation availability appears to affect the length of disability in the case of both surgical intervention32,43 and conservative care.39,42 However, Leavitt57 noted that most studies citing an association between compensation and back pain reporting and disability failed to take into account the effects of physical demands of the job; these can affect the outcome and differ significantly between compensation and noncompensation groups. He attempted to disentangle the effects of these factors and found that work-related back symptom reports were associated with more time loss than were non–work-related back symptoms, even after controlling for the degree of physical job demands. In addition, a related literature synthesis by Loeser et al62 concluded that when all other factors are held constant, the existing economic studies imply a positive relationship between the level of wage replacement benefits and both the incidence and duration of workers’ compensation claims. The relative effect of benefit
level appeared to be greater on claim duration than on claim incidence. This suggests that a key issue for workers’ compensation systems to contend with may be determining an optimal wage replacement ratio. Inappropriate medical management has been implicated also as a contributor to the growing disability problem. The rise in disability and increasing health care costs and utilization despite advances in medical technology led Frymoyer and Cats-Baril36 to raise the question, “Have medical professionals of all types become part of the problem rather than part of the solution?” Erroneous back pain beliefs of both health care professionals and the general public, including frequent suspicions of and investigations for major pathology and fear-avoidant beliefs in cases of simple back pain, appear to influence back pain disability.61 In regards to the desynchrony between current evidence-based treatment guidelines and popular opinions, Deyo28 stated, “The new back pain guidelines represent such a substantial shift from the traditional approach that the public will need to be re-educated.” Indeed, a recent public reeducation attempt through a social marketing campaign in Victoria, Australia, which portrayed the positive prognosis of back pain and conveyed the importance of staying active, was effective in altering beliefs and reducing workrelated disability.18
CONCLUSION AND IMPLICATIONS Back pain continues to be a major burden for developed countries. Since the earlier version of this chapter was written for the first edition of this book, further epidemiologic studies have been undertaken in an attempt to understand the prevalent and costly condition of low back pain. Because they substantially alter the conceptualization of occupational back pain, several discoveries are particularly noteworthy. First, lumbar spine degeneration, long considered a consequence of the accumulation of mechanical insults and injuries,
Chapter 4a
mainly from occupational exposures, has been found to be influenced in large part by heredity. The clinical implications of these findings include an altered conceptualization of the etiology of lumbar spine degeneration. Medical imaging findings that were once commonly attributed to occupational exposures can no longer be explained as such. Current evidence suggests that the role of occupational loading exposures is relatively minor in comparison with genetic influences. Second, the search for risk indicators has continued to result in inconsistent findings, identifying relatively small roles for environmental factors in explaining work-related back pain reporting and associated disability. These findings are contrary to earlier views that ascribed back pain incidents to excessive occupational physical loading requirements (either peak or repetitive). Thus it is not currently possible to predict which workers will experience back pain in a given occupation and which will experience delayed recovery. Finally, although the global experience of work-related back pain reporting and associated disability varies markedly by country or jurisdiction, over the past decade or so, for which figures are available, there has been an overall decline in some countries. This decline comes after many decades of growth. Recent trends in North America indicate that incidence and disability related to back injury claims, and time loss claims in particular, have declined over the past 10 years or so that data have been analyzed. However, this decline is part of one observed in all industrial injury and illness claims. The phenomena of work-related back pain incident reports, claims, and disability are influenced by socioeconomic, cultural, and broad legislative and jurisdictional factors. When comparing incidence and prevalence figures between nations and jurisdictions, great variations are thus observed. For this reason, the role of dominant paradigms through which back pain is viewed, particularly as it pertains to work, and the systems through which persons file related complaints must be acknowledged. Such factors constitute inherent biases in studies of the role of occupational exposures that must be recognized in planning epidemiologic studies and interpreting resulting data.
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Hashemi L, Webster BS, Clancy EA: Trends in disability duration and cost of workers’ compensation low back pain claims (1988-1996). J Occup Environ Med 40:1110-1119, 1998. Heine J: Uber die Arthritis deformans. Virch Arch Pathol Anat 260:521-663, 1926. Hemingway H, Shipley MJ, Stansfeld S, Marmot M: Sickness absence from back pain, psychosocial work characteristics and employment grade among office workers. Scand J Work Environ Health 23:121-129, 1997. Hestbaek L, Leboeuf-Yde C, Manniche C: Low back pain: what is the long-term course? A review of studies of general patient populations. Eur Spine J 12:149-165, 2003. Hoogendoorn WE, Bongers PM, de Vet HC, Ariens GA, van Mechelen W, Bouter LM: High physical work load and low job satisfaction increase the risk of sickness absence due to low back pain: results of a prospective cohort study. Occup Environ Med 59:323-328, 2002. Hult L: Cervical, dorsal and lumbar spinal syndromes; a field investigation of a non-selected material of 1200 workers in different occupations with special reference to disc degeneration and so-called muscular rheumatism. Acta Orthop Scand Suppl 17:1-102, 1954. Ilmarinen J, Louhevaara V, Korhonen O, Nygard CH, Hakola T, Suvanto S: Changes in maximal cardiorespiratory capacity among aging municipal employees. Scand J Work Environ Health 1(17 Suppl):99-109, 1991. Jones G, White C, Sambrook P, Eisman J: Allelic variation in the vitamin D receptor, lifestyle factors and lumbar spinal degenerative disease. Ann Rheum Dis 57:94-99, 1998. Kawaguchi Y, Kanamori M, Ishihara H, Ohmori K, Matsui H, Kimura T: The association of lumbar disc disease with vitamin-D receptor gene polymorphism. J Bone Joint Surg Am 84A:2022-2028, 2002. Kawaguchi Y, Osada R, Kanamori M, et al: Association between an aggrecan gene polymorphism and lumbar disc degeneration. Spine 24:2456-2460, 1999. Krause N, Frank JW, Dasinger LK, Sullivan TJ, Sinclair SJ: Determinants of duration of disability and return-to-work after work-related injury and illness: challenges for future research. Am J Ind Med 40:464-484, 2001. Krause N, Ragland DR, Fisher JM, Syme SL: Psychosocial job factors, physical workload, and incidence of work-related spinal injury: a 5-year prospective study of urban transit operators. Spine 23:2507-2516, 1998. Lawrence JS: Rheumatism in coal miners. III. Occupational factors. Br J Ind Med 12:249-261, 1955. Leavitt F: The physical exertion factor in compensable work injuries: a hidden flaw in previous research. Spine 17:307-310, 1992. Leino PI: Does leisure time physical activity prevent low back disorders? A prospective study of metal industry employees. Spine 18:863-871, 1993. Linton SJ: A review of psychological risk factors in back and neck pain. Spine 25:1148-1156, 2000. Linton SJ, van Tulder MW: Preventive interventions for back and neck pain problems: what is the evidence? Spine 26:778-787, 2001. Linton SJ, Vlaeyen J, Ostelo R: The back pain beliefs of health care providers: are we fear-avoidant? J Occup Rehab 12:223-232, 2002. Loeser JD, Henderlite SE, Conrad DA: Incentive effects of workers’ compensation benefits: a literature synthesis. Med Care Res Rev 52:34-59, 1995. Loney PL, Stratford PW: The prevalence of low back pain in adults: a methodological review of the literature. Phys Ther 79:384-396, 1999. Maher CG: A systematic review of workplace interventions to prevent low back pain. Aust J Physiother 46:259-269, 2000. Maniadakis N, Gray A: The economic burden of back pain in the UK. Pain 84:95-103, 2000. Marras WS, Davis KG, Heaney CA, Maronitis AB, Allread WG: The influence of psychosocial stress, gender, and personality on mechanical loading of the lumbar spine. Spine 25:3045-3054, 2000. Miettinen OS, Caro JJ: Medical research on a complaint: orientation and priorities. Ann Med 21:399-401, 1989. Miller JA, Schmatz C, Schultz AB: Lumbar disc degeneration: correlation with age, sex, and spine level in 600 autopsy specimens. Spine 13:173-178, 1988. Mooney V, Kenney K, Leggett S, Holmes B: Relationship of lumbar strength in shipyard workers to workplace injury claims. Spine 21:2001-2005, 1996. Mostardi RA, Noe DA, Kovacik MW, Porterfield JA: Isokinetic lifting strength and occupational injury. A prospective study. Spine 17:189-193, 1992. Murphy PL, Volinn E: Is occupational low back pain on the rise? Spine 24:691-697, 1999. Mustard C, Cole D, Shannon H, Pole J, Sullivan T, Allingham R: Declining trends in work-related morbidity and disability, 1993-1998: a comparison of survey estimates and compensation insurance claims. Am J Public Health 93:1283-1286, 2003. Nachemson A: The future of low back pain research. In JW Frymoyer, SL Gordon, eds: New perspectives on low back pain. Illinois, 1989, AAOS. Nachemson AL: Problemets omfatting. In Ont i ryggen, orsaker, diagnostik och behandling. Stockholm, 1991, SBU, pp. 18-28.
75. Nayha S, Videman T, Laakso M, Hassi J: Prevalence of low back pain and other musculoskeletal symptoms and their association with work in Finnish reindeer herders. Scand J Rheumatol 20:406-413, 1991. 76. Olmarker K, Rydevik B, Nordborg C: Autologous nucleus pulposus induces neurophysiologic and histologic changes in porcine cauda equina nerve roots. Spine 18:1425-1432, 1993. 77. Osti OL, Cullum DE: Occupational low back pain and intervertebral disc degeneration: epidemiology, imaging, and pathology. Clin J Pain 10:331-334, 1994. 78. Ostry A: The history of injury and industrial disease rates in British Columbia from 1950 to 1996. Can J Public Health 91:36-40, 2000. 79. Paajanen H, Erkintalo M, Kuusela T, Dahlstrom S, Kormano M: Magnetic resonance study of disc degeneration in young low-back pain patients. Spine 14:982-985, 1989. 80. Pengel LH, Herbert RD, Maher CG, Refshauge KM: Acute low back pain: systematic review of its prognosis. BMJ 327:323, 2003. 81. Ready AE, Boreskie SL, Law SA, Russell R: Fitness and lifestyle parameters fail to predict back injuries in nurses. Can J Appl Physiol 18:80-90, 1993. 82. Riihimaki H: Low-back pain, its origin and risk indicators. Scand J Work Environ Health 17:81-90, 1991. 83. Rossignol M, Lortie M, Ledoux E: Comparison of spinal health indicators in predicting spinal status in a 1-year longitudinal study. Spine 18:54-60, 1993. 84. Sambrook PN, MacGregor AJ, Spector TD: Genetic influences on cervical and lumbar disc degeneration: a magnetic resonance imaging study in twins. Arthritis Rheum 42:366-372, 1999. 85. Sarna S, Sahi T, Koskenvuo M, Kaprio J: Increased life expectancy of world class male athletes. Med Sci Sports Exerc 25:237-244, 1993. 86. Smith F, Jeffrey J, Porter RW: unpublished data. 87. Social Security Statistical Supplement (1977-1979), HE 3.3/ 3:979. Washington, DC, 1979, Government Printing Office. 88. Spengler DM, Bigos SJ, Martin NA, Zeh J, Fisher L, Nachemson A: Back injuries in industry: a retrospective study. I. Overview and cost analysis. Spine 11:241-245, 1986. 89. Spitzer WO: Scientific approach to the assessment and management of activity-related spinal disorders: a monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 12(Suppl):S12-S15, 1987. 90. Stewart WF, Ricci JA, Chee E, Morganstein D, Lipton R: Lost productive time and cost due to common pain conditions in the US workforce. JAMA 290:2443-2454, 2003. 91. Taylor PJ: International comparisons of sickness absence. Proc R Soc Med 65:577-580, 1972. 92. Truchon M, Fillion L: Biopsychosocial determinants of chronic disability and low-back pain: a review. J Occup Rehab 10:117-142, 2000. 93. Tubach F, Leclerc A, Landre MF, Pietri-Taleb F: Risk factors for sick leave due to low back pain: a prospective study. J Occup Environ Med 44:451-458, 2002. 94. van Poppel MN, Koes BW, Smid T, Bouter LM: A systematic review of controlled clinical trials on the prevention of back pain in industry. Occup Environ Med 54:841-847, 1997. 95. Videman T, et al: Elite sport as a predictor of back-related outcomes. American College of Sports Medicine Annual Meeting, Seattle, 1993. 96. Videman T, Battié MC: The influence of occupation on lumbar degeneration. Spine 24:1164-1168, 1999. 97. Videman T, Leppavuori J, Kaprio J, et al: Intragenic polymorphisms of the vitamin D receptor gene associated with intervertebral disc degeneration. Spine 23:2477-2485, 1998. 98. Videman T, Nummi P, Battié MC, Gill K: Digital assessment of MRI for lumbar disc desiccation. A comparison of digital versus subjective assessments and digital intensity profiles versus discogram and macroanatomic findings. Spine 19:192-198, 1994. 99. Videman T, Nurminen M, Troup JD: 1990 Volvo Award in clinical sciences. Lumbar spinal pathology in cadaveric material in relation to history of back pain, occupation, and physical loading. Spine 15:728-740, 1990. 100. Volinn E: The epidemiology of low back pain in the rest of the world. A review of surveys in low- and middle-income countries. Spine 22:1747-1754, 1997. 101. Waddell G: 1987 Volvo Award in clinical sciences. A new clinical model for the treatment of low-back pain. Spine 12:632-644, 1987. 102. Walker BF: The prevalence of low back pain: a systematic review of the literature from 1966 to 1998. J Spinal Disord 13:205-217, 2000. 103. Wasiak R, Pransky GS, Webster BS: Methodological challenges in studying recurrence of low back pain. J Occup Rehab 13:21-31, 2003. 104. Webster BS, Snook SH: The cost of 1989 workers’ compensation low back pain claims. Spine 19:1111-1115; discussion 1116, 1994. 105. Wiesel SW, Tsourmas N, Feffer HL, Citrin CM, Patronas N: A study of computer-assisted tomography. I. The incidence of positive CAT scans in an asymptomatic group of patients. Spine 9:549-551, 1984. 106. Woolf AD, Pfleger B: Burden of major musculoskeletal conditions. Bull World Health Org 81:646-656, 2003. 107. Yamamoto S: A new trend in the study of low back pain in workplaces. Ind Health 35:173-185, 1997.
CHAPTER
4b
Clinical Biomechanics of the Spine Malcom H. Pope
The spine is an important structure with many conflicting functions. The first function, mobility, provides the motion necessary for the activities of daily living. The second function is one of support for the body segments and any load moments that are applied by the worker. The third function is housing, in which the spinal cord and nerve roots are protected. The last function is control, with the muscles acting through the vertebrae to precisely control the posture.
FUNCTIONAL SPINAL UNIT The functional spinal unit (FSU) consists of two adjacent vertebrae, the interposed vertebral disk, and adjoining ligaments. The motion segment can be divided into anterior and posterior components. The anterior components are the vertebral bodies, the disk, and the attached ligaments; all the remaining structures are posterior components.19 The FSU is a structure in which the disk acts as a spring, the facet joints as a pivot, and the posterior ligamentous complex as another spring. Experiments have shown that the FSU exhibits coupled motion in which vertical translation also results in complex movements in other directions. The anterior elements of the FSU have a support function and a function of impact absorption, whereas the posterior elements control motion.
Anterior portion The major structural part of the anterior portion of the FSU consists of the vertebral bodies. These bear mainly compressive loads and are progressively larger caudally as the weight of the upper body increases (Fig. 4b.1). Therefore, the vertebral bodies in the lumbar region are bigger than those in the thoracic and cervical regions. Compressive strength concomitantly gradually increases from the cervical spine down to the lumbar spine. Overall, the vertebrae are six times stiffer than the disks, three times thicker than the disks, and suffer half the deformation of the disks. The vertebrae are very important in shock absorption. Under compression, endplate deformation precedes the expelling of hematopoietic contents from the vertebrae themselves. The vertebrae are an expression of Wolff’s law inasmuch as the trabeculae are oriented to resist the vertical compression forces and tensile forces through the spinous and transverse processes caused by muscle and ligament attachments. There is a zone of relative weakness anteriorly because of a lack of trabeculae.
Compressive failure, particularly in an osteoporotic individual, occurs in this region. The other major component of the anterior portion of the FSU is the intervertebral disk. The function of the disk is to distribute loads and restrain excessive motion. The disk is composed of the annulus fibrosus and nucleus pulposus. The annulus is made up of a series of sheets of collagen fibers, with the fibers of one sheet at a 30-degree angle relative to the neighboring sheet. Mathematical models show that with removal of the nucleus, interval stresses ensue as a result of the compressive forces being carried through the annulus. The inner portion of the disk, the nucleus pulposus, is rich in hydrophilic glycosaminoglycans in young adults, but with age the nucleus pulposus becomes progressively less hydrated. Animal experiments have shown that disks are avascular structures and that endplate permeability decreases with age, thereby decreasing disk nutrition. Motion is beneficial for intervertebral disks. Solute transport and metabolism are both improved by spinal motion, and intermittent motion is less effective than continuous motion. Aging usually results in disk degeneration. Degeneration of a disk reduces its proteoglycan content and thus its hydrophilic capacity. As the disk becomes drier, its elasticity and its ability to store energy and to distribute loads gradually decreases. Most disk herniations occur in the fourth decade of life, and herniations are found in 15 to 30 of autopsy specimens. The intervertebral disk exhibits creep, which means that the disk continues to deform under a constant load. This timedependent behavior comes from the fluid flow of the disk under an applied load and from the inherent viscoelastic behavior of the collagen and proteoglycan matrix. Time-dependent behavior has been demonstrated both in vivo by Keller et al8 and in vitro by Kazarian.7 The studies of Eklund and Corlett3 and Krag et al10 indirectly measured the change in overall height of the subjects. The diurnal loss was about 17 mm. Kazarian7 noted that a degenerate disk had a higher rate of deformation and the creep curve stabilized sooner. Virgin17 was the first to suggest that the nucleus pulposus acts hydrostatically to pressurize the disk and thus stabilizes the FSU. In a nondegenerate disk, nucleus pressure is redistributed as tension in the annulus layers. Normal disk pressure is about 1.5 times the compressive load divided by the cross-sectional area. Pressure is higher in the disk center and decreases toward the exterior. Nachemson15 reported that disk pressure is different in various positions or maneuvers (Table 4b.1). Andersson et al1 found in vivo that intradiskal pressure increased linearly with an increase in both trunk load and trunk moment. Disk pressure was found to be high in unsupported sitting but decreased significantly with the use of a backrest inclination greater than 110 degrees, with the use of lumbar supports, and with the use of armrests. The tensile stress in the annulus fibrosus due to disk pressure in the thoracic spine is less than that in the lumbar spine because the higher ratio of disk diameter to height in the thoracic disks reduces the circumferential stress.11
Posterior portion The posterior portion of the FSU has a primary role of guiding its movement. The type of motion possible at any level is
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C3 C4 C5 C6 C7 T1 T2 T3 T4 T5 Vertebral level
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T6
Messerer, 1880
T7
Perry, 1957
T8
Bell et al, 1967
T9 T10 T11 T12 L1 L2 L3 L4 L5
0
2000 (450 lbf)
4000 (900 lbf)
6000 (1350 lbf)
8000 (1800 lbf)
Compression strength in newtons (pound force) Figure 4b.1 Vertebral compression strength at a slow loading rate. (Modified from White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, WB Saunders.)
determined by the orientation of the facets of the FSU to the transverse and frontal planes. This orientation changes throughout the spine (Fig. 4b.2). Other structures that influence motion of the spine are the rib cage, which limits thoracic motion, and the pelvis. The cervical spine, the most mobile region of the spine, affords the head a
large range of motion, which is necessary for the activities of daily living. Except for the facets of the two uppermost cervical vertebrae (C1 and C2), which are parallel to the transverse plane, the cervical facets are oriented at 45 degrees to the transverse plane and are parallel to the frontal plane (Fig. 4b.2). The loadbearing function of the facets at all spinal levels is significant.
Chapter 4b
Load (N)
Supine (awake) Supine (semi-Fowler) Supine (traction, 500 N) Sitting (unsupported) Standing (relaxed) Coughing Straining
250 100 0 700 500 600 600
Functional spinal unit
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joints play an important role in resisting shear forces. In addition, Farfan5 showed that 40% of the torsional strength of the FSU come from the facet joints, and Lorenz et al12 suggested that 25% of the axial load bearing is from these structures.
Table 4b.1 Loads on the L3 disk calculated from intradiskal pressure measurements in a 70-kg man Position, Maneuver
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Ligaments The spine ligaments function in conjunction with other elements of the FSU as stabilizers and check reins. They are tensile elements that can fatigue, and they do contain pain fibers. The overall load deflection curve on the FSU is nonlinear, being reflective of ligament behavior. Extension loads the anterior ligaments and flexion loads the posterior elements. During flexion, the interspinous ligaments have the greatest strain, followed by the capsular ligaments and the ligamenta flava, whereas in extension the anterior longitudinal ligament bears the greatest strain. During lateral flexion, the contralateral transverse ligament is strained the greatest, followed by the ligamenta flava and the capsular ligaments. The capsular ligaments bear the most
Load sharing between the facets and the disk varies with the position of the spine. The loads on the facets are very high, peaking at about 30% of the total load when the spine is hyperextended.9 They are also quite high during forward bending coupled with rotation.4 The facets through the vertebral arches and intervertebral
Cervical (C3-C7)
0˚ A
45˚
20˚ Figure 4b.2 Orientation of the facets of the intervertebral joints. (A) In the lower cervical spine the facets are 45 degrees to the transverse plane and are parallel to the frontal plane. (B) The facets of the thoracic spine are oriented at 60 degrees to the transverse plane and at 20 degrees to the frontal plane. (C) The facets of the lumbar spine are oriented at 90 degrees to the transverse plane and at a 45 degree angle to the frontal plane. (From White AA, Panjabi MM: Clinical biomechanics of the spine, 1991, JB Lippincott.)
Thoracic
B – 60˚
45˚ C
90˚
Orientation of the facets to the transverse plane
Orientation of the facets to the frontal plane
Lumbar
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strain during rotation. The ligamentum flavum, which connects two adjacent vertebral arches longitudinally, is an exception in its behavior because it contains a large percentage of elastin. The elasticity of this ligament is therefore very high. This allows it to contract during extension of the spine and elongate during flexion. In a neutral position, the ligamentum flavum is under tension as a result of its elastic properties. Because it is located at a distance from the center of motion in the disk, it prestresses the disk and thus adds to overall stability.
independently of the rest of the cervical spine, but motion below C1 involves the entire cervical spine. The facets guide the motion, and as a result flexion-extension is coupled with transverse translation, lateral flexion with rotation (Fig. 4b.4), and rotation with axial translation. In the thoracic region, rotation is associated with lateral flexion, especially in the upper thoracic region. In this case, the vertebral bodies generally rotate toward the concavity of the lateral curve.18 Coupling of rotation and lateral flexion occurs in the lumbar spine, with the vertebral bodies rotating toward the convexity of the curve.13
KINEMATICS KINETICS The range of motion of the spine varies from level to level. White and Panjabi19 summarized these data (Fig. 4b.3). Flexion and extension are about 4 degrees in the upper thoracic, about 6 degrees in the midthoracic, and about 12 degrees in the lower thoracic segments. This increases in the lumbar motion segments to a peak of 20 degrees at L5-S1. Lateral flexion varies from level to level quite markedly but is greatest in the lower thoracic segments and L3-L4 (8 to 9 degrees). In the upper thoracic segments the range is 6 degrees. Rotation is greatest in the upper segments of the thoracic spine (9 degrees). The range of rotation is minimal in the lumbar spine because of facet orientation. The lumbar spine is susceptible to injury from rotation. There have been reports of coupled motion throughout the spine. Coupling refers to a primary motion in one direction leading to a secondary motion in another. For example, C1 moves
0˚
10˚ 20˚
0˚
10˚
20˚
The basic building materials of the spine are the vertebral bodies, which take the loads of compression, shear, and bending, and the muscles which act as the building blocks in tension. The muscles position and stabilize the spine. Without muscles, the ligamentous spine buckles under loads of as small as 2 kg. In general, the muscle electrical activity electromyographic (EMG) amplitude is directly proportional to the moment arm of the muscle line of action from the center of rotation. We can investigate the role of muscle around the periphery through a free-body analysis in which, mathematically at least, the body is cut in two and the forces and moments are resolved across that cut surface. Forces are estimated from the electromyographic signals. In complex postures, very high antagonistic activity occurs. Loads are also produced by body weight, prestress from ligaments, and externally applied loads.
0˚
10˚ 20˚
OC - C1 C1 -2 2-3 3-4 4-5 5-6 6-7 C7 - T1 T1 - 2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9 - 10 10 - 11 11 - 12 T12 - L1 L1 - 2 2-3 3-4 4-5 L5 - S1
Figure 4b.3 A composite of representative values for type and range of motion at different levels of the spine. (Modified from White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, JB Lippincott.)
Flexionextension
Lateral flexion
Rotation
Chapter 4b
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Kinetics
Neutral: OCC – C1 1.3 Nm (0.6 – 1.5) C7 – T1 1.2 Nm (0.5 – 2.2)
Left lateral flexion
Neutral
Right lateral flexion
Figure 4b.4 Coupled motion during lateral flexion is depicted schematically. When the head and neck are flexed to the left, the spinous processes shift to the right, indicating rotation. The converse is also illustrated. (Modified from White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, JB Lippincott.)
Because the lumbar spine is the main load-bearing area and the most common site of pain, studies have focused on this region. Loads on the cervical spine are mainly produced by the weight of the head, the activity of the surrounding muscles, the inherent tension of adjacent ligaments, and the application of external loads. Investigations in vivo confirm that physiologic loads are lower than those on the thoracic and lumbar spines. However, quite large loads on the cervical spine have been calculated during neck flexion, particularly in the lower cervical motion segments. Harms-Ringdahl6 calculated the bending moments generated around the axes of motion of the atlantooccipital joint and the C7-T1 motion segment with the neck in flexion, neutral position, and extension (Fig. 4b.5). The load on the junction between the occipital and C1 was lowest during extreme extension and highest during extreme flexion. The load on the C7-T1 motion segment was low with the neck in the neutral position but tucked in (ranging from an extension moment of 0.8 Nm to a flexion moment of 0.9 Nm). The load increased substantially during slight flexion (reaching 6 Nm). Moroney et al14 studied subjects who resisted loads. Calculation of the maximum (compressive) reaction forces on the C4-C5 motion segment ranged from 500 to 700 N during flexion, rotation, and lateral bending and rose to 1100 N during extension. Body position also affects the magnitude of the loads on the lumbar spine. These loads are minimal during well-supported reclining, remain low during relaxed upright standing, and rise during sitting (Fig. 4b.6). Trunk flexion increases the load by increasing the forwardbending moment on the spine. The forward inclination of the spine also makes the disk bulge on the concave side of the spinal curve and retract on the convex side. Hence when the spine is flexed, both compressive and tensile stresses on the disk increase.1 Nachemson and Elfström16 and Andersson et al2 also showed that during relaxed unsupported sitting, the loads on the lumbar spine are greater than during relaxed upright standing. In this position the pelvis is tilted backward and the lumbar lordosis straightens the upper body, thereby creating a longer lever arm for the weight of the trunk.
Slight flexion: OCC – C1 1.4 Nm (0.8 – 1.7) C7 – T1 3.7 Nm (3.0 – 6.2)
Figure 4b.5 Extension and flexion moments around the axes of motion of the atlantooccipital (OCC-C1) joint and the C7-T1 motion segment (marked with Xs) are presented for five positions of the head: extreme flexion, slight flexion, neutral, head upright with the chin tucked in, and extreme flexion. Values shown are the medial and range for seven subjects: Negative values indicate extension moments. The arrows represent the force vectors produced by the weight of the head. (Modified from Harms-Ringdahl K: On assessment of shoulder exercise and load-elicited pain in the cervical spine. Biomechanical analysis of load-EMG-methodological studies of pain provoked by extreme position. Thesis, 1986, Karolinska Institute, University of Stockholm.)
Figure 4b.6 The relative loads on the third lumbar disk for living subjects in various body positions are compared with the load during upright standing, depicted as 100. (Modified from Nachemson A, Elfström G: Intravital dynamic pressure measurements in lumbar discs: a study of common movements, maneuvers and exercises. Stockholm, 1970, Almqvist & Wiksell.)
111
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A
B
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Clinical biomechanics of the spine
C
D
Figure 4b.7 Influence of backrest inclination and back support on loads on the lumbar spine in terms of pressure in the third lumbar disk during supported sitting. (A) Backrest inclination is 90 degrees, and disk pressure is at a maximum. (B) The addition of lumbar support decreases disk pressure. (C) Backward inclination of the backrest to 110 degrees but with no lumbar support produces less disk pressure. (D) The addition of lumbar support with this degree of backrest inclination further decreases the pressure. (E) Shifting support to the thoracic region pushes the upper part of the body forward, moves the lumbar spine toward kyphosis, and increases disk pressure. (Modified from Andersson GBJ, Ortengren R, Nachemson A: Clin Orthop 129:156-164, 1977.)
E
Disk pressure
The loads on the lumbar spine are lower during supported sitting than during unsupported sitting because part of the weight is supported by the backrest. Backward inclination of the backrest and a lumbar support further reduce the loads (Fig. 4b.7).2 Because user requirements vary, the kinds of chairs available also vary widely. Regardless of use, however, it is important to be able to adjust any chair to meet the basic anthropometric dimensions of the worker. A proper seat height is desirable and should be adjustable for the individual user. The seat surface should be 3 to 5 cm below the knee-fold when the lower limb is vertical. Foot supports can be used with higher chairs. The width of the seat should be sufficient to accommodate the user. It must be possible to use the backrest, so the seat pan should not be too deep. Pressure should be avoided on the back of the thigh near the knees. Lifting creates the highest loads on the lumbar spine, and these are the occupational exposures with the greatest incidence of low back pain injury reports. The key to prevention is to reduce the load moment, which means reducing either the magnitude of the load, the distance from the body, or both. Therefore, if objects of the same weight, shape, and density but of different sizes are held, the lever arm for the force produced by the weight of the object is longer for the larger object and the bending moment on the lumbar spine is greater (Fig. 4b.7).
REFERENCES 1.
2.
3. 4.
5. 6.
7.
8. 9. 10. 11. 12.
DISCUSSION
13. 14.
The spine has functions of load bearing, protection of neural elements, and mobility yet stability. The FSU, which is the basic unit, exhibits coupled motion. It is composed of the anterior components (vertebral body, disk, pedicles, and ligament), and the remainder make up the posterior elements. Motion, which is largely controlled by the facet, varies between regimes. Flexion-extension is high in the lumbar spine, but rotation is minimal. Loads in the spine are a function of body mass, muscle activity, prestress, and external loads. The latter is particularly important in the lumbar spine.
15. 16.
17. 18. 19.
Andersson GBJ, Ortengren R, Nachemson A: Intradiscal pressure, intra-abdominal pressure and myoelectric back muscle activity related to posture and loading. Clin Orthop 129:156-164, 1977. Andersson GBJ, Ortengren R, Nachemson A, Elfstrom G: Lumbar disc pressure and myoelectric back muscle activity during sitting. I. Studies on an experimental chair. Scand J Rehabil Med 6:104, 1974. Eklund JAE, Corlett EN: Shrinkage as a measure of the effect of load on the spine. Spine 9(2):189-194, 1985. El-Bohy AA, King AI: Intervertebral disc and facet contact pressure in axial torsion. In SA Lantz, AI King, eds: Advances in bioengineering. New York, 1986, American Society of Mechanical Engineers, pp. 26-27. Farfan HF: Mechanical disorders of the low back. Philadelphia, 1973, Lea & Febiger. Harms-Ringdahl K: On assessment of shoulder exercise and load-elicited pain in the cervical spine. Biomechanical analysis of load-EMG-methodological studies of pain provoked by extreme position. Thesis, 1986, Karolinska Institute, University of Stockholm. Kazarian L: Dynamic response characteristics of the human vertebral column: an experimental study of human autopsy specimens. Acta Orthop Scand Suppl 146, 1972. Keller L, et al: In vivo creep behavior of the normal and degenerated porcine intervertebral disc-a preliminary report. J Spinal Disorder 1(4):267-278, 1989. King AI, Prasad P, Ewing CL: Mechanism of spinal injury due to caudocephalad acceleration. Orthop Clin North Am 6:19, 1975. Krag MH, Cohen MC, Pope MH: Load-induced changes in human intervertebral disc height in-vivo: a new and closer look. Orthop Trans 9(3):516, 1985. Kulak RF, Schultz AB, Belytschko T, Galante J: Biomechanical characteristics of vertebral motion segments and intervertebral discs. Orthop Clin North Am 6:121, 1975. Lorenz M, Patwardhan A, Vanderby R: Load-bearing characteristics of lumbar facets in normal and surgically altered spinal segments. Spine 8:122, 1983. Miles M, Sullivan WE: Lateral bending at the lumbar and lumbosacral joints. Anat Rec 139:387, 1961. Moroney SP, Schultz AB, Ashton-Miller JA: Analysis and measurement of neck loads. J Orthop Res 6(5):713-720, 1988. Nachemson A: Lumbar interdiscal pressure. In MIV Jayson, ed: The lumbar spine and back pain. London, 1987, Churchill Livingstone, p. 191. Nachemson A, Elfström G: Intravital dynamic pressure measurements in lumbar discs: a study of common movements, maneuvers and exercises. Stockholm, 1970, Almqvist & Wiksell. Virgin WJ: Experimental investigations into the physical properties of the intervertebral disc. J Bone Joint Surg 33B:607-611, 1951. White AA: Analysis of the mechanics of thoracic spine in man. An experimental study of autopsy specimens. Acta Orthop Scand Suppl 127:1-105, 1969. White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, JB Lippincott.
CHAPTER
4c
Initial Evaluation of the Low Back Region
have some specific properties (sensitivity and specificity) as well as those depending on the prevalence of the disease considered (predictive value) in the population being evaluated. Basically, signs and symptoms (or any other test) with very high sensitivity allow the clinician to rule out the target disease when the test is negative. On the contrary, when the specificity of a test is extremely high, a positive result “rules in” the target disease.21
Marek Szpalski, Federico Balagué, Robert Gunzburg, and Dan M. Spengler
HISTORY
Although patient evaluation and management have been clearly improved by the explosive growth in technology over the past decades, the hallmark of patient assessment continues to reside in the fundamentals of the history and physical examination. The information provided in this chapter emphasizes the importance of these basic skills to attempt to motivate the reader to continue to improve and update this important knowledge area. The focus of this chapter is the clinical assessment of patients who seek an evaluation of low back pain, with an emphasis on occupational aspects. Another relevant aspect that has become increasingly important in the last decades is the point of view of the patients. An important volume of literature devoted to this topic has been reviewed recently. In their systematic review of qualitative and quantitative studies, Verbeek et al72 highlighted the major patient expectations, specifically diagnosis, instructions, and interpersonal management. This information is important for the individual clinician. It is important to remind the clinician that the variables elicited by history taking and through a clinical examination
Two reviews of patient histories reported that although 2% to 3% of the causes of low back pain are nonmechanical, these etiologies must be considered most seriously and diagnosed quickly.20,22 All the factors that might be relevant because of their association with increased risk of cancer, infection, or other complications should be included in the history.20 In a study of almost 2000 back pain patients, Deyo21 found that no cancer was identified among those under age 50 without a history of cancer, unexplained weight loss, or failure of conservative therapy (combined sensitivity of 100%). The elements suggesting a diagnosis of specific low back pain are commonly designated in the literature as red flags (Table 4c.1).6 Concluding that a patient suffers from “nonspecific low back pain” once the clinician has reasonably excluded red flags seems to be rather unsatisfactory for most health care providers, who do not believe nonspecific low back pain to be one condition.42 It has been shown, moreover, that a comprehensive medical assessment is not predictive of return to work after an episode of occupational low back trouble.34 For all patients who are examined for an evaluation of low back pain with or without sciatica, a history of the present illness should be completed, including information regarding the nature
Table 4c.1
Red flags for potentially serious conditions
Possible fracture
Possible tumor or infection
Possible cauda equina syndrome
Age over 50 or under 20 History of cancer Constitutional symptoms such as recent fever or chills or unexplained weight loss Risk factors for spinal infection: recent bacterial infection (e.g., urinary tract infection) intravenous drug abuse, or immune suppression (from steroids, organ transplantation, or human immunodeficiency virus infection) Pain that worsens when supine; severe nighttime pain
Saddle anesthesia Recent onset of bladder dysfunction such as urinary retention, increased frequency, or overflow incontinence Severe or progressive neurologic deficit in the lower extremity
From medical history: Major trauma such as vehicle accident or fall from a height Minor trauma or even strenuous lifting (in older or potentially osteoporotic patients)
From physical examination: Unexplained laxity of the anal sphincter Perianal/perineal sensory loss Major motor weakness: quadriceps (knee extension weakness); ankle plantar flexors, evertors, and dorsiflexors (footdrop)
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of symptom onset. The absence of sciatica or femoral nerve radicular pain makes a clinically important disk herniation very unlikely (sensitivity about 0.95 and specificity 0.88).21 In addition, the examiner should document various treatment approaches and the effects of the treatments on symptoms. The reason for the evaluation and any anticipated outcomes must be understood in advance by both the physician and the patient. If the evaluation is for an independent medical evaluation, for example, the patient needs to understand its purpose of providing an independent objective assessment for a third party and that treatment is not included. The evaluation may be to assist another physician in patient management or solely to provide an insurance company or a workers’ compensation carrier with a diagnosis and recommendations. When related to swirling litigation and compensation issues, a history must usually be more detailed than one obtained solely to diagnose symptoms and manage a patient. If a patient falls at home and seeks evaluation, for example, the history might be succinct and relate only the type and distance of the fall. In a contested on-the-job injury encounter, the details may be more important for dispute resolution. Was the fall witnessed? Did the employee return to work? For how long? Is an attorney involved? Who are the physicians or others who have evaluated the patient? Has the employee had a previous injury? Has an impairment been recorded previously? An interview with a patient who is involved in litigation can be facilitated by having the referring person summarize the outcomes desired from the consultation. In addition, a succinct summary of the events to date should be provided to serve as a template for review during the patient interview. Information provided by the referral source does not replace the need for a good history; it only highlights the issues from another perspective. The opening aspects of the history should focus on the present illness. The examiner must not lead patients into answers by the use of “closed” questions, such as “Does your back pain radiate to the posterior of your thigh, calf, and foot?” Patients may often answer yes to these questions even though they may not understand what was asked or the relevance. A much better strategy is to ask the patient to describe the pain. What makes the pain better or worse? These questions can amplify the pain drawing that is gathered before the history and physical examination.9 This tool is helpful to maintain in the patient’s file to compare over time or to establish the patient’s pain pattern at the time of evaluation. In addition, recording a few notes for later dictation, the physician should also observe the psychologic, physical, and emotional behavior of the patient throughout the interview and examination. Loss of eye contact, change in voice tone, or excessive movement on the examining table should be noted, because these nonverbal cues may be equally or more important than the actual words spoken. Signs suggesting a clinical depression should be noted also because depression can be commonly encountered as both a primary and a secondary disorder in patients complaining of low back pain. Slurred speech or an impressive knowledge of pain medications should be noted also to provide clues to potential alcohol or medication abuse, the latter of which is quite common in patients who complain of chronic back symptoms.9,61 Pain patterns should also be noted. Does the pain intensity stay the same throughout the 24-hour day, or is it better or worse
in the morning or in the evening? Is the pain predictable or erratic? Is the patient’s sleep pattern disrupted because of night pain? Although night pain can be associated with various forms of malignancy or inflammatory disorders, it can also reflect clinical depression or be associated with psychosocial issues. The relationship of various activities to the pain complaints should be discussed as well. Pain that increases with walking short distances yet disappears rapidly with sitting or lying can represent a typical pattern in a patient with lumbar spinal stenosis. A clinical diagnosis cannot be advanced solely on the basis of the pain pattern, however, because of the wide variability of clinical symptoms in most disorders that result in low back pain. When interviewing a patient with low back pain that has been present for more than 3 months, the physician should completely review the patient’s systemic symptoms, including fever, chills, night sweats, weight loss, and lethargy, along with any sources of infection, whether systemic or not, such as a localized cutaneous abscess. Gastrointestinal symptoms are relevant because such disorders can actually occur concomitantly with low back symptoms and because so many patients take large doses of salicylates or nonsteroidal antiinflammatory agents, which can lead to significant gastrointestinal bleeding.53 Genitourinary symptoms are reviewed also, because bladder dysfunction can be associated with pressure on the spinal cord or cauda equina. Although such symptoms are more commonly related to causes other than neural compression, an early recognition of a change in bladder habits may signal a subtle increase in pressure on the neural elements.5 When genitourinary symptoms are present, the physical examination should include a well-documented rectal examination. A cystometrogram and a urologic consultation may be necessary to clarify the nature of these problems.5 Female patients should be questioned regarding any changes in bleeding patterns or pain related to menstruation, and those with persisting back complaints should be evaluated by their gynecologists. Medications taken by the patient should also be recorded. If the patient has been taking multiple medications in the past for back pain, the associated clinical response should be noted. Other back treatment approaches, including the patient’s pain-free interval after an intervention such as steroid dose packs, epidural steroid injections, or physical therapy, should be noted as well. Psychosocial and economic issues associated with the low back symptoms should be reviewed. Life stressors, litigation, compensation, and other secondary gain parameters would likely not have “caused” the pain, but such issues can certainly maintain the chronicity of symptoms in specific cohorts of patients. A systematic review of psychologic factors as predictors of chronicity or disability highlight the limits of the available evidence, but the roles of distress/depressive mood and, to a lesser extent, somatization are underlined. As discussed in greater detail in Chapter 2, the role of coping strategies and fear avoidance deserve further research.52,73 In recent years a list of red flags and treatment matrices have been enlarged to include cognitive and behavioral approaches into the early management of acute low back pain. “Yellow flags” can be evaluated by means of six open questions that should be phrased in the health care provider’s own words: 1. Have you had time off from work in the past with back pain? 2. What do you understand to be the cause of your back pain? 3. What are you expecting will help you?
Chapter 4c
4. How are your employer, coworkers, and family responding to your back pain? 5. What are you doing to cope with back pain? 6. Do you think that you will return to work? When?40 Moreover, “blue” flags (psychosocial aspects of work) and “black” flags (employer-specific and global) aimed at evaluating other socioeconomic environmental factors have been described in the last few years.31 The past medical history should be completed to include any diagnostic assessments, treatment approaches not previously noted, and doctors or others who have evaluated or treated the patient for low back and other medical problems. The length of any pain-free interval after previous surgical procedures should also be documented. Short-term relief after major surgery may occur after procedures that may not have been clearly indicated. Other causes can include an operation performed at the wrong spinal level, an inaccurate diagnosis, an associated medical disorder with referred low back symptoms, and a pain-prone patient who tends to amplify symptoms. A comparison of the existing occupational health guidelines for the management of low back pain revealed that all the published guidelines distinguished specific and nonspecific cases and consistently recommended a clinical history to identify relevant physical and psychosocial workplace factors and a physical examination including neurologic screening. Red and yellow flags are highlighted by most of the guidelines.63
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Physical examination
patient and doctor. They must be understood in the context of the patient’s history and offer only a psychologic “screener,” not a complete psychologic assessment. Finally, they are not on their own a test of credibility or veracity, nor are they a reason to deny appropriate physical treatment.48 A study showed that with regard to return to work in patients with acute low back pain, the predictive value of the nonorganic symptoms or signs (independently or combined) was rather poor.28 The patient should be suitably attired for the examination to provide for privacy but also to facilitate a complete musculoskeletal evaluation. Together with a sheet for the supine and prone portions of the examination, the standard patient gown that is open in back is quite appropriate. The physical examination should be complete but also age and complaint related. Although not an essential portion of the examination in an 80-year-old patient with back pain after a minor fall, chest expansion, for example, is clearly important in a 20-year-old man with an insidious onset of low back pain over a long period of time. Decreased chest expansion (less than 2.5 cm) in such a patient could suggest the diagnosis of ankylosing spondylitis. A study showed that a screening system led by two physiotherapists resulted in a clinical and economic improvement in the care of those suffering from acute low back pain.49 The physical examination is divided into five components based on the position of the patient, beginning with the patient standing.
Patient standing PHYSICAL EXAMINATION A physical examination is one among many patient expectations72 that permits the physician to assess the patient and record the observations. Objective findings, including deep tendon reflexes and circumferential measurements of the calf and thigh to determine swelling or atrophy, represent the most important parameters. Less helpful, subjective, physical examination findings include supine straight leg raising (unless done in the sitting position as well) and range of motion, the least reliable of all determinants.3 Unfortunately, range of motion is still used, although to a lesser degree, for impairment ratings as suggested in the American Medical Association guidelines. Inappropriate physical examination findings are important to record also. A certain number of inappropriate physical signs have been described and are often referred to as “Waddell’s signs.” Too often, physicians consider the presence of three or more of these findings as an alert that the patient may be attempting to amplify them for secondary gain. It is important to note, however, that the presence of inappropriate physical findings does not exclude the presence of a pathologic process and may be due to factors other than attempted malingering. This illness behavior may be linked to fear of reinjury, misunderstanding of instructions, other psychologic issues, and other incident issues. The onus is therefore on the physician to recommend the appropriate diagnostic studies. Main and Waddell48 discussed the theoretical misunderstandings of the behavioral signs in clinical practice and in the medicolegal context. We reproduce here some of the authors’ conclusions and recommendations. As “behavioral responses to examination,” these signs are a form of communication between
The lumbar spine examination begins with the patient standing. The physician should observe the general configuration of the spine to detect any lateral curvatures, kyphosis, or excessive lordosis. Patients with lumbar paraspinous spasms frequently have a pelvic list that should be noted. In patients with lumbar disk herniation, it has been demonstrated that although not associated with the location of nerve root compression, the direction of lumbosacral scoliotic list is related to the side of disk herniation.64 In young adult males with low back pain, chest expansion should be measured with a cloth tape because expansion less than 2.5 cm suggests an inflammatory process such as ankylosing spondylitis. After observing the spine orientation in the erect patient, the physician should ask him or her to flex forward, a step particularly important in adolescents to detect early lateral curvatures of the spine. To assess the range of motion of the lumbosacral spine, the physician should stand behind the patient and observe the lumbar paraspinous muscles. Any eccentric contractions of the musculature suggest lumbosacral paraspinous spasms; limited motion without evidence of such eccentric contractions might suggest a lack of patient cooperation even though there are other possibilities (such as a congenital block or previous fusion). Forward and lateral flexion and extension of the lumbar spine should be observed. Normal patients should be able to bend forward nearly to touch their toes and to the sides to touch the fibular heads, but extension of the spine is extremely variable. In general, pain increased by flexion suggests lumbar disk abnormalities and pain with extension suggests degenerative changes involving posterior elements of the spine, lumbar spinal stenosis, or both. Occasionally, patients with lumbosacral paraspinous
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spasm can flex forward reasonably normally but have difficulty returning to the erect position. Such patients may accomplish this move in a two-phase recovery by flexing the knees and extending the hips without motion in the lower back. The true value and reliability of flexibility assessment is, however, dubious. The reliability of lumbar flexion and extension measured with an electronic inclinometer within a complete physical examination was evaluated in a group of normal volunteers. The intrarater and interrater reliability for flexion were, respectively, 0.48 and 0.56, whereas the same values for extension were 0.53 and 0.37, respectively.33 In older patients, the range of motion of the cervical spine should also be assessed because degenerative osteoarthritis of the cervical spine occasionally results in low back complaints. A study including 27 patients suffering from lower back pain and unilateral single nerve root symptoms, 14 patients with multilevel nerve root symptoms, and 10 control subjects showed that low back pain correlated significantly with restriction of anteroposterior spinal flexion measured with a computerized triaxial potentiometric analysis system.54 After observing the range of motion, the physician should percuss the spine to detect any localized tenderness, a subjective reaction. This test has little value if the patient has tenderness at multiple areas, but consistent localized tenderness over the midline of the spine may suggest inflammatory diskitis (or fractures, tumors, and so forth). The costovertebral angle should be palpated; tenderness in this area suggests a genitourinary problem such as pyelonephritis. Patients should next be asked to walk on their heels and then toes to assess the overall strength of the dorsiflexors (L5) and plantar flexors (S1) of the ankle. In particular, the extensor hallucis longus muscles should be observed when the patient is walking on the heels, because discrepancies can be detected between this act of walking and later passive strength testing. To assess and detect weakness of the triceps surae muscles, which are innervated primarily through the S1 nerve root, the physician should ask the patient to hop several times on the left foot, then on the right foot, and note any discrepancies in the two abilities. The patient should be observed also while walking in the examining room. Extreme staggering from side to side and other bizarre gait patterns suggest symptom amplification. Patients with true herniated disks often have a gait pattern slightly antalgic on one side but with no bizarre abnormalities.
Patient sitting The patient should next sit on the edge of the examining table so the physician can perform the knee and ankle reflex tests and determine the strength of the extensor hallucis longus muscle. This latter examination is critical in all patients complaining of back and leg pain because many have weakness of the extensor hallucis longus but not the tibialis anterior. Weakness of the extensor hallucis longus in a patient who complains of back and leg pain suggests involvement of the L5 nerve root. The extensor digitorum brevis muscle should be checked; however, some authors remain unconvinced that observation of this muscle has any diagnostic significance in patients with lumbar disk disease. Asymmetry is often observed in patients who have never had low back and/or leg pain.
Figure 4c.1 Sitting straight leg raise test. The patient leans back in the “tripod” sign, indicative of true sciatic tension.
The most important portion of the sitting examination is the distracting straight leg raise (SLR) test (Fig. 4c.1). The SLR test has shown to be adequate in healthy subjects when performed within a complete physical examination.33 During this lifting of an extended symptomatic leg in the sitting position, patients with herniated disks and true symptoms of sciatic tension arch backward and complain of pain in the buttock, posterior of the thigh, and calf. Patients who do not have true sciatic tension do not recognize this as a sciatic tension test and therefore have no symptoms. For the patient who complains of pain in the neck as well as the lower back, the strength and reflexes of the upper extremities can be evaluated while he or she is sitting.
Patient supine With the patient supine on the examining table, the physician uses a standard tape to measure the true length of the limbs from the anterior superior spine to the medial malleolus on both sides. Although significant discrepancies (more than 2.5 cm) in limb lengths can result in mild compensatory scoliosis and low back discomfort, these associations are uncommon. The physician should observe the thigh and leg muscles for early signs of atrophy. In addition, the physician should use a cloth tape to measure the circumferences of both thighs one handbreadth above the patella and those of both calves one handbreadth below the patella. Discrepancies greater than 2 cm again are probably significant and suggest muscle atrophy. For the standard ipsilateral SLR maneuver, the physician stands to the patient’s right, places the left hand on the patient’s patella to extend the knee, places the right hand under the os calcis, and then lifts the leg while keeping the knee extended (Fig. 4c.2). Because patients often describe their discomfort in different locations in the extremity, the objectivity of the test results are qualified. If the patient complains of radicular discomfort
Chapter 4c
Figure 4c.2 Supine straight leg raise (SLR) test. For maximum accuracy in identifying sciatic tension, this test must be compared with the sitting SLR test.
during the test, the limb should not be lifted any higher. At that moment, plantar flexion of the ankle should be performed as a distracting test. Because plantar flexion of the ankle should not increase back pain, exacerbation of pain may suggest amplification of symptoms by the patient. Dorsal flexion, on the contrary, should increase sciatic tension and pain (Fig 4c.3). The physician should perform the crossed SLR test also by lifting the nonsymptomatic extremity as in the ipsilateral SLR test. If the patient complains of discomfort radiating into the symptomatic extremity when the well extremity is lifted, this test is positive, almost invariably indicating lumbar disk herniation. During both the SLR test and the crossed SLR test, the patient must be allowed to state where the discomfort is occurring. Specifically, asking the patient whether lifting the well extremity causes pain in the symptomatic extremity invalidates the test. It is important to note that in patients with L4-L5 and L5-S1 disk herniations, the SLR test has very high sensitivity (95%) but lower specificity, whereas the cross SLR has much lower sensitivity (25%) but significantly higher specificity (90%).20
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Patrick’s test should then be performed bilaterally. In this test, the shear force applied across the sacroiliac joint helps detect early abnormalities. Many patients with osteoarthritis of the hip complain of buttock pain rather than the classic groin discomfort, causing the hip joint often to be overlooked because of the apparent back problem. Patients with abnormalities of the hip joint cannot tolerate Patrick’s test, however, because of the discomfort when the limb is fully externally rotated into the abducted position. While the patient is supine with the limbs extended, the physician should therefore gently rotate the lower extremity both internally and externally, a gradual rotation that reveals early irritability in the hip joint. If internal and external rotations cause pain, it may arise from that area. Brown et al14 reported on the clinical signs that may be helpful to distinguish between a hip disease and a spinal origin of pain: “the presence of a limp, groin pain, and limited internal rotation of the hips more often was associated with and predictive of a hip disorder than a spine disorder.” The abdomen should be examined by palpating the four quadrants to detect any intraabdominal masses. Abdominal lesions may erode into the lumbosacral plexus and cause symptoms identical to those of lumbar spinal stenosis or disk disease (Fig. 4c.4). The strength of the abdominal muscles should be assessed by having the patient flex the knees while keeping the feet flat on the table and then perform a sit-up. Patients who have extreme difficulty completing even one sit-up are theoretically excellent candidates for a vigorous rehabilitation program. In addition, the patient should be asked to hold the lower extremities 15 to 20 cm off the table. In general, a patient with an established herniated disk can easily perform this maneuver, so the primary value of this test is to assess the strength of the abdominal musculature rather than determine the likelihood of a disk herniation. With the patient supine, the motor strength of the iliopsoas, quadriceps, and hamstrings, along with Babinski’s reflexes and proprioception, should all be assessed. A sensory examination also should be performed and recorded. A study demonstrated significant elevations of warm, cool, and touch perception thresholds correlated with leg pain in patients with unilateral L5 or S1 nerve root pain. However, dermatomal quantitative sensory tests require some specific tools that are not part of the routine clinical equipment.54
Patient on side
Figure 4c.3 Dorsiflexion of the ankle during a straight leg raise test increases pain.
The supine patient is then asked to turn on one side and to raise and maintain the superior extremity against resistance by the physician (Fig. 4c. 5). In most patients, the gluteus medius is innervated primarily by L5, so patients with L5 radiculopathy often have weak abductors, as do patients with significant hip disease. The trochanter should be palpated to test for trochanteric bursitis. These same tests should be repeated with the patient lying on the opposite side. With the patient on one side, perianal sensation and but-tocks sensation also should be evaluated. All patients over the age of 40 and any patient suspected of a neurologic deficit should have a rectal examination. In males, anal sphincter tone and the size of the prostate may be assessed. Female patients with chronic back pain should have a pelvic examination by a gynecologist.
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A Figure 4c.4 on an MRI.
B (A) CT of a calcified arthrosynovial cyst (circled) causing left nerve root entrapment. (B) The same pathology is less obvious
Figure 4c.5
Gluteus medurs strength testing with the patient on the side and abducting against resistance.
Chapter 4c
Patient prone With the patient prone on the examining table, the lumbar spine, sacrum, and sacroiliac joints should then be reexamined for any localized tenderness. A reverse SLR maneuver can easily be accomplished by the physician simply by lifting both of the patient’s lower extremities off the table, although quite often just bending the knees in the prone position is enough to elicit pain in the L3 or L4 dermatome. The patient should next flex the knees 90 degrees so that the physician can observe internal and external rotation of the hips. In most patients, the amount of internal and external rotation is quite similar. Patients with femoral anteversion, however, have excessive internal rotation and limited external rotation and often experience discomfort in the low back area and buttocks while running. When the patient is prone, ankle jerks often are easier to reexamine and compare; the absence of one or both reflexes should be noted. Finally, the patient should extend first one lower extremity and then the other by using the gluteus maximus muscle. Increased low back discomfort during this maneuver suggests a more superficial myofascial source of the symptoms.
ADDITIONAL INVESTIGATIONS After careful history taking and physical examination (and only then), a number of technical examinations can be ordered based on the results. None of those examinations should be considered as a screening tool, “to see how they come out.” A specificity of low back pain is that in most cases a precise cause of nociceptor cannot be precisely determined despite the increasing sophistication of investigations. Specialized examinations should serve to confirm or pinpoint a suspected diagnosis, and the precision of each should be known. That precision can be determined by statistical measures of sensitivity (the proportion of subjects with the disease in whom the examination is positive), the specificity (the proportion of subjects without the disease in whom the examination is negative), the accuracy, and the predictive value. The two latter measures are not always available in all cases, and in the context of back pain the specificity of imaging is often poor due to a wide range of abnormal images that are asymptomatic. With more sophisticated examinations, more asymptomatic abnormal images are found. In contrast to severe osteoarthritis of the hip or knee, which does not affect everyone and is seldom asymptomatic, marked degenerative changes in the spine seem to affect nearly all human beings with aging and are often asymptomatic. The patient should be told the reason for which an examination is ordered and advised that it may show some meaningless “pathologic images” that are irrelevant to the present symptoms. Those incidental findings are usually nonsignificant and not what was suspected and researched. We all see patients coming with multiple radiology reports where statements about “black disk,” “bulging disk,” or “degenerative changes” have been strongly underlined or highlighted by the patient (or sometimes the doctor). Those misconceptions can lead patients to further impressions of seriousness and prolonged disability. Early and complex imaging
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Additional investigations
with precise description of nonsignificant abnormalities facilitates the “medicalization” of low back pain,12 and duration of disability is associated with its early increased use.47 Patients’ perceptions, expectations, and demands play a major role in the use of imaging modalities to diagnose low back pain. A myth common among patients is that radiographs will show the exact cause of their back pain,36 so they expect to have radiographs when seeing doctors for such complaints.43 They wish to have an x-ray examination ordered, moreover, and physicians’ attitudes are often correlated to patient wishes.77 It appears then that patient education is necessary, although physician education is perhaps even more acutely needed.74 Although many guidelines about diagnostic procedures in back pain have been published in several countries, multiple studies show that most are not followed in the United States,27,56 Canada,8 Norway,77 and Spain.29 All those studies reveal that physicians, mainly in primary care settings but also specialists, still order too many examinations that are of little use.
Plain radiograph Plain radiographs have been the standard (and only widely available) imaging technique in assessment of back pain for decades. They show the bony structures precisely, displaying spondylolysis, spondylolisthesis, deformities, tumors, fractures, and degenerative changes such as disk narrowing, disk vacuum, and traction osteophytes. The latter, however, appear to be a normal evolution of the spine and are very common in symptom-free middle-aged and aged subjects. Instability can be assessed on dynamic (flexion/extension/lateral flexion) radiographs, but the relation of radiologic “instability” to back pain is subject to discussion.65 For these reasons plain films have very low specificity and therefore low diagnostic precision38 and make no difference to the outcome for back pain,78 especially in elderly subjects.10,71 In the case of acute low back pain in a subject between 18 and 50 years of age, plain films are indicated only if there is a history of trauma, malignant disease, or symptoms of infection. In the case of neurologic symptoms, magnetic resonance imaging (MRI) (or computed tomography [CT] if it is unavailable) might be a better diagnostic tool. If no clinical improvement is observed after 6 weeks, plain films may be taken to help exclude a diagnosis of tumor, infection, spondylolysis or olisthesis, and osteoarthritis of the hip, and along with simple laboratory tests will rule out systemic diseases.37 Some studies suggest, however, that in the absence of red flags, radiographs should not be ordered even after 6 weeks of symptoms.41 In chronic low back pain, the same pathologies should be ruled out, but preferably by MRI.10
Myelography Until the advent of CT, myelography was the only examination that enabled physicians to assess spinal neural structures, the dural sac, and the roots. Myelography is still the only widely available examination permitting a dynamic view of the dural sac during flexion and extension in the upright posture (Fig. 4c.6). Given the decrease of the dural sac diameter during extension, some cases of
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stenosis can be underestimated during examinations like CT or MRI that are performed in a supine position. Although upright MRI is becoming available, it is very expensive, uncommon, and constrained in patient positioning and acquisition time, making it inappropriate for this kind of assessment in stenotic patients. Upright myelography examination appears useful also in the diagnosis of position-related disk herniations35 and those in the lateral recess where MRI may underestimate root compression in nearly 30% of cases.2 Indeed, some authors have demonstrated similar sensitivity and specificity in myelography and MRI.55 Myelography is an invasive procedure, however, and neurologic or infectious complications, although very rare, are possible. Combined with CT (myelo-CT), myelography still has a place in cases of strong clinical suspicion of stenosis or herniated disk not clearly demonstrated on other imaging modalities. It also enables the laboratory analysis of the cerebrospinal fluid to be performed to rule out a number of neurologic diseases.
Computed tomography
Figure 4c.6 Myelogram showing multiple level central degenerative stenosis (arrows). Myelogram remains the only widely available examination enabling dynamic and upright assessment.
A
CT is the first examination to provide axial and three-dimensional representations of the spine and the first noninvasive examination to provide a view of spinal neural structures. When it appeared in the 1970s, it was a true revolution. It has now been widely replaced by MRI for the assessment of neural structures but still remains the best examination for the visualization of bony elements. It is also the only examination available for claustrophobic patients or for those with pacemakers or ferrous metallic implants. CT also offers more precise views of calcified disk protrusions.24
B
Figure 4c.7 (A and B) Spondylolysis and olisthesis are best investigated by computed tomography. In this case the pars defect is partially filled by Gill’s nodules (ossified fibrous tissue), which when associated with a disk bulge provoke a lateral stenosis.
Chapter 4c
CT shows more precisely the patterns of fractures in trauma cases and investigates pars fracture in spondylolysis or olisthesis (Fig. 4c.7). In the case of spinal stenosis, if MRI allows a better view of neural elements, CT is still invaluable to investigate the osseous participation in the stenotic process. We believe that it complements MRI before surgical treatment of lumbar stenosis. Spiraled helical CT allows a three-dimensional view of long spinal segments and as such may be very interesting for the accurate description of deformities.
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Additional investigations
MRI has become the standard investigation tool for spinal disorders. The precision of this examination handicaps its specificity, however, because it demonstrates a high frequency of clinically irrelevant abnormal images without associated symptoms. Some studies have shown a prevalence of 28% of disk herniations, at an average age of 42, in asymptomatic subjects,11,39 up to 52% of
which presented at least one bulging disk.39 With MRI, degenerative intervertebral disk disease is present in one third of subjects between 20 and 39, over half of those between 40 and 59, and in nearly all subjects over that age.11 Apparently, a normal physiologic evolution of the decrease of disk hydrophilic properties, dark or black disks, appear in almost everyone. These findings underline that to avoid misunderstandings by patients, MRI results must be interpreted with great care and meticulously related to clinical presentation. Even in the presence of symptoms, the correlation between the severity of clinical findings and MR images of mild to moderate compression due to bulging or stenosis is poor.4 Keeping these limitations in mind, MRI is nevertheless the best tool to investigate compromise of neural elements of the spine. In spinal stenosis it is especially useful in determining the extent of the narrow canal. In presence of a suspicion of neural compression, the addition of MR-myelography, realized through specific acquisition sequences, complements the results of the standard MRI in many cases (Fig. 4c. 8,9).26
Figure 4c.8 Voluminous extruded disk herniation provoking a cauda equine syndrome. In this case magnetic resonance imaging is the examination of choice. The patient had a full recovery after surgery.
Figure 4c.9 Magnetic resonance image of a lytic spondylolisthesis showing root entrapment in the foramen. The root (A) is hampered by the disk bulge in the foramen (B) consecutive to the sliding and flattening of the disk.
Magnetic resonance imaging
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Because it is usually performed in the supine position, MRI may underestimate images of compression in position-related stenosis or sciatica, as is the case with neurogenic claudication. Devices enabling axial compression during supine MRI (or CT) appear to add useful information about the decrease of the spinal canal diameter that appears during upright weight-bearing positions76 and also to enable more precise surgical strategies to be performed.32 MRI is highly specific and sensitive also in the research of malignant and infectious spinal diseases, warranting the use of gadolinium-enhanced MRI in acute low back pain when one of those pathologies is suspected.30 The results in MRI investigation of back pain are more subject to caution. An example is the high intensity zone, the presence of which has appeared to show much promise as a marker of discogenic low back pain. The high intensity zone is a high T2 signal in the posterior and/or posterolateral annulus that seems to increase during axial loading.59 Some authors have found a high correlation of this finding with pain and annular penetration of the dye during diskography, which they believe demonstrates a very high positive predictive value.1,60 Other authors, however, have shown a high prevalence of high intensity zone in asymptomatic subjects,15 whose reaction to diskography is similar to that of symptomatic patients.20 The sensitivity of the sign is low,58 and although it seems that the high intensity zone may show an annular fissure, that fissure is not a reliable sign of painful disk disease. In patients without active symptoms, furthermore, annular disruption is a weaker predictor of future low back pain than psychologic distress.19
have proposed ultrasonic imaging combined with pain provocation by vibrations to diagnose internal annular tears,79 but this technique has not gained widespread acceptance. Investigation of nerve roots and facets has been abandoned due to the lack of accuracy.51 Those examinations do not play a major role in spinal imaging.
Diskography Provocative diskography, which aims at back pain reproduction, has been a controversial subject for many years. It has been considered by some authors to be the best indicator of discogenic pain and has been widely used to confirm surgical indications of fusion and, more recently, disk replacement. Even after positive diskography, however, fusion results remain unpredictable.75 Furthermore, the frequency of positive responses to diskography among asymptomatic subjects challenges the value of this examination as a predictor of clinically relevant discogenic pathology.16,18 Although diskography is indeed a good indicator of annular tears, the latter do not appear to predict a clinically relevant spinal pathology.16 Specificity of diskography appears low,17 and pain intensity during injection is influenced strongly by the patient’s psychologic factors and compensation claims.16 In any case, diskography has no place in the initial assessment of low back troubles.
Electromyography Radionuclide bone scan Radionuclide bone scan (isotopic) is a highly sensitive but poorly specific examination. Of the different radionuclides that can be used, technetium-99m is the most common in spinal indications because it is highly sensitive for malignant diseases and infections. Bone scans using markers such as gallium or marked leucocytes show better specificity for infections. Nearly 40% of subjects with spinal metastasis and normal plain films have a positive bone scan.50 The test might help also to determine whether a vertebral or pelvic fracture is recent or old. Single photon emission CT has been suggested as useful for identifying patients with facet joint disease more likely to benefit from facet injections.23 Single photon emission CT also reveals many abnormalities not detected on a standard radiograph,57 but here again one might wonder about the clinical relevance of those findings. Whereas either the planar bone scan or single photon emission CT reveals areas of increased bone turnover, these tests lack the specificity necessary to determine the true nature of the “lesion” and serve only as indicators for further studies in accordance with the clinical presentation.
Ultrasonography Ultrasonograms may be useful in cases of paraspinal soft tissue infections or tumors or to rule out other sources of lumbar pain, such as urinary tract calculus or kidney diseases. Some studies
Electromyography may be useful in specifying the level of symptomatic compression and ruling out peripheral neuropathies (diabetic, ethylic, or other). One must bear in mind that electromyography shows abnormal signals only several weeks after the occurrence of a nerve compression. Although interesting as an adjunct examination, electromyography is not an essential tool in the initial assessment of spinal troubles.
Mechanical testing The inability to correlate low back pain to anatomic findings and the difficulties in quantifying pain have directed much effort toward measurement of spinal performance through the assessment of function across various dimensions such as flexibility, strength, speed, endurance, and coordination. Goniometers and isokinetic and isoinertial dynamometric devices are currently used. Isoinertial testing seems to be the most physiologic and clinically relevant approach. Useful for prescribing musclestrengthening therapy precisely, it enables the physician to follow up on the patient’s progress and can also be used to assess the efficacy of diverse treatments.44,46,68 In certain pathologies like spinal stenosis, specific patterns of motion have been demonstrated,69 and early decrease of spinal function has been shown in subjects with Parkinson disease.13 The use of neural network technique analysis of motion patterns has enabled researchers satisfactorily to assign back pain patients to pathologic categories based on the Quebec Task Force classification.7 These tests can also provide insight into the maximum effort exerted by the subjects62,66 but
Chapter 4c
despite the hopes of their proponents are by no means back pain “lie detectors.” The measure of flexibility is of limited value in the assessment of the spine,70 and the current American Medical Association guidelines for evaluating disability, heavily based on spinal range of motion, can lead to irrelevant results.45 More elaborate protocols, based on more complex analysis of kinematic profiles, appear to be much more promising.25
Other diagnostic studies Laboratory evaluation should be recommended for patients who are not responding to treatment or who have severe pain. Although many of these tests are indicated in specific situations, a useful screening evaluation for patients with persistent symptoms should include a complete blood count, sedimentation rate, coagulation survey, sequential multiple analysis-18, and urinalysis. Patients who show diminished bone density should be evaluated more thoroughly with thyroid studies, protein electrophoresis, urinary calcium, and evaluation of parathyroid hormone levels. Should one proceed this far in the evaluation, a referral to an endocrinologist with an interest in calcium metabolism is clearly warranted. In young male patients suspected of having ankylosing spondylitis, an HLA-27 antigen study can be ordered.
DIFFERENTIAL DIAGNOSES When evaluating patients with complaints of low back pain, the physician must remain vigilant to identify those whose symptoms result from referred pain unassociated with the intervertebral Differential diagnosis disk or spinal nerves. In this of low-back pain time of intense focus on cost, the physician must also remain Trauma dedicated to a proper evaluaInfections tion for the patient and not Inflammations succumb to managed-care Neoplasms bureaucrats who are interested Developmental abnormalities primarily in the cost rather Metabolic diseases than the quality of care. Patients with low back pain Degenerative disorders represent an interesting group. Neurologic disorders A list of differential diagnoses Referred pain is provided in the box to the Psychological disorders right. Approximately 2% of Miscellaneous patients who come to a low back specialty clinic have evidence for neoplasms as the source of the symptoms.10 A list of suspected causes coupled with the knowledge of appropriate testing aid the physician in formulating a proper workup. A complete history and careful physical examination must underlie any assessment for low back pain. Physicians should remember that their most effective and readily available tools are their hands and brains. Only after this meticulous first stage has been completed can specialized examinations be ordered to answer precise questions and to confirm or eliminate specific pathologies.
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References
Evidence-based medicine principles apply to diagnostic investigations, but there are no screening tests for back pathologies. The poor specificity of the most common imaging techniques is inversely proportional to the frequency of their use. Radiographs and now MRI, which seem to be used almost as routine investigations in low back pain patients, provide a huge quantity of clinically irrelevant information. In a world in which health care resources are decreasing while the population ages and increasing technology costs demand further funding, physicians will be held accountable for unjustified practice costs. Patients should be educated and alerted that technology will not invariably uncover the precise reason of their pain, but physicians too require education, as the failed implementation of many guidelines painfully shows.
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Pincus T, Burton AK, Vogel S, Field AP: A systematic review of psychological factors as predictors of chronicity/disability in prospective cohorts of low back pain. Spine 27:E109-E120, 2002. Pincus T, Griffin M: Gastrointestinal disease associated with nonsteroidal anti-inflammatory drugs. Am J Med 91:209-212, 1991. Quraishi NA, Taherzadeh O, McGregor AH, Hughes SPF, Anand P: Correlation of nerve root pain with dermatoma sensory threshold and back pain with spinal movement in single level lumbar spondylosis. J Bone Joint Surg 86B:74-80, 2004. Ramsbacher J, Schilling AM, Wolf KJ, Brock M: Magnetic resonance myelography (MRM) as a spinal examination technique. Acta Neurochir (Wien) 139:1080-1084, 1997. Rao JK, Kroenke K, Mihaliak KA, Eckert GJ, Weinberger M: Can guidelines impact the ordering of magnetic resonance imaging studies by primary care providers for low back pain? Am J Manag Care 8:27-35, 2002. Ryan PJ, Evans PA, Gibson T, Fogelman I: Chronic low back pain: comparison of bone SPECT with radiography and CT. Radiology 182:849-854, 1992. Saifuddin A, Braithwaite I, White J, Taylor BA, Renton P: The value of lumbar spine magnetic resonance imaging in the demonstration of anular tears. Spine 23(4): 453-457, 1998. Saifuddin A, McSweeney E, Lehovsky J: Development of lumbar high intensity zone on axial loaded magnetic resonance imaging. Spine 28(21):E449-E451, 2003. Schellhas KP, Pollei SR, Gundry CR, Heithoff KB: Lumbar disc high-intensity zone: correlation of magnetic resonance imaging and discography. Spine 21(1):79-86, 1996. Spengler DM, Loeser JD, Murphy TM: Orthopaedic aspects of the chronic pain syndrome. Instr Course Lect 29:101-107B, 1980. Spengler DM, Szpalski M: Newer assessment approaches for the patient with low back pain. Contemp Orthop 21:371-378, 1990. Staal JB, Hlobil H, van Tulder MW, et al: Occupational health guidelines for the management of low back pain: an international comparison. Occup Environ Med 60: 618-626, 2003. Suk KS, Lee HM, Moon SH, Kim NH: Lumbosacral scoliotic list by lumbar disc herniation. Spine 26:667-671, 2001. Szpalski M: The mysteries of segmental instability. Bull Hosp Jt Dis 55:147-148, 1996. Szpalski M, Federspiel CF, Poty S, Hayez JP, Debaize JP: Reproducibility of trunk isoinertial dynamic performance in patients with low back pain. J Spinal Disord 5:78-85, 1992. Szpalski M, Gunzburg R: Methods of trunk testing. Semin Spine Surg 10:101-111, 1998. Szpalski M, Hayez JP: Objective functional assessment of the efficacy of tenoxicam in the treatment of acute low back pain: a double-blind placebo-controlled study. Br J Rheumatol 33:74-78, 1994. Szpalski M, Michel F, Hayez JP: Determination of trunk motion patterns associated with permanent or transient stenosis of the lumbar spine. Eur Spine J 5:332-337, 1996. Szpalski M, Parnianpour M: Trunk performance, strength and endurance: measurement techniques and applications. In JN Weinstein, SW Wiesel, eds: The lumbar spine. Philadelphia, 1996, WB Saunders. Tress BM, Hare WS: CT of the spine: are plain spine radiographs necessary? Clin Radiol 41:317-320, 1990. Verbeek J, Sengers MJ, Riemens L, Haafkens J: Patient expectations of treatment for back pain: a systematic review of qualitative and quantitative studies. Spine 29: 2309-2318, 2004. Waddell G, McCulloch JA, Kummel E, Venner RM: Nonorganic physical signs in low back pain. Spine 5:117-125, 1980. Werner EL, Laerum E, Ihlebaek C: How is the general practitioner managing the back pain? Tidsskr Nor Laegeforen 122:1800-1803, 2002. Wetzel FT, LaRocca SH, Lowery GL, Aprill CN: The treatment of lumbar spinal pain syndromes diagnosed by discography: lumbar arthrodesis. Spine 19(7):792-800, 1994. Willen J, Danielson B: The diagnostic effect from axial loading of the lumbar spine during computed tomography and magnetic resonance imaging in patients with degenerative disorders. Spine 26(23):2607-2614, 2001. Wilson IB, Dukes K, Greenfield S, Kaplan S, Hillman B: Patients’ role in the use of radiology testing for common office practice complaints. Arch Intern Med 161(2):256-263, 2001. Yelland M: Diagnostic imaging for back pain. Aust Fam Physician 33:415-419, 2004. Yrjämä M, Tervonen O, Vanharanta H: Ultrasonic imaging of lumbar discs combined with vibration pain provocation compared with discography in the diagnosis of internal anular fissures of the lumbar spine. Spine 21(5):571-575, 1996.
CHAPTER
4d
Treatment Options Margareta Nordin, Federico Balagué, and Christine Cedraschi
More than 17 guidelines drawn from large evidence-based systematic literature reviews have been published in different countries on low back pain (LBP),8,79,96 a topic that the World Health Organization included in their report, the Bone and Joint Decade 2000-2010.38,59,98 LBP remains a common affliction that is debilitating for the patient and expensive for the working individual and for society.31,70 This chapter gives an overview of treatment modalities for returning an individual to work during the course of acute to chronic LBP. The focus is on LBP that is nonspecific, where causality cannot be established and which is treated by a structured evidence-based approach to prevent disability and chronicity.
SPECIFIC AND NONSPECIFIC LBP The classification for pain in the lumbar spine used by clinicians is “specific” or “nonspecific,” depending on which of more than 60 diagnoses applies.
TREATMENT MODELS Two treatment models are commonly used in treating back pain: the medical model and the biopsychosocial model. Modern medicine uses the classic scheme, which implies that an interaction between the patient and an exposure leads to an illness complex.99 This model works well in dealing with SLBP. The procedures are to 1. Recognize patterns of symptoms and signs by history and examination; 2. Identify underlying injury or disease by investigation and diagnosis; 3. Treat underlying injury or disease by specific intervention; 4. Expect the patient to recover. Preferably applied to NSLBP, the biopsychosocial model identifies factors associated with delayed recovery for return to activity and, most often, return to work. The model calls for identification of symptoms and signs outside the traditional medical field such as beliefs, high perception of disability, kinesophobia, depression, stress, job dissatisfaction, anxiety, somatization, or lack of control.22,94 These contributing factors are treated with nontraditional medical approaches such as cognitive behavioral therapy (CBT) or ergonomic or occupational intervention. The biopsychosocial model in occupational health care helps to 1. Recognize the nonspecific nature of the back pain; 2. Identify underlying psychosocial and/or environmental factors; 3. Treat these factors with appropriate interventions; 4. Empower the patient to assume responsibility for managing a condition with possibly frequent recurrence.
Specific low back pain The common feature for specific low back pain (SLBP), the diagnosis in up to 2% of all early back pain cases, is a causal link between a structural pathology and the described experience of the patient (see Chapter 4c). SLBP may result from systemic disease, infection, injury, trauma, cauda equine, or structural deformity. Additionally, nerve root pain, which occurs in about 5% of the individuals seeking care early, includes diagnoses such as a disk prolapse or spinal stenosis. These conditions are treated with or without surgery and should be referred to a specialist for determination of care.6,8,57
Nonspecific low back pain Nonspecific low back pain (NSLBP), which afflicts 85-90% of all individuals seeking care, is a diagnosis of exclusion: No precise structure is identified as the cause. NSLBP is attributable to common diagnoses such as lumbago, myofascial syndromes, muscle spasms, mechanical LBP, back sprain, and back strain. These conditions all include pain in the lumbar region that may or may not radiate to one or both thighs but not below the knee(s). The following International Classification of Diseases diagnostic codes are suggested to best represent NSLBP: lumbago (724.2) and sprains of the lumbosacral region (846.0-3/8-9, 847.2-3).24
The first occupational health guidelines for the management of LBP at work were published in 2001 (see also www.facoccmed. ac.uk).96 These guidelines are based on an extensive systematic review of the scientific literature primarily in terms of occupational settings or outcomes.
PATIENT EXPECTATIONS A patient approaches a physician with expectations and preconceptions. The patient expects diagnostic explanation, pain relief, referral for treatment, instructions for coping with pain and disability, and, in an occupational environment, help with sickness certification or light duty assignment. Some patients expect imaging or special tests and specific medication. In one cross-sectional study (n = 1942), for example, 77% of the responders believed that if back pain exists, a wrong movement could lead to a serious problem. Forty percent believed also that radiographs and imaging could always identify the cause of back pain.40 It takes time to explain inappropriate concepts and expectations. The first encounter addresses such misconceptions, whereas at subsequent visits the important concepts for recovery are discussed and reinforced.69,91 Evidence-based information educates the patient that selective treatments may take time; some treatments may pose higher risks, and the effects of new treatments
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are not entirely known. The patient and clinician discuss the proposed treatment and the prospect of harm when work is resumed and agree on a regimen including compliance and return to work. Patient education about treatment choice and expected outcome is a key factor for success.49,97
NATURAL HISTORY AND RECURRENCE OF NSLBP Acute NSLBP has a favorable prognosis. Some authors argue that NSLBP is a lifetime disease if recovery has not occurred during the first 3 months,10,84,92 as is true for a large subgroup of individuals.48 Von Korff et al93 found that 20% of the U.S. population suffers from chronic LBP each year and that about 30% of them suffer chronic pain over their lifetimes. Studies focusing on the natural history of LBP report that 80% of patients who consult a health care provider for acute NSLBP can expect to resume normal activities within 4 to 6 weeks. By 12 weeks, the rate of recovery rises to almost 90%. Compared with approximately 35% to 40% of patients with SLBP, 10% or fewer of NSLBP patients experience chronic pain and work incapacity.1,11,70 The recurrence rate in NSLBP varies considerably from 5% to 70%, with up to 2 years follow-up in studies of both general and specific occupational populations.18,92 Recurrence or episode rate is difficult to estimate, however, because the definition of an episode is not standardized in different studies.29 We diagnose recurrent NSLBP when the employee has returned to regular work pain free for at least 8 weeks since the previous episode.71
on exercises and NSLBP, the authors concluded that “exercise therapy is as effective as either no treatment or other conservative treatments” in 11 trials involving 1192 adults.1,45,88 A series of five to six manipulations in the acute stage of NSLBP reduces pain and disability for up to almost 3 weeks.4,8,14,33 Alternatively, the patient may have a short course in pain management involving five to six encounters with a therapist trained in the biopsychosocial approach.61 In a comparison of manipulation and pain management in patients with acute NSLBP, the outcomes at 3 months and 12 months were almost identical (difference 0 [95% confidence interval (CI), -1.3-1.4]), with a decrease in disability score of about 8.8/24 points.44 With the patient maintaining tolerable activity, manipulations and pain management in acute NSLBP are superior to all passive modalities (mobilization, diathermy, massage, heat) over the long term.21,33 Continued passive longterm treatment of NSLBP is harmful because it precludes patient involvement, increases fear that the condition is serious, decreases cardiovascular conditioning, and reinforces the role of sick person.94 For the employee seeking care, the message is sometimes difficult to understand, particularly if the injury or back pain started at work. “Why should I go back to work, where I was injured, if it may hurt my back?” he or she asks. This legitimate question needs to be answered in relation to the type of job involved and the availability of modified work for a limited period if necessary. The occupational health care provider is best placed to answer this question and to adapt the employee’s duties if necessary.
Self-care for acute NSLBP DURATION OF PAIN AND TREATMENT GOALS The following definitions of LBP and duration since onset are used and well accepted: The duration of acute NSLBP is 0-4 weeks and that of subacute NSLBP is 4-12 weeks.1,8,33 Although episode definition is not standardized, intermittent or recurrent NSLBP is diagnosed when the patient is pain free or almost pain free between the bouts of pain.1 Chronic NSLBP is defined as a duration of pain longer than 12 weeks.1,8,17,33 The most important goal for acute LBP is a continuum of occupational care and identification of factors to prevent chronicity during the first 3 months after the patient seeks help. Management in occupational medicine can make a difference by providing regular follow-up and using a multidisciplinary approach to reinforce return to work with temporary job accommodations or, in some cases, job change.
ACUTE NSLBP AND EVIDENCE FOR TREATMENT Because acute NSLBP is largely self-limiting, minimal or no medical interventions are recommended for most patients.1,26,33,67,88,95 The most important message is for the patient to keep as active as tolerable without bed rest.1,33,67,73,74,88 Specific exercises are not needed and may also have a negative effect. In two systematic reviews and a recent meta-analysis
Self-care implies that the NSLBP patient can control symptoms and engage in behaviors necessary to reduce or alleviate them. Playing an active role in recovery, the patient decides what behaviors are tolerable. The message to remain as active as possible cannot be overemphasized.1,88 Self-care techniques include (but are not limited to) stretching and/or walking or using heat and/or ice or relaxation techniques72 when convenient for shortterm relief. Written evidence-based information is helpful to reinforce the good prognosis of NSLBP, explaining the biopsychosocial factors influencing recovery and offering instructions for self-care.16 Company-specific information may have a better impact than a generic pamphlet.46,75 In summary, systematic literature reviews, randomized controlled trials, and meta-analysis of acute NSLBP show that selfcare in the form of maintained activity, education, and medication as needed is as effective as manipulation or a short course of pain management based on the biopsychosocial model. Bed rest and passive treatment should be avoided. If patients demand treatment, it is prudent to ask about their expectations and goals, educate them, and reinforce the positive prognosis. The natural history of acute NSLBP measured as return to work is altered only marginally by prescribed treatment at this early stage, but together with self-care it provides shortterm relief from pain. Patients should be followed until they resume work.
Chapter 4d
INTERVENTIONS FOR SUBACUTE NSLBP The interval of 4-12 weeks in the management of NSLBP has been called “the window of opportunity.” The occupational health care professional can become instrumental in preventing work disability and recommending alternative and more intensive regimens of evidence-based treatment. A clinical reevaluation at 4 weeks includes a careful orthopedic and neurologic examination along with imaging and other diagnostics if warranted to exclude any ongoing process in the spine.8,33 If the diagnosis remains NSLBP, screening for psychosocial factors is warranted.
Yellow flags “Yellow flags”56 indicate psychosocial barriers to recovery and predict poor outcomes related to occupational health care because the patient does not return to any kind of work.55 Yellow flags are employee misconceptions (that back pain is harmful or can be severely disabling), avoidance of movement or activity due to fear of pain, tendency toward depression, withdrawal from social interaction, or expectation of continued passive treatment rather than belief that active participation will help.55,61 Six open-ended questions are helpful for revealing yellow flags: 1. Have you had time off work in the past with back pain? 2. What do you understand to be the cause of your back pain? 3. What do you expect will help you? 4. How is your employer responding to your back pain? Your coworkers? Your family? 5. What are you doing to cope with your back pain? 6. Do you believe you will return to work? When?
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In one study from a primary care cohort (n = 800) over 5 years, not recognizing psychosocial issues early on has been shown to account for an increase of 10 consultations per year per patient.52
Blue flags In occupational health care it is also helpful to recognize so-called “blue flags” that are related to possible work problems. Initially proposed by Main and coworkers,7,65,66 blue flags represent occupationally related predisposing factors for delayed recovery and return to work. Blue flags include factors such as fear of losing one’s job, monotony at work, lack of job satisfaction, and poor relationships with peers and supervisors. Occupational health care professionals are particularly well placed to address these issues. Appropriate intervention such as CBT aims to strengthen the employee’s coping skills and problem solving. In collaboration with the occupational physician, a discussion with supervisors or a workplace visit can occur early in the course of back pain to prevent chronicity. An active approach combining patient participation with involvement by the health care provider, the management, and the union is beneficial.60,62,81
Management of NSLBP The management of subacute NSLBP treatment should proceed in a stepwise fashion from least to the most invasive treatment (Fig. 4d.1). There is weak to moderate evidence in randomized controlled trials for efficacy of a treatment regimen including exercise, behavioral therapy, and ergonomic intervention.33,70 The employee must be convinced to participate actively to prevent long-term chronicity and disability. Meaningful outcomes for the patient that need to be discussed are those of taking control of
Work disability in %
100
50
• Convey optimism • Stay active • Pain medication • Self care techniques • Follow-up • Pamphlet/information
0
1 month Acute
Figure 4d.1
• Convey optimism • Exercise • Pain medication • Psychological evaluation and possible cognitive behavoral treatment • Work conditioning program • Ergonomic and/or occupational intervention
>6 months
3 months Subacute
Suggested management of occupational nonspecific low back pain.
• Exercise • Aggressive pain management • Cognitive behavoral treatment • Multidisciplinary conditioning program with focus on return to work • Workplace intervention • Surgery (?)
Early chronic
Chronic
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the condition; feeling better; resuming activities, including work; and avoiding recurrences. Because compliance with regimens requires the patient’s active participation, management of subacute NSLBP is demanding. Compliance rates for different regimens have been reported to vary from 13% to 85%,2,61 and a patient’s decision to adhere to a treatment regimen is complex.50 Patients may prefer passive treatment that may delay the course of recovery.83 One study has shown, for example, that patient compliance with video watching for back education (70-80%) in a physical therapy practice was significantly higher than compliance with a more demanding exercise regimen (40-50%).2 Linton and Andersson61 indicated an adherence rate of 53% and 72% for six and four CBT sessions, respectively. Adherence appears to be influenced by both the type of treatment and its frequency. The stepwise active approach includes an exercise regimen or a CBT program as a single intervention or a combination of the two as a bimodal treatment if no recovery occurs.
Exercise regimens The message here is for the patient to “start moving” with or without help from a coach. There are many different types of exercise regimens for LBP, each with its own proponents. Exercise programs evaluated in randomized controlled trials include the McKenzie regimen, walking programs, Williams flexion exercises, endurance-strength-stabilization training, and other less frequently described regimens.23,27,43,47,54 Different types of exercises appear to be equally effective.1,87 A recent meta-analysis of five exercise studies involving about 800 patients resulted in pooled weighted difference decrease in pain of about two points (1.89 [95% CI, -1.13 to 4.91) on a scale of 100. Pooling four trials demonstrated an improvement of 1.07 (95% CI, -3.18 to 5.32) points on a scale of 100 for perceived functional outcomes.45 The authors concluded that the evidence is insufficient to refute or support the effectiveness of regimens involving exercise alone without a behavioral component.
Cognitive behavioral therapy CBT interventions include creative visualization, imagery, progressive muscle relaxation, problem solving, and other techniques. The clinician uses the components in various combinations to have the patient understand, accept, and take control of the back pain. Moderate to strong evidence indicates that CBT should be used early if biopsychosocial signs or symptoms are present, and strong evidence exists for using CBT in patients with chronic NSLBP.33,87,96 The European Guidelines 2005 stated, “We recommend cognitive-behavioural treatment for patients with chronic LBP,” and summarized as follows: There is strong evidence that behavioural treatment is more effective for pain, functional status, and behavioural outcomes than placebo/no treatment/waiting list control. There is strong evidence that a graded activity programme using a behavioural approach is more effective than traditional care for returning patients to work, and finally there is strong evidence that there is no difference in effectiveness between the various types of behavioural therapy.33
Combination therapy in occupational settings Three studies in occupational settings have found that a behaviorally oriented graded-activity exercise program provides moderate to excellent reduction of days lost at work. This type of program has been compared to usual care in the Netherlands and in Sweden.60,81,86 These studies had highly structured interventions with an unambiguous primary goal of returning the patient to work. A behaviorally oriented graded-activity exercise program includes the following components: 1. The occupational or treating physicians advise workers on ergonomics, prevention, and return to work schedules; 2. The clinicians also advise and communicate with interested parties such as health care providers and workplace representatives; 3. The programs use gradually progressive exercises adapted to patient needs; 4. The clinical team is trained, and all caregivers provide the same message to the patient to avoid ambiguity; 5. There is ample communication and discussion with the patient; 6. An ergonomic intervention such as a workplace visit or a discussion with the occupational physician may be included.60,62 The studies showed significant reduction in days of work loss. Lindstrom et al,60 for example, showed an average return to work in the intervention group at 10 weeks (standard deviation, 12.7) and in the control group at 15.1 weeks (standard deviation, 15.6). Staal et al80 showed an effect on work loss days (HR 1,9; CI, 1.2-3.2) at 50 days after randomization in favor of the graded-activity program. However, the results were not significant in early follow-up less than 50 days after treatment for the two interventions (an exercise program and a graded operant conditioning program). One randomized controlled trial in an occupational setting in the Netherlands added problem-solving therapy conducted by a trained therapist to a behaviorally oriented graded-activity exercise program for patients with subacute and chronic NSLBP. The combination group showed significantly favorable results, including fewer work loss days and fewer patients receiving disability pensions 1 year after the intervention.86 In all studies, self-reported pain and function were affected marginally.60,80,86 Usually measured by a pain score or visual analog scale, pain itself appeared not to be a major determinant for return to work. Possibly the highly structured positive environment in an occupational setting provides a better venue for problem solving, educating the patient, and monitoring progress.
Ergonomic intervention Using the Sherbrooke model of occupational/ergonomic intervention and clinical rehabilitation, Loisel et al62 found that a consultation with an occupational physician or a low-cost ergonomic intervention contributed the most to the success of return to work. In a follow-up study of cost effectiveness 6.4 years later, the same authors found that the Sherbrooke model yielded the highest savings in work loss days compared with standard care or rehabilitation alone.64 The authors assessed participatory ergonomics in workers
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suffering from subacute LBP (>6 weeks of work disability). Performed 6 months after the ergonomic intervention, the assessment included all parties: management, union, and afflicted worker. About half of the recommended ergonomic solutions were implemented with a substantial agreement among all respondents.63 The Cochrane review of multidisciplinary biopsychosocial rehabilitation concluded, “There is moderate evidence showing that multidisciplinary rehabilitation for subacute LBP is effective and that a work site visit increases the effectiveness.”53 These findings must be interpreted with caution, however, because the few studies reviewed contained methodologic flaws and need to be confirmed. Based on several studies of patients with chronic back pain, the European Guidelines 2005 recommend an occupational intervention.33
MULTIMODAL PROGRAMS FOR CHRONIC LBP Two recent reviews and one systematic Cochrane review of chronic NSLBP showed the importance of multimodal active programs.9,10,19,39,42 The Cochrane review covered 18 trials, including 1964 chronic NSLBP patients (Fig 4d.2).53,87 The comparison included treatment such as back training, exercise only, education, standard care, assessment by specialist with or without a nurse and/or advisement (oral and printed), waiting lists, and other factors. Like the European Guidelines 2005, the review concluded, “There is strong evidence that intensive multidisciplinary biopsychosocial rehabilitation for chronic NSLBP with a functional restoration approach reduces pain when compared with inpatient or out-patient nonmultidisciplinary treatments and moderate evidence when these programs are compared to usual care. There is contradictory evidence regarding global vocational outcomes.”42 The authors cautioned about the lack of definition concerning content, duration, and intensity of the programs but found that those longer than 100 hours of therapy with a focus on functional restoration seem to be more effective than less intensive programs or nonmultidisciplinary control groups. The review indicated significant and favorable results for pain ratings, functional status, employment status, and sick leave up to 60 months.
MANIPULATION Manipulation has been evaluated extensively for chronic LBP and studied less in the subacute phase. A recent pragmatic randomized trial, however, included 181 general practices in the United Kingdom with 1334 patients, most of whom had subacute NSLBP. Patients were randomized to groups of standard best care or manipulation, each with or without exercise, and followed for 1 year.85 Results on the Roland Morris disability questionnaire76-78 improved with a mean of 3.3 (standard deviation, 4.5) and 3.5 (standard deviation, 4.7) points out of a total score of 10 points at 3 and 12 months, respectively. A score change of 20% is deemed clinically significant.10 The difference between the groups was nonsignificant. Manipulation for chronic NSLBP was reviewed extensively by Assendelft et al,4 Bronfort and Bouter,13 and Cherkin et al.25 In a
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meta-analysis, Cherkin et al compared sham manipulation, traction, corset, bed rest, home care, topical gel, diathermy, massage, general practitioner care, analgesics, physical therapy, exercises, back training, no treatment, or some combination thereof. They found no evidence that spinal manipulation is substantially more or less effective than other conventional therapies for chronic NSLBP. The expected gain in pain reduction is 4-5 points (ranging from -4 to 12) on a 100-mm visual analog scale for pain of longterm duration and somewhat less for self-reported disability. These measures were reported for both the short and the long term.25 A UCLA study (n = 681) included about 50% patients with chronic NSLBP in a managed care health organization. The patients were randomized to chiropractic, medical, or physiotherapy care, and at a 6-month follow-up the results were comparable.51 Chiropractic care in combination with physical modalities or physical therapy modalities provided in combination with medical care did not produce clinically significant improvements in outcome.58 The European Guidelines 200533 recommend a short course of spinal manipulation/mobilization as a treatment option for chronic LBP. They also summarize the evidence for medication use as follows.
MEDICATION Nonsteroidal antiinflammatory drugs (NSAIDs) The usefulness of nonsteroidal antiinflammatory drugs (NSAIDs) was reviewed systematically by van Tulder et al,89 who highlighted the methodologic problems they encountered. Most of the published trials reported on acute LBP. In comparison with placebo, the authors found “conflicting evidence” that NSAIDs provided better pain relief, but patients on NSAIDs exhibited significantly less use of analgesics. There were no significant differences in terms of side effects. In the same review, “conflicting results” were found among studies comparing NSAIDs with paracetamol. Included in the same systematic review were six studies comparing NSAIDs with narcotic analgesics or muscle relaxants. The authors found “moderate evidence” that NSAIDs are not more effective than other drugs. van Tulder et al89 highlighted the impossibility of making any statement about the relative effectiveness of different NSAID types because no studies comparing the same two drugs for acute or chronic LBP were available.
Muscle relaxants Benzodiazepine and nonbenzodiazepine muscle relaxants, either isolated or combined with other drugs, have been extensively investigated in LBP. A systematic review of this literature was published by van Tulder et al.90 Limited evidence from one study favored diazepam (an intramuscular injection followed by 5 days of oral treatment) versus placebo. The authors found strong evidence both that oral nonbenzodiazepines are more effective than placebo for short-term pain relief and that both types of muscle relaxants are associated significantly more than placebo with central nervous system side effects. Because the number of high-quality studies comparing different muscle relaxants is
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Treatment options
Trial characteristics
Time since treatment
Pain record
Functional status
Days on sickness leave
Employment status
Intensive (>100h) daily MBPSR with functional restorative: Alsants 1994* v >100h inpatient rehabilitation
3 months 12 months
Bendix 1995:1* v < 30h outpatient rehabilitation
4 months 12 months 24 months 60 months
Bendix 1990 v usual care
4 months 24 months 60 months
Michel 1994* v usual care
4 months 12 months 24 months
Less intensive (<30h) once or twice daily outpatient MBPSR: Bazier 1997 v outpatient rehabilitation
At treatment completion
Bendix 1995:2* v <10h outpatient rehabilitation
6 months 12 months 24 months 30 months
Nichols 1991* v < 30h outpatient rehabilitation
6 months 12 months
Nichols 1992* v < 30h outpatient rehabilitation
6 months
Martapea 1989:2 v usual care
3 months 12 months 30 months 54 months
Other types of MBPSR: Martapea 1989:1 Inpatient MBPSR >108h (no functional restoration) v usual care
3 months 12 months 30 months 54 months
Juckel 1990 Sμ type MBPSR v waiting list
At treatment completion
Uritias 1989* Individualized inpatient MBPSR v usual care
12 months
–2 –1
0
1
Standardized mean difference
2
–2 –1
0
1
Standardized mean difference
2
0.1
1 Relative risk
10
–2 –1
0
1
2
Standardized mean difference
Figure 4d.2 Treatment effect sizes for 12 randomized comparisons of multidisciplinary biopsychosocial rehabilitation and a control condition. Bars represent standardized mean differences and 95% confidence intervals for comparison of intervention and control groups, except for employment status, where bars represent relative risks. Treatment effect sizes entirely to the left of the vertical line indicate statistically significant differences in favor of the intervention. *, High quality trial; I1, intervention 1 testing more than one multidisciplinary intervention; I2, intervention 2 testing more than one multidisciplinary intervention; MBSPR, multidisciplinary biopsychosocial rehabilitation.
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rather limited, it seems very difficult to make general recommendations in this area. There is strong evidence that combining tizanidine plus paracetamol or tizanidine plus NSAIDs is more effective for short-term pain relief than placebo plus paracetamol or plus NSAIDs. Two high-quality trials offer strong evidence that temazepam 50 mg 3 times a day is more effective than placebo for short-term pain relief and overall improvement. When the literature review was published, however, this drug was available only in some European countries and Mexico. Among the nonbenzodiazepines, there is moderate evidence that flupirtine and tolperisone are more effective than placebo for short-term improvement.90
Opioids Breckenridge and Clark12 and Fillingim et al35 independently showed that the use of opioids in chronic LBP patients was not predicted by pain intensity. Therefore, the factors influencing health care providers to prescribe opioids probably deserve more research.
Antidepressants The efficacy of antidepressants in chronic LBP was systematically reviewed by Staiger et al.82 Based on the seven studies reviewed, the authors concluded that tricyclic and tetracyclic antidepressants can produce moderate symptom reductions. Inhibition of norepinephrine reuptake seems important for the analgesic effect. Benefits appear to be independent of a patient’s depression. Selective serotonin reuptake inhibitors were evaluated in three studies that failed to show any analgesic effect. It remains unclear whether these drugs affect functional status.
Corticosteroids In their review, Atlas and Nardin5 stated that evidence supporting the use of oral corticosteroids is lacking. Because these drugs have potential significant side effects, the authors therefore advised against their use in patients with chronic pain.
SURGERY Chronic NSLBP would imply LBP without sciatica in patients with degenerative disk diseases.30 Although shown to be controversial, the diagnosis itself is usually made by provocative diskography at the level of the disk possibly causing the pain.19,20 An et al3 discussed disk degenerative progressive changes as part of normal aging. Studies today cannot confirm what starts and what influences progression if no trauma or disease is present. There is also debate about the disk as a pain source; from a clinical perspective, however, severe disk degeneration on several levels is shown to cause pain. Moderate to less visible disk degeneration changes are more debatable. The authors argued for investigating other sources of pain as well as its enhancers or modifiers. A systematic literature review in 1999 concluded that there was insufficient evidence for lumbar spine fusion in lumbar
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Surgery
spondylolysis and back pain.39 Three randomized trials have since shown that long-term benefits for surgery over 2 years is comparable with those of nonsurgical treatments.15,35,37 In a large randomized controlled study, Fritzell et al36,37 compared fusion with usual conservative care in patients (n = 294) with one- or two-level disk degeneration and pain duration of at least 1 year. The surgical group had a greater improvement in pain relief, function, depressive symptoms, and return to work at 1-year follow-up compared with those who had common conservative treatment prescribed by a physician. At 2-years follow-up, the difference between the groups had diminished, suggesting that the results of fusion are intermediary rather than long term. The heterogeneous therapy in the nonsurgical treatment may also have contributed to a less favorable result in the nonsurgical group. The nonsurgical group received a variety of treatments according to individual physician preferences such as acupuncture, physical therapy, injections, electrical stimulation, and CBT. The study did not have blinded evaluators. In a smaller randomized trial, 64 patients aged 25-60 years with NSLBP lasting longer than 1 year and evidence of disk degeneration at L4-L5 and/or L5-S1 at radiographic examination were randomized to either lumbar fusion with posterior transpedicular screws and postoperative physiotherapy or cognitive intervention and exercises.15 The cognitive intervention consisted of a lecture to help patients understand that ordinary physical activity would not harm the disk and a recommendation to use the back and bend it. This was reinforced by three daily physical exercise sessions for 3 weeks. The main outcome measure was the Oswestry Disability Index. At a 1-year follow-up visit to 97% of the patients, the Oswestry Disability Index was significantly reduced from 41/100 to 26/100 points after surgery, compared with 42/100 to 30/100 points after cognitive intervention and exercises. The mean difference between the groups of 2.3 points (-6.7 to 11.4; p = 0.33) was not significant. Improvements in back pain, use of analgesics, emotional distress, life satisfaction, and return to work were not different. Fear-avoidance beliefs and fingertip-floor distance were reduced more after nonoperative treatment, and lower limb pain was reduced more after surgery. According to an independent observer, the success rate was 70% after surgery and 76% after cognitive intervention and exercises. The early complication rate in the surgical group was 18%. The authors concluded that the main outcome measure showed equal improvement in patients with chronic LBP and disk degeneration randomized to lumbar fusion or cognitive intervention and exercises.15 The risk for the nonsurgical group was considerably lower, however, because no complications occurred. Although the evidence is less compelling than it might have been, in the future these patients may be offered surgery or CBT with similar results. This study needs to be confirmed by other and larger studies, but it may provide an alternative to surgery when expected outcomes from that treatment are uncertain. In a multicenter study from Great Britain,34 349 patients with chronic back pain lasting more than 1 year were randomized to surgery (spinal fusion) or to an intensive rehabilitation program for 5 days a week for 3 weeks continuously and followed for 2 years. The team included a physician, a physical therapist, and a psychologist. The program was individually tailored to each patient with progressive exercises and CBT to overcome fears and negative beliefs about back pain. Both groups reported
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reductions in disability, and the only primary outcome measure that marginally favored surgery was the Oswestry Disability Index, which showed a clinically insignificant decrease of about four points on a scale of 100 (-.1 [95% CI, -4.1 to -0.1; p = 0.045). No clear evidence emerged that primary spinal fusion was any more beneficial than intensive rehabilitation. Randomized controlled trials on novel technology such as artificial disks, electrothermal therapy, analgesic pumps, and implanted stimulators are lacking. One systematic literature review stated, “There is no evidence that disk replacement reliably, reproducibly, and over longer periods of time fulfills the three primary aims of clinical efficacy, continued motion, and few adjacent segment degenerative problems. Total disk replacement seems to be associated with a high rate of re-operations, and the potential problems that may occur with longer follow-up have not been addressed.”28 Arthroplasty and fusion or laminectomy have been compared in randomized clinical trials with similar outcomes.41,68 In these studies no nonsurgical groups were included for comparison, as is greatly needed. In patients with chronic NSLBP, the current evidence points to improved triage and a stepwise active approach in which the patient and clinician discuss goals, outcomes, and compliance with the proposed treatment.
COMPLICATIONS AND TREATMENT CHOICE
REFERENCES 1.
2.
3. 4.
5. 6. 7.
8.
9. 10. 11.
12.
We could not find any complications reported in therapies including exercise, CBT, or workplace intervention. The complication rate for spinal surgery varies by type from 2% to 15%, including instrument failure, prosthetic migration, infection, chronic pain, and neural injuries or/and pulmonary embolus. When advising a patient, this information can be used for education to help with choice of treatment.
13.
SUMMARY
17.
This chapter summarizes evidence-based management and treatment regimens for patients seeking care for LBP and diagnosed with NSLBP. In acute NSLBP there is strong to moderate evidence for self-care by taking over-the-counter medication and maintaining activity as tolerated or engaging in limited sessions of manipulative therapy. In subacute NSLBP, there is weak to moderate evidence for a graded activity program, including a combination of exercise and CBT. Strong evidence indicates that these programs reduce work absenteeism. In NSLBP of more than 12 weeks’ duration, a variety of regimens seems to be available with limited and similar efficacy on pain and disability reduction. There is weak to moderate evidence that interventions, including CBT, exercise, and education about chronic NSLBP, are as effective as surgery after 2 years of followup. Surgical indications for chronic NSLBP are ill-defined.
14.
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25.
26.
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ACKNOWLEDGMENT 29.
We thank Chaitrali Gore, M.S., for her excellent help with references and figures.
30.
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Fritzell P, Hagg O, Jonsson D, Nordwall A: Cost-effectiveness of lumbar fusion and nonsurgical treatment for chronic LBP in the Swedish Lumbar Spine Study: a multicenter, randomized, controlled trial from the Swedish Lumbar Spine Study Group. Spine 29:421-434, 2004. Fritzell P, Hagg O, Wessberg P, Nordwall A: Lumbar fusion versus nonsurgical treatment for chronic LBP: a multicenter randomized controlled trial from the Swedish Lumbar Spine Study Group, 2001 Volvo Award Winner in Clinical Studies. Spine 26: 2521-2532, 2001. Garfin SR, Andersson G, Gronblad M, et al: The Bone and Joint Decade, 2000-2010, for prevention and treatment of musculoskeletal disorders. Spine 24(11): 1055-1057, 1999. Gibson JN, Grant IC, Waddell G: The Cochrane review of surgery for lumbar disc prolapse and degenerative lumbar spondylosis. Spine 24:1820-1832, 1999. Goubert L, Crombez G, De Bourdeaudhuij I: Low back pain, disability and back pain myths in a community sample: prevalence and interrelationships. Eur J Pain 8: 385-394, 2004. Guyer RD, McAfee PC, Hochschuler SH, et al: Prospective randomized study of the Charite artificial disc: data from two investigational centers. Spine 4:252S-259S, 2004. Guzman J, Esmail R, Karjalainen K, et al: Multidisciplinary rehabilitation for chronic LBP: systematic review. BMJ 322:1511-1516, 2001. Hansen FR, Bendix T, Skov P, et al: Intensive, dynamic back-muscle exercises, conventional physiotherapy, or placebo-control treatment of low-back pain. A randomized, observer-blind trial. Spine 18:98-108, 1993. Hay EM, Mullis R, Lewis M, et al: Comparison of physical treatments versus a brief pain-management programme for back pain in primary care: a randomised clinical trial in physiotherapy practice. Lancet 365:2024-2030, 2005. Hayden JA, van Tulder MW, Malmivaara AV, Koes BW: Meta-analysis: exercise therapy for nonspecific LBP. Ann Intern Med 142:765-775, 2005. Hazard RG, Reid S, Haugh LD, McFarlane G: A controlled trial of an educational pamphlet to prevent disability after occupational low back injury. Spine 25: 1419-1423, 2000. Helmhout PH, Harts CC, Staal JB, Candel MJ, de Bie RA: Comparison of a high-intensity and a low-intensity lumbar extensor training program as minimal intervention treatment in LBP: a randomized trial. Eur Spine J 13:537-547, 2004. Hestbaek L, Leboeuf-Yde C, Engberg M, et al: The course of LBP in a general population: results from a 5-year prospective study. J Manip Physiol Ther 26:213-219, 2003. Heymans MW, van Tulder MW, Esmail R, Bombardier C, Koes BW: Back schools for nonspecific low-back pain. Cochrane Database Syst Rev, CD000261, 2004. Hiebert R: Factors influencing patient compliance with medically recommended care for work disabling, non-specific, low back pain during acute and subacute phases. Masters of Science (Sc.M.) thesis. Baltimore, 2004, Johns Hopkins School of Hygiene and Public Health, Department of Health Policy and Management. Hurwitz EL, Morgenstern H, Harber P, et al: A randomized trial of medical care with and without physical therapy and chiropractic care with and without physical modalities for patients with LBP: 6-month follow-up outcomes from the UCLA LBP study. Spine 27:2193-2204, 2002. Kapur N, Hunt I, Lunt M, et al: Psychosocial and illness related predictors of consultation rates in primary care—a cohort study, Psychol Med 34:719-728, 2004. Karjalainen K, Malmivaara A, van Tulder M, et al: Multidisciplinary biopsychosocial rehabilitation for subacute LBP in working-age adults: a systematic review within the framework of the Cochrane Collaboration Back Review Group. Spine 26:262-269, 2001. Kellet J: Support groups: caring about each other. Nurs Stand 5:46, 1991. Kendall NA: Psychosocial approaches to the prevention of chronic pain: the low back paradigm. Baillieres Best Pract Res Clin Rheumatol 13:545-554, 1999. Kendall NA, Linton S, Main C: Guide to assess psychosocial yellow flags in acute LBP: risk factors for long-term disability and work loss. Wellington Accident Rehabilitation and Compensation Insurance of New Zealand, 1997, National Health Committee. Koes BW, van Tulder MW, Ostelo R, Kim BA, Waddell G: Clinical guidelines for the management of LBP in primary care: an international comparison. Spine 26: 2504-2513, 2001. Kominski GF, Roby DH, Kincheloe JR: Cost of insuring California’s uninsured. Policy Brief: UCLA Cent Health Policy Res 1-6, 2005. Lidgren L: The bone and joint decade 2000-2010. Bull World Health Org 81(9):629, 2003.
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Lindstrom I, Ohlund C, Eek C, et al: Mobility, strength, and fitness after a graded activity program for patients with subacute LBP: a randomized prospective clinical study with a behavioral therapy approach. Spine 17:641-652, 1992. Linton SJ, Andersson T: Can chronic disability be prevented? A randomized trial of a cognitive-behavior intervention and two forms of information for patients with spinal pain. Spine 25:2825-2831, 2000. Loisel P, Abenhaim L, Durand P, et al: A population-based, randomized clinical trial on back pain management. Spine 22:2911-2918, 1997. Loisel P, Gosselin L, Durand P, et al: Implementation of a participatory ergonomics program in the rehabilitation of workers suffering from subacute back pain. Appl Ergon 32:53-60, 2001. Loisel P, Lemaire J, Poitras S, et al: Cost-benefit and cost-effectiveness analysis of a disability prevention model for back pain management: a six year follow up study. Occup Environ Med 59:807-815, 2002. Main C, Glozier N, Wright I: Validity of the HSE stress tool: an investigation within four organizations by the Corporate Health and Performance Group. Occup Med (Lond) 55:208-214, 2005. Main CJ: Early psychosocial interventions for LBP in primary care. BMJ 331:88, 2005. Malmivaara A, Hakkinen U, Aro T, et al: The treatment of acute LBP—bed rest, exercises, or ordinary activity? N Engl J Med 332:351-355, 1995. McAfee PC, Fedder IL, Saiedy S, Shucosky EM, Cunningham BW: Experimental design of total disk replacement-experience with a prospective randomized study of the SB Charite. Spine 28:S153-S162, 2003. McGuirk B, King W, Govind J, Lowry J, Bogduk N: Safety, efficacy, and cost effectiveness of evidence-based guidelines for the management of acute LBP in primary care. Spine 26:2615-2622, 2001. Nachemson A, Jonsson E: Neck and back pain: the scientific evidence of causes, diagnosis and treatment. Philadelphia, 2000, Lippincott Williams & Wilkins. Nordin M, Skovron ML, Hiebert R, et al: Early predictors of delayed return to work in patients with LBP. J Musculoskel Pain 5:5-27, 1999. Nordin M, Weiser S, Campello MA, Pietrek M: Self care techniques for acute episodes of LBP. Best Pract Res Clin Rheumatol 16:89-104, 2002. Oleske DM, Neelakantan J, Andersson GB, et al: Factors affecting recovery from workrelated, low back disorders in autoworkers. Arch Phys Med Rehabil 85:1362-1364, 2004. Proper KI, Staal BJ, Hildebrandt VH, van der Beek AJ, van Mechelen W: Effectiveness of physical activity programs at worksites with respect to work-related outcomes. Scand J Work Environ Health 28:75-84, 2002. Roberts L, Little P, Chapman J, et al: The back home trial: general practitioner-supported leaflets may change back pain behavior. Spine 27:1821-1828, 2002. Roland M, Morris R: A study of the natural history of back pain. Part I: development of a reliable and sensitive measure of disability in low-back pain. Spine 8:141-144, 1983. Roland M, Morris R: A study of the natural history of low-back pain. Part II. Development of guidelines for trials of treatment in primary care. Spine 8:145-150, 1983. Roland M, Fairbank J: The Roland-Morris Disability Questionnaire and the Oswestry Disability Questionnaire. Spine 25:3115-3124, 2000. Spitzer WO, Leblanc FE, DuPuis M: Scientific approach to the assessment management of activity-related spinal disorders: a monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 12(7 Suppl):S1-S59, 1987. Staal JB, Hlobil H, Twisk JW, et al: Graded activity for LBP in occupational health care: a randomized, controlled trial. Ann Intern Med 140:77-84, 2004. Staal JB, Hlobil H, van Tulder MW, et al: Return-to-work interventions for LBP: a descriptive review of contents and concepts of working mechanisms. Sports Med 32:251-267, 2002. Staiger TO, Gaster B, Sullivan MD, Deyo RA: Systematic review of antidepressants in the treatment of chronic LBP. Spine 28:2540-2545, 2003. Thomas E, Croft PR, Paterson SM, Dziedzic K, Hay EM: What influences participants’ treatment preference and can it influence outcome? Results from a primary carebased randomised trial for shoulder pain. Br J Gen Pract 54:93-96, 2004. Thomas E, Silman AJ, Croft PR, et al: Predicting who develops chronic LBP in primary care: a prospective study. BMJ 318:1662-1667, 1999. United Kingdom back pain exercise and manipulation (UK BEAM) randomised trial: effectiveness of physical treatments for back pain in primary care. BMJ 329(7479): 1377, 2004. van den Hout JH, Vlaeyen JW, Heuts PH, Zijlema JH, Wijnen JA: Secondary prevention of work-related disability in nonspecific LBP: does problem-solving therapy help? A randomized clinical trial. Clin J Pain 19:87-96, 2003. van Tulder MW et al: Behavioural treatment for chronic LBP. The Cochrane Library, Issue 3. Chichester, UK, 2004, John Wiley & Sons, Ltd. van Tulder MW, Ostelo R, Vlaeyen JW, et al: Behavioral treatment for chronic LBP: a systematic review within the framework of the Cochrane Back Review Group. Spine 25:2688-2699, 2000. van Tulder MW, Scholten RJ, Koes BW, Deyo RA: Nonsteroidal anti-inflammatory drugs for LBP: a systematic review within the framework of the Cochrane Collaboration Back Review Group. Spine 25:2501-2513, 2000.
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van Tulder MW, Touray T, Furlan AD, Solway S, Bouter LM: Muscle relaxants for nonspecific LBP: a systematic review within the framework of the Cochrane Collaboration. Spine 28:1978-1992, 2003. Verbeek J, Sengers MJ, Riemens L, Haafkens J: Patient expectations of treatment for back pain: a systematic review of qualitative and quantitative studies. Spine 29:2309-2318, 2004. Vingard E, Mortimer M, Wiktorin C, et al: Seeking care for LBP in the general population: a two-year follow-up study: results from the MUSIC-Norrtalje Study. Spine 27: 2159-2165, 2002. Von Korff M, Crane P, Lane M, et al: Chronic spinal pain and physical-mental comorbidity in the United States: results from the national comorbidity survey replication. Pain 113:331-339, 2005.
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Waddell G: The back pain revolution. New York, 1999, Churchill Livingstone. Waddell G, Burton AK: Concepts of rehabilitation for the management of LBP. Best Pract Res Clin Rheumatol 19:655-670, 2005. 96. Waddell G, Burton AK: Occupational health guidelines for the management of LBP at work: evidence review. Occup Med (Lond) 51:124-135, 2001. 97. Weinstein JN: Doctor and patient: advocacy for informed choice vs. informed consent. Spine 30(3):269-272, 2005. 98. Weinstein SL: 2000-2010: the bone and joint decade. J Bone Joint Surg 82A(1): 1-3, 2000. 99. Wood P: The basis of rheumatological practice, including nomenclature and classification. In JT Scott, ed: Copeman’s textbook of Rheumatic Diseases. New York, 1986, Churchill Livingston, p. 59.
CHAPTER
4e
Workplace Adaptation for the Low Back Region Shrawan Kumar and Steve Konz
THE NATURE OF LOW BACK PAIN The nature of low back pain (LBP) and even its broad categorization into acute, subacute, and chronic categories defy scientific precision. In many cases, its insidious onset, relief without medical intervention, recurrence despite all precautions, and eventual chronicity have not only perplexed medical practitioners but also posed an intellectual challenge even for a scientific conception of the phenomenon. Although many risk factors have been associated with LBP, its etiology remains obscure. Kumar14 categorized all known risk factors into four broad categories: (1) morphologic, (2) genetic, (3) biomechanical, and (4) psychosocial. He stated that whereas morphologic and genetic factors are hardly manipulable, the biomechanical and psychosocial factors lend themselves to manipulation. It was, however, conceded that all strategies must take into account the genetic and morphologic data for optimal results. Many studies have been conducted to examine the possible impact of different risk factors, but the human back is like a multilink chain that is only as strong as its weakest link. Unfortunately, the weakest link is most elusive, being different in different people and also at different times in the same individual because of varying internal and external circumstances.
CAUSAL MECHANISMS AND CONTROL Humans have evolved over millions of years into what they are today. Evolutionary pressures and consequent speciation resulted in an upright biped creature with dextrous upper limbs and a highly evolved brain. For a large duration of its existence, the species relied on hunting and gathering as its primary means of sustenance.5 With the advancement of science, technology, and industrialization, the physical occupational stresses have changed dramatically in an evolutionary “flash” so that none of the body systems that one uses today was either designed or evolved for the current purpose. As a result, demand for force exertion, activity repetition, or posture assumption for prolonged periods places stress on human physical systems that is inherently unnatural. This is further aggravated by many psychologic stresses emanating from financial or interpersonal factors. In addition, most human occupations have become complex, requiring significant organization and thereby enhancing the chances of errors. As a function of a multivariate complex system (in many cases under multiple partial controllers), significant
chances emerge for unplanned events. These then result in various kinds of accidents with property damage and/or personal injuries. A meaningful attempt to control such injuries makes it imperative to understand them. Most cases compensated by the Workers’ Compensation Board are regional musculoskeletal problems. Workers in different economic sectors generally have injuries characteristic of those sectors. People in forestry, construction, and manufacturing have a higher proportion of back injuries. Those working in office jobs involving keyboarding have cumulative trauma disorders (also called musculoskeletal disorders and repetitive strain injuries). Because heavy physical workers do not develop repetitive strain or injury of the upper extremity and office workers do not injure their backs, the argument can be made that the nature of the physical stress and the region enduring the load largely determine the affected area and probably the nature of injury. If therefore one could delineate the mechanisms of injuries and the quantitative details of the relevant variables, one might develop a more effective intervention. An effective intervention would result in better control of injuries, which clearly has a significant payoff. Thus, the long-term success in controlling these injuries depends on understanding their causality. Because for ethical reasons human beings cannot be subjected to controlled experiments exposing them to risk of injury, Kumar et al16 performed an integrative synthesis of information in the scientific literature to formulate biologically plausible theories as to the mechanisms of injury causality. Through this exercise they proposed four theories of musculoskeletal injury causality described briefly below. 1. The Cumulative Load Theory16: Because biologic tissues are composed of both solid and liquid, their combined mechanical behavior or viscoelasticity is determined largely by the proportion of these components. Biologic tissues therefore deform partially like solids and partially like liquids in a blended manner. Such properties are time dependent: a longer exposure to the same load will produce larger deformation and vice versa. As a result, recovery from deformation takes time also. If the succeeding load does not allow sufficient recovery time, the tissue begins to deform further from its compromised stage. As demonstrated by Kumar13 in an epidemiologic study, repeated loading results in a cumulative effect of reduced threshold to failure. 2. The Differential Fatigue Theory16: Occupational tasks are kinesiologically complex and hardly ever performed in one plane. Asymmetric activities requiring the use of many body parts of the bilaterally symmetric human organism result in differential unequal loads on various muscles, joints, and connective tissue. One task may stress one tissue element to 80% of its capacity, whereas another one is stressed only 10%. Additionally, this distribution is not determined by the tolerance of the tissue concerned. Such diverse distribution of stress results in one muscle becoming more fatigued than others.15,16 This differential fatigue causes loss of coordination resulting in sudden and significant stress concentration that precipitates an injury. 3. The Overexertion Theory16: The basic tenet of this theory is that even a rested and normal tissue can, and probably will, fail when the stress/load exceeds its tolerance time. Although stressed and fatigued tissues cannot withstand stress concentration, it is not necessary for tissues to reach that stage to fail.
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4. The Multivariate Interaction Theory16: Over and above the three previous theories, the variability in the individual threshold indicates also that a precipitation of musculoskeletal injury may be modulated by the interaction of genetic, morphologic, psychosocial, and biomechanical factors. Within each of these categories are many variables that may potentiate an injury. Interaction between the relative weights of the variables and the extent to which these have been stressed in any given individual determines the final outcome. Although these four theories have been presented as distinct, all four are simultaneously operative but to a different degree depending on the circumstances and individuals. As pointed out above, humans have not evolved over the past 250 million years to be industrial workers. Humans will therefore always find themselves in the middle of a conflict between their nature and an industrial requirement. Such a backdrop clearly makes occupational injury prevention not only a daunting and lofty goal but an unachievable objective. Control of injuries to reduce their incidence and severity, however, remains a goal that may be achieved to varying degrees. With this in mind, Kumar12 presented a strategy to quantify the risk based on the discrete physical elements of the task in question.
THE EXTENT OF THE PROBLEM As a medical condition LBP has only one redeeming feature—it is not fatal. In spite of the obscurities associated with its etiology, classification, and treatment, human and economic impacts have been approximately quantifiable. Chapter 4a on the epidemiology of LBP offers a comprehensive picture of the problem; suffice it to say here that it is a large social and economic one. Although it occurs in less developed countries also, the impact of LBP is much more recognized in Western and industrialized countries. To put the extent of the problem in perspective, a brief description follows. Andersson1 stated that national statistics from the European countries reveal 10% to 15% of all sickness absence to be due to back pain, with the number of work days lost per worker increasing steadily. An annual prevalence of 25% to 45% was reported, and chronic back pain was present in 3% to 7% of the adult population. The lifetime prevalence of LBP has been variously reported as between 70% and 80%. In Canada, LBP has steadily constituted approximately 27% of all industrial injuries; these have been reported to cost disproportionately higher amounts than all other injuries. In the United States, the annual prevalence has been reported to be in the 15% to 20% range. Khalil8 reported that on any given day, roughly 75 million Americans have back pain, 6.5 million of whom are in bed. Webster and Snook23 reported the cost of LBP in 1989 incurred by Liberty Mutual, the largest insurer in the United States; it constituted 16% of the claims and accounted for 33% of the total expense. They reported also that the mean cost per case of LBP was $8300 compared with $4100 for all other claims combined, whereas the median cost was $396 ($168 for other claims). In these claim settlements, 34% of the total cost for LBP was medical, whereas 66% was indemnity cost for lost time and wages.23 No matter which way one looks, LBP is prevalent and expensive. Some of the socioeconomic aspects of our society may accentuate
the problem because of the alleged secondary gain. We have been able to reduce neither the incidence nor the severity of LBP; a cure neither exists nor is likely to emerge in the foreseeable future. No difference in long-term outcome between aggressive and conservative treatments has been identified, and we seem unable to control the problem in a significant or meaningful way. LBP is clearly here to stay. It is therefore of utmost importance to focus on workplace adaptations to reduce human suffering and economic cost. Our endeavor to identify these adaptations must try to reduce the magnitude of identified risk factors and the exposure of workers to them, decrease the incidence of LBP in healthy people, and reduce stress in patients who already have the condition. Such adaptations will be helpful in returning workers to work after injury.
DISABILITY CAUSED BY LBP LBP is associated with considerable disability that results in work loss, its most important social and economic consequence despite the influence by many other factors. A direct correlative scale between LBP, disability, and work loss has not been established. A simple clinical and subjective assessment of disability, however, has been claimed to have considerable relevance to quality of life as well as industrial performance. This assessment is focused on loss of function rather than pain. The emphasis is on whether an activity can be performed by an individual or is restricted because of LBP. Implicit in this assumption is that the restriction must have its onset coincident with that of the back pain and must therefore be the functional limitation. The specific criteria used by Waddell et al21 are as follows: 1. Bending and lifting 2. Sitting 3. Standing 4. Walking 5. Traveling 6. Social life 7. Sleep 8. Sex life 9. Dressing/undressing The aforementioned criteria combine postural, strength, metabolic, and everyday living activities that are involved also in occupational activities. LBP and loss of function through disability are results of biomechanical (kinematic and kinetic) perturbation of the human system. These demands are covered in Chapter 4b, but we note here that the functional activities accentuating these demands are divided into two main categories: static load (sitting, holding) and dynamic load (pushing/pulling, carrying, and lifting/ lowering). The concentration must therefore be on those activities that reduce hazards for initial injury and subsequent recurrences.
ADAPTATIONS Static work Spitzer et al20 report the LBP incidence in Quebec, Canada of individuals required to do heavy work but also include sedentary
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work areas such as “government, wholesale and retail, and finance and insurance.” Magora17 reported on LBP for bank tellers and for those who perform heavy work.
Seated work Problem Because intervertebral disks are avascular, their nutrition depends entirely on diffusion. Intervertebral disks also are viscoelastic. While an individual is sitting, the load on the intervertebral disk is 140% of that imposed by standing. This static load progressively decreases the water content of a disk; an increased load accelerates this process. Loss of water from a disk makes the diffusion process more difficult and results in reduced oxygen tension and lack of nourishment, leading to disk degeneration. Sedentary occupations involve prolonged exposure to static loads, hastening this process and making the disk more vulnerable to injuries. A constant static load also deforms the viscoelastic disk and causes compression creep. Because creep is time dependent, elimination of a load does not immediately restore either the preload disk configuration or the water content. The reduction in water and oxygen is therefore prolonged, interfering with disk metabolism by decreasing the amount of glycosaminoglycans (which have a strong affinity for water) and increasing the content of keratan sulfate (which is amorphous with far less capacity to imbibe water). In the short term, the viscoelastic deformation may lead also to laxity of the ligament and lack of coordination, potentiating injury through biomechanical perturbations. Over the long term, it leads to degenerative and permanent changes that are a hazard to the back. The problem of seated sedentary work worsens considerably when prolonged sitting is combined with whole-body vibration, such as with truck driving. The frequencies of many vehicles are close to the natural frequency (4 to 8 Hz) of the human spine, causing resonance and thus amplification of the motion amplitude. Truck drivers must contend not only with this vibration but also with the static loading of the disk while driving. In addition, often they have periodic acute loading of the back when they load or unload their vehicles.
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stools; both conventional and sit/stand chairs should have backrests. Sit/stand chairs should have a forward tilt of 15-30 degrees and a fabric seat.4 Another technique to encourage movement is job rotation. A chair is the key component of seated work, but because not all seated work is the same, chairs should be matched to specific jobs. Of course, people vary in height and weight, and many of them often sit in the same chair because of multiple shifts, parttime workers sharing a shift, and holiday or vacation replacements. Thus chairs should be easily adjustable in terms of seat pan height, back rest height and forward/back location, and armrest width and height. The seat should be padded with a breathable fabric; avoid plastic and leather. It should not be contoured, because this reduces micropostural changes. A curved front edge (waterfall front) maximizes contact with the underside of the thigh; avoid upholstered beading on the front edge. Normally, the seat should tilt backward 1-5 degrees and permit swiveling. For seat width, the wider the better; for depth, the most common problem is a seat that is too deep. A deep seat forces the sitter forward (losing support of the backrest) or back (with the legs dangling). The ideal backrest is adjustable both horizontally and vertically and has a spring action so that it “tracks” the angle of the back as the person moves. It should be concave to give area support to the back, especially in the lumbar region. Armrests should be adjustable in width and height. Avoid long armrests that hit the table edge and preclude good chair location with respect to the task. The legs/pedestal normally should permit swiveling and thus micropostural changes. The sitter’s legs should be able to tuck under the seat to shorten the hamstrings (reducing their pull) and decrease stress on the back. If the seated worker moves about the work station, the chair should have casters; otherwise, they are inadvisable because they force the operator to use leg muscles to keep the chair still. Design modifications to truck seats should reduce vibration at the point of origin or dampen it before transmission to the driver. Trucks should be equipped with hoists and dollies to reduce acute stress on the back by doing the work.
Holding work Problem
Control strategies The two strategies for addressing this problem are personal compensations and job design. From a personal viewpoint, people in sedentary jobs should lead active lives outside the workplace. In addition, at work they should be encouraged to change postures frequently, move around, and mix nonseated with seated work. (Naturally, the job design should not just permit this movement but also encourage it.) Job designs of seated workers often include either machines or other workers to bring supplies and remove finished products. By not allowing the worker to move, this practice creates a “straight jacket” that precludes movement. Permitting a worker to fetch supplies and dispose of products not only is beneficial but also should be encouraged within limits. Another possibility for permitting some movement is to have a sit/stand work station where the worker can alternate between sitting and standing. Standing work is better if there is a “bar rail” or footrest upon which the worker can alternate foot positions.9 Avoid using
For some tasks in auto assembly, painting, or kitchen and laundry work, for example, workers hold an object without movement. Even without an object, the weight of one hand and arm is approximately 4.9% of body weight. The farther from the spine the hand or object, the greater the problem, because torque is a product of weight times moment arm.
Control strategies To address this problem, reduce the torque and its duration. Figure 4e.1 shows how a tipping aid can reduce the strain of holding a drum or container. An angled bar (a “plow”) on a belt conveyor can direct a product on the conveyor toward the side closest to the worker, who need not reach as far for the item and therefore reduces torque on the spine. For standing workers, a conveyor should be about 50 mm below the elbow (by height adjustment or by having short operators stand on platforms) to minimize torque on the arms and back. A balancer (Fig. 4e.2) reduces tool weight.
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Dynamic work Manual handling is quite prevalent in industry. Asfahl2 estimated that for every pound of product, 80-150 pounds of materials are handled and moved. Konz and Johnson9 stated that 25% of all industrial injuries are associated with manual handling—670,000 injuries per year in the United States. Of money spent on industrial injuries, 60% pays for those caused by manual handling, which accounts for 93,000,000 work days lost each year. Dynamic work risks are divided among pushing/pulling, carrying, and lifting/ lowering, the last of which causes most problems.
Pushing and pulling Imrhan7 provided an excellent summary of pushing/pulling. Pushing occurs not only while standing but also while sitting and even kneeling. Height and direction also are important (Fig. 4e.3).
Control strategies Figure 4e.1 Tipping aids permit a drum or carboy to be counterbalanced when pouring. The danger of spills and operator muscle stress is reduced.
A poor interface of the hand and handle is a potential weak link. Although a handle is needed for pulling, pushing may just use a flat surface. Two hands are better than one. The arm and shoulders (rather than the back) tend to be limiting (causing local muscle fatigue) when the activity is repetitive. Workers should avoid pushing or pulling above the shoulders or below the hip. Effective pushing involves leaning toward the load with the rear foot positioned behind the body’s center of mass (Fig. 4e.4), whereas pulling involves leaning away from the load with the rear foot behind the body’s center of mass. Although there should be a high coefficient of friction between the floor and the shoe, the object may have a low coefficient of friction against its supporting surface. Ball transfer sections on conveyors have a kinetic friction of 0.03 to 0.15, for example, so pushing a 50-kg container on balls requires a force of 1.5 to 7.5 kg. Air-film pallets use the same concept of reducing the friction of object against surface. Generally, people push/pull perpendicular to the shoulders. When pushing parallel to the shoulders, the capability is 50-60% of the perpendicular capability. Several recommendations for force limits for pushing and pulling have been published.18,19 In summary, ● Two hands are usually better than one. ● Force capability decreases when it is used more often. ● Initial force capability is higher than sustained capability. ● Pushing capability is higher than pulling capability. ● Pushing should be done at waist level and pulling at thigh level.
Carrying
Figure 4e.2 Balancers reduce tool weight from pounds to ounces. Note that the balancer is suspended from a job crane to minimize horizontal force as the tool is moved about the workplace. The greater tool weight increased torque at the elbow and shoulder, thereby decreasing comfort of the neck and back as well as the arm (Ulin S, Armstrong TJ, Snook SH, Monroe-Keyserling W: Examination of the effect of tool mass and work postures on perceived exertion for a screw driving task. Int J Ind Ergonom 12:105-115, 1993).
Although carrying objects for long distances (those over 10 m) no longer is common in developed countries, workers still carry around work stations. Carrying objects up and down stairs is especially dangerous because the hands are holding the object and thus not free to grasp handrails if there is a slip and because the object may obstruct vision.
Control strategies Long-distance carrying is best when mechanized with lift trucks, conveyors, or carts (Fig. 4e.5). As anyone who has transported a
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Figure 4e.3 Chiming a drum (rotating a tipped drum) requires little effort; with skill, the drum’s momentum can be used to move it onto a pallet. A drum cart is another alternative. A straight push, however, as shown on the right, requires considerable effort.
suitcase through an airport knows, pushing or pulling is better than carrying, so wheels should be used whenever possible. Jib cranes, ball-transfer sections, or manipulators (Fig. 4e.6) can move objects within work stations, as do ramps and elevators between floors.
multiplier, and CM is the coupling multiplier. Konz and Johnson9 explain the calculation procedure in detail, and the disk accompanying the book has a computer program to solve the equation.
Control strategies Lifting and lowering As pointed out above, manual handling creates many problems. Engineers and ergonomists can focus on the job-specific factors with reference to the detailed tables of the manual handling guide.18 For example, Table 4.2 of the guide gives 720 recommended weights for male industrial workers for two-handed symmetric lifting for 8 hours. The table has three box sizes, eight lifting frequencies, six lifting distances, and five population percentiles. The most common approach is that set forth in the National Institute for Occupational Safety and Health (NIOSH) lifting guideline.22 The NIOSH guideline assumes a load of 23 kg but then reduces the 23 through 6 multipliers (all less than 1.0) to arrive at a recommended weight limit (RWL): RWL = LC × HM × VM × DM × FM × AM × CM where LC is the load constant (i.e., 23 kg), HM is the horizontal multiplier, VM is the vertical multiplier, DM is the distance multiplier, FM is the frequency multiplier, AM is the asymmetry
1. Select strong people based on tests: Several studies have shown the significance of the job severity index, the ratio of the task demand to the person’s capability. One approach may therefore be to select workers with large capacities. It is important to consider worker capacity in job-simulated tests, which force the analyst to measure not only this factor but also the task requirements. 2. Bend the knees: Despite a concerted effort to train workers to lift with bent knees and straight backs, the practice has not received universal acceptance. The logic behind the recommendation has been to reduce the moment arm on the lumbosacral disk, thereby reducing mechanical compression. It has been shown, however, that unless the object to be lifted is brought very close to the body, the squat lift can in fact significantly increase mechanical compression on the lumbosacral disk. It has been shown also that the squat lift is associated with significantly higher physiological cost and is more tiring for workers.
Typical posture Recommended posture Figure 4e.4 Posture when pushing makes a difference. Peak intraabdominal pressure was 50% less when pushing with the back (Ridd J: A practical methodology for the investigation of materials handling problems. In T Kvalseth, ed: Ergonomics of work station design. London, 1983, Butterworth-Heinemann).
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A
C B Figure 4e.5 Drum carts reduce stress. (A) A two-wheeled cart; it should have a latch over the top rim during movement. (B) The foot can be used to help tip the drum. Another handle forward of the main handles is useful when tilting and maneuvering the drum to scales and pallets. (C) A four-wheeled cart useful for heavier drums; note that the hand positions are different.
Another disadvantage of the squat lift is that it causes considerable stress on the knees, which are also a frequent site of mechanical disorders. Therefore a universal acceptance of the squat (as opposed to the stoop) lift is neither physiologically nor mechanically sound. It is perhaps for this reason that this method has not been accepted by workers as widely as was initially hoped. Furthermore, the statistics of low back injuries associated with lifting over the past 40 years make clear that a steady increase in incidence has occurred despite many industrial workers’ following the squat method. It is important to assess the job as well as the individual performing it before recommending squat or stoop lifting. Garg et al6 compared the physiologic costs of different methods of lifting. They found that when subjects were allowed to lift any way they wanted, they chose neither pure stoop nor pure squat but combined the features of both in a freestyle lift. This lift was found to be metabolically the least expensive. The recommendation is therefore to use an individualand task-specific method to minimize stress on spine and reduce the chances of injuries.
3. Don’t slip or jerk: Sudden and ballistic movements have a large inertial component. Because of the viscoelastic nature of the human back and the resistance to immediate deformation offered by the fluid portion of the tissue, such inertial forces can exceed the tolerance limits of the tissues.16 In addition, sudden motion may also cause a slip or fall while performing a lift. It is therefore recommended that workers wear shoes with soles having a large contact area and a high coefficient of friction, as should floors, which must not be smooth. Data on a force platform indicate that peak forces and torques during lift are very “spiked,” with the peak force often occurring during initial lowering of the body before the object is even grasped. The accelerations and decelerations during lifting and lowering should be fast enough that the body gets the benefit of the momentum without causing a jerk that may lead to an injury. 4. Avoid twisting: To maintain symmetry of the human body, the spine is provided with a bilaterally symmetric arrangement of muscles and ligaments. Any rotation accentuates the activities in the agonist group of muscles and reduces the
Chapter 4e
5.
6.
7.
8.
Figure 4e.6 Manipulators (balancers with arms) can support tools or can be used to move products around work stations.
contribution of the antagonistic muscles. When manual materials are handled, a twisted posture or when the spine is progressively twisted during a lift, the force production in different muscles is continually varied, accentuating the stress on one group of muscles and ligaments. When most of the load is borne by only 50% of the structures, the stress could easily be doubled, significantly increasing the chances
●
Adaptations
of injury. Twisting while bent over, such as when removing parts from the floor, is risky. A general recommendation is therefore for workers to move their feet instead of twisting their backs. Because workers might not comply as rigorously as desirable, an engineering approach precluding the need to twist is recommended. Such an approach will solve the problem rather than depend on the workers’ knowledge, awareness, alertness, and cooperation. Figure 4e.7 shows how a task can be modified to reduce bending and twisting. Use mechanical aids: The most desirable means of preventing injuries associated with manual materials handling is to eliminate it by using mechanical aids. Instead of moving a power tool around a work station, for example, a balancer (Fig. 4e.2) or manipulator (Fig. 4e.6) can be used. Figure 4e.8 shows a turntable on a scissors lift used to mechanize palletizing; in automation, the operator would be replaced with a palletizer. In some circumstances robots are appropriate. Other machines commonly used to eliminate manual handling are hoists, lift trucks, conveyors (both portable and telescopic), and lever arms. Consider the packaging: For job design, an important concept is to keep the load close to the body, so it is important to keep packages small. Big, bulky, and awkward packaging increases the moment arm of the load on the spine, thereby increasing the compressive load significantly. Bulk may make it more difficult to lift 25 kg of feathers, for example, than 25 kg of iron. Konz and Coetzee11 reported that increasing a box’s volume up to a 30-cm cube did not bother men but strongly bothered women. When determining packaging dimensions, it is therefore important to consider the anthropometry of the work population. Have good coupling: Cardboard boxes with cutout holes provide poor coupling because (1) the hand cannot rotate as the object is lifted from the knee to the waist and (2) the narrow cardboard surface area tends to concentrate the load on a small area of contact with the hands, thereby cutting the circulation and squeezing the muscles. When the packages to be lifted are larger than optimal size, it is particularly important to provide a comfortable handhold to permit a relatively riskfree, orderly, and smooth lifting activity that minimizes the chance of injury. Consider work height and reach: Konz stated, “Drag it, pull it, push it, but don’t lift it.”10 As explained above, if lifting is necessary, it is best done at knuckle height; loads should not be on the floor or above the shoulders. When cartons are loaded from a conveyor, for example, the conveyor height should be adjustable. When they are loaded from a pallet, it should be left on the lift truck forks, the height of which should be periodically adjusted. If the fork lift cannot be tied up, the pallet should be placed on a wheeled lift table.
A summary of all these principles has been provided by Ayoub et al3 in a comprehensive set of guidelines to control and reduce occupational health problems associated with manual materials handling. Their recommendations can be summed up in two statements: (1) eliminate heavy manual materials handling and (2) decrease the stress to the worker. They recommend the use of mechanical aids such as hoists, lift tables, and conveyors and the provision of best work heights that can be varied to suit the operator and achieve an optimum work arrangement.
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Workplace adaptation for the low back region
Figure 4e.7 Work station positioners reduce lifting, bending, and twisting. (A) A scissors lift. (B) A bin on an adjustable-height cart that is useful to create temporary work stations for tasks such as shelf stocking. (C) A self-leveling truck (similar to cafeteria tray dispensers).
Figure 4e.8 Turntables can reduce stress when loading or unloading. The turntable is rotated after a few items are moved. It can be mounted on the floor and a pallet placed upon it. If the turntable surface is rollers, ball casters, or an air table, rotation can be manual. If it is mounted on a scissors table (as shown), horizontal transfer can replace lifting and lowering.
Chapter 4e
A reduction of stress, they suggest, can be achieved by reducing the weight of the object in cases in which it is not possible to split the load between two workers. A reduction in the size and weight of containers is a desirable goal also. The authors recommend changing the type of manual materials handling: lower the load rather than lift, push the load rather than pull, and pull the load rather than carry. They suggest reducing both the horizontal and vertical distance in reaching for an object and transporting it. Avoiding twisting in both standing and seated work is desirable. Modification of an object to make it easier to handle by using handles, balance containers, and reasonable width are all good design criteria. On the worker side, however, it is important also to provide adequate recovery time by reducing the frequency with which a particular task is performed and allowing for job rotation.
7. 8. 9. 10. 11.
12. 13. 14. 15. 16. 17. 18.
REFERENCES 1.
2. 3. 4. 5. 6.
Andersson GBJ: The epidemiology of spinal disorders. In J Frymoyer, Spitzer W, LeBlanc FE, Dupuis, M eds: The adult spine. New York, 1991, Raven Press, pp. 107-146. Asfahl CR: Industrial safety and health management. Englewood Cliffs, NJ, 1984, Prentice Hall. Ayoub MM, Selan J, Jiang B: Manual material handling. In G Salvendy, ed: Handbook of human factors. New York, 1987, Wiley & Sons. Chester M, Rys M, Konz S: Leg swelling, comfort and fatigue when sitting, standing, and sit/standing. Int J Indust Ergon 29:289-296, 2002. Davis PR: The biological basis of physiological ergonomics requirements. Int J Indust Ergon 23:241-245, 1999. Garg A, Sharma D, Chaffin DB, Schmidler JM, et al: Biomechanical stresses as related to motion trajectory of lifting. Hum Factors 25(5):527-539, 1983.
19.
20.
21.
22.
23.
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References
Imrhan S. Push-pull force limits. In W Karwowski, W Marras, eds: The occupational ergonomics handbook. Boca Raton, 1999, CRC Press. Khalil T: Ergonomic issues in LBP: origin and magnitude of the problem. Proceedings of the Human Factors Society, San Francisco, 1991, pp. 820-824. Konz S, Johnson S: Work design: occupational ergonomics, ed 6. Scottsdale, AZ, 2004, Holcomb Hathaway. Konz SA: Work design: industrial ergonomics, ed 4. Scottsdale, AZ, 1995, Publishing Horizons. Konz SA, Coetzee K: Prediction of lifting difficulty from individual and task variables. Proceedings of the Fourth International Congress on Production Research, Tokyo, 1977. Kumar S: A conceptual model of overexertion, safety and hazard. Hum Factors 36:197-209, 1994. Kumar S: Cumulative load as a risk factor for back pain. Spine 15(12):1311-1316, 1990. Kumar S: Functional evaluation of the human back: a research report. 1991. Kumar S, Narayan Y: Spectral parameters of trunk muscles during isometrics axial rotation in neutral posture. J Electromyogr Kinesiol 8:257-267, 1998. Kumar S, Narayan Y, Stein RB, Snijders C: Muscle fatigue in axial rotation of the trunk. Int J Indust Ergon 28:113-125, 2001. Magora A: Investigation of the relation between LBP and occupation. Ind Med 39(12):504-510, 1970. Mital A, Nicholson A, Ayoub MM: A guide to manual material handling. London, 1993, Taylor & Francis Publishers. Snook SH, Ciriello VM: The design of manual handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics 34(9):1197-1213, 1991. Spitzer W, LeBlanc FE, Dupuis, M: Scientific approach to the assessment and management of activity-related spinal disorders. A monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 12(Suppl):1-559, 1987. Waddell G, Allan DB, Newton M: Clinical evaluation of disability in back pain. In JW Frymoyer, Spitzer W, LeBlanc FE, Dupuis, M eds: The adult spine. New York, 1991, Raven Press. Waters T, Putz-Anderson V, Garg A: Application manual for the revised NIOSH lifting equation. NIOSH Pub PB94, Rockville, MD, 1994, Department of Health and Human Services. Webster BS, Snook SH: The cost of 1989 workers’ compensation LBP claims. Spine 19(10):1111-1115, 1994.
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Appendix 4e.1 Websites of workstation suppliers
Advance Lifts (work station positioners) www.advancelifts.com American Lifts (scissors lifts) www.americanlifts.com Autoquip (lifting, turning, tilting equipment) www.autoquip.com Bishamon Industries (pallet positioners, lift tables) www.bishamon. com Columbus McKinnon (lift tables) www.cmworks.com Columbus McKinnon (manipulators) www.positech-solutions.com Econolift (lifts/tilters) www.econolift.com Ergonomic Systems (work station/positioners) www. ergonomisystems.com
Glasgow (air tables) www.glasgowproducts.com Knight Industries (balancers, manipulators) www.knight-ind.com Presto Lifts (work station material handling) www.prestolifts.com Rampmaster (work station material handling) www.rampsonline. com Scaglia America (balancers, manipulators) www.scaglia.it Southworth (work positioning) www.southworthproducts.com Tawi USA (vacuum lifting) www.tawi.se Vestil (work positioning) www.vestilmfg.com
CHAPTER
Shoulder and Elbow
5
CHAPTER
5a
Shoulder and Elbow Disorders Marianne Magnusson and Malcolm Pope
This chapter discusses the epidemiology and pathomechanisms of disorders of the shoulder and elbow. Shoulder and elbow disorders were reported as related to certain occupations as long ago as 1713.80 Like other musculoskeletal disorders (MSDs), those of the upper extremity are increasing, as expressed by a more frequent reporting of them as occupational diseases.65 The reason for the increase might be the higher degree of automation resulting from workplace designs improved to reduce heavy workloads like lifting and manual labor. The demands of increasing productivity, however, which in turn imply the simplification of working tasks, has increased the work pace.96
CLASSIFICATION OF DISORDERS Shoulder In the International Classification of Diseases,99 work-related neck-shoulder disorders have been classified into “occupational diseases,” in which there is a direct cause-effect relationship between hazard and disease, and “work-related disease,” in which work environment and the performance of work contribute significantly, but as one of a number of factors, to the causation of a multifactorial disease.98 The concept of occupational cervicobrachial disorder was adopted in 1973.6,61 It is defined as “functional and/or organic disturbances resulting from neuromuscular fatigue to doing jobs in a fixed position or with repetitive movement of the upper extremities.” Waris93 named four categories: the cervical syndrome, the tension neck syndrome, humeral tendinitis, and thoracic outlet syndrome. Introduced in Australia, the term repetition strain injury is defined as “a soft tissue disorder caused by muscle overloading from repetitive use or maintenance of constrained postures” that “occurs among workers performing tasks involving frequent repetitive movements of the limbs or the maintenance of fixed postures for prolonged periods.”12 Cumulative trauma disorder, musculoskeletal injury and disorder, occupational repetitive strain injury, and regional pain syndrome are other terms that describe essentially the same condition.
Elbow Tennis elbow, also called lateral humeral epicondylalgia or lateral elbow syndrome, is a painful condition of the lateral aspect
of the elbow. Cubital tunnel external compression syndrome is caused by compression of the ulnar nerve at certain elbow flexion angles at a subcutaneous location behind the humeral epicondyle (cubital tunnel).
EPIDEMIOLOGY General population In general studies that include large sample populations without special demands for neck and shoulder activity, the 12-month prevalence of neck and shoulder disorders was 15% to 18%.5,94 Disorders of the neck and shoulders are most common among women.7,21,93,94 In a Swedish study, 50% of the women but only 36% of the men reported strain injuries from the neck and shoulders.44 Another study reported a 10 times higher rate of sick leave due to occupational cervicobrachial disorders in women compared with the sick leave in men due to occupational low back pain.51 Perhaps even more than men, women often work in occupations with repetitive and monotonous work tasks, and many studies have reported an increased prevalence of upper limb disorders in repetitive work.32,47,58,78,92 In a large Swedish study of 2537 men and women, 20% of the women and 16% of the men had neck-shoulder problems during the last 12 months,92 the incidence of which increased with age and occupational physical load. Takala et al reported a 1-year prevalence of 18% of women and 16% of men in a Finnish rural population.89 In a random sample of 855 men and women in Iceland, 65% of the women and 43% of the men had neck or shoulder pain during the previous year.79 Neck and shoulder pain has been found to be not only interrelated but also related to low back pain, indicating a susceptibility and a predisposition to develop MSDs.63
Occupational risk groups Epidemiologic studies show, and most researchers agree, that along with personal factors such as age, genetics, and gender, exposure to a combination of physical and psychosocial workplace risk factors is a major contributor to these disorders. Specific physical factors include intense, repeated, or sustained exertions; awkward, sustained, or extreme body postures; insufficient recovery time; vibration; and cold temperatures. Specific examples of workplace psychosocial factors include monotonous work, time pressure, high workload, lack of peer support, and a poor supervisor-employee relationship.34 Musculoskeletal diseases were the major reason for long-term absenteeism in a manufacturing company. Low back pain accounted for 17.7% of all long-term absenteeism (the greatest amount), and neck and shoulder pain caused 15.9%. Back disorders were most common in heavy manufacturing workshops, whereas in the light manufacturing workshops the most dominant diseases related to the neck and shoulder.51 As recorded in a questionnaire and compared with a control group with more varied tasks, females employed in assembly, fish-processing, and ceramics factories, all representing highly repetitive work tasks, had considerably higher prevalences of
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Shoulder and elbow disorders
Table 5a.1 Elbow problems in newspaper workers (% of total)82
12-month prevalence (%) Missed work (%) n
All
Office
Production
8 1 906
6 1 682
12 2 201
complaints and physical examination diagnoses of neck and upper limb disorders.70 Without a specific diagnosis or defined symptoms, neck and shoulder problems have been reported in a large number of studies involving secretaries and office workers,10,41,42,56,91 dentists,55,68 sewing machine operators,86 visual artists and piano players,16,27 and railway station workers.13 The annual prevalences of neck and/or shoulder symptoms for female secretaries and office workers ranged from 45% to 63%, whereas those for male office workers were considerably lower, ranging from 16% to 27%. Table 5a.1 reports the elbow problems found in a study surveying workers in the newspaper industry.82 Musculoskeletal problems in instrumental musicians have a long history.25,26 Lederman and Calabrese52 described an increasing number of reports of musculotendinous overuse. Nerve entrapment syndromes have been reported in musicians by Knishkowsky and Lederman.48 Charness et al17 reported that routine electromyography (EMG) and nerve conduction studies were abnormal in less than half the musician patients studied, attesting to the potential for even mild ulnar neuropathy to produce disabling symptoms.
RISK FACTORS Work-related factors Work-related factors recognized for their association with upper limb disorders include repetitive or forceful exertions, awkward postures, and segmental vibration. Several studies have suggested a relationship between static and/or repetitive load and disorders in the neck and upper extremity.30,44,51,60,95 In their meta-analysis of occupational neck-shoulder disorders, Hagberg and Wegman32 found that jobs with highly repetitive shoulder muscle contractions, static muscle work, and work above shoulder level were associated with the tension neck syndrome. Kuorinka and Forcier49 looked specifically at shoulder tendinitis and stated that the epidemiologic literature is “most convincing” regarding work relatedness, showing an increased risk especially from overhead and repetitive work. Several studies have supported these associations4,16,27,72,86; the mechanical load on the shoulders was obvious, and working tasks involving continuous arm movements always generate a static load component.1,72,85,97 Repetitive work should therefore not be considered independent of posture. Association between repetition and shoulder tendinitis has been reported in three studies,23,71,73 in all of which some or all of the results showed
associations with a combined exposure to repetition and awkward posture. The principal muscle to carry this load is the trapezius. The relative load as a percentage of maximum voluntary contraction (MVC) on the upper trapezius has been shown to increase linearly with the relative torque in the glenohumeral joint.29 There are large differences, however, among muscles and between flexion and abduction. A given shoulder torque during flexion produces smaller amplitudes of both the intramuscular pressure and the EMG than for the same torque during abduction.38 With a shoulder abduction of 30 degrees, the intramuscular pressure in the supraspinatus muscle by far exceeds the level at which the blood flow is significantly impeded. The supraspinatus is thus extremely vulnerable in work situations requiring arm elevation. High shoulder muscle force requirements can cause increased muscle contraction, which may lead to an increase in both muscle fatigue and tendon tension and may possibly impair microcirculation as well. Sjøgaard et al86 found that muscular fatigue would occur at EMG levels as low as 5% of MVC if sustained for 1 hour. Other studies have demonstrated that when the period of muscle contraction is extended to more than an hour, the endurance limit of force may be as low as 8% MVC.40 Workers performing repetitive work with the hands and wrists while maintaining static upper arm elevation may experience fatigue even at low load levels. Jonsson et al40 reported that many constrained work situations are characterized by static load levels near or exceeding 5% MVC even when there is a fairly low mean muscular load. Ohlsson et al71 reported an odds ratio of 3.03 (95% confidence interval, 2.5-7.2) for supraspinatus, infraspinatus, or bicipital tendinitis for work in the fish industry, representing repetitive work and poor posture. Compared with that of a referent population, the odds ratio for assembly work, which requires repetitive arm movements with static shoulder load, was 4.2 (95% confidence interval, 1.35-13.2). Kurppa et al,50 Silverstein et al,85 and others reported that highly repetitive tasks can cause pain and disability in the upper extremity. In many jobs, upper extremity tasks require repetitive contractions of those muscles over long periods of time at low contraction intensities and short contraction-relaxation cycles. Silverstein et al85 created a prevention index to rank industries by averaging the ranks of their number of claims and their claims incidence rate with a focus on nontraumatic soft tissue MSDs. Although the incidence rates for some disorders are decreasing, the overall rate is not decreasing as fast as that for all other claims. In some cases, the rate is stable (sciatica, rotator cuff syndrome) or increasing (epicondylitis). The industries with the highest risk are characterized by heavy manual handling and repetitive work. Edwards22 proposed that fatigue and lack of recovery are the elements that can cause injury to the elbow. In simulations of upper extremity work measuring recovery of blood flow, EMG fatigue index, and subjective ratings, Byström and Kilbom15 concluded that a mean contraction intensity of higher than 17-21% MVC was not acceptable. Using the same techniques, Byström and FransonHall14 suggested in a later article that continuous handgrip contractions higher than 10% MVC are to be avoided. These recommendations are conservative, and many industrial jobs exceed the safety limits.
Chapter 5a
Overall, epidemiologic evidence suggests a relationship between repeated or sustained shoulder postures with more than 60 degrees of flexion or abduction and shoulder MSDs, including both tendinitis and nonspecific pain. The evidence for increased risk of MSDs due to specific postures is strongest with a combination of exposures to several physical factors such as force and repetitive work. An example would be holding a tool while working overhead. Insufficient evidence exists to make an association between shoulder tendinitis and exposure to segmental vibration. Stenlund et al88 found such an association, but work with vibration exposure also placed a large static load on shoulder muscles so that the effects of forceful exertions could not be separated from it. Because they are multifactorial in origin, shoulder MSDs are and may be associated with both occupational and nonoccupational factors whose relative contributions may be specific to particular disorders. The confounders for nonspecific shoulder pain, for example, may differ from those for shoulder tendinitis. (Two of the most important confounders or effect modifiers for shoulder tendinitis are sport activities and age.) Excessive contractions or fatigue can lead to tennis elbow, one of the most common occupational elbow problems.19 This is characterized by intense pain of the lateral aspect of the elbow exacerbated by grip and more use. Coonrad18 reported that the main problem is repetition, but it is multifactorial in origin. Allander3 reported a prevalence of one third in 15,000 subjects. In studies at certain occupational clinics, Dimberg20 found that 64% of all diagnosed cases were related to work. Cyriax19 reported that only 8% of cases actually involved tennis. In a review, however, Maylack67 reported that 50% of competitive tennis players suffer from at least one episode of lateral epicondylitis. Another elbow problem is cubital tunnel external compression syndrome. As the ulnar nerve travels from the brachial plexus to the hand, it is vulnerable to compression at certain elbow flexion angles at a subcutaneous location behind the humeral epicondyle (cubital tunnel). A common occupational risk reported in drivers occurs where the elbow is rested on a hard surface for a long period of time.2 Mansukhani and D’Souza66 reported unilateral ulnar neuropathy in diamond workers that was restricted to the arm holding the eyeglass for inspecting the diamonds.
Individual factors Not all workers performing similar and risky work tasks develop MSDs, due to the obvious influence of individual factors on the exposure-effect relationship. The individual factors most frequently studied or controlled for are sex and age. Some studies have shown that age affects the prevalence of MSDs,36,47,54,91,94 whereas others have shown no such influence.11 Muscle strength and endurance influence the risk of neck and upper limb disorders. With higher muscle strength, the muscle is obviously less loaded than in the case of lower strength for the same force exertion. Women in general have lower strength than men, in particular in the upper extremities, and older people are weaker than younger ones.69 Some studies, however, have shown that compared with men, women have longer muscle endurance
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Pathomechanisms
in proportion to their muscle strength,10,84 but this has not been proven for all muscle groups. Although women may have more neck-shoulder disorders than men because of fatigue and poor strength, it is more likely because women predominate in jobs involving a high degree of repetitiveness and prolonged static postures of the neck and shoulders. Poor muscle strength and low endurance have been shown in patients with neck-shoulder pain. Strength was affected in acute patients,9,51 whereas endurance was impaired in chronic patients as well.31,86,87 Other studies, however, failed to show a relationship between neck and shoulder symptoms and strength and endurance.46 Indeed, the contrary was shown in a prospective study; subjects with high muscle strength in shoulder elevation seemed to be at a higher risk.40,45 A longitudinal study of motor assembly workers showed that low isometric strength of shoulder muscles was a risk factor for neck and shoulder pain.43 Hägg et al33 could not show significant relations between either EMG signs of fatigue during work or isometric strength with the development of muscular disorders during a 2-year follow-up. A few studies found certain personality traits to predispose to MSDs. Characterized by competitiveness, impatience, and a feeling of time urgency, the “type A” personality has been found to be associated with low back pain36,37,94 and with neck-shoulder pain.24,33,83
Social factors Along with recognition of the importance of the physical load to MSDs, there is a growing awareness of their association with psychosocial factors and work environment.59,64 In a longitudinal study, job satisfaction and relations with coworkers and supervisors were the strongest predictors for developing industrial back pain.7,8 Monotony, stress, low job satisfaction, lack of control, and low skill requirements characterized a typical light assembly job where young males reported a high rate of back pain.57,62 In a study of occupational drivers, the group that had the highest incidence of both back pain and neck-shoulder pain reported the highest stress level and lowest job satisfaction.63 The same study found a strong relationship between back pain and neck-shoulder pain also, indicating that individuals who are predisposed will develop any or several MSDs. Tola et al91 reported that moderate or poor job satisfaction and physical loading factors were significant risk factors for neck and shoulder pain. Bergenudd et al7 found that women with a history of shoulder pain were less satisfied with their jobs than women who did not experience pain. Among possible psychologic stresses at work, the combination of high work demand and low control in particular seems to play an important role in the development of musculoskeletal complaints.36,37
PATHOMECHANISMS Workload The common causative factor in MSDs is mechanical stress on musculoskeletal tissues. Normally, the tissues adapt to mechanical stress; that is, tissues strengthen with increased stress and
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Shoulder and elbow disorders
weaken with less.90 When the stress exceeds the limit of adaption, pathologic changes may occur in the tissue. The risk of developing symptoms may also increase, however, when the physical stress is very low.99 Hagberg and coworkers31,32 suggested three possible pathomechanisms for muscle pain as a result of physical load: mechanical failure, local ischemia, and energy metabolism disturbances. Mechanical failure of the muscles is typically the cause of the muscle soreness that occurs 24 to 48 hours after heavy physical exertion. The pain is due to ruptures of the z-disks and outflow of metabolites from the muscle fibers, which directly or through edema activate pain receptors. Local ischemia produces an accumulation of metabolites within the muscle that is typically a result of static or repeated muscular contraction or repeated muscular injuries. Energy metabolism disturbances occur when the energy demands exceed the production. Because of the prolonged replenishment of intracellular glycogen stores, the resulting development of muscle pain may be delayed up to 46 hours. Edwards22 proposed another model for pathologic changes in the muscle after occupational injury, suggesting that occupational muscle pain might result from a conflict between motor control of the postural muscular activity and that needed for movement or exertion. Some studies have been conducted to provoke pain or discomfort in the shoulder-neck region. Hagberg29 studied the immediate and long-term effect of continuous repetitions of shoulder flexions with and without weights for 1 hour or until exhaustion. He found that all subjects had pain localized to the descending part of the trapezius muscle directly after the experiments. In 14 of 18 experiments, the subjects had pain 24 hours later, and after 48 hours, tenderness occurred in the trapezius muscle and the rotator cuff insertions. Harms-Ringdahl and Ekholm35 studied the effect of prolonged extreme flexion of the neck and found that pain was experienced after 15 minutes and increased with time. Interestingly enough, the pain disappeared within 15 minutes, but in 9 of 10 subjects it recurred the same evening or the following morning and lasted for up to 4 days. Lee and Waikar53 found a correlation between EMG root-mean-square values and discomfort ratings in subjects simulating microscope work for 4 hours.
Muscular fatigue Muscular fatigue is related to the force of the active muscle; that is, fatigue develops faster with higher relative muscle force. Some muscle groups are more prone to fatigue than the neck and trunk extensor muscles.28,77,81 Limits to muscular load for constrained work with a duration of 1 hour or more were proposed by Jonsson39: static muscular load should not exceed 2-5% of MVC, mean load level should be limited to 10-14% of MVC, and peak loads should occur within 50-70% of MVC.
Entrapment Radial tunnel syndrome, also known as resistant tennis elbow, is seen in workers who must perform multiple repetitive motions, especially wrist extensions with or without force. The mechanism behind the condition is the entrapment of the radial nerve involving its sensory branch.
PREVENTION According to Hagberg and Wegman,32 the occupationally related etiologic fraction of neck and upper extremity injuries is high, and therefore a relatively large number could be prevented. Some studies have proved that intervention in working conditions can be successful,76 and rehabilitation of neck and upper limb disorders often fails when not combined with such improvements.23,75 Only a few studies have been able to describe an exposure-effect relationship. For successful prevention, future studies of the quantification of physical exposure and the importance of psychosocial factors are needed.
REFERENCES 1.
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Luopajärvi T, Kuorinka I, Virolainen M, Holmberg M: Prevalence of tenosynovitis and other injuries of the upper extremities in repetitive work. Scand J Work Environ Health Suppl 3:48-55, 1979. MacDonald LA, Karasek RA, Punnett L, Scharf T: Covariation between workplace physical and psychosocial stressors: evidence and implications for occupational health research and prevention. Ergonomics 44(7):696-718, 2001. Maeda K: Occupational cervicobrachial disorder and its causative factors. J Hum Ergol 6:193-202, 1977. Maeda K, Horiguchi S, Hosokawa M: History of the studies on occupational cervicobrachial disorder in Japan and remaining problems. J Hum Ergol 11:17-29, 1982. Magnusson M, Granqvist M, Jonson R, Lindell V, Lundberg U, Wallin L, Hansson T: The loads on the lumbar spine during work at an assembly line in a car factory. The risks for fatigue injuries. Spine 15(8):774-779, 1990. Magnusson M, Wilder DG, Pope MH, Hansson T: Investigation of the long-term exposure to whole body vibration: a 2-country study. Vienna Award for Phys Med 1992. Eur J Phys Med Rehab 3:28-34, 1993. Malker B, Blomgren UB: Occupational diseases 1985. Sweden, Stockholm, 1989, National Board of Occupational Safety and Health, and Statistics [In Swedish]. Malker HSR, Hedlin M, Malker BK, Weiner JA: Occupational musculoskeletal disorders. Identification of risk by ISA statistics. Arbete Och Hälsa 29:1-122, 1990 [In Swedish]. Mansukhani KA, D’Souza C: Ulnar neuropathy at the elbow in diamond sorters. Indian J Med Res (B) 94:433-436, 1991. Maylack FH: Epidemiology of tennis, squash, and racquetball injuries. Clin Sports Med 7:233-243, 1988. Milerad E, Ekenvall L: Symptoms of the neck and upper extremities in dentists. Scand J Work Environ Health 16:129-134, 1990. Murray MP, Gore DR, Gardner GM, Mollinger LA: Shoulder motion and muscle strength of normal men and women in two age groups. Clin Orthop 192:268-273, 1985. Ohlsson K: Neck and upper limb disorders in female workers performing repetitive industrial tasks. Thesis. Lund, Sweden, 1995. Ohlsson K, Attewell R, Paisson B, et al: Repetitive industrial work and neck and upper limb disorders in females. Am J Ind Med 27(5):731-747, 1995. Ohlsson K, Attewell R, Skerfving S: Self-reported symptoms in the neck and upper limbs of female assembly workers. Impact of length of employment, work pace, and selection. Scand J Work Environ Health 15:75-80, 1989. Ohlsson K, Hansson GA, Balogh I, et al: Disorders of the neck and upper limbs in women in the fish processing industry. Occup Environ Med 51:826-832, 1994. Onishi N, Nomura H, Sakai K, Yamamoto T, Hirayama K, Itani, T: Shoulder muscle tenderness and physical features of female industrial workers. J Hum Ergol 5:87-102, 1976. Parenmark G, Alffram PE, Malmkvist AK: The significance of work tasks for rehabilitation outcome after carpal tunnel surgery. J Occup Rehab 2:89-94, 1992. Parenmark G, Malmkvist AK, Örtengren R: Ergonomic moves in an engineering industry: effects on sick leave frequency, labour turnover and productivity. Int J Ind Erg 11:1-10, 1993. Petrofsky JS, Phillips CA: The strength-endurance relationship in skeletal muscle: its application to helmet design. Aviat Space Environ Med 53:365-369, 1982. Punnett L, Robins JM, Wegman DW, Keyserling M: Soft tissue disorders in the upper limbs of female garment workers. Scand J Work Environ Health 11:417-425, 1985. Rafnsson V, Steingrimsdottir OA, Olfsson MH, Sveinsdottir T: Muskuloskeletala besv’r bland islänningar. Nord Med 104:104-107, 1989. Ramazzini B: De morbis artificum, ed 2. Translated by WC Wright. New York, 1713, Hafner Publishing Co. Rohmert W, Wangenheim M, Mainzer J, Zipp P, Lesser W: A study stressing the need for a static postural force model for work analysis. Ergonomics 29:1235-1249, 1986. Rosencrance JC, Cook TM, Zimmermann CL: Active surveillance for the control of cumulative trauma disorders: working modes in the newspaper industry. JOSPT 19(5):267-276, 1994. Salminen JJ, Pentti J, Wickström G: Tenderness and pain in neck and shoulders in relation to type A behaviour. Scand J Rheumatol 20:344-350, 1991. Sato H, Ohashi J: Sex differences in static muscular endurance. J Hum Ergol 18:53-60, 1989. Silverstein B, Viikari-Juntura E, Kalat J: Use of a prevention index to identify industries at high risk for work-related musculoskeletal disorders of the neck, back, and upper extremity in Washington state, 1990-1998. Am J Ind Med 41(3):149-169, 2002. Sjøgaard G, Ekner D, Schibye B, et al: Shoulder-neck problems in sewers. An epidemiologic and work physiologic investigation. Copenhagen, 1987, Arbetsmiljøfondet [In Danish]. Sjøgaard G, Simonsen EB, Jensen BR, Christiansen JU, Pedersen SK: Physical workload and musculoskeletal disorders in sewing machine-operators. In AS Adams, RR Hall, BJ McPhee, MS Oxenburgh, eds: Ergonomics International 88. Proceedings in the tenth congress of the International Ergonomics Association. Sydney, 1988, Ergonomics Society of Australia, pp. 384-386.
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Biomechanics of the Shoulder and Elbow Complex
is implicated in a significant proportion of shoulder pathology, limitation of motion at the AC joint leads to minimal alterations in normal shoulder function.53 Like the SC joint, the AC joint possesses an intraarticular meniscus that enhances the contact area between its two incongruent articular surfaces. The AC joint is stabilized by two sets of ligaments: the AC ligaments are primarily condensations of the AC joint capsule, whereas the coracoclavicular ligaments include the more medial conoid and laterally based trapezoid ligaments.
David I. Pedowitz, David P. Beason, and Louis J. Soslowsky
Scapulothoracic Articulation Not a true joint, the scapulotho-
CHAPTER
5b
During physical activity, the forces acting on the shoulder and elbow have been estimated to be upward of several times body weight.1 Many workplace activities are known to involve heavy manual labor and chronic repetitive motion. Accordingly, the resultant forces and associated pain perceived at the shoulder and elbow can be greater at work due to the stress on the upper extremity when larger loads are applied.25,51 Also of importance are work tasks involving postures nearing or exceeding the normal range of joint motion, stationary postures over extended periods of time, highly repetitive motions, and excessive loading. A fundamental appreciation for the anatomy and biomechanics of the shoulder and elbow complexes serves as an excellent foundation for better understanding these injuries.
THE SHOULDER Anatomic considerations Because the shoulder is the primary conduit through which forces travel from the hand and elbow to the axial skeleton, a thorough understanding of the anatomy is paramount when considering its function and relation to patients’ symptoms. The shoulder complex is essentially composed of three bones, the clavicle, the scapula, and the proximal humerus, which participate in four principal articulations (Fig. 5b.1). Through these joints, the shoulder is acted on by nearly 30 different muscles that either affect the shoulder itself or connect the upper extremity to the spine and the chest wall. The following anatomic descriptions are meant to introduce the critical concepts of shoulder form and function.
Articulations Sternoclavicular Joint The most medial articulation in the shoulder complex, the sternoclavicular (SC) joint is comprised of the medial clavicle and the proximal part of the sternum, the manubrium. This joint serves as a strut connecting the axial skeleton to the upper extremity. The congruity of the articulation is enhanced by an intraarticular disk, which also confers some stability and cushioning for the two bony surfaces. The joint has some limited motion in nearly all directions that is stabilized by surrounding tough ligamentous structures.
Acromioclavicular Joint Similarly to the SC joint, the acromioclavicular (AC) joint is a conduit for forces from the distal upper extremity to the central axis of the body. Although the acromion
racic articulation represents the sliding and rotation between the bony thorax and the scapula. The scapula lies flat on the chest wall and is enveloped by muscle. The complex interaction between the scapular and thoracic muscles affords stability and additional rotation for the scapula on the posterior thorax. This in turn changes the orientation of the glenoid surface and significantly contributes to shoulder range of motion and function. Because the scapulothoracic articulation is not a true joint, it has no discrete ligamentous attachments.
Glenohumeral Joint Often likened to a sideways golf ball on a tee, the glenohumeral articulation allows more range of motion than that of any other major joint in the body. The joint itself is composed of the head of the humerus laterally, which articulates with the glenoid of the scapula medially. The glenoid is shaped like a pear, being broader distally and narrow proximally. It is covered in cartilage that is thin at the center and thickens more peripherally. Along the outer edge of the glenoid is a rim of thick fibrous soft tissue, the glenoid labrum, which deepens the articular surface and also acts as the origin for the long head of biceps (LHB) tendon and the glenohumeral ligaments. The articular surface of the humerus extends medially from the anatomic neck to form approximately one third of an irregularly shaped sphere. Unlike the more static midline structures on the chest wall that lie in the standard anteroposterior plane, the shoulder lies in the scapular plane. Viewed from above, the scapula is anteverted 30 degrees to lie flat on the curved posterior chest wall. This placement is balanced by a 30-degree retroversion of the humeral head. The joint capsule of the shoulder is a thin redundant sleeve of fibrous tissue that extends from the glenoid neck to the anatomic neck and variable areas of the proximal shaft of the humerus. The primary ligamentous structures at the glenohumeral joint are the coracohumeral and the three glenohumeral ligaments (Fig. 5b.2). The coracohumeral ligament (CHL) arises from the coracoid process and attaches to the greater and lesser tuberosities of the humerus. The glenohumeral ligaments are essentially condensations of capsule extending from the rim of the anterior articular surface of the glenoid to the head of the humerus. They provide significant stability to the joint and appear as discrete structures when viewed arthroscopically. The superior glenohumeral ligament extends from the tubercle of the glenoid anterior to the LHB tendon origin and inserts at the proximal tip of the lesser tuberosity. The middle glenohumeral ligament spans the distance between the anterior superior labrum and supraglenoid tubercle to the lesser tuberosity, where it blends with the subscapularis tendon. The strongest and most important of the glenohumeral ligaments, the inferior glenohumeral ligament
Chapter 5b
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Biomechanics of the shoulder and elbow complex
Coracoid process
Figure 5b.1 Bones of the shoulder region, anterior (A) and posterior (B) views.
Clavicle (cut)
Acromion Supraglenoid tubercle Anatomical neck Greater tubercle
Neck
Lesser tubercle
Subscapular fossa
Surgical Neck Infragneloid tubercule
Intertubercylar groove
Deltoid tuberosity
Glenoid cavity of scapula Head of Humerus Scapula Humerus
Condyles
{
Medial Lateral
Radial fossa Lateral epicondyle Capitulum
Trochlea
Coronoid fossa
A
Medial epicondyle Clavicle (cut) Coracoid process Acromion
Supraspinatus fossa Greater tubercle Spine
Head of humerus
Neck
Anatomical neck Surgical neck
Infraspinatus fossa
Infraglenoid tubercle Deltoid tuberosity Scapula Humerus
Olecranon fossa
Lateral epicondyle Trochlea Groove for ulnar nerve
B
Medial epicondyle
Chapter 5b
Anterior view
●
The shoulder
Clavicle
Acromion
Trapezoid ligament
Coracoacromial ligament
Conoid ligament
Supraspinatus tendon (cut)
Coracoclavicular ligament
Coracohumeral ligament Greater tubercle and Lesser tubercle of humerus
Coracoid process
Transverse ligament of humerus Subscapularis tendon Biceps brachii tendon (long Head) Capsular ligaments Figure 5b.2
Capsular and ligamentous structures of the shoulder, anterior view.
(IGHL), arises from most of the anterior glenoid labrum and inserts on the inferior margin of the humeral articular surface, around the anatomic neck of the humerus. Another important structure at the glenohumeral articulation is the coracoacromial arch, the osseoligamentous roof of the shoulder region formed by the coracoid process, the coracoacromial ligament, and the acromion of the scapula. Beneath the coracoacromial arch is the subacromial space, the rotator cuff, the LHB tendon, and the head of the humerus. In varying degrees of shoulder pathology, the undersurface of the acromion or Table 5b.1
leading edge of the coracoacromial ligament can impinge against the rotator cuff and LHB tendons.
Muscles The largest and most appreciable muscle in the shoulder region is the deltoid, which defines the thick rounded contour of the healthy shoulder. The muscle consists of three major sections—anterior, middle, and posterior—that are variably active in different aspects of shoulder motion. Overall, the deltoid is active in all forms of elevation.13 Table 5b.1 describes the muscles of the shoulder.
Muscles of the shoulder
Muscle
Origin
Insertion
Innervation
Action
Deltoid
Lateral one third of clavicle, acromion, and spine of scapula
Deltoid tuberosity of humerus
Axillary n. (C5-C6)
Biceps
Tuberosity of the radius and forearm via bicipital aponeurosis
Musculocutaneous n. (C5-C6)
Subscapularis
Short head: coracoid process of scapula Long head: supraglenoid tubercle of scapula Subscapular fossa of scapula
Shoulder flexion, extension, abduction, some internal/ external rotation Forearm flexion, supination of flexed forearm
Lesser tuberosity of humerus
Supraspinatus Infraspinatus Teres minor Teres major
Supraspinous fossa of scapula Infraspinous fossa of scapula Superior border of lateral scapula Inferior border of lateral scapula
Upper and lower subscapular nn. (C5-C7) Suprascapular n. (C4-C6) Suprascapular n. (C5-C6) Axillary n. (C5-C6) Lower subscapular n. (C6-C7)
Trapezius
Spinous processes of C7-T12 vertebrae
Latissimus dorsi
Spinous processes of T7-T12 vertebrae and iliac crest Lateral surface of ribs 1-8
Serratus anterior
n., nerve; nn., nerves.
Greater tuberosity of humerus Greater tuberosity of humerus Greater tuberosity of humerus Medial lip of intertubercular groove of humerus Lateral one third of clavicle, acromion, and spine of scapula Floor of intertubercular groove of humerus Anteromedial border of the scapula
Spinal accessory n. (CN-XI)
Thoracodorsal n. (C6-C8) Long thoracic n. (C5-C7)
Internally rotates and adducts humerus Abducts humerus Externally rotates humerus Externally rotates humerus Adducts and internally rotates humerus Elevates, retracts, and rotates scapula Extends, adducts, and internally rotates humerus Protracts and rotates scapula medially
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Biomechanics of the shoulder and elbow complex
The rotator cuff is a series of coalesced tendons from four muscles. Moving over the head of the humerus from anterior to posterior, these muscles include the subscapularis, supraspinatus, infraspinatus, and teres minor, which work in concert to stabilize and afford discrete motion of the shoulder. These muscles originate from the scapula and form a condensed tendinous sleeve around the anterior, superior, and posterior aspects of the humeral head. The most anterior muscle, the subscapularis, fans out from the anterior scapula over to the lesser tuberosity of the humerus. When contracted, it acts as an internal rotator of the humerus. At the most superior portion of the cuff is the supraspinatus, the rotator cuff muscle most often implicated in shoulder pathology. In its course to its insertion, it travels beneath the coracoacromial arch, forming the floor of the subacromial space. In this space between the acromion and the supraspinatus tendon is the soft subacromial bursa. The relationship between the supraspinatus and the acromion is important to appreciate, especially when considering conditions like impingement syndrome, where the subacromial space may be appreciably decreased in size, leading to pathology. When contracted, this muscle is a shoulder abductor in the plane of the scapula.6 Moving posteriorly on the cuff, the infraspinatus muscle functions to depress the humeral head and externally rotate the humerus. The final and most posterior rotator cuff muscle, the teres minor, is an external rotator of the humerus. Although thought of primarily as an elbow muscle, the biceps has a role in shoulder stability and pathology also. The biceps is unique in that it is one of the body’s few muscles that originate within a joint. Because of this intraarticular labral origin, the LHB is implicated in a great deal of labral pathology. Although functioning primarily as an elbow flexor and supinator of the forearm, the biceps is believed to play a role in the shoulder as a humeral head depressor and as a significant stabilizer to inferior subluxation.33,60 A number of other parascapular muscles act around the shoulder joint but do not necessarily contribute directly to glenohumeral range of motion or stability. The three largest of these are the trapezius, serratus anterior, and latissimus dorsi muscles. The bulky trapezius muscle mainly functions as a scapular retractor. By doing so, it rotates the inferior angle of the scapula laterally, shrugs the shoulders, and clamps the scapula to the chest wall. Sometimes known as the “boxer’s muscle,” the serratus anterior primarily protracts and medially rotates the scapula, drawing it closer to the posterior chest wall. The serratus anterior is active in all motions of the humerus but more so in flexion. The latissimus dorsi is an enormous back muscle that internally rotates and adducts the humerus and extends the shoulder.
Biomechanics of the glenohumeral joint Kinematics This concise discussion of biomechanics focuses on the primary source of motion at the shoulder, the glenohumeral joint. It should be noted however, that the AC, SC, and scapulothoracic articulations do also have roles, albeit less so, in the overall mechanics of the upper extremity.
Glenohumeral kinematics describes the motion of the humeral head in the glenoid cavity without consideration of forces contributed by surrounding musculature. This description can be for either two-dimensional planar motion or three-dimensional spatial motion.49 Planar motion of the glenohumeral joint can be divided into three modes of articulation: sliding, spinning, and rolling41 (Fig. 5b.3). In sliding, the contact point is constant on the translating humeral head but is always changing on the stationary glenoid cavity. The center of rotation is the center of curvature of the glenoid. During spinning, the contact point is always changing on the rotating humeral head but is constant on the stationary glenoid cavity. The center of rotation for spinning is the center of curvature of the humeral head. In rolling, the point of contact is always changing on both the humeral head and the glenoid cavity, with the center of rotation being the contact point itself. Any two of these three divisions can be combined to describe the planar motion of the glenohumeral joint.41 Spatial motion can best be explained in terms of degrees of freedom. In general, an unconstrained rigid body has six degrees of freedom—three translations and three rotations about the orthogonal x-, y-, and z-axes (Fig. 5b.4). In its normal range of motion, the glenohumeral joint is capable of three rotations about three orthogonal coordinate axes and thus has three degrees of freedom. In terms of joint motion, these three rotations are defined as flexion/extension, abduction/adduction, and internal/external rotation. These motions are constrained by soft tissues, ligaments, articulations, and muscles. In flexion/extension, the humerus can generally be moved in the sagittal plane through a range of about 170 degrees.41 Abduction/adduction can be achieved over a range of 180 degrees41 in the coronal plane. The range of motion for internal/external rotation totals approximately 150 degrees.41 Many overhead motions are achieved through combinations of flexion/extension and abduction/ adduction, with additional aid from the scapulothoracic articulation at motion extremes. This type of overhead motion has been reported as a source of numerous shoulder injuries, including those suffered during occupational tasks.22
Constraint The bony architecture of the shoulder affords this joint an exceptional range of motion. It is achieved, however, only with an obligatory reduction in its biomechanical stability. In compensation, both static and dynamic stabilizers help orchestrate a balance between mobility and stability. When viewing plain radiographs, the glenohumeral joint appears to function like a sphere articulating on a flat glenoid surface. Historically, it was therefore assumed that the osseous geometry of the joint surfaces provided little if any inherent stability to the shoulder. Cadaveric studies, however, have determined that the articular geometry of the shoulder does play a substantial role in stabilization. Using gross measurements and magnetic resonance imaging, investigators have documented that the radius of curvature of the average glenoid is about 2 mm greater than that of the corresponding humeral head.28 Using stereophotogrammetry, another center reported similar findings and determined that the mating humeral head and glenoid articular surfaces were in fact congruent.58 When the articular cartilage surfaces were analyzed, furthermore, it was
Chapter 5b
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The shoulder
Figure 5b.3 Planar glenohumeral articulation. Included are spinning, rolling, and sliding motions. These motions may occur either in isolation or in combination. (From Zuckerman JD, Matsen FA: Biomechanics of the shoulder. In M Nordin, VH Frankel, eds: Biomechanics of the musculoskeletal system. Philadelphia, 1989, Lea & Febiger.)
z
3 6 2 y 5 1
4
x Figure 5b.4 Orthogonal coordinate axes, illustrating six degrees of freedom—three translations (1-3) and three rotations (4-6).
observed that the actual articulating surfaces conformed more than previously thought.58 Enlarging the articulating area is thought to add to stability by decreasing the potential for humeral head translation and by increasing what Fukuda and colleagues17 referred to as the “constraining wall height” of the joint. Using this technique57 and Fugi Prescale film,69 contact areas within the glenohumeral joint have been documented also, ranging from approximately 0.75 cm2 with the arm at the side and 5 cm2 at 90 degrees of abduction. Additionally, contact pressure within the joint was found to decrease with increasing abduction to 90 degrees.69 The remaining static stabilizers of the shoulder joint include the glenoid labrum, the joint capsule, and the glenohumeral and coracohumeral ligaments. These coordinate to resist joint translation primarily by preventing displacement through their presence and secondarily by imparting increased joint contact forces resisting the displacement.24 The first of these structures, the glenoid labrum, is a meniscus-like thickening of fibrous tissue that is triangular in cross-section and surrounds the rim
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Shoulder Anatomy and Biomechanics
A
Figure 5b.5 The glenoid labrum. The labrum’s role can be thought of as extending the surface area of the socket, much as adding to the bank of a road deepens a curve. (From Flatow E: Shoulder anatomy and biomechanics. In M Post, L Bigliani, E Flatow, R Pollock, eds: The shoulder: operative technique. Philadelphia, 1998, Lippincott, Williams & Wilkins.)
B
of the glenoid cavity (Fig. 5b.5). Previously thought to be composed of fibrocartilage, the labrum is mostly dense fibrous tissue with few elastic fibers.43 Often conceptualized as a bumper that prevents the humeral head from excursion out of the glenoid, its role in enhancing the stability of the glenohumeral joint has been questioned, as some investigators have found that it offers little in overall shoulder stability.43,63 As a whole, however, the labrum does play some role in shoulder constraint, but its contribution is likely complementary.41 The joint capsule of the shoulder is a relatively thin sheet of fibrous tissue. Depending on the position of the shoulder, the capsule imparts a variable contribution to glenohumeral joint stability. In general, anterior shoulder structures are taut when the arm is externally rotated. Superior, inferior, and posterior structures are accordingly tightened when the arm is adducted, abducted, and internally rotated, respectively. The most obvious and important portions of the shoulder capsule that confer stability are sometimes referred to as the capsule-ligament complex. This complex consists of superior, middle, and inferior portions that along with the CHL define the ligamentous structures providing constraint to the shoulder joint41 (Fig. 5b.6). In general, the capsular structures participate in mechanically stabilizing the joint at the extremes of motion, though they may also have roles in proprioception. Because it extends from the coracoid process to the lesser tuberosity, the CHL is thought to participate in suspending the humerus in the glenoid when the arm is at the side. Its role in stability, however, remains controversial.60 The superior glenohumeral ligament is a fibrous structure that becomes tight when the arm is adducted at the side. As it tightens, it acts primarily as an inferior stabilizer and likely functions along with the CHL and the rotator cuff to prevent inferior translation of the humeral head on the glenoid.48,68 Often well developed, the
middle glenohumeral ligament has been demonstrated to be a significant constraint to anterior displacement of the humerus.14,43 Along with the anterior capsule, the middle glenohumeral ligament becomes taut when the arm is abducted and externally rotated. The IGHL is the ligament thought to be responsible for most of the shoulder’s static stability. Its geometry has classically been described as having three distinct components—a superior
Supraspinatus Long head of triceps Anterior View Posterior View SGHL
Intraspinatus
MGHL Subscapularis
Teres minor Posterior axillary pouch of IGHL Long head of triceps
Superior band of IGHL Anterior axillary pouch of IGHL Capsule
Figure 5b.6 The glenohumeral ligaments. The glenohumeral ligaments are thickenings in the capsule of the shoulder and function as passive check reins, particularly at the extremes of motion.
Chapter 5b
band and anterior and posterior axillary pouches.65 The geometry and mechanical properties of these distinct areas of the IGHL suit it well for its role as the primary static anterior stabilizer of the glenohumeral joint.8 Slack and redundant with the arm adducted, the IGHL is the primary static restraint to anteroinferior subluxation, particularly in abduction and external rotation, a position associated with increased anterior instability.9 In this position the more anterior structures become taut, whereas in internal rotation the posterior aspect of the IGHL is tense. The dynamic stabilizers of the shoulder joint include the rotator cuff, biceps, and deltoid muscles. Directly they act as a bulky barrier with inherent passive muscle tension that resists translation of the humeral head, and they play an important role in stability by providing compressive forces on the humerus into the glenoid socket. Indirectly, the dynamic stabilizers exert their effect by moving the joint into positions that tighten the capsular-ligamentous complex,41 thus engaging these stabilizing structures. As described in the section on anatomy, the rotator cuff is a series of four muscles that coalesce to form a tendinous arc of tissue around the glenohumeral joint. In addition to affording the shoulder with discrete motions, these muscles also provide stability. Anteriorly, the subscapularis muscle forms a musculotendinous curtain from the scapula to the lesser tuberosity. In doing so, it is thought to be the most important dynamic anterior stabilizer.15 This stability is greatest in external rotation and from 0 to 45 degrees of abduction.36,65 At 90 degrees of abduction, the IGHL seems to play the most important role.65 Of all the rotator cuff muscles, the subscapularis provides the most resistance to posterior subluxation when the arm is in forward flexion.10 Superiorly, the supraspinatus muscle has been reported to be an important restraint to inferior translation of the humerus. This action has been observed in cadaveric specimens where the supraspinatus was found to be an inferior stabilizer more effective than any other cuff muscle.60 Investigators demonstrated that moving posteriorly on the cuff, the infraspinatus, the teres minor, and occasionally the supraspinatus function together with the subscapularis to impart notable posterior stabilization.10,46 A complete analysis of the relative contributions of the rotator cuff muscles to glenohumeral joint stability is beyond the scope of this text. It is notable, however, that these muscles do not simply exist and function in isolation. Rather, they have been demonstrated to function in concert, with both anterior and posterior force coupling that yields enhanced joint stability.54 The contribution of the biceps muscle to overall glenohumeral stability is also important. As the LHB tendon courses over the curved head of the humerus, it acts like a cable wrapping around a pulley. When the biceps is activated, it compresses the humeral head into the glenoid.4 Additionally, the biceps has been suggested to be as important as the rotator cuff to glenohumeral stability.29 Because of its size (20% of overall shoulder muscle mass), the deltoid’s contribution to shoulder stability is thought to be noteworthy but remains undefined.7
Kinetics In contrast to kinematics, glenohumeral kinetics is the study of joint motion with respect to the forces responsible for it. The muscles and ligaments of the rotator cuff carry appreciable loads
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161
in day-to-day activities and in strenuous work tasks such as heavy lifting, abduction, and overhead use. The loading that occurs in the glenohumeral joint during normal motion has been reported to be as high as 0.89 times body weight at 90 degrees of abduction, and it is increased appreciably when weight is held.50 Most of the strength and gross motion at the joint is facilitated by the massive deltoid muscle, the three primary sections of which function differently depending on the direction of a force and the arm position when a load is applied. In general, the more anterior portion is important in forward elevation, whereas the posterior portion plays a significant role in posteriorly directed motion such as extension. The middle fibers of the deltoid make relative contributions to both of these movements but are involved mostly in shoulder abduction strength, to which the deltoid contributes over 60%.13 Although debated, the relative contribution of the supraspinatus to overall abduction of the shoulder has more recently been shown to be responsible for between 19% and 33% of the total abduction force generated at the shoulder.30 Its length-tension curve demonstrates maximum force at about 30 degrees of elevation.5 In selective nerve block studies, the infraspinatus and teres minor muscles have been found responsible for as much as 60% and 45% of the external rotation force that can be generated at the shoulder, respectively.13 The subscapularis muscle is the only primary internal rotator of the shoulder and as such is responsible for most of the force in that movement.
Mechanical properties of articular cartilage and ligaments When considering shoulder biomechanics, it is important to understand the mechanical behavior of the soft tissues (namely ligaments and cartilage) associated with the glenohumeral joint, the subject of various experimental techniques (Table 5b.2). Tests of the mechanical properties of glenohumeral articular cartilage have included both indentation44 and tensile testing.70 On average, the aggregate modulus for glenohumeral joint articular cartilage ranges from roughly 0.5 to 0.9 MPa.44 Compressive and shear properties of articular cartilage are important because of the nature of their role in dynamic articulating surfaces. Partly because ligaments are anisotropic, in that they have different properties in the longitudinal and transverse directions, and partly because their primary function is joint stabilization typically through tensile loading, the most common method of
Table 5b.2 Mechanical properties of some key glenohumeral ligaments
Ligament
Failure load (N)
Superior 101.911 glenohumeral Inferior — glenohumeral Coracohumeral 359.811
Stiffness (N/mm)
Ultimate stress (MPa)
Elastic modulus (MPa)
17.411
—
—
—
5.2, 5.5, 5.6* 38.7, 30.3, 41.9* — —
36.711
*Values are for superior, anterior, and posterior regions, respectively.8
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Biomechanics of the shoulder and elbow complex
Linear region
Yield/failure
Stress
Toe region
●
Strain Figure 5b.7 Typical tensile test of a ligament, showing the toe, linear, and yield/failure regions.
obtaining mechanical properties is the quasistatic tensile test. However, more sophisticated methods have enabled precise two-dimensional analysis of the glenohumeral joint. In situ strain fields in the anteroinferior shoulder capsule have been quantified in this way using stereoradiogrammetry, showing that strains are generally higher on the glenoid side of the capsule than on the humeral side.35,37 All biologic soft tissues demonstrate both nonlinear and viscoelastic mechanical behavior under loading. The nonlinearity is characterized initially by a relatively large increase in elongation with respect to load (Fig. 5b.7). In tensile testing, this “toe” region represents the straightening and aligning of collagen fibers in the longitudinal axis, that is, the direction of loading. This is followed by a linear region, over which the mechanical properties such as stiffness are typically evaluated. The ensuing region of nonlinear yield culminates with the failure of the specimen. In addition to behaving nonlinearly, soft tissues are also considered viscoelastic due to the rate dependence of their mechanical properties. When loaded rapidly, a ligament tends to be stiffer than when loaded at a lower rate. IGHL regions have been shown to have up to 62% increased modulus when loaded an order of magnitude more rapidly.44 A phenomenon associated with soft tissue viscoelasticity is the hysteresis effect. When a ligament is cyclically loaded and returned to its resting state, the load-deformation response shifts until equilibrium is eventually reached after 10-20 cycles.38 For this reason, biomechanical testing should begin with a period of preconditioning in which the specimen is cyclically loaded within its normal physiologic range. Although biomechanical studies demonstrated that soft tissue properties change as a function of age38 and epidemiology indicates that shoulder and upper limb disorders tend to arise over time,34 age has not shown a consistently strong association with shoulder tendonitis in the workplace environment. This is due partly to older workers often leaving their jobs because of the injury, resulting in “survivor bias.”23
addressed by testing them. Recently, animal models have gathered significant interest and use to address questions about the biomechanics of the shoulder and its injuries. The most fundamental issue that must be addressed when selecting any animal model is its biofidelity with respect to the body region of interest. For the shoulder, several animal models have been used in studying tendon and rotator cuff injury and repair. New Zealand white rabbits, for example, have been used to study muscle healing characteristics after supraspinatus tendon reattachment.39,66 Other works have investigated rotator cuff repair both in vitro and in vivo using infraspinatus tendons of sheep.18,19 Soslowsky et al59 set out to identify an effective animal model for studying rotator cuff injuries by examining anatomic characteristics of the shoulder in several different species. In an analysis involving 34 criteria applied to 37 animals, the rat emerged as the only model to satisfy all criteria while still being practical for experimental research. The most distinguishing characteristic that makes the anatomy of the rat shoulder comparable with that of a human is the position of the acromion and its associated enclosed arch in relation to the supraspinatus tendon.59 SpragueDawley rats have since been used effectively in numerous investigations into the roles of overuse and extrinsic factors in rotator cuff injuries. In the laboratory setting, overuse activity has produced a reproducible injury in the rat shoulder comparable with that seen clinically in the rotator cuff.61 Injuries stemming from overuse in combination with extrinsic compression have resulted in relatively high maximum stresses and elastic moduli when compared with each of the two factors alone, indicating that rotator cuff tendinosis is not typically attributable to a single factor.62
Prevention of disability through ergonomics Three of the most prominent risk factors to emerge from studies of workplace ergonomics are static or extreme posture,25,51 cyclical occupational motions,16,21 and external loading.16,47 The risk of shoulder disorder has been reported to be two to three times higher in occupations requiring abduction or flexion beyond 90 degrees for at least 10% of the time performing the task.51 This combination of awkward shoulder posture and long time periods has been identified as a key risk factor for disorders.56 The occurrence of shoulder tendinitis has been found to be two to three times higher in workers with highly repetitive or cyclical work tasks involving the upper limbs.16 External hand loads in combination with humeral abduction have been linked to increased rotator cuff muscle pressure, which can have detrimental effects on the shoulder.47 Conversely, when an occupation does not require appreciable loading, the risk of shoulder tendinitis is lower.16 With sufficient effort focused on these issues in the workplace through improved ergonomic conditions, resulting shoulder disorders may be appreciably reduced.
THE ELBOW Anatomic considerations
Animal models Although cadavers have proven beneficial in experimental biomechanics research, certain important questions cannot be
Complex in its articular geometry, the elbow is an important link in the lever arm chain of the upper extremity that facilitates a
Chapter 5b
Condyle
{
●
The elbow
Medial Lateral
Lateral supracondylar crest
Humerus Medial epicondyle Capitulum
Humerus Medial supracondylar crest Coronoid fossa
Radial fossa Lateral epicondyle
Tuberosity
Medial epicondyle Capitulum Head Neck Tuberosity Radius
A
Trochlea Head Neck
Radius
Trochlea Coronoid process
Ulna
Radial notch of ulna
Tuberosity Coronoid process
Tuberosity Ulna
B
Olecranun
Trochlear notch
Ulnar collateral ligament Annular ligament
C Figure 5b.8 Bones of the elbow, anterior (A) and medial (B) views. The orientation of the three components of the medial collateral ligament include the anterior, posterior, and transverse bundles.
broad range of motion, the absence of which causes significant functional impairment. A working knowledge of the elbow’s anatomy is thus important in any effort to understand the biomechanics at this articulation. The elbow is a trochleoginglymoid joint composed of three bones; the distal humerus and the proximal ulna and radius (Fig. 5b.8). The three articulations at the elbow are the ulnohumeral, radiohumeral, and radioulnar joints.
Articulations Ulnohumeral Joint As the metaphyseal bone of the distal humerus flares out distally, it forms two supracondylar regions that end in medial and lateral epicondyles. These epicondyles flank two odd-shaped asymmetric condyles. The condyles compose the distal articular surface of the humerus: the trochlea medially and the capitellum laterally. The ulnohumeral joint is essentially a hinge governed by the intimate matching geometry of the trochlea and proximal ulna. The most constrained portion of the elbow joint, this articulation allows only flexion and extension. On the humeral side, the trochlea resembles a spool of thread with broad ends (of which the medial is larger) that converge into a narrow trochlear groove. In the frontal plane the trochlea has approximately 6 degrees of valgus tilt that helps dictate the carrying angle of the normal elbow. There are two
depressions on the distal humerus that participate in the ulnohumeral joint as well: the coronoid and olecranon fossae. As the joint goes through flexion and extension, the olecranon and coronoid fossae accommodate their similarly named processes on the proximal ulna. The proximal ulna is composed of two arced processes—the olecranon and coronoid—separated from each other anteriorly by the greater and lesser sigmoid notches. A lateral indentation in the lesser sigmoid notch, the radial notch, provides articulation with the proximal radius. Viewed laterally, the proximal ulna resembles a claw that tightly grasps the trochlea of the distal humerus. The olecranon is a large posterior bony process that provides the posterior articulation for the ulnohumeral joint, prevents posterior displacement of the humerus, and serves as the site of attachment for the triceps tendon. Anteriorly, the coronoid provides the anterior articular surface of the joint, prevents anterior translation of the humerus, and serves as the site for the distal insertion of the brachialis muscle. Although strong transverse and oblique fibers do exist, the capsule of the elbow is generally weak and reinforced primarily by strong ligaments medially and laterally that stabilize the joint against varus and valgus forces (Fig. 5b.8b). On the medial side of the elbow, the medial collateral ligament (MCL) (often referred to as the ulnar collateral ligament) has a transverse
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Biomechanics of the shoulder and elbow complex
ligament and an anterior and posterior bundle. Laterally, the radial collateral ligament complex is composed of the annular ligament, radial collateral ligament proper, and lateral ulnar collateral ligament (LUCL). The annular ligament is a strong ring of tissue that loops around the radial head to hold it against the proximal ulna at the proximal radioulnar joint. The radial collateral ligament extends from the lateral epicondyle to the annular ligament and is taut throughout most of the normal range of motion at the elbow. Invariably present, the LUCL extends from the lateral epicondyle to the supinator crest on the proximal ulna.
Radiohumeral Joint The medial condyle of the distal humerus, the capitellum (l. little head), is spherical and covered by articular cartilage. At the radiocapitellar joint it articulates with the cylindrical head of the radius. The radiocapitellar joint allows flexionextension and pronation-supination and also undergoes varus and valgus moments. As the forearm rotates into either pronation or supination, the radial head spins underneath the capitellum.
Radioulnar Joint The radial head is bound to the ulna by the annular ligament and, due to its location, acts as a primary restraint to valgus force. The proximal radioulnar joint allows pronation and supination. Like the radiohumeral and ulnohumeral joints, this joint is enveloped in the elbow capsule.
Muscles The muscles acting on the elbow play defined roles in facilitating its motion. In general, muscles crossing the elbow on the anterior surface of the cubital fossa are elbow flexors, whereas those located posteriorly function to extend the elbow. As described in the shoulder section above, the biceps muscle crosses both the shoulder and the elbow joints. Its function at the elbow is to flex the extended elbow and supinate the flexed forearm, as in tightening a screw with the right hand. Like the biceps, the brachioradialis and brachialis muscles flex the elbow. Posteriorly on the elbow is the triceps brachii muscle, its primary extensor. Composed of a medial lateral and long head, the muscle extends the entire length of the posterior brachium to insert as a thick Table 5b.3
tendon on the olecranon process of the ulna. Adjacent to the triceps insertion is a small triangularly shaped muscle called the anconeus that is minimally involved in forearm extension. The epicondyles of the distal humerus provide the origin for a number of forearm muscles that act mostly on the wrist. Table 5b.3 describes the muscles of the arm.
Biomechanics of the elbow Kinematics In terms of spatial motion, the elbow is considered to have two degrees of freedom, flexion/extension and supination/pronation. Flexion/extension is essentially a hinge-like motion that occurs at the ulnohumeral joint. This motion defines the carrying angle, that formed by the ulna and the humerus. The rotational axis for flexion/extension is formed by the trochlea and capitellum. The normal range of motion in flexion, from 0 to 150 degrees, is restricted by bony impingement of the radial head and fossa, impact between the coronoid process and fossa, and muscular tension from the triceps.2 Extension is limited by the impingement of the olecranon process on the olecranon fossa and tension of the anterior and medial ligaments and flexor muscles.31 For supination/pronation, the axis of rotation passes through the distal ulna and the center of the radial head.2 The elbow is normally capable of approximately 75 degrees of pronation and 85 degrees of supination, or 160 degrees of total motion, limited primarily by muscles and secondarily by ligaments.2
Constraint In addition to the aforementioned stability afforded by the unique topography of the distal humerus and proximal ulna, additional constraint is provided by the elbow capsule and the periarticular ligaments.3,45 At the elbow, the medial and lateral ligamentous complexes provide most of the additional stability to the bony configuration. On the medial side of the elbow is the MCL. Cadaveric studies have determined that the anterior band of the MCL is the most important section of the ligament because it is the primary stabilizer against a valgus force.42
Muscles of the arm
Muscle
Origin
Insertion
Innervation
Action
Biceps brachii Brachialis
Short head: coracoid process of scapula Long head: supraglenoid tubercle of scapula Distal one half of anterior humerus Tip of coracoid process
Triceps brachii
Long head: infraglenoid tubercle Lateral head: posterior surface of humerus superior to spiral groove Medial head: posterior surface of humerus inferior to spiral groove Lateral epicondyle of humerus
Musculocutaneous n. (C5-C6) Musculocutaneous n. (C5-C6) Musculocutaneous n. (C5-C7) Radial n. (C6-C8)
Forearm flexion, supination of flexed forearm Forearm flexion
Coracobrachialis
Tuberosity of the radius and forearm via bicipital aponeurosis Coronoid process and tuberosity of ulna Middle third of medial surface of humerus Proximal olecranon process
Lateral surface of olecranon
Radial n. (C7-C8, T1)
Assists triceps in forearm extension
Anconeus
n., nerve.
Flexes and adducts humerus Extends forearm
Chapter 5b
Clinically, this becomes particularly relevant when the radial head (a secondary valgus stabilizer) is no longer functioning (e.g., due to fracture). The lateral collateral ligamentous complex functions mostly as a varus stabilizer of the elbow. The major component of the radial collateral ligament complex contributing stability to varus and rotatory stability of the elbow is the LUCL.2 Overall, the LUCL specifically is responsible for most of the lateral stabilization.2 In addition to holding the radius in the proximal radioulnar joint, the annular ligament also provides some stability against varus and valgus stress.55
Kinetics Contact in the elbow is typically described with respect to the ulnohumeral joint. The three most common methods of contact measurement in the elbow are silicone casting, cartilage staining, and Fugi Prescale film. Having evaluated all three techniques, Stormont et al64 identified silicone casting as the optimal method for studying elbow contact. In a study using a wax casting technique,20 contact was reported to be concentrated on the medial part of the lower trochlear notch with the elbow in full extension. At 90 degrees of flexion, the contact appeared predominantly as a band extending from the lower medial to upper lateral trochlear notch. At full flexion, the band of contact area increased, and contact between the radial head and capitulum became more pronounced.20 It was noted in a different study that with increased external load, contact area increased and its location became increasingly lateral.64 Although experimentally difficult on curved articulations, the use of Fugi Prescale film provides measurements of contact pressure as well as area. Like the shoulder, the mechanical behavior of elbow ligaments is nonlinear and viscoelastic, although there is substantially less information available. Properties for the medial and radial collateral ligamentous complexes, however, have been reported.52 The radial collateral ligament is reported to have a mean ultimate stress of 15.9 MPa and elastic modulus of 54.3 MPa. The MCL has been found to be stronger and less elastic, with ultimate stresses of 20.7 and 19.2 MPa and elastic moduli of 117.8 and 96.8 MPa for the anterior and posterior bundles, respectively. In the workplace, flexion/extension is typically involved in lifting tasks, whereas supination/pronation in combination with force exertion has been cited as a risk factor for medial and lateral epicondylitis in tasks involving repeated twisting motions.21 As with the shoulder, it has been shown that workers in high-repetition jobs are two to three times more likely to develop conditions such as elbow tendinitis than those performing low-repetition tasks.34
NOVEL DEVELOPMENTS AND FUTURE DIRECTIONS An important area that is gaining momentum in orthopedic biomechanics is in the field of tissue engineering, which strives to combine biologic and mechanical elements. Specifically, the concept of functional tissue engineering mandates consideration of mechanical properties and functional capabilities when dealing with tissues that are structurally vital.12 In particular, functional
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References
tissue engineering approaches are making significant strides toward improving the healing response of injured tissues such as the rotator cuff or in creating replacement structures such as for ligaments and joints. Investigators have begun using resorbable tissue scaffolds in the hope of regenerating new tendon. Using materials like porcine small intestine submucosa, human dermis, and woven starch fabrics, some centers have documented encouraging results in engineering new tissue growth. Advances in these areas will likely yield significant benefit to the patient population in the near future. The use of in vivo techniques and measurements in lieu of cadaveric investigations is another developing trend. In vivo measurements of loading and motion in both normal and abnormal states will further our understanding of the mechanics of the shoulder and elbow joints. Noninvasive techniques have begun to play a more important role in enhancing our understanding of upper extremity biomechanics. Together with three-dimensional reconstructed computer-aided tomograms, some investigators have used in vivo fluoroscopic imaging of the shoulder and elbow to gain exciting new insight into their kinematics. Using these techniques, they have gained a more comprehensive appreciation for the loading, contact area, and dynamic motion at these articulations. This information has helped in the development of better total joint arthroplasties. Ongoing work is making use also of magnetic resonance imaging to measure tendon strain fields in the shoulder. Another area that has seen recent development and is likely poised for significant advancement is in the use of computer models of the shoulder complex. Based on original work by both Högfors et al26,27 and van der Helm,67 efforts to combine finite element and three-dimensional modeling have yielded new methodologies for investigating the shoulder. Using a six-degreeof-freedom electromagnetic tracking device, investigators have obtained complete kinematic descriptions of shoulder motion.40 Additionally, with these three-dimensional models, investigators have been able to estimate muscle attachment sites and reliably apply them to geometric bone models.32 As the horizon for new advances in orthopedic bioengineering broadens, we hope to continue to find even more efficacious applications toward the prevention and treatment of injury and disability at the shoulder and elbow.
REFERENCES 1. An KN, Chao EYS, Kaufman KR: Analysis of muscle and joint loads. In VC Mow, WC Hayes, eds: Basic orthopaedic biomechanics, ed 2. Philadelphia, 1997, Lippincott-Raven, pp. 1-35. 2. An KN, Morrey BF: Biomechanics of the elbow. In BF Morrey, ed: The elbow and its disorders, ed 3. Philadelphia, 2000, WB Saunders, pp. 43-60. 3. An KN, Morrey BF, Chao EYS: The effect of partial removal of proximal ulna on elbow constraint. Clin Orthop Relat Res 209:270-279, 1986. 4. Andrews JR, Carson WG Jr, McLeod WD: Glenoid labrum tears related to the long head of the biceps. Am J Sports Med 13:337, 1985. 5. Atwater AE: Biomechanics of overarm throwing movements and of throwing injuries. Exerc Sport Sci Rev 7:43-85, 1979. 6. Basmajian JV, Bazant FJ: Factors preventing downward dislocation of the adducted shoulder joint. An electromyographic and morphological study. Am J Orthop 41A: 1182-1186, 1959. 7. Bassett RW, Browne AO, Morrey BF, An KN: Glenohumeral muscle force and moment mechanics in a position of shoulder instability. J Biomech 23:405-415, 1990. 8. Bigliani L, Kelkar R, Flatow E, Pollock R, Mow V: Glenohumeral stability: biomechanical properties of passive and active stabilizers. Clin Orthop Relat Res 330:13-30, 1996.
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Bigliani LU, et al: Tensile properties of the inferior glenohumeral ligament. J Orthop Res 10:187-197, 1992. Blasier RB, Soslowsky LJ, Malicky DM, Palmer ML: Posterior glenohumeral subluxation: active and passive stabilization in a biomechanical model. J Bone Joint Surg 79(3):433-440, 1997. Boardman ND, Debski RE, Warner JJ, Taskiran E, Maddox L: Tensile properties of the superior glenohumeral and coracohumeral ligaments. J Shoulder Elbow Surg 5: 249-254, 1996. Butler DL, Goldstein SA, Guilak F: Functional tissue engineering: the role of biomechanics. J Biomech Eng 122:570-575, 2000. Colachis SC, Strohm BR, Brechner VL: Effects of axillary nerve block on muscle force in the upper extremity. Arch Phys Med Rehabil 50(11):645-647, 1969. DePalma AF, Callery G, Bennett GA: Variational anatomy and degenerative lesions of the shoulder bone. AAOS Instruct Course Lect 16:255, 1949. DePalma AF, Coker AJ, Probhaker M: The role of the subscapularis in recurrent anterior dislocation of the shoulder. Clin Orthop Relat Res 54:35-49, 1969. Frost P, Bonde JP, Mikkelson S, Andersen JH, Fallentin N, Kaergaard A, Thomsen JF: Risk of shoulder tendinitis in relation to shoulder loads in monotonous repetitive work. Am J Indust Med 41:11-18, 2002. Fukuda K, Chen CM, Cofield RH, Chao EYS: Biomechanical analysis of stability and fixation strength of total shoulder prostheses. Orthopedics 11:141-149, 1988. Gerber C, Schneeberger AG, Beck M, Schlegel U: Mechanical strength of repairs of the rotator cuff. J Bone Joint Surg 76-B(3):371-380, 1994. Gerber C, Schneeberger AG, Perren SM, Nyffeler R: Experimental rotator cuff repair. J Bone Joint Surg 81-A(9):1281-1290, 1999. Goel VK, Singh D, Bijlani V: Contact areas in human elbow joints. J Biomech Eng 104(3):169-175, 1982. Grieco A: Application of the concise exposure index (OCRA) to tasks involving repetitive movements of the upper limbs in a variety of manufacturing industries: preliminary validations. Ergonomics 41(9):1347-1356, 1998. Grieco A, Molteni G, De Vito G, Sias N: Epidemiology of musculoskeletal disorders due to biomechanical overload. Ergonomics 41(9):1235-1260, 1998. Hales TR, Bernard BP: Epidemiology of work-related musculoskeletal disorders. Orthop Clin North Am 27(4):679-709, 1996. Harryman DT, Sidles JA, Clark JM: Translation of the humeral head on the glenoid with passive glenohumeral motion. J Bone Joint Surg 72(9):1334-1343, 1990. Herberts P, Kadefors R, Högfors C, Sigholm G: Shoulder pain and heavy manual labor Clin Orthop Relat Res (198):166-178, 1984. Högfors C, Peterson B, Sigholm G, Herberts P: Biomechanical model of the human shoulder. II. Shoulder rhythm. J Biomech 24(8):699-709, 1991. Högfors C, Sigholm G, Herberts P: Biomechanical model of the human shoulder. I. Elements. J Biomech 20(2):157-166, 1987. Iannotti JP, Gabriel JP, Schneck SL, Evans BG, Misra S: The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders. J Bone Joint Surg 74A(4):491-500, 1992. Itoi E, Newman SR, Ruechle DK, Morrey BF, An KN, et al: Dynamic anterior stabilisers of the shoulder with the arm in abduction. J Bone Joint Surg 76b(5):834-6, 1994. Itoi E, Minagawa H, Sato T, Sato K, Tabata S: Isokinetic strength of the shoulder with tears of the supraspinatus tendon. J Bone Joint Surg 79b(1):77-82, 1997. Kapandji IA: The physiology of the joints. Volume 1: Upper limb, ed 2. Edinburgh, 1982, Churchill Livingstone. Kaptein BL, van der Helm FCT: Estimating muscle attachment contours by transforming geometrical bone models. J Biomech 37:263-273, 2004. Kumar VP, Satku K, Balasubramaniam P: The role of the long head of biceps brachii in the stabilization of the head of the humerus. Clin Orthop Relat Res 244:172-175, 1989. Latko WA, Armstrong TJ, Franzblau A, Ulin SS, Werner RA, Albers JW: Cross-sectional study of the relationship between repetitive work and the prevalence of upper limb musculoskeletal disorders. Am J Indust Med 36:248-259, 1999. Malicky DM, Kuhn JE, Frisancho JC, Lindholm SR, Raz JA, Soslowsky LJ: Neer Award 2001. Nonrecoverable strain fields of the anteroinferior glenohumeral capsule under subluxation. J Shoulder Elbow Surg 11(6):529-540, 2002. Malicky DM, Soslowsky LJ, Blasier RB, Shyr Y: Anterior glenohumeral stabilization factors: progressive effects in a biomechanical model. J Orthop Res 14(2):282-288, 1996. Malicky DM, Soslowsky LJ, Kuhn JE, Bey MJ, Mouro CM, Raz JA, Liu CA: Total strain fields of the antero-inferior shoulder capsule under subluxation: a stereoradiogrammetric study. J Biomech Eng 123(5):425-431, 2001. Martin RB, Burr DB, Sharkey NA: Mechanical properties of ligament and tendon. In RB Martin, DB Burr, NA Sharkey, eds: Skeletal tissue mechanics. New York, 1998, Springer, pp. 309-348. Matsumoto F, Uhthoff HK, Trudel G, Loehr JF: Delayed tendon reattachment does not reverse atrophy and fat accumulation of the supraspinatus—an experimental study in rabbits. J Orthop Res 20:357-363, 2002. Meskers CGM, Vermeulen HM, de Goot JH, van der Helm FCT, Rozing PM: 3D shoulder position measurements using a six-degree-of-freedom electromagnetic tracking device. Clin Biomech 13:280-292, 1998.
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Morrey BF, Itoi E, An KN: Biomechanics of the shoulder. In CA Rockwood, FA Matsen, eds: The shoulder, ed 2. Philadelphia, 1998, Saunders, pp. 233-276. Morrey BF, Tanaka S, An KN: Valgus stability of the elbow. A definition of primary and secondary constraints. Clin Orthop Relat Res 265:187-195, 1991. Moseley HE, Overgaard B: The anterior capsular mechanism in recurrent anterior dislocation of the shoulder. J Bone Joint Surg 44B:913, 1962. Mow VC, et al: Material properties of the inferior glenohumeral ligament and the glenohumeral articular cartilage. In FA Matsen, FH Fu, RJ Hawkins, eds: The shoulder: a balance of mobility and stability. Rosemont, IL, 1993, American Academy of Orthopaedic Surgeons, pp. 29-67. O’Driscoll SW, Horii E, Morrey BF, Carmichael S: Anatomy of the ulnar part of the lateral collateral ligament of the elbow. Clin Anat 5:296, 1992. Ovesen J, Nielsen S: Posterior instability of the shoulder. Acta Orthop Scand 57(5):436-439, 1986. Palmerud G, Forsman M, Sporrong H, Herberts P, Kadefors R: Intramuscular pressure of the infra- and supraspinatus muscles in relation to hand load and arm posture. Eur J Appl Physiol 83:223-230, 2000. Patel PR, et al: Anatomy and biomechanics of the coracohumeral and superior glenohumeral ligaments. Trans Orthop Res Soc 21:702, 1996. Pope MH, Wilder DG: Biomechanics of the shoulder. In M Nordin, GBJ Andersson, MH Pope, eds: Musculoskeletal disorders in the workplace. St. Louis, 1997, Mosby-Year Book, pp. 352-358. Poppen NK, Walker PS: Forces at the glenohumeral joint in abduction. Clin Orthop Relat Res 135:165-170, 1978. Punnett L, Fine LJ, Keyserling WM, Herrin GD, Chaffin DB, et al: Shoulder disorders and postural stress in automobile assembly work. Scand J Work Environ Health 26(4):283-291, 2000. Regan WD, Korinek BS, Morrey BF, An KN: Biomechanical study of ligaments around the elbow joint. Clin Orthop Relat Res 271:170-179, 1991. Rockwood CA Jr, Green DP, eds: Fractures in adults, 2nd ed. Philadelphia, 1984, JB Lippincott. Saha AK: Dynamic stability of the glenohumeral joint. Acta Orthop Scand 42(6):491-505, 1971. Søjbjerg JO, Ovensen J, Gundorf CE: The stability of the elbow following excision of the radial head and transection of the annular ligament. An experimental study. Arch Orthop Trauma Surg 106(4):248-250, 1987. Sommerich CM, McGlothlin JD, Marras WS: Occupational risk factors associated with soft tissue disorders of the shoulder: a review of recent investigations in the literature. Ergonomics 36(6):697-717, 1993. Soslowsky L J, Flatow EL, Bigliani LU, Pawluk RJ, Ateshian GA, Mow VC: Quantitation of in situ contact areas at the glenohumeral joint: a biomechanical study. J Orthop Res 10:524-534, 1992. Soslowsky L J, Flatow EL, Bigliani LU, Mow VC: Articular geometry of the glenohumeral joint. Clin Orthop Relat Res 285:181-189, 1992. Soslowsky L J, Carpenter JE, De Bano CM, Banerji I, Moalli MR: Development and use of an animal model for investigations on rotator cuff disease. J Shoulder Elbow Surg 5(5):383-392, 1996. Soslowsky LJ, Malicky DM, Blasier RB: Active and passive factors in inferior glenohumeral stabilization: a biomechanical model. J Shoulder Elbow Surg 6(4):371-379, 1997. Soslowsky LJ, Thomopoulos S, Ton S, Flanagan CL, Keefer CC, Mastaw J, Carpenter JE: Neer Award 1999. Overuse activity injures the supraspinatus tendon in an animal model: a histologic and biomechanical study. J Shoulder Elbow Surg 9(2):79-84, 2000. Soslowsky L J, Thomopoulos S, Esmail A, Flanagan CL, Iannotti JP, Williamson JD, Carpenter JE: Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors. Ann Biomed Eng 30(8):1057-1063, 2002. Speer KP, et al: Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg 76A:1819-1826, 1994. Stormont TJ, An KN, Morrey BF, Chao EY: Elbow joint contact study: comparison of techniques. J Biomech 5:329-336, 1985. Turkel SJ, Panio MW, Marshall JL, Girgis FG: Stabilizing mechanisms preventing anterior dislocation of the glenohumeral joint. J Bone Joint Surg 63A:1208-1217, 1981. Uhthoff HK, Matsumoto F, Trudel G, Himori K: Early reattachment does not reverse atrophy and fat accumulation of the supraspinatus—an experimental study in rabbits. J Orthop Res 21:386-392, 2003. van der Helm FCT: A finite element musculoskeletal model of the shoulder mechanism. J Biomech 27(5):551-569, 1994. Warner JJ, Deng XH, Warren RF, Trozilli PA: Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint. Am J Sports Med 20(6): 675-685, 1992. Warner JP, Bowen MK, Deng XH, Hannafin JA, Arnoczky SP, Warren RF: Articular contact patterns of the normal glenohumeral joint. J Shoulder Elbow Surg 7(4): 381-388, 1998. Woo SLY, Akeson WH, Jemmott GF: Measurements of nonhomogeneous, directional mechanical properties of articular cartilage in tension. J Biomech 9(12):785-791, 1976.
CHAPTER
5c
Evaluation of the Shoulder and Elbow Derek Plausinis and Joseph D. Zuckerman
Coordinated movement of the shoulder and elbow is essential to position the hand in space. Symptoms related to the shoulder and elbow are often vague and clinically difficult to diagnose. Numerous associated musculoskeletal disorders such as tendinitis and nerve entrapment syndromes have been found to be related to repetitive and forceful use of the upper extremity in a wide variety of occupations.4 Because symptoms may overlap, it is important to distinguish referred pain from the cervical spine or adjacent joints from that arising locally. Sound knowledge of local anatomy and appreciation of the salient features of the history and physical examination are crucial to the formulation of an accurate diagnosis, treatment regimen, and plan for prevention, especially with regard to work-related injuries.
THE SHOULDER History Complaints related to the upper extremity must be approached in an organized methodical manner, with care taken to not focus too quickly on a specific complaint so as to avoid missing a more generalized or related condition. At the initial assessment, identification of personal and work-related risk factors is essential. The patient’s age, hand dominance, occupation, and chief complaint should begin every history because these are the major contributors to the establishment of an accurate diagnosis. Age and nature of the complaint can be very directive in identifying the underlying shoulder disorder. A 40-year-old carpenter’s complaint of pain in the overhead position, for example, indicates to the physician to evaluate further the possibility of impingement and rotator cuff pathology, as opposed to a 20-year-old gymnast’s complaint that the shoulder “slips out” in the abducted and externally rotated position, which suggests ligamentous instability. Symptoms of pain, instability, and loss of motion account for most complaints about the shoulder. Noting maneuvers that provoke pain, presence of night pain, radiation of symptoms, and neck and opposite shoulder pain can aid in differentiating between referred pain and local pathology. Bilateral shoulder pain that is worsened by hyperextension or rotation of the neck but not by glenohumeral motion is due most often to cervical spine pathology as opposed to an intrinsic shoulder disorder. The physician must also ask about the presence of any extremity weakness, radiating pain, or paraesthesia. The distribution of neurologic symptoms assists in differentiating cervical radiculopathy from myelopathy or brachial neuritis.
When occupational activity-related pain is the chief complaint, the usual questions as to the location, timing, and character of the pain need to be supplemented by a detailed work history. Exploration into the exact nature of the task and how often it is performed is necessary to further elucidate occupational risk factors that can predispose to or aggravate the current condition. How often and how quickly the task is carried out should be noted. Repetitive work, especially when combined with high force demands, has been associated with shoulder tendinitis.4 Other work-related risk factors include high force, awkward joint posture, direct pressure, vibration, and repetitive overhead activities.21 A history with documentation of prior claims, time off work, and litigation in process constitutes valuable information because secondary gain can play a significant role in the prognosis. Just as important as the task itself is the mechanical and psychologic environment in which it is performed. In addition to the degree of stress involved, the presence of a draft, the need to work at a height, the positioning of equipment/tools, and the use of gloves may all play a role in the multifactorial etiology of repetitive strain disorders. Consideration of how the present condition affects recreation and activities of daily living also assists in determining the severity of the problem. Localized pain that is intense enough to disrupt sleep and cause limitation of simple overhead activities is most commonly due to rotator cuff pathology. Infection, arthritis, and frozen shoulder syndrome, however, can less frequently be manifested in a similar manner. Pain on carrying heavy packages at the side or when pushing a revolving door open may be more indicative of instability of the glenohumeral joint. Patients should be questioned with respect to previous injuries and any preexisting conditions that may have predisposed them to the current problem. If an acute injury is reported, details of its mechanism and the position of the extremity at the time force was applied should be ascertained. In the case of a fall, the height, the type of surface onto which the patient fell, and the body part that struck first should be recorded. Feelings of subluxation or crepitus at the time of injury with an inability to continue working secondary to immediate pain attest to the severity. In addition, symptoms of numbness or paraesthesia may accompany episodes of instability. The mechanism of anterior shoulder dislocation is usually the result of forced abduction and external rotation of the shoulder, whereas direct trauma is more likely to cause contusions or fractures. A fall onto or direct blow to the top of the shoulder often results in varying degrees of acromioclavicular injury, whereas falls onto the outstretched hand can easily result in proximal humeral fractures. For any injury or joint disorder, treatments undertaken to date must be ascertained. These include previous physician consults, medications, physiotherapy, splints, or joint injections. In the shoulder, multiple steroid injections in the subacromial space may lead to rotator cuff degeneration and tearing.26 Finally, a careful past medical history and functional assessment must be obtained. Multiple joint pains may suggest rheumatologic disease or referred pain.
Physical examination Even with the most thorough history, the physician may or may not have a clear sense of the underlying problem. A systematic
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Table 5c.1 Summary approach to shoulder physical examination Cervical spine examination Neurovascular assessment Shoulder examination Inspection Palpation Active and passive range of motion Special tests Impingement Hawkins test Neer’s test Painful arc Rotator cuff muscles Supraspinatus Infraspinatus and teres minor Subscapularis Biceps tendon Check for rupture Speed’s test Yergason’s test Stability tests Anterior Posterior Inferior and generalized laxity AC joint assessment Local tenderness Cross-body adduction Injection tests AC joint Subacromial space Glenohumeral joint
Figure 5c.1 Severe axillary nerve palsy manifested as deltoid atrophy, squaring off of the shoulder, and inferior subluxation of the humeral head.
rotator cuff tears, this may be related also to supraspinatus nerve entrapment neuropathy or C5 nerve root pathology. Prominence of the clavicle may suggest clavicle fracture or malunion as well as acromioclavicular joint dislocations (Fig. 5c.3). Swelling is unusual but may be seen in cases of subacromial bursitis or extravasation of synovial fluid in massive rotator cuff tears. Posterior dimpling or a “sulcus” may suggest anterior shoulder dislocation.
AC, acromioclavicular. Note: see text for detailed description of examination maneuvers.
meticulous approach to the physical examination is therefore required to avoid missing subtle findings and arriving at a diagnosis that is inaccurate or incomplete. A summary of the key elements of the shoulder physical examination is provided in Table 5c.1. Note that evaluation of all potential shoulder problems must include a thorough examination of the cervical spine. Inspection occurs with the patient sitting or standing and appropriately gowned to expose the shoulder entirely. The shoulder should be examined for signs of asymmetry caused by muscle wasting, soft tissue swelling, or bone or articular incongruities and a comparison made with the unaffected side. Muscle spasm involving the trapezius or paracervical muscles may cause asymmetry and may be related to cervical root pathology,8 whereas muscle fatigue may affect shoulder posture and kinematics.9 Deltoid atrophy may be associated with general disuse of the shoulder or related to axillary nerve pathology; best noted from an anterior vantage point, it is characterized by squaring off of the involved shoulder (Fig. 5c.1). Atrophy of the supraspinatus or infraspinatus muscles is best visualized from behind (Fig. 5c.2). Most commonly seen in association with
Figure 5c.2 Supraspinatus and infraspinatus atrophy noted from behind; the atrophy was secondary to a long-standing rotator cuff tear.
Chapter 5c
Figure 5c.3 Acromioclavicular separation with complete loss of articulation of the joint surfaces and prominence of the distal end of the clavicle.
The next step in a comprehensive examination of the shoulder is palpation of the bony and soft tissue elements. Tenderness or crepitus about the clavicle suggests fracture or nonunion, particularly if consistent with details of the history. Acromioclavicular joint tenderness is found in cases of arthritis and may be seen in those whose occupations require carrying heavy loads on their shoulders like lumber or postal bags21 or in the presence of instability secondary to traumatic ligamentous disruption. Tenderness on palpation over various anatomic landmarks can provide important clues leading to a diagnosis: Tenderness of the anterior of the acromion may be a subtle indicator of rotator cuff impingement; tenderness about the greater tuberosity may be seen in cases of rotator cuff tears, supraspinatus tendinitis, or fracture; tenderness over the bicipital groove, which is found between the greater and lesser tuberosities, is suggestive of bicipital tendinitis; and tenderness over the posterior joint line beneath the posterior of the acromion may represent glenohumeral arthritis. Anterior joint or capsular tenderness is more representative of soft tissue injury after anterior shoulder dislocation or subluxation.8 A nonspecific indicator of inflammation, local warmth is seen in conditions such as inflammatory arthritides or infection. Anesthesia or hypoesthesia in the dermatome overlying the middle deltoid suggests injury to the axillary nerve from traction, compression, or demyelination. Both active and passive joint motion must be assessed. It is important to understand the two basic components of shoulder elevation: glenohumeral and scapulothoracic. In the first 30 degrees of elevation in the scapular plane, motion occurs mostly at the glenohumeral joint. As the arm is elevated further, more scapulothoracic motion occurs with an equal contribution of glenohumeral and scapulothoracic movement in the last 60 degrees of elevation. In elevation there is a 2:1 ratio of glenohumeral to scapulothoracic motion overall.12 To assess the relative contributions of each, the scapula should be stabilized by holding the inferior scapular angle. Adhesions or rotator cuff derangement likely alters the normal fluid pattern of glenohumeral motion, and a greater proportion of the arc of motion becomes scapulothoracic.
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The American Shoulder and Elbow Surgeons has recommended that four planes of shoulder motion be assessed in all patients: total forward elevation, external rotation with the elbow at the side, external rotation with the arm abducted 90 degrees, and internal rotation behind the back.22 Active and passive motion for both shoulders should be recorded. Abduction and internal rotation are best examined with the patient sitting upright on the examination table. Forward elevation and external rotation can most accurately be examined with the patient both upright and supine to ensure that compensatory movements of the spine are eliminated. A limited active arc of motion may have a musculotendinous or neurologic etiology, or it may be related to pain. Limited passive motion suggests a mechanical block as in adhesive capsulitis, malunion of fractures, loose bodies, or glenohumeral arthritis. When assessing forward elevation, the practitioner should view the patient from a lateral position and reference the angle of the arm with the posterior thorax. External rotation, both active and passive, is best assessed with the arm at the side and the elbow flexed 90 degrees (Fig. 5c.4). A deficiency in active external rotation generally indicates neurologic or rotator cuff derangement, whereas one in both active and passive external rotation may be seen in adhesive capsulitis or in patients with mechanical blocks such as locked posterior dislocations. Testing external rotation with the arm abducted 90 degrees may be helpful, particularly in patients performing repetitive overhead activities such as throwing or welding. In this position, symptoms suggestive of capsulolabral deficiencies, greater tuberosity pathology, and instability may be elicited. Internal rotation is generally tested with the patient sitting upright. The patient is asked to reach around the back while internally rotating (and slightly extending) the shoulder so as to record the level reached by the outstretched thumb. This is commonly documented as the buttock, sacrum, iliac crest, and exact lumbar or thoracic spinous process reached. Generally, active and passive range of motion in this plane is similar, with limitations again suggestive of subacromial pathology such as rotator cuff derangement or a frozen shoulder.
Figure 5c.4 External rotation of the glenohumeral joint is assessed with the patient supine to prevent torso rotation. The elbow is flexed to 90 degrees with the arm at the side.
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Table 5c.2
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Evaluation of the shoulder and elbow
Muscle grading
Muscle gradations
Description
5 (normal) 4 (good) 3 (fair) 2 (poor) 1 (trace) 0 (absent)
Complete ROM against gravity with full resistance Complete ROM against gravity with some resistance Complete ROM against gravity Complete ROM with gravity eliminated Evidence of muscle contraction; no joint motion No contractility
ROM, range of motion.
Muscle strength testing is essential to assess the competence of the musculotendinous complexes about the shoulder and to identify possible peripheral or central neuropathology such as peripheral compressive neuropathy or cervical stenosis. In this regard, a thorough understanding of the structure of the brachial plexus and innervation patterns more peripherally is critical. Clearly, a suggestion of cervical pathology stimulates a more thorough neurologic examination. Muscle strength should be recorded using the universal system of grading on a scale from 0 to 5, with the opposite and presumably normal limb used as the control for comparison (Table 5c.2). It is important to realize that in the presence of pain, the accuracy of motor strength recording may be called into question. The primary motor functions—forward flexion, abduction, and external and internal rotation—are tested by resisting the particular plane of motion. Forward flexion is primarily the role of the anterior head of the deltoid muscle (axillary nerve, C5-C6) with secondary flexors, including the biceps and coracobrachialis muscles (musculocutaneous nerve, C5-C7), and the clavicular portion of the pectoralis major muscle (lateral pectoral nerve, C5-C6). Abduction tests the strength of both the middle third of the deltoid muscle (axillary nerve, C5-C6) and the supraspinatus muscle (suprascapular nerve, C5). Finally, the presence of scapular winging should be noted, indicating dysfunction of the serratus anterior (long thoracic nerve, C5-C7) or the trapezius (spinal accessory nerve). Scapular winging may be demonstrated by inspecting from behind while asking the patient to push against a wall. For assessing the rotator cuff, the key clinical features are muscle strength and pain. Whereas weakness alone may suggest a compressive neuropathy, that accompanied by pain suggests rotator cuff pathology. Before formal cuff muscle testing, the presence of any muscular atrophy is first noted (Fig. 5c.1). The greater tuberosity is palpated for tenderness or defect at the site of insertion of the supraspinatus, and the shoulder is passively flexed and extended while palpating for subacromial crepitus. The strength of the supraspinatus muscle may be isolated by elevating the arm 90 degrees, maximally pronating the forearm with the thumb down, and applying a downward force on the patient’s arm.24 The supraspinatus is affected in most rotator cuff tears, and when extension into the infraspinatus tendon occurs, external rotation may be weak or painful. External rotation strength with the elbow at the side assesses principally the infraspinatus muscle (suprascapular nerve, C5-C6) and teres minor muscle (axillary nerve, C5-C6). Large rotator
Figure 5c.5 To test for teres minor involvement in rotator cuff disorders, support the patient’s arm at 90 degrees of elevation in the scapular plane and ask the patient to externally rotate against resistance. The inability to externally rotate the arm indicates a positive “horn blower’s” sign.
cuff tears often produce a discrepancy between active and passive motion. The “dropping sign” is demonstrated by grasping the forearm with the elbow flexed and held at the side and passively externally rotating the shoulder 45 degrees. The patient is asked to resist a force in external rotation as the forearm is released. If the patient is unable to hold the arm in this position and the forearm drops to a neutral position, then the “dropping sign” is positive for infraspinatus weakness.9 Further extension of a rotator cuff tear into the teres minor can be suggested by external rotation weakness in abduction. This is tested by supporting the patient’s arm at 90 degrees of elevation in the scapular plane and then asking the patient to externally rotate against resistance (Fig. 5c.5). If the patient cannot externally rotate, then a “hornblower’s” sign is present,27 indicating extension of a tear into the teres minor. This sign can be functionally illustrated by asking the patient to bring the hand to the mouth; patients with infraspinatus and teres minor cuff weakness will abduct the arm to accommodate for inability to externally rotate. The subscapularis cannot be isolated by testing internal rotation strength with the arm at the side but rather requires the “lift-off ” test,6 which involves asking the patient to place his or her hand behind the back at the lumbosacral junction and then lift the hand off. Inability to perform a lift-off suggests subscapularis rupture; many patients with shoulder stiffness, however, are unable to perform this maneuver. The examiner must pay attention to the elbow during the lift-off test, because patients with subscapularis deficiency may give the false impression of being able to lift off by extending the elbow. When patients have limited internal rotation and the ability to perform the lift-off test is compromised, the subscapularis may be tested with the “belly press,”5 which involves asking the patient to place his or her hand on the abdomen and then bring his or her elbow forward to the level of the hand. Patients with subscapularis insufficiency will keep their elbow at the side with the wrist flexed and will be unable to effectively bring the elbow forward.
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Figure 5c.6 Positive impingement sign as described by Neer with forced forward elevation of the arm, causing the supraspinatus to impinge on the undersurface of the acromion.
Several provocative tests can be used to elucidate subacromial impingement, of which two have been classically used. The Neer “impingement sign” consists of forced forward elevation of the arm.13 Pain is elicited as the inflamed supraspinatus tendon impinges against the inferior border of the acromion anterior (Fig. 5c.6). If local anesthetic is administered to the subacromial space, pain in impingement syndrome is eliminated, which then confirms a positive impingement test.13 The impingement sign becomes much less reliable, however, when there is a limitation of passive forward elevation. In the Hawkins impingement test, the arm is forward-flexed 90 degrees and then forcibly internally rotated. Pain is evoked as the inflamed supraspinatus tendon is impinged against the coracoacromial ligament. In addition to these impingement tests, patients with impingement often demonstrate a “painful arc.” As the arm is abducted in the coronal plane, pain occurs between 60 and 100 degrees and is usually maximal at 90 degrees. Patients may be observed to rotate the humerus externally in the abducted position to minimize impingement of the greater tuberosity under the acromion. Assessment of the acromioclavicular joint begins with examination for local tenderness and swelling. A provocative maneuver for acromioclavicular joint pathology, cross-body adduction, can be elicited by passively elevating the arm to 90 degrees and adducting the arm and forearm across the chest. Pain near the acromioclavicular joint with cross-body adduction indicates acromioclavicular joint pathology,3 whereas that in the posterior shoulder usually results from posterior capsular tightness. In patients with documented or suspected glenohumeral instability, anterior instability is the most common clinical presentation. The simplest clinical maneuver, the “apprehension test,” is performed with the patient in the supine position with the arm abducted 90 degrees. The shoulder is externally rotated as the patient’s facial expression is noted. A patient’s apprehension or sense of impending shoulder subluxation or dislocation indicates a positive test. The “relocation” test can then be performed with the shoulder at the point of apprehension.
Figure 5c.7 Anterior instability is tested by placing the shoulder in 90 degrees of abduction and external rotation while attempting to level the humeral head out anteriorly with gentle posterior pressure. Apprehension and pain are indicative of positive responses.
A posteriorly directed force is applied to the proximal humerus, and in cases of instability pain or apprehension is relieved, indicating a positive “relocation” test.25 A similar but more provocative test for anterior instability is to abduct and externally rotate the shoulder in the upright position. When an anteriorly directed force is applied to the posterior proximal humerus, the patient with anterior instability becomes apprehensive or experiences pain in the shoulder (Fig. 5c.7). Although less common, posterior instability may be seen after a traumatic event or in association with a history of seizure disorder or alcohol abuse. A “posterior apprehension test” may be performed by flexing and internally rotating the shoulder and noting if the patient experiences a sense of instability. To further assess posterior laxity, an axial load can be applied to the elbow with the shoulder flexed 90 degrees and in neutral rotation. This maneuver subluxes the humeral head posteriorly. The examiner then abducts the arm and palpates for the sudden reduction of the subluxed shoulder.8 Anterior and posterior capsular laxity may be examined further by assessing the amount of glenohumeral translation. This may
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be difficult to produce on examination without the benefit of anesthesia but should be assessed in all patients. Humeral head translations may be tested with the patient sitting upright or lying supine while the scapula is stabilized with one hand and the humeral head grasped with the other. Anterior and posterior translatory loads are applied to evaluate anterior and posterior instability, respectively. The humeral head normally translates posteriorly up to 50% of the width of the glenoid, but the shoulder does not appreciably translate anteriorly. It is important to compare these findings with those in the opposite shoulder because some degree of laxity may be expected even in normal shoulders. Patients with inferior instability may have their symptoms reproduced by applying longitudinal downward traction on the arm. When the deltoid muscle is relaxed, an inferior “sulcus sign” is usually present in affected patients (Fig. 5c.8). Patients with inferior instability commonly also have anterior and posterior instability, in which case the term multidirectional instability is used. This condition is usually associated with generalized hyperlaxity as evidenced by hyperextension of the elbows and knees or the ability for the patient to bring the thumb passively to touch the ipsilateral forearm.
The long head of the biceps is first assessed by examining for continuity of the tendon. The patient is asked to resist gentle flexion of the elbow, and the upper arm is inspected. An abrupt change in contour of the biceps muscle proximally that is asymmetric with the contralateral side, referred to as a “Popeye” muscle, indicates rupture of the long head of the biceps. With an intact biceps tendon, tenderness in the bicipital groove is a common finding in bicipital tendinitis. As the humerus is externally rotated, the anterior pain of bicipital tendonitis typically moves more laterally with the externally rotated bicipital groove. Common provocative maneuvers for long head of biceps pain include Yergason’s test and Speed’s test. Yergason’s test consists of actively supinating the forearm against examiner resistance with the elbow flexed 90 degrees. Speed’s test involves forward elevation of the arm against resistance with the elbow extended and the forearm supinated. If positive, both tests elicit pain in the region of the bicipital groove. It should be noted that this diagnosis is often a component of the impingement syndrome, and controversy exists as to whether it exists as an isolated entity. In addition to the detailed neurologic examination outlined earlier, a careful vascular examination should be performed to rule out vascular compression in the neck as the source of claudicant shoulder pain, the so-called thoracic outlet syndrome. Distal pulses should routinely be palpated. Several tests have a time-honored role in the diagnosis of vascular insufficiency, perhaps the most commonly used of which is Adson’s maneuver or one of its several modifications. The examiner palpates the radial pulse and abducts the ipsilateral arm 90 degrees while extending and externally rotating the shoulder with the patient turning the head to the opposite side. A diminishing peripheral pulse signifies proximal compression and indicates a positive test. It is critical to identify the source of vascular compression, including an accessory rib, Pancoast’s tumor, fibrous bands, or clavicular malunion, so that proper steps in management may be taken.
Diagnostic testing
Figure 5c.8 Inferior ligamentous laxity exhibited by an inferiorly subluxed humeral head with downward traction on the humerus with the arm at the side.
The practitioner generally establishes the diagnosis after a thorough history and comprehensive physical examination. Most imaging tests are performed to confirm the physician’s clinical impression, but inevitably in some cases the diagnosis remains unclear and further investigation is warranted. The mainstay of imaging remains the standard radiograph. In general, all patients with complaints referable to the shoulder should receive a routine series of at least three radiographs as initial screening. This consists of anteroposterior (AP), scapular lateral, and axillary radiographs of the shoulder with the beam centered over the glenohumeral joint. When shooting these radiographs it is important to follow meticulous guidelines and to keep in mind that the plane of the scapula is rotated anteriorly approximately 35 to 40 degrees (Fig. 5c.9). A true AP radiograph in the scapular plane is taken with the posterior aspect of the affected shoulder against the cassette and the opposite shoulder rotated anteriorly approximately 40 degrees. The AP radiograph in internal rotation shows the greater tuberosity en face, external rotation shows it in profile, and both show
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Technique for obtaining scapular anteroposterior (A), lateral (B), and axillary (C) views of a trauma series required on all patients.
different aspects of the humeral head. In these views the distance between the humeral head and the acromion process should be assessed. In cases of massive rotator cuff tears, the normal interspace, averaging 10 mm, may diminish as the humeral head migrates cephalad, and a break in the inferior calcar line may be seen (Fig. 5c.10).7 Also considered routine in trauma situations is the scapular lateral view, in which the scapula is seen tangentially. This is an anterior oblique projection taken with the patient rotating the involved shoulder 60 degrees toward the central beam.7 Its value lies in identifying shoulder dislocations and fractures of the humeral head or neck or scapula. In the axillary view, the patient is positioned supine with the arm abducted. A horizontal x-ray beam is directed in toward the axilla. This projection visualizes the relationship between the humeral head, glenoid, coracoid, and acromion (Fig. 5c.11). It is a
key projection for identifying shoulder dislocations and any associated anterior glenoid avulsion fractures (bony Bankart lesion) or posterior impression fractures of the humeral head (Hill-Sachs lesion) (Fig. 5c.12). The relative position of the anterior aspect of the acromion with respect to the clavicle should be assessed, particularly in cases of impingement syndrome. Anterior projection of the acromion beyond the anterior limits of the clavicle has been shown to predispose to rotator cuff problems.28 The “outlet view” represents a lateral projection into the subacromial space. It is an ideal projection for assessing the slope of the acromion, which has been shown to have an impact on the development of impingement syndrome (Fig. 5c.13). It is taken with the patient standing and the affected shoulder rotated 60 degrees toward an x-ray beam angled 10 to 15 degrees caudad.7
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Figure 5c.12 Locked posterior dislocation with a humeral head impression fracture. Figure 5c.10 In the presence of massive rotator cuff tears, a highriding humeral head is noted with decreased acromiohumeral distance and a break in the inferior calcar margin.
A specialized AP radiograph angled 15 degrees cephalad is a valuable tool for imaging the distal and middle aspects of the clavicle and acromioclavicular joint. As such, this projection is used to assess clavicle fractures, acromioclavicular joint sprains, arthritis, or spurring (a source of rotator cuff impingement), or distal clavicle osteolysis (common in weight lifters). Magnetic resonance imaging (MRI) has become the imaging modality of choice in most centers for identifying most soft
tissue pathology about the shoulder. Multiaxial images and the development of newer MRI protocols have enabled more accurate assessments of shoulder pathology. For rotator cuff pathology and impingement syndrome, MRI can identify rotator cuff tendinosis and partial and full thickness tears (Fig. 5c.14).1 An estimate of rotator cuff tear size can be made, and the presence of fatty degeneration of the rotator cuff muscles can be identified. In cases of impingement, MRI can also identify potential sources of cuff impingement such as an osteophyte
C
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Figure 5c.11 Axillary view of the shoulder, crucial for determining the position of the humeral head in relation to the glenoid. The labeled structures are the humeral head (H), glenoid (G), coracoid (C), acromion (A), and acromioclavicular joint (AC).
Figure 5c.13 Supraspinatus outlet view with a large subacromial spur, causing impingement.
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AC A RT
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Figure 5c.15 Arthrogram documenting a full-thickness rotator cuff tear with dye extravasation into the subacromial space and laterally to the greater tuberosity.
Figure 5c.14 Magnetic resonance image of the right shoulder revealing a full-thickness rotator cuff tear (RT) with a retracted supraspinatus tendon (SS) underneath the acromion (A) and acromioclavicular joint (AC). The greater tuberosity (GT) is also shown.
from the undersurface of the acromioclavicular joint, acromioclavicular joint hypertrophy, or a downward-beaking acromion that may be associated with a subacromial spur. In cases of instability when the diagnosis is unclear, MRI can be used to detect capsular injury or redundancy as well as labral tears. Although infrequent, in cases of violent traumatic anterior shoulder dislocations, the subscapularis tendon may be torn either directly off its insertion on the lesser tuberosity or in its mid-substance. In the latter case, MRI potentially shows retraction at the site of the tear, or in chronic cases calcific deposits may be seen in the substance of the subscapularis muscle or tendon. The tendon of the long head of the biceps can be imaged on axial cuts as it sits in the bicipital groove. Absence of the tendon in this landmark would imply rupture and subsequent retraction (which should be obvious on clinical examination) or subluxation, as may be seen in a congenitally shallow bicipital groove or after trauma. Bicipital tendinitis is often a more proximal phenomenon and is difficult to image by MRI. Finally, MRI has a role in the diagnosis of osteonecrosis of the humeral head and should be considered in certain high-risk conditions such as sickle cell disease, steroid use, or alcohol abuse or in deep sea divers in the setting of shoulder pain even without radiographic findings. Historically regarded as unreliable, ultrasonography has played an increasing role in rotator cuff diagnoses in recent years. With newer equipment and experienced ultrasonographers, sensitivities and specificities of 94% or greater for the detection of fullthickness tears and 93% or greater for partial-thickness tears have been reported.23 Although it has a lower cost than MRI and is a noninvasive test, the availability of accurate rotator cuff assessment is limited by the availability of an experienced musculoskeletal ultrasonographer.
Although it has largely been replaced by MRI and ultrasound, arthrography continues to have a role in the diagnosis of shoulder disorders. It entails injection of either contrast alone or contrast followed by the injection of room air into the glenohumeral joint. Various x-ray views are then taken to assess different shoulder components. The technique has a time-honored role in the diagnosis of complete rotator cuff tears (Fig. 5c.15). The arthrogram may be used also to visualize the long head of the biceps tendon, thereby diagnosing rupture, tenosynovitis, or subluxation. Computed tomography (CT) is used primarily to assess bony pathology further when details are unclear from plain radiographs, as may be seen in cases of recurrent instability with glenoid or humeral head defects. Lidocaine injection tests serve a vital role with regard to problems of the shoulder in that they can be valuable diagnostic tools when the precise diagnosis is in question. For instance, at times it may be difficult to localize the source of symptoms to the acromioclavicular joint, the subacromial space, or the glenohumeral joint. In these situations, selective lidocaine injection can be of obvious benefit. The subacromial space is the most frequently injected region. Amelioration of symptoms points to rotator cuff tendinitis or tear as the culprit; conversely, if symptoms persist, the source of pain is elsewhere, although the subacromial space may be responsible at least in part. Various techniques for injection have been described; nevertheless, it is always important to follow strict sterile technique to minimize the risk of infection. The subacromial space can be injected from a lateral approach with relative ease (Fig. 5c.16). Downward traction may be applied to the arm to help widen the interval between the humeral head and the acromion. Also a frequent source of pain, the acromioclavicular joint is easily palpated between the distal clavicle and the acromion, with a needle directed from its superior aspect. Often, pathology in this joint is associated with impingement of the rotator cuff, and selective injection here may help clarify the severity of the referred pain.
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Figure 5c.16 Subacromial lidocaine injection test via a lateral approach is extremely valuable in the diagnosis of impingement.
Technetium bone scanning has a limited role in the evaluation of problems related to the shoulder. However, it may be of use in the evaluation of adhesive capsulitis or in ruling out occult infection, tumor, or avascularity in the presence of persistent symptomatology. Electromyographic and other nerve conduction studies have a definite role in distinguishing central from peripheral neuropathy and in investigating the possibility of a neural basis of muscle wasting or weakness when intrinsic myotendinous pathology is ruled out. In suggestive cases, shoulder evaluation may include laboratory studies, particularly routine blood tests such as a complete blood count, erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, antinuclear antibody, and blood chemistry analysis, to exclude inflammatory arthritides or infection. Additionally, adhesive capsulitis is more likely in diabetic patients, hence the importance of assessing serum glucose levels. If joint sepsis or crystal diseases are suspected, the glenohumeral joint can be aspirated and fluid sent for Gram stain, culture, cell count, and microscopy for crystals.
THE ELBOW History The approach to the history for the patient with an occupational elbow disorder follows an outline similar to that for a shoulder disorder. The general content for history of present illness and occupational history are as outlined previously. Specific complaints arising from elbow pathology with clinical examples are provided below. Symptoms related to the elbow usually involve pain or stiffness. Whereas pain is a common complaint with advanced elbow arthritis, the early phases of degenerative joint disease in the elbow usually present with loss of motion as the primary concern. After any trauma to the elbow, stiffness is also a common complaint, particularly with a history of prolonged
Figure 5c.17 olecranon.
Lateral view demonstrating a spur off the tip of the
immobilization after injury. Elbow stiffness may or may not be associated with pain, and it is important to delineate whether the patient’s primary concern and source of functional impairment is pain or stiffness. Degenerative joint disease ultimately results in activity-related pain, usually first occurring near full extension. Osteoarthritis may present also with a history of episodic sharp pain in the elbow and intermittent loss of motion or locking. These mechanical symptoms commonly arise also after a traumatic event to the elbow and suggest the presence of loose bodies that usually require surgical removal. Patients may notice swelling about the elbow joint. A joint effusion or synovitis is present with some diffuse swelling about the elbow and is often more apparent clinically in the posterolateral aspect. In contrast, olecranon bursitis may present with a recurrent mass directly over the olecranon. Bone spurs off the olecranon (Fig. 5c.17) have been associated with olecranon bursitis (Fig. 5c.18), and the patient may have noticed the development of a more prominent olecranon. Olecranon bursitis may be sterile or septic, and the patient should be questioned as to a history of fever, erythema, previous attempts at aspiration, and drainage. Unlike the shoulder, recurrent instability is an uncommon problem in the elbow. Stiffness is the usual problem after elbow dislocation. When present, instability may present as recurrent episodes of dislocation or more commonly as a sense of elbow subluxation and pain. In cases of recurrent instability after elbow trauma, symptoms are most likely to occur from lateral ligament deficiency and are provoked by activities where a valgus stress is applied to the elbow with the forearm in supination. The valgus instability from medial collateral ligament laxity is typically seen in throwing athletes and very uncommonly as a result of workplace injury.
Chapter 5c
Figure 5c.18 Classic appearance of olecranon bursitis. Note the prominent fluid-filled bursa over the olecranon (compared with a normal elbow in Fig. 5c.19).
Tendinopathy about the elbow is a common problem, usually presenting as medial or lateral epicondylitis. Patients typically complain of pain in the region of the flexor or extensor origin that is aggravated with repetitive active wrist movement. Chronic tendinitis of the distal biceps tendon is uncommon; however, ruptures may occur after resisted activity, typically in the dominant arms of men in their forties. Entrapment neuropathies about the elbow must be considered also as a possible source of elbow pain and may present with weakness or sensory changes in the hand and wrist as well. Lying posterior to the medial epicondyle, the ulnar nerve is prone to compression and irritation with activities requiring recurrent elbow flexion or from direct compression over the nerve. In cases of cubital tunnel syndrome (ulnar nerve entrapment at the elbow), patients typically complain of sensory changes in the ring and small fingers. The ulnar nerve lies close to the ulnohumeral joint and in cases of arthritis can be prone to irritation from osteophytes and loose bodies.17 Median and radial nerve compression at the elbow level may occur also, although less frequently than ulnar nerve entrapment. Patients typically present with elbow pain, and neurologic symptoms are less common.19,20 When considering the diagnosis of peripheral nerve entrapment, the distribution of symptoms and the exacerbating features are critical to help determine whether the symptoms are truly originating at the elbow level or whether referred pain from the shoulder or a cervical radiculopathy may be the underlying cause.
The elbow
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Inspection of the elbow is first undertaken to look for any signs of inflammation or previous injury. To identify subtle findings, comparison with the unaffected side is helpful. An elbow effusion may be clinically apparent by a fullness in the posterolateral aspect, whereas olecranon bursitis presents with a local mass over the olecranon (Fig. 5c.18). With the elbow in full extension and the forearm in supination, the alignment of the ulna compared with humerus (carrying angle) is estimated. Despite considerable variation among individuals, normal values for the carrying angle are approximately 10 degrees for men and 13 degrees for women.19 Childhood injuries to the elbow commonly result in alteration of the carrying angle into either valgus or varus malalignment. Although excess valgus alignment may lead to ulnar nerve irritation,17 varus malalignment, also termed a gunstock deformity, is usually not associated with any functional deficits. Palpation of the elbow relies first on establishing the appropriate surface anatomy. On the lateral aspect, three important bony landmarks appear: lateral epicondyle, radial head, and tip of the olecranon (Fig. 5c.19). The radial head is a bony prominence just distal and slightly inferior to the lateral epicondyle. The location of the radial head is confirmed by rotating the forearm with the elbow held at 90 degrees of flexion; the rotation of the radial head on the stationary capitellum is palpable. At the center of these three bony landmarks (Fig. 5c.19), fullness indicates synovitis or effusion and represents also a safe location for elbow joint aspiration or injection. The radiocapitellar joint may be palpated between the radial head and the lateral epicondyles. While palpating over this region, passive forearm rotation and passive flexion and extension allow for an assessment of any crepitus or soft tissue snapping from the radiocapitellar joint. On the medial side of the elbow, the medial epicondyle and the olecranon may be identified. In the groove posterior to the medial epicondyle lies the ulnar nerve, which may be gently palpated. Medial to the ulnar nerve is the medial aspect of the ulnohumeral joint. Placing the examining index finger and thumb on either side of the ulna just distal to the olecranon while the elbow is gently flexed and extended allows for the assessment of ulnohumeral joint crepitus and tenderness.
Physical examination As in the case of shoulder examination, a thorough elbow examination begins with an evaluation of the cervical spine. Shoulder and wrist examination must be performed also to rule out a referred etiology for the current complaint. In addition, the complete upper extremity examination will reveal any other disabilities from joints above or below the elbow that may contribute to the patient’s functional deficit.
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Figure 5c.19 Lateral side of elbow illustrating the palpable bony landmarks: lateral epicondyles (E), radial head (R), and olecranon (O).
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Tendons about the elbow are then systematically palpated. Each tendon should be palpated for continuity on active contraction of the corresponding muscle group. The presence of local tenderness, pain with resisted activity, and pain with passive stretch of a tendon suggests tendinopathy. For example, the common extensor origin is just distal to the lateral epicondyle. Local tenderness, pain with resisted active wrist extension, and pain with passive wrist flexion all suggest a diagnosis of lateral epicondylitis (tennis elbow). Similarly, pain over the common flexor-pronator origin just distal to the medial epicondyle along with pain with resisted active wrist flexion and passive wrist extension suggest medial epicondylitis (golfer’s elbow). After examining the common flexor and extensor origins, the triceps tendon is examined. The triceps tendon inserts into the olecranon, and palpation may reveal a prominent traction spur (Fig. 5c.17). The distal biceps tendon can then be identified in the middle of the antecubital fossa just lateral to the brachial artery. The biceps assists in elbow flexion and is also the primary muscle responsible for forearm supination. A ruptured distal biceps tendon (reverse Popeye sign) can be identified by having the patient perform resisted supination with the elbow in a flexed position and noting a lack of palpable tendon in the cubital fossa. Another symptom is a prominent bulge of the distal aspect of the biceps muscle. The elbow is then taken through both active and passive movements so that range of motion can be documented. Any crepitus from the ulnohumeral or radiocapitellar joints is noted. In addition to flexion and extension, forearm rotation must also be documented. Limitation of motion or pain on forearm rotation mandates a detailed wrist examination to rule out any pathology at the distal radioulnar joint. Normal elbow range of motion is from full extension (0 degrees) to 145 degrees of flexion. Normal forearm rotation is from 75 degrees of pronation to 85 degrees of supination.2 For a patient to perform most activities of daily living, range of motion from 30 degrees to 130 degrees of flexion and forearm rotation from 50 degrees of pronation to 50 degrees of supination (i.e., 100 degrees of flexion-extension and a 100-degree arc of forearm rotation) is necessary.11 Stability testing of the elbow can be challenging, but in the setting of occupational disorders elbow instability is an infrequent finding. One of the challenges of instability testing is that valgus and varus stability tests require rotationally stabilizing the humerus. From full extension to 20 degrees of flexion the collateral ligaments cannot be isolated, because bony contributions to stability are provided by the seating of the olecranon in the olecranon fossa. Medial collateral ligament laxity has been shown to be greatest with the elbow in 20 degrees of flexion and the forearm pronated.16 To test the medial collateral ligament, the elbow is held flexed approximately 20 to 30 degrees with the forearm pronated and the arm maximally externally rotated as a valgus stress is applied. The presence of medial-sided pain and palpable medial joint line opening are signs of medial collateral pathology. Another test to stress the medial collateral ligaments is the “milking sign” performed by fully flexing the patient’s elbow and grasping the thumb to apply a valgus stress to the elbow. The test is positive if medial elbow pain is elicited. Varus stability is tested also with the elbow at 20 to 30 degrees of flexion but instead requires maximum internal rotation of the arm. The examiner can then stand behind the patient to apply
the varus stress and examine the lateral joint line. Recurrent instability occurs very infrequently after elbow dislocations, and the specific tests for the lateral ligament complex are well described.14 These tests are rarely important, however, in the setting of occupational elbow disorders. At elbow level the ulnar, radial, and median nerves may all be compressed. A detailed assessment of ulnar, radial, and median motor and sensory function, including inspection of the hand and forearm for muscle atrophy or fasciculations, should be performed. The ulnar nerve is palpated behind the medial epicondyle and once identified, the elbow can be brought from a position of extension to flexion to determine whether the ulnar nerve subluxes or dislocates anteriorly during flexion. Gently tapping over the nerve may produce paresthesia radiating into the small finger and ulnar half of the ring finger (Tinel’s sign at the cubital tunnel), indicating nerve irritation. A further sign of ulnar nerve compression at the elbow is to hold the joint in a flexed position for 1 minute and observe for the development of paresthesias or numbness in the ring and small fingers.17 Less commonly, the median and radial nerves may be compressed at elbow level.19,20 The median nerve runs adjacent to the brachial artery in the antecubital fossa and may be sensitive to pressure in the antecubital space or over the proximal portion of the pronator teres.20 Gentle tapping over the course of the median nerve may produce Tinel’s sign at the point of irritation. Compression in the antecubital space (at the lacertus fibrosis) is tested by actively supinating the forearm against resistance with the elbow flexed beyond 120 degrees. For evaluating median nerve compression at the pronator teres, resisted pronation is performed with the elbow in extension. Compression of the median nerve may occur also as it travels under the flexor digitorum superficialis as can be determined with resisted flexion of the long finger.20 For radial nerve entrapment, Tinel’s sign along its course may likewise be elicited. Perhaps the most important point of examining for radial nerve entrapment is the location of the pain. Pain emanating from radial compression is often associated with tenderness approximately 4 to 5 cm distal to the lateral epicondyle, whereas the pain of lateral epicondylitis is present adjacent to the lateral epicondyle.15
Diagnostic testing Routine diagnostic studies for elbow disorders begin with plain radiographs. A standard elbow series consists of an AP (Fig. 5c.20), a lateral (Fig. 5c.17), and an oblique film.18 With a history of trauma, it is particularly important to confirm that the radial head is in joint as evidenced by its lining up with the capitellum on all views. At the same time, any radial head deformity should be noted, as well as signs of radiocapitellar degenerative changes. A radial head view can be requested also if the radial head cannot be adequately assessed (Fig. 5c.21). The ulnohumeral joint can then be studied on the radiographs. In cases of degenerative joint disease, osteophyte formation medially or laterally off the ulnohumeral joint is a common finding on the AP view, and the lateral view may demonstrate osteophytes off the coronoid or tip of the olecranon. In cases where pathology about the olecranon is suspected or if loose bodies are a possibility, an
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Figure 5c.22 Axial view of elbow showing the olecranon (O), trochlea of the distal humerus (T), medial epicondyle (ME), and lateral epicondyle (LE).
Figure 5c.20
Standard anteroposterior radiograph of the elbow.
Figure 5c.21
Radial head view.
axial view of the flexed elbow can be helpful (Fig. 5c.22). For cases of suspected medial and lateral instability, stress views demonstrate abnormal joint widening. When in doubt, comparison views of the unaffected side can be obtained. A complete interpretation of standard radiographs should also include an assessment of soft tissue shadows for signs of swelling or effusion. Seen with cases of elbow effusion, a radiolucent area posterior to the olecranon fossa represents visualization of the posterior fat pad. Anteriorly, it is normal to see a thin concave radiolucent fat pad; however, a convex fat pad known as a “sail sign” indicates an elbow effusion. CT is often helpful in the setting of trauma to identify osseous loose bodies (Fig. 5c.23) or for cases where the osseous anatomy is unclear on standard radiographs.10 Offering the benefit of soft tissue assessment, MRI is ideal for evaluating cases of suspected cartilaginous loose bodies, assessment of tendons when the clinical examination is unclear, assessment of collateral ligaments, or evaluation of soft tissue masses.10,18 It is helpful also in cases of peripheral nerve compression by suspected soft tissue masses such as cysts within the cubital tunnel or synovitis extending into the radial tunnel. Proliferative synovial disorders presenting as an isolated synovitis of unknown etiology are also well suited to MRI evaluation. Although less commonly used in elbow disorders, ultrasound is useful to evaluate fluid collections around the joint and to assess the continuity of superficial muscle tendon units such as the triceps and biceps when the clinical examination is uncertain. It has been used also to investigate for intraarticular loose bodies10; however, because ultrasound requires an experienced ultrasonographer, it is less commonly used than CT or MRI in that setting. Electrodiagnostics can be particularly useful in the patient with neurologic symptoms or signs. Electromyography and nerve conduction studies are particularly useful to determine the presence, location, and extent of peripheral nerve compression
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should be carried out in suspected cases of infection or for isolated effusions of unknown etiology.
REFERENCES 1.
Figure 5c.23 Computed tomography showing a bony loose body in the olecranon fossa.
or to identify a brachial plexus lesion or cervical radiculopathy. Electrodiagnostic studies for cubital tunnel syndrome and posterior interosseous nerve compression syndrome often demonstrate electrophysiologic abnormalities and are helpful to confirm the diagnosis.15,17 In contrast, electrodiagnostic studies in cases of radial tunnel syndrome and pronator syndrome are usually normal.19,20 Diagnostic blocks about the elbow are much less common than for assessment of shoulder disorders but may on occasion be useful. Local anesthetic injection into the radial tunnel distal to the lateral epicondyles may help to distinguish cases of radial tunnel syndrome from lateral epicondylitis.15 Similarly, a local anesthetic block may be used at a potential site of median nerve compression at the elbow to determine whether it is responsible for the patient’s pain.20 Although less commonly used for elbow disorders, technetium bone scanning may be useful to identify biologically active areas of bone in cases of occult infection, tumor, or early degenerative disease. When considering a diagnosis of inflammatory disease or infection, routine blood tests such as a complete blood count, erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, and antinuclear antibodies may be useful. Joint aspiration
Bencardino JT, Garcia AI, Palmer WE: Magnetic resonance imaging of the shoulder: rotator cuff. Top Magn Reson Imag 14(1):51-67, 2003. 2. Boone DC, Azen SP: Normal range of motion of joints in male subjects. J Bone Joint Surg 61A:756-759, 1979. 3. Chen AL, Rokito AS, Zuckerman JD: The role of the acromioclavicular joint in impingement syndrome. Clin Sports Med 22:343-357, 2003. 4. Frost P, Bonde JP, Mikkelsen S, et al: Risk of shoulder tendinitis in relation to shoulder loads in monotonous repetitive work. Am J Indust Med 41(1):11-18, 2002. 5. Gerber C, Hersche O, Farron A: Isolated rupture of the subscapularis tendon. J Bone Joint Surg 78A:1015-1023, 1996. 6. Gerber C, Krushell RJ: Isolated rupture of the subscapularis tendon: clinical features in 16 cases. J Bone Joint Surg 73B:389-394, 1991. 7. Gold RH, Bassett LW: Disorders of the shoulder: plain radiographic diagnosis. In LL Seeger, ed: Diagnostic imaging of the shoulder. Baltimore, 1992, Williams & Wilkins. 8. Hawkins RJ, Bokor DJ: Clinical evaluation of shoulder problems. In CA Rockwood Jr, FA Matsen, eds: The shoulder, ed 2. Philadelphia, 1998, WB Saunders. 9. McQuade KJ, Dawson J, Smidt GL: Scapulothoracic muscle fatigue associated with alterations in scapulohumeral rhythm kinematics during maximum resistive shoulder elevation. J Orthop Sports Phys Ther 28(2):74-80, 1998. 10. Miller TT: Imaging of elbow disorders. Orthop Clin North Am 30(1):21-36, 1999. 11. Morrey BF, Askew LJ, An KN, Chao EY: A biomechanical study of normal functional elbow motion. J Bone Joint Surg 63A:872-877, 1981. 12. Morrey BF, Itoi E, An K: Biomechanics of the shoulder. In CA Rockwood Jr, FA Matsen, eds: The shoulder, ed 2. Philadelphia, 1998, WB Saunders. 13. Neer CS II: Impingement lesions. Clin Orthop Relat Res 173:70-77, 1983. 14. O’Driscoll SW: Classification and evaluation of recurrent instability of the elbow. Clin Orthop Relat Res 370:34-43, 2000. 15. Plate AM, Green SM: Compressive radial neuropathies. Instruct Course Lect 49:295-304, 2000. 16. Pomianowski S, O’Driscoll SW, Neale PG, Park MJ, Morrey BF, An KN: The effect of forearm rotation on laxity and stability of the elbow. Clin Biomech 16:401-407, 2001. 17. Posner MA: Compressive ulnar neuropathies at the elbow. I. Etiology and diagnosis. J Am Acad Orthop Surg 6(5):282-288, 1998. 18. Potter HG. Imaging of posttraumatic and soft tissue dysfunction of the elbow. Clin Orthop Relat Res 370:9-18, 2000. 19. Regan WD, Morrey BF: Physical examination of the elbow. In BF Morrey, ed: The elbow and its disorders. Philadelphia, 2000, WB Saunders. 20. Rehak DC: Pronator syndrome. Clin Sports Med 20(3):531-540, 2001. 21. Rempel DM, Harrison RJ, Barnhart S: Work-related cumulative trauma disorders of the upper extremity. JAMA 267:838-842, 1992. 22. Richards RR, Bigliani LU, Gartsman GM, Iannotti JP, Zuckerman JD: A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg 3:347-352, 1994. 23. Teefey SA, Middleton WD, Yamaguchi K: Shoulder sonography: state of the art. Radiol Clin North Am 37:767-785, 1999. 24. Tennent TD, Beach WR, Meyers JF: A review of the special tests associated with shoulder examination. Part I. The rotator cuff tests. Am J Sports Med 31(1): 154-160, 2003. 25. Tennent TD, Beach WR, Meyers JF: A review of the special tests associated with shoulder examination. Part II. Laxity, instability, and superior labral anterior and posterior (SLAP) lesions. Am J Sports Med 31(2):301-307, 2003. 26. Tillander B, Franzen LE, Karlsson MH, Norlin R: Effect of steroid injections on the rotator cuff: an experimental study in rats. J Shoulder Elbow Surg 8(3):271-274, 1999. 27. Walch G, Boulahia A, Calderone A, Robinson AHN: The “dropping” and “hornblower’s” signs in evaluation of rotator cuff tears. J Bone Joint Surg 80B(4):624, 1998. 28. Zuckerman JD, Kummer FJ, Cuomo F, Simon J, Rosenblum S: The influence of coracoacromial arch anatomy on rotator cuff tears. J Shoulder Elbow Surg 1:4-12, 1992.
CHAPTER
5d
Treatment of Shoulder Disorders Anthony M. Buoncristiani, Paul H. Marks, and Freddie H. Fu
Disorders of the shoulder girdle are very common and can limit participation in vocational, recreational, and professional activities. Developing an approach to the management of shoulder disorders relies on appropriate history taking, physical examination, and imaging. This chapter outlines the treatment of most common shoulder problems, including rotator cuff pathology; instability; fracture and dislocations of the sternoclavicular joint, clavicle, acromioclavicular joint, and proximal end of the humerus; frozen shoulder; and degenerative joint disease.
ROTATOR CUFF DISEASE IN THE SHOULDER In an older patient who complains of shoulder pain, the diagnosis of rotator cuff disease must be considered. This entity is very common and important. In 1934, Codman’s classic publication32 summarized 25 years of observations on the musculotendinous cuff and its components. Coleman also discussed ruptures of the supraspinatus tendon and performed the first repair of the cuff in 1909. Although there have been recent advances in diagnosis and imaging of the rotator cuff, current views and treatments are quite similar to concepts proposed 50 years ago.
Anatomy and function The components or musculotendinous units of the rotator cuff are known to function as dynamic stabilizers for the glenohumeral joint. Electromyographic and biomechanical studies have demonstrated the role of the rotator cuff in providing support of the capsule and preventing excessive anterior and posterior movement. Studies have suggested that the rotator cuff contributes between one third and one half of the power of the shoulder in abduction and at least 80% of the power in external rotation.30 The rotator cuff, which consists of the subscapularis, supraspinatus, infraspinatus, and teres minor, functions to approximate the humeral head to the glenoid cavity. The supraspinatus assists the deltoid in abduction, whereas the subscapularis, infraspinatus, and teres minor serve to depress the humeral head during elevation of the arm. Depression of the humeral head during elevation of the arm helps to avoid impingement. The infraspinatus and teres minor function to externally rotate the arm. These muscle actions may also reduce the strain on the inferior glenohumeral ligament with the arm abducted and essentially rotated.28 In this position, they serve to pull the humeral head posteriorly. The subscapularis internally rotates the arm. It serves
as an effective restraint to external rotation and anterior translation of the humeral head with the arm at the side of the body; however, it is ineffective in doing so with the arm abducted to 90 degrees.147 At 90 degrees of abduction, the subscapularis lies above the equator of the humeral head and cannot reinforce the anterior aspect of the shoulder. The vascular anatomy of the cuff tendons has been reported by many authors. Most have concluded that the supraspinatus has a “critical zone” that is prone to calcium deposits and potential rupture.103 Rathbun and MacNab122 found that filling of the cuff vessels was dependent on the position of the arm at the time of injection. They documented poor filling of the supraspinatus tendon near its attachment to the greater tuberosity and suggested that tendon failure may be caused by “constant pressure from the head of the humerus which tends to wring out blood supply to the tendon when the arm is held in the resting position of adduction and neutral rotation.”122 The long head of the biceps may be considered a part of the rotator cuff. It attaches to the supraglenoid tubercle of the scapula. This structure is positioned to function as a humeral head depressor. It also guides the humeral head as it is elevated.141 The concomitant tears that occur in the rotator cuff and biceps tendon attest to the close functional relationship between these two structures. Neer stated that “impingement of the rotator cuff beneath the coracoacromial arch has been recognized as one of the causes of chronic disability of the shoulder.” Anatomically, this problem occurs during elevation of the arm anterior to the scapular plane. He attributed pathologic changes of the rotator cuff to mechanical impingement and believed that most rotator cuff tears were due to attritional tears from a narrow supraspinatus outlet.24,106 Additionally, Neer discussed associated alterations on the undersurface of the anterior third of the acromion, the coracoacromial ligament, and in time the acromioclavicular joint. He described three different stages of impingement. Stage I usually occurs in patients less than 25 years old. Pathology is characterized by edema and hemorrhage. The clinical course is reversible and conservative treatment is suggested. Stage II is seen in the 25-year-old to 40-year-old age group. Pathology includes fibrosis and tendinitis. These patients have activity-related pain, and treatment may be surgical if there is no response to rehabilitation. Stage III disease typically occurs in patients greater than 40 years old. Pathology in this group includes acromioclavicular spurs and full-thickness cuff tears. These patients have progressive disability and are often candidates for acromioplasty and repair. Bigliani et al17 reported on a morphologic study in which the variation in shape of the acromion was correlated with tears of the rotator cuff. They described three types of acromion. Type I has a flat profile, type II has a smooth curve, and type III has an angular curve or “hook type” of acromion. The latter type was noted to be present in higher frequency with complete tears of the rotator cuff. Neer108 suggested an important role of the rotator cuff in maintaining a so-called watertight joint space and allowing continuation of the normal synovial fluid mechanics that maintain cartilage nutrition and may prevent secondary osteoarthritis. The scapulothoracic joint must also be considered when rotator cuff problems are managed. The scapula sits on the posteriorlateral aspect of the thorax. It is angled approximately 30 degrees anterior to the frontal plane. As a result of this, abduction of the
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arm relative to the scapula occurs 30 to 40 degrees anterior to the frontal plane. Abduction of the arm in the scapular plane places the rotator cuff muscles in their most efficient position and reduces tension on the joint capsule. The scapula is approximated to the thorax by the scapulothoracic muscles. These include the upper, middle, and lower trapezius, serratus anterior, rhomboideus major and minor, levator scapulae, pectoralis minor, and subclavius. These muscles must function to position and stabilize the scapula during movement of the arm. Inman et al70 described scapulohumeral rhythm as the coordinated motion between the scapula and humerus that occurs when the arm is elevated through its full range. During the first 30 degrees of elevation of the arm, motion primarily occurs at the glenohumeral joint and the scapula is said to be setting. Elevation of the arm beyond this occurs in a 2:1 ratio of glenohumeral to scapulothoracic motion. The total arc of elevation is a result of approximately 120 degrees of motion of the glenohumeral joint and 60 degrees of motion of the scapulothoracic joint. Motion of the scapulothoracic joint occurs as a result of elevation and rotation at the sternoclavicular and acromioclavicular joints. Normal scapulohumeral rhythm is important for normal function of the shoulder girdle; it allows for maintenance of the length-tension relationship of the rotator cuff muscles, which allows them to function efficiently throughout the full arc of motion. Additionally, proper movement of the scapula positions the glenoid under the humeral head to enhance glenohumeral stability. Poor motion and positioning of the scapula have been linked to impingement and rotator cuff problems.
Classification of injury Cuff tendon failure can be classified by various criteria. These include partial- or full-thickness tears, acute or chronic injury, and traumatic or degenerative etiology. The cuff pathology is almost always near the tendon insertion. It nearly always occurs in the supraspinatus component of the rotator cuff, because this is the area that is subject to mechanical impingement against the coracoacromial arch. A full-thickness tear extends from the bursal side through to the humeral aspect of the cuff. A partial tear may involve the bursal or the humeral side of the tendon. Acute tears occur suddenly and are found in only a relatively small portion of patients with rotator cuff pathology. Chronic tears are more common and are usually insidious in onset. It should be noted that the size of the complete tear can also be used to describe the pathology. A “massive tear” is the term used by Cofield33 to describe a defect more than 5 cm in diameter. The incidence of full-thickness rotator cuff tears has been documented in various cadaver studies as being between 5% and 26.5%.111,157 The incidence of cuff pathology has also been documented in clinical subjects. Age has been found to correlate with incidence.102 Moseley102 found that the incidence rose dramatically with the age of the patient. Traumatic cuff tears have also been found in patients with anterior-inferior dislocations. Arthrographically documented tears were seen in 30% in the fourth decade and 60% in the sixth decade.119 The role of secondary impingement and eccentric overload has been recognized in the pathogenesis of rotator cuff injuries in
throwing athletes.71 It is hypothesized that in throwing athletes, weakness and fatigue of the rotator cuff results in overload of the passive restraints. This results in laxity and subluxation of the glenohumeral joint and leads to secondary impingement. Additionally, the rotator cuff muscles are eccentrically overloaded as they attempt to stabilize the head of the humerus in the glenoid cavity. Repetitive eccentric overloading of the rotator cuff results in inflammation and injury to the rotator cuff tendons.
Clinical presentation History Most patients with rotator cuff pathology are over 40 years of age. Fifty percent of patients recall a traumatic incident that initiated the symptoms. They usually do not describe a major injury. One can usually elicit a history of recurrent “bursitis” and/or “tendonitis”; these episodes often resolve with rest or other conservative measures. With time, there is increasing shoulder discomfort. This is noted with forward elevation and external rotation of the arm against resistance. Patients may have complaints of nocturnal discomfort, particularly when sleeping on the affected side. Patients may describe crepitation with movement.
Physical examination The physical findings may be related to the underlying pathology. Crepitation would relate to the lack of smooth surfaces in the subacromial space. Weakness of flexion, abduction, and external rotation relates to loss of the tendonous attachment to bone. Upward riding of the humeral head on deltoid contraction results from a loss of the depressor action of the rotator cuff, and this further exacerbates impingement and cuff degeneration. Partial tears of the rotator cuff may cause pain with motion, crepitation, and stiffness. A complete tear may reveal a palpable defect of the cuff. As previously noted, associated tendonitis of the biceps may be present, and this should be documented. The patient should be examined for impingement signs. Specifically, this includes full-forward flexion with pain at terminal motion, otherwise known as the Neer impingement sign. Pain may also be elicited with the Hawkins test, a provocative test that elicits pain from impingement by bringing the arm into forward flexion, adduction, and internal rotation, thus driving the supraspinatus insertion into the coracoacromial arch and creating pain. The acromioclavicular joint can be stressed with cross-chest adduction. Stability of the biceps tendon should be elicited. Bicipital pathology tests include those of Speed and Yergason. Speed’s test reproduces pain with resisted forward elevation of the humerus against an extended elbow. The pain is localized to the bicipital groove area. Yergason’s test reproduces pain over the bicipital groove with resisted supination of the forearm with a flexed elbow. Muscle strength testing about the shoulder is part of the neurologic examination and should be documented.
Differential diagnosis When assessing a patient with a suspected tear of the rotator cuff, one should consider other underlying pathologies in the differential diagnosis. These include cuff tendonitis, bursitis, frozen shoulder, cervical spondylosis, suprascapular neuropathy,
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snapping scapula, acromioclavicular or glenohumeral arthritis, and glenohumeral instability.
Methods of treatment Despite rotator cuff pathology, not all patients are symptomatic, so aggressive treatment is not indicated in an asymptomatic shoulder. In a symptomatic shoulder, the goals of treatment are elimination of pain, restoration of function, and prevention of recurrence or progression.
Nonoperative treatment Nonoperative modalities of treatment include physical therapy, rest, elimination of aggravating activities, and administration of antiinflammatory medications and steroid injections. In one study, 44% of the patients with arthrogram-proven rotator cuff tears were shown to respond to nonoperative treatment.143 Successful nonoperative management of impingement and rotator cuff injuries requires an understanding of the anatomy and biomechanics of the shoulder girdle and an appreciation of the underlying etiology. Treatment is based on the patient’s signs and symptoms at examination. Progression should be based on the response to treatment. General goals for the rehabilitation of an individual with rotator cuff pathology are listed in the box on this page. Patients with acute signs and symptoms complain of constant pain at rest that is referred distally over the deltoid insertion, and they generally exhibit decreased motion with pain before resistance with passive testing. During this phase, the focus of treatment is on pain control. This includes the use of relative rest to avoid those activities that aggravate the symptoms. Additionally, the patient is encouraged to position the arm in abduction in the scapular plane. This reduces pain and prevents “wringing out” of the rotator cuff as described earlier. Pain-relieving modalities are used and may include ice, moist heat, and transcutaneous electrical nerve stimulation. Gentle mobilization and range-of-motion exercises are performed to prevent loss of motion and development of a stiff shoulder. Patients in the subacute phase have intermittent pain that is more localized to the shoulder. The pain may be aggravated by repeated movements. Motion may be limited and resisted testing may be weak and painful. During this period, treatment continues to consist of relative rest, and modalities can be used to decrease pain and promote healing. The intensity of exercise can be progressed. The focus is on restoration of the normal motion necessary for function of the individual. Full range of motion
Goals of rotator cuff treatment Control pain Restore motion Improve rotator cuff function Strengthen scapular muscles Correct posture Resume function Prevent recurrence
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must be restored, with particular emphasis on restoration of external rotation. External rotation is necessary so that the greater tuberosity can clear the acromion as the arm is elevated overhead. Joint mobilization techniques should be used if glenohumeral mobility is decreased. Often, the posterior capsule is tight and requires stretching. Stretching exercises can also be used to increase motion. Joint mobilization should be avoided for patients with hypermobility. For these patients, the focus of treatment should be on the development of dynamic stabilization. This requires strengthening of the rotator cuff and proprioceptive exercises to retrain the muscles to dynamically stabilize the glenohumeral joint. Finally, strengthening of the axioscapular muscles (serratus anterior, trapezius) is important to establish normal scapulothoracic motion and decrease the role of scapulothoracic dyskinesia in impingement biomechanics. Strengthening exercises begin with isometrics with the shoulder positioned in 30 to 45 degrees of abduction in the scapular plane. Active and light progressive resisted exercises are initiated as tolerated. These should specifically strengthen the rotator cuff muscles. Several studies have demonstrated maximum electromyographic activity in the rotator cuff muscles with a variety of exercises.18,146 The supraspinatus may be strengthened by performing abduction in the scapular plane with the arm internally rotated, but caution must be taken to avoid further impingement with this exercise. Additionally, the supraspinatus may be strengthened by performing prone horizontal abduction with the arm abducted to 100 degrees in the frontal plane and maximally externally rotated. The infraspinatus may be strengthened by performing prone horizontal abduction with the arm abducted to 90 degrees in the frontal plane and externally rotated. The teres minor may be strengthened by prone external rotation with the arm abducted to 90 degrees. The subscapularis may be strengthened by performing internal rotation with the arm at the side. Both eccentric and concentric phases of the rotator cuff exercises are emphasized. Adding excessive resistance to these exercises should be avoided because it will only result in substitution by larger muscles of the shoulder complex. These exercises must be performed precisely without substitution to develop specific muscles of the rotator. Internal and external rotation with the arm at the side of the body will not fully develop the rotator cuff. Strengthening exercises for the scapular muscles should also be included. Particular emphasis should be placed on strengthening the middle and lower trapezius as well as the serratus anterior. Successful treatment of rotator cuff injuries is dependent on an understanding of the underlying anatomy and biomechanics, as well as an appreciation of the underlying etiology. Treatment must be appropriate for the patient’s stage of inflammation. Knowledge of the functional demands placed on the shoulder is also necessary. Signs of overly aggressive treatment must be recognized and include increased pain greater than 2 hours after treatment and/or regression of motion or strength. If the patient’s symptoms do not improve after 3 to 6 months, further investigation with imaging modalities as discussed before is indicated. Some would suggest that nonoperative treatment should continue, but only about 50% of such patients respond.
Operative treatment Samilson and Binder135 outlined the following indications for operative repair: (1) a patient “physiologically” younger than
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60 years, (2) a clinically or arthrographically demonstrable fullthickness cuff tear, (3) failure of the patient to improve with nonoperative management for a period not less than 6 weeks, (4) a need to use the involved shoulder in overhead activities in the patient’s vocation or avocation, (5) full passive range of motion, (6) a patient’s willingness to exchange decreased pain and increased external rotator strength for some loss of active abduction, and (7) the ability and willingness of the patient to cooperate. Currently, anterior acromioplasty with limited detachment of the deltoid appears to be the most direct, least harmful, and most effective procedure for persistent rotator cuff tendonitis. Ellman43 documented an 88% satisfactory result rate in patients who have chronic impingement treated by arthroscopic acromioplasty. Simple debridement of partially torn rotator cuffs has allowed an 85% rate of return to activity in a group of patients treated by Andrews et al.7 Although acromioplasties are still routinely performed in conjunction with rotator cuff repairs, recently Matsen and coworkers91 published their results on 96 patients who underwent mini-open rotator cuff repair without acromioplasty. Significant improvement in self-assessed shoulder comfort and in each of the 12 shoulder functions was observed. Burkhart26 published results of arthroscopic treatment of massive rotator cuff tears. He treated 10 patients with painful, massive, complete tears involving primarily the supraspinatus with arthroscopic acromioplasty and rotator cuff debridement. All patients except one had normal preoperative motion and strength. These patients maintained adequate mechanics of the glenohumeral joint during abduction because there is a balance of two important force couples.120 The first force couple is in the coronal plane and consists of the rotator cuff and deltoid such that the rotator cuff maintains a fixed fulcrum for rotation of the deltoid during abduction. The second force couple acts in the transverse plane and consists of a balance between the anterior and posterior portions of the rotator cuff that allows the humeral head to maintain centering during rotation of the glenohumeral joint. This study showed that normal shoulder function is possible with massive unrepaired rotator cuff pathology. Similar results were seen with Motycka et al104 with their cohort of 64 patients with large rotator cuffs tears followed for a mean period of 5 years. As arthroscopic techniques improve, more surgeons are treating rotator cuff pathology arthroscopically. Several articles have been published demonstrating equal results comparing all arthroscopic versus mini-open rotator cuff repair.25,137,148 However, for most cuff tears that come to operative management, an open approach is still used. The extent of the rotator cuff tear is ascertained at the time of surgery, and the torn edges of the rotator cuff are identified. The following sequence has been suggested for closure: (1) resection of the bursal scar, (2) identification of the tear, (3) assessment of tissue mobility, (4) mobilization of the rotator cuff, and (5) planning for closure, either side to side or in most cases to a trough in bone.81 Concomitant acromioplasty is performed in these patients. Long-term results of this technique were reported by Bigliani et al.16 In patients with an average follow-up of 7 years, 85% had satisfactory results with adequate pain relief and 92% could raise the arm above the horizontal plane. Many techniques have been described for massive tears that cannot be treated as just outlined. These options include accepting the defect, moving local tissue into the deficient area, and inserting a free graft of local or distant tissue, that is, either an allograft,
xenograft, or prosthetic material.34 Latissimus dorsi transfer for the treatment of massive tears of the rotator cuff has been described by Gerber et al.53,55 In cases with good subscapularis function but irreparable defects in the external rotator tendons, restoration of approximately 80% of normal shoulder function was obtained. In fact, in a cohort of patients with massive rotator cuff tears, Harryman et al59 reported patient satisfaction regarding comfort and function despite greater than 50% demonstrating recurrent tears determined by ultrasonography.
Postoperative care Postoperative care after surgery on the rotator cuff is dependent on the status of the deltoid, the size of the repair (i.e., small versus massive), the ability to mobilize tissue, and the safe range of motion achieved at surgery. Therefore, postoperative care must be individualized to the patient and the procedure rather than everyone being treated with a standardized protocol. Immediate postoperative care after rotator cuff surgery should protect the healing structures, control pain, and restore range of motion. For small tears, the arm is generally immobilized at the side for 4 to 6 weeks with a deltoid-splitting technique. Painrelieving modalities can be used to improve comfort. Passive range-of-motion exercises are begun immediately postoperatively and performed several times per day in the range prescribed by the surgeon. Once sufficient healing has occurred (i.e., at 4 to 6 weeks), active assisted and active range-of-motion exercises can be initiated. Strengthening exercises using isometrics can also be initiated at this time. Postoperative management after the repair of massive tears in which the deltoid was detached includes immobilization for up to 6 weeks. Generally, an abduction pillow is used to reduce tension on the postoperative repair. Modalities are used to control pain as necessary. Passive range of motion is performed for the first 6 weeks. The safe range of motion achieved at surgery must be communicated by the physician to the therapist. Active assisted and active range-of-motion exercises are delayed for 6 weeks to ensure adequate tissue healing. Isometric strengthening exercises are usually delayed until 12 weeks after surgery. Once sufficient time for healing has passed, the patient is gradually progressed through the rehabilitation program. Initial emphasis is on restoring the motion necessary for normal function of the shoulder complex. Attention is directed at reestablishing normal scapulohumeral rhythm. Additionally, strengthening exercises focus on developing the rotator cuff and scapular muscles. Functional activities are incorporated to allow gradual resumption of function. The patient must be willing to accept some limitation in level of function. In patients who complain of shoulder pain, pathology of the rotator cuff is important to consider because of the large spectrum of disease from impingement to complete and massive tears of the rotator cuff. Many patients may respond to nonoperative therapy, although slightly fewer than 50% may fall into this group. After careful history taking and physical examination, most patients can initiate a course of nonoperative management. In those patients who do not respond, imaging of the cuff is the next appropriate step in the algorithm. In patients with simple tendinitis or impingement, conservative management is continued. If symptoms persist, acromioplasty, either open or with endoscopic techniques, can be considered. Patients with complete disruption
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or full-thickness disruption may be candidates for other operative approaches as outlined earlier. The most direct and simple repair technique is often the most appropriate: progression from direct tendon repair, to repair of bone, to transposition of local tissue, to grafting. Postoperative support should vary according to need. Physiotherapy after surgery is a vital part of the treatment protocol.
SHOULDER INSTABILITY A rational approach to surgical management of instability should be based on an understanding of the definition of successful repair and an appreciation of the reasons for failure. Successful surgery is traditionally defined as elimination of recurrence of instability. According to this definition, up to a 97% rate of excellent results has been reported with a large variety of procedures.* Both operative and nonoperative treatment must be based on an appreciation of the spectrum of glenohumeral instability. A classification system for shoulder instability should include the following factors: frequency of occurrence, etiology, direction of instability, and degree of instability. One can distinguish between traumatic recurrent instability and atraumatic recurrent instability. The former occurs as a result of a single episode of macrotrauma, is usually unilateral, is less responsive to a rehabilitation program, and has the Bankart lesion as the most common primary pathology. The latter may occur as the result of repetitive microtrauma (e.g., swimming or throwing), may be bilateral, is responsive to a therapy program, and has excessive capsular laxity as the most common primary lesion. Voluntary instability is found in a subset of individuals with a traumatic instability. These patients can be further subdivided into two groups. Group I patients with voluntary instability have an arm position-dependent instability that is usually posterior but may be anterior. These patients usually respond to rehabilitation and do not have an underlying psychiatric disturbance. If they remain refractory to conservative treatment, they may be well managed by surgery. Group II patients have the ability to selectively contract muscles to create a dislocation. Some of these individuals have an underlying psychiatric disturbance and use their instability as a trick to control their environment.131 These individuals are not candidates for surgical treatment and are better managed by psychiatric counseling and conservative rehabilitation. There is a spectrum of glenohumeral instability in which subluxation and dislocation represent degrees of injury to the capsulolabral structures. Dislocation is defined as complete separation of the articular surfaces, and subluxation represents increased humeral head translation within the glenoid to a degree beyond normal tissue laxity. Because the parameters of normal glenohumeral translation have not yet been fully defined,136 clinical subluxation is defined as detectable glenohumeral translation with accompanying symptoms. The increased use of arthroscopy has led to the characterization of an additional group within this spectrum of instability. This group appears to be throwing athletes in whom symptomatic labral tears or attrition develops secondary to increased glenohumeral translation without clinical subluxation.4,6,9
*References 1, 2, 6, 14, 21, 22, 29, 41, 47, 72, 84-88, 90, 97, 101, 109, 112, 124, 130, 139,144.
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Appreciation of the direction of instability is critical to selection of a successful approach to treatment. Traditionally, 95% of all instability has been observed to be simple anterior instability; however, there has been increasing recognition of significant posterior instability in athletes who are loose-jointed individuals.8,52 Posterior instability is usually subluxation inasmuch as dislocation occurs only with rarer traumatic episodes.52 Since Neer and Foster’s article on multidirectional instability (MDI), there has been an increasing awareness of both atraumatic and traumatic capsular laxity occurring in more than one direction. The main direction of instability is usually anterior, although inferior instability appears to be the hallmark of this diagnosis.5,37,49,109,112 Traditional procedures that treat anterior capsular laxity by Bankart repair or capsular plication do not adequately manage the associated components of inferior and/or posterior instability. In the worst scenario, these procedures can actually lead to instability in the opposite direction. Failure of the operative approach may occur at any point in the course of treatment and may be due to either physician or patient error or a combination of the two. For a successful outcome, the diagnosis, surgical procedure, and rehabilitation must be individualized and appropriate in each case. A correct diagnosis is critical in categorizing the instability and recommending the appropriate form of treatment. For example, a misdiagnosis of impingement or failure to recognize a concomitant rotator cuff tear in a patient over the age of 50 may lead to failure despite a technically adequate anterior stabilization procedure. Additionally, a Bankart procedure that ignores the inferior component of capsular laxity in a patient with MDI will fail. Assuming a correct diagnosis, a variety of technical pitfalls is encountered with each type of stabilization procedure. Appropriate anterior capsular tension must be restored, and procedures that over-tighten the anterior capsule or subscapularis tendon may result in serious functional limitation of external rotation. In some cases this may lead to osteoarthritis or exacerbation of posterior instability in patients with unrecognized MDI.63,159 Knowledge of the regional anatomy or an inadequate exposure predisposes to an inadequate repair and possible neurovascular injury.125 Assuming the correct diagnosis and correct procedure, the failure of patient compliance or inappropriate rehabilitation may result in limited range of motion or recurrence of instability. To avoid complications of treatment, it is critical to be both sensitive and specific in the initial diagnostic assessment of the individual’s shoulder complaints. Both the degree and direction of any instability must be accurately determined, and any associated fractures, neurovascular injury, or concomitant rotator cuff pathology must be identified.
Impingement syndrome Impingement syndrome may occur either as an isolated entity or in combination with instability.62,156 Hawkins and Hawkins63 identified several patients whose untreated impingement syndrome was the cause of their ongoing pain after anterior shoulder stabilization. This should not be confused with the common finding in patients with anterior instability of pain located posteriorly in combination with clinical findings consistent with impingement
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syndrome.64,150 This impingement pain is likely a secondary phenomenon related to repetitive traction and compression of the rotator cuff during subluxation or to overwork of the rotator cuff muscles in an attempt to maintain the humeral head centered in the glenoid in the setting of capsular insufficiency. Jobe et al72,134 described this overlap in the literature, and Altchek et al6 observed a 20% incidence of impingement symptoms in individuals with surgically confirmed anterior-inferior MDI. In most cases it is possible to correctly diagnose impingement syndrome from the history and examination; however, if this evaluation is inconclusive, examination under anesthesia and arthroscopic inspection assist in clarification of the diagnosis. Anterior shoulder instability in a patient older than 40 years of age is a unique situation that deserves special consideration if complications and failure of treatment are to be avoided. The association of concomitant anterior shoulder dislocation and rotator cuff tear has been reported by numerous orthopedic surgeons.† This concomitant injury may be missed if one is not attentive. Moreover, there is an increased risk for adhesive capsulitis in this older group of patients if early range of motion is not begun after reduction of a dislocation. The incidence of an associated rotator cuff tear in this group has been reported to be as high as 70% to 90%.62,94,95 Most recently, Neviaser et al113 and Hawkins et al62 increased our understanding of this problem. Anterior dislocation in an older individual may result in disruption of a rotator cuff that has undergone age-related attrition. The anterior capsulolabral structures are spared.62,123 McLaughlin92 and subsequently Craig38 termed this the posterior mechanism of anterior shoulder instability. In older patients with persistent external rotation and abduction weakness after the reduction of an anterior dislocation, physicians should avoid the trap of assuming an axillary nerve injury as the etiology.38,113 The overall incidence of clinically significant axillary nerve injury in this setting has been reported to be in the range of 9% to 18%.19,126 Neviaser et al113 observed an incidence of 7.8% for axillary nerve injury in association with rotator cuff tear after anterior dislocation. A suprascapular nerve injury is rare in the setting of anterior dislocation.38 In general, older patients have a lower rate of recurrence of instability after an initial episode of anterior instability.132 This is particularly true if there is an associated fracture of the greater tuberosity that reduces the range of motion of the joint and muscle strength.95,126 In older patients with an unrecognized rotator cuff tear, pain and weakness appear to be more common problems than recurrent instability.62,113 In a separate group of older patients, recurrent anterior shoulder instability develops as the result of an excessively redundant anterior capsule and no rotator cuff tear.77 These individuals typically demonstrate the stigmata of generalized ligamentous laxity, including thumb to forearm; hyperextension of the elbow, knee, and metacarpal joints; a history of easy bruising, hernias, and scar spreading; and excessive skin laxity. These features should be documented during the examination. An approach to treating older individuals (>45 years) after an initial shoulder dislocation is based on classifying such patients into three groups:
†References
32, 65, 93-95, 113, 142.
Group I: If after reduction no significant weakness of external rotation or abduction is found, immobilization should be continued no longer than 7 to 10 days. A gentle range-ofmotion program should begin and progressive supervised therapy should follow. Failure to move the shoulder early in these patients can result in marked limitation of motion. Group II: Patients with persistent pain and external rotation and abduction weakness likely have an associated rotator cuff tear. Early arthrography and electromyography should be performed to confirm this fact and to rule out any associated axillary nerve injury. Conservative treatment in this setting usually results in a poor outcome.63 Early repair of the rotator cuff generally yields good results, and surgery performed after a delay in diagnosis may be fraught with difficulty because the cuff tissues may become extensively scarred and difficult to mobilize.62,113 If the patient does have an associated axillary nerve injury, we would still perform an early repair of the cuff, although final function will likely be determined by return of axillary nerve function. Group III: Recurrent instability in older patients may be due to either a rotator cuff tear or excessive capsular laxity.62,77,113 Labral lesions may occur but are less common in this group. Examination usually reveals those patients with generalized ligamentous laxity, but an arthrogram is essential to clarify the status of the rotator cuff. It is prudent to know the pathology before surgery is attempted because most cuff pathology is best treated through an anterior superior approach with an acromioplasty, whereas anterior capsulolabral pathology is managed through a deltopectoral interval approach. It should be noted that Neviaser et al113 observed a significant subscapularis tear in all cases of recurrent instability. Fracture of the greater tuberosity, the second most common associated fracture after the Hill-Sachs lesion, occurs in about 10% of all anterior dislocations.92 In most cases this fracture reduces anatomically with reduction of the glenohumeral joint and recurrence of shoulder instability is actually less than if no fracture were present.92 Displacement of the greater tuberosity fragment more than 1 cm may result in residual impingement and blocked external rotation. In these cases, surgical reduction and fixation may be necessary. A glenoid rim fracture may occur with anterior dislocation and continued displacement of the anterior glenoid articular surface of greater than 25% to 35% results in recurrent instability.11,80,129 Computed tomography demonstrates this clearly, and surgical reduction and fixation may be necessary if residual displacement is greater than 2 mm. The axillary nerve is the most commonly injured neurovascular structure, with the reported incidence ranging from 5% to 33% in first-time dislocators.19,130 Both a motor and sensory examination should be performed before and after any reduction maneuver because complete motor paralysis may occur without any detectable hypoesthesia. Any residual neurologic deficit persisting longer than 3 to 4 weeks should be evaluated by electromyography.19 Most patients spontaneously recover over a 6-week period inasmuch as most of these injuries are neuropraxic in nature. The axillary artery is occasionally damaged with anterior dislocation because it is relatively fixed as it passes beneath the pectoralis minor and over the subscapularis.39,73,92,126 This is particularly the case in older individuals, in whom atherosclerosis
Chapter 5d
may render the vessels less compliant to displacement. Clinical findings include severe pain, expanding hematoma, and diminished peripheral pulses; an arteriogram should be performed urgently in such cases because timely repair is crucial to a successful outcome. Failure to recognize the voluntary aspect of a patient’s instability may result in the failure of any procedure for recurrent instability. Rowe et al131 described a typical patient in this group as an adolescent with an underlying psychiatric problem, without any prior history of significant trauma, who can voluntarily dislocate his shoulder and who has essentially normal radiographic findings. As already noted, group I patients are typically emotionally stable individuals with positional instability.52 Group I patients represent a subset of atraumatic voluntary instability, and if they fail to respond to conservative management, an operative procedure that reduces the excessive capsular laxity is a reasonable alternative. It is crucial to sort out this group from those in group II, who have a muscular-control type of voluntary instability that may be used as a trick to control the environment. These individuals are managed by psychiatric counseling and rotator cuff strengthening exercises. The spectrum of MDI includes those individuals with excessive ligamentous laxity (atraumatic type), those with instability resulting from repetitive overhead activities with extremes of motion (microtrauma type), and those with instability after violent trauma (macrotrauma type).6,140 Recognition of MDI is critical because traditional stabilization procedures such as the Bankart or Bristow operations fail to adequately address the inferior component of instability.‡ Moreover, too tight an anterior repair in this setting may actually aggravate the posterior component of MDI.64,159 The diagnosis of MDI is based on the history and the classic finding of a significant “sulcus sign” in addition to anteriorposterior laxity demonstrated with a load-and-shift maneuver. Furthermore, 50% of these individuals usually have stigmata of generalized ligamentous laxity. Up to 50% to 70% of these individuals respond well to a rehabilitation program aimed at rotator cuff strengthening if it is coordinated with activity modification. This is in contrast to young individuals with posttraumatic, unidirectional, anterior recurrent instability, who often require surgery.27 Missed unreduced anterior dislocation may occur in elderly patients, individuals with substance abuse, individuals with seizure disorders, and unconscious polytraumatic patients.60,133 Unlike missed posterior dislocations that go unrecognized because of a failure to perform an adequate radiograph, missed anterior dislocations are usually due to a failure to perform an initial or follow-up radiograph.60 The chronicity of the dislocation must be established. If an anterior dislocation is less than 6 weeks old and no concomitant osteoporosis or history of steroid use is present, an attempt at mild gentle closed reduction may be made under general anesthesia.60 In cases with chronic unreduced dislocations older than 6 weeks, open reduction and stabilization are recommended. In these cases, an axillary radiograph confirms the diagnosis; however, computed tomography gives valuable information about the status of the humeral head and glenoid. It is helpful to have this information before surgery because
‡References
6, 49, 54, 90, 109, 112, 121, 126, 127, 140.
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significant bone loss of the anterior glenoid or posterolateral humeral head may necessitate supplemental bone grafting. In older individuals, an arthrogram may also be appropriate to rule out an associated cuff injury. An anterior surgical approach through the deltopectoral interval is recommended. If necessary for exposure, the superior 1 cm of the pectoralis major insertion may be detached. The anterior 1 cm of the conjoined tendon insertion at the level of the coracoid process can be divided. The subscapularis is usually contracted and fibrotic along with the capsule and rotator cuff, and the axillary nerve may be stretched tightly across the anterior glenohumeral joint. This must be kept in mind during release of these tight anterior structures. After release of the subscapularis and capsule, it is often necessary to remove granulation tissue within the joint before the humeral head is reduced. After reduction and repair of the capsule, early motion is preferred rather than spica immobilization advocated by some surgeons.60 Management of glenoid bone deficiency and large Hill-Sachs lesions is discussed later. In cases in which the dislocation is older than 1 year or when the Hill-Sachs lesion is larger than 50% of the articular surface, the humeral head may no longer be viable and a hemiarthroplasty may be the best alternative treatment. In these cases, placement of the prosthesis at an angle greater than the normal retroversion of 30 degrees (50 to 60 degrees) helps prevent the recurrence of anterior instability. Although most procedures have a success rate in excess of 95% in providing stability to the shoulder, no single surgical technique is perfect. In general, procedures that do not address specific pathology should not be used in the primary surgery setting. An individualized approach to each situation is recommended, because a variety of pathologic lesions may be present in different patients. The optimum technique, as defined by Cofield et al,35 would be one with the following characteristics: low recurrence rate, low complication rate, low reoperation rate, low rate of osteoarthritis (uses no hardware), no limitation of motion, anatomic treatment of pathology, and no technical difficulty. Because no one procedure satisfies all these criteria, we present specific pitfalls and their management for a variety of common anterior stabilization techniques.
Examination under anesthesia and diagnostic arthroscopy It is essential to confirm both the direction and the degree of instability by examination under anesthesia before any surgical procedure. This aids in the decision of which operative approach and procedure to use. One should perform a drawer test on the shoulder to assess the amount of anterior, posterior, and inferior translation of the humeral head in the glenoid. Anterior and posterior translation is assessed with the shoulder at 90 degrees’ abduction and neutral rotation and is graded on a scale of +1 to +3 (+1 is movement of the humeral head to the rim but not over it, +2 represents humeral head dislocation over the glenoid rim with spontaneous reduction when pressure is released, and +3 is frank dislocation of the humeral head that does not reduce spontaneously).6 One should not be surprised to find increased
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posterior translation along with anterior translation when a patient with suspected anterior instability is examined because injury to the ligaments on both sides of the joint may occur with an anterior dislocation.115,136 Inferior instability is assessed by the presence of a “sulcus sign.” This test is performed with downward traction on the adducted arm, and the degree of acromiohumeral interval separation is noted.150 The “sulcus sign” is graded on a scale of +1 to +3 (+1 is 0 to 1 cm, +2 is 1 to 2 cm, +3 is greater than 2 cm).6 Arthroscopic inspection may occasionally be useful in these patients, although office examination, history, and an examination under anesthesia usually confirm the diagnosis. Most labral lesions below the equator of the glenoid are associated with a deficient inferior glenohumeral labrum.
Surgical procedures for instability The classic Bankart procedure13,118 and its modifications72,130,144 anatomically repair a detached glenoid labrum together with the inferior and middle glenohumeral ligaments. Several variations in handling of the subscapularis deserve mention. Thomas and Matsen144 described a technique first proposed by Ellison. The subscapularis and capsule are both divided laterally, with medial retraction allowing repair of the Bankart lesion with the joint in an inside-out fashion. This approach is useful in revision cases in which extensive scarring is found medially at the glenoid. Jobe and Glousman72 recommended longitudinal division of the subscapularis muscle with preservation of its lateral insertion on the lesser tuberosity. This approach is designed to minimize scarring and shortening of the muscle in a throwing athlete. Several potential problems with this approach include limited inferior exposure in cases in which a capsular shift might be necessary and the potential for injury to the axillary nerve and brachial plexus if longitudinal splitting is carried too far medially. To repair the Bankart lesion once the sutures are well placed through the bony anterior glenoid rim, the lateral capsule is repaired to the rim. A potential error here is to not address any concomitant capsular laxity. The standard Bankart procedure handles capsular laxity by placing the sutures more laterally through the lateral capsular flap. The T-plasty repair pulls the inferior portion of the capsule superiorly before placement of the sutures through the capsule. The inferior capsular shift procedure as originally described by Neer and Foster112 is designed to treat excessive capsular laxity occurring with MDI. It has been used successfully and involves detachment of the capsule laterally along its humeral attachment with a superior-lateral shift of the inferior flap and then an inferior-lateral shift of the superior flap.40,49 Repair of an associated Bankart lesion is performed first, and failure to address this lesion has been associated with failure of the procedure.87 Inferior detachment of the capsule laterally along the humeral neck probably involves less risk to the axillary nerve than does a medial paraglenoid capsulotomy incision; however, there is still significant risk with inferior dissection, and Neer109 observed three cases of axillary nerve neuropraxia early in his experience. To avoid this potential complication, the inferior flap should be developed by placing stay sutures in the capsule and pulling superiorly while
applying progressive external rotation. An elevator is placed inferiorly and used to remove any muscle from the capsule before its division. If the axillary nerve cannot be palpated and its exact location is not precisely known, it should be visualized before division of the inferior capsule. A T-plasty procedure can be performed to manage capsular laxity and concomitant labral detachment simultaneously.6 The basic goal of the T-plasty is to restore proper tension in the inferior glenohumeral ligament by advancing this structure superiorly and medially. At completion of the capsular repair, external rotation with the arm at the side should be in the range of 35 to 45 degrees without undue tension on the repair. The Bristow procedure and its modifications basically involve fixation of the coracoid process and attached conjoined tendon to the scapular neck through a split in the subscapularis tendon.§ The procedure theoretically functions by provision of an anterior bone block, formation of a dynamic musculotendinous sling, and partial tenodesis of the inferior third of the subscapularis tendon. It does not directly address pathologic lesions such as labral detachment or capsular laxity. Although the Bristow procedure has a success rate comparable with that of other procedures, it is generally accepted to be a poor alternative for stabilization in athletes involved in overhead sports, because it may limit external rotation.14,66,85,86 The orthopedic literature has documented a high incidence of complications with this procedure.10,12,46,159 The major risk with the Bristow procedure is injury to the musculocutaneous nerve.12,15,48,125,159 This complication is usually due to inadequate knowledge of variations in regional anatomy or poor surgical technique.125 Significant variations in anatomy of the conjoined tendon and musculocutaneous nerve may be encountered.48,125 The musculocutaneous nerve, in most cases, enters the coracobrachialis muscle at a distance of 5 or more cm distal to the coracoid process; however, in 5% of cases it may also be as close as 2.5 cm from the tip of the coracoid.12,48,125 If the nerve is observed to enter the muscle at 2.5 cm or closer to the coracoid process, the Bristow procedure should not be performed. Finally, staple fixation may impinge or rupture the biceps tendon with improper placement. The Putti-Platt procedure treats anterior instability by shortening the subscapularis in a “vest-over-pants” technique to limit external rotation.22,68,84,116 The subscapularis is detached 2.5 mm medial to its insertion, and the capsule and subscapularis are then sutured to the glenoid rim with the arm in internal rotation. The main complication of this procedure is loss of function from excessive limitation of external rotation, and in the extreme case this may result in secondary glenohumeral arthritis caused by excessive constraining forces on the articular surfaces.61 Instability may also result if the patient has unrecognized MDI.63 In the duToit capsulorrhaphy procedure, a staple is used to effect a Bankart-type repair, and complications stem from problems with staple fixation and placement.20,42,139 Injury to the articular surface and loosening of the staple have been reported.160 Metal devices are mentioned here for their historical role in the development of arthroscopic Bankart repairs.
§References
138, 145.
2, 3, 10, 14, 21, 29, 30, 41, 47, 57, 66, 67, 69, 82, 85, 86, 89, 96, 114,
Chapter 5d
The enthusiasm for arthroscopic stabilization of anterior shoulder instability is based on the assumption that limited disruption of the anterior soft tissues results in a better functional outcome. This is particularly relevant to young throwing athletes who require full external rotation and power. Although short-term studies with 2- to 3-year follow-up are encouraging, long-term data supporting this assumption are not available.44,76 However, three recent meta-analyses comparing arthroscopic versus open repair for traumatic anterior shoulder instability both concluded that open repair has a more favorable outcome with respect to recurrence and return to activity.36,50,98 Because arthroscopic management of instability has been in evolution over the recent years, the conclusions drawn from the meta-analyses may be biased toward success of open repair. The technique, which was originally popularized by Johnson,74 uses a dual-pronged staple and attempts to reproduce the duToit capsular staple-Bankart repair arthroscopically.4,42,150 Since then, modified techniques have included the use of a removable rivet,154 modified staple capsulorrhaphy,56 cannulated screw and ligament washers,158 and suture Bankart repair.4,31,99,100 The ideal patient is an individual with posttraumatic, recurrent, anterior, unidirectional instability with labral detachment below the level of the equator of the glenoid. Patients with MDI are not candidates for this procedure. Routine examination of patients under anesthesia is performed before the procedure. Individuals with a significant sulcus sign that does not lessen with external rotation and adduction are treated with a rotator interval closure. One can use a suture technique in which absorbable sutures are placed through the inferior glenohumeral ligament and a Bankart repair is achieved through transscapular drill holes.4,31,99,100 Drill holes are placed above the equator on the anterior scapular neck to allow restoration of tension in the inferior glenohumeral ligament as it is pulled superiorly and medially with the repair. More recently, the use of a biodegradable cannulated tack to avoid problems associated with hardware or drilling across the scapula has been discussed.149 No matter what form of fixation is used, it is essential to adequately prepare the anterior scapular neck to ensure a bleeding bony bed for the repair. When a motorized burr is used, care should be taken not to slip over the glenoid rim and injure the articular surface. Injury to the suprascapular nerve is a theoretical risk with pin placement through the scapula. Excessive lateral penetration of the pins should be avoided.100 In conclusion, many pitfalls and complications are potentially encountered in surgery for shoulder instability. The shoulder surgeon must have an organized approach to diagnosis and treatment. If surgery is contemplated, the procedure must be tailored to the individual patient and must deal with the underlying pathology.
FRACTURES AND DISLOCATIONS ABOUT THE SHOULDER Fractures and dislocations about the shoulder are very common injuries. These injuries are best classified by anatomic location for the purpose of discussion. Shoulder girdle injuries are located at the sternoclavicular joint, clavicle, acromioclavicular joint,
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Fractures and dislocations about the shoulder
proximal end of the humerus, and scapula. An associated neurovascular injury may or may not be present.
Sternoclavicular joint Most often, sternoclavicular dislocations do not cause any significant functional disability.24 An anterior dislocation is usually asymptomatic and does not require any treatment. Posttraumatic ankylosis of the sternoclavicular joint can cause pain and disability. Compression of the mediastinal structures can occur with posterior dislocations of the sternoclavicular joint. In general, anterior injuries can be treated conservatively and posterior injuries may require some intervention. Surgical management of chronic sternoclavicular dislocations may include soft tissue reconstruction, arthrodesis, resection of the medial aspect of the clavicle, and resection combined with costoclavicular ligament reconstruction.
Clavicle Clavicular fractures account for greater than 60% of shoulder girdle fractures. The middle third of the clavicle is involved in 82% and the distal third in 15%.128 Nonunion of the clavicle is relatively uncommon and reported in 1.8% of those patients treated nonoperatively.128 If a nonunion does occur, most often it is minimally symptomatic. One study has determined that atrophic nonunions are less likely to become symptomatic than are hypertrophic nonunions.155 In a study by Johnson and Collins,73 26 clavicular nonunions treated nonoperatively resulted in 23 excellent results, 2 good results, and 1 poor result. Rowe128 noted spontaneous uniting of apparent nonunions as long as 5 months from the time of injury. Only patients with significantly symptomatic nonunions and malunions should be offered reconstructive surgery. Malunion of the middle third of the clavicle, if symptomatic, can be managed with osteotomy and bone grafting. This is supplemented with internal fixation. Nonunions can be managed by excision of the pseudoarthrosis, reduction, bone grafting, and internal fixation with promising results.75,110 Distal clavicular nonunions, which can result after type II distal clavicle fractures, have been treated by excision of the distal fragment and/or open reduction and internal fixation. The results of excision cannot be recommended.73 Neer107 documented some success with transacromial wire fixation. The fixation is removed after union has occurred. However, cases of migratory hardware have made pin or wire fixation less appealing.
Acromioclavicular joint Of shoulder girdle dislocations, 9% involve the acromioclavicular joint. Fifty percent are complete grade III or higher dislocations with disruption of the conoid and trapezoid components of the coracoclavicular ligaments.128 Most acute acromioclavicular injuries can be treated nonoperatively: application of ice over the first 24 hours, possibly a sling for comfort, and resumption of activity at approximately 1 week if tolerated. Posterior displacement of the clavicle is
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uncommon and may require surgery to reduce the clavicle. It may be wedged into the angle between the acromion and the spine of the scapula. One may attempt a closed reduction by displacing the shoulder posteriorly to widen the distance between the acromion and sternum. Treatment of injuries that involve complete separation of the acromion and clavicle is controversial. Some have attempted closed reduction with pressure by tape or a splint, but significant problems with the skin have been noted when these techniques are used. Surgery for acute grade III lesions has included many techniques105: direct acromioclavicular joint stabilization with ligament repair; clavicle stabilization by attachment to the coracoid, as with a Bosworth screw, wire, Dacron tape,58 silk sutures, or absorbable suture; and resection of the outer end of the clavicle and coracoclavicular ligament stabilization with the coracoacromial ligament.151 Most patients with chronic acromioclavicular subluxations or dislocations are asymptomatic or minimally symptomatic and respond well to nonoperative management. Occasionally, acromioclavicular subluxations become symptomatic.105 Degenerative joint disease or osteolysis of the distal end of the clavicle may develop. These problems can be assessed with an acromioclavicular view on plain radiographs and by injection with local anesthetic to confirm the diagnosis with pain relief.
Proximal humerus fracture dislocations The classification of proximal humeral fractures is based on the absence or displacement of each of four major segments: the humeral head, the greater and lesser tuberosities, and the humeral shaft. The Neer classification is most commonly used and considers the segment displaced if there is greater than 45 degrees of angulation or 1 cm of displacement. It should be noted that all patients with a suspected fracture of the proximal end of the humerus require a shoulder trauma series of radiographs. This includes anteroposterior, lateral, and axillary views. The treating physician must exclude concomitant dislocation of the humeral head. A complete vascular and neurologic examination must be performed and documented. Treatment considerations include the patient’s age, functional demands, dominance, expectations, anticipated compliance, degree of segment displacement, and bone quality. Most of these fractures can be managed with protective immobilization and early range of motion. This is, of course, based on the aforementioned factors and includes fracture stability. In a prospective randomized study of proximal humerus fractures (minimally displaced), Kristiansen et al79 compared 1 and 3 weeks of immobilization before starting physical therapy. Shorter immobilization resulted in better functional results during the first 3 months. After 6 months, the results in both groups were essentially the same. Fractures that are more significantly displaced require reduction. This can be accomplished by closed means or with open reduction and internal fixation. Occasionally, prosthetic replacement is preferred. Available internal fixation includes tension band wires, screws, percutaneous pins, plates and screws, and intramedullary nailing. There is a trend toward open reduction and internal fixation as newer types of locking plates become more commonly implemented.45 This restores anatomy and provides fracture stability. The risk of avascular necrosis increases with
fracture comminution and displacement, but conversion to hemiarthroplasty is always a possibility after attempted fracture fixation. Two-part lesser tuberosity fractures are often associated with posterior glenohumeral dislocation. Smaller fragments can be treated nonoperatively: Larger fragments may require open reduction and internal fixation. Two-part greater tuberosity fractures may include a tear of the rotator cuff. This requires open reduction and internal fixation with either a tension band wire or screw and repair of the rotator cuff tear. Two-part fractures of the anatomic neck are uncommon and carry a significant risk of osteonecrosis. Flatow et al48 published a series of 12 two-part greater tuberosity fractures that were treated surgically by open reduction and internal fixation with a heavy nonabsorbable suture and careful repair of the rotator cuff. All fractures healed, and early range of motion resulted in good or excellent results in all patients. Two-part surgical neck fractures can be either impacted or completely displaced and unstable. Options for treatment include closed reduction, with or without percutaneous pinning, or open reduction and internal fixation. Kowalkowski and Wallace78 published a series of 22 displaced fractures treated with closed percutaneous Kirshner wire stabilization of the surgical neck. Significant problems in obtaining adequate reduction and migration of the smooth pins were encountered. Unsatisfactory results were more common in the older age group (greater than 50 years old). In three-part fractures, closed reduction is often difficult to maintain, and therefore open reduction is required. Tensionband wiring can often be used because it incorporates the rotator cuff in the repair. If the fracture is severely comminuted or the bone osteoporotic, a hemiarthroplasty can be considered, especially in elderly patients. In young patients with a four-part proximal humerus fracture, an attempt at open reduction and internal fixation is considered despite the high risk of osteonecrosis. If reconstruction is not possible or the patient is elderly and has poor bone stock, a hemiarthroplasty is preferred. As discussed earlier, it is important to eliminate the presence of concomitant dislocation of the humeral head. Isolated dislocations without fracture can be seen. Many posterior dislocations of the humeral head are missed and recur chronically. These patients most often complain of decreased range of motion. They may or may not complain of pain. Articular impression fractures can often best be imaged with computed tomography. In general, closed reduction can be considered if the injury is less than 6 weeks old; after 6 weeks, open reduction is required. Treatment of the articular impression defect is based on the percentage of head involvement. If the defect is less than 20%, it is generally stable after a period of immobilization. If the defect is between 20% and 40%, a transfer procedure into the defect may be required, as well as possibly a subscapularis transfer for posterior dislocations or infraspinatus transfer for anterior dislocations. A hemiarthroplasty may be used if the defect is greater than 40% of the head or if significant degenerative changes are present.
FROZEN SHOULDER Frozen shoulder—also termed adhesive capsulitis—has many underlying causes. It can be seen in association with other shoulder
Chapter 5d
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References
pathologies, for example, posttraumatic, postsurgical, and rotator cuff pathology. It is also associated with other disease entities, including insulin-dependent diabetes mellitus, parkinsonism, cardiovascular disease, and thyroid disease. Most patients have an insidious onset of pain and stiffness. Most patients demonstrate a gradual decrease in pain and return of motion over time. There may be improvement for up to 24 months. Treatment consists of gentle physical therapy, antiinflammatory medication, and occasional use of cortisone injections intraarticularly and subacromially. If the patient does not respond after an extended trial of therapy, consideration may be given to manipulation under anesthesia. More recently, arthroscopic release and debridement have been proposed.153 Open surgical release is rarely indicated and may in fact worsen the problem. Ozaki et al,117 however, reported on 17 patients treated surgically for recalcitrant adhesive capsulitis. These patients showed significant contracture of the coracohumeral ligament and rotator interval. Resection of these structures relieved pain and restored motion.
excellent pain relief with total-shoulder arthroplasty.51,152 Reverse-type prostheses are reserved for the elderly person with severely debilitating cuff tear arthropathy or loss of the coracoacromial arch. However, early reports are fraught with a high complication rate, and its implementation is still being defined.83
DEGENERATIVE JOINT DISEASE OF THE SHOULDER
REFERENCES
CONCLUSION In attempting to treat the myriad of shoulder problems, the orthopedist must first make an accurate diagnosis. The goals of treatment include controlling symptoms, improving function, and preventing recurrence, if possible. A systematic approach to management includes appropriate conservative modalities and surgical intervention, if necessary. Future concerns must address cost-effectiveness, standards of care, and outcome research.
1.
Degenerative joint disease of the shoulder can occur secondary to a number of different underlying pathologic conditions. The glenohumeral joint requires prosthetic replacement less often than other major joints. Osteoarthritis of the glenohumeral joint is uncommon, and patients with rheumatoid arthritis can most often be managed nonoperatively with regard to the shoulder. Degenerative joint disease may develop after fracture of the proximal humerus and subsequently require treatment. In rare cases, proximal humerus fractures may necessitate prosthetic replacement. Any of the aforementioned pathologic entities may be an indication for shoulder replacement. It is, however, most useful for diseases in which the proximal humeral subchondral bone has become distorted and the articular surface destroyed resulting in painful decreased motion. All patients should pursue a nonoperative course of management initially. Should symptoms persist or progress symptomatically, surgical intervention can be contemplated. Although shoulder prosthetic systems have improved, the patient may be a candidate for arthrodesis. This can be considered in a younger active patient with degenerative arthritis, joint sepsis, or loss of deltoid and rotator cuff function or as a salvage procedure after failed total-joint arthroplasty. The humeral component is designed to preserve metaphyseal bone stock and provide adequate fixation. The glenoid component is often not required, particularly if the rotator cuff is intact or repairable. Hemiarthroplasty is usually considered in younger patients with osteoarthritis, posttraumatic conditions without glenoid loss, rotator cuff pathology, or osteonecrosis. In many patients with more extensive osteoarthritis and rheumatoid arthritis involvement, glenoid resurfacing has improved pain relief. The glenoid most commonly is cemented into position. In younger patients with good bone stock, consideration is given to uncemented glenoid fixation with bone ingrowth. Results of survivorship analysis predicted a 27% failure rate.23 Other studies reported
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
15.
16. 17. 18. 19. 20. 21. 22.
Aamouth GM, O’Phelan EH: Recurrent anterior dislocation of the shoulder: a review of 40 athletes treated by subscapularis transfer (modified Magnusson-Stack procedure). Am J Sports Med 5:188-190, 1977. Akermak C, et al: Results of the Bristow repair: sports participation after surgery. In I Bayley, L Kessel, eds: Shoulder surgery. Berlin, 1982, Springer-Verlag, pp. 92-94. Allman F, et al: Symposium on sports injuries to the shoulder. Contemp Surg 7(3):70-109, 1975. Altchek DW, Skyhar MJ, Warren RF: Shoulder arthroscopy for shoulder instability. Instr Course Lect 36:187-198, 1989. Altchek DW, Warren RF, Skyhar MJ, Ortiz G: T-plasty anterior repair for anterior and inferior instability of the shoulder. J Bone Joint Surg 73A:105-111, 1991. Altchek DW, Warren RF, Wickiewicz TL: Arthroscopic labral debridement. A three year follow-up study. Am J Sports Med 20:702-706, 1992. Andrews JR, Broussard TS, Carson WG: Arthroscopy of the shoulder in management of partial tears of the rotator cuff: a preliminary report. Arthroscopy 1(2):117-122, 1985. Andrews JR, Carson WG: The arthroscopic treatment of glenoid labrum tears in the throwing athlete. Orthop Trans 8:44, 1984. Andrews JR, Carson WG Jr, Mcleod WD: Glenoid labrum tears related to the long head of the biceps. Am J Sports Med 13:337-341, 1985. Artz T, Huffer JM: A major complication of the modified Bristow procedure for recurrent dislocation of the shoulder. J Bone Joint Surg 54A:1293-1296, 1972. Aston JW, Gregory CF: Dislocation of the shoulder with significant fracture of the glenoid. J Bone Joint Surg 55A:1531-1533, 1973. Bach BR, OBrien SS, Warren RF, Leighton M: An unusual neurological complication of the Bristow procedure: a case report. J Bone Joint Surg 70A:458-460, 1988. Bankart ASB: The pathology and treatment of recurrent dislocation of the shoulder joint. Br J Surg 26:23-29, 1938. Barry TP, Lombardo SJ, Kerlan RK, Jobe FW, Carter VS, Shields CL, Yocum LA, Tibone JE: The coracoid transfer for recurrent anterior instability of the shoulder in the adolescent. J Bone Joint Surg 67A:383-386, 1985. Bigliani LU, McCann PD, Dalsey RM: An anatomic study of the suprascapular nerve. Presented at the annual meeting of the American Shoulder and Elbow Surgeons, Las Vegas, February 12, 1989. Bigliani LU, Cordasco FA, McIlveen SJ, Musso ES: Operative repair of massive rotator cuff tears: long term results. J Shoulder Elbow Surg 1(3):120-130, 1992. Bigliani LU, Morrison DS, April EW: The morphology of the acromion and its relationship to rotator cuff tears. Orthop Trans 10:216, 1986. Blackburn TA, et al: EMG analysis of posterior rotator cuff exercises. J Natl Athl Train Assoc 25:40-45, 1990. Blom S, Dahlback L: Nerve injuries in dislocation of the shoulder joint and fractures of the neck of the humerus. Acta Chir Scand 136:461-466, 1970. Boyd HB, Hunt HL: Recurrent dislocation of the shoulder. The staple capsulorrhaphy. J Bone Joint Surg 47A:1514-1520, 1965. Braley WG, Tullos HS: A modification of the Bristow procedure for recurrent dislocation of the shoulder. Am J Sports Med 13(2):81-86, 1985. Brav EA: An evaluation of the Putti-Platt reconstruction procedure for recurrent dislocation of the shoulder. J Bone Joint Surg 37A:731-741, 1955.
191
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192
23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41.
42. 43. 44.
45.
46.
47. 48. 49. 50.
51.
52. 53. 54.
55. 56. 57.
●
Treatment of shoulder disorders
Brenner BC, Ferlic DC, Clayton ML, Dennis DL: Survivorship of unconstrained total shoulder arthroplasty. J Bone Joint Surg 71A:1289-1296, 1989. Brown JE: Sternoclavicular dislocation. Am J Orthop 3:134, 1961. Buess E, Steuber KU, Waibl B: Open versus arthroscopic rotator cuff repair: a comparative view of 96 cases. Arthroscopy 21(5):597-604, 2005. Burkhart SS: Arthroscopic treatment of massive rotator cuff tears. Clin Orthop 267:45-56, 1991. Burkhead WZ, Rockwoood CA Jr: Treatment of instability of the shoulder with an exercise program. J Bone Joint Surg 74A:890-896, 1992. Cain PR, Mutschler TA, Fu FH, Lee SK: Anterior stability of the glenohumeral joint: a dynamic model. Am J Sport Med 15:144-148, 1987. Cameron JC, Hall M, Courtney BC: The Bristow procedure for recurrent anterior dislocation of the shoulder. J Bone Joint Surg 67B:327, 1985. Carol EJ, Falke LM, Kortmann JHJPM: Bristow-Latarjet the repair for recurrent anterior shoulder instability: an eight year study. Neth J Surg 37(4):109-111, 1985. Caspary RB: Arthroscopic reconstruction for anterior shoulder instability. Techn Orthop 3(1):59-66, 1988. Codman EA: The shoulder: rupture of the supraspinatus tendon and other lesions about the subacromial bursa. Brooklyn, NY, 1934, G Miller & Co, Medical Publishers. Cofield RH: Rotator cuff disease of the shoulder. J Bone Joint Surg 67A(6):974-979, 1985. Cofield RH: Subscapular muscle transposition for repair of chronic rotator cuff tears. Surg Gynecol Obstet 154:667, 1982. Cofield RH, Kavanaugh BF, Frassica FJ: Anterior shoulder instability. Instr Course Lect 34:210-227, 1985. Cole BJ, Warner JJ: Arthroscopic versus open Bankart repair for traumatic anterior shoulder instability. Clin Sports Med 19(1):19-48, 2000. Cooper RA, Brems JJ: The inferior capsular shift for multidirectional instability of the shoulder. J Bone Joint Surg 74A:1516-1521, 1992. Craig EV: The posterior mechanism of acute anterior shoulder dislocations. Clin Orthop 190:212-216, 1984. Curr JF: Rupture of the axillary artery complication dislocation of the shoulder. J Bone Joint Surg 52B:313-317, 1970. Detrisac DA, Johnson LL: Arthroscopic shoulder anatomy: pathologic and surgical implications. Thorofare, NJ, 1986, Slack. deWaal D, Melefijt J, Ooms AJ, van Rens TJ: A comparison of the results of the Bristow-Latarjet procedure and the Bankart/Putti-Platt operation for recurrent anterior dislocation of the shoulder. Acta Orthop Belg 51:831-842, 1985. DuToit GT, Roux D: Recurrent dislocation of the shoulder. A 24 year study of the Johannesburg stapling operation. J Bone Joint Surg 38A:1-12, 1956. Ellman H: Arthroscopic subacromial decompression: analysis of one-to-three year results. Arthroscopy 3(3):173-181, 1987. Fabbriciani C, Milano G, Demontis A, Fadda S, Ziranu F, Mulas PD: Arthroscopic versus open treatment of Bankart lesion of the shoulder: a prospective randomized study. JBJS Am 86A(11):2574, 2004. Fankhauser F, Boldin C, Schippinger G, Haunschmid C, Szyszkowitz R: A new locking plate for unstable fractures of the proximal humerus. Clin Orthop Relat Res 430:176-181, 2005. Fee JJ, McAvoy JM, Dainko EA: Pseudoaneurysm of the axillary artery following a modified Bristow operation: report of a case and review. J Cardovasc Surg 19:65-68, 1978. Ferlic DC, DiGiovine NM: A long-term retrospective study of the modified Bristow procedure. Am J Sports Med 16:469-474, 1988. Flatow EL, Bigliani LU, April EW: An anatomic study of the musculocutaneous nerve and its relationship to the coracoid process. Clin Orthop 244:166-171, 1989. Foster CR: Multidirectional instability of the shoulder in the athlete. Clin Sports Med 2(2):355-367, 1983. Freedman KB, Smith AP, Romeo AA, Cole BJ, Bach BR Jr: Open Bankart repair versus arthroscopic repair with transglenoid sutures or bioabsorbable tacks for recurrent anterior instability of the shoulder: a meta-analysis. AJSM Epub 32(6):1520-1527, 2004. Friedman RJ, Thornhill TS, Thomas WH, Sledge CB: Non-constrained total shoulder replacement in patients who have rheumatoid arthritis and class-IV fractures. J Bone Joint Surg 71A:494-498, 1989. Fronek J, Warren RF, Bowen M: Posterior subluxation of the glenohumeral joint. J Bone Joint Surg 71A:205-216, 1989. Gerber C: Latissimus dorsi transfer for treatment of irreparable tear of the rotator cuff. Clin Orthop 275:152-160, 1992. Gerber C, Ganz R: Clinical assessment of instability of the shoulder: with special reference to anterior and posterior drawer tests. J Bone Joint Surg 66B:551-556, 1984. Gerber C, Vinh TS, Hertel R, Hess CW: Latissimus dorsi transfer for the treatment of massive tears of the rotator cuff. Clin Orthop 232:51-61, 1988. Gross MR: Arthroscopic shoulder capsulorrhaphy: does it work? Am J Sports Med 17:495-500, 1989. Halley DK, Olix ML: A review of the Bristow operation of recurrent anterior shoulder dislocation in athletes. Clin Orthop 106:175-179, 1975.
58. 59.
60. 61. 62. 63. 64. 65. 66. 67.
68.
69.
70. 71. 72. 73. 74.
75. 76. 77. 78. 79.
80. 81. 82. 83. 84.
85. 86.
87. 88. 89. 90. 91. 92.
Harrison WE Jr, Sisler J: Reconstruction of the AC joint using a synthetic fascial graft. J Bone Joint Surg 56A:1313, 1974. Harryman DT, Mack LA, Wang KY, Jackins SE, Richardson ML, Matsen FA: Repairs of the rotator cuff. Correlation of functional results with integrity of the cuff. JBJS Am 73A(7):982-989, 1991. Hawkins RJ: Unrecognized dislocation of the shoulder. Instr Course Lect 34:258-263, 1985. Hawkins RJ, Angelo RC: Glenohumeral osteoarthrosis. A late complication of the Putti-Platt repair. J Bone Joint Surg 72A:1193-1197, 1990. Hawkins RJ, Bell RH, Hawkins RH, Koppert GJ: Anterior dislocation of the shoulder in the older patient. Clin Orthop 206:192-195, 1986. Hawkins RH, Hawkins RJ: Failed anterior reconstruction for shoulder instability. J Bone Joint Surg 67B:709-714, 1985. Hawkins RJ, Kennedy VC: Impingement syndrome in athletes. Am J Sports Med 6:151-158, 1981. Hawkins RJ, Koppert G: The natural history following anterior dislocation of the shoulder in the older patient. J Bone Joint Surg 64B:255, 1982. Helfet AJ: Coracoid transplantation for recurring dislocation of the shoulder. J Bone Joint Surg 40B:198-202, 1958. Hovelius L, Akepmark, Albrektsson B, Berg E, Korner L, Lundberg B: Bristow-Latarjet procedure for recurrent anterior shoulder subluxation and dislocation. Am J Sports Med 9:283-287, 1981. Hoveluis L, Gavle JJ, Frein LH: Recurrent anterior dislocation of the shoulder: results after Bankart and Putti-Platt operation. J Bone Joint Surg 61A:566-569, 1979. Hovelius L, Korner L, Lundberg B, Akermark C, Herberts P, Wredmark T, Berg E: The coracoid transfer for recurrent anterior dislocation about the shoulder. J Bone Joint Surg 65A:926-934, 1983. Inman VT, Saunders JB, Abbott LC: Observations on the function of the shoulder joint. J Bone Joint Surg 26:1-30, 1944. Irrgang JJ, Whitney SL, Harner CD: Nonoperative treatment of rotator cuff injuries in throwing athletes. J Sport Rehab 1:197-222, 1992. Jobe FW, Glousman RE: Anterior capsulolabral reconstruction. In JE Tibone, ed: Techniques in orthopedics. Frederick, MD, 1989, Aspen Publications, pp. 29-35. Johnson EW Sr, Collins HR: Nonunion of the clavicle. Arch Surg 87:963, 1963. Johnson LL: Arthroscopic management for shoulder instability: stapling. Presented at the annual meeting of the Arthroscopic Association of North America, Atlanta, February 1988. Jupiter J, Leffert RD: Non-union of the clavicle. Associated complications and surgical management. J Bone Joint Surg 69A(5):753-760, 1987. Kim SH, Ha KI, Kim SH: Bankart repair in traumatic anterior shoulder instability: open versus arthroscopic technique. Arthroscopy 18(7):755-763, 2002. Kinnet JG, Warren RF, Jacobs B: Recurrent dislocation of the shoulder after age fifty. Clin Orthop 149:164-168, 1980. Kowalkowski A, Wallace WA: Close percutaneous K-wire stabilization for displaced fractures of the surgical neck of the humerus. Injury 2:209-212, 1990. Kristiansen B, Angermann P, Larsen TK: Functional results following fractures of the proximal humerus: a controlled clinical study comparing two periods of immobilization. Arch Orthop Trauma Surg 108:339-341, 1989. Kummel BM: Fractures of the glenoid causing chronic dislocation of the shoulder. Clin Orthop 69:189, 1970. Kunkel SS, Hawkins RJ: Rotator-cuff repair utilizing a trough in bone. Techn Orthop 3(4):51-57, 1989. Latarjet M: A propos du traitment des luxations recidivantes de s’epaule. Lyon Clin 49:994-997, 1954. Laudicina L, D’Ambrosia R: Management of irreparable rotator cuff tears and glenohumeral arthritis. Orthopedics 28(4):382-388, 2005. Leach RE, Corbett M, Schepsis A, Stockel J: Results of a modified Putti-Platt operation for recurrent shoulder dislocation and subluxation. Clin Orthop 164:20-25, 1982. Lombardo SJ: The modifed Bristow-Laterjet procedure. Techn Orthop 3(4):12-22, 1989. Lombardo SJ, Kerlan RK, Jobe FW, Carter VS, Blazina ME, Shields CL: The modified Bristow procedure for recurrent dislocation of the shoulder. J Bone Joint Surg 58A:256-261, 1976. Loomer R, Fraser J: A modified Bankart procedure for recurrent anterior-inferior shoulder instability. A preliminary report. Am J Sports Med 17:374-379, 1989. Mackenzie DB: The treatment of recurrent anterior shoulder dislocation by the modified Bristow-Laterjet procedure. S Afr Sports Med J 65:325-330, 1984. Mackenzie DB: The Bristow-Helfet operation for anterior recurrent dislocation of the shoulder. J Bone Joint Surg 62B:273-274, 1980. Matsen FA III, Zuckerman JD: Anterior glenohumeral instability. Clin Sports Med 2(2):319-338, 1983. McCallister WV, Parsons IM, Titelman RM, Matsen FA: Open rotator cuff repair without acromioplasty. JBJS Am 87A(6):1278-1283, 2005. McLaughlin HL: Dislocation of the shoulder with tuberosity fracture. Surg Clin North Am 43:1615, 1963.
Chapter 5d
93. McLaughlin HL: Injuries about the shoulder and arm. In HC McLaughlin, ed: Trauma. Philadelphia, 1959, WB Saunders, pp. 233-296. 94. McLaughlin HL, Cavallaro WV: Primary anterior dislocation of the shoulder. Am J Surg 80:615-620, 1950. 95. McLaughlin HL, MacLellan DI: Recurrent anterior dislocation of the shoulder. A comparative study. J Trauma 2:191-201, 1967. 96. Mead NC: Bristow procedure. Letter presented at the Spectator Society, July 9, 1964. 97. Miller LS, Donahue JR, Good RP, Staerk AJ: The Magnuson-Stack procedure for recurrent glenohumeral dislocation. Am J Sports Med 12:133-137, 1984. 98. Mohtadi NG, Bitar IJ, Sasyniuk TM, Hollinshead RM, Harper WP: Arthroscopic versus open repair for traumatic anterior shoulder instability: a meta-analysis. Arthroscopy 21(6):652-658, 2005. 99. Morgan CD: Arthroscopic Bankart suture repair—2 to 5 year results. Presented at the annual meeting of the American Shoulder and Elbow Surgeons, Las Vegas, February 12, 1989. 100. Morgan CD, Bodenstab AB: Arthroscopic Bankart suture repair: technique and early results. Arthroscopy 3(2):111-122, 1987. 101. Morrey BF, Janes JM: Recurrent anterior dislocation of the shoulder: long-term follow-up of the Putti-Platt and Bankart procedure. J Bone Joint Surg 58A:252-257, 1976. 102. Moseley HF: Ruptures of the rotator cuff. Springfield, IL, 1952, Charles C Thomas. 103. Moseley HF, Goldie I: The arterial pattern of the rotator cuff of the shoulder. J Bone Joint Surg 45B(4):780-789, 1963. 104. Motycka T, Lahner A, Landsiedl F: Comparison of debridement versus suture in large rotator cuff tears: long-term study of 64 shoulders. Arch Orthop Trauma Surg Epub 124(10):654-658, 2004. 105. Mumford EB: Acromioclavicular diagnosis-a new operative treatment. J Bone Joint Surg 23:799-802, 1941. 106. Neer CS: Anterior acromioplasty for the chronic impingement syndrome in the shoulder. J Bone Joint Surg 54A(1):41-50, 1972. 107. Neer CS: Fractures of the distal third of the clavicle. Clin Orthop 53:43, 1960. 108. Neer CS: Impingement lesions. Clin Orthop 173:70-77, 1983. 109. Neer CS: Involuntary inferior and multidirectional instability of the shoulder: etiology, recognition, and treatment. Instr Course Lect 34:232-238, 1985. 110. Neer CS: Non-union of the clavicle. JAMA 172:1006-1011, 1960. 111. Neer CS, Craig EV, Fukuda H: Cuff-tear arthropathy. J Bone Joint Surg 65A:1232-1244, 1983. 112. Neer CS, Foster CR: Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. J Bone Joint Surg 62A:897-908, 1980. 113. Neviaser RJ, Neviaser TJ, Neviaser JS: Concurrent rupture of rotator cuff and anterior dislocation of the shoulder in the older patient. J Bone Joint Surg 70A:1308-1311, 1988. 114. Nielson AB, Nielson K: The modified Bristow procedure for recurrent anterior dislocation of the shoulder. Results and complications. Acta Orthop Scand 53:229-232, 1982. 115. Norris T: Diagnostic techniques for shoulder instability. Instr Course Lect 34:239-257, 1985. 116. Osmond-Clark H: Habitual dislocation of the shoulder: the Putti-Platt operation. J Bone Joint Surg 30B:19-25, 1948. 117. Ozaki J, Nakagawa Y, Sakarai G, Tamai S: Recalcitrant chronic adhesive capsulitis of the shoulder. Role of contracture of the coracohumeral ligament and rotator interval in pathogenesis and treatment. J Bone Joint Surg 71A:1511-1515, 1989. 118. Perthes: Uber operation bei habitueller Schulterluxation. Deutsche Zeitschr Chir 85:199-277, 1906. 119. Pettersson G: Rupture of the tendon aponeurosis of the shoulder joint in anterior inferior dislocation. Acta Chir Scand 77(Suppl):1-184, 1942. 120. Poppen NK, Walker PS: Forces at the glenohumeral joint in abduction. Clin Orthop 135:165-170, 1978. 121. Protzman RR: Anterior instability of the shoulder. J Bone Joint Surg 62A:909-918, 1980. 122. Rathbun JB, MacNab I: The microvascular pattern of the rotator cuff. J Bone Joint Surg 52B:540-553, 1970. 123. Reeves B: Experiments on tensile strength of the anterior capsular structures of the shoulder in man. J Bone Joint Surg 50B:858-865, 1968. 124. Regan WD, Webster-Bogaert S, Hawkins RJ, Fowler PJ: Comparative functional analysis of the Bristow, Magnusson-Stack, and Putti-Platt procedures for recurrent dislocation of the shoulder. Am J Sports Med 17:42-48, 1989. 125. Richard RR, Hudson AR, Bertoia JT, Urbaniak JR, Waddell JP: Injury to the brachial plexus during Putti-Platt and Bristow procedure. A report of eight cases. Am J Sports Med 5:374-380, 1987. 126. Rookwood CA: Subluxation and dislocation about the shoulder. In CA Rockwood, DP Green, eds: Fractures in adults. Philadelphia, 1984, JB Lippincott, pp. 722-860. 127. Rockwood CA Jr: Subluxation of the shoulder: the classification, diagnosis and treatment. Orthrop Trans 4:306, 1979.
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References
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CHAPTER
5e
Workplace Adaptation for Shoulder Disorders Thomas J. Armstrong
This chapter is concerned with workplace adaptations for preventing work disability due to shoulder, neck, and elbow impairments. Disability occurs when work demands exceed worker capacities (Fig. 5e.1).3,9 Development of workplace adaptations requires information about both worker and job demands, which can then be compared to determine whether new or additional adaptations are required. Although population work capacity data can often be determined from published data and models, individual data must be obtained from a qualified health care provider. The health care provider plays an important role also in determining how successful intervention has been and whether additional job modifications are required. Development of workplace adaptations requires the affected worker, the health care provider, and the employer to work closely together. Although the concept of disability is straightforward, its determination of disability and the development of adaptations are more complex due to the multiple physical, behavioral, and social variables involved. It is possible unwittingly to declare a worker disabled who is not or to declare one able who is not. It may be found, for example, that a worker is disabled because of a shoulder impairment that restricts his or her reach capacity, but that worker might have learned to adapt the workplace by rearranging equipment or standing up to reach distant objects. Similarly, it may be found that a worker is able to reach all the necessary work objects but is disabled by inability to do the job for 8, 10, or 12 hours per day.
EXPOSURE-RESPONSE RELATIONSHIP It is necessary to understand in general and specific terms the relationship between work factors and conditions that affect fatigue and risk of musculoskeletal disorders (MSDs). This relationship is referred to as the exposure-response relationship.4,34,35 Figure 5e.2 shows a hypothetical exposure-response relationship with exposure on the horizontal axis and response on the vertical axis. A number of metrics have been proposed and used for describing exposure; some of these are described later in this section. Response is typically expressed as the prevalence of symptoms or conditions at a given time or as an incidence rate of cases over time. Exposure-response relationships typically exhibit a sigmoid relationship as exposure increases from low to high. The prevalence and incidence of MSDs at low exposures are referred to as the background level and may be due to personal or other nonwork factors. The prevalence and incidence may also vary from one sign, symptom, condition, and measurement method to another. Figure 5e.2 illustrates two examples: curve a shows a low background level and a high sensitivity to work factors and curve b shows a high background level and a low sensitivity to work factors. In the future, we will have sufficient data to specify job designs for given populations that will produce an acceptable level of risk. Until then, the exposure-response relationship still provides important insights for job designers. Exposure-response relationships are based on a series of biomechanical and physiologic mechanisms.4,34,35 Work activity entails exertion of the body to overcome the weight, resistance, and inertia of work objects. These forces produce moments about joints that must be counteracted by muscles. The position of the body and the external forces are exposure variables and the moment about the shoulder is a response variable. At a second level, the joint moments can be regarded an exposure variable, whereas the muscle force acts as a response variable. At a third level, muscle forces can be regarded as exposure variables and perceived exertion, discomfort, and fatigue as short-term
Modify job
Treat worker Yes
Determine job demands
Response
Disability
b
Evaluate worker Demands > capacities
a
Exposure No Successful adaptation Figure 5e.1 Basic process for accommodation of work populations or individual workers.
Figure 5e.2 General exposure-response relationship shows an increasing prevalence or incidence of pain, fatigue, or other musculoskeletal disorders with increasing frequency and duration of force and posture. Curve a illustrates a low background level and a high sensitivity to a given factor and curve b illustrates a high background level and low sensitivity to a given factor.
196
Chapter 5e
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Workplace adaptation for shoulder disorders
response variables. Chronic tissue injuries and corresponding symptoms can be regarded as long-term responses. These biomechanics and physiology relationships are supported by experimental, psychophysical, and epidemiologic studies.4,34,35
Law, when a worker reaches for an object, the muscles in the shoulder and elbow must produce sufficient moment forces of gravity on the arm, forearm, and hand (Fig. 5e.3). A work object in the hand requires additional muscle force. The load moment on the shoulder, Ms, can be calculated based on the size of the body parts and their weight13,36:
Biomechanics An important example of the exposure-response relationship is found in the shoulder, the examination of which provides useful tools for developing workplace adaptations. By Newton’s Third
Ms = cosθ1x1w1 + (cosθ1l1 + cosθ2x2)w2 + (cosθ1l1 + cosθ2l2 + cosθ3x3)(w3 + wobject) where l1, l2, l3 are lengths of the arm, forearm, and hand; θ1, θ2, θ3 are angles of the arm, forearm, and hand with respect to
Mtot W3 W1
W1
X1
X2
I1
A
Wobject
X3
I2
I3
q3 q1
q2
B Figure 5e.3 (A) The moment produced about the shoulder is equal to the sum of the moments produced by the arm, forearm, and hand. In addition, the weight of a work object such as a part or tool contributes to the shoulder moment. (B) The angles of the arm, forearm, and hand with respect to the horizontal are shown.
Chapter 5e
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Exposure-response relationship
Table 5e.1a Average body link sizes as fractions of total stature16
Table 5e.1c Body segment weights as percentages of total body mass15,29
Link
Link
Stature Floor-ankle Floor-knee Floor-hip Floor-shoulder Floor-elbow Floor-wrist Floor-hand Floor-buttocks Floor-eye Center-shoulder Shoulder-elbow Elbow-wrist Wrist-hand
Fraction 1.000 0.039 0.285 0.530 0.818 0.630 0.485 0.377 0.480 0.936 0.129 0.188 0.145 0.108
the horizontal; x1, x2, x3 are the moment arms between the proximal joint and the center of gravity of the arm, forearm, hand, and work object; and w1, wf2, w3, wobject correspond to the weights of the arm, forearm, hand, and work object. The moment arms can be measured for a given individual or estimated from height of a given population percentile using the relative link lengths shown in Table 5e.1a16 and the link center of gravity locations shown in Table 5e.1b.15,29 Weights of each segment can be estimated for a given individual or population percentile weight using the relative segment weight data shown in Table 5e.1c. Height and weight data for the U.S. adult population are shown in Table 5e.2. The calculated shoulder and elbow moments for persons with average female and male stature and weight performing a horizontal reach at elbow height and at shoulder height are shown in Figure 5e.4. Figure 5e.4, b, d, f, and h, shows how the moment about the shoulder due to the weight of the arm, forearm, and hand increases with the horizontal reach distance. Added to the weight of the arm, forearm, and hand, the moment of the weight of a held object such as a tool or part would equal the distance between the shoulder and hand times the weight. Holding a 10 N (2 pound) tool in the hand at a distance of 0.6 m, for example, would add 6 Nm to the 10 Nm of the arm and forearm. This simple biomechanical analysis can be applied to many work tasks. Figure 5e.4, for example, shows a 7-Nm shoulder load in the shoulder of an average female holding her hands over a keyboard at a distance of 0.5 m, with the moment proportionally
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Relative body mass
Head Arm Forearm Hand
6.9% 2.7% 1.6% 0.6%
higher for a worker with greater body weight. The biomechanical analysis provides both a qualitative and quantitative rationale for job design.
Important limitations Deliberately simplified for demonstration purposes, this analysis of shoulder stress generally underestimates the actual loads. Increased loads result from inertial forces associated with acceleration and deceleration of the body and work object. Additional loads may result also from antagonistic muscle forces. Although some antagonistic muscle contractions are inevitable, others may result from psychologic stresses,7 the contributions of which, although real, are difficult to quantify and beyond the scope of this discussion.
Other biomechanical considerations In addition to the effect on muscle workload, increasing shoulder angles produce pressure on internal and surrounding soft tissues.22 In fact, although the required muscle loads actually decrease as the arm torso arm angle exceeds 90 degrees, pressure on soft tissues continues to increase. Epidemiologic studies show that elevated elbow postures are associated with elevated incidences of chronic shoulder pain and impairment.6
Other body parts Similar analyses can be performed for other parts of the body, such as the neck.23 Bending the neck or torso forward to reach or see work objects such as documents, controls, or equipment produces load moments on the neck that must be counteracted by internal muscle forces. Extreme rotation of the forearms in combination with forceful exertions of the hands produces stress on the attachments of the finger flexor and extensor muscles. As a general rule, jobs should be designed so that workers do not have to perform sustained or repeated exertions at or near range of motion limits. Ideally, the elbows should be near the sides of the body, the forearms should not be rotated to one extreme or the other, and the head should be held upright. At the other extreme, the work pace should enable workers to periodically stretch and change positions. Even the best posture eventually becomes uncomfortable if it is maintained too long.
Table 5e.1b Body segment distance from proximal joint center of gravity15 Link Arm Forearm Hand
Center of gravity 43.6% 43.0% 50.6%
Localized fatigue Acceptable work design standards for preventing MSDs that may afflict the elbow, neck, and shoulder have not been established, but recommendations may be made for preventing localized fatigue. An important problem in its own right, localized
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Table 5e.2 Statures (m) and body masses (kg*) for males and females ages 18 and over from the National Center for Health Statistics11 Female
Stature Weight
Male
Average
5%
50%
95%
Average
5%
50%
95%
1.618 69.2
1.504 48.0
1.618 65.6
1.73 102.5
1.755 82.1
1.636 59.7
1.755 80.0
1.880 110.8
*1 N = kg × 9.8 m/s2.
fatigue may be a harbinger or precursor of more serious MSDs.34,35 According to the above exposure-response relationship, localized fatigue responses include concentrations of metabolic substrates, metabolites, and ions. These changes may result in altered electromyograms, reduced motor control, reduced strength, and, perhaps most importantly, pain. Exposures are expressed as percentages of maximum voluntary contraction (% MVC), exertion frequency, and duty cycle. The % MVCs are computed as the ratio of the required muscle force to that possible for a given task, individual, or population or as the ratio of job demands to worker capacities, as shown in Figure 5e.1. Recommended acceptable exposure limits for continuous work previously ranged from 0 to 15% MVC; those for intermittent work range from 17% to 21% MVC. Bystrom and Fransson-Hall10 recommended an upper limit of 10% MVC for continuous static work and 17% MVC for intermittent work. The above biomechanical analysis of the shoulder loads during reaching and lifting can be used to estimate relative muscle workload for a given task, but first it is necessary to consider worker capacity.
Worker capacity Acceptable workloads vary from group to group and person to person, and design commonly accommodates the general population or a specific individual. In the former case, work capacity data are typically taken as a lower percentile of the general population. It is all too common to design for a 5th percentile, a practice that seems to be reinforced by reference books showing the 5th percentile, average, and 90th percentile population data. The problem is that 5 people out of 100 may be disqualified or experience significant difficulty or injury doing the job. Design for an individual requires a function evaluation that specifies strength limits for that person. The designer should work closely with the evaluator during and after design implementation to make sure that the job can be performed without risk of injury or reinjury. For discussion purposes, data from Winters and Kleweno,40 shown in Figure 5e.5, indicate that female strength is about half that of male strength and that male strength is sensitive to shoulder posture. The average female strength of approximately 30 Nm is significantly less for an elderly or injured worker. Reaching results not only in increased load moments on the shoulder (Fig. 5e.4) but also in decreasing strength (Fig. 5e.5). Vertical reaching also reduces strength. Figure 5e.6 shows a job in which a female of average stature, proportions, and weight gets 10 N parts at a rate of 20 per minute from a rack at a distance of 0.625 m at shoulder height
and places the parts on a moving tray at a distance of 0.32 m. Because the trays are moving, the worker cannot rest her forearms while waiting for them to come into position. The shoulder moments due to the weight of the body and load are calculated in Table 5e.3 and are plotted in Figure 5e.6B. (Loads between successive positions are approximated as straight lines.) It can be seen that the moments increase due to the weight of the arms during the reach. The moment then increases as the part is lifted and then decreases as it is moved into position to wait for the tray to come into position. Finally, the load force decreases to zero as the load is released, but the shoulders must continue to support the weight of the body. The average total shoulder moment can be calculated as a time-weighted average: Ms =
( ∑ t i Mi ) ∑ ti
where Ms is the average shoulder moment, ti is the duration of the ith work element, and Mi is the average total moment produced during the ith element. For this sample task the average moment is calculated as = [0.67 × (4.5 + 9.8)/2 + 0.13 × 9.8 + 0.79 × (16.05 + 7.71)/2 + 2.00 × 7.71 + 0.36 × 7.71 + 0.07 × (7.71 + 4.5)/2]/4.0 = 8.4 Nm This analysis provides important insights into the factors that should be considered in evaluating and designing work stations. It is important to know the locations of controls and those where materials, parts, and tools are stored and used as well as the forces required to obtain, hold, and use work objects. The list of work elements and their durations33 are likewise all significant factors affecting the load on the shoulder and other parts of the body. As described earlier, loads on the body are frequently normalized as a fraction of maximum strength or percent of maximum voluntary contraction, % MVC, which is used commonly as a metric of physical workload and predictor of localized fatigue. Calculation of relative workload requires information about both the absolute load and the corresponding work strength. Strength varies among workers, joints and their relative positions, hands, ages, and occupational groups and may be affected by fatigue, injuries, and diseases. The analyst may select a value from the literature that corresponds to the population of interest or use data provided by a functional evaluation of a specific worker of interest. Based on an average strength of 30 Nm, the average relative workload for the worker described in Figure 5e.5 and Table 5e.3 would be 28% MVC. Joint loads can be estimated also from surface electromyography (EMG), which can be regarded as a response variable
–0.40 –0.20 0.00 – 0.05 – 0.10 – 0.15 – 0.20 – 0.25 – 0.30 – 0.35
0.00
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0.40
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Moment (Nm)
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0
14 12 10 8 6 4 2 0 –2 –4 –6
Shoulder moment (Nm) Shoulder angle (°)
– 20 – 40 – 60 – 80 –100 –120 –140 –160
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B
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14 Shoulder moment (Nm) Shoulder angle (°)
12
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C
0.00
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Moment (Nm)
10
– 20 – 40
8
– 60
6
– 80
4
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–2
–140 –160
–4 0.0
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Female 0 –10 – 20 – 30 – 40 – 50 – 60 –70 – 80 – 90 –100
14 Shoulder moment (Nm) Shoulder angle (°)
0.00 0.00 – 0.05 – 0.10 – 0.15 – 0.20 – 0.25 – 0.30 – 0.35
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12 10 8 6 4 2 0 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Distance (meters)
E
F
Male
Male 0 –10 – 20 – 30 – 40 – 50 – 60 –70 – 80 – 90 –100
14 Shoulder moment (Nm) Shoulder angle (°)
0.00 0.00 – 0.05 – 0.10 – 0.15 – 0.20 – 0.25 – 0.30 – 0.35
0.20
0.40
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0.80
Moment (Nm)
12 10 8 6 4 2 0 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Distance (meters)
G
Female
H
Female
Figure 5e.4 Calculated shoulder and elbow moments due to the weight of the arm, forearm, and hand for an average male and female performing a horizontal reach at elbow (A-D) and at shoulder (E-H) heights for females (C, D, G, H) and males (A, B, E, F).
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ANALYSIS OF JOB TASK DEMANDS
100
As stated at the beginning of this chapter and shown by the above discussion, information about task demands is necessary for disability evaluation and work adaptation design. Collecting job and worker information requires a systematic approach in two steps.
80
MS (N-m)
Males 60
Job task demands The first step documents what, where, when, and how the job is performed and includes the process, equipment, procedures, and environment.
40
20
Job documentation
Females
0 0
30
60
90
120
Figure 5e.5 Shoulder strength for four healthy young females and four healthy young males versus shoulder angle with elbows straight (triangles) and flexed 90 degrees (circles).
to external load.23,26,31 Generally, EMG methods are used to verify hypotheses developed using biomechanical analyses and psychophysical studies. Electrodes are attached over one or more of the muscles associated with the joint motion of interest and connected to appropriate preamplifiers, amplifiers, data loggers, and computers. The test can be normalized with respect to a maximum exertion or some other reference signal and provide a continuous real-time indication of muscle load. Further discussion of EMG methods is beyond the scope of this chapter.
A thorough documentation of the job helps to ensure a systematic analysis of all relevant factors and enables the analyst to identify those that contribute to stressful postures. Finding that the job involves exposures to extreme shoulder postures, for example, is insufficient without information explaining what actions like reaching for a part or operating a control produce those postures. This information enables the analyst to recommend possible interventions to reduce that stress. Evaluation of particular stresses, such as part weight and location, can be used to calculate the load moment on the shoulder.
Observations Documentation procedures may need to be adapted to the type of jobs being studied. In many settings, particularly manufacturing, the work is by design standardized to control work quality and production, but subtle differences from worker to worker may depend on their sizes, methods, and skill levels. A short worker, for example, may have to reach up and over, whereas a tall worker may have to reach down and under. One may choose
Shoulder (Nm)
20 Total (Nm) Load (Nm) Body (Nm)
15 10
Average
5 0 0
A
1
2 Time (s)
3
4
B
Figure 5e.6 (A) A worker reaching 0.625 m forward to get 10 N (2 pounds) parts from trays 0.320 m in front of her on a moving tray and a rate of 20 per minute. (B) The moment due to the weight of the body and work object are shown. Average total moment (body plus work object) is 8.4 Nm for the work cycle.
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Table 5e.3
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Analysis of Job Task Demands
201
Work elements, locations, and loads for a repetitive hand transfer task
Work element
Elapsed time
Hand location
Load weight
Moment load
Moment body
Total
Reach Grasp Move Wait Position Release
0.67 0.13 0.79 2.00 0.36 0.07
32.1→62.5 62.5 62.5→32.1 32.1 32.1 32.1
0 0 10 N 10 N 10 N 0
0 0 6.25→3.21 3.21 3.21 0
4.5→9.8 9.8 9.8→4.5 4.5 4.5 4.5
4.5→9.8 9.8 16.05→7.71 7.71 7.71 4.5
to walk around a pallet of parts, whereas another reaches across. Although one worker may be able to complete work promptly and take brief rest periods, another may have trouble keeping up and have no rest. How workers perform their jobs may change over time. In some cases, jobs contain multiple tasks, as though each was two or more jobs. The documentation should include identification of each task, its frequency, and its duration. Frequencies and duration may vary from day to day, so it is necessary to either observe the job over time as previously described or to ask the worker or supervisor to estimate the variation. An increasing trend to rotate workers among jobs occurs in many cases to maintain production schedules by cross-training them to deal efficiently with absenteeism and schedule changes. In other cases it is done to reduce exposure to highly demanding jobs. Generally, the analyst performs at least a cursory analysis of all the jobs the worker performs, particularly if he or she has had a musculoskeletal injury. It is common to manufacture different product models or even products on the same production line. In some cases the worker may have to hurry to perform all the required assembly operations without rest, whereas at other times they may be able to work quickly and rest frequently. Some jobs, such as maintenance, repair, and office work, have yet to achieve a high level of standardization and instead typically entail two or more tasks that may be performed at irregular intervals for variable periods. These multitask jobs may require considerably more time than a standardized singletask job. For the above reasons, observations should be repeated for several workers over time to assess job variations for those being studied. While interviewing workers, the analyst should anticipate this variability. Differences from one worker and one work station to the next often provide insights into how the job can be improved. The documentation can be performed from available job descriptions, time studies, workplace inspections and measurements, equipment specifications, and interviews with workers and supervisors. To facilitate cooperation of both the worker and employer, it is important that the job analysis minimizes disruption of work activities. Because the goal is to obtain information about how the job is performed under normal work conditions, minimal disruptions will help keep the worker from being distracted by the analyst. Available information may include job descriptions from the personnel department, standard work method descriptions, and
time analyses from industrial engineering or previous ergonomic assessments. Job descriptions from the personnel department tend to focus on skill requirements rather than on force and posture patterns. Work method and time descriptions can be quite useful because they usually describe the methods and time allocations. Combined with information about work objects and work stations often make it possible to predict loads and postures as described above. Because the job may have changed since the standard was developed, work method and time descriptions should always be verified with observations or interviews. Although in some cases an ergonomic job analysis has previously been performed, at present such analyses are not standardized. Unless the analyst has first-hand knowledge of the job and the methods used to analyze it, each job should be inspected to verify that all necessary information was included or that it has not changed.
Video recordings Still and video images have become integral parts of job analyses. Readily available low-cost digital and video cameras can now be used to collect images and transfer them into computers where they can be viewed and edited. Freeware, such as Apple Computers QuickTime™, can be used to play back digital films frame by frame, the most useful of which can be captured and pasted into report documents. A few simple steps will greatly improve the quality of the video data: (1) obtain permission from the worker and the employer, preferably in writing; (2) record several representative work cycles, both to allow the worker to get used to the camera and to observe variations; (3) take pictures from several angles (the view of one hand may be blocked by the body or other obstructions); and (4) use a tripod to improve video steadiness most efficiently and least expensively. Video cameras often can be set up and left to run unattended, even with intermittent pauses at specified intervals.24 If video recordings are not possible, the analyst may elect to make periodic tours of the workplace to observe and record personally. Intermittent observations of worker activities are referred to as “work sampling”; statistical procedures have been described for estimating confidence limits for the frequency that a task occurs.17,33 To get a confidence limit of a few percent, typically hundreds of samples are required, which may be beyond the scope of most studies. Statistical calculations are based on the assumption that the observations are randomized. Although generally there is sufficient variation in the work process to allow fixed interval sampling, the analyst should make sure that
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observations are not synchronized from any workplace activities that could bias the results.
Measurements of the work station and equipment Physical measurements of the work station often can be made before or after the shift or while the worker is on break. The employer may have engineering drawings that enable the analyst to determine key dimensions such as the height of the work surface and the location of parts, assemblies, and controls; otherwise, it will be necessary to determine these dimensions using a tape measure. In either case it is necessary to establish reference lines or planes for these measurements. The ideal reference plane for vertical measurements for a vertical worker, for example, is the floor. The ideal horizontal reference plane is a vertical plane that passes through the barrier separating the worker from the work object. For a seated worker, this is the front of the desk, whereas for a standing worker reaching into a bin of parts it is the edge of the bin. The reference plane for horizontal measurements should correspond to a barrier that restricts movement from side to side. For a worker seated in a fixed location, this may correspond to the sagittal plane of the body; if the worker is standing and free to step side to side, then measurements to either side may not be of critical importance, unless the worker is required to reach two objects with opposite hands at the same time.
Table 5e.4 Basic job documentation information can be obtained from existing job descriptions, interviews, observations, and physical measurements For the job Formal job title (in company documentation) Informal job title (among workers and supervisors at the work site) ● Work objectives (one or more reasons that the job exists) ● Job tasks (all worker duties that share a common purpose; tasks may or may not be separated in time and space) For each job task ● ●
● ● ● ●
● ●
Objective Tools and equipment (ID, size, weight) Materials and parts (ID, size, weight) Methods (step-by-step description in necessary detail of what the worker does to perform the task) Work station (sketched or described with key dimensions) Environment (location and conditions of job)
The second part of the analysis assesses the physical job stresses. As mentioned at the beginning of this chapter, exposure-response entails a cascading series of relationships.4 Job demands may be characterized as a force and posture profile, as a load moment profile for a joint such as the shoulder, as the muscle activity (measured in an EMG), or as a symptom such as localized discomfort.
same time or push and pull quickly, creating an inertial factor. Direct weight and breakaway force measurement may be a starting point, but often second- or third-level methods such as EMG or perceived exertions are also necessary. Joint angles between two adjacent body segments can be measured using goniometers, including manual devices that require the worker to stop while they are positioned over joints and electrical devices that can be attached to a data logger or computer for continuous posture recordings. Gerr et al20 described the use of manual goniometers for determining major body angles in computer users. Joint angles can also be estimated from direct observations of workers or indirect observations of photographs and movies. Observations are subject to observer and parallax errors.30 Parallax errors can be minimized by aligning the viewer with the axis of joint rotation. Often this is not possible; however, an experienced job analyst can often do an adequate job of mentally compensating for parallax errors. It is helpful to observe or record images from several views. Joint moments can be calculated from loads and body positions. Recall that moments are related to both the magnitude of the force and the distance between the force and the center of joint rotation. In some cases, it may be possible to stop the worker and measure distances using a tape measure. Sometimes distances can be estimated from dimensions of the work place. In other cases, they may be estimated from pictures. In some cases, the forces correspond to the weight of an object lifted; in others, they correspond to the force to hold or move one object against another. Then it is necessary to simulate the workers’ actions with a force gauge.
Measurement of posture and force
Surface EMG
Postures and forces can sometimes be measured directly using force gauges and goniometers. In the example shown in Figure 5e.6, the major forces are due to the weight of the work object and that of the upper limb. However, many cases are not this simple: The worker may lift, push, and pull, for example, at the
Surface EMG, in which electrodes are placed on the skin over the muscles of interest, is used most commonly for exposure and fatigue assessment. Electrodes are connected to preamplifiers, amplifiers, and some kind of recording device. The signals may be recorded by a portable memory device that the worker
Interviews Worker and supervisor interviews are important sources of information, the quality of which can be greatly improved with a few rules32: (1) explain the purpose of the interview, (2) list the key points to be covered, (3) avoid leading questions, (4) clarify by summarizing back to the interviewee, (5) do not let the interview wander into irrelevant areas, (6) protect the interviewee’s confidentiality, and (7) take careful notes or use an audio recording device. Interviews may be performed with one or more workers at a time. Questionnaires also can be used to obtain information from workers and supervisors, but development of a valid questionnaire to obtain desired information about a given job can be a major undertaking in its own right. Table 5e.4 is intended as a template for a job documentation data collection form that the user can modify to suit specific needs.
Physical job stresses
Chapter 5e
wears or by a digital computer. The worker may be tethered to the computer by wires or connected via radio transmitter. Because EMG values may change very quickly, it is necessary to record signals over several representative cycles at high frequencies. The volumes of data generally dictate the use of a computer and appropriate software for analysis. Jonsson26 and Mathiassen and Winkel31 described procedures summarizing force patterns using EMG data that indicate rest/recovery time versus work time. The investigator must be familiar with human anatomy and with the operation (including calibration) of the equipment to obtain meaningful results. An important quality of EMG is that it provides information about a specific body part under real work conditions by a real worker; a limitation is that an EMG provides information about only a very small part of the body. In some cases additional channels can be used to monitor multiple muscle groups simultaneously, but this may be too cumbersome and disruptive in many work situations. Some EMG measurements can be performed on a subject simulating some part of or the entire job in a laboratory. Although an important tool, EMG is an advanced technique for use after observations and simulations have documented the job and identified the specific muscle groups. A number of commercial EMG systems are now available and easy to find on the Internet; the user is cautioned, however, to understand clearly where and how the test will be used and to have adequate technical support.
Psychophysical responses Joint loads can be assessed also using perceived exertion,8,23 which is affected by localized fatigue. Most commonly it is measured using a Borg scale of relative perceived exertion (Fig. 5e.7B), but it may be assessed using visual analog scales also shown in Figure 5e.7C. On average both work equally well, but some prefer the Borg scale while others prefer the visual analog scale.39 One of the important and useful features of perceived exertion
2
0 1
6
10
3
7
11 12 13
4 5
8 9
14
15
16
17
A
Very uncomfortable work
0 0.5 1 2 3 4 5 6 7 8 9 10
Nothing at all Very, very easy Very easy Easy Moderately hard Somewhat hard Hard Very hard Very, very hard
B
Very comfortable work
C Figure 5e.7 Local discomfort patterns can be mapped by asking the worker to indicate areas on a body part map as shown in A. Localized and overall discomfort and effort can be quantified using the modified Borg scale shown in B or a visual analog scale shown in C.
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Analysis of Job Task Demands
is that it can be measured simultaneously for different parts of the body.14 Regional body discomfort patterns can be compared with workload patterns and with underlying impairments. Saldana et al37 described the use of a computer program to evaluate discomfort patterns in rural letter carriers. Readily applicable to other types of work, this method is particularly well suited for studying office workers who regularly use a computer. Studies by Ulin et al39 showed that perceived exertion associated with the use of a pneumatic hand tool increases with work distance from the body and with increasing elevation above the shoulder and decreasing elevation below the elbow. Krawczyk et al27 showed similar results for the hand transfer tasks. With repeated or sustained exertions, the worker may begin to experience discomfort. With exertions performed over longer periods such as days, weeks, or years, the worker may experience chronic symptoms. The Nordic Health Questionnaire provides a standardized instrument for collecting work symptom data.28 Saldana et al37 demonstrated how a computer could be used to collect worker symptom data and how these data correspond with work patterns. Symptom data are easy to collect and require minimum equipment; the data may be highly variable from one worker to the next, however, and care is required to avoid bias.
Event-based versus time-based observations The analysis may be “event based” with observations recorded only when an event of interest occurs, such as when a worker reaches for or uses a work object. Joint loads are plotted as a function of time in Figure 5e.6, but because the times correspond with the worker’s reaching for parts, it is an event-based analysis. The definition of events is arbitrary: They may correspond to specific work elements as shown in Figure 5e.6, with only selected work elements, or with the use of certain tools. The example shown in Figure 5e.6 is an event-based analysis in which the events are work elements and straight-line extrapolations are used between successive events. The selection of events is determined by the job documentation and the goals of the analysis. The analysis may also be “time based” in that the forces and postures are observed continuously or at specific time intervals. The corresponding events are then examined to identify the work factors that cause the extreme force or posture. Forces and postures may be estimated from observations, measured directly using force gauges and goniometers, or predicted by biomechanical models and insights. The work sampling method described above is a time-based analysis of activities, but it could be combined with force and posture measurements.
Prediction of posture and forces Figure 5e.4 shows how link data can be used to estimate postures and forces of males and females of given percentiles at selected locations. In many cases, the analyst may mentally extrapolate based on observations and experience. When a tall worker is seen reaching overhead for a part, for example, it becomes obvious that a short worker or one with limited mobility will be even more challenged to perform the same task. The analyst may want to report not only what was observed, but what might be observed for another worker. The moments about the shoulder and elbow can be computed using the methods described above if additional quantification is desired. These values can be used to predict and compare
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worker endurance at the observed versus modified work stations. Many third-party biomechanical models available for purchase or for download as shareware or freeware can be used to facilitate analysis of loads on the entire body or on selected body parts. One commercially available product is the University of Michigan Three-Dimensional Static Strength Prediction Program.13 This program enables the user to enter information about the location and direction of the load, at which the model calculates moments and populations for percentiles at each major joint. The user also can directly enter body part sizes and positions for a given problem.
WORKPLACE ADAPTATION The preceding discussion indicates that workplace adaptations entail reducing load moments by rearranging work objects and eliminating stressful postures, reducing forces themselves, or reducing the time that forces must be exerted. Such adaptations include rearrangement of work space layout and use of lighter tools or materials, mechanical assistance, and/or body supports.
Placement of work objects Ideally, work objects such as materials, parts, tools, assemblies, controls, and data input devices should be placed as close to the worker as possible at or near elbow height. Aforementioned studies by Ulin et al39 found that some workers prefer to use tools slightly above elbow height, which may provide better visibility, whereas others prefer them slightly below, which may enable them to lean into the task at hand. Similarly, Sauter et al38 and Grandjean et al21 showed that most keyboard users prefer positioning conventional keyboards at or near elbow heights, but some prefer it slightly higher or lower. Personal preferences vary significantly from person to person. As shown in Table 5e.2, worker size varies significantly between and within gender groups. Individual preferences also vary among workers of the same size and for the same worker over the course of the day; even the best position eventually becomes uncomfortable. Because one-size work station will not fit everyone, it is very important for each worker to be able to adjust the work station to his or her own preference. Achieving this flexibility begins with designing equipment in ways that make such adjustments easy and convenient. If a mechanic must come to raise or lower a keyboard, the adjustment probably will not occur as often as needed. Workers must be trained and encouraged to adjust their work stations, with periodic inspections to make sure that they are doing so. A worker’s failure to adjust a work station upon inspection may not mean a discipline problem but rather a lack of training or time, an adjustment for temporary stretch break, or equipment that is difficult or unsuitable to adjust. It is important to discuss these issues with the worker. Although it is usually desirable to locate work objects close to the worker, it is not always possible. In many cases the job may entail work on large equipment, parts from multiple sources, or use of several tools and controls. Work station design begins with a thorough knowledge of the work objective, tools, materials, and methods as well as worker size and strength, as shown in
Tables 5e.1a, 5e.2, and 5e.4. Together this information can be used to map worker reach capabilities or envelopes and to calculate load moments, as shown in Table 5e.3.
Anthropometric considerations Figure 5e.8 shows maximum reach envelopes for 5th percentile female and 95th percentile male statures on horizontal work surfaces. In one case the arm is outstretched at shoulder height, and in the second case the shoulder is constrained to -60 degrees (Re. horizontal). There is nothing sacred about the 5th and 95th percentiles; universal designs that accommodate all possible users are preferable. As a practical matter the selection of design benchmarks is based on costs and benefits, although the cost of potential litigation can favor inclusion of more users in an analysis and design. In either case, it is still necessary to have information about the size of the potential work population or a specific individual to be accommodated. It is also possible to estimate the effective work area subject to desired posture constraints. The effective work area for the small female shown in Figure 5e.8d, for example, is approximately 0.48 m2. Based on a straight hand, this calculation disregards any intrusion of the body into the work space. As a practical matter, the area should be reduced a minimum of 8% for a relatively lean body. The reach distance and area would be further reduced if the worker must hold an object like a mouse or a power tool. Reducing the reach distance by one-half hand length to allow for gripping would reduce the effective work area by 24% from 0.48 to 0.36 m2. Adjusting for the incursion of the body into the work area further reduces the work area to 0.32 m2. Of course the worker can reach farther, but it would be at the expense of increased shoulder and/or back flexion. Although reasonable for short periods, such increased flexion may be unsatisfactory for prolonged or sustained work. Objects that are used continuously or frequently should have first priority for this space. For a data entry job, for example, these would be the keyboard, mouse, and source documents. Objects used less frequently such as a telephone, the computer CPU, or stored reference documents may be placed at the outer limits of the reach envelope. A typical keyboard requires 0.1 m2 of space, a mouse another 0.1 m space, and a standard 8.5 × 11-inch document another 0.6 m2, totaling 0.26 m2 of the available 0.32 m. The areas required for the keyboard, mouse, and documents, however, are not contiguous, and workers generally position them in a way that conforms with their body positions. As a result the 0.32 m2 will be more than used up. The required space can sometimes be reduced by selecting alternative equipment. A track ball or touch pad, for example, would reduce the mouse area to less than 0.01 m2. Unless the worker uses the numeric keypad, a shorter keyboard might be substituted. By holding a document on an incline, a stand or holder can reduce its footprint. With the many choices of computer input devices and work stations that are now available, the feasibility of these adaptations of course depends on job demands and individual capacities. Additional anthropometric guidelines for design of computer work stations have been published by the Human Factors and Ergonomics Society.25
Chapter 5e
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Figure 5e.8 Reach envelopes computed according to National Health Survey Data of stature and relative link length data reported by Drillis and Continni.16 (A and B) Side views of someone with 5% female stature and average body proportions with an arm outstretched at shoulder height and the shoulder constrained to −60 degrees (Re. horizontal). Restricting shoulder flexion to −60 degrees reduces reach distance by 21% from 0.66 to 0.52 m and elbow height from 1.23 to 0.99 m. (C and D) Top views of the elbow height reach envelopes for the 5 percentile females with and without shoulder constraints. (E and F) Top views of the elbow height reach envelopes for the 95 percentile males with and without shoulder constraint. For the large male, restricting shoulder flexion reduces reach distance by 22% from 0.83 to 0.65 m and reduces elbow height from 1.54 to 1.23 m.
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The above calculations were based on standard percentiles. Similar calculations can be performed based on link length estimates for an individual by using the link length fractions reported by Drillis and Contini16 and displayed in Table 5e.1a or those reported by Dempster15 and others.13,29 Minimizing the reach distance helps to minimize the load on the shoulder. Work that requires continuous visual feedback may result in prolonged neck flexion, however, requiring a tradeoff between loads on the shoulder and neck. The solution depends on the task. Most experienced keyboard users, for example, can work without watching their hands; however, documents laid flat on the work surface require the worker to look down. In many cases this problem can be solved with a document holder. It is not uncommon, particularly in medical billing, for the source documents to contain many pages that are bound together and may require a custom holder. In some cases, like fine assembly and dental work, it is necessary to bring the work in line with the eyes, often by providing arm and body supports. The traditional assembly line presents some special design challenges because it is often in continuous motion and difficult to make work stations individually adjustable (Fig. 5e.9a). Also, the worker often must reach over a structure along the sides of assembly line. Space is required not only for the line itself, but also for parts containers and tools. Parts may be stacked in front of, beside, or behind the worker, whereas tools may be suspended overhead or mounted or laid along the side of the line. There have been many improvements in manufacturing methods over the last 30 years that help to address these issues. Lean manufacturing discourages large inventories of parts that fill up the work space and increase reach requirements (Fig. 5e.9b). There is increasing emphasis on kitting of parts so that only those needed for a specific assembly are delivered to the work
site at the time required. In addition to reducing inventory costs, these methods also reduce reaching.
Tool weight control Loads can also be reduced by decreasing the weight of work objects by using lighter tools, for example. Armstrong et al2 found that workers consistently rated hand tools weighing more than 18 N as “too heavy.” The weight of a work object may otherwise be an asset; for example, the weight of a power tool for driving threaded fasteners or for sanding or buffing may reduce the force required. Of course, this is true only with horizontal surfaces, when the worker is driving threaded fasteners down or sanding or polishing the top, as opposed to underneath, where tool weight would be a liability. Tools that work well in one situation may not work well in another. Adaptation development requires a thorough job analysis.
Mechanical assists A mechanical assist can be defined as any mechanical device that helps to reduce the task demands on the worker. In this context we are concerned with devices that reduce the load moments about the elbow, shoulder, and neck. A mechanical assist may range from a complex robotic device capable of supporting high forces with low-force guidance to a simple work surface that relieves the worker of the need to support an object in use. Some examples of mechanical assists include the following: Lifts raise or lower materials to reduce bending and reaching and support work objects while they are in use.
A
B Figure 5e.9 (A) A traditional continuously moving assembly line. Parts are stored in front, beside, and behind the worker. (B) A modern “lean” line in which the parts for each operation are supplied in kits that follow the assembly on the line. The line stops until the work is complete.
Chapter 5e
Turntables rotate materials and work objects to reduce reaching. Tool balancers support tools against gravity. Articulating arms may be neutrally balanced to support tools and resist reaction forces and may be powered to provide increased lifting capability for heavy objects. Carts may be used to support work objects while in use and to transport them from one work station to another. Mounting fixtures and brackets hold tools in convenient locations/ orientations when not in use. Work fixtures and jigs hold work objects, reduce loads otherwise required to hold or use them, and free one or both hands for performing useful work. Work benches support the weight of work objects and should be adjustable to accommodate various heights of users and tasks. Tools and power tools ranging from a simple pry bar to a complex poster tool combined with an articulating arm reduce the strength required to perform tasks. Although mechanical assists can greatly reduce physical loads and task demands, failure to design, select, and install them properly can result in stressful postures and increased workloads. Assists must also be easily adjustable to suit each worker and task. Additional details of these devices are beyond the scope of this chapter but are readily available on the Internet.
Worker fitness and weight National health survey data show that the level of obesity in our society is growing rapidly.12 Although fitness and weight training are the concerns of health care providers, job designers need to understand their effects on work capacities and ability to meet job demands (Fig. 5e.1). Workers with low fitness levels exert less force for a given amount of time. Load moments on the shoulder of heavy people tend to be higher than those for a person with a low body weight because their arms are heavier (Table 5e.1c). Large body masses encroach on the work space close to the body, which is the ideal location for many work objects. A large body mass also may require a worker to reach farther and to produce greater shoulder moments than a small body mass. The treating physician or therapist should be consulted regarding how the work space should be adapted for a worker with a very large body mass.
Body supports Body supports such as arm rests are widely used to counteract gravity forces on the body.1,5,18,19 In the absences of arm rests, workers often use the edge of the work bench, desk, or keyboard or the work object itself, padded with pillows, foam pads, packing materials, and duct tape. Although improvised arm rests may look crude, they are often more effective than those provided with a chair or by the employer because their position is just right for specific workers and tasks. Although chair arm rests may be fine when the arms are relaxed at the sides, they may not be close when the work task is performed, or worse they may actually obstruct a worker’s arm motions. It is increasingly common, however, to find chair arm rests with vertical and lateral adjustability. Arm rests in motor vehicles are frequently
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adjustable, folding down to support the arm for highway driving and up and out of the way for city driving. Forearm rests can also be mounted on articulating arms that adjust vertically and move freely in a horizontal plane. Articulating forearm rests are well suited for keyboard- and mouse-intensive jobs and for some bench assembly work. Forearm rests may be fashioned also from slings suspended from balancers overhead that enable the worker to move in three dimensions while reducing loads on the shoulder. As with balancers used for power tools, placement and force adjustments for each worker and task are very important.
Evaluation of adaptations It is important that workplace adaptations be evaluated to ascertain their effectiveness. A well-intended adaptation may increase rather than reduce work demands because it was ill-conceived or improperly installed or adjusted. As a minimum, evaluations should include inspection of the job. A more formal assessment may require time- and event-based analyses of work postures and forces. Worker feedback in the form of perceived exertion from one or more users also may be used to evaluate the intervention. As a practical matter, there is very seldom sufficient control or statistical power to show a significant reduction in chronic soft tissue complaints and impairments, but most employers continue to monitor health records for possible changes.
SUMMARY Resulting from job demands that exceed an individual’s work capabilities, disability can be controlled by reducing these demands through workplace adaptations or by increasing workers’ capabilities through medical treatment and physical therapy. Determining disability and designing adaptations require understanding of the exposure-response relationship, which provides a framework for work factors, external workloads, internal tissue loads, pain, fatigue, and MSDs. Many examples of mechanical assists and body supports can be found by searching the Internet. Population and individual anthropometric data can be used to specify workplace layouts, equipment, tools, and procedures that help to reduce job demands and disability. Workplace adaptations should be evaluated to verify that they have achieved their intended effect.
REFERENCES 1. Aaras A, Fostervold KI, Ro O, Thoresen M, Larsen S: Postural load during VDU work: a comparison between various work postures. Ergonomics 40(11):1255-1268, 1997. 2. Armstrong T, Punnett L, Ketner P: Subjective worker assessments of hand tools used in automobile assembly. Am Ind Hyg Assoc J 50:639, 1989. 3. Armstrong TJ, Buckle P, Fine LJ, et al: A conceptual model for work-related neck and upper-limb musculoskeletal disorders. Scand J Work Environ Health 19(2):73-84, 1993. 4. Armstrong TJ, Franzblau A, Haig A, et al: Developing ergonomic solutions for prevention of musculoskeletal disorder disability. Assist Technol 13(2):78-87, 2001. 5. Attebrant M, Winkel J, Mathiassen SE, Kjellberg A: Shoulder-arm muscle load and performance during control operation in forestry machines: effects of changing to a new arm rest, lever and boom control system. Appl Ergon 28(2):85-97, 1997.
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18. 19.
20. 21. 22.
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Bernard B, ed: Musculoskeletal disorders and workplace factors: a critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. Cincinnati Department of Health, Education, and Welfare, Public Health Service, 1977, Centers for Disease Control, National Institute for Occupational Safety and Health. Bongers PM, deWinter CR, Kompier MA, et al: Psychosocial factors at work and musculoskeletal disease. Scand J Work Environ Health 19(5):297-312, 1993. Borg GA: Psychophysical bases of perceived exertion. Med Sci Sports Exerc 14(5):337-381, 1982. Brandt E, Pope A, eds: Enabling America: assessing the role of rehabilitation science and engineering. Washington, DC, 1997, National Academy of Press. Bystrom S, Fransson-Hall C: Acceptability of intermittent handgrip contractions based on physiological response. Hum Fact 36(1):158-171, 1994. Centers for Disease Control: Anthropometric reference data, United States, 1988-1994. National Center for Health Statistics, 2003. Centers for Disease Control and Prevention: Physical activity and good nutrition: essential elements to prevent chronic diseases and obesity 2004. Atlanta, 2004, Centers for Disease Control and Prevention. Chaffin DB, Andersson GBJ, Martin BJ, et al: Occupational biomechanics. New York, 1999, Wiley-Interscience Publication. Corlett EN, Bishop RP: A technique for assessing postural discomfort. Ergonomics 19(2):175-182, 1976. Dempster WT: Space requirements of the seated operator. Geometrical, kinematic and mechanical aspects of the body with special reference to the limbs. WrightPatterson Air Force Base, OH, 1955, Wright Air Development Center. Drillis R, Contini R: Body segment parameters. New York, 1966, New York Office of Vocational Rehabilitation. Drury CG: Methods for direct observation of performance. In JR Wilson, EN Corlett, eds: Evaluation of human work: a practical ergonomics methodology. Bristol, PA, 1995, Taylor & Francis, pp. 45-68. Feng Y, Grooten W, Wretenberg P, Arborelius UP: Effects of arm support on shoulder and arm muscle activity during sedentary work. Ergonomics 40(8):834-848, 1997. Feng Y, Grooten W, Wretenberg P, Arborelius UP: Effects of arm suspension in simulated assembly line work: muscular activity and posture angles. Appl Ergon 30(3):247-253, 1999. Gerr F, Marcus M, Ortiz D, White B, Jones W, Cohen S, et al: Computer users’ postures and associations with workstation characteristics. Aihaj 61(2):223-230, 2000. Grandjean E, Hunting W, Nishiyama K, Piderman M: Studies on an adjustable video screen work station. Soz Praventivmed 27(5):249-250, 1982. Hagberg M: Occupational musculoskeletal stress and disorders of the neck and shoulder: a review of possible pathophysiology. Int Arch Occup Environ Health 53(3):269-278, 1984.
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Harms-Ringdahl K: On assessment of shoulder exercise and load-elicited pain in the cervical spine. Biomechanical analysis of load—EMG—methodological studies of pain provoked by extreme position, Scand J Rehabil Med Suppl 14:1-40, 1986. Homan M, Armstrong T: Evaluation of three methodologies for assessing work activity during computer use. Am Indust Hyg Assoc J 64(1):48-55, 2003. Human Factors and Ergonomics Society: Draft standard for trial use human factors engineering of computer workstations, BSR/HFES 100. Santa Monica, 2002, Human Factors and Ergonomics Society. Jonsson B: The static load component in muscle work. Eur J Appl Physiol Occup Physiol 57(3):305-310, 1988. Krawczyk S, Armstrong TJ, Snook SH: Preferred weights for hand transfer task for an eight hour workday. Sweden, 1992, Intl. Scien. Conf. on Prevention of Work Related Musculoskeletal Disorders. PREMUS, Sweden, May 12-14, 1992. Kuorinka I, Jonsson B, Kilbom A, et al: Standardized Nordic health questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon 18(3):233-237, 1987. LeVeau BF, Williams M: Williams & Lissner’s biomechanics of human motion. Philadelphia, 1992, W.B. Saunders. Lowe BD: Accuracy and validity of observational estimates of shoulder and elbow posture. Appl Ergon 35(2):159-171, 2004. Mathiassen SE, Winkel J: Quantifying variation in physical load using exposure-vs-time data. Ergonomics 34(12):1455-1468, 1991. McCormick E, ed: Task analysis: handbook of industrial engineering. New York, 1982, John Wiley & Sons. Niebel BW, Freivalds A: Methods, standards, and work design. Boston, 1998, WCB/McGraw-Hill. NRC: Work-related musculoskeletal disorders: a review of the evidence. Washington, DC, 1999, National Academy Press. NRC and IOM: Musculoskeletal disorders and the workplace: low back and upper extremities. Washington, DC, 2001, National Academy Press. Ozkaya N, Nordin M: Fundamentals of biomechanics: equilibrium, motion, and deformation. New York, 1999, Springer-Verlag. Saldana N, Herrin GD, Armstrong TJ, Franzblau A: A computerized method for assessment of musculoskeletal discomfort in the workforce: a tool for surveillance. Ergonomics 37(6):1097-1112, 1994. Sauter SL, Schleifer LM, Knutson SJ: Work posture, workstation design, and musculoskeletal discomfort in a VDT data entry task. Hum Fact 33(2):151-167, 1991. Ulin SS, Ways CM, Armstrong TJ, Snook SH: Perceived exertion and discomfort versus work height with a pistol-shaped screwdriver. Am Ind Hyg Assoc J 51(11):588-594, 1990. Winters JM, Kleweno DG: Effect of initial upper-limb alignment on muscle contributions to isometric strength curves. J Biomech 26(2):143-153, 1993.
CHAPTER
Wrist and Hand
6
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6a
Epidemiology of Wrist and Hand Disorders David Rempel and Laura Punnett
This chapter summarizes the findings of epidemiologic studies that address workplace and individual factors associated with hand and wrist musculoskeletal disorders (MSDs). From an epidemiologic point of view, this topic is challenging because although many specific hand and wrist disorders such as carpal tunnel syndrome (CTS) and hand-arm vibration syndrome are recognized, no criteria for case definitions are universally accepted. More data are available for CTS than for other hand and wrist disorders because of its relatively well-defined pathology and available diagnostic methods such as nerve conduction velocity testing.79 These disorders are not new; epidemics and clinical case series of work-related hand and wrist tendinitis were reported throughout the 1800s and early 1900s.17,92 As summarized by a review by a National Academy of Sciences panel,65 many crosssectional studies and more recent prospective studies consistently identify certain key risk factors at the same time that they point to the multifactorial nature of work-related hand and wrist disorders. The etiology of these disorders includes both biomechanical and work organizational factors, along with reporting and clinical progression that are likely affected by the worker’s perception of the work environment and by medical management. A conceptual model of this complicated relationship, adapted from Armstrong et al4 and presented in Figure 6a.1, is based on epidemiologic studies and pathophysiologic mechanisms clarified in laboratory studies. Health care providers can apply this information and limit workplace exposures to risk factors both to reduce the overall incidence of hand, wrist, and other musculoskeletal disorders (primary prevention) and to prevent loss of function in patients (secondary and tertiary prevention) in whom such disorders have occurred.
FREQUENCY, RATES, AND COSTS National incidence rates of work-related hand and wrist disorders in the United States are not easy to assess because of the difficulty in attributing causation and the sparse data on background incidence and prevalence. Annual incidence rates of all work-related repeated-motion disorders reported by U.S. private employers to the Bureau of Labor Statistics are shown for 1980 to 2000 in Figure 6a.2. Approximately 55% were hand or wrist disorders, a percentage also reported in industrial studies60 and in studies from other countries.46 The dramatic rise after 1983 may be partially explained by early industry under-reporting on the Occupational Safety and Health Administration (OSHA)
200 log, a factor partially rectified in the early 1980s after OSHA levied large fines against some meat processing and automobile manufacturers for under-reporting. A similar calendar trend in work-related hand/forearm problems has been observed in other countries such as Finland,46 Australia,7 and Japan.70 Rates of hand and wrist symptoms and associated disability among working adults were assessed by a 1988 national interview survey of 44,000 randomly selected U.S. adults (National Health Interview Survey).71 Of those who had worked any time in the past 12 months, 22% reported some finger, hand, or wrist discomfort that fit the category “pain, burning, stiffness, numbness, or tingling” for 1 or more days in the past 12 months. Only one fourth were due to an acute injury such as a cut, sprain, or broken bone. Nine percent reported having prolonged hand discomfort, that is, discomfort of 20 or more days during the last 12 months or 7 or more consecutive days that was not due to an acute injury. Of those with prolonged hand discomfort, 6% changed work activities and 5% changed jobs because of the hand discomfort. From the same data set it was estimated that in 1988 alone there were 520,000 cases of work-related hand and wrist disorders (CTS and tendon syndromes) in the United States.89 Administrative records (e.g., workers’ compensation) are frequently used to estimate incidence rates, but the data are extremely problematic to interpret because of varying decision rules that may have no clinical value in defining a “case.” For example, Fine et al26 evaluated multiple records for the same time period at two U.S. automobile plants. Within each facility the magnitude of the incidence rates of hand and arm disorders varied dramatically between data sources: The rates were 10 times higher in the workers’ compensation records than in the OSHA 200 log and 10 times higher in the plant medical records than in the compensation data. Nevertheless, the relative ranking of the departments within each plant was similar, regardless of which data source was used. The incidence of work-related CTS, impact of work disability, and factors predicting disability have been assessed on a large scale in Washington State. A review of 7926 workers’ compensation claims for CTS from 1984 to 1988 yielded an industry-wide
Work-related factors • Work organization • Repetition • Force • Posture Individual factors • Size • Capacity • Behavior • Repair
Internal load (dose) Discomfort Pain Disorder Disability
Figure 6a.1 A possible model of the relationship between exposure to work, worker attributes, and development of chronic musculoskeletal disorders of the hands and wrist. Internal loads and individual capacity result in a reversible cascading series of events ranging from minor mechanical or biologic disturbances to tissue damage and disability. (Modified from Armstrong TJ, Buckle P, Fine LJ, et al: Scand J Work Environ Health 19:73-84, 1993.)
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Figure 6a.2 Incidence rates (per 1000 full-time employees) of repeated-motion disorders for all U.S. private-sector workers from 1980 to 2000. The lower curve is the incidence for industries with primarily office work (finance, insurance, and real estate). Approximately 55% are hand/wrist disorders. (From Bureau of Labor Statistics, 1980-2000.)
incidence rate of CTS claims of 1.74 per 1000 full-time employees.27 Rates up to 20 cases per 1000 full-time employees were observed in shellfish, fish, and other meat-packing industries. Industries with the highest rates of occupational CTS are presented in Figure 6a.3. The ranking of these rates also shows a high correspondence with the occupations in Finland having the highest rates of hand, wrist, and forearm disorders, despite some geographic differences in industry. Disability burden was quantified as “years of productivity lost,” addressing time lost from work for incident compensation claims in 1986.30 Upper extremity strains were the third
highest cause of years of productivity lost, after sprains of the back/neck and lower extremity, representing 1.8 years lost per thousand workers per year. CTS had a lower incidence rate but caused more lost time per case, accounting for 0.5 years lost per 1000 worker-years. Approximately 40% of all the Washington State workers with CTS went on to surgical treatment.1 Of these, the mean duration of lost time was 4 months. The length of time lost from work was not associated with demographic factors (age, gender, wage) or case severity as assessed by clinical staging or nerve conduction values. Most (67%) returned to the same job, 15% found a different job, and 3 years after surgery 18%
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Figure 6a.3 Population age-specific incidence rates of carpal tunnel syndrome for Rochester, Minnesota, from 1961 to 1980 (——) (n = 1016)75 as compared with work-related incidence rates for the Washington State workers’ compensation system from 1984 to 1988 (...) (n = 7926).28
Chapter 6a
had not returned to work. Workers from jobs with elevated rates of CTS or those involving repetitive hand activity were less likely to return to the same job. A return to repetitive or physically demanding work is a predictor of poor long-term outcome after surgery.2,58 Few data are available to assess the long-term financial and functional impact on patients and society, but best estimates by the National Academy of Sciences panel place the average direct cost per workers’ compensation case at over $8000, with total cost estimates for all MSDs as high as $45 to $54 billion per year, around 0.8% of the nation’s gross domestic product.65 A population survey in Connecticut indicated that only about one in five persons with medical treatment for work-related MSDs was reimbursed by compensation and that they had substantial other social and economic costs, ranging from loss of function to decreased job advancement to losing a car or home for financial reasons.62
DISORDER TYPES AND THEIR NATURAL HISTORY Figure 6a.3 lists some hand and wrist disorders identified in occupational epidemiologic studies. Nonspecific hand/wrist pain is the most common problem, followed by tendinitis, ganglion cysts, and CTS.38,53,60,86 In their early stages, these disorders may be manifested by nonspecific symptoms without signs or laboratory findings. It is important to remember that symptoms in the hand may be due to nerve or vascular lesions further up the arm. When measured in high-risk workplaces, rates of nonspecific symptoms, tendinitis, and CTS appeared to track each other; that is, specific disorders usually do not occur in isolation. For example, in a pork processing plant, the rank order of hand and wrist problems as a percentage of all morbidity was nonspecific hand/wrist pain, 39%; CTS, 26%; trigger finger, 23%; trigger thumb, 17%; and de Quervain tenosynovitis, 17%.61 Among packers in a bread factory, whose work involved repetitive and forceful gripping, approximately one half had wrist/hand tenosynovitis (compared with 14% among retail shop assistants).53 The most common disorder of the hand or wrist was thumb tenosynovitis, followed by finger/wrist extensor tenosynovitis. CTS was diagnosed in four packers and in no control subjects. Similar ratios of disorders have been observed in manufacturing workers,6,60,86 food processors,47,53 and computer operators.9,38 For the purposes of this chapter, tendinitis includes hand, wrist, and distal forearm tendinitis or tenosynovitis and trigger finger. Tendinitis occurs at discrete locations, the most common site being the first extensor compartment (de Quervain disease), followed by the five other pulley sites on the extensor side of the hand and three on the flexor side. The diagnosis is based on the history, symptom location, and palpation and provocative maneuvers on physical examination.34 No association of tendinitis with age has been found, but a bimodal curve with seniority has been described; work-related tendinitis was higher among workers with less than 3 years of employment, for example,60 suggesting that performance of unaccustomed tasks is a risk factor and/or that affected workers are less likely to remain in the job. In cross-sectional workplace studies, the prevalence of ganglion cysts, as assessed by physical examination, is 2% to 3%.9,38,60
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Individual Factors
Whether these rates are higher among those performing repetitive hand activity versus those performing tasks with low repetitiveness is unknown. In the absence of universally accepted diagnostic criteria for CTS, some consider just an abnormal nerve conduction study a gold standard.39,45,63 Relying exclusively on nerve conduction studies can lead to very high prevalences, however, such as 28%63 and 19%8 in low-risk working populations. The usual signs of CTS have relatively poor sensitivities and specificities28,39,45; only in the late stages of the disease or in the elderly are weakness and thenar atrophy noticeable features, and in approximately 25% of cases, CTS is accompanied by other disorders of the hand or wrist.72 Although consensus criteria using symptom history and nerve conduction study findings have been proposed,79 the combination of a positive nerve conduction velocity test and symptoms consistent with CTS represents a preferable case definition. Few studies have evaluated how osteoarthritis of the hand and wrist relates to work.35,99 Hadler et al35 assessed the hands of 67 workers at a textile plant in Virginia. Significant differences in finger and wrist-joint range of motion, joint swelling, and radiograph patterns of degenerative joint disease were observed between three different hand-intensive jobs; the observed differences were reported to match the pattern of hand usage. Hand-arm vibration syndrome, or vibration white finger disease, occurs in occupations involving many years of exposure to vibrating hand tools.66 This disorder of the small vessels and nerves in the fingers and hands is manifested as localized blanching at the fingertips with numbness on exposure to cold or vibration. The symptoms are largely self-limited if vibration exposure is eliminated at an early stage,20,31 but with continuing exposure the condition becomes irreversible. Hypothenar hammer syndrome, or occlusion of the superficial palmar branch of the ulnar artery, has been associated in clinical series and case-control studies with habitually using the hand for hammering52,69 and with exposure to vibrating hand tools.44 The mean length of exposure before seeking medical attention was 20 to 30 years. Small case-control studies or clinical series have described factors associated with less common disorders such as gamekeeper’s thumb,14,68 digital neuritis, ulnar neuropathy at the wrist,86 and Kienböck disease.32
INDIVIDUAL FACTORS In general population studies and clinical case series, the average age of patients with CTS is approximately 55 years.10,72,88,100 In contrast, the mean age for “occupational” cases, based on the Washington State workers’ compensation study, is 37.5 years.27 Furthermore, as displayed in Figure 6a.3, the incidence increases with age in the general population but does not appear to do so in the occupational cohort. Only 3% of the variability in median nerve latency in a cross-sectional study of an industrial cohort is explained by age.63 In another prospective study, age was not a predictor for incidence of CTS or for wrist tendonitis in a mixed occupational cohort51 or of tendon-related disorders of the hand and forearm among computer users.34 Similarly, gender appears to play a greater role in populationbased studies of CTS than in industrial studies. In regional
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population studies and clinical series, the incidence of CTS is higher in females than in males by a factor of 2.2:1 to 3.7:1,10,72,88,100 whereas in workplace studies, when employees perform similar hand activities, the ratio is much closer to unity at 1.2:1.27,34,63,86 CTS can be a sequela (usually self-limiting) of pregnancy21; however, the role of other female reproductive factors such as oophorectomy, hysterectomy,11,15,18,77 or the use of oral contraceptives82 is less certain. The overall implications are that when hand activities are taken into account, the differences between working men and women are not particularly prominent, and hormonal influences likely account for relatively little morbidity when ergonomic exposures are high.76 Other individual factors with strong associations to CTS are diabetes mellitus,72,88,100 rheumatoid arthritis,72,88,100 and obesity.18,23,63,94,97 For other factors, including thyroid disorders,38,72 vitamin B6 deficiency,3,22,59 wrist size and shape,5,12,33,43 and general deconditioning,63 the associations are based on single studies or the studies present conflicting results. Nonspecific distal symptoms have also been associated with systemic disease, obesity, smoking, and other nonoccupational factors.51,73,75
WORK-RELATED FACTORS Figure 6a.3 summarizes the characteristics of work that have been associated with elevated rates of hand and wrist symptoms and with specific disorders like CTS and tendinitis. The number of prospective studies has increased substantially in recent years, and the risk factors identified tend to be quite consistent with
those of older cross-sectional studies of the same endpoints.95 Tables 6a.1 and 6a.2 summarize selected studies of wrist and hand tendinitis and CTS that included a control group. Hand/wrist pain and disorders have been associated with repetitive hand and finger motions characterized by a variety of metrics. Prevalences are generally high in manual-intensive occupations such as data-entry work, postal sorting, cleaning, industrial inspection, and packaging.65 In a study relying exclusively on nerve conduction measurements, median nerve slowing occurred at a higher rate among assembly line workers than among administrative control subjects.64 Assembly line workers appeared to have more repetitive tasks than the control group. Similar results were obtained in comparisons of garment workers performing repetitive hand tasks with hospital employees not using computer keyboards77 and in bread packers compared with retail shop attendants.53 A number of other cross-sectional and prospective studies have similarly observed the importance of high hand pace, short cycle time, little variation in tasks, and lack of rest breaks for risk of CTS,8,16,50,80,98 tendinitis,47 and hand pain or combined disorders.25,49 This range of metrics illustrates the varied ways that “repetitive motion” may be operationalized in addition to high velocity or acceleration of the wrist or rate of repetition of postural stress.57 The force applied to a tool or materials during repeated or sustained gripping is also a predictor of the risk for tendinitis, CTS, and other distal extremity disorders. For example, in a study of the textile industry, the risk of hand and wrist tendinitis was 3.9 times higher among packaging and folding workers than among knitting workers, who performed work that was
Table 6a.1 Selected controlled epidemiologic studies evaluating the association between work and wrist, hand, or distal forearm tendinitis* Authors
Exposed population
Control population
Kuorinka et al, 1979 Luopajarvi et al, 197953† Silverstein et al, 198686§||
90 scissors makers 152 bread packaging Industrial 143 low force/high rep 153 high force/low rep 142 high force/high rep Manufacturing 369 packers/folders 562 sewers 296 boarding workers 102 meat cutters 107 sausage makers 118 packers 352 manufacturing workers (high/low rep)
133 shop attendants 133 shop attendants Industrial 136 low force/low rep 136 low force/low rep 136 low force/low rep Manufacturing 352 knitting workers 352 knitting workers 352 knitting workers 141 office workers 197 office workers 197 office workers
McCormack et al, 199060
Kurppa et al, 199147†¶
Latko et al, 199949
*Case criteria are based on history and physical examination. †All exposed and control subjects are female. ‡Significant difference from control. §Adjusted for age, sex, and plant. ||Analysis includes other disorders, although tendinitis was most common. ¶Cohort study with a 31-month follow-up. OR, odds ratio.
Rate in exposed (%)
Rate in control (%)
18 53‡
14 14
3? 4? 20‡
1.5 1.5 1.5
3.3‡ 4.4‡ 6.4‡ 12.5? 16.3‡ 25.3‡ OR = 3.23
0.9 0.9 0.9 0.9 0.7 0.7
Chapter 6a
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Work-Related Factors
Table 6a.2 Selected controlled epidemiologic studies evaluating the association between work and carpal tunnel syndrome* Authors
Exposed population
Control population
Criteria
Silverstein et al, 198787†
Industrial High force/high rep 22 keyboard operators 164 assembly line 115 general plant 23 grinders 106 ski manufacturing repetitive jobs 65 factory workers/65 case controls
Industrial Low force/low rep 147 admin/clerical 147 admin/clerical 147 admin/clerical 147 admin/clerical 67 ski manufacturing nonrepetitive jobs
History and physical examination Electrodiagnostic Electrodiagnostic Electrodiagnostic Electrodiagnostic Electrodiagnosis and signs Symptoms, signs, electrodiagnosis, surgery
Nathan, 198864§||
Barnhart, 19918§ Roquelaure et al, 199780
Rate in exposed (%)
Rate in control (%)
5.1‡
0.6
27 47 38 61‡ 15.4‡
28 28 28 28 3.1
OR = 9.0 (2.4-33.4) for force and OR = 8.8 (1.8-44.4) for repetition
*Diagnoses are based on history and physical examination or nerve conduction study. †Controlled for age, gender, and years on job. ‡Significantly different from control group. §Controlled for age and gender. ||Low participation rate and limited exposure assessment. OR, odds ratio.
much less physically demanding. In a study by Moore and Garg61 at a pork processing plant, in the jobs that involved high grip force or long grip durations such as Wizard knife operator, snipper, feeder, scaler, bagger, packer, hanger, and stuffer, almost every employee was affected. Others observed a similar relationship with work involving sustained or high force grip in grinders,64 meatpackers and butchers,23,47 and other industrial workers.51,92,96 A comprehensive cross-sectional study of the combined factors of repetition and force was conducted among 574 industrial workers by Silverstein et al.86,87 Disorders were assessed by physical examination and history and were primarily tendinitis followed by CTS, Guyon tunnel syndrome, and digital neuritis. Subjects were classified into four exposure groups based on force and repetition. The “high-force” work involved a grip force averaging more than 4 kg of force, whereas “low-force” work involved less than 1 kg of grip force. The “high-repetition” work involved a repetitive task in which either the cycle time was less than 30 seconds (greater than 900 times in a work day) or more than 50% of the cycle time was spent performing the same kind of fundamental hand movements. After adjusting for plant, age, gender, and years on the job, the high-risk groups were compared with the low-risk group. The odds ratio of all hand/wrist disorders for high force alone was 5.2 and that for high repetition alone was 3.3; this increased to 29 for jobs that required both high force and high repetition. The identical analysis of just CTS revealed an odds ratio of 1.8 for force, 2.7 for repetition, and 14 for the combined high-force high-repetition group. Years of exposure to both repetitive wrist movement and “heavy load on the wrist” were strongly associated with CTS.83 Estimates of the CTS cases among workers who perform repetitive or forceful hand activity that can be attributed to work range from 50% to 90%.36,91 Other investigations similarly highlighted the combined effects of repetition, force, postural load, and
other physical stressors.37, 77, 80 The importance of addressing all such exposures simultaneously in workplace interventions is further demonstrated by the effect of multifaceted ergonomic interventions in reducing upper extremity morbidity.13,25,67 Work involving increased wrist deviation from a neutral posture in either the extension/flexion or ulnar/radial direction has been associated with CTS and other hand and wrist problems.40,92,93 de Krom et al18 conducted a case-control study of 156 subjects with CTS versus 473 control subjects randomly sampled from the hospital and population registers in a region of the Netherlands. After adjustment for age and sex, a doseresponse relationship was observed for increasing hours of work with the wrist in extension or flexion. No risk was observed for increasing hours performing a pinch grasp or typing, although methodologic limitations may have obscured such associations. Some studies of computer operators have linked awkward wrist postures to severity of hand symptoms,24 risk of tendinitis or CTS,84 and arm and hand discomfort.19,41,83 In a large population sample, both CTS and distal tendonitis were associated with repetitive occupational bending and twisting of the hands and wrists.89,90 Wrist angles measured by electrogoniometry were strongly linked with wrist disorders in a range of service and manufacturing occupations; forceful exertions and repetitiveness were also risk factors, although they were correlated with each other too strongly to distinguish their effects.55 Prolonged exposure to vibrating hand tools such as chain saws has been linked in prospective studies to hand-arm vibration syndrome.20,31 The risks are primarily vibration acceleration, amplitude, and frequency; hand coupling to tool; hours per day of exposure; and years of exposure. Based on existing studies, however, no clear vibration acceleration/frequency/duration threshold has been found that would protect most workers. Medical surveillance is therefore recommended to identify
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cases early while the disease can still be reversed.66 Nonetheless, both the American National Standards Institute and the International Standards Organization have promulgated guidelines limiting the duration of exposure as a function of acceleration and frequency. The use of vibrating hand tools may also increase the risk of CTS,15,81,85,98 either by direct nerve injury or by indirectly increasing applied grip force through a reflex pathway.78 Prolonged or high-load localized mechanical stress over tendons or nerves from tools or from resting the hand on hard objects has been associated with tendinitis93 and nerve entrapment40,72 in case studies. The average total hours per day that a task is repeated or sustained has been a factor in predicting hand problems.54,56 For example, an increase in hours of computer use has consistently been a predictor of increased symptom prevalence.9,24,26,41,74 In prospective studies of computer users, increasing hours of keyboard and mouse use predicted increased incidence of hand/ wrist pain and tendonitis, especially above 20 hours per week.34,42 In cross-sectional studies, work organizational factors (e.g., work structure, decision control, workload, deadline work, supervision) and psychosocial factors (e.g., job satisfaction, social support, relationship with supervisor) appear to have some influence on hand and wrist symptoms. Work organizational factors represent upstream determinants of both physical motion patterns and subjective psychosocial work experiences. For example, justin-time production systems increase both the work pace48 and the risk of CTS.50 In an automotive manufacturing plant, improved work station design was negatively offset by a change to assembly line production with very short-cycle, monotonous, “robotized” jobs.29 Among banking employees, longitudinal changes in work scheduling and rest break policies were shown to predict changes in medical morbidity.25 Among newspaper reporters and editors, psychosocial factors modified the expected relationship between work station design and hand and wrist symptoms. Symptom intensity increased as keyboard height increased among those with low decision latitude but not among those with high decision latitude.24 In another study of newspaper employees, the risk of hand and wrist symptoms was increased among those with increasing hours of deadline work and less support from the immediate supervisor.9 Among directory assistance operators at a telephone company, high information-processing demands were associated with an elevated rate of hand and wrist disorders.38 On the other hand, in an industrial setting, Silverstein et al86 observed no association with job satisfaction. Because these problems may develop in the workplace after and as a consequence of employees’ symptoms and unsuccessful efforts to obtain job modifications or other accommodation, psychosocial factors are the most difficult to interpret in crosssectional studies. Overlapping measurement approaches may also obscure the relationships among work organization, physical, and psychosocial factors.
SUMMARY Although variability exists between industries, hand and wrist disorders account for many work-related upper extremity MSDs. These disorders are costly to the worker, employer, and workers’
compensation system; however, a full accounting of their financial impact has yet to be done. Hand and wrist problems may present in any number of ways, from the most common presentation of nonspecific hand symptoms to discrete entities such as hand-arm vibration syndrome or de Quervain tenosynovitis. The rates of specific disorders correspond to high symptom rates in a work population. Studies point to a multifactorial relationship between work and these disorders. Some disorders such as tendinitis and CTS are clearly associated with repetitive and forceful hand use, postural stress, and vibration. For other disorders such as ganglion cysts and osteoarthritis, the relationship to work has not been well studied. Symptom severity and disorder rates—or at least their reporting—appear to be influenced by work organizational factors such as decision latitude and cognitive demands. In population-based studies and clinical case series, CTS in particular has been linked to individual factors. However, in workplace studies when workplace exposure is high and quantified, individual factors play a limited role relative to workplace factors.5,15,24,38,41,87
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Epidemiology of wrist and hand disorders
Rothfleisch S, Sherman D: Carpal tunnel syndrome: biomechanical aspects of occupational occurrence and implications regarding surgical management. Orthop Rev 7:107-109, 1978. Sabour M, Fadel H: The carpal tunnel syndrome, a new complication ascribed to the pill. Am J Obstet Gynecol 107:1265-1267, 1971. Sauter SL, Scheifer LM, Knutson SJ: Work posture, work station design, and musculoskeletal discomfort in a VDT entry task. Hum Fact 33:151-167, 1991. Seligman P, Boiano J, Anderson C: Health hazard evaluation of the Minneapolis Police Department. Springfield, VA, 1986, NIOSH HETA 84-417-1745, U.S. Department of Commerce, National Technical Information Service. Seppalainen AM: Nerve conduction in the vibration syndrome. Scand J Work Environ Health 6:82-84, 1970. Silverstein BA, Fine LJ, Armstrong TJ: Hand wrist cumulative trauma disorders in industry. Br J Ind Med 43:779-784, 1986. Silverstein BA, Fine LJ, Armstrong TJ: Occupational factors and carpal tunnel syndrome. Am J Ind Med 11:343-358, 1987. Stevens JC, Sun S, Beard CM, O’Fallon WM, Kurland LT: Carpal tunnel syndrome in Rochester, Minnesota, 1961 to 1980. Neurology 38:134-138, 1988. Tanaka S, Petersen MR, Cameron LL: Prevalence and risk factors of tendinitis and related disorders of the distal upper extremity among U.S. workers: comparison to carpal tunnel syndrome. Am J Ind Med 39:328-335, 2001. Tanaka S, Wild DK, Cameron LL, Fruend E: Association of occupational and nonoccupational risk factors with the prevalence of self-reported carpal tunnel syndrome in a national survey of the working population. Am J Ind Med 35:550-556, 1997.
91. Tanaka S, Wild DK, Seligman PJ, et al: The US prevalence of self-reported carpal tunnel syndrome. Am J Public Health 84:1846-1848, 1994. 92. Thompson A, Plewes L, Shaw E: Peritendinitis crepitans and simple tenosynovitis: a clinical study of 544 cases in industry. Br J Ind Med 8:150-160, 1951. 93. Tichauer E: Some aspects of stress on forearm and hand in industry. J Occup Med 8:63-71, 1966. 94. Vessey MP, Villard-MacInosh L, Yeates D: Epidemiology of carpal tunnel syndrome in women of childbearing age. Finding in a large cohort study. Am J Epidemiol 19:655-659, 1990. 95. Viikari-Juntura E, Silverstein BA: Role of physical load factors in carpal tunnel syndrome. Scand J Work Environ Health 25:163-185, 1999. 96. Welch R: The causes of tenosynovitis in industry. Ind Med 41:16-19, 1972. 97. Werner RA, Albers JW, Franzblau A, Armstrong TJ: The relationship between body mass index and the diagnosis of carpal tunnel syndrome. Muscle Nerve 17: 632-636, 1994. 98. Wieslander G, Norback D, Gothe CJ, Juhlin L: Carpal tunnel syndrome (CTS) and exposure to vibration, repetitive wrist movements, and heavy manual work: a case-referent study. Br J Ind Med 46:43-47, 1989. 99. Williams WV, Cope R, Gaunt WD, et al: Metacarpo-phalangeal arthropathy associated with manual labor (Missouri meta-carpal syndrome). Arthritis Rheum 30:1362-1371, 1987. 100. Yamaguchi D, Liscomb P, Soule E: Carpal tunnel syndrome. Minn Med J 22-23, 1965.
CHAPTER
6b
Biomechanics of the Wrist and Hand Rita M. Patterson and Kai-Nan An
The human hand is a relatively mobile three-dimensional structure capable of conforming to the shape of manipulated objects. The biomechanical structure of the hand can be considered a linkage system of intercalated bony segments balanced by muscle and tendon forces and joint constraints. This chapter reviews some of the unique qualities that affect the biomechanics of the hand and wrist: normal skeletal and soft tissue anatomy, joint constraint and stability, range of joint motion and strength, and more basic biomechanical considerations of muscle-tendon function.
SKELETAL AND LIGAMENTOUS ANATOMY/JOINT CONSTRAINT Joint constraint and stability are provided by the joint articular surfaces, the capsuloligamentous structures, and the musculotendinous units. Primary joint stability is related to balance of the muscle and tendon forces to an externally applied force, with the capsuloligamentous structures appearing to stabilize initially against instantaneous loading and to provide secondary maintenance of joint stability. The collateral ligaments of all the hand joints and the intercarpal ligaments in the wrist are important soft tissues for joint constraint. The locations and orientations of the ligament lines of action determine their characteristics in resisting loads on the joint. For example, the radial collateral ligament and the ulnar collateral ligament are the primary ligaments of the metacarpophalangeal joint. Originating from the radial-dorsal aspect of the metacarpal head with insertion into the radial-volar aspect of the proximal phalanx, the radial collateral ligament is the primary ligament resisting ulnar deviation and pronation of the proximal phalanx at the metacarpophalangeal joint. The ulnar collateral ligament, on the other hand, is the primary constraint in resisting radial deviation and supination of the proximal phalanx. The relative contribution of each of the ligaments in resisting joint displacement has been studied by sequential sectioning or removal of the individual ligaments (Fig. 6b.1). The reduction of the load after removal of each ligamentous structure represents the contribution of that ligament. Anatomic studies performed on the carpal bones and the ligaments of the wrist in particular have identified several morphologic differences associated with degenerative changes and with specific kinematic (motion) patterns. Viegas and colleagues14 identified two different lunate shapes. Type II has a facet that articulates with the hamate and has been associated with increased arthritis in its proximal pole. Type I has no facet.
Most wrist ligaments are considered true intracapsular ligaments and tend to be oriented obliquely, from the periphery of the wrist toward the midline, from a proximal to distal direction. The volar ligaments are well established as the primary stabilizers of the wrist joint. Studies investigated the anatomy and mechanical strength of the dorsal ligaments of the wrist. Together the dorsal intercarpal (DIC), dorsal radiocarpal, and dorsal scapholunate (SL) interosseous ligaments create a lateral “V” that delivers indirect dorsal stability between the scaphoid and the radius while still allowing a threefold change in distance between the radius and the scaphoid dorsal groove. This unique design allows dorsal stability of the scaphoid throughout the range of motion of the wrist that would require changes in the linear dimension of a “dorsal radioscaphoid ligament” far greater than any fixed ligament could accommodate (Fig. 6b.2). The combined mechanical properties of the DIC, dorsal SL interosseous, and dorsal radiocarpal ligaments together function to maintain scaphoid stability and alignment while allowing for carpal mobility.18 Three distinct ligaments around the scaphoid trapezium and trapezoid (STT) joint have also been identified. The STT ligaments extend distally (scaphoid trapezial ligament) and ulnarly (scaphocapitate and scaphotrapezium ligaments) to form a “V.” The plane of the V-shaped STT ligament is essentially parallel to that of the trapezium-trapezoid articulation and corresponding interfacet ridge on the joint surface of the distal pole of the scaphoid. This ridge runs radiodorsal to ulnopalmar, a 45-degree angle from the sagittal plane13 (Fig. 6b.3).
MOTION The fingers and thumb consist of phalanges articulated at the interphalangeal joints. Within the physiologic range of motion, the interphalangeal joints can be considered hinges that allow flexion/extension. In a normal hand, each interphalangeal joint has at least 90 degrees of motion. The proximal phalanx articulates with the metacarpal at the metacarpophalangeal joints, which are usually considered universal joints, allowing not only flexion/extension but also abduction/adduction. Normally, the range of flexion/extension is about 90 degrees and that of abduction/adduction is 20 to 30 degrees. A composite articulation of eight carpal bones, the wrist joint connects the digits of the hand to the radius and ulna of the forearm. The range of wrist motions required to comfortably perform activities of daily living consists of 60 degrees of extension, 54 degrees of flexion, 40 degrees of ulnar deviation, and 17 degrees of radial deviation. Most of the hand placement and range-of-motion tasks can be accomplished with 70% of wrist motion maximum range. This converts to 40 degrees each of wrist flexion, wrist extension, and combined radial/ulnar deviation. Wrist flexion/extension and radial/ulnar deviation has traditionally been modeled as a fixed center of rotation through the proximal aspect of the capitate. However, studies have described the flexion/extension axis of the wrist as moving between the lunate and capitate. During global wrist motion, the radiolunate joint contributes more motion in flexion, whereas the lunocapitate joint contributes more motion in extension.16 Other studies described the kinematics of the lunate and the differences due to lunate type.13,18 The kinematics of type I lunate
Chapter 6b
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Biomechanics of the Wrist and Hand
0.6 Extended MP joint a
a: Intact
b c
Sequential sectioning of b: RCL-P c: RCL-D d: UCL-P e: UCL-D
Torque (N-m)
220
0.4 a b c
0.2 a b c
Pronation 20
a b c
10
10
a
d
d e
20 Supination
a
0.2 a
0.4
Figure 6b.1 Load-displacement curves were obtained by measuring the restraining torques when the metacarpophalangeal joints were displaced in supination and pronation. Curve a represents the torques with the entire capsule-ligament complex intact. Curves b and c represent the torques when the palmar and dorsal portions of the radial collateral ligament, respectively, were sectioned, whereas curves d and e represent those when the palmar and dorsal portions of the ulnar collateral ligament, respectively, were sectioned. The difference in load between each curve for a given displacement indicates the contribution of that particular sectioned element. For example, the difference in load between curves a and b represents the contribution of the palmar portion of the radial collateral ligament. N-m, newton-meter. (From An KN, Cooney WP III: Biomechanics, section II, the hand and wrist. In BF Morrey, ed: Joint replacement arthroplasty. New York, 1991, Churchill Livingstone International, pp. 137-146.)
motion differs from that of type II. The total range of radial/ ulnar translation of type II lunates was greater than that of type I lunates during radial/ulnar deviation. Compared with that of type I lunates, extension of type II lunates occurred later during ulnar deviation, whereas flexion of type II lunates occurred earlier. Describing the kinematics of the STT joint, Moritomo et al13 found that the trapezium and the trapezoid rotate as a unit with respect to the scaphoid during either flexion/extension or radial/ ulnar deviation of the wrist.
STRENGTH The potential strength of various joints in the hand and wrist in normal subjects has been studied with dynamometers. Normal pinch strengths ranged from 3 to 10 kg and grasp strengths from 20 to 40 kg. The wrist position and size of the grasped object have a significant influence on grip strength, which has been studied extensively as a function of wrist joint position. A self-selected wrist position of 35 degrees of extension and 7 degrees of ulnar deviation has been identified as the position in which maximum grip strength can be generated.15 For a given size of an object, grip strength is significantly reduced when the wrist position deviates from this self-selected position.
Forearm position has been shown also to affect key and fingertip pinch strength but not three-jaw chuck pinch strength. The neutral forearm position rendered the highest mean score and the pronated position the lowest mean score for key and fingertip pinch strength. Although these effects were consistent, the statistically significant effects of forearm position were less than 1 pound of force and may not be clinically relevant. However, standardized forearm positioning during pinch strength measurement is still recommended.17 The strength of the wrist joint is in the range of 10 to 20 Nm of flexion, 6 to 10 Nm of extension, 10 to 18 Nm of radial deviation, and 10 to 20 Nm of ulnar deviation.
TENDON EXCURSION The ability to control the movement of an individual digit of the hand depends very much on the anatomic arrangement of the musculotendinous complex. The magnitude of tendon excursion during joint movement for a given task would be important also for assessing possible overuse injury caused by cumulative trauma. For the finger and thumb, the pulley structures on the palmar side of the digits restrain bowstringing of the digital flexor
Chapter 6b
Flexion Tq
Sc
Radius Ulna
Extension Sc
Tq
Radius Ulna
Figure 6b.2 The lateral “V” configuration of the dorsal radiocarpal/ dorsal intercarpal construct allows dorsal stability of the scaphoid along with a threefold change in the distance between the radius and the dorsal groove of the scaphoid between flexion and extension of the wrist (arrows).
c
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Muscle and Joint Forces
during joint flexion. Alteration of such a pulley system in the hand disturbs the relationship between tendon excursion and joint angular displacement, and thus joint function. Parameters have been defined from the curves of tendon excursion and joint motion for comparing tendon-pulley joint interactions under normal and abnormal conditions.9 The range of movement of the joint produced by a given standardized amount of excursion is called the effective range of motion. Absolute tendon excursion is that from full extension to 90 degrees of flexion as measured with the flexor tendon set at its normal length in the neutral position. Division of the pulley would result in bowstringing and adding slack to the tendon system, which would have to be taken up before any joint motion could occur. This amount of tendon slack is termed bowstring laxity. Subtracted from absolute tendon excursion, bowstring laxity defines relative tendon excursion. The biomechanical functions of the musculotendinous complex can be understood in terms of the relationship of tendon excursion to joint angular displacement. The rate of change in tendon excursion as the joint rotates is equal to the moment arm of the associated muscle or tendon for that specific joint motion.4 The moment arm defines not only the effectiveness of the tendon in joint rotation but also its mechanical advantage in resisting external loads. The larger the moment arm, the higher the torque and rotation angle generated for the same amount of muscle force and excursion. A determination of the potential moment arm contributions of muscles can provide insight into the balance of forces at a joint for planning tendon transfers or designing orthotics to help provide mobility or stability while minimizing loss of function. Tendon excursion and joint rotation angles of the wrist, for example, are measured by using an electric potentiometer and an electromagnetic tracking device, respectively.1 The instantaneous moment arms of each tendon are then calculated from the slope of the curve between the tendon excursion and the joint angular displacement. Calculated tendon moment arms are found to be consistent throughout a full range of flexion/extension and radio/ulnar deviation motion; they correspond closely to the anatomic location and orientation of the tendons (Fig. 6b.4).
MUSCLE AND JOINT FORCES a
FCR b
Figure 6b.3 The ligaments around the scaphoid trapezium and trapezoid joint at the palmar aspect of the left wrist. (a) The scaphotrapezial (S-Tm) ligament; (b) the scaphocapitate (S-C) ligament; (c) the capitate-trapezium (C-Tm) ligament. FCR, flexor carpi radialis.
The potential force generated by a muscle depends on its size and architecture. Three anatomic parameters of muscle morphology have been recognized for their importance in defining its biomechanical potential5: (1) muscle fiber length is related to the potential range of physiologic excursion of the tendon and muscle, (2) the physiologic cross-sectional area of a muscle is proportional to its maximum tension potential, and (3) physically, the product of the force and distance is work; therefore, the muscle mass or volume is proportional to its work capacity. In addition, potential force generation is further regulated by the velocity of shortening or lengthening of the muscle and, as is well known, its length at the time of contraction. Usually, an optimum length can be found for generating maximum contractile force. The arrangement of the muscle fiber architecture further influences the characteristics of the muscle contraction.8 It has been demonstrated that parallel muscle fibers produce a
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Biomechanics of the Wrist and Hand
Figure 6b.4 (Left) Tendon excursion and moment arm of the five wrist motor tendons during flexion/extension motion. (A) Tendon excursion. The wrist joint was moved from full flexion to full extension passively. (B) Moment arms calculated from A. The flexors and extensors show the different directions of the moment arm: extensors show the plus, and flexors show the minus. (Right) Tendon excursion and moment arm of the five wrist motor tendons during radial/ulnar deviation. (A) Tendon excursion. The wrist joint was moved from radial deviation (R.D.) to ulnar deviation (U.D.) passively. (B) Moment arms calculated from A. The ulnar side tendons show the plus moment, and the radial side tendons show the minus moment. ERCB, extensor carpi radialis brevis; ECRL, extensor carpi radialis longus; ECU, extensor carpi ulnaris; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris. (From Horii E, An KN, Linscheid RL: Excursion of prime wrist tendons. J Hand Surg 18(1):83-90, 1993.)
length-tension curve with maintained force throughout a wider range of excursion than do muscles with a shorter fiber pennate structure, which produce sharply peaked curves. The index of muscle architecture, defined as the ratio of muscle fiber length to muscle belly length, has been used to define such characteristics. The orientation or constraint of muscles or tendons crossing a joint determines the characteristics of excursion and the moment arm. In general, the larger the moment arm, the better the mechanical advantage for the same amount of tendon or muscle force. On the other hand, the larger the moment arm, the more tendon excursion expected for the same amount of joint rotation. The excursion of the tendon eventually affects the muscle length of contraction and ultimately determines the potential force generation according to the muscle length-tension characteristics. The size and shape of the object to be grasped determines the joint configuration of the thumb and fingers involved in
grasp function. The corresponding moment arms of both the intrinsic and extrinsic muscles at a particular joint configuration determine the mechanical advantage, tendon excursion, and corresponding muscle length. Therefore, as mentioned earlier, the size and shape of the object are important considerations in determining the power and strength of the grasp. Furthermore, the extrinsic muscles of the fingers and thumb originate from the forearm. Wrist joint motion therefore creates excursion of these tendons and modifies the muscle contraction characteristics because of the length-tension relationship. Thus grasp power and strength are regulated by wrist joint configuration as well. Because of the relatively smaller moment arms or mechanical advantage of the muscles and tendons across the joints as compared with those of externally applied forces at the tip of the digits, the muscle force required to balance grip or pinch functions is much higher. For example, in the tip and pulp pinch
Chapter 6b
function, the forces of the flexor profundus and sublimis are about one to two times the force at the tip of the digits. The associated forces in the intrinsic muscles are in the range of 0.5 to 1.5 times the applied forces.2,3 Accordingly, with such a magnitude of muscle and tendon forces, the compressive and shear forces across the finger joints are quite significant (Fig. 6b.5).
●
Force Through Wrist Carpal Joint
CX2 = 2.7
CX4 = 4.9 A=1 CZ6 = 0.2
FORCE THROUGH WRIST CARPAL JOINT When the hand is used, the wrist joint encounters a tremendous amount of force. The distribution of the forces among the carpal bones has great potential for injury to the associated bone and soft tissue. Cumulative trauma with compression of the lunate, for example, has been thought to result in avascular necrosis of the lunate (Kienböck disease). It has been postulated that excessive and uneven loading is experienced by the lunate between the lunate fossa of the radius and the compressible triangular fibrocartilage of the ulna. The overall force transmitted from the proximal row of carpal bones to the distal radioulnar joint has been examined by numerous investigators. Although the findings have not been in complete agreement and probably depend on the measurement technique, trends of certain important characteristics have been quite consistent. On average, 15% to 20% of axial wrist joint force is transmitted by the distal end of the ulna, and 80% to 85% is transmitted through the radius in the neutral position (Fig. 6b.6A).7
CX6 = 3.9
CY6 = 2.3
Figure 6b.5 Resultant joint forces during tip pinch function of one unit force, that is, A = 1. Forces represent the actions of the proximal segment applied onto the distal segment crossing the joint. CX, joint compressive joint force; CY, joint dorsal shear force; CZ, joint radial shear force. (From An KN, Cooney WP III: Biomechanics, section II: the hand and wrist. In BF Morrey, ed: Joint replacement arthroplasty. New York, 1991, Churchill Livingstone International, pp. 137-146.)
Figure 6b.6 (A) Each arrow represents the cumulative compressive force vector between adjacent bones and between the carpal bones and distal ends of the radius and ulna. These joint compressive forces or pressures within the carpus are calculated by this model when all the joints and ligaments are intact and axial loads are applied along the metacarpals. (B) Predicted displacements of the carpal bones under the loading condition shown in A. Slight ulnar translation is present as a result of a component of force tangential to the radial articular surface. Carpal bone displacement must be considered when the concentration of the force vector across articular surfaces is analyzed. The dotted line represents the unloaded position and the solid line represents the loaded position of the carpus: S, scaphoid; L, lunate; Tq, triquetrum; Tr, trapezium/trapezoid; C, capitate; H, hamate; R, radius; U, ulna. (C) Each arrow represents the calculated tension for the different carpal ligaments under the same loading condition: 1, palmar radiolunate ligament; 2, dorsal radiotriquetral ligament; 3, palmar radiocapitate ligament; 4, palmar capitatotriquetral ligament; 5, dorsal scaphotriquetral ligament; 6, palmar/dorsal hamatocapitate ligaments; 7, flexor retinaculum. (From Horii E, Garcia-Elias M, Bishop AT, Cooney WP, Linscheid RL, Chao EY: J Hand Surg Am 15A(3):393-400, 1990.)
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The effect of joint position and forearm rotation on the percentage of load transmission across the radius and ulna has also been recognized. With the wrist in the neutral position, at the midcarpal joint 30% of the total force was transmitted through the scaphotrapezial joint, 19% through the scaphocapitate joint, 31% through the lunocapitate joint, and 21% through the triquetrohamate joint. With the wrist loaded, the carpal bones translate in the ulnar direction down the inclined slope of the distal end of the radius (Fig. 6b.6B), and tensions in the intercarpal ligaments are observed as well (Fig. 6b.6C). Interaction of the carpal bones is conceptually analogous to a Rubik’s cube in which motion in one segment directly affects the position of another.
POSTTRAUMATIC INJURY Dobyns et al6 introduced the concept of traumatic carpal instabilities, and many reports have described their clinical features, treatments, and long-term consequences. The most common type of carpal instability is the dorsal intercalated segmental instability (DISI). Although many reports describe the anatomy and function of the volar ligaments of the wrists, only recently has the anatomy of the dorsal ligaments been better detailed and their function discussed. Most articles, which describe the pathomechanism of SL instability (SLI), concentrate on the scaphoid instability. However, there has been relatively little information about lunate instability and no clear explanation of the anatomic differences between dynamic and static SLI. Studies suggested that the DIC ligament is important in maintaining the carpal alignment of both the scaphoid and lunate.19 When the DIC and the SL interosseous ligaments were disrupted from the scaphoid but the DIC was still attached to the lunate, the resulting carpal instability demonstrated a flexed posture of the scaphoid and a widened SL gap, but only when the hand was loaded. This was comparable to a clinical dynamic SLI. When the DIC ligament was also disrupted from the lunate, the resulting instability demonstrated a flexed posture of the scaphoid and a widened SL gap in both loaded and unloaded conditions. Furthermore, when the DIC was detached from the lunate, the latter changed position to an extended posture, also in both loaded and unloaded conditions. This was comparable with a clinical static SLI with DISI. There was no apparent effect or further destabilization of the scaphoid or lunate resulting from disruption of the lunotriquetral interosseous ligament. The existence and progression of a dynamic SLI to a static SLI with a DISI deformity resulting from SL dissociation is well accepted in the clinical setting. To date, however, there has not been any detailed anatomic explanation and/or example of what the causes and the differences are between a dynamic SLI and a static SLI with DISI. The anatomic and mechanical integrity of the DIC ligament appears to play a significant role in SL stability and in determining whether the SL dissociation develops a dynamic or a static instability and DISI deformity. It is, of course, uncertain whether or not the progressive stages of instability simulated in these studies reflect actual clinical injury patterns. These results nevertheless propose that the treatment of the SLI should address not only the SL interosseous
With OA
Without OA Radiographic TT inclination
A
B
Figure 6b.7 (A) Radiographic measurements in the scaphoid axial view. Radiographic trapezium-trapezoid (TT) inclination is an angle formed by a line running axially through the 3rd metacarpal and another line running from the dorsal to the palmar articular edges of the proximal trapezium and trapezoid surfaces. (B) TT inclination is associated with increased osteoarthritis (OA).
ligament but also the DIC ligament at both its scaphoid and lunate attachments.10,19 The second most common site of degenerative changes in the wrist is scaphoid trapezium trapezoid degeneration. The etiologic factors in the development of degenerative changes in the STT joint are still unclear; studies have suggested, however, that degenerative changes are associated with scaphotrapezial ligament tears and increased trapezium-trapezoid inclination (the degree of coverage by the facets of the trapezium and trapezoid over the distal pole of the scaphoid) (Fig. 6b.7).12 Fractures of the scaphoid (the most commonly broken carpal bone) are difficult to treat because of its complex threedimensional shape and oblique orientation. Fractures of the proximal pole of the scaphoid have been associated with increased pressure and degenerative changes in the radius under its distal pole. Whether the fracture line passes distal or proximal to the dorsal apex of the ridge of the scaphoid (where the DIC ligament and the dorsal component of the SL interosseous ligament attach) appears to determine the likelihood of subsequent DISI deformity and the pattern of degenerative changes, if the fracture progresses to a scaphoid nonunion.11 In the volar type, the distal fragment displaces volarly with respect to the proximal fragment, and in the dorsal type, the distal fragment displaces dorsally.
SUMMARY Work-related injuries of the hand commonly occur. The nature of hand function places a tremendous amount of tension and repetition on the tendons and intrinsic muscles. Although tension may not be high enough to cause great damage, it can create compressive and frictional forces on the tendons and adjacent tissues around the pulley, bony surface, or other soft tissues. These compressive and friction forces can potentially cause cumulative trauma disorders of the bone and soft tissue.
Chapter 6b
REFERENCES 1. 2. 3.
4. 5. 6. 7.
8. 9. 10.
An KN, Berger RA, Cooney WP: Biomechanics of the wrist. New York, 1991, SpringerVerlag. An KN, Chao EY, Cooney WP, Linscheid RL: Forces in the normal and abnormal hand. J Orthop Res 3:202-211, 1985. An KN, Cooney WP III: Biomechanics. Section II: The hand and wrist. In BF Morrey, ed: Joint replacement arthroplasty. New York, 1991, Churchill Livingstone International, pp. 137-146. An KN, Ueba Y, Chao EY, Cooney WP, Linscheid RL: Tendon excursion and moment arm of index finger muscles. J Biomech 16:419-425, 1983. Chao EYS, An KN, Cooney WP, Linscheid RL: Biomechanics of the hand. A basic research study. Singapore, 1989, World Scientific. Dobyns JH, Linscheid RL, Chao EY, Weber ER, Swanson GE: Traumatic instability of the wrist. In A.A.O.S. 1975. St. Louis, MO, 1975, C.V. Mosby, pp. 182-199. Horii E, Garcia-Elias M, Bishop AT, Cooney WP, Linscheid RL, Chao EY: Effect on force transmission across the carpus in procedures used to treat Kienböck’s disease. J Hand Surg Am 15A(3):393-400, 1990. Kaufman KR, An KN, Chao EYS: Incorporation of muscle architecture into muscle length-tension relationship. J Biomech 22:943-948, 1989. Lin GT, Amadio PC, An KN, Cooney WP: Functional anatomy of the human digital flexor pulley system. J Hand Surg Am 14A:949-956, 1989. Mitsuyasu H, Patterson RM, Shah M, Buford W, Iwamoto Y, Viegas SF: Role of the dorsal intercarpal ligament in dynamic and static scapholunate instability. J Hand Surg 29(2):279-288, 2004.
11.
12.
13.
14. 15.
16.
17.
18.
19.
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References
Moritomo H, Viegas SF, Elder KW, et al: Scaphoid nonunion: a three dimensional analysis of patterns of deformity. J Hand Surg 25A(3):520-528, 2000. Moritomo H, Viegas SF, Nakamura K, Patterson RM: The scaphotrapezio-trapezoidal joint: Part 1. An anatomic and radiographic study. J Hand Surg 25A:899-910, 2000. Nakamura K, Beppu M, Patterson RM, Viegas SF: Motion analysis in two dimensions of radial-ulnar deviation of type I versus type II lunates. J Hand Surg 25A:877-888, 2000. Nakamura K, Patterson RM, Moritomo H, Viegas SF: Type I vs. type II lunates: ligament anatomy and presence of arthrosis. J Hand Surg 26A:428-436, 2001. O’Driscoll SW, Horii E, Ness R, Cahalan TD, Richards RR, An KN: The relationship between wrist position, grasp size, and grip strength. J Hand Surg 17:169-177, 1992. Patterson RM, Nicodemus CL, Viegas SF, Elder KW, Rosenblatt J: High speed, three dimensional kinematic analysis of the normal wrist. J Hand Surg 23A(3):446-453, 1998. Stegink Jansen CW, Simper VK, Stuart HG Jr, Pinkerton HM: Measurement of maximum voluntary pinch strength: effects of forearm position and outcome score. J Hand Ther:16:326-336, 2003. Viegas SF, Patterson RM, Hokanson JA, Davis J: Wrist anatomy: incidence, distribution and correlation of anatomy, tears and arthritis. J Hand Surg 18A:463-475, 1993. Viegas SF, Yamaguchi S, Boyd NL, Patterson RM: The dorsal ligaments of the wrist: anatomy, mechanical properties, and function. J Hand Surg 24A(3):456-458, 1999.
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6c
Functional Evaluation of the Wrist and Hand Jane Bear-Lehman
MULTIDIMENSIONAL ASSESSMENT PROCESS FOR THE WRIST AND HAND A comprehensive multidimensional assessment plan for the wrist and hand requires the selection and use of many different types of evaluation instruments to measure the outcomes of the patient’s health status, impairment level, functional limitations, and disability status. Assessment focuses on the outcome levels for those variables that can change because of time, treatment, or disease.27 Often generic or condition-specific self-report questionnaires are now selected to measure health, function, and disability status from the patient’s perspective, and performancebased instruments known as the tools of our trade still provide data about functional impairment and limitations. Clinical assessment of the wrist and hand is both a quantitative and a qualitative process. Its aim is to help the clinician construct and then monitor the effectiveness of the treatment plan, the progression or the prevention of the disease or injury, and the health status over time. Treatment of a patient who has sustained a musculoskeletal occupational injury of the wrist and hand focuses on helping the patient achieve maximal function of both body and limb and regain independence in ordinary activities of daily living while restoring health status. Occupational musculoskeletal wrist and hand injuries can result from direct or indirect trauma in the workplace. The injury affects the musculoskeletal system, which includes the bone, its joints, and their related structures: muscles, tendons, ligaments, nerves, and arteries. Direct trauma injuries are usually a medical emergency; they have a date, time, and place of injury and may result from a fall in the workplace or adverse physical contact with tools or machinery. Indirect trauma is microtrauma to the muscles, tendons, ligaments, nerves, or arteries that persists and develops over time. The physical performance assessment of a patient with direct or indirect trauma to the wrist and hand focuses specifically on the injured and adjacent body parts as appropriate for the medical and surgical stage of recovery; these results are compared with function of the uninjured limb, if available. Several performance-based instruments that produce quantitative measurements are used in the therapeutic setting to assess the functional impairment level, including range of motion (ROM), muscle performance, edema (limb size), and sensation; functional limitations are assessed using instruments that measure activities of daily living, dexterity, and physical capacity. This chapter reviews the performance-based measures for the wrist
and the hand that are considered tools of the trade, with attention to each instrument’s stage of development and achieved reliability and validity. Although it is assumed that the use of reliable and valid tests increases the statistical probability for making correct clinical decisions and predictions about performance potential, we are cautioned to not rely exclusively on these functional impairment or functional performance quantitative data alone. Qualitative data in terms of behavioral response, such as personal attitude and response to pain, fear, and loss of control, often influence the quantitative wrist and hand functional evaluation results.10 Furthermore, in today’s clinic it is essential to have outcome documentation, including information about the patient’s health status, function, and overall satisfaction level, to understand the different kinds of results.3 The clinical assessment of a patient with a musculoskeletal disorder affecting the wrist and hand follows a biomechanical frame of reference to evaluate the results or outcomes. The problems are identified by gathering and then synthesizing subjective, observational, and objective information about the patient to determine the quality of the result and the level of satisfaction.3 This information is derived from the patient, the clinician’s observation of the patient visually and through touch (palpation), and the outcome measures the patient achieves on administered self-report and performance-based tests. The assessment relies on the patient’s effort and voluntary cooperation with clinical stimuli, inquiries, and directives. To begin the assessment, the clinician gathers a history from the patient’s perspective about the nature and the course of the injury, prior medical and therapeutic attention sought, and success of these interventions. This report from the patient’s perspective is compared for congruity with the written medical history. The clinician poses many questions about life-style adjustment, to document the alterations but more so to appreciate the patient’s ability to recognize, understand, and function within the restrictions imposed by the present physical problem(s). Patients are therefore asked to describe how the impact of the injury has affected their life-styles, namely, the changes in ability to perform ordinary activities of daily living at home, at work, and at leisure.25 The course, location, duration, and type of pain are addressed through standardized questionnaires, such as the McGill Pain Profile or the Visual Analog Scale, to detect painful reaction, patterns about the patient’s pain, and methods to control it.11,30 Outcome self-report instruments are administered to measure health status and function; some of the measures include information about pain level, performance of activities of daily living, and satisfaction level. Generic or condition-specific scales in self-report instruments are selected to help standardize the functional assessments. These tools provide the clinician, the patient, and others with basic functional information that is meaningful and helps serve as a screen at the outset of treatment.3 The SF-36, a widely used generic scale, measures health status in 36 items addressing key elements such as physical function, physical role, bodily pain, general health, social function, and emotional role.40 Many suggest that when assessing a patient with a wrist or hand injury, the highly regarded SF-36, with its impressive reliability and validity, should be combined with a more condition-specific instrument, of which several are available for selection.8 Care in selection increases the quality of
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responsiveness and meaningfulness of the information. Attention should be directed to condition-specific regional self-report tests on function and health status such as the DASH (disabilities of the arm, shoulder, and hand), the Michigan Hand Questionnaire, or the Upper Body Musculoskeletal Assessment for patients who have upper limb injuries.8,15,24 More focused questionnaires are appropriate for specific conditions, such as the Patient-rated Wrist Evaluation Questionnaire for those who have sustained a wrist fracture and the Carpal Tunnel Syndrome Questionnaire for individuals recovering from that syndrome. When matched with the patient who has the targeted diagnosis, these highly specific instruments are more responsive than the DASH or the SF-36.3,27 In the biomechanical component of the clinical hand and wrist assessment, the clinician observes the patient’s posture and attitude of the injured wrist or hand and its adjacent structures to answer the following questions: Is the patient favoring a posture to protect the injured part from environmental contact through upper extremity flexion and adduction? Is there biomechanical alteration in the body to compensate for the poverty of movement or the increase in pain? Is there symmetry in size and shape between the injured and uninjured wrist and hand? Does the body move symmetrically? What are the preferred postures during static positions such as sitting? What are the transition patterns, that is, moving from sitting to standing, and the dynamic patterns of movement such as walking? What is the quality of movement at the injured site and in the adjacent structures? Is there a change in coloration at the injured site; does the coloration vary? Palpation of the skin gives the clinician more information about the skin’s temperature, the presence of nodules, and the tightness of muscle-tendon units. Physical or anatomic measurement is a continuous and ongoing process; it is carefully coordinated and monitored with the stage of healing, the plan for movement during healing, and the trajectory of recovery. Physiologic changes can and do occur quite rapidly during the acute stage.18 Objective measures provide the treating clinician with information about the effectiveness of a given treatment, confirm the need to continue with a given treatment regimen, or signal the need for revision if the progress or response is not as anticipated. The data are used to justify the need for continuation of treatment or the consideration of other therapies.
CLINICAL ASSESSMENT OF THE MUSCULOSKELETAL SYSTEM Physical performance measurements provide the clinician with information on the functional impairments affecting the wrist and the hand. These measurements rely on familiar hand care tools of the trade; some of the tools or instruments, such as goniometers for measuring active or passive range of motion, have remained the same. Others have been further developed to improve the reliability of the measurement: Hydraulic pinch meters have replaced spring gauges, for example. Tools have also been redesigned to improve the quality of measurements, as in the continual instrument development for the measurement of light-touch deep pressure sensory response or two-point discrimination testing. Functional impairment requires the assessment
of the wrist and the hand for actual measures of ROM, edema, muscle performance testing, sensation, and pain, as follows.
Range of motion Since the 1940s, clinicians have been reporting their use of the goniometric system to obtain accurate information about patients’ joint status and movement capacity. Although technically not a standardized assessment tool, the universal goniometer is the most widely selected tool for measuring joint ROM. The American Academy of Orthopaedic Surgeons guide is used as a reference for normative values.4 In terms of reliability, Hamilton and Lachenbruch20 found no difference in the results of determining joint angles with different goniometers. The reliability of readings by the same tester over time has shown a 5-degree error when measuring joints in the wrist or the hand. The method of recording continues to follow the Academy guideline in which minus sign notation is used to show an extension limitation and a plus sign indicates hyperextension. The American Society for the Surgery of the Hand accepted the method of reporting goniometric scores in terms of the total arc of movement at a given joint or a related series of joints. Use of the arc measurement system for the digits is reported as total active movement and as total passive movement for the summation of the angles of the three joints in each digit.14,18 That is, the total active movement or total passive movement represents the summation of the amount of movement available in all three joints, the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal, with full ROM yields a score approximating 260 degrees. This composite measurement does not isolate the individual joint that is creating the deficit, but it is suited for graphic representations of the patient’s performance over time; it is very useful after a tendon or nerve repair. ROM measurements are conducted on the adjacent joints in the acute stage of recovery; deficits in the adjacent joints that were not present before the injury are remediated in therapy. Depending on the nature of the injury and the medical or surgical protocol, measurements may be taken for active or passive ROM at the injury site immediately or may be deferred until the integrity of the joint or the surrounding tissue allows a measurement. ROM assessment of the injured joints depends on the type of protection and stabilization used for healing. If complete rest of the injured region is required, measurements are delayed until movement is permissible. If controlled movement at the injured site is allowed, the clinician measures the type of movement (active or passive) within the range allowed and restricts movement beyond the prescribed arc.
Edema Trauma or surgery is frequently followed by an abnormal accumulation of fluid in the interstitial spaces of tissues, resulting in an increase in limb size. This edematous state limits ROM and, ultimately, function. Measurement of wrist and hand size circumferentially with a tape measure is often done at three locations: proximal to and distal from the edematous part and over the edematous part. To allow for a more valid comparison of
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sequential measurements, anatomic landmarks are used as reference points for placement of the tape measure. Placement and tension of the tape measure or finger gauge affect intertester and intratester reliability. In the past, clinicians have used jewelers’ rings to help reduce the measurement error related to tension on the tape measure. Now clinicians rely on the Gulick tape, which has a unique spring gauge, or the finger circumference gauge for more consistent measurements for repeated measures (Figs. 6c.1 and 6c.2). Because edema may be not localized in a digital segment but more generalized over the hand and arm, a volumeter method is preferred to accurately measure edema changes in the hand and wrist (Fig. 6c.3). The volumeter, based on Archimedes’ principle of water displacement, is used to measure composites of hand mass. Waylett and Seibly41 documented 10-ml test-retest reliability when the manufacturer’s guidelines are followed.23 Normative values for any of these measures are not available; the contralateral side is used as the approximate normal value for that patient. Because hand-size changes may be attributed to factors other than edema, such as normal asymmetry or muscle atrophy in the affected limb from disuse, care must be taken regarding generalization and interpretation of the findings.
Muscle performance testing Muscle testing is used to evaluate the level of nerve injury and nerve regeneration and preoperatively to determine potential donors in tendon transfer surgery. The manual muscle test designed by Lovett and Martin26 is a screening device that relies on the external forces of gravity and resistance to assess muscle strength.
Figure 6c.1 Gulick tape measure has a unique spring gauge to provide consistent measurements. (NC70170-95: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
Figure 6c.2 Finger circumference gauge is used for consistent measurement in inches or centimeters. (NC70157-95: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
The strength of muscle contractions can be measured clinically by means of spring scales, dynamometers, weights, or manual resistance. Manual resistance is added to voluntary maximal contraction once it has been established that the muscle exertion and the applied resistance will not adversely affect the healing bone, joints, and related structures. There is no agreement regarding whether isometric or isotonic contraction should be used in muscle testing or whether testing scores are best derived from the muscles’ isometric contractibility under load at the end of the range, which is often chosen as the point for applied resistance.22 Few discrepancies are found in
Figure 6c.3 Hand volumeter is used to measure changes in hand size. (NC70310.00: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
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manual muscle testing procedures. Hislop et al21 used a gravityeliminated position to test metacarpophalangeal joint extension, whereas Kendall et al22 did not distinguish the effect of gravity in the hand. The scoring methods of Lovett and Martin26 and Brunnstrom and Denner13 continue to be used: 0 (zero), 1 (trace), and 2 (poor) represent test results in the gravity-eliminated posture; 3 (fair) uses the external force of gravity; and 4 (good) and 5 (normal) add the dimension of resistance. Overall, reports of reliability are descriptive. No predictive validity has been established for grip and pinch scores, although many are hypothesized, nor is hand function predictive. Functional hand strength is measured by grip and pinch tests. In the case of a distal forearm, wrist, or hand fracture, measurements are deferred for at least 2 to 4 weeks after the removal of immobilization. Hand strength measurement is the most common standardized assessment using hydraulic dynamometers. Figure 6c.4 shows the use of the Jamar hydraulic dynamometer to measure hand-grip strength. Pinch patterns are measured using the hydraulic pinch meter (Fig. 6c.5). Spring pinch gauges are not recommended because they cannot be calibrated and have yet to prove as reliable or consistent in measuring as
Figure 6c.5 The hydraulic pinch gauge gives accurate and consistent results, and like the Jamar dynamometer it can be calibrated. (NC70141_03: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
the hydraulic instruments. If regularly calibrated, the hydraulic hand strength instruments have been shown to be reliable and produce consistent measurements.7,18 Both grip and pinch hand strength instruments allow for readings in kilograms-force and pounds-force. The literature shows a variety of test procedures that can have an impact on interrater and intrarater reliability, as well as on its normative data pool.29 The American Society for the Surgery of the Hand and the American Society of Hand Clinicians accept the seated posture with humeral adduction and neutral humeral rotation, the elbow flexed to 90 degrees, and the forearm and wrist in neutral position as the desired body posture for grip testing.28 Norms have been established for age 5 to adulthood. Healthy adult grip strength values for the five handle positions, when providing full voluntary effort, yield a normal bell-shaped curve.36 The first position, the closest, is the least advantageous because it relies primarily on the ulnar nerve-innervated hand intrinsics, whereas the widest or fifth position relies on the median nerveinnervated long finger flexors. Middle-range handle positions require the intrinsic and extrinsic musculature to work together. A patient without neural or tendon damage who has a flattened curve may be suspected of providing submaximal voluntary effort. The traditional pinch patterns of lateral, palmar (also known as tripod or three-jaw chuck), and tip pinch are reported as the average of three trials for each type of pinch. The normative data tables are described on the basis of age and gender for both grip and pinch. Three test trials are recorded for each grip and pinch pattern tested. The mean (average of the three), the standard deviation, and the coefficient of variation (standard deviation/average) are computed to monitor the consistency or sincerity of effort.32,33,36
Sensation Figure 6c.4 The handheld Jamar dynamometer records grip strength in kilograms-force or pounds-force.
The hand is a complex organ whose function depends on harmony between sensory and motor abilities.16 Sensory testing
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can frequently identify sensorineural changes earlier than traditional motor examination. Studies have shown, for example, that in median nerve entrapment at the carpal canal level, sensory changes precede motor changes. Clinical tests of vibration and Semmes-Weinstein monofilament testing show changes earlier than electromyographic studies because the latter does not show the process of change. Many of the tools used clinically to test sensation are being revised and improved, and because of the changes offered by microsurgery, more patients now have greater potential to achieve sensory results of higher quantity and quality. Sensory testing of a patient with a wrist and hand injury addresses the ability to perceive light touch and deep pressure, to discriminate touch, and to detect vibration. To monitor the progress of a patient’s sensory status, particularly if a neural injury is suspected, it is advisable to use instruments that yield ordinal rather than nominal data. Early methods to test light touch and deep pressure called for the use of a cotton ball or a cotton-tipped applicator. This form of testing yields the results that the patient perceived the touch or is normal, may not have perceived or appreciated the stimulus fully or is impaired, or did not perceive the stimulus at all or is absent. This hierarchy represents an ordinal-level data system ranging from normal to absent response levels; the increment between the values is not known, nor is it equal. Abnormal results need to be monitored during the course of treatment. It is expected that sensitivity over scars and pin tracks is heightened. The deep pressure-to-light touch interval hierarchy for sensation in the hand resulted from the findings of von Frey,39 a surgeon who had a passion for learning about sensation and a love of horses. von Frey discovered that some of his patients could detect only the sensation of thicker horse hairs when applied to their skin surfaces, and as they healed, they could begin to feel finer horse hairs. The horse hairs that were first used are now 20 calibrated nylon monofilaments graded in diameter and individually attached to Plexiglas handles. The amount of force transmitted is related directly to the diameter of each filament, which bends at a specific force controlling the magnitude of the touch-pressure stimulus.9 Weinstein42 developed a smaller more portable version of his original test, the Weinstein Enhanced Sensory Test (WEST), for ease of use in the clinic. Now clinicians use either the WEST or the Touch-Test Sensory Evaluators. The latter are individually calibrated within a 5% standard deviation of the predetermined targeted force. No other commercially available “monofilament type” testing device meets this scrutiny (Fig. 6c.6). The larger set of 20 still provides greater specificity for those patients who require it. To test for discriminatory touch sensation, the static or stationary two-point discrimination instrument continues to be challenged. The original Weber two-point discrimination instrument’s sliding scale allowed for adjustment of the spacing between the two points; however, the adjustment often did not allow the same precision as a tool with fixed points. Some practitioners open up paper clips to approximate distances, which leads to variability in spacing and uneven pressure between points. The two-point discrimination instrument, the Diskcriminator, designed by Dellon et al,17 controls for the precision between points and provides even application when two points are applied, and the
Figure 6c.6 The Touch-Test Sensory evaluators (Semmes-Weinstein monofilaments) are individually calibrated and accurately measure light touch-deep pressure. (NC12757: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
Touch-Test Two-Point discriminator provides the opportunity for clinicians to have all points of measure on a single disk (Fig. 6c.7). Studies show that the amount of pressure offered when two points are applied can be very different from that of just one. The ability to perceive vibratory stimuli is clinically valuable when the patient has undergone nerve repair or when nerve compression or a peripheral neuropathy is suspected. The 30-Hz and 256-Hz tuning forks continue to be used to test for vibratory response. Clinical studies have proposed that both the 30-Hz and the 256-Hz tuning forks be used because it is believed
Figure 6c.7 The Touch-Test Two-Point discriminator allows for two-point discrimination testing in one unit. (NC12776A: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
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that each elicits the response of an individual sensory neurite receptor. The 30-Hz fork is believed to evoke the response of the Meissner corpuscle and the 256-Hz fork from the Pacinian corpuscle.16 Whether the prong or the stem should be applied to the skin surface is often debated; in either event, the lack of control of amplitude and variability in technique make the reliability of the test inconsistent.7 Furthermore, the patient may hear the sound of the tuning fork before perceiving it on the skin surface, confounding the response. Only ordinal data are gleaned from this form of testing. A vibrometer with a fixed frequency level provides a result measured in microns of motion at 120 c/s (Fig. 6c.8). The data are interval and therefore quantifiable, allowing for specific tabulation of progress. The raw score is a logarithmic function of probe displacement measured in volts that is converted mathematically into microns. Normal expected values of the displacement for skin surface are presented in an anatomic diagram and table format. This instrument requires the use of an electrical outlet and is not as readily portable as other hand assessment tools that fit into a laboratory coat pocket.
Pain Observed during the course of the assessment, pain can be monitored over time in several ways. Pain is measured as part
of the health and function status at the outcome evaluation by the use of the McGill Pain Questionnaire or the Visual Analog Scale,11,30 and it is monitored as treatment progresses. The patient is asked to describe the type, location, and threshold of pain perceived before, during, and after each therapy session. Perception of pain varies from one patient to the next with the same injury as well as for the same patient over time. The clinician must also observe and address signs that may be causing pain, such as a constrictive dressing, cast, or splint or an infection. Pain may and often does occur at the onset of therapy; this form of pain is localized and should subside within 2 hours of the session.
FUNCTIONAL ASSESSMENT OF THE MUSCULOSKELETAL SYSTEM Critical to the assessment process is to appreciate wrist and hand use in terms of functional limitations that result from the injury and to monitor change. Information about functional limitations can be derived from the self-report questionnaires such as the generic SF-36, the condition-specific DASH, or the diagnosis condition-specific Patient-Rated Wrist Evaluation. Performance tests are administered, and the scores are compared with the normative tables, if available. The performance scores can be compared also with the self-report questionnaire findings. Less often, clinicians may consider direct observation performance measures for activities of daily living; however, when this occurs, it is usually to resolve a specific concern or clarify a patient’s self-report.
Information processing
Figure 6c.8 The Bio-Thesiometer Vibrometer measures the threshold of appreciation of vibration. (Courtesy of Bio-Medical Instrument Company, Newbury, OH.)
The patient comes to the medical setting mainly because of pain, fear, and disability.6 A satisfactory result depends not only on the technical skills of the team but also on the team’s ability to communicate, engender confidence, and fully understand and explain the problem to the patient.12 It is necessary for the clinician to look at the process of therapy and the patient’s response to it. The clinician helps the patient by designing a learning environment that emphasizes the salient traits and the characteristics of the problem to be solved or the condition to be learned. One method is to engage the patient in metacognitive experiences, that is, conscious thinking and awareness of feelings that accompany and pertain to the problem-solving task.1 Flavell19 defined metacognitive knowledge as information or beliefs about the course and outcome of the cognitive enterprise in three areas of cognitive awareness: person, task, and strategy. Every patient has a different level of cognitive awareness and a variety of beliefs, feelings, understanding of goals, and strategies for problem solving. In therapy, practice or instructional programs are systematically used with a focus on the process rather than the content.35 Each task is analyzed relative to its repetition, imitation, and substitution. The training is assessed for the patient’s need to have cues or anchors and intermodal training and for the patient’s performance in a novel or new learning situation. How the patient accepts and responds to the information that has been shared is viewed in more than just a physical sense. Fear, pain, or side effects of medications often intervene in the patient’s ability to orientate to the therapy situation and to
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focus attention (alertness); this also affects the patient’s ability to learn. A patient in pain may find one voice instrumental in helping to learn the new way of moving the wrist. A verbal, visual, or kinesthetic voice (cue) from the clinician may be sufficient as the patient learns to move the wrist and hand again. Two voices, visual and verbal, may be needed, or the two voices may bombard the patient’s ability to concentrate if given at the same time because of the high threshold of pain. By observing how the patient learns to move again and how feedback is obtained and used,2 the clinician determines whether the patient is reliant on others for direction and guidance to perform tasks or is selfdirected and self-regulated.35 It is important to know whether the patient can detect an error in movement alone, how the error is corrected, and what kind of reinforcement is required. The clinician also observes the patient’s ability to cope with the injury. After guidance in how to select and terminate activities that correspond to the patient’s stage of healing, the clinician observes how the patient follows such guidelines in performing ordinary daily tasks, in participating in rehabilitation, and in assuming societal and family roles. The patient is observed for the ability to adhere to safety precautions and exhibit selfcontrol in terms of physical limitations and reactions to pain.
Activities of daily living The quantity and the quality of the patient’s performance of activities of daily living are ascertained by interview. Information from the self-report health and functional status can be used or an additional inquiry may be conducted for more specific information as warranted. For problematic deficit areas, the clinician may observe the patient’s actual performance. Early in the healing process, when medical restrictions are in place as to the amount of movement or force allowed at the site of injury or the ability of the injured part to get wet, the patient must be assessed for methods of accommodation in activities of daily living.5 For patients with a wrist or hand injury, this may require an assessment of eating, personal hygiene, dressing, bathing, and communication. Adaptive methods and devices may be indicated temporarily to facilitate one-handed methods, such as using a rocker knife for cutting meat or a button-hook for fastening buttons, or the clinician might suggest purchasing precut or prepared foods. During the course of the rehabilitation program it is important for the clinician to guide the patient as to when and how the injured wrist and hand can be safely reintegrated into the performance of activities of daily living corresponding with the clinical progress. The first reintegration is in the performance of personal activities of daily living. When strengthening is introduced into the clinical program, the clinician needs to consider the patient’s need to perform such instrumental tasks, including those related to meal preparation, household management and shopping, and care of others. For many patients, work during the acute phase of recovery may not be possible due to extensive manual demands on the job, whereas others may not have a work interruption. For those who are working, the clinician identifies the components and demands of the patient’s job by interview and helps the patient assume those tasks that correspond to the achieved clinical status. For those unable to work, the demands essential to the
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patient’s job are delineated to develop the requirements for return to work and the goals for therapy. As treatment progresses, the patient’s performance level is reviewed and compared with the levels needed for safe return to work. The feasibility of meeting the physical demand levels in terms of essentially required dexterity, strength, or physical endurance are determined during the rehabilitation process.
Dexterity Commonly defined as skill and ease in using the hands, dexterity is considered a functional limitation when impaired. To assess manual dexterity or physical functioning efficiently, the examiner must select the standardized test that suits the patient’s abilities and needs. Most have a high index of reliability (greater than 0.75) and show good face and content validity; little has been done on concurrent validity or predictive validity, which is most needed for the clinical decision-making process.6 Predictive validity determines whether the patient, based on the performance on the test, is ready to return to work. Dexterity tests can be classified by their demand for fine to gross motor movement patterns, requirement of one hand or integration of both to perform the task, requirement of a tool for their administration, and length of time the test takes to perform. The Moberg Pick Up test can be classified as a sensory and dexterity test because it brings together the sensate and motor functions. This test is usually performed with unrestricted vision and with vision occluded, and the patient is timed as the familiar objects are scooped, handled, identified, and placed in a designated location. The Nine Hole Peg Test (Fig. 6c.9), the Purdue Pegboard (see Fig. 6c.10), the O’Connor Tweezer Dexterity Test, the O’Connor
Figure 6c.9 The Nine-Hole Peg Test quickly measures fine motor dexterity. (NC34547.d1: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
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Figure 6c.10 The Purdue Pegboard Test has four subtests: right hand placement, left hand placement, use of the hands in parallel, and, as shown, integrated use of the two hands on assembly.
Finger Dexterity Test, and the Crawford Small Parts Test are all examples of fine-motor dexterity movement patterns. However, the Nine Hole Peg Test and the Purdue Pegboard Test are short tests that do not provide information about endurance; the Purdue Pegboard Test does require the use of one hand as well as that of both hands in a parallel and in an integrated fashion, as shown in Figures 6c.9 and 6c.10. The O’Connor Tweezer Dexterity Test and the Crawford Small Parts Test both require the use of a small tool to handle and manipulate the test parts. The former requires the use of small tweezers, and testing is completed on the use of one hand at a time for all functions; the latter requires the use of tweezers or a screwdriver in one hand while the alternate hand is assistive. The Minnesota Manual Dexterity Test (Fig. 6c.11) and the Bennett Hand-Tool Dexterity Test assess gross motor function; the former requires the patient to handle the test items directly, whereas the latter requires the use of ordinary mechanic’s tools. Both allow for the direct use of both hands during some of the test components. Many of the Valpar38 Corporation Work Samples (VCWS) are well suited to assess precise finger and hand movements. In particular, the VCWS 1 small tools (mechanical) work sample38 is helpful in assessing the use of small tools in tight or awkward spaces requiring use of the hand(s) without direct visual monitoring. The outcome scores for manual dexterity performance are reported as the amount of time (the speed) that the patient required to perform the task, and the increments of time are compared with normal data based on age, gender, and occupation published in the test manuals. The clinician also reports the preferred prehensile patterns used during the course of the tasks and the control the patient had over performance. Observations of motor control are discussed relative to the patient’s safe use of the injured part, biomechanical alignment of the injured part relative to the body, postural accommodation of the body to the injured part, and quality of task performance. Qualities of concern include the patient’s ability to integrate both the injured hand or wrist and the principles of joint protection spontaneously into the dexterity pattern and the ability of the two hands to work together as a dominant and subdominant pair.
Figure 6c.11 The Minnesota Manual Dexterity Test measures eyehand-finger movement in two subtests: one-handed placement and twohanded turn and placement. (NC70030-96: Courtesy of North Coast Medical, Inc., Morgan Hill, CA.)
The patient is observed for safety relative to the injured part, him or herself, and others.
Physical capacity evaluation Most physicians and clinicians use a physical capacity evaluation to try to answer the question of whether a patient can safely return to work. The capacity to perform work may be directly related to achieved physical performance but is more complex due to the contribution of both philosophic and psychologic issues.34 Many sophisticated instruments are available to assist in the evaluation process, but the level of validity for these instruments is less than is often required. Performance on these systems is interpreted in a variety of ways, including MTM (motiontimes-measurement) standards, U.S. Dictionary of Occupational Titles Worker Qualification Profiles37 or U.S. Department of Labor O*NET.31 The theoretical model that is followed is Parson’s trait factor from the early 1900s in industrial engineering. The procedure is to identify the traits that the patient now has physically, behaviorally, and cognitively; to keep symptoms under control to work safely and effectively; and to match these to environmental factors, including the design of the work station, to determine safe maximum levels of functional work ability in the work force.
SUMMARY Success and satisfaction in rehabilitation of the wrist and the hand is measured by the patient’s ability to use the injured
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part spontaneously in usual, customary, and ordinary activities. Instruments that produce reliable and valid data assist in accountability for the assessment of upper extremity function and restoration of health status. The art of practice requires awareness and documentation not just of the patient’s quantitative wrist and hand dysfunction characteristics, but also of the qualitative ones. To move effectively and efficiently, the patient needs to learn again how to do so in a controlled rhythmic way. Today’s practice requires the clinician to use standardized assessments and report results or outcomes that are meaningful to the clinician, the patients, and all who have access to the information. Using an outcome model allows the clinician to understand what is happening to the patients who are treated.
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14.
Abreu BC: Evaluation and intervention with memory and learning impairments. In C Unsworth, ed: Cognitive and perceptual dysfunction: a clinical reasoning approach to assessment and treatment. Philadelphia, 1999, F. A. Davis, pp. 163-207. Abreu BC, Peloquin S: The quadraphonic approach: a holistic rehabilitation model for brain injury. In N Katz, ed: Cognition and occupation across the life span: Models for intervention in occupational therapy, 2nd ed. Rockville MD, 2005. AM. Occ Therapy Assoc. Amadio PC: Outcome assessment in hand surgery and hand therapy: an update. J Hand Ther 14:63-67, 2001. American Academy of Orthopedic Surgeons: Joint motion: method of measuring and recording. Chicago, 1965, The Academy. Appelby MA, Schkade JK, Gilkeson GE: Timing of ADL education with hand surgery patients. J Hand Ther 5:218-225, 1992. Bear-Lehman J: Factors affecting return to work after hand injury. Am J Occup Ther 37:189-194, 1983. Bear-Lehman J, Abreu BC: Evaluating the hand: issues in reliability and validity. Phys Ther 69:1025-1033, 1989. Beaton DE, Katz JN, Fossel AH, Wright JG, Tarasuk V, Bombardier C: Measuring the whole or the parts? Validity, reliability, and responsiveness of the disabilities of the arm, shoulder, and hand (DASH) outcome measure in different regions of the upper extremity. J Hand Ther 14:128-146, 2001. Bell-Krotoski JA: Sensibility testing with Semmes-Weinstein monofilaments. In J Hunter, E Mackin, A Callahan, eds: Rehabilitation of the hand and upper extremity, ed 5. St. Louis, 2002, Mosby, pp. 194-213. Brand PW: The mind and spirit in hand therapy. J Hand Ther 1:145-147, 1988. Briggs M, Closs JS: A descriptive study of the use of the visual analog scales and verbal rating scales for the assessment of post-operative pain in orthopedic patients. J Pain Sympt Manage 18:438-446, 1999. Brown PW: The role of motivation in patient recovery. Conn Med 42:555-557, 1978. Brunnstrom S, Denner M: Round table on muscle testing. Annual conference of American Physiotherapy Association, Federation of Crippled and Disabled, New York, 1931. Cambridge-Keeling CA: Range-of-motion measurement of the hand. In J Hunter, E Mackin, A Callahan, eds: Rehabilitation of the hand and upper extremity, ed 5. St. Louis, 2002, Mosby, pp 169-182.
26. 27.
28. 29. 30.
31. 32. 33. 34.
35. 36. 37. 38. 39. 40.
41. 42.
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Chung KC, Pillsbury MS, Walters MR, Hayward RA: Reliability and validity testing of the Michigan Hand Outcomes Questionnaire. J Hand Surg 23A:575-587, 1998. Dellon AL: Evaluation of sensibility and re-education of sensation in the hand. Baltimore, 1981, Williams & Wilkins. Dellon AL, Mackinnon SE, Crosby PM: Reliability of two point discrimination measurements. J Hand Surg Am 12A:693-696, 1987. Fess EE: Documentation: essential elements of an upper extremity assessment battery. In J Hunter, E Mackin, A Callahan, eds: Rehabilitation of the hand and upper extremity, ed 5. St. Louis, 2002, Mosby, pp. 263-284. Flavell JH: Metacognition and cognitive monitoring: a new era of cognitive developmental inquiry. Am Psychol 34:906-911, 1979. Hamilton GF, Lachenbruch PA: Reliability of goniometers in assessing finger joint angle. Phys Ther 49:465-469, 1969. Hislop HJ, Montgomery J, Daniels I: Worthingham’s muscle testing techniques of manual examination, ed 7. Philadelphia, 2002, WB Saunders. Kendall FP, McCreary EK, Provance PG: Muscles: testing and function, ed 4. Baltimore, 1993, Williams & Wilkins. King TI: The effect of water temperature on hand volume during volumetric measurement using water displacement method. J Hand Ther 6:202-204, 1993. Kramer JF, Potter P, Harburn KL, Speechly M, Rollman GB, Evans D: An upper body musculoskeletal assessment instrument for patients with work-related musculoskeletal disorders: a pilot study. J Hand Ther 14:115-121, 2001. Law M, Cooper BA, Strong S, Stewart D, Rigby P, Letts L: Theoretical contexts for the practice of occupational therapy. In C Christiansansen, C Baum, eds: Occupational therapy enabling function and well-being, ed 2. Thorofare, NJ, 1997, Slack. Lovett RW, Martin EG: Certain aspects of infantile paralysis and a description of a method of muscle testing. JAMA 6:729-733, 1916. MacDermid JC: Outcome measurement in the upper extremity. In J Hunter, E Mackin, A Callahan, eds: Rehabilitation of the hand and upper extremity, ed 5. St. Louis, 2002, Mosby, pp. 285-296. Mathiowetz V, Kashman N, Volland G, et al: Grip and pinch strength: normative data for adults. Arch Phys Med Rehabil 66:69-74, 1985. Mathiowetz V, Kashmen N, Volland G, Weber K, Downe M, Rogers S: Reliability and validity of hand strength evaluation. J Hand Surg Am 9A:222-226, 1984. Melzack R, Mathiowetz V, Weber K, Volland G, Kashman N: Reliability and Validity of grip and pinch strength evaluations. The McGill pain questionnaire: major properties and scoring methods. Pain 1:265-276, 1975. O*NET on-line. Retrieved from http://online.onetcenter.org Schectman O: The coefficient of variation as a measure of sincerity of effort of grip strength. Part 1. The statistical principle. J Hand Ther 14:180-187, 2001. Schectman O: Using the coefficient of variation to detect sincerity of effort of grip strength: a literature review. J Hand Ther 13:25-32, 2000. Schneider LH: Impairment evaluation. In J Hunter, E Mackin, A Callahan, eds: Rehabilitation of the hand and upper extremity, ed 5. St. Louis, 2002, Mosby, pp. 297-307. Schwartz RK: Therapy as learning. Rockville, MD, 1985, American Occupational Therapy Association. Stokes HM: The seriously injured hand: weakness of grip. J Occup Med 25:683-684, 1983. U.S. Dictionary of Occupational Titles: Worker qualification profiles. Retrieved from www.oalj:dol.gov/libdot.htm Valpar Corporation Catalog. Retrieved from http://www.valparint.com von Frey M: Zur physiologie der juckempfindung. Arch Neurol Physiol 7:142, 1922. Ware JE, Kosinski M, Keller SD: SF-36 physical and mental health summary studies: a user’s manual. Boston, 1994, The Health Institute, The New England Medical Center. Waylett J, Seibly D: A study of the accuracy of a commercially available volumeter. J Hand Ther 4:10-13, 1991. Weinstein S: Fifty years of somatosensory research: from the Semmes-Weinstein monofilaments to the Weinstein enhanced sensory test. J Hand Ther 6:11-22, 1993.
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6d
Wrist and Hand: Treatment Options David M. Kalainov and Mark S. Cohen
Disorders of the wrist and hand are common in the work environment.23 Effective management frequently depends on a multidisciplinary approach with coordinated input from a physician, hand therapist, and nurse case manager. This chapter reviews several wrist and hand conditions that may occur in an occupational setting, including tendinitis, peripheral nerve compression lesions, sprains, fractures, arthritis, ganglia, and complex regional pain syndrome. The underlying pathologies, diagnostic methods, treatment options, and projected outcome for the various conditions are discussed.
TENDINITIS Tendinitis is a general term used interchangeably with tenosynovitis, stenosing tenosynovitis, and tendovaginitis. A thin low-friction envelope that surrounds individual tendons, the tenosynovium, enhances tendon gliding around bony prominences and through retinacular sheaths. Tenosynovitis, which refers to inflammatory changes in this lining, is often associated with a systemic disease process. A more frequently encountered condition, termed stenosing tenosynovitis or tendovaginitis, involves thickening of the tendon and overlying retinacular sheath with only a paucity of tenosynovial inflammation. de Quervain disease and trigger digit are two common examples.
is occasionally palpable as are small ganglia arising from the diseased compartment. The best objective tool in confirming the diagnosis of de Quervain disease is the Finkelstein test. By maximizing the excursion of the tendons through the stenotic first dorsal compartment, this maneuver produces significant discomfort for the patient if the condition is present. Conservative treatment options for de Quervain disease include splinting, corticosteroid injections, nonsteroidal antiinflammatory medication, temporary job modifications, and therapy. Splinting alone may be beneficial for management of acute pain, but symptom recurrence is common. A single corticosteroid injection into the first extensor compartment successfully relieves pain in 60% of cases, whereas two injections may provide relief in up to 80% of cases. Because the soft tissue in this region is thin, however, repeated corticosteroid injections, with infiltration into the subcutaneous tissues, can lead to localized depigmentation, fat necrosis, and subcutaneous atrophy. If conservative measures fail, surgical release of the first extensor tendon compartment may be considered. Surgery involves incision of the retinacular sheath and division of any septae separating the abductor pollicis and extensor pollicis brevis tendons. Vigorous retraction or injury of skin sensory nerves intraoperatively can cause periincisional pain and/or numbness. A therapist may be helpful in the early postoperative period with scar desensitization and strengthening exercises. Release of the first dorsal compartment predictably leads to a satisfactory result in over 90% of cases. Patients are generally able to return to unrestricted employment within 6 to 8 weeks after surgery.
Trigger finger The flexor tendons projecting to each digit enter a retinacular sheath that begins in the distal palm. Thickening of the tendons and sheath at this point may obstruct normal tendon gliding, leading to catching and locking of the digit (Fig. 6d.2).
de Quervain disease The dorsal wrist is comprised of six retinacular compartments encompassing the extensor tendons of the wrist and hand. The first compartment, which contains the abductor pollicis longus and the extensor pollicis brevis tendons, is located directly over the styloid process of the distal radius (Fig. 6d.1). Painful restricted tendon motion through this compartment is referred to as de Quervain disease.19 de Quervain disease is frequently associated with activities involving repetitive flexion and extension of the thumb and ulnar deviation of the wrist. The condition is also associated with direct trauma, rheumatoid arthritis, gout, and diabetes mellitus. A subdivision of the compartment by a septum is thought to predispose some individuals to the development of this condition. A patient with de Quervain disease presents with symptoms of pain, swelling, and tenderness over the radial styloid. Pain can be quite severe, with guarding and limitation of wrist and thumb motion. Crepitation with thumb flexion and extension
Figure 6d.1 Wrist and finger extensor tendons. The first dorsal compartment contains the abductor pollicis longus and extensor pollicis brevis tendons (arrow). Painful restricted tendon motion through this compartment is referred to as de Quervain disease.
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area four fingerbreadths proximal to the radial styloid. Often, palpable and audible crepitus occurs in this region with active wrist motion. Other tendons occasionally involved by inflammation and stenosis include the flexor carpi radialis, the extensor carpi ulnaris, and the extensor pollicis longus. In these cases, nonoperative treatment measures that may include splinting, ice, corticosteroid injection(s), antiinflammatory medications, activity modifications, and therapy are usually successful.
CARPAL TUNNEL SYNDROME
Figure 6d.2 Digital flexor tendon sheath. Thickening of the tendons and sheath proximally may lead to triggering (arrow).
Examination often reveals a tender nodularity in the distal palm that moves with excursion of the tendons.26 Conservative care of a trigger digit entails activity modifications and a corticosteroid injection into the proximal flexor tendon sheath. Single finger involvement, a discreet palpable nodule, and a short duration of symptoms are favorable prognostic indicators. Splinting of the metacarpophalangeal joint for a brief period may be added to the treatment regimen. In individuals whose symptoms are aggravated by the use of small tools, modification of these instruments to distribute forces over a greater area with a lesser requirement for digital flexion may be beneficial. The reported success rates after an injection range from 60% to 84%. If conservative management fails, surgical treatment may be considered. Incision of the proximal portion of the flexor tendon sheath in the palm is curative in over 95% of cases. Most patients are capable of returning to unrestricted work activities within 4 to 8 weeks postoperatively.
The median nerve passes across the wrist through an unyielding fibroosseous canal, termed the carpal tunnel (Fig. 6d.3). Compression of the median nerve within this space is termed carpal tunnel syndrome. The condition occurs due to a mismatch between the volume of the canal and its contents: the median nerve and the nine digital flexor tendons. Carpal tunnel syndrome is associated with diabetes, hypothyroidism, rheumatoid arthritis, and renal failure. Other contributory risk factors include wrist fractures, aging, obesity, female gender, smoking, pregnancy, and alcoholism. In the workplace, carpal tunnel syndrome has been attributed to repetitive forceful use of the wrist and digits, repeated impact on the palm, and operation of vibratory tools. Task-related factors, however, are variable and inconsistent, and the mechanisms by which they may contribute to carpal tunnel syndrome are poorly understood. The diagnosis of carpal tunnel syndrome relies initially on the patient history.8 Symptoms may include tingling and numbness in the thumb and central digits, burning pain, weakness, and clumsiness of the hand, all corresponding to the motor and sensory distributions of the median nerve. Symptoms often appear after prolonged wrist flexion while sleeping and extended periods of wrist extension while driving. Loss of sensation (in the radial four digits) and atrophy of the thenar eminence muscles are symptoms of advanced median nerve compression. Carpal tunnel syndrome is diagnosed primarily through physical examination, including evaluation of thenar muscle
Other tendonopathies Intersection syndrome refers to tenosynovitis of the radial wrist extensor tendons where they cross the first dorsal compartment tendons in the distal forearm. Pain is typically localized to an
Figure 6d.3 Wrist magnetic resonance image, axial view. The carpal tunnel (white arrow) contains the median nerve and the nine flexor tendons. The adjacent ulnar tunnel (black arrow) contains the ulnar nerve and artery.
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Hand-Arm Vibration Syndrome
bulk and strength and performance of sensibility testing. A variety of provocative maneuvers is used to reproduce or accentuate the symptoms. Phalen’s test refers to placing the wrist in a fully flexed posture, whereas Tinel’s test refers to percussion of the median nerve over the wrist. The median nerve compression test involves direct pressure on the median nerve over the carpal canal. An electrodiagnostic study may be obtained to confirm the diagnosis of carpal tunnel syndrome and to quantify the degree of median nerve injury. In the absence of diminished sensation, muscle atrophy, or denervation potentials on electrodiagnostic testing, initial treatment for carpal tunnel syndrome involves splinting the wrist in neutral alignment and injecting corticosteroid into the carpal canal.11 A neutral wrist position relaxes the median nerve and maintains a low pressure in the carpal tunnel. Splinting and injection provide short-term relief of symptoms in over 75% of patients and continued symptomatic relief for 1 year or more in 13% to 40% of patients diagnosed early with mild symptoms. Presence of symptoms for less than 12 months, intermittent numbness, male gender, absence of advanced sensory changes, and normal thenar muscle bulk are good prognostic indicators for success. Activity modifications and use of antivibration gloves are encouraged in manual laborers.16 Associated systemic diseases such as diabetes and hypothyroidism should be recognized and appropriately managed. Ergonomic changes may be considered for general patient comfort and satisfaction. Many recommended measures have not, however, been scientifically proven to prevent or ameliorate symptoms of carpal tunnel syndrome. If patients experience only partial or temporary relief with conservative treatment measures, surgical decompression of the carpal tunnel may be considered. Individuals who report at least temporary relief after an injection are more apt to obtain similar relief from carpal tunnel release surgery.10 Newer techniques such as limited-incision carpal tunnel releases and those performed endoscopically have been developed to decrease palm discomfort and allow for a more rapid return to activities. Compared with a standard open decompression, the endoscopic procedure has been found to shorten the recovery period, but it may be associated with a higher reoperation rate and possibly an increased risk of nerve injury.20 Operative release reliably diminishes tingling in the digits, whereas improvements in numbness and weakness are less predictable. In patients with severe chronic nerve compression, it is not unusual to have permanent low-grade symptoms after uncomplicated carpal tunnel release surgery. Palm sensitivity around the scar, referred to as pillar pain, is fairly common and can be helped by scar desensitization performed by an occupational therapist. Activity restrictions in a manual laborer are typically recommended for a period of 6 to 8 weeks after surgery, with maximum medical improvement anticipated between 3 and 6 months postoperatively. Successful carpal tunnel release surgery usually produces no permanent impairment.
passes the ulnar nerve and artery. Compression of the ulnar nerve at this site can occur from trauma, use of vibrational tools, ulnar artery thrombosis or aneurysm, or presence of a space-occupying lesion such as a ganglion cyst. Symptoms include intrinsic muscle weakness, numbness, and tingling in the ring and small fingers, or a combination of motor and sensory abnormalities. The diagnosis depends on a thorough physical examination and pertinent ancillary studies. The examination should include palpation, percussion, vascular and motor evaluations, and sensory testing. Wrist radiographs are helpful in excluding a hook of hamate fracture in patients with a history of trauma. Magnetic resonance imaging (MRI) or an ultrasound study may be valuable in identifying a ganglion cyst, ulnar artery aneurysm, or arterial thrombosis. An electrodiagnostic study can assist in locating the anatomic site of compression and in determining the severity of the nerve involvement. If a specific etiology for ulnar tunnel syndrome is identified, treatment is directed toward the cause. Examples include excision of a space-occupying lesion, resection of an arterial aneurysm, and repair or resection of a hook of hamate fracture. When no cause is found, conservative treatment measures such as wrist splints, antivibration gloves, activity modifications, and nonsteroidal antiinflammatory medication are instituted. Surgery is considered in these patients only if the diagnosis is certain and nonoperative modalities fail. The procedure involves decompression of the ulnar nerve and artery in the proximal palm. Most patients with ulnar tunnel syndrome without a structural lesion do well with nonoperative management. In patients managed surgically, assistance from an occupational therapist may be beneficial in the early postoperative period. Most patients are able to return to previous employment activities in 6 to 8 weeks, with maximum medical improvement expected from 3 to 6 months postoperatively. An uncommon cause of ulnar tunnel syndrome that deserves special mention is the hypothenar hammer syndrome.6,9 This condition results from repetitive impact to the ulnar aspect of the hand leading to ulnar artery damage and formation of a pseudo-aneurysm and/or clot. Clinical findings include local tenderness and ischemic changes with numbness in the ring and small fingers. A pathologic Allen test with compression of the radial artery and impaired blood flow to the ulnar digits supports the diagnosis. The location of the lesion can be determined with ultrasonography, selective angiography, or MRI angiography. Initial treatment of hypothenar hammer syndrome includes cessation of impact trauma to the hand, elimination of tobacco products, and avoidance of prolonged cold exposure. Arterial thrombosis may be addressed nonoperatively in some individuals with injection of a thrombolytic agent or surgically in others by resecting the damaged vessel segment. Because of the potential for repeated thrombi formation and emboli to the digital arteries, an aneurysm is best managed operatively. Although residual cold intolerance can be expected, the results of surgical treatment are generally good.
ULNAR TUNNEL SYNDROME
HAND-ARM VIBRATION SYNDROME
Neuropraxia of the ulnar nerve at the wrist is referred to as ulnar tunnel syndrome.3 The ulnar tunnel, or loge of Guyon, is a fibroosseous space adjacent to the carpal tunnel through which
Hand-arm vibration syndrome, or vibration white finger, is a complex condition associated with vibration exposure and the use of hand-held vibrating tools.14,18,22 Symptoms include
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white fingers, sensory disturbances, reduced hand dexterity, and diminished grip strength. Additional symptoms may include cold intolerance, wrist and hand pain, and muscle cramps. Vibration exposure has a cumulative effect on both vessels and nerves. The duration of exposure necessary to elicit symptoms, however, has never been clearly defined. The diagnosis of hand-arm vibration syndrome is based on a history of vibration exposure and the presence of symptoms. The Stockholm workshop scales are widely used in assessing the severity of this condition in affected individuals. Electrodiagnostic and vascular flow studies are helpful in excluding other etiologies such as an arterial thrombosis or peripheral nerve compression lesion, although separate conditions may coexist. Prevention of hand-arm vibration syndrome is of paramount importance, with measures including use of well-padded antivibration gloves and frequent breaks from operating vibratory machinery. If symptoms develop, avoidance of the inciting tool(s) is essential. Discontinuation of smoking, oral vasodilators, and limitation of cold exposure may be beneficial in reducing associated digital vasospasms. In early stages, the condition is typically reversible, but in long-standing cases, blanching of the fingers may persist indefinitely despite avoidance of vibration exposure.
include wrist arthrography (Fig. 6d.4), MRI arthrography, and arthroscopy. Initial nonoperative management is indicated for acute and stable scapholunate interval injuries. Individuals with partial ligament tears and no clinical or radiographic evidence of carpal instability can be treated by temporary wrist immobilization. A nonsteroidal antiinflammatory medication and a localized cortisone injection may also be considered. Patients with chronic scapholunate ligament tears and evidence of marked degenerative arthritis can be initially managed similarly. If symptoms persist beyond approximately 4 months, surgical options may be discussed. In patients with acute and unstable scapholunate ligament injuries, early operative intervention is recommended. The decision to intervene surgically, however, depends on additional factors, including patient age, health status and expectations, and anticipated compliance with postoperative care. Because most individuals who sustain an acute scapholunate interval injury are physiologically young and active, direct ligament repair with capsular augmentation is perhaps the best means of managing this injury. However, other surgical procedures
SPRAINS A sprain constitutes an injury to one or more ligamentous structures stabilizing a joint. The complex anatomy of the wrist ligaments includes thickened bands of capsular tissue interconnecting the distal radius to the distal ulna and carpal bones, along with deeper structures such as the scapholunate and lunotriquetral interosseous ligaments linking adjacent carpal bones. The finger metacarpal and interphalangeal joints are stabilized by medial and lateral capsular thickenings termed collateral ligaments and a strong palmar structure designated the volar (palmar) plate.
Scapholunate interval Stability of the scapholunate interval depends on the integrity of the scapholunate interosseous ligament and secondary capsular ligament restraints.31 A history of falling onto the affected hand is often described in association with a scapholunate interval injury, the symptoms of which include dorsoradial wrist pain and a weakened grasp. Occasionally, active wrist flexion against resistance produces a painful snapping sensation. The diagnosis is suspected when pain is elicited with finger pressure over the scapholunate interval. The scaphoid shift test is helpful in excluding other causes of dorsoradial wrist pain, such as a ganglion cyst. A positive shift test is noted if the proximal pole of the scaphoid can be translated over the dorsal rim of the radius under dynamic load. In the initial evaluation, plain radiographs are useful. If an abnormality in carpal bone spacing is detected, comparative views of the contralateral wrist are obtained to distinguish a normal variation in carpal spacing from pathologic carpal alignment. In equivocal cases, fluoroscopic imaging can be helpful. Additional studies that may assist in making the diagnosis
Figure 6d.4 Wrist arthrogram. Radiopaque dye injected into the radiocarpal interval with leakage into the midcarpal and distal radioulnar joints. The appearance is diagnostic for tears of the scapholunate and lunotriquetral ligaments and the triangular fibrocartilage complex (TFCC).
Chapter 6d
have been described for treatment of both acute and chronic scapholunate interval trauma. Depending to a large degree on the specifics of the surgery, the course of rehabilitation and the results of treatment vary.
Lunotriquetral interval Analogous to scapholunate instability, pathologic laxity of the lunotriquetral interval requires injury to both the lunotriquetral interosseous ligament and the secondary capsular restraints.27 The spectrum of pathology ranges from partial ligament tears with retained carpal stability to complete dissociation with carpal collapse. Symptoms may include pain and crepitus with diminished wrist motion, grip weakness, and sensation that the carpus is giving way. To differentiate a lunotriquetral interval injury from other lesions that can cause ulnar-sided wrist symptoms, a careful examination is necessary. Palpation over the lunotriquetral joint predictably elicits pain. A ballottement test, performed by grasping the pisotriquetral unit between the thumb and index finger of one hand and the lunate between the thumb and index finger of the other hand, reproduces symptoms and may demonstrate abnormal joint laxity. Plain radiographs are recommended in the evaluation of ulnar-sided wrist pain. Lunotriquetral instability may not be readily apparent on standard radiographic images, however. An MRI arthrogram can assist in diagnosis and occasionally reveal other lesions contributing to the symptom complex. Initial management is typically nonoperative, involving activity modifications and a 4- to 6-week course of wrist immobilization. A midcarpal corticosteroid injection and short-term use of an antiinflammatory medication may be beneficial also. Most patients with isolated lunotriquetral ligament tears respond well to conservative treatment. Persistent pain localized to the lunotriquetral interval with failure of conservative management is an indication to intervene surgically. The result depends on a variety of factors, including chronicity of the injury, associated carpal arthrosis, and specifics of the operation performed. Surgical options include simple ligament debridement, shortening of the ulna to decompress the lunotriquetral joint, lunotriquetral ligament reconstruction, and lunotriquetral fusion. Poor response to a previous injection and/or immobilization is a strong indicator of a potential surgical failure.
Sprains
in the soft tissues distal to the tip of the ulnar styloid predictably elicits discomfort. Stress testing of the stabilizing function of the TFCC is performed by applying dorsal and palmar pressure to the interval between the distal ulna and the carpus. Wrist radiographs are recommended to assess arthritic changes, carpal instability patterns, and ulnar bone length relative to the radius (ulnar variance). MRI with or without intraarticular contrast may assist in the diagnosis. In most patients, initial treatment of a TFCC injury involves a variable period of wrist immobilization and possibly a cortisone injection into the ulnocarpal joint. Exceptions include the rare traumatic tear with gross instability at the distal radioulnar joint. These cases usually require early operative intervention. In those individuals who fail conservative measures and have significant symptoms, surgical intervention may be indicated. Simple arthroscopic debridement is effective in the management of many traumatic TFCC lesions, especially central tears (Fig. 6d.5). In individuals with positive ulnar variance or lunotriquetral instability, this can be combined with formal ulnar shortening. Open or arthroscopically assisted repairs of a peripheral tear have exhibited results similar to or better than debridement alone. The expected postoperative recovery period depends to a large extent on the details of the operation performed. After discontinuation of splint immobilization, all patients may benefit from a short period of therapy. Maximum medical improvement is expected 3 to 6 months postoperatively.
Triangular fibrocartilage complex The triangular fibrocartilage complex (TFCC) is a soft tissue structure composed of seven contiguous elements that combine to stabilize the distal radioulnar joint and suspend the ulnar carpus.15 Traumatic disruption of the TFCC can lead to ulnarsided wrist pain, instability of the distal radioulnar joint, and articular cartilage degeneration. Patients typically describe pain and a clicking sensation localized to the ulnar aspect of the wrist after known injury or repeated microtrauma. Symptoms are often aggravated by forearm rotation and ulnar deviation of the wrist. Applied pressure
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Figure 6d.5
Wrist arthroscopy.
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Gamekeeper’s thumb Disruption of the ulnar collateral ligament of the thumb metacarpophalangeal joint occurs when a significant valgus stress is applied to the joint,13 often from a fall on the outstretched thumb. The injury may result in metacarpophalangeal joint instability, causing pain with thumb motion and adversely affecting both grip and pinch strength. Two terms commonly used to describe this injury are the gamekeeper’s thumb and the skier’s thumb. The anatomy of the thumb ulnar collateral ligament is analogous to that of the collateral ligaments stabilizing the finger metacarpophalangeal and interphalangeal joints. The thumb ulnar collateral ligament ruptures most often from its distal insertion at the base of the proximal phalanx. Displacement of the ligament can occur such that it comes to lie superficial and proximal to the adductor pollicis muscle, a specific pattern of injury referred to as a Stener lesion (Fig. 6d.6). The diagnosis of a gamekeeper’s injury involves a careful examination of the involved thumb. Plain radiographs should be obtained to assess for an underlying bone injury. Stress radiographs with applied valgus force to the metacarpophalangeal joint can confirm the diagnosis and determine the degree of ligament disruption. Treatment of partial ligament tears involves a 4- to 6-week period of thumb immobilization. A hand-based spica splint or cast incorporating the thumb proximal phalanx usually suffices. A complete ligament tear is an indication for surgical intervention; in these cases a Stener lesion may preclude effective ligament healing with nonoperative treatment. The thumb is commonly immobilized for 4 weeks postoperatively. Unrestricted activities are permitted after 6 weeks in cases treated nonoperatively and after 3 months in patients managed surgically. In thumbs with partial ligament injuries, nonoperative treatment yields a stable and painless thumb with near-normal motion in most cases. In thumbs with a complete ligament
rupture treated early with surgery, more than 90% of patients can expect a good to excellent result.
Fingers The finger metacarpophalangeal and interphalangeal joints may be injured by a variety of different mechanisms, resulting in partial or complete disruption of the collateral ligaments and palmar plate. Although the closely conforming articular surfaces of the proximal and distal interphalangeal joints usually afford residual stability, the metacarpophalangeal joints are less anatomically constrained and may exhibit pathologic laxity with injury to identical periarticular structures. The diagnosis of a finger sprain is relatively straightforward. The involved joint exhibits variable swelling and limited motion with maximum tenderness in the area of soft tissue injury. Gentle stress may elicit visible or palpable joint instability. Assessment and documentation of neurovascular status commonly reveals a digital neuropraxia. Radiographs are valuable in excluding the presence of a fracture, joint subluxation, or joint dislocation. Ultrasound and MRI studies may be considered but are often unnecessary for initial diagnosis. A stable sprain of the finger metacarpophalangeal joint is treated with buddy strapping and immediate motion. Velcro straps or athletic tape is placed around the injured digit and adjacent finger, leaving the interphalangeal joints free for motion exercises. An unstable metacarpophalangeal joint may be managed by buddy strapping and/or immobilization in a handbased splint for 4 to 6 weeks. The decision to intervene surgically depends on several factors, including the presence of an associated avulsion fracture and residual joint instability with splint immobilization. Sprains of the proximal and distal interphalangeal joints are managed by finger extension splinting for a brief period followed by active motion exercises and protective buddy strapping. Progressive static or dynamic extension splinting may be indicated during the course of treatment to address a developing joint contracture. Supervised therapy is often helpful. Most finger sprains can be managed without surgical intervention. Some degree of permanent swelling is expected, and a small flexion contracture may persist. The deformity will unlikely impair hand function or preclude a return to gainful employment.
FRACTURES Distal radius
Figure 6d.6 Torn and displaced ulnar collateral ligament of the thumb metacarpophalangeal joint, termed a Stener lesion (arrow). This pattern of displacement is often responsible for failure of nonoperative management of complete ligament tears.
Distal radius fractures, commonly called Colles’, Barton’s, Smith’s, and Chauffeur’s fractures, account for 14% of all extremity injuries.12,24 Approximately 50% of these injuries involve the articular surface of the distal radius. In healthy and active individuals, restoration of bone and joint alignment is indicated to preserve function and to deter posttraumatic arthrosis. The initial examination should include an assessment for concurrent bone and soft tissue injuries with specific attention to the stability of the distal radioulnar joint. Although vascular compromise occurs rarely, neurologic symptoms are relatively
Chapter 6d
frequent and typically involve the median nerve in the carpal tunnel with paresthesias in the radial four digits. Radiographic evaluation is performed both before and after attempted closed fracture reduction (Fig. 6d.7). Assessment of the intraarticular extent of the injury is crucial. A residual joint incongruity of 2 mm or greater displacement has been associated with posttraumatic arthrosis. Special imaging studies such as computed tomography are useful when the fracture pattern and/or magnitude of displacement is difficult to determine on plain radiographs. Closed stable fractures in acceptable alignment can be treated nonoperatively. Serial radiographs are obtained, and a cast is worn for approximately 6 weeks, followed by the use of a temporary removable splint. Supervised therapy may be helpful early during the course of healing to assist with finger motion and later, after fracture consolidation, to help improve wrist motion and grip strength. Displaced and unstable fractures usually require surgery. Procedural options include the use of percutaneous pins, external fixation, open reduction and internal fixation, or a combination of methods. The results of treatment vary, depending in part on the severity of the initial injury and the extent of articular surface involvement. Although maximum medical improvement is anticipated 6 months after injury or surgery, patients may continue to demonstrate improvements in wrist motion, grip strength, and endurance for well over 1 year.
Scaphoid
Figure 6d.7
Figure 6d.8
Displaced distal radius fracture (arrow).
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Fractures
The scaphoid is the most commonly fractured carpal bone.7 This type of injury typically results from a sudden impact on the palm with the wrist hyperextended, such as occurs with a fall onto the outstretched hand. When the fracture is complete, intrinsic forces may lead to displacement of a scaphoid fracture into a flexed humpback position: The proximal pole extends, whereas the distal pole flexes. Classically, the patient presents with loss of wrist motion, snuff box tenderness, and pain with resisted forearm pronation and supination. Wrist swelling may be present, but this and other signs of local trauma are not always apparent. In many instances the presentation and diagnosis are delayed, with the injury initially attributed to a “sprain.” Although most scaphoid fractures can be detected acutely on good quality plain radiographs (Fig. 6d.8), some do not become apparent for several weeks. Specialized imaging studies, including MRI, scintigraphy, and computed tomography, are occasionally helpful in early diagnosis and subsequent management. Closed treatment is indicated for acute nondisplaced scaphoid fractures. If diagnosed promptly and immobilized for an adequate duration, more than 90% of stable scaphoid injuries heal. Surgical intervention is indicated for acute fractures that are either displaced or unstable and for older fractures that have failed to unite. Instability is defined as displacement greater
Scaphoid waist fracture (arrow).
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than 1 mm in any direction and injuries associated with loss of carpal bone alignment. Relative indications for surgical treatment include a proximal pole fracture and prolonged wrist immobilization that would be unacceptable to the patient for social and/or economic reasons. Intramedullary pins or screws have become the standard of fixation for scaphoid fractures, with union rates comparable with those reported for closed-cast treatment. When screws are used and stability is achieved, early mobilization of the wrist is often permitted. In one study of military personnel, percutaneous screw fixation of nondisplaced scaphoid fractures was shown to result in more rapid radiographic union and return to duty when compared with cast immobilization.5 Maximum medical improvement is expected 4 to 6 months after injury or surgery but is contingent upon fracture healing.
Metacarpals and phalanges Fractures involving the metacarpals and phalanges occur in multiple patterns: transverse, oblique, spiral, and comminuted.4,17 Most of these injuries may be evaluated using standard radiographs. The rotational alignment of the digit is assessed with active finger motion or by generating finger motion through a tenodesis effect with passive wrist flexion and extension. The phalanges should be parallel during extension and point toward the thenar eminence when flexed. Most metacarpal and phalangeal shaft fractures can be treated nonoperatively with protective casting or splinting. Clinical union usually requires 4 to 5 weeks for metacarpal injuries and 3 to 4 weeks for proximal and middle phalanx injuries. A distal phalanx fracture may take longer to unite. Metacarpal fractures are typically immobilized with a forearm-based cast or splint incorporating the metacarpophalangeal joint of the injured finger and one or two adjacent digits. Hand-based immobilization is indicated for proximal and middle phalanx shaft fractures, whereas distal phalanx fractures are treated with a simple finger splint. All cases require close radiographic follow-up to assess for loss of fracture alignment. Operative treatment is indicated for irreducible or unstable fractures and those associated with tendon lacerations. Articular injuries with marked incongruency and/or persistent joint subluxation are also considered for surgical repair. The type of fixation used depends on the fracture pattern, the soft tissue injury, and the judgment and experience of the surgeon. Depending in part on the severity of the fracture and associated soft tissue trauma, the reported results after nonoperative and operative treatment of metacarpal and phalangeal fractures are variable. A successful outcome requires patient compliance with treatment and an appropriately structured rehabilitation program. In most cases maximum medical improvement is anticipated approximately 3 to 4 months from injury or surgery.
affecting the hands symmetrically. The distal interphalangeal joint of the finger is the most commonly involved hand joint, followed by the thumb basilar joint. In contradistinction to systemic arthritic conditions such as rheumatoid arthritis, the finger metacarpophalangeal joints are usually spared. Although several studies have alluded to repetitive activities as having an influence on the development of osteoarthritis in the wrist and hand, a causal relationship between repetitive activities and degenerative joint disease has never been conclusively proven.
Wrist Osteoarthritis of the wrist most often develops secondary to a traumatic event. Intraarticular fractures of the distal radius, malunited scaphoid fractures, scaphoid nonunions, and intercarpal ligamentous injuries all predispose the wrist to degeneration. In many cases, however, a specific cause is never identified. Patients with wrist arthritis report pain, loss of mobility, and weakness in grip. Crepitation during motion or loading activities and swelling over the dorsal carpus are common in advanced disease. Plain radiographs confirm the diagnosis and assist in devising a treatment strategy (Fig. 6d.9). For early degenerative disease of the wrist, conservative measures are frequently successful. These include nonsteroidal
OSTEOARTHRITIS Osteoarthritis is a slowly progressive joint disease of multifactorial etiology.21,29 Cartilage degeneration and osteophyte formation are often seen in association with advancing age, characteristically
Figure 6d.9 Wrist degenerative arthritis developing after a scapholunate interval injury (arrow).
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antiinflammatory medication, wrist immobilization, activity modifications, and corticosteroid injection(s). Significant degenerative arthritic changes predict some degree of permanent functional impairment. Surgery is indicated if symptoms warrant and conservative treatment measures have failed. Procedures include proximal row carpectomy (excision of the three most proximal carpal bones), partial carpal bone fusions, and total wrist arthrodesis. The period of postoperative immobilization depends on the specifics of the operation performed, averaging 6 to 8 weeks for a fusion procedure. Results of surgical treatment are favorable in terms of pain relief. Motion-retaining procedures such as a partial wrist fusion and proximal row carpectomy require a considerable amount of therapy after cast removal. Total wrist fusion is the most reliable in terms of relieving pain and improving grip strength but at the expense of wrist motion. Work restrictions after surgery must be determined on an individual basis, taking into account the specific job requirements. Maximum medical improvement is anticipated 6 months postoperatively.
Thumb basilar joint The basilar joint of the thumb consists of the metacarpal base and trapezium bone.2 Arthritis around the trapezium is the second most common site for degenerative joint disease in the hand (preceded only by the distal interphalangeal joint). More frequent in females than males, the condition has been attributed to laxity of the important stabilizing ligaments of the thumb. Patients with basilar thumb joint arthritis have pain localizing to the base of the thenar muscles. Opening jars and turning door knobs are often difficult tasks to perform comfortably. As the condition advances, pinch and grip strength diminish, and thumb range of motion may decrease as well. Examination reveals a tender and enlarged basilar joint. Axial grinding of the thumb metacarpal exacerbates the pain and may elicit sensations of instability and crepitation. The Finkelstein test is usually negative, helping to distinguish basilar joint arthritis pain from de Quervain disease. The diagnosis is confirmed by plain radiographs (Fig. 6d.10). Initial treatment of basilar joint osteoarthritis includes activity modifications, splint immobilization, nonsteroidal antiinflammatory medication, thenar muscle strengthening exercises, and joint injection(s). If a patient’s symptoms are not satisfactorily relieved by conservative means, surgical intervention may be considered. The most commonly performed operation entails partial or total excision of the diseased trapezium with stabilization of the thumb metacarpal base using local tendon graft. A significant hyperextension deformity of the thumb metacarpophalangeal joint may require a concomitant procedure to stabilize the metacarpophalangeal joint. The postoperative course typically involves a 4- to 6-week period of wrist and thumb immobilization followed by a supervised therapy program. Pain relief from surgery is nearly universal but not always complete, especially in younger and more active individuals. Activity modifications in the workplace may be indicated for an extended period of time after surgery. Thumb motion and
Figure 6d.10
Thumb basilar joint arthritis (arrow).
grip/pinch strength improve slowly. Maximum medical improvement is anticipated after approximately 6 months.
Proximal interphalangeal joint Osteoarthritis of the proximal interphalangeal joint is relatively rare. The condition typically arises after a dislocation or intraarticular fracture. The earliest signs of degenerative arthritis are swelling and morning stiffness. Limited proximal interphalangeal joint motion follows with the development of marginal osteophytes (Bouchard’s nodes). Late joint degeneration leads to an angular deformity and joint instability. Radiographs confirm the diagnosis and reveal the degree of joint deterioration. Conservative treatment measures include nonsteroidal antiinflammatory medication, activity modifications, and short-term splinting. Early in the degenerative process, steroid injections can be helpful in ameliorating pain. If these measures fail and considerable symptoms persist, surgical intervention may be considered. Arthrodesis is the most reliable method of eliminating pain. Fusion of the ulnar digits at the proximal interphalangeal joint level impairs grip strength and finger dexterity to a greater
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degree than it does in the radial digits. Fusion rates vary from 84% to 100%. Implant arthroplasty also provides pain relief with the added benefit of preserving partial joint motion. Joint replacement, however, carries an attendant risk of implant breakage and should be avoided in younger patients and/or manual laborers. Maximum medical improvement is expected 3 to 6 months postoperatively.
Distal interphalangeal joint Idiopathic degeneration of the distal interphalangeal joint commonly involves multiple digits in a symmetric distribution, whereas single finger joint degeneration is more suggestive of previous injury. In most cases, symptoms are mild and functional impairment is negligible. Swelling and stiffness are common symptoms in early degeneration of the distal interphalangeal joint. As the disease progresses, joint enlargement is seen secondary to osteophyte formation (Heberden’s nodes), resulting in limited motion. Late in the disease, angular and rotational deformities occur at the finger tip. Radiographs confirm the diagnosis and demonstrate the severity of joint destruction. In most individuals, conservative care is successful. Treatment measures include nonsteroidal antiinflammatory medication, activity modifications, corticosteroid injection(s), and splinting. Surgery is reserved for symptomatic degenerative disease that does not respond to conservative measures. Distal interphalangeal joint fusion reliably relieves pain, restores stability and strength, and improves the appearance of the digit. Fusion rates vary from 80% to 100%. Maximum medical improvement is expected 2 to 4 months postoperatively.
GANGLIA Ganglia are fluid-filled structures that arise from a joint, tendon, or tendon sheath.28,30 They contain lubricating fluid called mucin that is similar in content to but more viscous than the fluid found in joints and tendon sheaths. Ganglia can emanate from almost any anatomic region, but they are most common at the wrist, the proximal margins of digital flexor tendon sheaths, and the finger distal interphalangeal joints. Cysts communicate with these structures through one or more ducts that account for their intermittent fluctuation in size. The true etiology of a ganglion is unknown, although approximately 10% have been associated with previous trauma.
Carpal ganglia Ganglia of the wrist are seen most frequently dorsally, near the articulation of the scaphoid and lunate bones (Fig. 6d.11). They occur less commonly at the palmar aspect of the wrist, adjacent to the flexor carpi radialis tendon. Cysts may be multiloculated and much larger than clinically apparent, extending far away from their point of origin. Patients with carpal ganglia may complain of activity-related wrist pain and weakness. Guarding with minor loss of wrist
Figure 6d.11 Wrist magnetic resonance image, axial view. Dorsal ganglion attached to the scapholunate interval (arrow).
motion secondary to pain may result. In most cases, however, the cysts yield few or no symptoms and require no specific intervention. For a symptomatic dorsal wrist ganglion, aspiration of the cyst with or without a corticosteroid injection is initially recommended and successful in up to 50% of cases. Aspiration is relatively contraindicated for volar wrist ganglia because of the close proximity of the radial artery. In these cases temporary wrist splinting and use of a nonsteroidal antiinflammatory medication may be helpful. Surgical excision of wrist ganglia is indicated for persistent pain, with reported recurrence rates averaging approximately 5%. The procedure is frequently performed in an open manner, although an arthroscopic technique for excising dorsal ganglia was recently described.25 After ganglion excision, most patients experience continued low-grade discomfort for several weeks. Supervised therapy may be helpful in diminishing pain and in restoring wrist motion and grip strength. Maximum medical improvement is anticipated 2 to 3 months postoperatively.
Retinacular cysts Ganglia arising from the digital flexor tendon sheath are termed volar retinacular ganglia or retinacular cysts. Appearing as a small bump at the base of a digit adjacent to the palmar digital flexion crease, this type of cyst commonly causes discomfort during activities that require gripping or holding objects in the palm. A painful cyst can usually be treated by needle aspiration. Surgery to excise the lesion is considered in recalcitrant cases and when the diagnosis is uncertain. A rapid return to regular work activities is expected.
Mucous cysts Cysts arising from the distal interphalangeal joint, termed mucous cysts, are invariably associated with degenerative arthritic changes in the underlying joint. Because of their location, mucous cysts
Chapter 6d
may disrupt the germinal matrix of the nail bed and lead to longitudinal nail plate grooves and ridges. Aspiration and instillation of a corticosteroid can be attempted, but this treatment is rarely curative. Because the distal interphalangeal joint is immediately deep to the skin surface, aspiration increases the likelihood of septic arthritis. Simple cyst excision carries a recurrence rate of 25% or greater. Excision of the cyst in conjunction with debridement of marginal joint osteophytes, however, is successful in over 95% of cases. Recovery after surgery is relatively rapid, and unrestricted use of the hand should be possible within 6 weeks.
COMPLEX REGIONAL PAIN SYNDROME Complex regional pain syndrome (CRPS) is a neurogenic disorder characterized by pain out of proportion to the level anticipated with the diagnosis, swelling, autonomic dysfunction, and joint stiffness.1,32 In the past, a variety of terms, including reflex sympathetic dystrophy, causalgia, Sudeck’s atrophy, and shoulder-hand syndrome, has been used to describe this condition. Type 1 CRPS develops after a noxious event without identifiable nerve injury, whereas type 2 CRPS occurs in association with a nerve injury. The pathogenesis of CRPS remains poorly understood. Autonomic hyperactivity is implicated in syndrome development, and in many cases psychologic factors seem to play a role. Initially, pain, swelling, restricted motion, and vasomotor changes (hyperhidrosis, erythema, excessive warmth) predominate the symptom complex. After several months, swelling changes from a soft to a hard brawny edema. Eventually, the skin appears shiny and glossy, and stiffness becomes marked with fixed joint contractures. The diagnosis of CRPS is made on clinical examination but may be confirmed by a variety of objective tests. Radiographs frequently reveal diffuse osteopenia secondary to bone demineralization. Three-phase bone scans show characteristic diffuse uptake in the involved areas. Thermography can depict asymmetric temperature when compared with the contralateral limb. Anesthetic blockade at the neck/shoulder level confirms the diagnosis in cases with primary involvement of the sympathetic nervous system. Successful treatment of CRPS depends on prompt diagnosis and early intervention. The appearance and persistence of inordinate pain after injury or surgery is typically the first sign. The possibility of nerve injury should be entertained and any painful stimulus (e.g., cast compression) eliminated. Active range-ofmotion exercises, edema control, interval splinting, and a stressloading program are initiated by an experienced therapist. Pharmacologic treatment measures include corticosteroids, αadrenergic blocking agents, calcium channel blockers, and regional anesthetic injections. To address marked joint contractures late in the disease process, surgical intervention may be indicated. Evidence suggests that the earlier treatment is instituted, the better the chance for a successful result. A significant percentage of patients, however, still complain of pain, cold intolerance, sensory disturbances, swelling, hand weakness, and stiffness years later. Once the chronic stages of CRPS have occurred, results are less favorable, with expected varying degrees of permanent upper extremity impairment.
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References
CONCLUSION Management of an occupational-related disorder of the wrist or hand is contingent upon the recognition of factors related to condition development, a coordinated team approach to care, and the patient’s active participation in recovery. Conservative treatment measures include supervised therapy, splinting, corticosteroid injection, oral pain medication, and activity modifications. Surgical intervention may be indicated for trauma, advanced nerve compression lesions, arterial thrombosis, recalcitrant tendonitis, symptomatic degenerative arthritis, painful ganglia, and various other conditions. The ultimate goals of treatment should include patient satisfaction, symptom resolution, and return to gainful employment.
REFERENCES 1. 2. 3. 4. 5.
6. 7. 8. 9. 10. 11.
12. 13. 14.
15. 16. 17. 18.
19. 20. 21. 22. 23.
Atkins RM: Aspects of current management complex regional pain syndrome. J Bone Joint Surg Br 85(8):1100-1106, 2003. Barron OA, Glickel SZ, Eaton RG: Basal joint arthritis of the thumb. J Am Acad Orthop Surg 8:314-323, 2000. Bednar MS: Ulnar tunnel syndrome. Hand Clin 12(4):657-663, 1996. Blazar PE, Steinberg DR: Fractures of the proximal interphalangeal joint. J Am Acad Orthop Surg 8:383-390, 2000. Bond CD, Shin AY, McBride MT, Dao KD: Percutaneous screw fixation or cast immobilization for nondisplaced scaphoid fractures. J Bone Joint Surg Am 83(4):483-488, 2001. Cooke RA: Hypothenar hammer syndrome: a discrete syndrome to be distinguished from hand-arm vibration syndrome. Occup Med 53(5):320-324, 2003. Cooney WP III: Scaphoid fractures: current treatments and techniques. Instr Course Lect 52:197-208, 2003. D’Arcy CA, McGee S: Clinical diagnosis of carpal tunnel syndrome. JAMA 284(15):1924-1925, 2000. De Monaco D, Fritsche E, Rigoni G, Schlunke S, Von Wartburg U: Hypothenar hammer syndrome: retrospective study of nine cases. J Hand Surg Br 24(6):731-734, 1999. Edgell SE, McCabe SJ, Breidenbach WC, LaJoie AS, Abell TD: Predicting the outcome of carpal tunnel release. J Hand Surg Am 28(2):255-261, 2003. Gerritsen AA, de Krom MC, Struijs MA, Scholten RJ, de Vet HC, Bouter LM: Conservative treatment options for carpal tunnel syndrome: a systematic review of randomized controlled trials. J Neurol 249(3):272-280, 2002. Hanel DP, Jones MD, Trumble TE: Wrist fractures. Orthop Clin North Am 33(1):35-57, 2002. Heyman P: Injuries to the ulnar collateral ligament of the thumb metacarpophalangeal joint. J Am Acad Orthop Surg 5:224-229, 1997. Jetzer T, Haydon P, Reynolds D: Effective intervention with ergonomic, antivibration gloves, and medical surveillance to minimize hand-arm vibration hazards in the workplace. J Occup Environ Med 45(12):1312-1317, 2003. Kalainov DM, Culp RW: Arthroscopic treatment of TFCC tears. Tech Hand Upper Extremity Surg 1(3):175-182, 1997. Kasdan ML, Lewis K: Management of carpal tunnel syndrome in the working population. Hand Clin 18(2):325-330, 2002. Kozin SH, Thoder JJ, Lieberman G: Operative treatment of metacarpal and phalangeal shaft fractures. J Am Acad Orthop Surg 8:111-121, 2000. Kurozawa Y, Nasu Y, Hosoda T, Nose T: Long-term follow-up study on patients with vibration-induced white finger (VWF). J Occup Environ Med 44(12):1203-1206, 2002. Lane LB, Boretz RS, Stuchin SA: Treatments of de Quervain’s disease: role of conservative management. J Hand Surg Br 26:258-260, 2001. Macdermid JC, Richards RS, Roth JH, Ross DC, King GJ: Endoscopic versus open carpal tunnel release: a randomized trial. J Hand Surg Am 28(3):475-480, 2003. Palmieri TJ, Grand FM, Hay EL, Burke C: Treatment of osteoarthritis in the hand and wrist: nonoperative treatment. Hand Clin 3(3):371-383, 1987. Pelmear PL: The clinical assessment of hand-arm vibration syndrome. Occup Med 53(5):337-341, 2003. Piligian G, Herbert R, Hearns M, Dropkin J, Landsbergis P, Cherniack M: Evaluation and management of chronic work-related musculoskeletal disorders of the distal upper extremity. Am J Ind Med 37(1):75-93, 2000.
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24. 25.
26. 27. 28.
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Rettig ME, Raskin KB: Acute fractures of the distal radius. Hand Clin 16(3):405-415, 2000. Rizzo M, Berger RA, Steinmann SP, Bishop AT: Arthroscopic resection in the management of dorsal wrist ganglions: results with a minimum 2-year follow-up period. J Hand Surg Am 29:59-62, 2004. Saldana MJ: Trigger digits: diagnosis and treatment. J Am Acad Orthop Surg 9:246-252, 2001. Shin AY, Battaglia MJ, Bishop AT: Lunotriquetral instability: diagnosis and treatment. J Am Acad Orthop Surg 8:170-179, 2000. Steinberg BD, Kleinman WB: Occult scapholunate ganglion: a cause of dorsal radial wrist pain. J Hand Surg Am 24:225-231, 1999.
29. 30. 31. 32.
Steinberg DR: Management of the arthritic hand. In MW Chapman, ed: Operative orthopaedics, ed 2. Philadelphia, 1993, JB Lippincott. Thornburg LE: Ganglions of the hand and wrist. J Am Acad Orthop Surg 7:231-238, 1999. Walsh JJ, Berger RA, Cooney WP: Current status of scapholunate interosseous ligament injuries. J Am Acad Orthop Surg 10:32-42, 2002. Zyluk A: The sequelae of reflex sympathetic dystrophy. J Hand Surg Br 26(2): 151-154, 2001.
CHAPTER
6e
Biomechanical Aspects of Hand Tools Robert G. Radwin
The mechanical relationships between hands, tools, and tool operation are important for understanding and controlling physical stress of tool operators. Hand exertions needed for many tool operations are affected directly by the selection of specific tools and accessories for the task. Although many of the recommendations in this chapter are based on years of extensive biomechanics research, others arise out of simple mechanical principles and reasonable assumptions about mechanical relationships between tools and their operators. The objective is to illustrate how the characteristics of a particular tool (such as size, shape, output, and accessories) and its manner of use (such as orientation or location relative to the operator) can significantly affect the effort needed for performing specific tasks. Both manual (hand powered) and power (electric, pneumatic, or hydraulic) hand tools require that operators produce forces at varying levels. Manual tools may require exertion of forces to squeeze together tool handles, such as those of pliers and cutting tools. Other manual tools may require twisting, pulling, or pushing. Safe operation of a power tool requires that an operator support it adequately in a particular position and apply the necessary forces while reacting against the force generated by the tool itself. Force demands that exceed an operator’s strength capabilities can cause loss of control and result in an accident or an injury. If improper selection, installation, or use of a power tool requires an operator to make substantially greater exertion than necessary, it may lead to muscle fatigue or a musculoskeletal disorder.1,5,28,39,40 Tools that are selected to minimize hand forces are usually the best ones for the task. The discussion begins with simple manually operated hand tools, including screwdrivers and pliers. An investigation of the means by which different kinds of screw fasteners can affect forces in the hands is followed by a description of how selection and installation of power hand tools can control the static and dynamic hand forces associated with their use. Mathematical and biomechanical calculations are provided to enable interested readers to follow them and to impress other readers less concerned with how objective conclusions can be ascertained through mostly deterministic methods. These principles should be applicable to occupational health professionals in the selection and installation of tools. Designers and engineers should be able to adapt these calculations to new tools and job designs.
of screws and work situations. A screw is tightened usually by grasping the screwdriver handle and simultaneously applying a torque while exerting a push force. The amount of torque, T, needed for tightening a screw depends on the kind of screw and the characteristics of the screw joint such as friction, screw diameter, thread, and clamping load. The push force is often called feed force. Feed force, F, is the axial force applied against the screwdriver shaft that is required to thread the screw and keep the screwdriver blade seated. Numerous taskrelated factors affect feed force, including thread type (whether the screw is self-tapping or threaded), material hardness, thread size, and hole diameter. The choice of a particular size screwdriver can have a great effect on the hand exertion required for a task.
Handle length A question often asked is how does screwdriver length affect hand force? Experience has found that a longer screwdriver handle generally results in less effort.32 This can be explained by considering the motions needed for tightening a screw. When a screw is tightened, torque is transferred to the handle, usually by rotating the forearm in combination with flexion and ulnar deviation of the wrist. The asymmetry of the hand, wrist, and forearm relative to the screwdriver’s radial axis produces eccentric rotation of the handle that causes perturbation of the handle and shaft along a horizontal displacement Δ from the vertical axis (Fig. 6e.1). The magnitude of this displacement depends on the particular action and anthropometry of the wrist.
F
Fx
Δ
Fy
Direction of twist θ
L
Direction of rotation
MANUAL SCREWDRIVERS One of the most commonly used hand tools, the screwdriver, is available in various sizes and forms suitable for different types
Figure 6e.1 Rotation and perturbation of a manual screwdriver when the handle is twisted in the hand.
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This perturbation causes the screwdriver shaft to tilt to a maximum angle, θ, as the screwdriver rotates. If screwdriver handle size, diameter, and shape and shaft diameter remain the same, hand and wrist rotation is unaffected by the shaft length, so the handle perturbation remains constant. Assuming that the handle displaces the same distance Δ from the axis of the fastener shaft (Fig. 6e.1), the maximum angle, θ, that the screwdriver shaft tilts as it is twisted can be described as ⎛ Δ⎞ θ = sin−1 ⎜ ⎟ ⎝ L⎠ Orthogonal feed force components (Fig. 6e.1) can be resolved into Fy = F cosθ, Fx = F sinθ If a screwdriver has a length, L, then the maximum component parallel to the fastener shaft is Fy: ⎡ ⎛ Δ⎞ ⎤ Fy = F cos θ = F cos ⎢ sin−1 ⎜ ⎟ ⎥ ⎝ L⎠⎦ ⎣ Solving for F, F=
Fy ⎡ ⎛ Δ⎞ ⎤ cos ⎢ sin−1 ⎜ ⎟ ⎥ ⎝ L⎠⎦ ⎣
A consequence of this relationship is that if the required axial force component Fy remains constant, F decreases as L increases. Hence, the hand force exerted can be reduced by increasing L and using the longest screwdriver available. For example, if the shaft of a 6-cm screwdriver displaces Δ = 3 cm, the feed force F needed to drive a screw is F=
Fy ⎡ ⎛ 3⎞ ⎤ cos ⎢ sin−1 ⎜ ⎟ ⎥ ⎝ 6⎠ ⎦ ⎣
= 1 . 15 × Fy
Therefore, the maximum feed force can be as much as 15% greater than the axial force needed. If the screwdriver length is increased to 25 cm, the feed force needed to drive a screw would be F=
Fy ⎡ ⎛ 3 ⎞⎤ cos ⎢ sin−1 ⎜ ⎟ ⎥ ⎝ 25 ⎠ ⎦ ⎣
= 1 . 01 × Fy
which decreases the force feed to only as much as 1% more force than is actually needed. Of course, a very long screwdriver may not be practical under all circumstances. Clearance and spatial constraints may limit the size of screwdriver that can be used. Furthermore, a very short screwdriver can facilitate the precision grip needed for light precise work, such as that afforded with a jeweler’s screwdriver. Another way to limit the horizontal perturbation of a screwdriver as it rotates in the hand is by supporting the screwdriver shaft, as might be done when two hands are used. If the screwdriver were held straight by supporting the shaft with the fingers of the free hand, then the tilt angle θ remains close to 0 degrees
~F cos 0 degrees ~ ~ F. This action therefore aids the and Fy~ operator by keeping the axial feed force requirements minimal and unaffected by screwdriver length. When high feed forces are required, screwdriver shafts should be long enough to be pinched or gripped by the other hand as a guide. Using a similar argument, the hand force needed for a nut driver should be mostly independent of the shaft length because the shaft is coupled to the nut, permitting concentric rotation with the handle despite the asymmetries of the hand and forearm.
Handle diameter Another common question is how does a screwdriver handle diameter affect hand force? Several studies investigated the effect of handle diameter on the torque capability of the hand. A study involving volitional torque exerted for different manual screwdrivers, locking pliers, and wrenches found that the resulting torque magnitude was influenced strongly by the kind of tool and the posture assumed.26 From a purely mechanical standpoint, a greater handle diameter should result in more torque at the screwdriver shaft for the same effort, provided that the frictional properties of the handles are similar and the diameter is not too large. The diameter of a screwdriver handle plays a critical role in limiting a user’s torque-generating capability. Large grip forces are often needed for sustaining a grip and for coupling the hand and the tool to prevent the handle from slipping. A simplified relationship between the torque and diameter illustrates the effect of mechanical advantage on torque: T = S G = μ FG G where T is torque, S is the shear grip force, G is the handle radius, μ is the coefficient of friction between the hand and the handle, and FG is grip force.32 If FG remained constant, torque would linearly increase as the handle diameter increased. As is well known, however, grip strength is not constant for all diameters but rather is affected by handle size.4,17,19 If a handle is too large or too small, the strength of the hand is greatly compromised. The relationship between cylindrical handle size and grip strength is summarized in Figure 6e.2.29 Maximum grip force occurs around 6 cm. Consequently, the optimal diameter is one in which a further increase in diameter increases the mechanical advantage while simultaneously decreasing grip force. Research has found that this optimum depends on handle design, friction, gender, and hand size.32 Torque performance diminishes when handle diameters are greater than 5 cm,33 and a diameter of 4 cm is sometimes recommended for screwdrivers.7,8 Sufficient friction must be present between the handle and the hand to provide a secure grip, exert force or torque, and prevent a tool from slipping. Surfaces that do not provide adequate friction require greater grip force that may result in greater effort and even loss of control of the tool. The amount of friction depends on the coefficient of friction between the hand and the material or object grasped. Some materials have greater coefficients of friction and consequently better frictional characteristics than others. No one handle size is practical for all tasks, and certain handles serve some objectives better than others. A panel of ergonomics experts recommends using a small-diameter handle (8-13 mm)
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Grip strength
400
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Screwdriver blades and screw heads
Allowances should be made for all these factors. The three most common threaded fastener heads are slotted, Phillips, and Torx™ (Fig. 6e.3), each of which has different feed force requirements.
Slotted screws 300
200 4
5
6
7
Handle span (cm) Figure 6e.2 Grip strength for a population of 29 subjects (19 university students and 10 factory workers). Error bars represent one standard error of the mean.
for a precision grip and a large-diameter handle (50-60 mm) for a power grip.27 In one study, handles between 31 and 38 mm in diameter were considered optimal for a power grip12; several studies recommend 50 mm as an upper limit diameter.4,33,38
SCREWDRIVER BLADES AND SCREW HEADS Screwdriver feed force can be affected by the particular type of screw fastener head and screw tip needed.6 Self-tapping screws require more feed force than do screws tightened through pretapped holes. Material hardness and friction are also important factors to consider for self-tapping screws. Feed force requirements increase as the torque level increases for cross-recess screws.
Slotted
Phillips head
Torx
The oldest and simplest type of screw head, the slotted screw, has a single slot across the entire diameter of the head. When a screwdriver blade is inserted inside a screw slot and rotated, contact is usually made at the two edges of the blade, as shown in Figure 6e.4. The size of the screwdriver width, w, limited by the radius of the screw head provides a slight mechanical advantage for applying torque against the screw. Wider screw heads and screwdriver blades generally require less torque exertion at the screwdriver shaft. We ignore frictional force by assuming that friction between the screw and screwdriver blade is zero. (Because in this case, friction assists the operator by helping keep the screwdriver blade in the screw slot, zero friction would be the worst-case condition.) If the width of the screwdriver blade is w and the applied torque at the screwdriver shaft is T, then the normal contact force, FC, between the blade and the screw head slot is FC =
T W
Because the blades of slotted screwdrivers are usually tapered to an angle φ to ease insertion of the screwdriver blade and accommodate different size screw slots, the normal contact force FC is not actually perpendicular to the screwdriver shaft but rather acts at an angle perpendicular to the blade edge (Fig. 6e.4). This results in an axial force at each contact point
Fy = FC sin φ =
T sin φ W
Figure 6e.3 Slotted head, Phillips head, and Torx™ head screws.
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Fy
F = 4Fy = 4FC sin φ = 4
Because φ is typically greater for Phillips head screws and w is much smaller, Fy is considerably more than for slotted screwdrivers. The typical taper angle for a Phillips head screw is φ = 40 degrees, so
T
F=4 φ Fc Fc
T T sin( 40 °) = 2 . 57 . W W
which is more than six times the force needed for a slotted screw with an equivalent diameter head.
Torx™ head screws W
Figure 6e.4
T sin φ. W
Static forces acting on a slotted screwdriver blade and shaft.
that acts to push the screwdriver blade out of the slot as torque is applied to the shaft. The hand must react against this force by exerting an equal and opposite axial force Fy that is a component of the feed force. Because there are two contact points, the total axial force is 2Fy. Consequently, the axial force required to keep the blade from coming out of the slot is F = 2Fy = 2
T sin φ. W
The greater the torque T, the greater the axial force needed to keep the screwdriver blade in the slot. If the screwdriver blade taper angle φ is 12 degrees, F=2
T T sin(12 °) = 0 . 42 . W W
If the screwdriver blade angle is not tapered but parallel to the slot, this force is negligible (Fy = 0) because no axial force acts to unseat the blade. Such a screwdriver, however, would be limited to certain size slots and more difficult to insert into them.
Phillips head screws Although slotted screws are simpler, screwdriver blades sometimes slip out of slotted heads and have the potential to damage or scratch the work piece. The Phillips head screw (Fig. 6e.3) gained popularity because it prevented slippage and discouraged vandals from removing screws in public places with a coin or knife edge.31 A Phillips head screwdriver blade contains four wedges acting on the blade. Similarly to the slotted screwdriver, the axial forces acting parallel to the fastener can be described by the equation
Torx™ screws offer the advantages of both slotted screws and Phillips head screws. Because φ = 0 for Torx™ head screws (Fig. 6e.3), no axial force component other than the actual feed force is required to advance the fastener. Because the screwdriver blade cannot be tapered to accommodate different-size screws, Torx™ head screws are not as flexible as slotted or Phillips head screws. The disadvantage of requiring a large assortment of screwdrivers with corresponding blade sizes may be outweighed by the mechanical advantage of Torx™ head screws. Furthermore, they are more difficult to tamper with because Torx™ head screwdrivers are less readily available than slotted and Phillips head screwdrivers and an assortment of sizes are needed. The advantages and disadvantages of slotted, Phillips, and Torx™ head screws are summarized in Table 6e.1.
PLIERS AND CUTTING TOOLS The particular finger or combination of fingers used can affect grip strength.2,37 As the strongest fingers, the thumb, index, and middle fingers should be used for producing the most grip force. The weaker ring and small fingers should be used for stabilizing handles rather than acting as primary force contributors. Sometimes tool operators handle tools in ways that take these differences into account. Table 6e.1 Summary of ergonomic advantages and disadvantages of different screw heads Screw head
Advantages
Disadvantages
Slotted
Very flexible tool—one size fits all
Difficult to keep seated in the slot Can slip and damage work piece Requires more axial feed force
Requires little axial feed force Phillips Torx™
Easy to keep seated in head Flexible tool No axial feed force needed Easy to keep seated in head
Inflexible—must have a specific size for an associated screw head
Chapter 6e
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Power hand tools
Xj
θ Lj
L1 X1
L2 L3 L4
X2 X3 X4
Figure 6e.6
Figure 6e.5 grasped.
Static forces acting on the hand when a pair of pliers is
Offering the mechanical advantage provided from squeezing together two opposing lever arms, pliers are used often for pinching, grasping, and cutting. The common use of pliers involves a grip depicted in Figure 6e.5, where the pliers jaw is held on the radial side of the hand. In many instances, however, this grip does not optimize the mechanical advantage with finger strength and can result in greater exertion than necessary. Swedish researchers observed that some sheet metal workers held metal shear blades on the ulnar side of the hand by using an inverted grip (Fig. 6e.6) rather than that used with conventional shears.10,41 Finger strength data revealed that the inverted grip allowed a greater span between the larger index finger and thumb than between the small finger and the palm, providing a better-suited handle size for more force in each cut.14 The articulation angle from the closed position to the pivot point is defined as θ. The jaw span Xj is related to the grip span Xi as L Xi = X j i Lj where Li is the distance from the fulcrum to the finger i, Lj is the distance from the fulcrum to the jaw tip, and Xi is the grip span available for finger i. Assuming there are no coupling effects between fingers, the resultant force is the sum of all four fingers. Individual-finger
Inverted pliers grip.
normal strengths for the distal phalanx while grasping handles of different sizes are taken from Amis.2 By summing the moments about the pivot point, the total moment is MJ = F1L1 + F2L2 + F3L3 + F4L4 This moment is counteracted by that produced from reaction forces at the jaw. Consequently, the maximum jaw force is Fj =
Mj Lj
Using the dimensions provided in Table 6e.2, the maximum jaw force available increases from 714 to 786 N (10) just by inverting the handle. Because the index and middle fingers have the greatest strength, they are provided with larger moment arms for generating force with the inverted grip, providing additional mechanical advantage. One study observed that the maximum force of one finger depended not only on its grip span but also on those of the other fingers.14
POWER HAND TOOLS One of the best methods of controlling applied hand exertion is to substitute a power hand tool for a manual tool. In fact, many repetitive jobs could not be performed without the use of power tools. Modern power hand tools can operate at high speeds and produce very high forces. Exertions and forces acting against the hand in power tool operation can be reduced by eliminating excess weight, by making the best use of the mechanical advantage, or by
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254
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Biomechanical aspects of hand tools
Table 6e.2 Pliers handle dimensions and associated finger strength for showing the mechanical advantage using an inverted grip Grip
Index
Middle
Ring
Small
Grip span Xi (cm) Grip strength Fi (N) Finger distance Li (cm) Torque (Nm) Jaw force FJ Inverted
6.0 60 7.0 420 165
6.6 63 8.3 523 206
6.4 44 10.2 449 177
5.4 37 11.4 422 166
Grip span Xi (cm) Grip strength Fi (N) Finger distance Li (cm) Torque (Nm) Jaw force FJ
5.4 62 11.4 707 278
6.4 64 10.7 685 270
6.6 43 8.3 357 141
6.0 35 7.0 245 97
Si Gi
Total
Conventional 204 1814 714
LGY
L1Y
204 1994 786 T
providing mechanical aids for holding tools, parts, and materials. Selecting a power hand tool having certain dimensions and shapes can often reduce tool reaction forces and provide mechanical advantages that assist the operator. Increasing friction between the hand and objects grasped can also reduce the forces required for gripping tools. Nut runners and power screwdrivers are widely used for securing screws and threaded fasteners in manufacturing and assembly operations, such as in the automotive, mechanical equipment, and electronics industries. Using electromyography as an index of muscle effort during pneumatic shut-off nutrunner operation, Radwin et al37 observed that electromyographic activity during threaded fastener torque buildup was affected by tool torque output and torque buildup time. Electromyographic activity during torque buildup was more than three times greater than during preparation and shut-off. Oh and Radwin29 observed that the operator initially overcomes the tool reaction force with a concentric muscle exertion. As the force rapidly rises, the tool eventually overcomes the operator, causing the motion in opposition to muscle contraction and resulting in an eccentric muscle exertion. Due to passive properties of the muscle, during an eccentric, or lengthening, contraction the muscle acts like a spring, producing proportionally more force as it lengthens. Because they directly affect handle force in a complex manner, tool geometry, mass, moment of inertia, and center of gravity are important factors in the design and selection of power hand tools. By providing mechanical advantages, the handle length of pistol-grip and right-angle tools and the diameter of in-line tool handles likewise affect hand exertions.11,20,36 Tool load affects grip force,9,16,21,43 fatigue onset,18 task performance,13 and subjective preference by tool operators.3,30,42 In addition to the static forces exerted by an operator when carrying and positioning tools or when a tool is running at a constant state, the impulsive forces and torques produced by rotating spindle power hand tools are dynamic.
Figure 6e.7 operated.
Forces acting in the hand when an in-line nut runner is
Static forces Lin et al22 developed a mechanical model of power hand nutrunner operation for static equilibrium (no movement) conditions. Using hand force, reaction force from the work piece, tool weight, and tool torque, the static force model calculates handle force when carrying tools and when spindle torque is constant. The model uses a Cartesian coordinate system relative to the orientation of the handle grasped using a power grip (Fig. 6e.7A). This coordinate system has the x-axis perpendicular to the axial direction of the handle, the y-axis passed through the long axis of the handle, and the z-axis perpendicular to both. The origin is the end of the bit or socket. Hand forces are described here in relation to these coordinate axes. To simplify the model, we assume that orthogonal forces can be summed along the handle without producing coupling moments, an assumption that allows force to have a single point of application. The variables used in the model are summarized in Table 6e.3 and illustrated in Figure 6e.7. When a tool is in static equilibrium, the sums of all forces (F), moments (M) about the origin, and grip moments generated by the spindle (MG) are zero. Therefore three vector equations can be developed: Σ Fi + Σ Ri + W + FF + Fs = 0
(Σ F = 0)
Σ (Fi + Ri) × Li + W × LG = 0
(Σ M = 0)
Σ Si × Gi + T = 0
(Σ MG = 0)
These vector equations can be written in matrix form: The full model considers forces and moments exerted by both hands (subscripts 1 and 2), but not all these equations are
Chapter 6e
0 0 1 0 0 0 0 0 0 0 0 ⎡ 1 ⎢ 1 0 0 1 0 0 0 0 0 0 0 ⎢ 0 ⎢ 0 0 1 0 0 1 0 0 0 0 0 0 ⎢ L1z −L1y L 2z −L 2 y 0 0 0 0 0 0 0 ⎢ 0 ⎢ −L1z 0 0 0 0 0 0 L 1x − L 2 z L 2x 0 0 ⎢ 0 L 2 y −L 2 x 0 0 0 0 0 0 0 ⎢ L 1y − L 1x ⎢ 0 1x 0 0 G 2x 0 0 0 0 0 0 0 G ⎢ ⎢ 0 0 0 0 0 0 0 G1y 0 0 G2 y 0 ⎢ 0 0 0 0 0 0 0 G1z 0 0 G2z ⎣ 0 ⎡F1x ⎤ ⎢ ⎥ ⎢F1y ⎥ ⎢F1z ⎥ ⎢ ⎥ ⎢F 2 x ⎥ ⎢F 2 y ⎥ ⎢ ⎥ ⎢F 2 z ⎥ ⎢S1x ⎥ ⎢ ⎥ ⎢S1y ⎥ = ⎢ ⎥ ⎢S1z ⎥ ⎢ S2 x ⎥ ⎢ ⎥ ⎢ S2 y ⎥ ⎢ S2 z ⎥ ⎢ ⎥ ⎢Fsx ⎥ ⎢ ⎥ ⎢Fsy ⎥ ⎢⎣Fsz ⎥⎦
Legend of variable notation
Variable*
Description
Fi Si
Handle force acting on hand i Shear force acting in hand i, applied when the handle rotates in the y-axis Reaction force produced by the spindle torque at point i Tool weight Feed force; not applicable when carrying a tool Surface support force; not applicable when carrying a tool Tool torque Location vector of point i Location vector of the center of gravity Grip radius at point i, applied when the handle rotates in the y-axis
Ri W FF Fs T Li LG Gi
0 1 0 0 0 0 0 0 0
Power hand tools
0⎤ ⎥ 0⎥ 1⎥ ⎥ 0⎥ 0⎥ × ⎥ 0⎥ 0 ⎥⎥ 0⎥ ⎥ 0⎦
− W x − R1x − R 2 x − FFx ⎡ ⎤ ⎥ ⎢ − W y − R1y − R 2 y − FFy ⎥ ⎢ ⎥ ⎢ − W z − R1z − R 2 z − FFz ⎥ ⎢ ⎢ L1zR1y − L1yR1z + L 2 zR 2 y − L 2 yR 2 z − LGzW y + LGyW z ⎥ ⎢ L1xR1z − L1zR1x + L 2 xR 2 z − L 2 zR 2 x − LGxW z + LGzW x ⎥ . ⎥ ⎢ ⎢L1yR1x − L1xR1y + L 2 yR 2 x − L 2 xR 2 y − LGyW x + LGxW y ⎥ ⎥ ⎢ −T Tx ⎥ ⎢ ⎥ ⎢ − Ty ⎥ ⎢ − Tz ⎦ ⎣
required for all situations, and in certain cases the equations system may be reduced depending on tool shape and operating conditions. For example, the shear force needed for in-line tools is insignificant for pistol grip tools except when a hand grasps the tool around the spindle. The tool torque and feed force are Table 6e.3
1 0 0 0 0 0 0 0 0
●
*All the variables in bold type are vectors. Subscript i represents a specific hand used in operating the tool. The right hand is annotated using subscript 1 and the left hand is annotated using subscript 2.
assumed always to act in a single axis. When the matrix becomes degenerate or singular, additional assumptions are needed to solve for handle force. Nut runners are commonly configured as pistol grip, right angle, and in-line (Fig. 6e.7). Examples are provided in this article to demonstrate the resulting matrix reduction for these three common tool shapes. A set of more general cases are fully described in Lin et al.22
Pistol-grip power drivers Consider the free-body diagram of the pistol-grip nut runner in Figure 6e.7B, which shows the use of the right hand (subscript 1), and the tool geometry shown in Figure 6e.8A. The spindle stall torque T acts clockwise in the xy-plane. The tool operator must oppose this equal and opposite reaction torque Tz counterclockwise by producing a reaction force R1x along the x-axis that is equal to and opposite of the hand force component F1x. This is not, however, the only force that the tool operator must produce. A force acting along the z-axis F1z provides feed force FFZ and produces an equal and opposite reaction force FSz. The operator must also react against the tool mass to support and position the tool by producing a vertical force component F1y. The tool weight Wy and push force F1z tend to produce a clockwise rotation of the power tool about the spindle in the yz-plane that is countered by this vertical support force.
255
256
Chapter 6e
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Biomechanical aspects of hand tools
y x L1z z LGz Tz FFz F1y
LGy −Tz
L1y Wy F1z
F1x
Figure 6e.8
Static forces during pistol-grip nut runner operation.
In the case of one-handed operation, the right hand (subscript 1) reacts against all tool forces and torques. The vector equations can therefore be reduced to ⎡ 0 0 1 ⎢ 0 1 ⎢ 0 ⎢ 0 0 0 ⎢ ⎢ 0 L1z − L1y ⎢ L 1y 0 0 ⎣
0 1⎤ ⎥ 1 0⎥ 0 1⎥ × ⎥ 0 0⎥ ⎥ 0 0⎦
⎡F1x ⎤ ⎢ ⎥ ⎢F1y ⎥ ⎢F1z ⎥ = ⎢ ⎥ ⎢Fsy ⎥ ⎢Fsz ⎥ ⎣ ⎦
0 ⎤ ⎡ ⎥ ⎢ − W y ⎥ ⎢ ⎢ − FFz ⎥ . ⎥ ⎢ ⎢ − W yLGz ⎥ ⎢ − Tz ⎥ ⎦ ⎣
These equations reveal several relationships between tool parameters and hand force. Torque reaction force R1x = F1x is directly proportional to the reaction torque Tz and inversely proportional to the handle length L1y. The torque reaction force is therefore less for longer tool handles than for shorter handles. The vertical support force F1y is inversely proportional to the tool length L1z and dependent on tool weight, center of gravity location, handle length L1y, and feed force FF = F1z. The equations indicate that less effort is probably needed for supporting a pistol-grip power hand tool when the tool body is long than when it is short. When feed force is large, supporting force decreases when the handle length is short. This is why handles aligned close to the tool spindle axis and with long tool bodies are advantageous for tools such as power hand drills. These drills often require considerable feed force with torque reaction forces relatively less than for a nut runner, so a short handle is favorable. Alternatively, when torque is large and feed force is small, a tool with a long handle is advantageous. When both feed force and torque are significant factors, however, as when drilling large holes or shooting self-tapping screws in hard wood, these parameters must be optimized. The model can be used for comparing resultant hand forces associated with different tools for the same operation and for
selecting the tool requiring the least exertion. Consider the four hypothetical power nut runners shown in Figure 6e.9. All four tools weigh the same (30 N) and have the same torque output with different dimensions and mass distribution. Comparisons between the four tool dimensions are provided in Table 6e.4. Assuming one-handed operation, resultant hand force was predicted by using the model for the four different tools and plotted as a function of torque in Figure 6e.9. Hand force was determined for both low-feed force (1 N) and high-feed force (100 N) conditions when the tools were operated against a vertical surface. When feed force was small, the resultant hand force was affected mostly by the torque reaction force, which increased as torque increased for all four tools. Because the greatest force component in this case was the torque reaction force, tools 3 and 4 resulted in the least resultant hand force because they had the longest handles (Table 6e.4). Tool 3, however, had a considerably greater resultant hand force when feed force was high because the hand was located farthest from the spindle for that tool. This effect was not observed for tool 4, which also had a long handle, because of its greater tool body length. Although tool 4 had the least resultant hand force when both feed force and torque levels were high, tools 1 and 2 had less resultant hand force for high feed force and low torque because these tools permitted the hands to grasp the tool close to the spindle axis. Consequently, the best tool depended on both feed force and the torque requirements for the task. All tools were assumed to weigh the same; had they varied weights, the differences might have been even greater. Additional factors the model can consider include relative tool weight, mass distribution, and tool orientation. This analysis does not take into account the relative strength capabilities of the hand in the three component directions, although use of such a model does not exclude strength comparisons.
Chapter 6e
●
Power hand tools
Tool types
1 Figure 6e.9
2
3
Comparison of resultant hand forces acting on the hand for four equivalent power nut runners plotted against reaction torque.
The reaction force transmitted to the hand for right-angle power drivers is affected also by the magnitude of spindle torque and the tool dimensions. Right-angle nut runner spindle torque can range from less than 0.8 Nm to more than 700 Nm. A tool operator opposes these forces while supporting the tool and maintaining control. This torque is transmitted to the operator as a reaction force and opposed by the great mechanical advantage resulting from the long reaction arm created by the tool handle.37
Right-angle power drivers A right-angle nut runner is functionally nothing more than a pistol-grip nut runner with a very short body and long handle. The model for a right-angle nut runner is shown in Figure 6e.7C. Because right-angle nut runners are usually operated with both hands, two-hand forces are now in the z-axis; F1z is applied at the handle for supporting the tool, and F2z is applied over the tool spindle to help provide feed force. (When these tools are used one handed, the equations for a pistol grip nut runner apply.) Right-angle tools have short spindles perpendicular to the long axes of the handles. Because the handle is usually longer than the spindle, these tools are often held in two hands (Fig. 6e.7C). In this case, the right hand (subscript 1) grasps the tool at the distal end of the tool handle, whereas the left hand (subscript 2) grasps it proximal to the spindle. It is further assumed that equal amounts of force are exerted by both hands to react against tool torque along the long axis of the handle, and hence F1z = F2z. The resulting matrix is
Table 6e.4 Pistol-grip nut runner dimensions, load, and center of gravity location Tool 1 2 3 4
4
Weight (N) 30 30 30 30
L1z (m)
L1y (m)
L1z (m)
0.09 0.40 0.11 0.40
0.06 0.09 0.50 0.50
0.07 0.26 0.07 0.32
0 1 0 ⎤ ⎡ F1x ⎤ ⎡ − W x ⎤ ⎡ 1 ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ − 0 0 1 0 1 ⎥ ⎢ F1z ⎥ ⎢ ⎢ ⎥ × = ⎢ 0 L 1y 0 L 2 y ⎥ ⎢ F 2 x ⎥ ⎢ − T x ⎥ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎣L1y 0 L 2 y 0 ⎦ ⎣ F 2 z ⎦ ⎣ − W xLGy ⎦ These equations can be used to compare hand forces between a right-angle and a pistol-grip power nut runner used on a horizontal surface (Fig. 6e.10). The right-angle nut runner in this example weighs 20 N, whereas the pistol-grip nut runner weighs 50 N. A graph of torque reaction force plotted against torque shows that the mechanical advantage of the right-angle nut runner for high torque levels is considerable. The other hand, however, exerts greater feed force for the right-angle nut runner than for the pistol-grip nut runner. Because the pistol-grip nut runner weighs more and has its center of gravity closer to the tool spindle, it requires less support force for F1z and F2z than for the right-angle nut runner (Fig. 6e.10). Sometimes handle force can be reduced further through the proper use of accessory handles and torque reaction arms.
In-line power drivers The form factor and associated forces and moments involved in operating an in-line power tool are shown in Figure 6e.7D and dimensions in Figure 6e.8C. Assuming that the right hand (subscript 1) supports the tool, the static handle force matrix is ⎡1 0 ⎤ ⎡F1y ⎤ ⎡ − W y ⎤ ⎢ ⎥×⎢ ⎥=⎢ ⎥ ⎣0 G1x ⎦ ⎣ S1y ⎦ ⎣ − Ty ⎦ The static torque developed at an in-line power hand tool spindle has an equal and opposite reaction torque Ty that must be overcome by tangential shear forces between the hand and the handle. The tangential shear force S1y produces torque about the grip radius G. The shear force S1y is proportional to the compressive hand force FG and the coefficient of friction μ between the hand and the handle, similar to a manual screwdriver except in this case the spindle rather than the hand is producing the torque. In-line power driver operation is therefore limited by the
257
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Chapter 6e
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Biomechanical aspects of hand tools
z x L1y y LGy Lzy
F1x F2z
L1z
LGz F1z Wz −Tz Tz
FRz Figure 6e.10
Static forces for right-angle nut runner operation.
maximum compressive grip force an operator can produce and by the dimensions of the tool. The relationship between the static torque, grip force, and tool diameter is similar to that of manual screwdriver operation: Ty = S1yG = μFG G Push-to-start activated power hand tools free the operator from having to squeeze a trigger or lever, but they can increase force requirements because they require more feed force to start them. A flange at the end of in-line handles helps prevent the hand from slipping during feed force exertion.15
Accessory handles and torque reaction arms Accessory handles assist a pistol-grip power tool operator by providing an additional handle for two-handed operation. A torque reaction bar can sometimes be used to transfer loads back to the work piece. In fact, reaction torque can be completely eliminated from the operator’s hand by use of either a stationary reaction bar adapted to a specific operation so that reaction force can be absorbed by a convenient solid object or a torque-absorbing suspension system. A reaction bar can be installed on in-line, pistol-grip, and angled tools. The advantages of tool-mounted reaction devices are that (1) all reaction forces are removed from the operator; (2) one-hand-operated pistol-grip and in-line reaction bar tools can be used rather than right-angle nut runners, which usually require two hands; (3) reaction bar tools can be less restricting on
the operator’s posture; (4) tool speed and weight are improved over right-angle nut runners in most tool sizes; and (5) use of reaction bars can improve tool performance. The limitations are that (1) torque reaction bars must be custom-made for each operation, (2) several attachments can make tool use difficult, (3) adding weight to the tool makes it more cumbersome to handle, and (4) the intervention is not practical when the accessibility is limited, the manipulation is restricted, or the reaction bar has no surfaces to contact. If a reaction bar is provided, however, a smaller tool handle can be used. When an accessory handle or torque reaction bar is used with a pistol-grip nut runner (Fig. 6e.11), the horizontal hand force F1x is reduced. If a vertical force is applied to a torque reaction bar, as depicted in Figure 6e.12, an additional term is needed for the sum of the moments in the z-axis: T − F1x L1y + FSy LSx = 0 As a result, F1x becomes F1x = − FSy L Sx +
T L1 y
If a torque reaction bar is used and all the torque reaction force acts against a stationary object, then T = −FSy LSx Consequently, F1x = 0
Chapter 6e
●
Power hand tools
259
Tool types
Pistol grip
Right angle
Figure 6e.11
Comparison of hand forces between a right-angle nut runner and a pistol-grip nut runner operated on a horizontal surface.
Tool counterbalancers The force requirements for a job are often related to the weight of the tools being handled. The effort needed for holding an object in the hands is usually associated with its mass,34,35 so that heavier tools generally require greater exertion. There is a tradeoff between the selection of a lightweight tool and the benefit of the added weight for performing operations that require high feed force. A spring counterbalance or air balancer can help reduce the load from heavy tools that are operated frequently. When used to support the tool, the counterbalance produces a force that opposes gravitational force. This is illustrated with a pistol-grip power tool in Figure 6e.13. When the tool is held freely in the hand, there is no torque to react against (T = 0) and consequently no reaction force (F1x = 0). Besides creating a
moment in the yz-plane, the counterbalance force FCy also influences F1y. The moment is counteracted by a coupling moment, C, from the hand, as described in the following equations: F1y + Wy + FCy = 0 F1yL1z + WyLGz + FCyLCz + C = 0 If the counterbalance force FCy is set to counteract the tool weight Wy, then FCy = −WTy Consequently, the y-axis component of the hand force becomes F1y = 0. The location that the counterbalance force acts against the tool can affect operator exertion when holding it. Solving for the coupling moment C, C = FCy(LGz − LCz)
LSx
The equation shows that the coupling moment can be eliminated (C = 0), if
−TZ
LGz = LCz
FSy
F1x
Figure 6e.12 Force and moment arm for a pistol-grip nut runner equipped with a torque reaction bar.
Balancers should therefore be attached to tools at or near their centers of gravity so as to avoid additional effort by the tool operator to counteract the handle moment. Balancers should be installed carefully so that minimal effort is needed when holding and using the tools in the desired work location. Spring counterbalances produce a force that opposes gravitational force so the tool weight is reduced. If installed incorrectly, however, these balancers can actually have the reverse effect of increasing force. Spring tension should be adjusted so that the operator does not have to counter more force than necessary and balancers so that the tool aligns as close to the work area as possible to prevent unnecessary reaching. The counterbalance should not lift the tool when it is released so that the operator must elevate the shoulder to reach it; the tool should remain suspended at the same height at
260
Chapter 6e
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Biomechanical aspects of hand tools
y
FCy
x
LCz L1z
z
LGz
LGy L1y Wy Figure 6e.13 Static forces when handling a pistol-grip power hand tool with a counterbalance. Counterbalance force FCy creates a moment in the yz-plane that is counteracted by a coupling moment C.
which it was released. Also, situations where operators tend to work ahead of or behind the assembly line should be avoided. If a tool is moved horizontally, a trolley and rail system should be installed. Special attention may be required to be sure that the balancer is attached directly above the work.
Dynamic forces Tool torque buildup model There are three elements involved in power nut runner operation using a threaded fastener: the operator, the tool, and the mechanical joint that joins or clamps two objects together, the hardness of which is analogous to the stiffness of a spring. The clamping
Figure 6e.14 Recording of torque buildup profiles for hard (light line) and medium-soft (heavy line) joints. (From Lin JH, Radwin RG, Fronczak FJ, Richard TG: Ergonomics 46(12): 1161-1177, 2003.)
F1y C
force of a threaded fastener is therefore proportional to torque, with a desired clamping force achieved by rotating the fastener to a specific target torque. Levels of joint stiffness range from a hard joint (30 degrees of spindle rotation) to a soft joint (360 degrees of spindle rotation). Examples are illustrated in Figure 6e.14 The spindle torque and angular displacement during torque buildup have a linear relationship such that θt θ( T ) = ( T − T0 ) Tt − T0 where T is tool spindle torque, θ is spindle angular displacement, Tt is the target torque, T0 is the rundown torque, and θt is the target angle.
Chapter 6e
Pneumatic motors have a distinctive speed-torque relationship. The motor does not produce torque at the free running speed, whereas it exerts maximum torque when the motor stalls. The spindle speed can be described using the equation S( T ) = S0 (1 −
T ), T max
where S is spindle speed expressed as a function of torque T, Tmax is the motor maximum torque output, and S0 is free running speed. Because speed S(T) is the derivative of angular displacement θ(T), the unique solution for the differential equation is the torque delivered to the spindle T ( t ) = T max + ( − T max + T0 )e
−
●
Power hand tools
following differential equation results in terms of the tool rotation θ: ( J T + Msh 2 )
d 2θ dθ + csh 2 + ks h 2 θ = T(t) dt dt 2
where T(t) is the tool torque, Ms, cs, and ks are the operator mechanical parameters, JT is the mass moment of inertia of the tool about its spindle, and h is the distance between the hand and the tool spindle.
( Tt − T0 ) S0 t θtT max
The force experienced by the hand can be obtained by dividing the equation for T(t) by the distance of the hand from the rotating spindle.
Handle force model: dynamics Lindqvist25 proposed that a simple mass-spring mechanical system might be sufficient to describe the handle response to impulsive reaction forces encountered in nut runner operation but did not identify specific parameters for these elements. Lin et al23 advanced this model of the human operator; their method identifies these mechanical properties to predict the kinematic and kinetic response of the handle (motion and force) when an impulsive reaction force was encountered in threaded fastener power hand tool operation. A brief description of the model is provided here. The human operator is represented as a dynamic mechanical analog of a single degree-of-freedom mechanical system consisting of a linear spring, a mass, and a viscous damper (Fig. 6e.15). Instead of modeling for individual contributing muscles, the model combines the loading of the muscles and joints into mechanical elements without considering the directions of the loads. The mechanical properties, Ms, ks, and cs, are assumed to be passive and invariant for an individual, a given posture, and a tool orientation. The effective mass Ms represents the total contributions of the standing operator coupled to the tool through the hands. The effective spring stiffness and damping represent the gross effect of the operator acting against the handle, including contributions from the entire body and nonspecific muscle groups. A system identification method using free oscillation measures these mechanical parameters for various work locations for three common tool shapes: pistol grip, right angle, and in-line. This method measures the influence of the operators’ mechanical elements on the system dynamic response (oscillation frequency and damping ratio) of a known mechanical system. The mechanical parameters are then extracted analytically.23 Given the mechanical parameters for an operator, the model estimates the dynamic response (angular displacement and force) when the operator encounters an impulsive reaction force from a power tool. A torsional dynamic equilibrium equation about the tool spindle axis can be written. The
Figure 6e.15 A pistol-grip pneumatic hand tool is illustrated with a normal operator grip. The mechanical parameters can be defined as follows: Ms = the total effective mass of the operator’s arm, hand, and a portion of the upper body lumped at the distance h from the center of rotation of the tool spindle or line of action of the tool torque, T(t). JT = the rotational mass moment of inertia of the tool about the center of mass of the tool. h = location of the center of pressure of the operator’s hand on the tool handle. ks = the effective stiffness of the operator’s arm, hand, and a portion of the upper body. cs = the effective damping of the operator’s arm, hand, and a portion of the upper body. T(t) = the tool torque which is transmitted to the operator in a typical mechanical fastening operation. θ = the rotation of the tool and hand about the tool spindle axis. H = horizontal distance between the floor and the handgrip. V = vertical distance between the ankles and the handgrip. (From Lin JH, Radwin RG, Richard TG: Handle dynamics predictions for selected power hand tool applications. Hum Fact 45(4):645-656, 2003.)
261
262
Chapter 6e
●
Biomechanical aspects of hand tools
This second-order differential equation can be solved numerically using finite difference techniques and a discrete time step variation of the tool torque, T(t). The result will be a description of the time variation of the tool rotation, θ(t),
⎧ ⎪ ⎪ 1 θi + 1 = ⎨ 2 2 ⎪ Msh + J T + cs h 2 ⎪ ( Δt ) 2 Δt ⎩
⎫ ⎪⎡ ⎤ ⎫ ⎪⎧ cs h 2 2( Ms h 2 + J T ) ⎪⎫ ⎪ ⎪⎧ 2( Ms h 2 + J T ) 2⎪ sh ⎬ θi + ⎨ k θ i − 1 + Ti ⎥ , − ⎬ ⎬ ⎢⎨ ( Δt ) 2 ( Δt ) 2 ⎥⎦ ⎪ ⎢⎣ ⎩⎪ ⎭⎪ ⎭⎪ ⎩⎪ 2 Δt ⎪ ⎭
where i is the iteration step, Δt is the time step, and T is the tool torque. With the rotational response of the tool predicted, the motion of the handle can be defined as hθ(t). The force F(t) delivered to the handle can be approximated by csh
situations can be assisted by comparing the mechanical relationships between the task and tool parameters. Other aspects that should be considered but are not covered in this chapter include repetitive use, assumed postures, vibration exposure, and contact stress.
dθ + ks hθ = F(t) dt
Here the handle force F was estimated by solving the above equation. The tool operator mechanical model was also used to estimate tool handle kinematics during torque buildup. The resultant handle displacement and force for using a right-angle tool having buildup times ranging from 35 (hard) to 1000 (soft) ms was calculated and is plotted in Figure 6e.16 for the female with the smallest stiffness and the male with the greatest stiffness.24
CONCLUSIONS AND RECOMMENDATIONS Tool operator exertion can be minimized by considering the forces acting on the tools and the way they are used for a specific task. The selection of alternative hand tools for different work
The following recommendations can be made: 1. When large feed forces are necessary, use the longest manual screwdriver available and provide a screwdriver shaft long enough so that it can be gripped by the other hand as a guide. Nut drivers and socket drivers also help reduce hand forces by providing concentric handle rotation and additional mechanical advantage at the screw head. 2. Large-diameter manual screwdriver handles with high frictional characteristics are recommended; if the handle diameter is too large, however, the mechanical advantage may be counteracted by reduced grip strength. 3. Phillips head screws should be avoided because they require greater axial push force as torque increases. Torx™ head screws provide the least axial reaction force. 4. Pliers and shears can sometimes be used to a greater mechanical advantage by gripping them so that the pivot is on the ulnar rather than the radial side of the hand. 5. Torque reaction force is less for longer pistol-grip and rightangle nut runners than for equivalent tools with shorter handles. 6. When pistol-grip power hand tools that have longer tool bodies are used, less vertical support force is required than for
Figure 6e.16 Model prediction for handle displacement and force when using a right-angle nut runner on a horizontal surface for different torque buildup times. (From Lin JH, Radwin RG, Richard TG: Handle dynamics predictions for selected power hand tool applications. Hum Fact 45(4): 645-656, 2003.)
Chapter 6e
equivalent tools with shorter tool bodies, provided that their mass distribution is similar. 7. All other factors being equivalent, when feed force is large and torque is small, a pistol-grip power tool with a shorter handle should be used. When feed force is small and torque is large, a pistol grip power hand tool with a longer handle is more advantageous. 8. Torque reaction bars help eliminate torque reaction forces, and accessory handles help distribute torque reaction forces among the two hands. 9. A tool counterbalance can help reduce the force needed to support a power hand tool. The optimal location for attaching a balancer is at the tool center of gravity.
17. 18.
19. 20.
21.
22. 23. 24.
25. 26.
REFERENCES
27.
1.
28.
2. 3. 4. 5. 6. 7. 8. 9.
10.
11.
12. 13. 14. 15. 16.
Aghazadeh F, Mital A: Injuries due to hand tools. Appl Ergonom 18(4):273-278, 1987. Amis AA: Variation of finger forces in maximal isometric grasp tests on a range of cylinder diameters. J Biomed Eng 9:313-320, 1987. Armstrong TJ, Punnett L, Ketner P: Subjective worker assessments of hand tools used in automobile assembly. Am Indust Hyg Assoc J 50:639-645, 1989. Ayoub MM, LoPresti PL: The determination of an optimum size cylindrical handle by the use of electromyography. Ergonomics 14(4):509-518, 1971. Cannon LJ, Bernacki EJ, Walter SD: Personal and occupational factors associated with carpal tunnel syndrome. J Occup Med 23:255-258, 1981. Cederqvist T, Lindberg M: Screwdrivers and their use from a Swedish construction industry perspective. Appl Ergonom 24(3):148-157, 1993. Cochran DJ, Riley MW: The effect of handle shape and size on exerted forces. Hum Fact 27:253-265, 1986. Cochran DJ, Riley MW: An evaluation of handle shapes and sizes. Proceedings of the 26th Annual meeting of the Human Factors Society, Seattle, WA, 1982, pp. 408-412. Cook TM, Rosecrance JC, Zimmerman CL: Work-related musculoskeletal disorders in bricklaying: a symptom and job factors survey and guidelines for improvements. Appl Occup Environ Hyg 11:1335-1339, 1996. Dahlman S, et al: Tools and hand function: requirements of the users and the use situation. In Y Quéinnec, F Daniellou, eds: Designing for everyone. London, 1991, Taylor & Francis. Deivanayagam S, Weaver T: Effects of handle length and bolt orientation on torque strength applied during simulated maintenance tasks. In FI Aghazadeh, ed: Trends in ergonomics/human factors V. Amsterdam, 1988, Elsevier Science, pp. 827-833. Drury CG: Handles for manual materials handling. Appl Ergonom 11(1):35-42, 1980. Drury CG, Hibschweiller ML: Size and weight effects on robot teach pendants. In SA Robertson, ed: Contemporary ergonomics. London, 1994, Taylor & Francis, pp. 417-423. Fransson C, Winkel J: Hand strength: the influence of grip span and grip type. Ergonomics 24(7):881-892, 1991. Grant KA, Habes DJ: Effectiveness of a handle flange for reducing manual effort during hand tool use. Int J Ind Ergonom 12:199-207, 1993. Grant KA, Habes DJ, Steward LL: The influence of handle diameter on manual effort in a simulated assembly task. In S Kumar, ed: Advances in industrial ergonomics and safety IV. London, 1992, Taylor & Francis, pp. 797-804.
29. 30.
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37. 38. 39.
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Greenberg L, Chaffin DB: Workers and their tools. Midland, MI, 1977, Pendell. Hallbeck MS, Sheeley GA, Bishu RR: Wrist fatigue in pronation and supination for dynamic flexion and extension: a pilot study. In S Kumar, ed: Trends in ergonomics/human factors I. Amsterdam, 1984, Elsevier, pp. 51-57. Hertzberg T: Some contributions of applied physical anthropology to human engineering. Ann NY Acad Sci 63(4):616-629, 1955. Huston TR, Sanghavi N, Mital A: Human torque exertion capabilities on a fastener device with wrenches and screwdrivers. In A Mital, ed: Trends in ergonomics/human factors I. Amsterdam, 1984, Elsevier, pp. 51-57. Kattel BP, Fernandez JE: Criteria for selection of hand tools in the aircraft manufacturing industry: a review. In MA Hanson, ed: Contemporary ergonomics. London, 1998, Taylor & Francis. Lin JH, Radwin RG, Fronczak FJ, Richard TG: Forces associated with pneumatic power screwdriver operation: statics and dynamics. Ergonomics, 46(12):1161-1177, 2003. Lin JH, Radwin RG, Richard TG: Dynamic biomechanical model of the hand and arm in pistol grip power hand tool usage. Ergonomics 44(3):295-312, 2001. Lin JH, Radwin RG, Richard TG: A single-degree-of-freedom dynamic model predicts the range of human responses to impulsive forces produced by power hand tools. J Biomech 36(12):1845-1852, 2003. Lindqvist B: Torque reaction in angled nutrunners. Appl Ergonom 24:174-180, 1993. Mital A: Effect of body posture and common hand tools on peak torque exertion capabilities. Appl Ergonom 17(2):87-96, 1986. Mital A, Kilbom A: Design selection and use of hand tools to alleviate trauma of the upper extremities. Part I. Guidelines for the practitioner. Int J Ind Ergonom 10:1-5, 1992. Myers JR, Trent RB: Hand tool injuries at work: a surveillance perspective. J Saf Res 19:165-176, 1988. Oh S, Radwin RG: Pistol grip power tool handle and trigger size effects on grip exertions and operator preference. Hum Fact 35(3):551-569, 1993. Örtengren R, Cederqvist T, Lindberg M, Magnusson B: Workload in lower arm and shoulder when using manual and powered screwdrivers at different working heights. Intl J Indust Ergonom 8:225-235, 1991. Petroski H: The evolution of useful things. New York, 1992, Alfred A Knopf. Pheasant S: Body space: anthropometry, ergonomics and design. London, 1988, Taylor & Francis, pp. 227-233. Pheasant S, O’Neill D: Performance in gripping and turning-a study in hand/handle effectiveness. Appl Ergonom 6(4):205-208, 1975. Radwin RG, Armstrong TJ: Assessment of hand vibration exposure on an assembly line. Am Ind Hyg Assoc 46(4):211-219, 1985. Radwin RG, Armstrong TJ, Chaffin DB: Power hand tool vibration effects on grip exertions. Ergonomics 30(5):833-855, 1987. Radwin RG, Oh S, Fronczak FJ: A mechanical model of hand force in power hand tool operation. In Proceedings of the Human Factors and Ergonomics Society, 39th Annual Meeting, San Diego, CA, October 1995, pp. 548-552. Radwin RG, VanBergeijk E, Armstrong TJ: Muscle response to pneumatic hand tool reaction forces. Ergonomics 32(6):655-673, 1989. Replogle JO: Hand torque strength with cylindrical handles. Proceedings of the 27th annual meeting of the Human Factors Society, Norfolk, Virginia, 1983, pp 412-416. Rothfleish S, Sherman D: Carpal tunnel syndrome: biomechanical aspects of occupational occurrence and implications regarding surgical management. Orthop Rev 7:107-109, 1978. Silverstein BA, Fine LJ, Armstrong TJ: Occupational factors and carpal tunnel syndrome. Am J Ind Med 11:343-358, 1987. Swedish National Institute of Occupational Health: Forskning & Praktik. Vol. 2. 1993, The Institute, pp. 14-17 (English edition). Ulin SS, Armstrong TJ, Snook SH, Monroe-Keyserling W: Perceived exertion and discomfort associated with driving screws at various work locations and at different work frequencies. Ergonomics 36:833-846, 1993. Westling G, Johansson RS: Factors influencing the force control during precision grip. Exp Brain Res 53:277-284, 1984.
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CHAPTER
Hip and Knee
7
CHAPTER
7a
Epidemiology of the Lower Extremity
Age, sex, and social life are of importance, along with occupational factors. When compared with the upper extremities, neck, and lower back, diseases and disorders of the lower extremities have less association to work.12 Workers’ compensation claims for disorders of the lower extremities account for fewer than 10% of all musculoskeletal claims in Sweden.
DEFINITIONS
Gunnar B. J. Andersson
Musculoskeletal impairments increase with age. This is true for lower extremity impairments as well. Praemer et al26 concluded, based on 1995 data, that over 5% of the U.S. population had lower extremity or hip impairments. This number is probably slightly higher today as the population has aged. Although the percentile rates were 1.8% among those below age 17, it was 7.7% in individuals 65 years of age and older. Women experience a slightly smaller percentage of lower extremity impairments than men. More than 20 million Americans have osteoarthritis (OA), which makes OA the leading cause of long-term disability in persons older than age 65 years. Nonspecific knee pain is reported by 4.6% of persons older than 18 years, and the corresponding number for hip pain is 3.1% (NHANES III). Specific to the workplace, in 1996 there were about 5.7 million occupational injuries in the United States, of which 6.4% were fractures and 43.6% were sprains and strains. Some 8.6% of fractures and 10.3% of sprains and strains involved the leg (excluding the foot and ankle); 71% of injuries occur from knee causes: overexertion (28%), contact with objects (26.2%), and falls (16.9%). Fractures resulting in work loss often involved the lower extremities (41.8%), but most of those affect the foot and ankle. On the other hand, sprains and strains involved the lower extremity frequently (20%), with the knee being affected in 8.5% of cases (Table 7a.1). In a population-based study of 55 year olds (575 subjects), Bergenudd5 showed that 11% had femoropatellar pain and 10% had knee joint pain. The prevalence was higher in women than in men. In a study correlating knee pain and low IQ measured 40 years earlier, low job satisfaction, obesity, and increased s-glutamyltransferase were found in men, whereas low education level, low income, low life success, and sleeping disturbances were found in women. For the entire group, knee pain and high occupational workload were also correlated. Similar results were found for hip pain. Occupational workload correlated with hip pain in men but not in women. Increased body weight correlated with knee pain in men and hip pain in women. As with many other musculoskeletal conditions, the background for symptoms from the knee and hip is multifactorial.
From an etiologic perspective, occupational musculoskeletal disorders can be viewed as caused, aggravated, or accelerated by work. An occupational injury is defined as any injury that results from a work-related accident or exposure involving a sudden event in the work environment.25 An occupational illness is any abnormal condition or disorder other than that resulting from occupational injury that is caused by exposure to factors associated with employment.25 Cumulative trauma disorders are considered occupational illnesses.
OCCUPATIONAL INJURIES In the United States, injuries to the musculoskeletal system in 1997 had an annual incidence of 7.1 per 100 full-time equivalent workers. Injuries among men are most common between 18 and 44 years of age. Rupture of tendons and muscles is not often caused by occupational loading. The strength of tissues decreases with age, but ruptures are most often seen in sports activities and as a result of rather high-loading injuries.
OCCUPATIONAL ILLNESS Joints are made for loading and movement. The cartilage of the joints is well designed to withstand compression, translation, and shear forces. Deleterious types of loading are loads in extreme positions (nutcracker effect) and axial impact loads particularly at high speed.23 Low-frequency vibrational loading may be deleterious to the joints and the joint cartilage but is often attenuated by the time it reaches the knee and hip. High-frequency vibration is unlikely to affect the lower extremities. Highly repetitive, monotonous work can cause a variety of problems in the joints, bones, tendons, and peripheral nerves. These types of loading conditions are not often seen in the lower extremities in relation to occupation but can occur during sports activities.
Tendinitis Tendinitis, tenosynovitis, myalgia, and other conditions of muscles and tendons are uncommon in the lower extremities.
Table 7a.1 Occupational injuries of the lower extremities as a percentage of all injuries: U.S. data.25 Diagnosis Fracture Sprain and strain
Hip 0.3 0.3
Knee 2.6 7.9
Lower leg 2.0 0.3
Multiple 1.2 0.8
Bursitis Eighteen bursae surround the hip joint, and approximately 10 surround the knee joint. Specific diagnoses are often difficult
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Epidemiology of the lower extremity
to make. Bursitis caused by sports overuse is not uncommon, but bursitis around the hip as an occupational illness is rarely seen. Bursitis of the knee, especially prepatellar or infrapatellar, is often seen in jobs that require kneeling, for example, floor layers, fishermen, and plumbers.28-30
Nerve entrapments Only occasionally is nerve entrapment seen in the lower extremities. Ischial neuralgia, or “wallet sciatica,” a sensation along the ischial nerve caused by compression at the infrapiriforme foramen, may be encountered by sitting, particularly when having a well-filled wallet in the back pocket. Peroneal nerve compression at the side of the knee may cause palsy and can result from work activities. This may happen to tractor drivers during prolonged sitting in a twisted position and from accidents. Ilioinguinal neuralgia and lateral cutaneous nerve neuralgia are reported as occupational illnesses. The mechanism is often some type of pressure over the anterior part of the iliac crest from heavy belts or other equipment, especially if loaded with tools or other weights. Edema, tiredness, and dull pain in the legs are more common in those with static sitting or standing occupations than in those who work in a more varied posture.37 Compartment syndromes are rarely due to occupational loading of the lower extremities. This syndrome is more often seen as a result of sports activities and as a complication of fractures and other traumatic injuries.
Rheumatic diseases Arthritis and rheumatism account for 66% of the musculoskeletal conditions among women and 51% among men. Osteoporosis accounts for an additional 11% of musculoskeletal disease, occurring predominantly in females.25 Rheumatic diseases are not caused by occupational loading but may be worsened by it.
Table 7a.2 Prevalence of osteoarthritis as diagnosed by history or examination by gender and age group: rate per 100 persons Diagnosis by history
Diagnosis by examination
Age
Males
Females
Males
Females
Less than 20 years 20–39 years 40–59 years Over 60 years All ages All ages over 20 years
— 0.2 3.4 17.0 1.9 4.5
— 0.4 8.4 29.6 4.0 7.3
— — 4.0 20.3 2.2 4.2
— 0.2 8.9 40.8 5.0 9.0
Perthes disease). Primary OA has been shown to have a multifactorial background. Bilateral hip and knee OA has been suggested to have an etiology different from that of unilateral OA. Hochberg13 reported on a group of 1337 students who graduated from The Johns Hopkins University School of Medicine from 1948 through 1964. The cumulative incident of knee OA at age 65 was 6.3%, whereas hip OA existed in 2.9% of individuals. Cumulative knee OA relative rise was three times higher in those with a history of knee injury (13.9% vs. 6%). The incidence of knee OA was 7.5 per 1000 person-years among those with a knee injury compared with 1.2 per 1000 person-years, for a relative risk (RR) of 5.2. Similarly for the hip, the incidence was 3.2 per 1000 person-years among those with hip injury compared with 0.7 without a hip injury (RR, 3.5). The increased risk remained significant even after adjustment for age, sex, body mass index, and physical activity at study entry. Clearly, lower leg injuries should be prevented to reduce the risk of knee and hip OA.
Heredity
Osteoarthritis The prevalence of OA is greater in women than in men. Physical examination more often results in a diagnosis of OA, as compared with radiographic examination, when narrowing of the joint space is used as the criterion. If osteophytosis is included as a sign of OA, the prevalence is much higher. Around 12% of the U.S. population have OA in any joint.8,12,18 Table 7a.2 shows the prevalence of OA diagnosed by radiographic examination in different age groups.18,25 Diagnosis by examination revealed more OA than diagnosis by history. The explanation is that many individuals are symptom free. In the NHANES I study,2 the prevalence of OA of the knee was 2.3% to 18% in those aged 45 to 74 years, with a larger prevalence in the elderly and in women. Hip OA was found in 0.2% to 6.6% in those aged 25 to 74 years, more in the elderly but with less sex difference than OA in the knee. OA of the hip and knee has been studied in relation to occupational and other factors. These results were confirmed in recent studies.1,6 Secondary OA is due to previous known trauma (e.g., fracture, surgery) or disease (e.g., hip dysplasia, osteochondritis,
Most OA is not attributable to single genes. Rather, common OA appears to result from interactions between multiple genes and the environment. In a comparative population study in San Francisco, standardized rates of primary hip OA, expressed as numbers per 100,000 population per year, were 1.5 in Japanese, 1.5 in Chinese, 1.6 in Filipinos, 5.1 in Hispanics, 8.3 in blacks, and 29.4 in whites. The hereditary factor often results in a more generalized OA in different locations of the body.22 The percentage of hip OA, defined as lowered height of the joint cartilage, at 70 years of age in Sweden is about 2% in both sexes. Knee OA has a prevalence of 2% in men and 3% in women at 70 years of age in Sweden. However, a relation to occupational loading or sports is more clearly shown in men, whereas obesity correlates more with knee OA in women. Consequently, a hereditary factor increasing the risk for females to contract OA of the knee is likely.22 Obesity correlates with symptomatic OA in the hip31 and also in the knee, which is clearly shown in females, and has an RR of about 4.10,22
Hip OA Sports Lindberg and Montgomery20 found a 2.8% prevalence of hip OA in control subjects as compared with 5.6% in athletes
Chapter 7a
●
References
and 14% in elite athletes (soccer players). Similar results have been shown by Klunder et al.16 Among those undergoing a total hip procedure because of OA, Vingård et al32-34 found an RR of 4.5 for athletes. Those athletes who also had a physically demanding job had an RR of 8.5. Different results have been shown in studies of long-distance runners.9
carry an increased risk for OA. Other physically demanding jobs have less of an increase in RR for OA, around 2 to 3, similar to the RR for obesity and lower than the increased risk in some elite athletes.22
Occupation Vingård et al32-36 found more symptoms caused by hip OA in men exposed to greater physically demanding jobs. Farmers, construction workers, firefighters, and food processing workers had significantly more OA than expected (RR, 2.4). For those exposed to both occupational loading and sports activities the RR was 8.5, and for sports alone the RR was 4.5. In this study, being overweight had an RR of 2.5. Disability pension for hip OA was more often received by those with high occupational load exposure than by those with low exposure (RR, 12.4).33 The risk occupations were construction workers, metal workers, farmers, and forestry workers. An increased risk for hip OA has been shown in farmers, with RRs of 9.7 to 12 in several studies.4,7,11,15,19,27 In female farmers, no difference from control subjects was found.4
REFERENCES
Knee OA
8.
Sports A Swedish study22 found a knee OA prevalence of 7% in
9.
soccer players as compared with 1.6% in control subjects. The prevalence was higher in those with known meniscal tears or anterior cruciate ligament ruptures.
1.
2.
3. 4. 5. 6.
7.
10.
11.
Occupation The Framingham study showed an odds ratio of 2.2 for OA of the knee in jobs requiring knee bending and at least a medium level of physical activity.10 The etiologic fraction or attributable proportion of knee OA to occupational physical loading was 15%. Obesity accounted for 10%. Only a few females had physically demanding jobs in the study, and no gender association was found.10 In the NHANES study, knee OA was increased among men and women with physically demanding jobs: odds ratios of 1.88 in women (not significant) and 3.13 in men of younger ages, and odds ratios of 3.49 and 2.45, respectively, at higher ages. The occupational etiologic fraction was estimated to be 32%.2 Dock workers have been shown to have more knee OA than office workers.24 Lindberg and Montgomery20 found an increasing risk for knee OA in shipyard workers as compared with office workers and teachers. Vingård et al32-34,36 found an increased risk for knee OA among farmers, construction workers, and firefighters. That study also showed an increased risk of knee OA symptoms in female janitors and letter carriers. Therefore, a moderately increased risk of symptom-giving knee OA has been shown in physically demanding occupations.4,17,21 Overweight and some sports activities seem to increase the risk of symptom-giving knee OA more than any occupation. A consensus discussion in 1992 in Malmö on the etiology of OA concluded that unfavorable weight bearing and repeated minor trauma may contribute to OA.22 This is in agreement with the current etiologic hypotheses. Static load, repeated trauma over long periods, and an unnatural use of joints are likely to contribute to OA. Regarding occupation, farmers, professional ballet dancers,3 and professional soccer players have a much higher frequency of OA than expected and are therefore considered to
12. 13.
14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.
30.
Andersen RE, Crespo CJ, Ling SM, Bathon JM, Bartlett SJ: Prevalence of significant knee pain among older Americans: results from the Third National Health and Nutrition Examination Survey. J Am Geriatric Soc 47(12):1435-1438, 1999. Andersson JJ, Felson DT: Factors associated with osteoarthritis of the knee in the first National Health and Nutrition Examination Survey (NHANES I): evidence for an association with overweight, race, and physical demands of work. Am J Epidemiol 128(179):89, 1988. Andersson S, Nilsson B, Hessel T, et al: Degenerative joint disease in ballet dancers. Clin Orthop 238:233-236, 1989. Axmacher B, Lindberg H: Coxarthrosis in farmers. Clin Orthop 287:82-86, 1993. Bergenudd H: Talent, occupation, and locomotor discomfort. Doctoral thesis. Malmö, Sweden, 1989, Lund University. Christmas C, Crespo CJ, Franckowiak SC, Bathon JM, Bartlett SJ, Andersen RE: How common is hip pain in older adults? Results from the Third National Health and Nutrition Examination Survey. J Fam Pract 51(4):345-348, 2002. Croft P, Coggon D, Cruddas M, Cooper C: Osteoarthritis of the hip: an occupational disease in farmers. BMJ 304:1269-1272, 1992. Cunningham LS, Kelsey JL: Epidemiology of musculoskeletal impairments and associated disability. Am J Public Health 74:574-579, 1984. Ernst E: Jogging-for a healthy heart and worn out hips? J Intern Med 228:295-297, 1990. Felson DT, Hannan MT, Naimark A, et al: Occupational physical demands, knee bending and knee osteoarthritis: results from the Framingham study. J Rheumatol 18:1587-1592, 1991. Forsberg K, Nilsson B: Coxarthritis on the island of Gotland. Increased prevalence in a rural population. Acta Orthop Scand 63:1-3, 1992. Hadler NM: Occupational musculoskeletal disorders. New York, 1993, Raven Press. Hochberg MC: Prevention of lower limb osteoarthritis: Data from the John Hopkins Precursor Study. In VC Hascall, KE Kuettner, eds: The many faces of osteoarthritis. Berlin, 2002, Birkuauser. Hult L: The Monkfors investigation. Acta Orthop Scand Suppl 16:1-76, 1954. Jacobsson B, Dalén N, Tjörnstrand B: Coxarthrosis and labour. Int Orthop 11:311-313, 1987. Klunder KB, Rud B, Hansen J: Osteoarthritis of the hip and knee joint in retired football players. Acta Orthop Scand 51:925-927, 1980. Kohatsu N, Schurman D: Risk factors for the development of osteoarthritis of the knee. Clin Orthop 261:242-246, 1990. Lawrence RC, Hochberg MC, Kelsey JL, et al: Estimates of selected arthritic and musculoskeletal diseases in the U.S. J Rheumatol 16(4):427-441, 1989. Lindberg H, Axmacher B: Coxarthrosis in farmers. Acta Orthop Scand 59:607, 1988. Lindberg H, Montgomery F: Heavy labor and the occurrence of gonarthrosis. Clin Orthop 214:235-236, 1987. Nicolaisen T: Health among postmen. Copenhagen, 1983, General Directorate for Post and Telegraph (in Danish). Nilsson BE: The Tore Nilson Symposium on the etiology of degenerative joint disease. Acta Orthop Scand Suppl 64(253): 54-61, 1993. Nordin M, Frankel VH: Basic biomechanics of the musculoskeletal system, ed 2. Philadelphia, 1989, Lea & Febiger. Partridge REH, Dulthie JJR: Rheumatism in dockers and civil servants. Ann Rheum Dis 27:559-568, 1968. Praemer A, Furner S, Rice DP: Musculoskeletal conditions in the United States. Park Ridge, IL, 1992, AAOS. Praemer A, Furner S, Rice DP. Musculoskeletal conditions in the United States. Rosemont, IL, 1999, American Academy of Orthopedic Surgeons, pp. 1-182. Thelin A: Hip joint arthrosis: an occupational disorder among farmers. Am J Ind Med 18:339-343, 1990. Törner M: Musculoskeletal stress in fishery: causes, effects, and preventive measures. Doctoral thesis. Sweden, 1991, University of Göteborg. Törner M, Zetterberg C, Anden U, Hansson T, Lindell V: Workload and musculoskeletal problems: a comparison between welders and office clerks. Ergonomics 34:1179-1196, 1991. Törner M, Zetterberg C, Hansson T, Lindell V, Kadefors, R: Musculoskeletal symptoms and signs and isometric strength among fishermen. Ergonomics 33:1155-1170, 1990.
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31. 32. 33.
34.
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Epidemiology of the lower extremity
Vingård E: Overweight predisposes to coxarthrosis. Body mass studied in 239 males with hip arthroplasty. Acta Orthop Scand 62:106-109, 1991. Vingård E: Work, sports, overweight and osteoarthrosis of the hip. Arbete och Hälsa 25, doctoral thesis, 1991, Karolinska Institute, Stockholm, Sweden. Vingård E, Alfredsson L, Fellenius E, Hogstedt C: Disability pensions due to musculoskeletal disorders among men in heavy occupations. Scand J Soc Med 20:31-36, 1992. Vingård E, Alfredsson L, Goldie I, Hogstedt C: Sports and osteoarthrosis of the hip. Am J Sports Med 21(2):195-200, 1993.
35.
36. 37.
Vingård E, Alfredsson L, Hogstedt C, Goldie I: Ökad risk för arthros i knän och höfter för arbetare i yrken med hög belastning på benen. Läkartidningen 87:4413-4416, 1990. Vingård E, Hogstedt C, Alfredsson L, Fellenius E, Goldie I, Koster M: Coxarthrosis and physical work load. Scand J Work Environ Health 17:104-109, 1991. Winkel J: On fast swelling during prolonged sedentary work and the significance of leg activity. Arbete och Hälsa, doctoral thesis, Stockholm, 1985, National Institute of Occupational Health.
CHAPTER
7b
Biomechanics of the Hip and the Knee Ali Sheikhzadeh
Biomechanical analysis of the hip and knee joints during daily activities that occur in the home and work environment can identify tasks that are potentially harmful for a healthy and an injured joint. A kinematics and kinetic profile of uninjured joints provides an understanding of joint contribution during functional tasks, provides a baseline to identify abnormalities, and thereby assists with diagnosis and treatment. Moreover, it facilitates the design and performance of reconstructive surgery and rehabilitation programs. The kinematics and kinetics of the hip and knee joints and the joint forces that occur during activities of daily living are the focus of this chapter. The application of biomechanical models for calculating external forces and moments at the hip and knee joints is explained first. The application of biomechanical concepts in reducing joint forces and thereby risk of injury is then discussed. The activities discussed are mainly physical activities of daily living and those commonly performed at work such as gait, stair climbing, rising from a chair, and lifting weights.
KINEMATICS OF THE HIP AND KNEE A three-dimensional measurement of relative motion among adjacent limb segments, comprehensive kinematics analysis is expressed by 6 degrees of freedom, generally three translational and three rotational angles. However, kinetics analysis involves both static and dynamic analysis of internal and external forces and moments acting on a joint. In the musculoskeletal system, external forces frequently include the ground reaction forces, the weight of the limb segment, and the force of one segment on another. Muscle contractions, passive soft tissue stretch, and articular reaction forces generate primarily internal forces.
Kinematics of the knee The knee joint is composed of the tibiofemoral joint and the patellofemoral joint. The tibiofemoral joint has the greatest motion in the sagittal plane, 0 to approximately 140 degrees. Provided by articulations between large convex femoral condyles and smaller or nearly flat tibia condyles, this large range allows extensive knee motion in the sagittal plane for the activities such as walking, running, squatting, and climbing. The knee motion in the transverse plane (internal and external rotation) and in the frontal plane (abduction and adduction) is affected by the amount of joint flexion. The interlocking of the
femoral condyles in the knee in extension precludes almost any motion in the frontal and transverse planes. The knee motion in the transverse plane increases as the knee is flexed toward 90 degrees, with a maximum of approximately 45 degrees in internal rotation and 30 degrees in external rotation, and then decreases primarily due to the soft tissue restrictions. Similarly, motion in the frontal plane increases as the knee is flexed toward 30 degrees, reaching a maximum of only a few degrees of abduction and adduction, and then decreases as the knee flexion goes beyond 30 degrees. Values for the average range of motion of the knee joint in the sagittal plane during 11 common activities are reported in Table 7b.1. A range of motion of 130 degrees is required for common daily living activities. Excluding the range of motion required to bathe, 11061 to 117 degrees51 of knee flexion would seem a reasonable goal for the rehabilitation of its motion for the general population. The inability of the knee to move within the range of motion required for daily living activities would be compensated for by increasing the motion of other joints51 or avoiding trying to perform the task.
Kinematics of the hip The hip joint is a synovial ball-and-socket joint with articulation between the large nearly spherical head of the femur and the acetabulum of the pelvis. With its inferior anterolateral and inferior opening, the acetabulum provides a wide range of motion. The concave acetabulum covers about two thirds of a spherical femur head. As the hip joint is loaded, the acetabulum deforms about the femoral head. The unloaded acetabulum has a smaller diameter than that of the femoral head.21 Hip motion takes place in all three planes, with the greatest motion in the sagittal plane. The extreme motion of the hip joint is limited by passive tension of the surrounding ligaments and muscles (Table 7b.2). Passive hip flexion is approximately 140 degrees, whereas active hip flexion with the knee flexed is 125 degrees and with it extended is 90 degrees. Passive hip extension is approximately 30 degrees, whereas active extension is 20 degrees.59
Table 7b.1 The mean of the left knee joint angle performed by 20 normal elderly subjects during 11 functional activities Function
Mean
Level walking Ascend slope Descend slope Ascend stairs Descend stairs Sit down low chair Sit to stand low chair Sit down standard chair Sit to stand standard chair Into bath Out of bath
64.5 61.6 69.0 80.3 77.8 92.5 95.0 91.0 89.8 123.3 131.3
Rowe PJ, Myles CM, Walker C, Nutton R. Gait Posture 12:143-155, 2000.
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Magnitude of hip range of motion and associated limiting ligaments and muscular tissues
Hip motion
Magnitude of hip motion
Examples of tissues that may limit the extremes of motion
Flexion
80° (with knee extended) 120° (with knee fully flexed)
Extension
20° of extension (with knee extended)*
Abduction Adduction
0° (with knee fully flexed) 40° 25°
Internal Rotation Extrenal Rotation
35° 45°
Hamstrings and gracilis muscles Inferior fibers of ischiofemoral ligament Inferior capsule Predominantly iliofemoral ligament and anterior capsule; some components of the pubofemoral and ischiofemoral ligaments Rectus femoris muscle Pubofemoral ligament, inferior capsule, adductor and hamstring muscles Superior fibers and ischiofemoral ligament, iliotibial band, and abductor muscles such as the tensor fasciae latae Ischiofemoral ligament external rotator muscles (e.g., piriformis) Lateral fasciculus of iliofemoral ligament, iliotibial band, and internal rotator muscles (e.g., gluteus minimus, tensor fasciae latae)
*Implies 20° of extension beyond the neutral zero degree position. From Neumann, DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation. St. Louis, 2002, Mosby; p. 400.
The hip abduction range is about 30 degrees, and adduction range is about 25 degrees. The external and internal rotations of the hip are 90 and 70 degrees, respectively, when the joint is flexed. The internal and external rotations of the hip, when it is extended, are approximately 15 and 35 degrees, respectively.59 Most common daily activities require flexion, abduction, and external rotation. The mean of motion during selected daily activities is shown in Table 7b.3. Most daily activities require more than 100 degrees of hip flexion.30 Squatting and shoe tying with the foot across the opposite thigh require the greatest motion in the frontal and transverse planes. Walking on a level surface requires about 30 degrees of flexion and 10 degrees of extension, with minimal abduction-adduction and internal-external rotation. Approximately 80 to 104 degrees of flexion and extension, respectively, is required to sit on or rise from a chair. The range of motion during daily activities should be interpreted cautiously. The reported range has been shown to be influenced by age,23 speed of movement,15 and environmental task constraints such as chair46 and stair height. Mulholland and Wyss44 demonstrated the significance of cultural sensitivity in the interpretation of daily activities. In many parts of Asia and the Middle East, a chair is not commonly used at home or work, and sitting on the floor without support, sitting cross-legged, or kneeling are more common than in Western countries.22,44 Mulholland and Wyss44 suggested that even rural as opposed to urban life-styles in different geographic locations might demand significantly different analytical approaches and should be considered in evaluations of daily physical activities. The current related literature on daily living activities, including data reported in Tables 7b.1 and 7b.3, reflects mainly the Western life-style and would not apply to the actual life-styles of many people in Asian and Middle Eastern cultures. There is a growing need for culturally and racially sensitive data that allow for individual variation in the normal range of motion.
require gross oversimplification of forces and coincide with the theoretical assumption of the model itself. However, the reliability and validity of biomechanical models depend on realistic assumptions and representations of the mechanical system and accuracy of the experimental data that constitute the inputs and/or outputs. In addition, an important aspect of developing a model is to decide what should be included or neglected. Although it is not always possible, generally the simplest model that provides a valid representation of reality should be used.
Table 7b.3 Mean values for maximum hip range of motion measured in three planes during several common activities for 33 healthy men
KINETICS OF THE HIP AND KNEE Generally, a biomechanical model attempts to represent a simplified version of a complex task. Often these representations may
Johnston RC, Smidt GL: Hip motion measurement for selected activities of daily living, Clin Orthop 72:205-215, 1970.
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(cm) 10.0
Glut eu s
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Figure 7b.1 A side view of the femoral head with the line-of-action of several muscles crossing the hip in the sagittal plane. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation. St. Louis, 2002, Mosby, p. 400.)
The formulation of a comprehensive dynamic model of the knee and hip joints is challenging because of the complexity of internal forces acting on the joints and the difficulty of measuring anatomic parameters precisely. For instance, a comprehensive model of the hip joint should include the line-of-action of muscles crossing it with respect to its axes of rotation in the sagittal and frontal plane, as presented in Figure 7b.1. In addition to the line-of-action of muscles, such a model should consider the dynamic changes of these parameters during joint motion. The following methods are used to overcome the difficulty and complexity of estimating the internal joint forces during dynamic tasks.
Analytical joint models Often, even the simplest model of external forces generated by gravity acting on the body provides crucial functional and clinical information about a joint. As illustrated in Figure 7b.2, for instance, a simplified free-body diagram of the lower extremity during a single leg stand phase of stair climbing presents a reasonable estimate of the tibiofemoral joint forces and patella tendon force. The flexion moment of the lower leg is the product of the body weight (BW) and its lever arm, the perpendicular distance of the BW to the center of the tibiofemoral joint motion. The sensitivity
Figure 7b.2 Free-body diagram of moments acting around the center of motion of the tibiofemoral joint during stair climbing. The ground reaction force (W) and its lever arm (a) are counterbalanced by moments produced by the quadriceps muscle force through the patellar tendon (P) and its lever arm (b). (From Nordin M, Frankel VH: Biomechanics of the knee. In M Nordin, VH Frankel, eds: Basic biomechanics of the musculoskeletal system. New York, 2001, Lippincott Williams & Wilkins, pp. 176-201.)
of the knee flexion moment to the carrying of objects during occupational tasks can be determined by adding the weight of an object to the external weights acting on the body. Despite the oversimplification of the joint forces that may be estimated based on a free-body diagram, a two-dimensional static model can be used to analyze occupational tasks or to design rehabilitation training. Typically, a person with arthritis pain or patellofemoral joint pain is advised to avoid large forces created by the quadriceps.12 Figure 7b.3 illustrates the magnitude of the external forces on the knee during two physical tasks requiring knee extension, tibial-on-femoral knee extension (the line between D and B) verses the femoral-on-tibial knee extension during the 0 to 90-degree joint angle (the line between A and C). During tibial-on-femoral knee extension, the external moment arm of the weight of the lower leg increases from 90 degrees to 0 of knee flexion. In contrast, during femoral-on-tibial knee extension, the external moment arm of the upper BW decreases from 90 degrees to 0 of knee flexion. A more realistic biomechanical model of the knee should include a better representation of the patellofemoral stresses and forces within the quadriceps muscle. The single line of quadriceps force in Figure 7b.2 should be replaced by four lines. The four heads of the quadriceps muscle consist of distinct fibers that
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B
A External Torque-Angle Plot 100%
70%
Relative external torque (% maximum)
0% D
90º
70º
45º
20º
0º
C
Knee angle (degrees) EXTENSION
Figure 7b.3 The relative external torque generated by body weight acting on the knee joint between 90-degree flexion and full extension (0 degree) during two styles of knee extension: (1) during femoral-on-tibial extension (A to C line), the external moment arm of the weight of the lower leg increases from 90-degree knee flexion to full knee extension, and (2) during tibial-on-femoral extension (D to B line), the external moment arm of the upper-body weight decreases from 90 degrees to 0 knee flexion. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation. St. Louis, 2002, Mosby, p. 458.)
approach the patella at different angles, especially the vastus medialis fibers, which approach from two distinct directions. The more distal oblique fibers approach the patella at 50 to 55 degrees, and the remaining more longitudinal fibers approach it at 15 to 18 degrees, both medial to the quadriceps tendon.49 Cohen et al12 presented a more comprehensive model of the knee joint, computer simulated with geometric and anatomic details, to compare the patellofemoral stresses and quadriceps force during open (with 0, 25-N, and 100-N load at ankle) and closed kinetic chain leg exercises in the flexion range of 20 to 90 degrees. As demonstrated in Figure 7b.4, the quadriceps muscle force and the average patellofemoral contact forces increase progressively from 20 to 90 degrees. To achieve a more realistic estimate of joint forces, a biomechanical model of the hip and knee joint should include the soft tissues forces such as agonist-antagonist muscle forces in threedimensional dynamic environments. The exclusion of agonistantagonist muscle forces underestimates the internal joint forces. However, the inclusion of these forces adds another layer of complexity to the model and demands more advanced analytical methods to solve indeterminate systems. Generally, inverse dynamic models47 or optimization methods4,56 are used to solve the indeterminate problem of determining muscle and contact forces. For example, with the large number of muscles crossing the hip (Fig. 7b.1) and with at least 27 separate musculotendinous units crossing the joint, a unique demonstration of individual muscle force can be achieved only by oversimplification. Today’s advances in computer science and technology provide the possibility of creating “virtual human” reality.10 The virtual
human concept aims at understanding human activities through the simulation of accurate physiologic and anatomic models and data. This type of simulation combines biomechanical models of joints and mechanical properties of connective tissues to visualize
Figure 7b.4 Quadriceps muscle force exertion simulation based on anatomical data from five cadavers for closed kinetic chain (CKC) and open kinetic chain (OKC) exercises for knee flexion range of 20 to 90 degrees. The three OKC loading simulated conditions are OKC 0N, knee extension with no load; OKC 25N, leg extension with 25-N external force at the ankle; OKC 100N, leg extension with 100-N external force at the ankle. (From Cohen ZA, Roglic H, Grelsamer RP, et al: Patellofemoral stresses during open and closed kinetic chain exercises: an analysis using computer simulation. Am J Sports Med 29:480-487, 2001.)
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the results in both static and animated forms. For surgical implantation of a proximal femur/hip prosthesis, for example, graphic information about implants that is available directly from the manufacturers or CAD/CAM files can be added to real images of the patients’ anatomic parameters taken from computed tomographies. It can also be incorporated into the biomechanical models of joints and soft tissues in functional tasks. For surgical and medical education and for device development applications, it is worthwhile to incorporate adaptive anatomic models, which include prosthetic implants and fracture fixation devices. Advanced computation environments for static posture, kinematics, kinetics, and stress analysis under physiologic boundary and loading conditions can be incorporated.
In vivo direct measurement of joint forces Although biomechanical models deal with indirect estimates of internal forces, the real-time continuous signal from an instrumented telemetric prosthesis has been used for direct measurement of internal forces acting on the distal or proximal femur during daily activities such as walking and stair climbing.69 Direct measurement of the hip contact forces was first obtained by Rydell.62 The peak hip forces during gait vary from 1.8 to 4.3 times the BW, with peak pressure occurring during heel strike and early midstance.4 These hip forces are related to the ground reaction forces acting on the superior anterior acetabulum. For patients measured at 11-31 months postoperatively, the average hip forces during fast walking and climbing stairs was about 250% BW and slightly less than going downstairs.7 Taylor and Walker69 studied two patients over 2.5 years during various daily activities. The average peak distal femoral shaft forces for one patient during various activities were jogging 3.6 BW, stair descending 3.1 BW, walking 2.8 BW, treadmill walking 2.75 BW, and stair ascending 2.8 BW. Bending moments about the mediolateral axis (flexion-extension) and anteroposterior axis (varus-valgus) peaked in the range of 4.7-7.6 BW cm and 8.5-9.8 BW cm, respectively, over the follow-up period. During similar activities, however, forces and moments for the second subject were generally 45-70% less than those for the first subject due to inadequate musculature around the knee.69 The joint forces and moments of patients who have had joint arthroplasty are expected to return to the values of healthy individuals within approximately 6 months after surgery.2 The discrepancy between forces and moments reported by various authors, for example, Bergmann et al7 and Taylor and colleagues,69,70 reflect the variation among individuals, success of surgery, location of measured forces, and time of study with respect to surgery. For example, Taylor and Walker offer a good estimate of the loading conditions (distal femoral) acting at the knee and are assumed to offer data different from what Bergmann and colleagues found with respect to hip arthroplasty surgery. In comparison with biomechanical models, direct measurement produces valid data on internal forces. The information serves mostly as validation9,39,65 for biomechanical models and provides useful insight into wear, strength, and fixation stability. Direct measurement is otherwise difficult because of technologic restrictions and ethical considerations, and because of a variety
of practical reasons only a limited number of subjects can be studied.69 Because the validity of collected information depends on the extent to which joint mechanics and surrounding tissues have been altered, generalizations cannot be made.
REDUCING INTERNAL JOINT LOAD: APPLICATION OF BIOMECHANICAL CONCEPTS Determining the consequence of daily physical activities of work and leisure on lower extremity joints is difficult because of the complexities of structural anatomy and dynamic movements combined with the calculation of internal and external forces acting on joints. Musculoskeletal loading is influenced by a number of individual differences such as age, weight, and gender; the activity itself; and the variables of the task. Such factors help explain individual variation in functional abilities, biomechanical consequences of physical performance on internal tissues, and potential risk or mechanism of injury. Biomechanical analysis of physical activities such as walking, running, and stair climbing provides understanding of internal and external forces acting on a joint and their significance for injury and pain. Biomechanical analysis of task variables such as stair or chair height influence and gait speed demonstrate the degree to which selected characteristics of a task may influence the physical demands of executing it and its consequences for joints and surrounding tissues. The following is a brief description of selected variables that directly or indirectly influence physical ability and musculoskeletal loading during daily living activities.
Individual factors Individual factors such age, gender, anatomic variation, and medical history and disease stage are known directly or indirectly to influence ability, internal resources for executing a task, and distribution of internal forces and tissue tolerance. Except for weight, individual factors cannot be controlled or altered, but understanding a mechanism by which these factors may influence joint loading is important to explain injury mechanism, prevent injury risk, and design rehabilitation programs for special groups of individuals.
Age, weight, and gender Individual factors such as age,1,15,16,21,34,58 weight,1,11 and gender35,36,67 influence the internal joint forces and ultimately the injury mechanism and risk. Biomechanical properties of soft tissues and the hip and knee joints are known to be different between genders and to change with age in a highly individualized process and rate. They may be modified negatively or positively by many factors such as activity types and frequency, medical conditions, and nutritional factors. The alteration of posture, active and passive range of motion of the hip and knee joints, and gait during physical activities are associated with age and gender as well.51 An individual’s weight and height directly influence the hip and knee joint moments.71 Height can influence limb size and therefore lever arm. Daily physical activities such as walking and
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stair climbing exert 3.5 BW on hip and knee forces. A change of 5 pounds of BW, for instance, may therefore result in 17.5 pounds of excess force in the knee and hip. Additionally, an individual’s weight has been associated with the prevalence of joint pain1 and change in properties of tissue characteristics.11 Aging is associated with a decrease in neuromuscular control characterized by the decline of maximum muscle force production, the velocity of contraction, and the dynamic stability.33 Human muscle strength attains its peak between the ages of 20 and 30 years and declines gradually until the age of 60 and rigorously thereafter.31 During the single-leg support phase of walking and stair climbing, while the body is moving forward, lower extremity muscular strength is required to control and support it.34 Often a lack of joint strength or an inability to develop torque within the appropriate time may contribute to the risk of injury.71 Stair descent by the elderly has previously been described as a “controlled fall” due to the lack of ankle flexibility and strength as well as the delay in developing torque rapidly.72 It has been suggested that absolute task demands for performing activities of daily living are not significantly high; however, older adults’ difficulty in performing these activities must take
into account their decrease in capacity.23 Using inverse dynamics analysis, Figure 7b.5 compares the knee joint moments of healthy young and older adults during stair ascent and descent and when rising from a chair compared with maximal isometric effort in supine leg press. Although there is no significant difference between absolute knee moments during physical activities, motor tasks demand substantially greater effort relative to available maximum capacity of elderly compared with young adults. As illustrated in Figure 7b.5, relative effort was significantly higher for stair ascent, 54% for younger compared with 78% for older adults, stair descent required 42% compared with 88% relative effort, and chair rising required 42% compared with 80%. Compared with young adults, the elderly walk at a significantly higher rate of oxygen uptake (about 20% more) and physiologic relative effort, that is, the ratio of the required oxygen uptake to the available maximal capacity.5,23 Age has been hypothesized to cause a redistribution of joint torques and power during gait. DeVita and Hortobagyi15 reported that during self-selected walking speed, elderly adults had 58% greater angular impulse and 279% more work at the hip and 50% less angular impulse and 29% less work at the knee compared with young adults. Similarly, they reported 23% less angular
Figure 7b.5 Mean of body mass-normalized knee joint moments for healthy young adults of 22 years and old adults with a mean age of 74 years during stair ascent (A), stair descent (B), and sit-to-stand (C). For stair ascent and descent, one cycle represents the initial foot contact (0) with the stair to toe-off (100%). For rising from a chair, one cycle corresponds to lift-off (0) to fully erect position at the end of the rise (100%). The bar graphs represent the group mean of the maximal isometric knee joint moments measured at specific knee joint positions in a leg press task. Solid lines and filled columns indicate older adults, and dashed lines and open columns denote young adults. (From Hortobagyi T, Mizelle C, Beam S, DeVita P: Old adults perform activities of daily living near their maximal capabilities. J Gerontol A Biol Sci Med Sci 58:M453-M460, 2003.)
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impulse and 29% less work at the ankle for the elderly compared with young adults. The elderly use less of the ankle plantar flexors and knee extensors and more of the hip extensors.15
Anatomic variation In addition to variation in the size of muscle and bone, many known anatomic variations directly influence the hip and knee joint forces. For instance, the femoral neck has two angular relationships with the femoral shaft: the neck-to-shaft or inclination angle and the torsion or anteversion angle. The inclination angle of the femur is referred to the relation of the femur neck with the shaft in the frontal plane. The inclination angle is about 140 to 150 degrees at birth and usually reduces to approximately 125 degrees, with a range of 90 to 135 degrees in adulthood. These abnormal angles alter the alignment between the acetabulum and femoral head and thereby alter the hip moments by changing the lever arm and the effect of upper body forces on the joint. The inclination angle may have positive and negative biomechanical effects.49 The torsion angle of the femur is the relative rotation that exists between the neck and the shaft. Normally, an infant is born with about 30 degrees of torsion angle that usually decreases to 15 degrees by 6 years of age.55,75 Excessive anteversion is often associated with a tendency toward internal rotation of the leg during gait, change of contact area between the femoral head and the acetabular,50 and wear on the articular cartilage. The Q-angle is another reported anatomic variation. During active knee extension and passive stretch, several structures guide the patellar movement with respect to the tibiofemoral joint. Although each structure alone may force medial or lateral movement of the patella, the net result of these forces moves it through the groove with minimal stress to the articular surfaces. The degree that the quadriceps tends to pull the patella is known as the Q-angle, which varies between the genders24 and is not bilaterally symmetric.37,38 A Q-angle of greater than 15-20 degrees is often thought to contribute to high articular stress and the poor tracking of the patella, thereby leading to arthritis, chondromalacia, recurrent patellar dislocation, or patellofemoral joint pain syndrome. Although in apparently normal anatomic structure the Q-angle and femoral neck angle of inclination and torsion is not necessarily consistent with the appropriate knee and hip joint loading during physical activities, the abnormal range of these angles is usually an indication of abnormal joint loading and pain.
Medical history and disease stage Medical history such as osteoarthritis45 and ligament deficiency35,67 may alter the kinematics and kinetics of the hip and knee joints directly or indirectly. Hip and knee osteoarthritis results from degenerative changes in cartilage that to some extent result from arbitrary increases in joint loading.19 For instance, patients with advanced knee osteoarthritis walk with lower ground reaction forces and reduced sagittal plane range of motion,45,66 increased knee adduction moment,6 decreased stride length,3 and increased angling out of the toes.73 Although self-selected walking speed has been reported to explain only 8.9% of the variation in the maximum knee adduction moment, a patient’s walking style is associated with the severity of knee osteoarthritis.45 One study has shown that knees with more severe osteoarthritis have greater
adduction moments and more varus alignment than those in which osteoarthritis is less severe.45 Figure 7b.6 demonstrates the magnitude and slope of the theoretical relationship between the maximum knee adduction moments and the walking speeds for two groups of patients with different degrees of knee osteoarthritis severity compared with asymptomatic control subjects matched for age and sex. The variation of the slopes in Figure 7b.6 indicates that adopting different walking speeds may not equally benefit osteoarthritis patients. Patients with less severe knee osteoarthritis walk with unique gait mechanics that are different from those of the control group and those of patients whose knee osteoarthritis is more severe.45 Similarly, other studies have demonstrated the effects of hip osteoarthritis and pain on the hip forces and gait.25 In summary, the kinematics and kinetics of the knee and hip joints are directly or indirectly influenced by individual factors. A brief discussion of some of these factors mainly serves as an example of how they may influence hip and knee joint forces. Although these individual factors cannot be controlled or modified, understanding their relationship with their influencing mechanism helps to explain the individual’s tolerance, ability to perform physical tasks, neuromuscular adaptation, and variation in the magnitudes of joint forces. Whereas most reported studies in this section discuss and compare healthy individuals with certain groups such as the elderly or individuals with severe osteoarthritis, who may not represent the working population, the information can still demonstrate the process and direction of biomechanical change.
Less severe knee OA
Maximum knee adduction moment (% body weight • height)
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2.0
More severe knee OA
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Walking speed (m/s) Figure 7b.6 Relationship between maximum knee adduction moment and self-selected walking speed for three groups of subjects: patients with knee osteoarthritis (OA) of lesser and greater severity and matched control subjects. (From Mundermann A, Dyrby CO, Hurwitz DE, Sharma L, Andriacchi TP: Potential strategies to reduce medial compartment loading in patients with knee osteoarthritis of varying severity: reduced walking speed. Arthritis Rheum 50:1172-1178, 2004.)
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Reduction of joint forces and moments Many physical activities such as walking, running, and stair climbing involve coordinated cyclic movements of several joints. Often, the comprehensive kinetic and kinematics analysis of single joints such as the hip or knee requires understanding their function in relation to other joints and their crossing muscles. The internal joint forces during dynamic physical activities are produced by BW, externally carried loads, and internal soft tissue forces such as muscles. A practical method of reducing joint force is to reduce the lever arm and impact of external forces. Several biomechanical and physiologic factors underlie the mechanism to reduce joint loads during physical activities and thereby risk of injury.
Reducing the lever arm The primary function of the hip joint is to support the weight of the head, arm, and trunk both in static erect posture and in dynamic activities such as walking, running, and stair climbing. The most effective means of reducing the joint forces during daily activities is to find a practical method of reducing the magnitude of either these forces or the lever arm. The hip and knee joint forces need to be understood largely in the context of action of the upper BW on the lower extremity. For example, the magnitude of the torques on the hip joint during upright standing is equal to the weight of the upper body (W), which is equal to two thirds of BW50 times the distance of this force from the hip joint axis. As shown in Figure 7b.7A, during a single-legged stance, assuming the lever arm is 4 inches,52 for a 180-pound individual, the gravitational force at the hip is as follows: Hip joint moment = (upper BW + lower leg weight) × lever arm Assuming the weight of lower leg is one sixth of BW, the acting moment is as follows: = (2/3 BW + 1/6 BW) × lever arm = 5/6 BW × 4 = 150 × 4 = 600 lbs/in Often individuals with painful hip or abductor weakness may lean their upper bodies over the painful hip to reduce the pain or may display a Trendelenburg (abductor lurch) gait pattern.59
When the pelvis rotates and the trunk is laterally flexed toward the stance limb, the moment arm may reduce substantially with respect to the neutral trunk. If the lever arm decreases from 4 to 2 inches (Fig. 7b.7B), the hip joint moment proportionally reduces to half. In a series of three experiments, Neumann48 compared the electromyography activity of the hip abductor muscles in subjects with hip prostheses adopting different methods of walking while using canes and carrying external loads. Twenty-four subjects with unilateral hip prostheses carried loads weighing 5%, 10%, or 15% BW and held by either their contralateral or ipsilateral arms relative to their prosthetic hips. As shown in Figure 7b.8, it was assumed that during the midstance phase of walking, the hip abductor muscle generated a very large force proportional to the BW and varied with a relatively small moment arm. Neumann found that the use of a cane on the contralateral side and the ipsilateral load condition could reduce the muscle activities by 40% of baseline as compared with walking without a load or a cane.
Synergic movement and muscular coactivation The force produced by a given muscle with specific size and structure depends on the activation level, length, and speed of contraction. The interaction of these parameters and their influence on muscle force production has been discussed in most basic textbooks of skeletal muscle biomechanics and physiology. Generally, it is known that tension generated in a skeletal muscle is a function of its length and the magnitude of overlap between the actin and myosin filaments. As the load increases, the velocity at which a muscle shortens while undergoing maximal stimulation decreases. During physical activities involving the lower extremity, muscle length changes due to the synergy among the monoarticular and biarticular muscles of the hip and knee joints. During functional activities, often the biarticular muscles have antagonistic activities at one joint and agonistic activities at another.4 During stair climbing, for example, the rectus femoris acts as the knee agonist muscle by providing the knee extension moment and as the hip antagonist muscle by providing the hip flexion moment.4 At times a muscle is even antagonist in one plane and agonist in another. Except for the short head of the
Weight Moment Arm Weight Moment Arm
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Figure 7b.7 Normal pelvis and hip orientation during upright standing (A) and pelvis position during abductor lurch and Trendelenburg (B). (From Robertson DD, Britton CA, Latona CR, Armfield DR, Walker PS, Maloney WJ: Hip biomechanics: importance to functional imaging. Semin Musculoskelet Radiol 7:28-41, 2003.)
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flexors in a series of radiographs. He found that the hamstring moment arm is about 2.50 cm in 5- and 90-degree knee flexion, but it increases to 4.08 cm as the knee reaches 45 degrees. These findings suggest that besides the length-tension relationship, the hamstring lever arm compensates for the decrease of muscle length that occurs during knee flexion (Fig. 7b.9B).42 Two-joint muscles provide several advantages in the control of the musculoskeletal system during physical performance. First, biarticular muscles couple the motion of the two joints in that they cross and redistribute muscle torque, joint power, and mechanical energy throughout a limb. Second, the shortening velocity of biarticular muscles is less than that of monoarticular muscles. Therefore, a comprehensive biomechanical analysis of a physical task should include a careful analysis of co-contraction biarticular muscles and synergic activities among all joints in balancing internal and external forces.
Joint forces during daily living activities
Figure 7b.8 The mean of normalized electromyography produced by the hip abductor muscles during three walking conditions: walking with contralateral (CL) cane and ipsilateral (IL) load, with contralateral cane, and with ipsilateral load. Loads are 5%, 10%, and 15% BW. The hip abductor electromyogram is normalized to normal control walking conditions. (From Neumann DA: An electromyographic study of the hip abductor muscles as subjects with a hip prosthesis walked with different methods of using a cane and carrying a load. Phys Ther 79:1163-1173, 1999.)
biceps femoris and the popliteus, all knee flexors are biarticular muscles, and their ability to produce force is influenced by the relative position of the two joints over which they cross. And except for the gastrocnemius, all muscles that cross posterior to the knee have the ability to flex and internally or externally rotate it. As a joint angle varies during physical activity, changes in the muscle length and in its effective moment arm at the joint result in torque variation.42 For the biarticular muscle of the hip and knee, it has been shown that change of angle at one joint and elongation of the muscle have been accompanied in most cases by greater torque production, an example being the effect of the hip angle on the knee extensor or flexor torque. Mohamed et al42 investigated the influence of length change on the electromyographic activity of six knee flexor muscles. As shown in Figure 7b.9A, regardless of the knee position, extended hip position was associated with significantly less torque than that of the other two flexed hip positions. Similarly, 90-degree knee flexion influenced the flexor muscle torque independent of the hip angle. Because the hamstring muscle length was shortened at both joints, the extended hip position and the 90-degree knee flexion resulted in the least torque production. The highest knee flexion torque was 90 degrees at the hip position and 45 degrees of knee flexion rather than extension. Similar results have been reported by other investigators that the peak torque occurred during the 45-degree knee flexion, where the flexor muscles were not fully stretched. In addition to the knee flexion torque, Smidt64 measured the lever arms of the knee
The muscular demand and internal forces on the joint and soft tissues during daily physical activities may provide valuable information about how they interact. Understanding the factors that may modulate the demand of these activities on the internal forces can be extremely valuable for assessing the effects of tasks that occur routinely at home and at work.
Squatting Dynamic squatting is an integral part of occupational27-29,68 and daily living activities, especially in non-Western cultures,22,44 and is the essential part of the strength and conditioning programs for rehabilitation and many sports that require high levels of strength and power.18 Half squatting, in which the posterior thighs are parallel to the ground with approximately 0-100 degrees of knee flexion, is more commonly discussed and recommended in the literature rather than deep squatting, in which the posterior thighs and legs make contact. Dynamic squatting is generally discussed in the context of the tibiofemoral and patellofemoral forces, the knee muscle activities, and the joint stability. Escamilla18 reviewed selected studies that have quantified the knee force during dynamic squatting. The posterior cruciate ligament restrains low to moderate posterior forces for all of the knee flexion angles throughout squatting. The anterior cruciate ligament restrains low forces from 0 to 60 degrees of knee flexion. During dynamic squatting, peak posterior cruciate ligament forces are estimated to range from 295 to 2704 N, peak anterior cruciate ligament forces from 28 to 500 N for 0 to 60 degrees of knee flexion, and peak compression from 550 to 7928 N. Because the ultimate failure load is reported to be 4000 N54 for the posterior cruciate ligament and from 1725 to 2160 N for the anterior cruciate ligament,53,74 dynamic squatting should not injure healthy joints.18 Although squatting and kneeling are common activities among many populations,22,27-29,44 only a limited number of studies have investigated the biomechanical consequences during such deep flexion activities.22 Hefzy et al22 used biplanar radiographs to evaluate knee kinematics in deep flexion and showed that the motion of the femur did not reveal rollback on the tibia beyond 135 degrees of flexion. Another kinematic study by Dyrby et al17
Chapter 7b
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Figure 7b.9 (A) The maximum isometric knee torque and electromyographic data collected during a series of nine combinations of the knee and hip position for 19 healthy subjects. (B) The maximum isometric knee flexion torque for three positions of the knee and two hip angles. (From Mohamed O, Perry J, Hislop H: Relationship between wire EMG activity, muscle length, and torque of the hamstrings. Clin Biomech 17:569-579, 2002.)
showed the relationship between deep knee flexion and internal/external rotation during deep squatting. Dahlkvist et al14 calculated joint and muscle forces from data collected from six subjects performing squatting and rising from a deep squat. Compared with the forces during normal walking,41,43 they estimated the tibiofemoral joint forces to vary from 4.7 to 5.6 times the BW vertically and 2.9 to 3.5 times the BW horizontally. Other investigators studied different styles of sitting and standing that require deep knee flexion. As shown in Figure 7b.10, deep flexion activities generate large quadriceps moments and net posterior forces depending on the style of ascension. The net moments and posterior forces increase along with the flexion angle. As Figure 7b.10 shows, net quadriceps muscle activity during double leg descending is about twice the single leg descending.
Fry et al20 studied knee joints under external load, the barbell squat technique, the restricted forward displacement of the knees past the toes versus non-restricted movement, and the knee position on the hip and knee torques. Seven weight-trained men were videotaped while performing parallel barbell squats with loads equal to their BWs. The study showed significant (p < 0.05) differences between the static knee and the hip torques, and the restricted squat produced more anterior lean of the trunk and shank and greater angles at the knees and ankles. The restricted squat produced knee torque of 117.3 (34.2) Nm and hip torque of 302 (71) Nm, whereas the unrestricted squat produced knee torque of 150 (50) Nm and hip torque of 28 (65.0) Nm. The squat technique and stabilization mechanism to balance the whole body can affect the large net quadriceps moments and
Reducing internal joint load: application of biomechanical concepts
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Chapter 7b
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Figure 7b.10 The mean and standard deviation of the net flexion moment (䊏), net posterior force (䊉), and net inferior force (䉱) during single-leg (A) and double-leg (B) descent for 9 women and 10 men with a mean age of 29 years (range, 21-37). Stick figures indicate the sagittal image of the limb during each motion. Net moments are normalized to the percent of body weight times the height (%BW × Ht), and net force is normalized to the percent of body weight (%BW). (From Nagura T, Dyrby CO, Alexander EJ, Andriacchi TP: Mechanical loads at the knee joint during deep flexion. J Orthop Res 20:881-886, 2002.)
net internal forces of the knee and hip joints. The loads on the knee during deep flexion are important for both knee pathogeneses and rehabilitation programs for patients with total knee arthroplasty. Although some squatting techniques such as restricting forward movement of the knees may minimize their stress, it is likely that such techniques may inappropriately transfer mechanical stress to the hips and low back.
Stair climbing and walking Like walking, stair climbing is a common daily activity that has been associated with a large number of cyclic joint loadings. If these activities are accompanied by pain and instability, they increase the perception of disability.13 Although stair climbing and walking are performed easily by healthy persons, they are quite demanding when joints or motor functions have been altered by disease or injury. Especially during their single support phase, adequate joint strength and control are critical to support the entire body mass and move the body forward. Despite the similarity between these two physical activities, adequate muscle strength and joint range of motion for level walking does not ensure the individual’s ability for stair climbing. The differences between these modes of locomotion might be significant for individuals with physical impairments. Compared with level walking, stair climbing requires 15 to 20 degrees more
knee and hip flexion.46 Bergmann et al8 reported the peak hip contact forces and torsional moments measured by instrumented implants during different common physical activities. The average hip joint load was 238% BW while walking 4 km/h, 251% BW while ascending stairs, and 260% BW while descending stairs. The most critical aspect of stair climbing is the inward torsion, which is 23% larger during ascent than walking. The number of parameters studied during stair climbing has been limited, in particular in the frontal plane. Nadeau et al46 studied and compared stair climbing and level walking during a preferred speed in healthy adults over 40 years old. The net moments and powers were estimated with an inverse dynamic approach. The researchers reported a significantly shorter stance time and longer mean cycle duration for stair climbing than for level walking. In comparison with level walking, greater flexion of the lower limb was observed at the beginning of the stair climbing cycle (foot strike) and less extension at the hip was observed at toe-off with concentric action of the abductor muscles that raise the pelvis on the contralateral side. Although the same muscle groups are used in stair climbing and walking, major differences were observed in the patterns of the knee flexors and extensors and the hip abductors and in the magnitude of the knee dorsiflexion during the swing phase. The moments and powers indicated a different action of the hip abductors across
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tasks to control the pelvis in the front plane of the stance phase and the knee extensors in the sagittal plane. Costigan et al13 examined hip and knee joint kinetics during stair climbing in 35 young healthy subjects using a subjectspecific knee model to estimate the bone-on-bone tibiofemoral and patellofemoral joint contact forces. Net knee forces were below one BW, whereas peak posterior-anterior contact forces were close to one BW. The peak distal-proximal contact force was on average three times BW and could be as high as six times BW. These contact forces occurred at a high degree of knee flexion, where there is a smaller joint contact area resulting in high stresses. The peak knee adduction moment was 0.42 (0.15) Nm/kg, whereas the flexion moment was 1.16 (0.24) Nm/kg. Similar peak moment values, but different curve profiles, were found for the hip. The hip and knee posterior-anterior shear forces and the knee flexion moment were higher during stair climbing than during level walking. The most striking difference between level walking and stair ascent was that the peak patellofemoral contact force was eight times higher during the latter. The patterns for normal stair gait show the dominant role of the knee during weight acceptance and pull-up, with the supporting
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roles played by the hip and ankle.40 The ankle has the major role during forward continuance, with relatively little contribution from the knee and hip. If the ankle is restricted, the higher forces are therefore transferred to the hip and knee.
Task variables In addition to the lever arm and magnitude of the external forces, various task variables are known to influence gait or movement pattern and thereby change the forces of the muscles and internal joints. Task variables can be classified into two categories. The first is those that are defined by the environment and cannot be individually controlled, such as stair height and angle of inclination and chair height, armrest,26,60 and surface condition.63 For example, Riener et al57 studied the influence of stair climbing with three inclination angles of 24, 30, and 42 degrees on the hip and knee joint biomechanics and motor coordination (Figure 7b.11). The joint angles and moments showed relatively small differences but depended significantly on the three inclination angles. The temporal gait cycle parameters and ground
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Figure 7b.11 (A) Joint moments during level walking and stair ascent and descent at minimum (±24 degrees), normal (±30 degrees), and maximum (±42 degrees) inclinations, averaged for 10 healthy subjects. Joint moments are normalized by body weight. The cycle starts with foot contact. The vertical bar indicates the toe-off, which divides the entire cycle into stance and swing phase. (B) Group mean and standard deviation for joint powers and joint moments for hip (䊉), knee (䊏), and ankle (䉱) during level walking (0-degree inclination), three-stair descent (at angles of −42, −30, and −24 degrees), and three-stair ascent (at angles of 24, 30, and 42 degrees). The solid lines show linear regressions. (From Riener R, Rabuffetti M, Frigo C: Stair ascent and descent at different inclinations. Gait Posture 15:32-44, 2002.)
Chapter 7b
reactions were not significantly affected, but joint powers were significantly influenced by stair inclination. The maximum joint powers in the hip and ankle change up to 67% with the inclination and can be attributed to the amount of potential energy produced during ascent or absorbed during descent by the muscles. The kinematics and kinetics of staircase walking differ considerably from those of level walking. A review of the literature indicated that a chair seat’s height, the use of armrests, and foot position have major influences on the sit-to-stand ability and the kinematics and kinetics of the lower extremity joints. Using a higher chair seat results in significantly lower moments at the knee (up to 60%) and hip (up to 50%) joints, whereas lowering the seat height makes sit-to-stand movement more demanding or even occasionally impossible.26 Reducing the seat height can alter the body’s stabilizing strategy and biomechanical profile, such as the increase in its center of mass travel distance and momentum needed to initiate the movement and the range of motion of the ankle, trunk, and knee.26 Conversely, maximum knee flexion moments were found to be highly dependent on chair height and nearly doubled from the lowest to the highest position from 6 BW at 115% of knee height to 3 BW at 65% of knee height.60 As shown in Figure 7b.12, moreover, a more posterior foot position allows both a lower maximum mean extension moment, 32.7 Nm at posterior versus 148.8 Nm at anterior, and a shorter movement time.32 Additionally, the use of the armrests reduces the moments needed at the knee and by 50% those needed at the hip. A chair with
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Conclusion
adequate height, sufficient space underneath, and armrests should therefore be recommended for patients with prosthetic devices,60 as well as for individuals with painful joints and low hip and knee strength. The second category of task variables consists of those that individuals may be able to control such as shoes, speed of movement, and style of movement gait. Peak force is sensitive to walking speed.69 Bergmann et al8 studied the influence of footwear and walking or running style. One subject with an instrumented hip implant wore different sports shoes, normal leather shoes, hiking boots, and clogs and walked barefoot with soft normal and hard heel strikes. The loads were the lowest while walking and jogging without shoes. The torsional loads rose up to 50% with shoes, whereas the hip bending moment at the implant slightly changed. The investigators concluded that soft heel strikes with smooth gait patterns are the only means to reduce joint loading. Soft heels, soles, or insoles did not offer advantages, and no relationship was found among different types of shoes. Shoes with very hard soles, however, increased the joint load and were clearly disadvantageous.
CONCLUSION Physical activities of daily living such as walking, running, and stair climbing involve cyclic activities coordinated among several joints. Kinetic and kinematic analyses of the hip and knee therefore
Figure 7b.12 The pathways of the center of gravity (COG) in a sagittal plane during two methods of foot placement in the initial stage of standing up from a chair (height, 40 cm). In the first method, with anterior foot placement, the COG moves forward and then up with the knee joint extension. In the second method, with posterior foot placement, the COG moves up from the early stage after lift-off with the hip joint and trunk extension. The initial position of the COG is defined as 0. The positive values correspond to forward and up. T1 indicates the beginning and T3 the end of the movement, whereas T2 indicates the beginning of different joint extensions. (From Kawagoe S, Tajima N, Chosa E: Biomechanical analysis of effects of foot placement with varying chair height on the motion of standing up. J Orthop Sci 5:124-133, 2000.)
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require an understanding of joint activities in relation to the whole body in the context of external loads and adapted posture. Kinematic and kinetic analyses of the hip and knee joints enhance our understanding of factors influencing external and internal forces and injury risks. Additionally, biomechanical concepts and simple biomechanical models provide reasonable estimates of factors differing among individuals, physical activities being undertaken, and task variables. A careful analysis of these factors provides a practical method of reducing musculoskeletal loads by altering external loads or modifying techniques for executing physical daily activities, thereby reducing risk of injury.
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63. 64. 65.
Reikeras OF, Bjerkreim IF, Kolbenstvedt A: Anteversion of the acetabulum and femoral neck in normals and in patients with osteoarthritis of the hip. Acta Orthop Scand 54:18-23, 1983. Reinbolt JA, Schutte JF, Fregly BJ, et al: Determination of patient-specific multi-joint kinematic models through two-level optimization. J Biomech 38:621-626, 2005. Riener R, Rabuffetti M, Frigo C: Stair ascent and descent at different inclinations. Gait Posture 15:32-44, 2002. Riley PO, DellaCroce U, Kerrigan DC: Effect of age on lower extremity joint moment contributions to gait speed. Gait Posture 14:264-270, 2001. Robertson DD, Britton CA, Latona CR, Armfield DR, Walker PS, Maloney WJ: Hip biomechanics: importance to functional imaging. Semin Musculoskelet Radiol 7:28-41, 2003. Rodosky MW, Andriacchi TP, Andersson GB: The influence of chair height on lower limb mechanics during rising. J Orthop Res 7:266-271, 1989. Rowe PJ, Myles CM, Walker C, Nutton R: Knee joint kinematics in gait and other functional activities measured using flexible electrogoniometry: how much knee motion is sufficient for normal daily life? Gait Posture 12:143-155, 2000. Rydell NW: Forces acting on the femoral head-prosthesis. A study on strain gauge supplied prostheses in living persons. Acta Orthop Scand 37(Suppl):132, 1966. Simpson AH, Lamb S, Roberts PJ, Gardner TN, Evans JG: Does the type of flooring affect the risk of hip fracture? Age Ageing 33:242-246, 2004. Smidt GL: Biomechanical analysis of knee flexion and extension. J Biomech 6:79-92, 1972. Stansfield BW, Nicol AC, Paul JP, Kelly IG, Graichen F, Bergmann G: Direct comparison of calculated hip joint contact forces with those measured using instrumented
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implants: an evaluation of a three-dimensional mathematical model of the lower limb. J Biomech 36:929-936, 2003. Stauffer RN, Chao EY, Gyory AN: Biomechanical gait analysis of the diseased knee joint. Clin Orthop Relat Res 126:246-255, 1997. Swanik CB, Lephart SM, Swanik KA, Stone DA, Fu FH: Neuromuscular dynamic restraint in women with anterior cruciate ligament injuries. Clin Orthop 425:189-199, 2004. Tanaka S, Lee ST, Halperin WE, Thun M, Smith AB: Reducing knee morbidity among carpetlayers. Am J Public Health 79:334-335, 1989. Taylor SJ, Walker PS: Forces and moments telemetered from two distal femoral replacements during various activities. J Biomech 34:839-848, 2001. Taylor WR, Heller MO, Bergmann G, Duda GN: Tibio-femoral loading during human gait and stair climbing. J Orthop Res 22:625-632, 2004. Thelen DG, Schultz AB, Alexander NB, Ashton-Miller JA: Effects of age on rapid ankle torque development. J Gerontol A Biol Sci Med Sci 51:M226-M232, 1996. Townsend MA, Shiavi R, Lainhart SP, Caylor J: Variability in synergy patterns of leg muscles during climbing, descending and level walking of highly-trained athletes and normal males. Electromyogr Clin Neurophysiol 18:69-80, 1978. Wang JW, Kuo KN, Andriacchi TP, Galante JO: The influence of walking mechanics and time on the results of proximal tibial osteotomy. J Bone Joint Surgery Am 72:905-909, 1990. Woo SL, Hollis JM, Adams DJ, Lyon RM, Takai S: Tensile properties of the human femur-anterior cruciate ligament-tibia complex. The effects of specimen age and orientation. Am J Sports Med 19:217-225, 1991. Yoshioka YF, Cooke TD: Femoral anteversion: assessment based on function axes. J Orthop Res 5:86-91, 1987.
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Clinical Evaluation of the Hip and Knee Craig J. Della Valle, Benjamin Crane, and Gunnar B. J. Andersson
A careful clinical evaluation of the hip and knee is important to determine the presence of disease or injury for the purpose of establishing the nature of a complaint. Only by means of an accurate diagnosis is it possible to determine an appropriate treatment. Given the importance of a thorough history and physical examination, textbooks are available that deal with this topic in great detail. It is beyond the scope of this chapter to provide a complete description of all the tests that are available to evaluate the hip and knee. Rather our goal is to provide the clinician with the basic skills needed to diagnose accurately and begin treatment appropriate for occupationally related complaints. Although advances in diagnostic imaging continue to improve our ability to identify anatomic abnormalities, these often do not correlate with clinical signs and symptoms. For this reason, indiscriminate ordering of advanced imaging studies is discouraged, particularly in patients with occupationally related complaints. In cases for which they are deemed necessary, plain radiographs can point the physician to a correct diagnosis of most complaints when these tests are combined with a thorough history and physical examination.
HISTORY Obtaining a medical history from a patient with an occupationally related complaint is somewhat different from doing so with a more general complaint: Occupational factors may provide additional information useful to obtain a correct diagnosis, and any relationship between the complaint and the patient’s vocation can have important legal, medical, and rehabilitative implications. The history should be structured, and the use of a “checklist” or standardized form is useful to ensure that all critical portions are carefully obtained and documented. An example of a structured history is shown in Table 7c.1. The history should begin by identifying the chief complaint and injury mechanism. All events should be carefully documented in chronological order. Although patients with hip pathology typically report pain in the groin, pain in the area of the greater trochanter or buttock is not uncommon. A history of difficulty in donning shoes suggests loss of hip range of motion and arthritis. In patients complaining of knee pain, it is important to document where the pain is located (anterior, posterior, medial, or lateral) and whether it is associated with swelling, sensations of instability (suggestive of a ligamentous injury), or mechanical symptoms such as locking or clicking that may point to a meniscal pathology or a loose body. Associated symptoms such as
numbness and tingling (characteristic of lumbar radiculopathy) that suggest alternative sites for pathology are also important to note. It is especially important to determine whether there are activities that exacerbate or improve the patient’s symptomatology to ascertain return to work status. Although past treatment of a particular problem is generally a crucial criterion for determining further treatment, in an occupational injury the complaint is typically referable to a triggering event (accident). It is important, however, to determine whether the present complaint is referable to a joint that has been symptomatic or injured in the past, because this may be a critical point in ascertaining whether the event in question caused an initial injury or aggravated a preexisting condition. Specific questions regarding childhood problems are particularly important in patients with complaints of hip and groin pain because developmental problems can become symptomatic later in life. Past medical history is important to ensure an appropriate evaluation (in a person with a history of malignancy, for example, metastatic disease can be considered among the potential diagnoses). The patient’s social history, including information about recreational habits, smoking, alcohol intake, and family life, are all important pieces of a thorough evaluation and paint a fuller picture of the person being examined.
PHYSICAL EXAMINATION Hip The physical examination of a patient with a complaint of hip pain begins with an observation of the gait pattern. The patient needs to be sufficiently undressed so that movements of the hip and knee can be observed appropriately. The two most common
Table 7c.1
Example of structured history
History of present illness What is the chief complaint (e.g., “left knee pain”)? When did the symptoms begin? How did they start? Was an accident or specific activity involved? What do you believe caused the symptoms? Why? Where exactly is the pain located (i.e., anterior knee, back of knee, inside of knee)? How would you describe your pain (i.e., throbbing, sharp, dull, tightness)? Are there activities that make your pain worse? What activities make your pain better? Do you have any associated symptoms such as stiffness, swelling, or weakness? What previous treatment have you had related to this complaint? Have radiographs or other tests been performed? Previous history of injury or problems with the affected joint Past medical history Occupational history Social history Review of systems
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gait patterns observed are an antalgic gait and a Trendelenburg or gluteus medius gait. An antalgic gait pattern results from the patient’s attempt to decrease weight bearing on the painful hip by decreasing the amount of time spent in stance phase on the affected side and thus the resulting pain. A Trendelenburg gait results from weakness of the hip abductor muscles (the luteus medius and minimus). In its normal state, the abductor musculature holds the pelvis level during the swing phase of gait; when the abductors are weakened, the pelvis drops on the side contralateral to the affected hip. The patient compensates by shifting the trunk in the opposite direction to maintain the center of gravity closer to the stance leg. The Trendelenburg test involves asking the patient to stand on one leg and then observing movements of the trunk and pelvis (Fig 7c.1). Normally, when the patient stands on the right leg, the gluteus medius on that side contracts to keep the pelvis level. If the muscle is weak or paralyzed, the pelvis on the contralateral side—the left side, for example—drops and the patient compensates by listing the trunk to the right. The test is typically recorded as positive (abnormal) or negative. It is positive most commonly in arthritic conditions, but patients with neurologic disease or with palsy of the superior gluteal nerve have similar, if not more dramatic, findings. With the patient still standing, the skin overlying the hip is inspected for abrasions, discoloration or ecchymosis, swelling, atrophy, or other deformity. The presence or absence of pelvic obliquity is determined next by identifying the anterior superior iliac spines, the iliac crest, and the greater trochanter; these structures should be symmetrically level bilaterally, and if not, pelvic obliquity is present. The patient is then placed supine on an examination table for a determination of leg lengths. A general assessment involves examining the relative positions of the soles of the feet and the medial malleoli. Keep in mind, however, that this measurement will not differentiate between a “true” leg length discrepancy and an apparent discrepancy that can be caused by pelvic obliquity or more commonly a hip flexion contracture. Actual leg length can be measured with a tape measure as the distance between the anterior superior iliac spine and the medial malleolus bilaterally (Fig. 7c.2). Apparent leg length discrepancy is measured from the umbilicus to the medial malleolus. The hip is next palpated to determine areas of tenderness. The greater trochanter can be tender after a fall on the affected side, but tenderness is more commonly associated with a trochanteric bursitis or insertional tendonitis. The femoral triangle anteriorly, the sciatic notch posteriorly, and the individual muscles around the hip should be palpated also to determine areas of maximal tenderness; these may represent a contusion or strain injury secondary to acute trauma or tendonitis or bursitis from less acute processes. The patient is then asked to “straight leg raise” or to lift the leg off the examination table with the knee extended. An inability to do so may indicate a femoral neck fracture, particularly in the setting of acute trauma, and thus plain radiographs should be obtained before proceeding further with the examination. The leg can also be passively elevated with the knee extended, and if shooting pain is experienced down the leg past the knee, particularly down the contralateral leg, a lumbar source of pain should be
Figure 7c.1 Trendelenburg test. The unaffected hip drops when standing on the affected leg.
sought (see Chapter 4c). Range of motion is then measured with the patient supine. A complete examination includes measurement of flexion, extension, internal rotation, external rotation, abduction, and adduction. To identify a hip flexion contracture, the Thomas test is performed: The contralateral hip is maximally flexed to eliminate the lumbar lordosis, and then residual flexion, if any, is measured (Fig. 7c.3). Normal range of hip flexion is 120 to 135 degrees (Fig. 7c.4). Internal and external rotation of the hip are measured next with the patient still supine and the knee flexed 90 degrees; normal ranges for internal rotation are 30 to 45 degrees and for external rotation, 45 to 60 degrees (Fig. 7c.5).
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Figure 7c.4
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Hip flexion is normally 120 to 135 degrees.
true hip range of motion (Fig. 7c.6). Normal ranges for hip abduction are 45 to 50 degrees and for hip adduction, 20 to 30 degrees. Hip extension is measured next and is most commonly performed with the patient prone; a normal range is 20 to 30 degrees (Fig. 7c.7). Muscular strength can be assessed next and should include direct testing of the hip flexors (iliopsoas and rectus femoris muscles), the hip extensors (gluteus maximus muscles), and the hip abductors and adductors. Hip flexion is tested most easily with the patient seated and asked to flex the hip against manual resistance; pain during this maneuver may indicate iliopsoas tendonitis. Hip extensor strength is most easily tested with the patient prone. Although the hip abductors have already been tested indirectly by gait observation and with the Trendelenburg test, with the patient in the lateral decubitus position, direct muscle strength testing can be performed. Pain with resisted
Figure 7c.2 Leg length should be measured from the anterior superior iliac spine to the medial malleolus.
Intraarticular conditions of the hip cause pain with rotatory movements, and a loss of internal rotation in particular is an early indicator of hip disease. Abduction and adduction are measured next while keeping one hand on the patient’s pelvis during testing to ensure that pelvic motion is not confused for
45°
35° 0° Figure 7c.3 The Thomas test is used to detect flexion contractures of the hip and to evaluate the range of hip flexion.
Figure 7c.5 Rotation tested in the flexed position is normally 30 to 45 degrees internal and 45 to 60 degrees external.
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A Figure 7c.6
B (A) Abduction and (B) adduction. Abduction is normally 45 to 50 degrees, and adduction is normally 20 to 30 degrees.
hip abduction may be further evidence of a trochanteric bursitis. Hip adduction is tested most easily with the patient supine and asked to adduct the hip actively from an abducted position. Although not directly related to the hip, a brief neurologic examination of the lower extremities is imperative to ensure that lumbar radiculopathy is not present; this should include a test of deep tendon reflexes and a motor and gross sensory examination.
Knee
with hip pathology can present with pain that is primarily referred to the knee. While the patient is still standing, examine the overall alignment of the extremity (Fig. 7c.8). Normally, the lower extremity is in slight (4-6 degrees) valgus alignment with larger amounts of varus or valgus typically associated with longer term pathology, such as arthritic conditions. Although unusual, muscular wasting should be sought, typically in association with neurologic pathology or disuse. Subtle muscular atrophy indicative of more chronic pathology can be ascertained with a tape measure placed around the thigh at symmetric points on the affected and unaffected limbs (e.g., at a specific distance as
The physical examination of the knee follows closely the form seen for that of the hip. As previously discussed, the patient must be sufficiently undressed to view the lower extremity in its entirety. Gait is typically examined first. Although an antalgic gait (decreased stance phase on the affected side to decrease pain) is most common, the presence of a Trendelenburg gait (indicative of hip pathology) is critical to identify because patients
30°
0°
Normal Figure 7c.7
Hip extension is normally 20 to 30 degrees.
Figure 7c.8
Valgus
Varus/valgus deformity of the knee.
Varus
Chapter 7c
measured from the medial joint line). Long-standing subjective complaints of knee pain without substantial (more than 5 mm) side-to-side difference in girth should be viewed skeptically by the examiner. In the setting of an acute accident, the skin is carefully inspected for abrasions, ecchymosis, or swelling. The patient can then be placed supine and the knee examined for an effusion or generalized knee swelling (Fig. 7c.9). In the setting of an acute injury, a very large effusion may indicate an intraarticular fracture, a ligamentous disruption, or an acute meniscal tear. With a more long-standing history of knee pain, an effusion can suggest arthritis or a meniscal tear. More localized areas of swelling can occur anteriorly (directly over the patella), indicating a prepatellar bursitis that can be associated with long periods of kneeling. Some patients (particularly males) may have an area of apparent swelling anterior to the tibial tubercle, just distal to the insertion of the patellar tendon. When palpated, this area is hard and represents bony overgrowth secondary to OsgoodSchlatter disease, a self-limited process that is rarely problematic other than for a cosmetic protuberance in the area. A localized area of swelling in the posterior aspect of the knee suggests a “Baker’s cyst.” Typically not the result of a primary process, a Baker’s cyst is secondary to arthritis or a meniscal tear, which induces an effusion that expands in the direction of least resistance. Because many of the important anatomic structures about the knee are subcutaneous, careful palpation can often identify the site of pathology. Tenderness directly over the patella can indicate either a contusion or a fracture if the patient sustained a fall or a direct blow to the area; alternative causes of pain here include prepatellar bursitis, as previously noted. Tenderness proximal to the patella most commonly represents tendonitis of the quadriceps or strain of the quadriceps muscle. If a frank tendon rupture is present, the examiner will clearly feel a palpable defect (Fig. 7c.10), and in most cases, the patient is unable to extend the knee actively or lift the leg with it extended. Tenderness distal to the patella can indicate chronic tendonitis (“Jumper’s knee”) or an acute tear if a palpable defect is noted and the patient is unable to extend the knee actively.
Figure 7c.9
Swollen right knee (typical appearance of an effusion).
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Figure 7c.10 Palpable defect in the quadriceps tendon, just proximal to the patella, indicative of a quadriceps tendon rupture; the patient was unable to extend the knee actively, and surgical repair was required.
The patella itself can also be examined to determine its mobility by gently moving it from side to side with the knee extended; normally, the patella should be mobile in extension and fixed in flexion. Whether this maneuver is painful or not and whether crepitation is sensed should be carefully noted because these symptoms may indicate arthritis of the patellofemoral articulation or patellar instability. The examiner should not be able to dislocate the patella completely from within the trochlear groove. Some patients may experience substantial apprehension during these translational maneuvers, perhaps indicating patellar instability; in the setting of acute trauma, tenderness along the medial border of the patella may be secondary to its dislocation. Generalized pain with patellofemoral compression may indicate arthritis or early degenerative changes of the cartilage of the patellofemoral articulation. If the examiner suspects patellar instability, the “Q” angle can be assessed also by determining the angle tendered between a line drawn from the anterior superior iliac spine and the quadriceps tendon and a second line drawn across the tibial tubercle and the central axis of the patella. Calculated with the knee extended and the patient supine, this value is expected to range from 15 to 20 degrees. Next, the joint lines are carefully palpated both medially and laterally; this is most easily accomplished with the patient supine and the knee flexed approximately 90 degrees. Localized tenderness along the joint lines may indicate meniscal pathology
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10° 0°
130° 90° Figure 7c.11 Flexion-extension of the knee: normal extension, 10 degrees; flexion, 135 to 150 degrees.
Figure 7c.12 the knee.
or arthritis. The collateral ligaments can also be palpated directly; tenderness and localized swelling along the medial or lateral collateral ligament (including the fibular head where the lateral collateral ligament inserts) can indicate acute rupture or strain. Range of motion is measured as flexion and extension with normal values 0 to approximately 135 degrees. Here 0 degrees is described as “full extension,” and values of less than that are referred to as a “flexion contracture” that is typically associated with knee arthritis or other long-standing pathology (Fig. 7c.11). Inability to extend the knee actively can indicate a disruption of the extensor mechanism (rupture of the quadriceps or patellar tendon or fracture of the patella) and is referred to as an “extensor lag” (Fig. 7c.12). Hyperextension of the knee rarely exceeds 10 or 20 degrees and, if asymmetric, may represent cruciate ligament injury or, rarely, neurologic disease. Although uncommon,
some patients may present with a “locked knee” wherein the leg is held in mid-flexion and cannot be flexed or extended; most commonly involving a large meniscal tear or a loose body that has become incarcerated in the joint, this symptom is associated often with acute severe pain and muscular guarding. Various special tests have been developed in an effort to identify meniscal pathology: A history of acute injury with an effusion and joint line tenderness or a subacute history of localized joint line pain, recurrent effusions, and mechanical symptoms such as locking suggest it as a cause. Most tests that follow should not be performed in the setting of acute injury because they not only cause substantial pain but also are relatively nonspecific. The McMurray test is performed by rotating the tibia internally and externally while simultaneously flexing and extending the knee with the patient in the supine position (Fig. 7c.13).
A Figure 7c.13
Extensor lag is defined as an inability to actively extend
B McMurray test. The knee is first rotated in full extension (A) and then extended (B).
Chapter 7c
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Physical examination
B
Figure 7c.14 compression.
Apley test. With the patient prone, the knee is flexed and the foot internally and externally rotated (A) with distraction and (B) with
The examiner’s fingers are placed at the joint line during this maneuver, and a palpable sense of locking or clicking, particularly when combined with recreation of the patient’s symptoms, suggests a meniscal tear. Although similar, the Apley test is performed with the patient prone and the knee flexed 90 degrees (Fig. 7c.14). The foot is rotated internally and externally while the joint is distracted or compressed; the test is considered positive if pain is recreated, particularly while the joint is compressed. Knee joint stability is tested by various means. As noted above, in the setting of acute trauma these tests should typically be deferred because they can be very painful and muscular guarding secondary to pain compromises their sensitivity. Stability of the lateral and medial collateral ligaments is determined by applying a lateral or medial moment to the knee while it is flexed
A Figure 7c.15
approximately 20 degrees (Fig. 7c.15). Testing is performed in mid-flexion to avoid a false-negative result, as the geometry of the joint itself confers some stability when the knee is fully extended. If a sprain rather than a frank tear has occurred, the application of these types of forces causes substantial pain without the examiner sensing frank instability. Testing the stability of the anterior cruciate ligament can involve either the anterior drawer test or the Lachman test. An anterior draw test is performed with the knee in 90 degrees of flexion while an anterior force is placed on the tibia (Fig. 7c.16); in the setting of acute trauma this test is particularly susceptible to a false-negative result because secondary restraints can compensate for a torn anterior cruciate ligament. Reputed to have higher sensitivity, the Lachman test is performed similarly, but the knee is held in approximately 30 degrees of flexion.
B Lateral stability is tested with the knee in approximately 15 to 20 degrees of flexion (A, medial; B, lateral).
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Figure 7c.16
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Anterior drawer test to detect cruciate ligament injury.
Specifically, the examiner holds the femur in one hand while applying an anterior force to the tibia with the other. In both tests, the examiner notes how far forward the tibia moves on the femur and whether or not there is a firm “endpoint” when such forces are applied. A final test to determine anterior cruciate ligament competency is the “pivot-shift” test; particularly uncomfortable for patients (and thus subject to false-negative results secondary to patient guarding), this test is probably most useful when performed in the anesthetized patient preoperatively. Place the patient supine and flex the knee approximately 30 degrees. Internally rotate the foot and apply a valgus force on the extremity by the placing the opposite hand on the tibia. The knee is then extended, and if the anterior cruciate ligament is ruptured, a palpable subluxation of the joint may be felt as the tibia jumps forward on the femur. Posterior cruciate ligament stability is tested using the posterior drawer test. Quite similar to the anterior drawer test, this test includes placing a posteriorly directed force on the tibia with the knee flexed 90 degrees while the patient is supine; a firm endpoint should be felt.
IMAGING DIAGNOSIS Hip Radiographic examination of the hip should include at least an anteroposterior (AP) view of the hip and pelvis and a lateral view of the hip. Oblique or Judet views may be useful when evaluating a patient with a suspected or known acetabular fracture, and pelvic inlet and outlet views are useful in patients with known or suspected pelvic fractures. Plain radiographs are the standard technique for evaluation of trauma and arthritis. Osteoarthritis is characterized by joint space narrowing (particularly in the superolateral or weight-bearing portion of the joint), subchondral sclerosis, and osteophyte formation; subchondral cysts may also be seen. In advanced cases, erosion of the femoral head or acetabulum can occur. In the earliest
stages of disease, weight-bearing views may be required to detect subtle joint space narrowing. Rheumatoid arthritis is characterized by a more symmetric pattern of joint space narrowing along with periarticular osteopenia; osteophytes are rarely seen until the later stages of the disease when secondary osteoarthritis develops. Seronegative arthritides (such as ankylosing spondylitis) usually present also with fusion of the sacroiliac joints, as seen on the pelvic AP view. Computed tomography is typically reserved for the evaluation of acetabular and pelvic fractures, but it may detect early degenerative changes. Three-dimensional reconstructions made from high-resolution computed tomographies can be used for better understanding of complex hip anatomy such as in hip dysplasia. Magnetic resonance imaging (MRI) is useful for identifying early osteonecrosis or avascular necrosis of the hip and occult fractures and stress fractures that are not visible on plain radiographs. In the patient with a history of trauma who complains of groin or hip pain and cannot raise the straight leg or ambulate, an MRI will most rapidly identify a nondisplaced fracture of the proximal femur. MR images can also detect loose bodies or pathology of the acetabular labrum; early degenerative changes also can be identified. Very sensitive but quite nonspecific, nuclear medicine studies such as bone scans are rarely useful, except for identifying metastatic disease. Although a bone scan also can identify subtle arthritis, joint inflammation, or occult fracture, MRI is superior in showing the specific pathology so that appropriate treatment can be instituted. In the case of occult fracture, whereas an MRI shows immediate changes, a bone scan may not be positive for several days.
Knee Routine radiographs of the knee include standing AP, lateral, and patellar (merchant or sunrise) views. Standing AP radiographs are recommended to assist in identifying subtle joint space narrowing and determining overall alignment (normally 7 degrees of valgus). Typically performed with the knee in 30 degrees of flexion, the lateral view is non–weight bearing. Additional views that may be helpful include a weight-bearing AP view with the knee flexed 45 to 60 degrees. Commonly referred to as a “skier’s view,” this radiograph often identifies more subtle joint space narrowing as the posterior aspect of the femoral condyle is imaged. Radiographic markers of osteoarthritis include joint space narrowing, subchondral sclerosis, and osteophyte formation. Radiographic changes may affect the medial tibiofemoral, lateral tibiofemoral, or patellofemoral compartments. The most common pattern is a varus deformity with the most severe radiographic changes affecting the medial compartment, although patients can develop a valgus deformity or have arthritis that affects predominantly the patellofemoral joint. Inflammatory arthritis generally causes a more symmetric pattern of joint space loss with periarticular osteopenia and often a valgus deformity. Plain radiographs can be reviewed not only for bony pathology such as arthritis or fracture but also for soft tissue pathology because symptoms such as a large effusion are often identifiable radiographically. Stippled calcifications seen in the area of the joint space may represent chondrocalcinosis or pseudo-gout.
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A high riding patella or “patella alta” may indicate rupture of the patellar tendon. MRI is used as a secondary test to identify pathology of the ligaments and menisci; more subtle damage to the cartilaginous surfaces can be recognized also as can processes such as osteonecrosis. Although bone scans are used occasionally to identify early degenerative changes when plain radiographs are negative, MRI is often both more sensitive and certainly more specific.
Similarly, arthroscopy of the hip is used occasionally in situations where subtle pathology of the labrum or cartilage is suspected that may be unrecognized with other tests. The greatest strength of arthroscopy is the ability to both diagnose and treat at the same time.
ARTHROSCOPY
Clinical evaluation of the hip and knee often allows the physician to make a diagnosis and plan for treatment. Imaging is sometimes a necessary complement but should always be evaluated in light of the clinical findings. Advanced imaging such as computed tomography and MRI are rarely necessary and should not be used for screening purposes, because the yield is low and false positive findings are not uncommon.
In the patient with persistent complaints of pain or instability in the face of plain radiographs and advanced imaging studies, arthroscopic examination of the knee can be used for diagnostic purposes to directly view its anatomic structures. Although tests such as MRI are quite sensitive, false-negative results can occur.
SUMMARY
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7d
Hip and Knee: Treatment Options James B. Talmage
Work-related problems in the lower limb are quite different from those in the upper limb. Physicians frequently see patients with occupational illnesses of the upper limb, where no major traumatic event has occurred, and the patient’s complaints are believed to be related to repetitively performing the same task(s). In the lower limb, these “overuse” disorders are distinctly uncommon. Sports medicine physicians see overuse hip and knee injuries, but these are very uncommon in workers’ compensation patients. The lower limb seems to be built with more reserve capacity for activity than is present in the upper limb. Thus, unlike when treating upper limb disorders, physicians rarely treat lower limb disorders and then have to ponder the wisdom of returning workers to jobs in which the repetitive performance of simple activities is alleged to have initiated the overuse illness. Most hip and knee problems that come to the attention of physicians are either gradually progressive age-appropriate degeneration (e.g., osteoarthritis), acute traumatic injuries (e.g., knee meniscal tear), or rheumatologic illness (e.g., acute gout or rheumatoid arthritis). Treatment of these hip and knee problems is the same for those patients in the workers’ compensation system (e.g., acute knee meniscal tear at work) as it is for those who have the same problem but are not in the workers’ compensation system. The results may not be as good. A recent meta-analysis showed that in 175 of 205 published studies, the results of surgical treatment of compensation patients were not as good as the results of treating the same condition with the same surgery in noncompensation patients.7 The pooled odds ratio for an unsatisfactory outcome in compensated patients compared with noncompensated patients was 3.79 (95% confidence interval, 3.28-4.37). Decisions on return to work require consideration of the nature of the condition. Acute injuries generally show progressive improvement with time and treatment, whereas progressive diseases like osteoarthritis and rheumatoid arthritis may show progressive deterioration requiring job modification or career changes.
THE HIP Hip problems in workers are uncommon and much less commonly seen than knee problems. For example, the American College of Occupational and Environmental Medicine’s Occupational Medicine Practice Guidelines, 2nd edition, contains a chapter on every part of the musculoskeletal system except for the hip. The material in the preceding chapter on diagnosis is not repeated, and the reader is referred to that chapter for details. A few of
the more common disorders affecting the hip are discussed in terms of treatment and work implications. Hip fractures are major acute injuries, generally from significant falls (Fig. 7d.1). Hip fractures are usually treated with surgical internal fixation or prosthetic replacement. For example, significantly displaced femoral neck fractures are frequently treated with prosthetic replacement of the proximal femur due to the high probability of the complication of avascular necrosis of the femoral head, whereas nondisplaced femoral neck fractures are usually treated with internal fixation for stabilization while the fracture heals. The orthopedic surgeon determines, based on the type of fracture and the type of surgery performed, when weight bearing on the affected limb is permissible. Until weight bearing is permitted, a worker can only do work in a sitting position. Ambulation at work would require crutches or a wheelchair and at least temporary access to handicapped parking. Periods of leg elevation may be required for prevention of thrombophlebitis. Workers with hip fractures may be using narcotic pain medication for several weeks or months. Company policies on work while using medications need to be considered. Hip arthritis may be a cause for hip pain with work activity (Fig. 7d.2). Osteoarthritis is much more common than knee arthritis. It increases in prevalence with age. Other than in farmers, epidemiologic studies have not associated hip osteoarthritis with work activity, so workers can continue to safely work despite osteoarthritis of the hip.17 The paradox of osteoarthritis in the lower limbs is those who get osteoarthritis of the hip do not usually get osteoarthritis of the knee, and those who get osteoarthritis in the knee do not usually get it in the hip; neither group gets osteoarthritis of the ankle, and yet each joint carries the same body the same number of steps. Simple overuse or “wear and tear” does not explain osteoarthritis. Ten to 20% of osteoarthritis patients present with arthritis in both the hips and the knees, but these patients also have multiple other joints involved (spine, shoulders, wrists, hands, and/or feet), suggesting a genetic disorder.7 Nonoperative treatment includes trials of nonsteroidal antiinflammatory drugs (NSAIDs) and a cane in the contralateral hand. No NSAID has proven to be superior, and physicians frequently prescribe several in serial trials, looking for the NSAID that gives the best relief and fewest side effects in the individual patient. The COX-2–specific NSAIDs have not been shown to provide better pain relief that the older traditional mixed COX-1 and COX-2 NSAIDs. The COX-2–specific drugs are suspected of having an association with myocardial infarction and stroke and are being prescribed less frequently. Weight reduction is frequently recommended on biomechanical principles but is rarely achieved. Dietary supplementation with glucosamine and chondroitin sulfate can be tried. These “nutraceuticals” are safe because they are compounds found in the human diet. They may decrease symptoms in osteoarthritis, although their onset of action is slow (several months). Whether they have a diseasemodifying affect is being debated.11,16 Glucosamine has not been shown to raise fasting blood glucose levels in diabetics. Severe hip pain is usually treated with total hip replacement. After hip replacement surgery, the surgeon determines when full weight bearing can occur. Cemented hip replacements are
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Figure 7d.1 (A) Plain radiographs of a 65-year-old woman who complained of severe pain after a fall. No evidence of fracture is seen on the initial film (arrow). (B) Magnetic resonance imaging of the pelvis. T1-weighted spin echo and (C) STIR images demonstrate focal bone marrow edema (arrows) in the femoral neck and a difference in intensity, indicating the presence of a nondisplaced femoral neck fracture. (D) Bone scan shows intense focal uptake at the site of the fracture (arrow). Intense diffuse uptake in the contralateral hip is due to osteoarthritis. STIR, short inversion time inversion recovery.
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Figure 7d.2 Severe osteoarthritis of the left hip with cystic changes in both the acetabulum and femoral head (arrow) in a 59-year-old school teacher. The contralateral hip was treated with a cementless total hip arthroplasty.
inherently stable, and full weight bearing can be permitted almost immediately. Noncemented hip replacements require time for bone to grow into the porous coating of the implant or for the patient to “heal to the implant” before full weight bearing can be permitted. After hip replacement, permanent restrictions against running, jumping, full squatting, kneeling, crawling, heavy lifting, and carrying are common to prevent loosening and dislocation of the prosthetic components. Avascular necrosis of the hip (osteonecrosis) is an uncommon problem (Fig. 7d.3). It may occur as a complication of femoral neck fracture or hip dislocation. It is seen without a history of trauma in patients with a history of systemic corticosteroid use, alcoholism, and as an idiopathic condition. In its early stages it is treated much like hip osteoarthritis with NSAIDs and a cane or crutches. If femoral head collapse has not yet occurred when the condition is recognized, non–weight-bearing ambulation with crutches may be recommended. In these early cases, bone grafting surgery is frequently tried. Late cases with femoral head collapse and severe pain are treated with hip replacement. Trochanteric bursitis is the most common bursitis about the hip. This is painful but not serious, because no significant consequences result from continued activity despite pain. Nonoperative treatments include NSAIDs, stretching, and strengthening exercises frequently initially under the supervision of a physical therapist. For refractory cases a corticosteroid injection into the region of the bursa may be helpful. Surgery is rarely indicated. A temporary period of reduced work activity may be useful, but it should not exceed 6 weeks. Hip “sprains and strains” are uncommon in the workplace. They must be differentiated from inguinal and femoral hernias. They usually result from significant falls, because few jobs include running or jumping activities likely to cause a hip strain or sprain. Heavy lifting rarely injures anything about the hip. Most sprains and strains recover in 6 weeks or less. Nonoperative treatment includes pain control and rehabilitation through stretching and strengthening exercises. Those that persist are usually evaluated by magnetic resonance imaging (MRI), looking for the unusual
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“bone bruise,” early avascular necrosis, transient osteoporosis of the hip, bursitis about a deep hip bursa (of which there are 13), or an acetabular labrum tear. Tears of the labrum do not always visualize on MRI, however, and hip arthroscopy may be necessary to exclude or to treat this diagnosis. For simple sprains and strains, a temporary period of reduced work activity may be helpful, but it should not exceed 6 weeks. Sprains and strains of the hip region, like those of other joint regions, heal in a known sequence. Muscles, ligaments, and tendons begin with an inflammatory phase of healing, progress to a synthesis phase, and finish with a remodeling phase. Although it may decrease pain, antiinflammatory medication does not speed up healing of muscles, ligaments, or tendons.6 Inflammation is a necessary part of tissue healing. “Muscle relaxants” are really centrally acting minor tranquilizers, and sedation accounts for their “muscle relaxation.” If a patient is not sleeping well, one dose a day at bedtime may improve his or her sleep pattern. Opioid analgesics, on occasion, are used for severe acute pain symptoms. Opioid analgesics act primarily by binding to opiate receptors in the central nervous system. They have potential problems of tolerance, dependence, addiction, and illicit use/diversion with long-term administration. Even short-term use of these medications should be undertaken with caution because potential problems with demotivation, early reactive hyperalgesia, and early dependency can occur in a select group of patients. Although more potent than NSAIDs and acetaminophen, in two of three clinical trials narcotic analgesics were not found to be more effective. The dosage schedule should be defined (not “PRN”) and use limited to patients whose pain is unresponsive to alternative medications.10 Physical agents including ultrasound, electrical stimulation, and heat and cold have been used to supposedly speed healing by increasing circulation and decreasing inflammation while reducing pain. These passive modalities do not appear to have any effect on clinical outcomes. No single modality has been shown to be superior to others for relief of musculoskeletal pain. Prolonged use of these passive modalities should be discouraged. Short-term use (1 to 3 weeks) of physical modalities may be appropriate for an acute musculoskeletal problem or a flare-up of a chronic condition, if they facilitate participation in active rehabilitative exercise.6
THE KNEE Acute knee injuries are common, although most are not work place injuries. Overuse syndromes about the knee are mainly a sports medicine problem and not a workers’ compensation problem. For example, the American College of Occupational and Environmental Medicine’s Occupational Medicine Practice Guidelines, 2d edition, discusses the treatment of many conditions affecting the knee, none of which is occupational overuse. Meniscal injuries are common (Fig. 7d.4). Small stable meniscal tears may produce only occasional tolerable symptoms with heavier activity. For these minor tears, patients may be content with intermittent use of NSAIDs and a home strengthening exercise program. A single intraarticular corticosteroid injection is sometimes given to decrease acute pain and effusion, hoping to permit earlier rehabilitative exercise. For patients
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Figure 7d.3 (A) Severe avascular necrosis of the femoral head in a 35-year-old alcohol abuser. Note the incongruity of the femoral head with collapse (arrow). (B) Frog-leg lateral demonstrates severe collapse of the superior portion of the femoral head (arrows). (C) Magnetic resonance imaging of the pelvis. T1-weighted and T2-weighted (D) spin-echo images demonstrate the extent of osteonecrosis in the femoral head.
with persisting major mechanical symptoms, arthroscopic partial meniscectomy is the now traditional treatment. For young patients with large peripheral tears (near the joint capsule where the meniscus still has a blood supply) that are discovered early, meniscal repair instead of meniscectomy is sometimes performed. If the meniscal tear is repaired, and if it heals, hopefully knee function will be normal, and the late posttraumatic arthritis that usually develops in knees after meniscectomy can be prevented. Long-term studies on this procedure are in progress. For the
young person without age-related osteoarthritis who sustains a large symptomatic meniscal tear, transplantation of a cadaveric meniscus is occasionally performed. More often this is performed in the young patient without significant arthritis change who remains symptomatic after total meniscectomy and who does not have significant knee deformity or instability.12 Patients with isolated meniscal injuries can almost always return to the job they were doing before the injury. Arthroscopic partial meniscectomy usually permits return to even heavy
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Figure 7d.4 (A) Magnetic resonance imaging (MRI) of a normal meniscus appears black (arrows) in a proton-density-weighted image, as it does in this case. (B) MRI of a torn meniscus. The posterior horn tear appears as a high-intensity white line or band (arrows).
work in 6 weeks (or at most 12 weeks).13 Patients with meniscal repair or meniscal transplantation require longer periods of activity restriction with emphasis on avoiding extreme flexion and twisting. Knee ligament injuries are sprains (Figs. 7d.5 and 7d.6). Isolated grade 1 and grade 2 sprains typically heal in 6 weeks and leave no sequela. Partial injuries to a cruciate ligament are sometimes treated with temporary protective bracing in addition to activity restriction to minimize the chance of reinjury. Complete
A
or grade 3 injuries to the medical collateral ligament are usually treated nonoperatively. Grade 3 injuries to the lateral collateral ligament may be treated with primary surgical repair. Grade 3 injuries to a cruciate ligament do not heal and are not amenable to primary repair. A period of rehabilitative exercise after injury permits a decision as to whether the residual symptoms can be tolerated with NSAIDs, quadriceps and hamstring strengthening exercise, and bracing. If not, reconstruction of the involved cruciate ligament is the surgical option.
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Figure 7d.5 (A) T2-weighted magnetic resonance imaging (MRI) of a normal anterior cruciate ligament (ACL) that has a low-intensity (black edge) straight anterior margin (arrows). The posteroinferior edge of a normal ACL is variable in appearance; it is high in intensity in this case. (B) T2-weighted MRI of a torn ACL. Tissue in the expected region of the ACL is high in signal and disorganized, indicating a tear. Note the frayed ends of the torn ligament (arrows).
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Figure 7d.6 (A) T2-weighted magnetic resonance imaging (MRI) of a normal posterior cruciate ligament (PCL) in a 25-year-old man. The ligament (arrows) is normally black, as it is in this case. (B) MRI, torn PCL. The bright appearance of the proximal end of the ligament and its discontinuity (arrows) indicates a tear at its attachment to the femur.
If residual instability is present, and especially if instability is present in two planes (both varus-valgus and anterior-posterior instability), posttraumatic arthritis generally develops at an accelerated rate. Bracing and permanent work activity restriction or a career change may be indicated if the patient usually performs heavy work. Osteoarthritis of the knee is very common. It increases in prevalence with age, and it is associated with family history, knee varus or valgus deformity, obesity, prior intraarticular fracture, and prior significant meniscus or ligamentous injury. At present, there are no conclusive data on the association of knee osteoarthritis and patients’ prior activity levels.3 Osteoarthritis of the knee is not a simple “wear and tear” problem. Nonoperative treatments1 of knee arthritis include NSAIDs, use of a cane, and usually weight reduction (again, frequently prescribed but rarely accomplished). Physical therapy consultation for training in quadriceps and hamstring strengthening may help significantly with symptoms, because the developing arthritis has frequently resulted in favoring the symptomatic knee and thus quadriceps and hamstring weakness from disuse.15 This exercise prescription does not result in further “wearing out” of the knee, because osteoarthritis is not a simple wear and tear problem. Unlike automobile tires, knees do not have a fixed number of miles they can travel. For patients with a significant knee varus deformity (bow legs), lateral wedge shoe insoles decrease the external varus moment and the estimated medial compartment load, resulting sometimes in pain improvement, especially in early stage arthritis. An unloader brace, which applies a varus or valgus moment to reduce force transmission in the most involved knee compartment (medial or lateral), can be tried in an active patient with isolated unicompartmental disease. Most patients discontinue brace use as the arthritis progresses. Work activity modification may be necessary as the arthritis progresses.
As in hip osteoarthritis, glucosamine and chondroitin may be tried, and some patients improve symptomatically.11 Acetaminophen (paracetamol in Europe) for many arthritis patients gives acceptable osteoarthritis pain relief with a better side effect or safety profile, and many reviewers recommend this drug be tried before NSAIDs are used.5,19,20 If symptoms are more severe, injection therapy is frequently used. Intraarticular corticosteroid injections may significantly decrease pain and effusion and may be repeated as often as every 3 months without documented worsening of the arthritis or other adverse effects.2,4 Intraarticular hyaluronic acid injection or “viscous supplementation” may also be tried. It is U.S. Food and Drug Administration approved as a series of three injections; however, it is much more expensive than simple corticosteroid injection, and its efficacy is controversial.8 As in hip osteoarthritis, when pain and disease become severe, surgical treatment is used. Arthroscopic debridement of the degenerative knee was performed in the past, although since the publication of a randomized controlled trial14 that showed no benefit over placebo arthroscopy, this surgery is rarely performed. Arthroscopy is still indicated for comorbid osteoarthritis and significant mechanical pathology, like a major meniscal tear or a loose body. For early varus deformity with medial compartment arthritis or for early valgus deformity with lateral compartment arthritis, if the other compartment is still relatively normal, a weighttransferring osteotomy of the proximal tibia is sometimes performed. Varus deformities are usually treated by lateral closing wedge osteotomy and valgus deformities by medial closing wedge osteotomy (Fig. 7d.7). The ideal patient for osteotomy has singlecompartment arthritis, ligamentous stability, and is “young” and physically active.13 Absolute contraindications include inflammatory arthritis, severe tricompartmental disease, a flexion arc of 90 degrees or less, marked tibiofemoral subluxation, and
Chapter 7d
Figure 7d.7 Bilateral varus deformities with medial joint arthritis in a 41-year-old woman treated with a high tibial osteotomy on the left side to correct her varus alignment.
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previous meniscectomy in the contralateral compartment. Relative contraindications include age older than 60 years, patellofemoral arthritis, collateral ligament insufficiency, lateral tibial subluxation, or a varus deformity more than 10 degrees. Once the osteotomy (“broken tibia”) has healed, activity restrictions may not be needed. Osteoarthritis is a progressive disease, so results deteriorate with time, and up to 40% of patients undergo knee replacement in 5 years and 50% in 10 years.9 For patients with severe arthritis and pain who are not candidates for osteotomy, unicompartmental knee replacement or total knee replacement are the surgical options (Figs. 7d.8 and 7d.9). Current knee replacement designs can be expected to last at least 15 years before wear requires revision.14 As in hip replacement, cemented knee replacements are immediately stable, whereas noncemented units require time for the patient to heal to the implant before full weight bearing is allowed. Rehabilitation after knee replacement is slower than after hip replacement. After successful replacement arthroplasty, the worker requires permanent restrictions prohibiting jumping, heavy lifting, and so forth. Knee tendonitis is an occasional problem, although again is much more frequently seen in a sports medicine practice than in an occupational medicine practice. It may involve the quadriceps
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Figure 7d.8 (A) A severe varus deformity in an 8-year-old girl with partial loss of the medial tibial plateau (arrow). (B) Total knee arthroplasty required a bone graft fixed with screws on the medial side to support the tibial plate (arrow).
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Figure 7d.9 (A) Bilateral degenerative joint disease in a 56-year-old woman rheumatoid patient. Note the complete loss of joint space, severe osteopenia, and lack of osteophytes typical of rheumatoid arthritis. (B) Bilateral total knee arthroplasties were cemented in place because of poor bone quality in this patient.
tendon, the patellar tendon, the iliotibial band, the popliteus tendon, or the medial hamstring tendon insertions (pes anserine bursitis). Treatment is usually symptomatic with a brief period of activity restriction, NSAIDs, and stretching and strengthening exercises. There is very little quality evidence on the role of physical therapy for knee tendinitis syndromes.1 For the patellar tendon, use of a “strap” orthosis may provide partial symptom relief. For refractory cases a corticosteroid injection may be used (but not for the quadriceps or patellar tendons because of the possibility of steroid induced tendon weakness predisposing to tendon rupture). In athletes, a shoe orthotic to alter knee mechanics is sometimes helpful. Surgery is used only for serious complications like complete rupture of a quadriceps or patellar tendon. “Patellofemoral pain” is a frequent complaint and is somewhat like chronic headache and chronic low back pain in that the findings in patients with anterior knee pain are usually nonspecific and commonly seen in asymptomatic individuals. Anterior knee pain in patients with obvious patellar malalignment or patellar instability (subluxations) can be rationally treated surgically, although with less than ideal results in many cases. Patients with anterior knee pain without obvious patellar malalignment or instability are challenging. In many patients the pain is attributed to chondromalacia of the patella, although arthroscopy studies have shown that the patella has normal cartilage in many of these cases.10 A patellar plica is a fold of synovium present in embryologic life that does not always resorb in childhood. In some adults it is postulated to be a cause of anterior knee pain. However, results from excising the plica arthroscopically are variable, and the persisting plica was not considered to be a source of symptoms when knee surgery was by open arthrotomy. Cynics believe that the plica is implicated
so that surgeons can charge more (therapeutic arthroscopy is reimbursed at a higher level than a “negative” diagnostic arthroscopy). Other than for obvious patellar malalignment or instability, the treatment for anterior nonspecific knee pain is usually nonoperative. NSAIDs are tried, although they may be ineffective. Physical modalities have not been proven to be effective treatment.1 Aerobic conditioning and quadriceps and hamstring stretching and strengthening exercises are usually tried. Closedchain knee extension strengthening exercises between 0 and 30 degrees of flexion put the least compression load on the patella and may be tolerated and thus performed. Surgical debridement (patellar chondroplasty) has variable to disappointing results. Like the patient with chronic low back pain, the patient with chronic anterior knee pain without objective findings is at times a problem in the workplace. There is no risk of serious consequences if the patient/worker remains active at work despite pain. The crucial issue is the patient’s tolerance for workplace symptoms, and in the absence of major objective findings, there is not usually physician agreement on the appropriateness of advising employers or patients to decrease the job demands on the patient.18
REFERENCES 1.
2. 3.
Archibeck MJ, Ayers DC, Berger RA, et al: Knee reconstruction. In KJ Koval, ed: Orthopaedic knowledge update 7. Rosemont, IL, 2002, American Academy of Orthopaedic Surgeons, pp. 513-536. Arroll B, Goodyear-Smith F: Corticosteroid injections of osteoarthritis of the knee: meta-analysis. BMJ 328:869-873, 2004. Clyman B: Sports, exercise, and arthritis. Bull Rheum Dis 50(6):1-3, 2001.
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4. 5. 6. 7. 8. 9. 10.
11. 12.
Cole BJ, Schumacher HR Jr: Injectable corticosteroids in modern practice. JAAOS 13(1):37-46, 2005. Courtney P, Doherty M: Key questions concerning paracetamol and NSAIDs for osteoarthritis. Ann Rheum Dis 61:767-773, 2002. Dahners LE, Mullins BH: Effects of nonsteroidal anti-inflammatory drugs on bone formation and soft-tissue healing. JAAOS 12(3):139-143, 2004. Harris I, Mulford J, Solomon M, et al: Association between compensation status and outcome after surgery. JAMA 293:1644-1652, 2005. Lo GH, LaValley M, McAlindon T, et al: Intra-articular hyaluronic acid in treatment of knee osteoarthritis: a meta-analysis. JAMA 290(23):3115-3121, 2003. Lonner JH: Clinical crossroads: a 57 year-old man with osteoarthritis of the knee. JAMA 289(8):1014-1025, 2003. Mayer TG, Press J: Musculoskeletal rehabilitation. In AR Vaccaro, ed: Orthopaedic knowledge update 8. Rosemont, IL, 2005, American Academy of Orthopaedic Surgeons, pp. 655-660. McAlindon T: Glucosamine and chondroitin for osteoarthritis? Bull Rheum Dis 50(7):1-4, 2001. McCarty EC, Spindler KP, Bartz R: Knee and leg: soft-tissue trauma. In AR Vaccaro, ed: Orthopaedic knowledge update 8. Rosemont, IL, 2005, American Academy of Orthopaedic Surgeons, pp. 443-456.
13. 14. 15. 16.
17. 18.
19.
20.
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References
http://www.mdainternet.com/V5/mdaTopics.aspx. Accessed 05/28/05. Mosely JB, O’Malley K, Petersen NJ, et al: A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med 347(2):81-88, 2002. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitative interventions for knee pain. Phys Ther 81(10):1675-1700, 2001. Richy F, Bruyere O, Ethgen O, et al: Structural and symptomatic efficacy of glucosamine and chondroitin in knee osteoarthritis: a comprehensive meta-analysis. Arch Intern Med 163:1514-1522, 2003. Sherrer YS: Working with common rheumatologic disorders. In JB Talmage, JM Melhorn, eds. A physician’s guide to return to work. Chicago, 2005, AMA Press. Talmage JB, Melhorn JM: How to think about work ability and work restrictions: risk, capacity, and tolerance. In JB Talmage, JM Melhorn, eds. A physician’s guide to return to work. Chicago, 2005, AMA Press. Zhang W, Doherty M, Arden N, et al: EULAR evidence based recommendations for the management of hip osteoarthritis: report of a task force of the EULAR standing committee for international clinical studies including therapeutics (ESCISIT). Ann Rheum Dis 64(5):669-681, 2005. Zhang W, Jones A, Doherty M: Does paracetamol (acetaminophen) reduce the pain of osteoarthritis? A meta-analysis of randomized controlled trials. Ann Rheum Dis 63:901-907, 2004.
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Workplace-Related Lower Extremity Disorders: Workplace Adaptations with Case Studies Amit Bhattacharya, Daniel J. Habes, and James A. Dewees
MAGNITUDE OF THE PROBLEM Work-related lower extremity musculoskeletal disorders A significant amount of research has been performed in the area of cumulative trauma disorders of the upper extremity and low back pain of occupational origin.127 Although studies on this topic are important enough to warrant further investigation, it is becoming more important to address the need to evaluate the lower extremity cumulative trauma syndrome. According to the Bureau of Labor Statistics, there were 1.4 million injuries and illnesses in private industry that required days away from work in 2002. Of these, 488,000 (34%) were musculoskeletal disorders, defined as injuries or disorders of the muscles, nerves, tendons, joints, cartilage, and spinal disks. Twenty-one percent of these musculoskeletal disorders occurred in manufacturing and about 9% occurred in construction. The back accounts for the greatest number of occupational injuries and illnesses, but reports for the upper extremity (hand, finger, wrist) and lower extremity (knee, foot, toe) are comparable with each other for both total injuries and illnesses (Fig. 7e.1A) and for musculoskeletal disorders only (Fig. 7e.1B). Moreover, the severity of injuries and illnesses to the lower extremity exceeds that for both the upper extremity and back, trailing only that of the shoulder (Fig. 7e.1C). For the years 2000-2002 the median number of days away from work for back, upper extremity, lower extremity, and shoulder injuries and illnesses has averaged 6, 6, 8, and 12 days, respectively. According to 2002 Bureau of Labor Statistics data, the services industry, which includes health care and social assistance, accounted for more lower extremity musculoskeletal disorders with days away from work than any other broad industry category (11,092). Manufacturing (5759) and transportation and public utilities (5668) were next, with about half the number of lower extremity musculoskeletal disorders with days away from work as services but higher severity rates with median days away from work of 11 and 15 days, respectively. Construction, which was fifth on the list of industries having lost work-day lower extremity musculoskeletal disorders (4748), also experienced more severe cases than services, having a median number of days
lost of 15. Furthermore, in the construction industry, musculoskeletal disorders involving the knee resulted in a median of 29 lost work days, a severity higher for the knee than any of the industry groups having more total lower extremity musculoskeletal disorders. Despite these facts from the Bureau of Labor Statistics, scientific studies and journal articles found in the literature predominantly address the upper extremity. Entering the key words “upper extremity musculoskeletal disorders” and “lower extremity musculoskeletal disorders” into a popular search engine yields 877 and 20 hits, respectively. There is additional justification for this new emphasis area based on the following facts: The working population is aging, and because age-induced muscle strength impairment affects the lower extremity and the upper extremity, it stands to reason that tasks requiring repetitive and sustained use of lower limbs detrimentally affect this part of the body. In contrast to the upper extremity, the lower limbs are under sustained static and dynamic loading due to weight bearing. When a person is simply standing upright, the lower extremity joints (such as ankle, knee, and hip joints) experience sustained biomechanical loading. These loadings become significantly high and repetitive (2 to 20 times the body weight) during simple walking and running.16,43 With an aging musculoskeletal system, such high repetitive loading may detrimentally affect the health of the joints. Furthermore, with the aging process, it is well established that in the general population the incidence of musculoskeletal disorders such as osteoarthritic knee is very high. It is estimated that over 80% of people over the age of 55 have a clinically diagnosed osteoarthritic condition.64,138 In the aged population the joint complaints of the lower extremities are more frequent than that of the upper extremities.11 There is sufficient evidence in the literature4 that osteoarthritis causes more absenteeism than any other joint trauma. Therefore, a worker population chosen from such a sample is at a high risk of developing significant musculoskeletal disorders of the lower extremity. Keeping in mind the changing demographics of the aging work force and the fact that lower extremity injuries account for about 20% of all compensable injuries, it is rather important that we further study this particular cumulative trauma. In particular, because most of the industrial tasks require some amount of sustained standing, it places excessive loading on the already traumatized lower extremity joints due to aging. Furthermore, jobs requiring excessive kneeling and walking further traumatize the aging lower extremity joints. A review of the literature indicates that a variety of occupations that require excessive use of the lower extremities shows a high incidence of musculoskeletal disorders. For example, osteoarthritic/arthritic and other types of musculoskeletal conditions of the knee, ankle, and hip have been documented in carpet layers, ballet dancers, housemaids, miners, and construction workers.13,24,26,38,63,66,69,105,107,108,122 Similar findings of lower extremity trauma have been documented in people involved in professional athletics such as soccer, football, bicycling, and running.8,24,60,101 Coggon et al33 concluded that there is strong evidence for occupational osteoarthritis from prolonged kneeling and squatting but reported that obesity may be a factor in such workers. A study by Lindberg and Montgomery67 reported that
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Figure 7e.1 (A) Number of nonfatal occupational injuries and illnesses with days away from work for select parts of the body, years 2000-2002. (B) Number of musculoskeletal disorders (MSK) involving days away from work for selected body parts, years 2000-2002. (C) Percentage of nonfatal injuries and illnesses with days away from work exceeding 30 days for selected body parts, years 2000-2002.
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osteoarthritic knee conditions in 322 shipyard workers (average age, 66 years) were significantly related to long-term (30 years) exposure to heavy labor rather than age. An epidemiologic study106 of 342 chain saw operators and 277 rock drill operators indicated that these workers showed not only classic cases of vibration white finger disorders but symptoms of numbness and coldness in the legs as well. The workers with the most frequent symptom were older and had longer exposures to vibration. The results imply vibration-induced disturbance of circulation of the lower limbs. Earlier studies14,139 showed that whole body vibration can cause modification of the cardiovascular system relevant for the lower extremities. Such disorders do not occur suddenly; rather, it is the long-term insult by the externally applied forces that gives rise to microtrauma of the biologic issues in question. The human body undergoes microtrauma on a daily basis from performing routine tasks such as walking, running, and climbing stairs. For normal tissue, exposure to such a low level of force causes gradual replacement of microscopically injured tissues with new ones. However, when the activities become more stressful and repetitive and the loading envelope reaches a certain limit, the biologic system no longer is able to respond by regeneration, and the result is pathologic conditions. Furthermore, the onset of such pathologic response is highly dependent on the existing health status of the tissue. For example, with the aging process, the susceptibility of injury to tissues under loading to externally applied forces is high. Middle-aged or elderly workers who are exposed to repetitive loading of certain parts of their bodies may be highly susceptible to injury due to declining health status in their tissue properties and not being able to sustain the insult caused by the external loading.
Case study of carpet layers Lower extremity trauma in carpet installers The concept of microtrauma induced by repetitive loading as described above is used for analyzing the job of carpet layers in our laboratory. This section presents the approach involving ergonomic/ biomechanical principles to better understand, characterize, and monitor lower extremity trauma experienced by these workers and to provide some solutions to help minimize this trauma. There are occupations (such as carpet laying) where knee injury claims have been significantly higher than knee injury claims from all occupations. Morbidity data indicate that carpet installers experience more than 10 times the number of lower extremity disorders than expected, given the percentage of these workers in the United States.117 Although others such as tile setters, floor layers, drywall installers, cement and concrete finishers, and carpenters also use their lower extremities in the performance of their jobs by kneeling, the carpet layers’ exposure to mechanical loading to the knee is not limited to the task of kneeling. A comparison of knee disorders among essentially equal numbers of carpet and floor layers to painters indicated that the former group reported more knee pain, knee accidents, and treatment regimens for the knees than the latter group. Osteophytes of the patella were more common among the carpet and floor layers as measured by radiographic changes.55 Ultrasonography performed by these same authors found thickening of the prepatellar or superficial infrapatellar bursa in 49% of carpet installers versus 7% of house painters.54
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The carpet layers further heighten the trauma to their knees by impacting on a carpet stretching device called a “knee-kicker” at a rate of about 140 kicks per hour with impact peak forces averaging around 3000 N15 (Fig. 7e.2A). Similar research found that seven male carpet layers using a knee-kicker over 39 trials demonstrated peak forces of 2933 N.128 In general, the carpet installation task requires use of awkward body posture, high impact forces to the knees, high acceleration of lower legs, and repetition that is biomechanically demanding and, therefore, provides reasons for high risk of knee disorders (Fig. 7e.2, B to D). The epidemiologic data of high morbidity (107.8) among carpet layers compared with tile setters and general floor layers substantiate the fact that these workers are at a relatively high risk of developing lower extremity musculoskeletal disorders.117 According to the Industrial Commission of Ohio’s report,3 the percentage of carpet layers’ knee injury claims was about four times higher than knee injury claims filed by all other Ohio workers. In an epidemiologic/medical study of 112 carpet layers, 42 tilers and terrazzo setters, and 243 millwrights and bricklayers, Thun et al122 reported that carpet and floor layers have a high frequency of bursitis, needle aspiration of knee fluid, and skin infections compared with the other workers in the study. Their study also showed that the frequency of impacting on the knee-kicker was the only statistically significant predictor of bursitis. The act of kneeling was one of several descriptors of knee aspiration and skin infection of the knee. The above summary12,17-19,54,55,68,117,122,128 of existing research studies on carpet installers clearly indicates a serious knee morbidity problem exists among these workers. The data so far supports the fact that the knees of these workers are actually traumatized by their occupation, and the resulting cost of medical expenses, earning loss, and physical and psychologic suffering compels us to investigate further monitoring and prevention of such a disability of the lower extremity.
Biomechanical basis for clinical responses to the carpet installation task Most of the postures used during the carpet installation phase of the job of installing carpet pose unusual biomechanical demands on the musculoskeletal system. In our previous study with carpet layers,17 we were able to identify typical postures that produce either static or dynamic sustained loading on the lower extremities (in particular, the knee joint). In Figures 7e.2A and 7e.3, we present examples of typical body postures that produce sustained static biomechanical loading of the knee joint. Such kneeling postures are maintained about 75% of the work period. The arrows in Figure 7e.3 indicate the potential areas of pressure points due to distributed ground reaction forces acting at the interface of the ground and the body. Because of excessive knee flexion angles and direct ground pressure at the infrapatellar region associated with these postures, the infrapatellar bursa is susceptible to injuries. This conclusion agrees with the finding of investigators at the National Institute for Occupational Safety and Health (NIOSH) who reported more frequent infrapatellar bursitis than prepatellar bursitis in this work force.122 In Figure 7e.3D, a typical posture is shown which describes the dynamic act of knee-kicking with the suprapatellar region of the knee. In our previous study17 we found that most of the
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time (70%) workers were involved in carpet stretching tasks, using the knee-kicker to stretch the carpet. The knee-kicking motion required vigorous and quick extension and subsequent flexion of the knee joint as the carpet stretching tool was struck. Therefore, this movement of the leg and the direct impact on the kneekicker with the knee potentially exposes the bursae (fluid-filled sacs whose function is to reduce friction and distribute stress) located anterior and posterior to the patella to trauma (Fig. 7e.4). The epidemiologic/medical evaluation study on carpet layers by Thun et al122 concluded that only the use of the knee-kicker predicted the occurrence of bursitis and to some extent knee tapping (using a needle to withdraw fluid from the knee). Our biomechanical explanation presented above and shown in Figure 7e.4 supports the findings of Thun et al.122 In the case of carpet layers performing the carpet-stretching task (using a knee-kicker), it appears that the bursae located
posterior and anterior to the patella and the infrapatellar bursa are in direct contact with the quadriceps muscle and the patellar tendon, respectively. Under such a repetitive movement condition, the tendon moves repeatedly over the bursae, causing mechanical irritation that gives rise to inflammation, causing fluid to be released into the bursae. Fluid in the bursae produces swelling and tenderness. If the inflammation is intense, the overlying skin becomes red and feels hot when touched. Symptoms typical of inflammation include95 swelling caused by accumulation of fluid that may require knee tapping, redness and local rise of skin temperature caused by increased blood flow around the injured area, tenderness on touching the affected area, and impaired function. Early signs of superficial tissue damage due to sustained kneeling or impacting a knee-kicker may be indicated by skin redness caused by increased blood flow and therefore local rise of skin temperature. Therefore, one of the medical/physiologic
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Figure 7e.3 process.
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(A-D) Lower extremity locations of potential pressure points and/or vigorous impact force on body postures of the carpet installation
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parameters of measurement should be skin temperature distribution and the degree of skin redness that could be used as preclinical indicators of inflammation/bursitis. In comparison with frictional bursitis, the condition of hemobursa (bleeding into a bursa) may be produced in people whose activities require them to make repeated contact with a hard surface or object, such as those experienced by carpet layers. In the case of carpet layers, sheer impact force on the knee-kicker may be sufficient to injure the bursae located posterior and anterior (pre) to the patella. Blood within the bursae causes chemical irritation, and in severe cases it may clot, causing adhesion of connective tissue and loose bodies. At this stage, chronic inflammation is likely to set in. The presence of loose bodies causes a specific cracking and grating sound when the knee is flexed and extended. Chu et al32 showed that the presence of loose bodies can be quantified by noninvasively measuring and characterizing the “acoustic signature” using a special purpose (20 to 20,000 Hz) microphone (attached to a waveform analyzer) in an auscultation examination of the knee joint. Development of this kind of methodology is highly recommended for a future project because this technique may be sensitive enough to identify the preclinical signs of the existence of loose bodies as well as some degenerative knee joint disorders. In addition to the trauma to the bursae, Thun et al122 also reported the existence of arthritic conditions in the carpet layers. They did not specifically distinguish between osteoarthritis and
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rheumatoid arthritis. In the carpet layers’ case, biomechanics can be used to explain the existence of potential osteoarthritis. Previous investigators77,100 implied and showed that with increase of articular stresses and asymmetric loads beyond the capacity of resistance of bone and cartilage tissues, osteoarthritic lesions appear and develop. From our field study and biomechanical analysis of the impact data and the position of the knee during the impact phase of the kicking cycle, we see that the result of Rk (impact knee force on knee-kicker) and Rpf (patellofemoral force) (Fig. 7e.4) either (1) acts eccentrically at the articulating surface, creating uneven pressure distribution on the cartilage and therefore present conditions for developing osteoarthritis, or (2) acts laterally, resulting in eccentric squeezing of the patella against the femur that increases localized stress with bone osteophytes, destruction of cartilage, and narrowing of joint space. Either of the above two conditions in conjunction with the impacting nature of the load experienced by the carpet layers give sufficient biomechanical reasons to promote osteoarthritis of the knee. Whatever the nature of the underlying cause, it appears that there is a need to quantify the existence of knee osteoarthritis in carpet layers at a preclinical stage. To date, this type of degenerative disease (generally irreversible) can be identified only when the actual sclerotic lesions have appeared on the tibiofemoral joint surface. These lesions are visible on an x-ray film. In our laboratory we have further developed, refined, and validated a previously reported133 noninvasive method for quantifying preclinical biomechanical parameters of knee osteoarthritis.2,50,111 Briefly, this technique allows noninvasive quantification of stiffening (or damping) properties of subchondral bone in the osteoarthritic patients compared with normal subjects. Previous study101 has shown that stiffening of subchondral bone may be used as a preclinical indicator of knee osteoarthritis. The experimental protocol involves attaching single-axis accelerometers at the tibial tuberosity and femoral condyles of each subject for collecting heel-strike–induced acceleration waveforms. The rationale is that the stiffer subchondral bone of osteoarthritic patients produces high-frequency bone vibration compared with those produced by normal subjects. Because of decreased damping capacity of the subchondral bone, harmful forces due to external loads (either produced by the occupational task and/or natural heel strike events) damage the knee cartilage and eventually traumatize the tibiofemoral bony surfaces. Ultimately, the incoming forces continue to progress toward the hip, causing it to become the next target of trauma. The results from our previous and ongoing studies with clinically diagnosed osteoarthritic patients2,52,113 (Bhattacharya, Watts, and Waters, 2004, unpublished data) indicate that this technique can differentiate osteoarthritic acceleration patterns from those obtained from normal subjects. The purpose of this study52 was to describe the accelerometric technique used to estimate tibial damping properties among osteoarthritic subjects. Tibial tuberosity bone vibration was captured in 8 osteoarthritic patients and 10 normal subjects with a skin-mounted low-mass accelerometer described in the literature.7,25,130-132 The subject was asked to walk on a force plate. Trabecular damping was estimated assuming a single degree of freedom model in which the tibia and foot were considered together as a lumped mass and the trabecular behaves as a linear
Figure 7e.5 Tibial damping calculated by accelerometric technique. (From Huang S, Bhattacharya A: Chin J Med Biol Eng 13:255-264, 1993.)
spring and viscous damper.10,34 During a force plate event (patient steps across force plate), the single degree of freedom system responds to the transient force in accordance with the solution to the second-order differential equation. Using a frequency response function (transfer function between the force plate and the acceleration at the tibia), the solution to a differential equation, a trabecular-damping fraction (ratio, ζ), was obtained directly from a measured frequency response function using a technique adapted from Coleman34 and Bendat and Piersol.10 The results showed that the osteoarthritic subjects have higher resonant frequency and decreased damping (Fig. 7e.5) than the normal subjects. It implies that the subjects with osteoarthritis have a decreased shock-absorbing capacity in the tibia and stiffer bone compared with normal subjects. Therefore it is a worthwhile effort to investigate this technique for identifying preclinical signs of osteoarthritis in the carpet layers. Based on the above discussion and our previous studies, the following parameters should be measured as descriptors of mechanical loading of the knee joint in carpet layers: kneeling time, knee-kicking frequency, kneeling pressure/force, and kneekicking impact force. The above parameters can be used to define new indices of biomechanical loading of the knee joint for carpet layers. One such index, called the Cumulative Impact Loading Index, is described in our earlier publication.18 The corresponding clinical/physiologic response variables should include (1) location and size of inflammation region, (2) skin temperature distribution of the inflamed region, (3) degree of skin redness, (4) range of motion of knee joint, (5) acoustic identification of the existence of loose bodies, and (6) noninvasive preclinical quantification of an osteoarthritic condition.
Work-related lower extremity vascular problems Many occupations require long periods of standing, including workers in the manufacturing, service, and retail sectors. Epidemiologic studies have shown certain health outcomes to be associated with occupational prolonged standing, including
Chapter 7e
chronic venous insufficiency,41,57,58,125 varicose veins,1,56,114,126 low back pain,73,85,105 symptom-free venous reflux,61 hip osteoarthritis,37 leg and foot pain,105 varicose symptoms without varicose veins (hypotonic phlebopathy),5 venous disease,42 arthrosclerotic progression (as measured by ultrasound of carotid intima media thickness),56 and trunk varices.116 Abramson et al1 estimated the prevalence of varicose veins in the general population to be 10% in men and 29% in women. Krijnen et al57,58 found the prevalence of venous insufficiency in a population exposed to occupational standing to be 29%. Chronic venous insufficiency is often unrecognized in the occupational population because it is sometimes asymptomatic.58 Much more research is needed to investigate causes of venous insufficiency.41 Biomechanical studies have shown prolonged standing to be associated with increased plantar pressures81 and pain and increased leg internal fluid volume.57,58 Prolonged standing can cause lower leg and back discomfort.102 Magora75 reported a high incidence of lower back pain for workers standing more than 4 hours a day. In addition to lower back pain, supermarket workers such as checkout personnel have a high incidence of lower limb discomfort and pain.105 Leg discomfort and fatigue is also found in assembly and quality control inspection workers.103 Eighty-four percent of French female health care workers stand more than 4 hours a day, compared with 43% in the general population.39 German laundry workers stand 70-80% of their work time per day.39
Physiology/biomechanics of prolonged standing The upright posture poses a challenge for the human cardiovascular system. In the upright position about 70% of the total blood volume is below the heart level and three fourths of the blood volume is located in the compliant veins.104 With upright posture, the increased hydrostatic pressure causes marked distension of the veins, causing pooling of the blood as increased filtration of fluid from the capillaries remain in the interstitial space (extracellular fluid) of the legs instead of returning to the heart. In the upright position, the mean capillary pressure of a person of average height may increase by 80 mm Hg to a value of about 125 mm Hg. During sudden upright position, the hydrostatic column of the blood in the vein between foot level and the heart level is broken up by a series of one-way venous valves. However, as the standing time progresses, the blood continues to flow from the arteries into the lower extremity veins, causing the blood to pool and thereby forcing the valves to open, causing an uninterrupted hydrostatic column of blood to form between the foot vein and the right atrium. Under these conditions, about 600 ml of blood usually shifts from the central circulation to the veins in the lower legs.72 Up to 30 minutes of standing causes the following responses to take place. When humans stand upright, both central venous and arterial pulse pressures fall, causing an increase in venous muscle tone via innervation of the sympathetic vasoconstrictor nerves supplying the smooth muscles of the venous walls. The increase in venous muscle tone increases the stiffness of the vein walls, causing the pressure of the blood within the veins to rise; this increased venous pressure then drives the blood out of the vein toward the right heart.114 Once the standing task continues beyond 30 minutes, both the neural and humoral responses play significant roles. With prolonged standing, the
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stimuli to initiate neural/humoral responses are a decrease in central venous pressure, arterial pulse pressure, and arterial mean pressure. The neural/humoral responses are an increase in sympathetic activity, plasma norepinephrine, heart rate, vasoconstriction, and vasopressin or antidiuretic hormones.104 The release of antidiuretic hormones is modulated by the atrial mechanoreceptors that sense the shift in fluid volume to the lower leg as a decrease in fullness of the vascular system. This hormone has water and salt retention properties that may constitute an effective long-term adjustment to the upright posture. The mechanism behind muscle pain/discomfort due to prolonged standing is not well understood.52,113-115 Some human studies113-115 using thermodilution techniques (along with hematocrit, hemoglobin, lactic acid, and muscle biopsy) have shown that submaximal static muscle contraction (such as prolonged standing) causes an increase in muscle water content due to an increase in extracellular water (possibly affecting muscle membrane potential due to changes in potassium and sodium contents of the muscle as per Sjogaard et al113), and with maximal static contraction intracellular water increases. One reason for an increase in water in the muscle is because lactate formed during fatigue is transported into the t-tubules where it attracts water and causes t-tubule swelling and vacuolation.62 Bakke et al9 in a study on humans showed significant correlation between muscle edema (as measured by an increase in extracellular fluid retention by the muscle) and subjective pain/discomfort. Therefore, previous studies,28 in which external leg volume was measured before and after prolonged standing, showed no statistically significant correlations between leg discomfort and leg volume change. This insignificant relationship could be due to the fact that an increase in leg discomfort may not be linearly related to venous pooling, because with sustained standing, compensatory mechanisms may actually reduce the venous pooling temporarily.9,104
WORKPLACE ADAPTATION/ RECOMMENDATIONS Injury/disease prevention plan for jobs requiring use of knee: carpet layers’ tasks The development of an effective injury prevention program involves three phases: (1) identification and estimation of the level of the health hazard/injury for a specific job, (2) development of a hazard/injury monitoring program, and (3) control of the hazard. As far as the carpet layers study is concerned, the hazard has been identified and its potential risk determined. We, in our laboratory, and others developed techniques to estimate the level of biomechanical loading and estimation/ measurement of medical/physiologic variables of lower extremity trauma. For example, to monitor and quantify the level of external loading exposure to the knee joints during daily carpet installation activities, we designed and developed an “electronic kneeling meter” that can measure and record the number of kneelings, length of kneeling time, and number of kicks applied by a worker during a working day15,20,46 (Fig. 7e.6). These parameters are then used for calculating a cumulative loading parameter for the knee joint. This unit is a self-sustaining microcomputer
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system controlled by a microprocessor through a software program stored in a nonvolatile microprocessor chip. This device is worn as a knee pad on the infrapatellar and suprapatellar regions. The entire system is designed for portability, and the display and storage of kneeling parameters remains intact for at least 4 hours before the data need to be downloaded (on a laptop computer) and stored for future analysis. The use of this device allows quantification and characterization of the dose of external loading on knee joints associated with tasks requiring the use of the lower extremities. For the quantification and characterization of early medical/ physiologic effects of exposure to chronic low-level biomechanical loading of the knee, a microprocessor-based liquid crystal thermography technique was developed in our laboratory.46 The developed system, which is inexpensive and portable for field use, uses flexible sheets embedded with liquid crystals that have both thermal and fluid properties. These sheets are factory calibrated to produce different colors for known temperature ranges. The flexible liquid crystal sheets are cut to fit the surface of the suprapatellar and prepatellar regions of the knee joints. For the evaluation of the temperature profile of the knee regions exposed to knee-kicker impact and kneeling tasks, the subject is first seated in an air-conditioned room with his or her leg inside a glare-free box. Once the liquid crystal patch is placed on the knee joint (either suprapatellar region or the prepatellar region), the colors are allowed to change and finally stabilize. An individual thermographic sheet displays its full range of colors from brown (coldest) to blue (hottest) within a range of 3 or 4°C. These color changes are continuously recorded on tape with a video camera. The video data are analyzed off-line with the help of a TARGA-16 based video-digitization system with customdeveloped software that allows calculation of liquid crystal areas of equal temperature zones. The output of this software allows us to identify the “hot spot” regions of the knee joint of the subject. This technique has been evaluated on arthritic and rheumatic patients, and the results suggest that the technique is
accurate in detecting joint inflammation in the absence of visible impairment. This thermography system was tested at the site of a local hotel undergoing renovation.46 Two carpet-installer tradesmen volunteered to undergo a day of testing with the thermography sheets. Both were experienced workers with 10 and 11 years experience as carpet installers, respectively. Measurements were taken before work began, at mid-morning and mid-afternoon breaks, just before lunch, and at the end of the work day. Because the thermography sheets we used had a narrow temperature range and we did not know what temperatures to expect from the workers’ knees, we assembled a collection of thermography sheets that could detect temperatures from 22 to 42°C. The two tradesmen went about their typical work activities that included a mix of unloading rolls of carpet from the delivery truck, cutting carpet and pads to size, laying tack strip and molding, and stretching carpet. We assumed that the workers were spending about 75% of the work time on their knees as indicated by our previous study.18 The individual and combined results for the upper knee (suprapatellar) of the two workers over the course of the work day are presented in Figure 7e.7. Measurements were taken on both the prepatellar and suprapatellar regions of the knee, but only the suprapatellar are presented because this part of the knee, which makes contact with the knee-kicker, produced the most dramatic results. The highest knee temperature detected was 30.1°C. The percentage of total patch area for each temperature color was calculated by outlining each color with the computer mouse and using the customized computer program to calculate the total area for each color outlined. The results of this case study indicate that the use of contact thermography, in conjunction with the analytical methods described above, may be an effective and expedient means of obtaining quantitative measures of knee temperature patterns in response to work involving the knee. Although the increase in the size of the “hot spots” on the knees of the two volunteer carpet installers was steady and consistent over the course of the day, the exact cause of the inflammatory response cannot be ascertained from an analysis of thermographic records alone. Questions to be answered are whether or not the observed inflammatory response was due to the work that was performed that day or to an existing knee inflammation that the workers may have developed over the course of their careers. Other questions that are raised include whether or not recovery to the knees would occur overnight, and whether these workers would demonstrate similar patterns of knee temperature increases while performing other knee-intensive activities such as walking, stair climbing, or crouching with a bended knee. A larger more in-depth study is needed to address these issues. Nonetheless, we conclude the following from this study: 1. Knee temperatures appear to increase consistently as cumulative biomechanical loading increases. 2. Contact thermography is able to detect these changes. 3. The thermographic system we developed provides a feasible means of measuring knee temperature at the work site. Some of the techniques such as those described above are tested and validated, and others may require some refinement. What remains to be done is the development and validation of a
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dose-response curve in a long-term prospective study that would be appropriate for development of a trauma/injury monitoring program. The methods and device(s) described here set the framework within which a long-term prospective study can be developed in the future. It is through such prospective study that one can determine the dose-response characteristics of job-related lower extremity cumulative trauma caused by external loading. The biologic system is capable of tolerating short-term low levels of external loading with complete recovery. However, it is possible, after a certain amount of biomechanical insult to the knee region, that the biologic system will show early (preclinical) signs of tissue damage/trauma as manifested by the inflammatory process. Even before the inflammatory process sets in permanently, the workers may show an increasing level of discomfort of the knee joint region as the biomechanical loading increases due to daily exposure to kneeling and knee-kicking. In summary, it appears that the dose-response curve may have several dimensions, including cross-correlation among variables of biomechanical loading, knee joint discomfort rating, medical/ physiologic response, and incidence of permanent knee injury. Such a dose-response curve (once established with a large population) could be made available to the worker or trade groups, such as unions, to show its application regarding identifying their members’ state of risk by measuring certain cumulative biomechanical parameter(s) on a regular basis along with proper and periodic medical evaluation. The primary objective would be to avoid getting close to the “irreversible trauma zone” of the proposed dose-response curve shown in Figure 7e.8. This could
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Increase in cumulative biomechanical loading** Hypothetical relationship * Skin temperature distribution pattern captured by thermography ** Cumulative impact loading index, kneeling time, skin pressure distribution by kneeling meter
Figure 7e.8 Schematic of hypothetical association between cumulative biomechanical loading of the knee and the early symptoms of clinical/physiologic outcomes.
be possible by suggesting proper work practice procedures and work rotation (rotating workers from knee-kicking activity, which is more traumatic, to other tasks of the carpet installation job). We drafted a preliminary guideline for the development of a work practice guide.16 It is envisioned that with the availability of such a monitoring program, one can make significant improvement in arresting and minimizing the high morbidity ratio found among carpet layers. Some of the information that will be generated for carpet layers can be modified for use by other professions (tile setters, floor layers, etc.), and in other occupations where the kneeling posture is also common. In addition to the above-mentioned significance to worker health associated with the proposed development of a doseresponse curve, tool redesign is certainly another approach that needs to be explored to investigate methods to further reduce injury among carpet layers. A study conducted by Liu et al68 in which the knee-kicker pad was modeled as a viscoelastic solid, concluded that the typical pad does little to attenuate the impulse of the kick stroke. That is, the pad is effective in transmitting the force produced by the worker’s knee to the carpet being stretched but does little or nothing to cushion the blow to the worker’s knee. The authors concluded that different pad materials need to be developed that better absorb harmful force transmissions and distribute the forces more evenly to the knee and for a longer time. They believed that with future research such a material could be found that reduces the trauma to the worker’s knee while maintaining the sharp impulse applied to the carpet. In response to the research described above, NIOSH published an Alert entitled “Preventing Knee Injuries and Disorders in Carpet Layers.”83 The purpose of a NIOSH Alert is to inform workers and employers of a health hazard, solicit the public for assistance in preventing the described health hazard, and provide recommendations for injury prevention and control based on what is known at the time. In the Alert, NIOSH recommended the following: 1. Employers educate workers about the hazards of kneeling and using a knee-kicker. 2. Workers wear protective knee pads while working on hard floor surfaces. 3. Power stretchers should be used wherever possible. 4. Conduct research to develop carpet installation methods that further reduce the physical stress and trauma incurred by carpet layers. A power stretcher is a tool that looks like a typical knee-kicker but is anchored to the opposite wall by attaching a series of telescoping tubes to its end. Once the power stretcher is spanned across the width of the room, force is produced by pushing downward on a handle that uses the leverage obtained from the stationary wall. Power stretchers are effective and relieve the worker from impact forces to the knee but are not used as often as possible because they are expensive, require more setup time, often lack portability, and cannot be used in small spaces such as hallways and stairs. A new type of carpet stretcher mechanism has emerged that promises to remedy some of the inconveniences of the power stretcher while maintaining its ability to stretch carpet. Called the “stretcher adapter,” it is a short piece of tube attached to
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the end of the power stretcher head that receives its leverage by insertion of a sharp pin directly into the floor. The stretcher adapter puts a hole in the carpet, underlying pad, and floor and cannot be used when installing carpet over concrete, but it reduces the setup time for the power stretcher, is lightweight and inexpensive, and can be used in small spaces such as hallways and closets (http://mctltd.com/StretchAdapter.htm). The stretcher adapter also causes no structural damage as can occur when a power stretcher is anchored against a wall in the room being carpeted. Innovations like these are what is needed (provided such devices are properly evaluated and found satisfactory) to relieve the carpet installer from the hazardous insults to the knee that have long been associated with this industry. Communication with trainers and safety specialists at carpentry and floor laying unions indicate that there is more emphasis on safety and safe work practices now than ever before. Workers also have better personal protective equipment such as knee pads that protect the knee and lower leg (www.proknee.com), cushioned insoles for work shoes, and even cushioned antifatigue material that can be wrapped around any type of shoe (http://www.safetyseven.com/ergoflash.html). For carpet and floor installers there are improved tools that reduce fatigue and physical trauma to the lower extremity such as automatic scrapers for ripping up existing flooring, carpet stretchers that can be activated with a lever instead of the knee (www.kneeless.com), and double-headed mini–carpet stretchers that more easily and quickly align seams for carpet that is glued to the floor. Nail guns used by carpenters eliminate the fatigue of hammering and allow framing and trim work to be accomplished quickly and efficiently, which means less time spent in hazardous postures such as kneeling and squatting. The experts say that a worker who is not fatigued will more likely take the time to work smartly and safely. According to one source, the traditional carpet stretcher is still used, but sparingly. One of the main recommendations of the NIOSH carpet layer Alert83 was to more extensively use the power stretcher. At first this device was not commonly used by carpet installers because it was cumbersome to use, expensive, and time consuming to set up. Modern designs are lightweight and easy to set up, and attachments exist that eliminate the need to span the stretcher between opposite walls to stretch carpet (http://mctltd.com/StretchAdapter.htm). These improvements have made the power stretcher the tool of choice in most carpet installation jobs. It is widely believed that comparatively few injuries to the lower extremity for carpenters and floor layers may be due to under-reporting. Despite improvements in tools and installation methods, workers still place a priority on finishing jobs on time. Sometimes cutting corners and overworking their bodies is needed to achieve these goals. The bottom line is that more emphasis on safety and the availability of more safety and health information, such as the NIOSH carpet layer Alert, may have made a difference in the musculoskeletal health of building trade workers, but working smart and safe is a constant struggle that must continually be reinforced. Ultimately, surveys of workers in controlled studies must be conducted to determine the true extent of any changes in the hazards of this type of work and the manner in which workers cope with it.
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Antifatigue mats for jobs requiring prolonged standing To reduce body discomfort and fatigue, antifatigue mats have been used in many industries. Many researchers have investigated the relationships between subjective measures, such as selfreported body discomfort, while working on different surfaces (such as an antifatigue mat) and objective measures, such as electromyography recording on the lower legs and back,35,40,47,48,74,79,140 leg volume,28 movements of the ankle and center of pressure, and other biomechanical parameters.28,40,47,48,74 Because of the pull of gravity, prolonged standing may cause poor venous pump activity, which may cause leg edema and body discomfort.137 In addition, poor venous pump activity has been documented as a result of prolonged standing on poor resilient surfaces.23 The effects of various standing surfaces on venous pump activity were evaluated in some studies.21-23,102,103 The results have shown that antifatigue mats with increased elasticity/stiffness can increase venous pump activity of the legs and reduce body discomfort.28 However, the range of values of elasticity/stiffness and energy absorption of the floor mats, which are shown to be beneficial, have not been reported in the literature.
Impact of contaminants on antifatigue properties of floor mats In many working environments, such as automobile parts manufacturing plants or food processing facilities, antislip and/or antifatigue mats are often contaminated with water, oil, or other fluids. The effectiveness of the antislip properties of antislip and/or antifatigue mats with different contaminations and the reduction of body discomfort while performing a job task are not well documented in the literature. The effectiveness of the antislip property of mats is “qualified” by manufacturers as “good” slip resistance. This measure is not adequate for working environments because the slip resistance of the mat is related to the shoe worn by the worker and the task being performed.29-31 Furthermore, the presence of contaminants such as water and oil can modify an antifatigue mat’s mechanical properties, which have been reported to relieve postural fatigue due to prolonged standing.28 Cham and Redfern28 reported that floor mats with increased elasticity, decreased energy absorption, and increased stiffness are associated with lower levels of fatigue of the lower leg and the back area. However, repeated exposure to oil and/or water decreases the mat’s stiffness and elasticity, thereby compromising its antifatigue properties. Contaminants also reduce the antislip properties. Previous studies from our laboratory showed that postural stability is significantly compromised during dynamic and semidynamic task performance on slippery surfaces.27,28,30,31,71,135 Limited studies109 from our laboratory also showed that leg muscle workload associated with bicycling significantly (p < 0.007) impairs postural stability. Previous electromyographic studies51,80 have shown that pedaling activity uses predominately the same muscle groups (hamstrings, triceps surae, gluteus maximus, tibialis anterior, and quadriceps) that are needed to perform standing and walking activities. Seliga et al109 showed that postural sway length significantly increased with increasing workload from 40 to 125 watts, implying postural instability. Therefore, when postural muscles are overworked for maintaining
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upright balance on a slippery surface, it is reasonable to assume that with prolonged standing/walking on slippery surfaces, the postural muscles experience further fatigue and discomfort, causing potential postural instability and fall/near fall-related injuries. In a pilot study at an auto manufacturing plant, the effect of task performance on slippery surfaces (concrete and floor mats) on body part pain/discomfort and slips and their association with surface coefficient of friction was carried out by our research group.70 The results suggest that workers’ body pain or discomfort may be caused by the task characteristics or the combination of working on the slippery surface and the task characteristics. Under these circumstances, there is a need to modify the mat’s properties in such a way that it has a reduced rate of absorption of a contaminant such as cutting fluid/oil/coolant and an increased coefficient of friction value, while preserving the desired material properties associated with its antifatigue features. One such technique is to deposit plasma polymerized films onto the mats to vary the coefficient of friction and to control the uptake of cutting fluid/coolant/oil.118-121 The above literature review raises several questions regarding the floor mats used in industries where workers have to perform tasks during prolonged standing on mats contaminated with oil/ coolant/cutting fluid: How do contaminants modify the mechanical properties of the floor mats? Do contaminants detrimentally modify the antifatigue properties of the mats? Do antislip mats provide proper frictional properties as well as antifatigue properties?
Shoe inserts/insoles for jobs requiring prolonged walking Because walking and running give rise to heel strike–induced forces in the musculoskeletal system, the transmission, absorption, and attenuation of energy that intakes to the skeleton due to heel strike are an important component of bone physiology and pathology.44,84,98,134 The human locomotion system, which consists of natural shock absorbers (joints with viscoelastic components, articular cartilage, meniscus, intervertebral disks, trabecular bone, etc.), is subjected to constant insult not only during weight-lifting activities but also during normal daily activities such as walking and running.6,16,130,131 During heel strike, the vertical force component acting on the foot is on the order of 1.5 times the body weight depending on walking velocity.16,129 These force waves are gradually attenuated by the body’s natural shock absorbers on their way toward the head. The process of force wave attenuation is the body’s natural way of protecting the vital organ, the brain. In healthy subjects, 70% of the incoming shock waves are absorbed by the body’s natural shock absorbers before it reaches the forehead.7,16,44,130,133,134 Among all natural shock absorbers in the human body, the trabecular bone has the highest capacity (170 times higher than that provided by the cartilage) to attenuate incoming shock wave associated with heel strike during walking and running.96 Previous researchers have shown that such cumulative loading may give rise to gradual fracture of subchondral bone trabeculae, which through healing of the fracture actually renders the subchondral bone stiffer, thereby decreasing its shock-absorbing capacity.94,97,99,124
Such stiffening of subchondral bone has been found to be associated with osteoarthritis, one type of degenerative musculoskeletal disease.45,94,97 Based on the above discussion of the potential detrimental impact of heel strike–induced trauma of the knee joint, it is reasonable to use a shock-absorbing type of material in the lower extremities to dampen the incoming shock waves. The use of shoe inserts and insoles have been reported in the literature to help minimize pain and discomfort associated with degenerative disorders of the knee such as osteoarthritis. In our laboratory, a study110 with 24 subjects (normal and osteoarthritic patients) was carried out to determine the impact of shoe insert (pad) in reducing heel strike–induced acceleration measured at the tibial tuberosity. The results showed that a shoe insert or pad reduced the high-frequency heel strike force-induced shock waves over a larger frequency range as compared with that provided by the physiologic shock absorbers available in the human body when a shoe insert was not used. Specialized shoe orthotics have been evaluated to determine their effectiveness in minimizing osteoarthritis associated pain/discomfort.84 Kerrigan et al53 tested lateral-wedged (5 degrees) insoles and found them to be biomechanically effective in potentially reducing loading of the medial compartment in patients with knee osteoarthritis. In a study by Toda et al,123 two types of shoe inserts were evaluated. The effectiveness of a novel lateral wedge insole with elastic strapping was compared with that of a traditional shoe insert/insole in 90 female subjects with osteoarthritis of the knee in an 8-week study. The subjects wearing the novel lateral wedge insole with elastic strapping showed a significant improvement in their pain and decreased femorotibial angle and talar tilt (i.e., leading to valgus angulation of the talus). For the traditional patients wearing shoe inserts such improvements were not found. Although Kerrigan et al,53 Toda et al,123 and others36 reported some beneficial effects of the use of laterally wedged insoles, Maillefert et al76 did not show any pain relief from short-term (6 months) use of the shoe insert in medial femorotibial osteoarthritic patients. In addition to the use of shoe inserts, there is some evidence in the literature regarding the role of exercise programs for minimizing insult to the knee joint. Oddis84 recommended use of isometric muscle strengthening of the quadriceps, which may act as the shock absorber for the injured knee. Although studies of shoe inserts in osteoarthritic patients have been well documented in the literature, there are a lack of data regarding the use of this form of intervention in occupational populations. Finally, there is a need for research studies where shoe inserts and specialized exercise programs can be tested as preventive tools in workers exposed to activities requiring prolonged walking and standing.
A two-part case study from an industry in workplace accommodations for an acute knee injury and subsequent chronic pain, discomfort, and work restrictions Case study part 1: Prevention of recurrence of a knee injury that resulted from a fall while
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descending a staircase and carrying a 24-pound power tool The worker and task A right-handed 52-year-old man approximately five feet ten inches tall and weighing about 210 pounds worked as a maintenance and service technician for over 18 years for the same company. At the time of this writing, he was one of seven technicians performing roughly the same tasks. His job required frequent walking throughout the facility and occasionally ascending and descending staircases while carrying various tools and equipment that weighed from just a few pounds to nearly 40 pounds. He estimated that he typically climbed and descended staircases three to five times during each regular 8- to 10-hour shift. The nature of the business and potential safety hazards required him to wear steel-toed boots with metatarsal arch protection, a flame-resistant long-sleeved jacket, a hardhat, eye protection, and hearing protection. The facility where he worked was built in the early 1970s, and it had not changed significantly over the next 30 years, except for occasional cleaning, repairs, and minor alterations to the walking and working surfaces. Until the spring of 2001, this worker had no history of knee or lower extremity injuries or discomfort and could not recall experiencing any significant slips, trips, or falls during his 18 years of service. He reported to be “very familiar” with the facility and until the experience described below had not missed a day of work as a result of a work-related mishap. However, according to the company’s Occupational Safety and Health Administration (OSHA) 200 logs, there had been three other lost-time injuries to three separate workers resulting from slips, trips, and falls during the previous 3 years.
The accident and injury One afternoon in April 2001, the worker was returning to the tool crib after completing a job that required the use of a powered chipping hammer to break concrete. He reported carrying the tool, which weighed about 24 pounds, in his right hand and walking at a moderate pace. He decided to cross over a bridge that recently had been closed for repairs but had been reopened. He stated that he typically had crossed the bridge many times in the past but that his regular path over the bridge had been altered for about 3 days while repairs to the bridge were in progress. The bridge was constructed with seven metal steps up one side, a platform over and across some mechanical equipment below, and seven metal steps down the other side. The worker climbed up the first set of steps, crossed the platform, and while descending the other side, misjudged a step, lost his balance at about the third step from the bottom and fell to the floor, dropping the power tool and feeling a sharp burning pain in his right knee. After the fall, he stood up carefully and took a few steps toward the chipping hammer that had slid several feet across the floor, but he could not bear the pain so he sat down on one of the steps and then called and waited for assistance. An emergency medical examination that evening discovered a torn medial collateral ligament in his right knee that would require surgical repair and 3 to 4 weeks of lost work.
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Safety and ergonomic assessment Recall that the worker had no history of knee or lower extremity disorders and did not recall experiencing any significant slips, trips, or falls during his 18 years with the company. Also, he had become very familiar with the facility and until this accident had not missed work as a result of an on-the-job mishap. Therefore, the assessment of the safety hazards and ergonomic risk factors began with the design and construction of the staircase at the specific location of the accident according to the following criteria: 1. Standard conventional angle of stairway rise (slope), height of each step (riser), depth of each step (tread run), slip resistance of each tread and leading edge (nosing), and uniformity throughout the entire flight of stairs per: a. OSHA 29 CFR 1910.24 (e): Angle of stairway rise88 b. OSHA 29 CFR 1910.24 (f): Stair treads89 c. Lehmann65: Stairs of the following dimensions require the least energy consumption and “seem to cause the fewest accidents.”59 i. Slope of 25-30 degrees ii. Recommended formula: 2h + d = 630 mm (24.8 in); where h = height of riser and d = depth of tread d. Rapid Entire Body Assessment, REBA49
Assessment results OSHA 29 CFR 1910.24 (e)88 states that fixed stairs shall be installed at angles to the horizontal (slope) of between 30 and 50 degrees. The 43-degree slope of the staircase at the location of the accident was in compliance with the standard. Table 7e.1 from the OSHA standard88 shows “riser” and “tread run” combinations that when uniform throughout the entire flight of stairs, produce a stairway within the permissible range. The table also shows the slope (angle to horizontal) produced by each combination and that each step of a stairway having a 43-degree slope should have a “riser” of approximately 8-1/2 inches and a “tread run” of roughly 9 inches. OSHA 29 CFR 1910.24 (f) reemphasizes that the “risers” and “tread runs” shall be uniform throughout any flight of stairs.89 Each of the seven steps that were being descended by the worker at the time of the accident were measured as shown in Table 7e.1 (accuracy ± 1/8 inch) and numbered from the top step to the bottom. The measurements show that the bottom three steps had rise dimensions that did not comply with Table 7e.1 of the OSHA standard,88 and that the riser dimensions were not
Table 7e.1 Stairway riser and tread run in case study part 1 Step no.
Riser (in inches)
Tread run (in inches)
7 6 5 4 3 2 1
8-5/8 8-1/2 8-1/2 8-3/8 8-0 7-7/8 9-5/8
9-0 9-0 8-7/8 9-0 9-0 8-7/8 9-1/8
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uniform throughout the flight of stairs. Further investigation revealed that steps 2 and 3 had been repaired because they had become rusted and had partially broken loose from the metal frame. Steps 2 and 3 had been raised slightly and rewelded to the frame, which shortened their riser dimensions by 5/8 and 1/2 inch, respectively, consequently increasing the riser of step 1 by 1-1/8 inches. OSHA 29 CFR 1910.24 (f) states,89 “all treads shall be reasonably slip-resistant and the nosings shall be of non-slip finish. Welded bar grating treads without nosings are acceptable providing the leading edge can be readily identified by personnel descending the stairway and provided the tread is serrated or is of definite non-slip design.” The treads of the stairway at the accident location were welded bar grating without nosings, and their leading edges were not clearly identifiable. The tread was serrated and of nonslip design. According to Lehmann,65 a staircase slope of 25-30 degrees with uniform risers of 170 mm (roughly 6-5/8 inches) and tread runs of 290 mm (roughly 11-3/8 inches) requires the least energy consumption and seems “to cause the fewest accidents.” Lehmann’s recommendation for the most “efficient” riser and tread run dimensions can be expressed by the formula 2h + d = 630 mm (24.8 in) where h = height of riser and d = depth of tread. Steps 4 through 7 of the 43-degree-slope staircase where the accident occurred had relatively uniform risers (h) of an average 8-1/2 inches and tread runs (d) of roughly 9-0 inches. Although the 43-degree slope fell within range of the 30-50 degrees specified by OSHA, it exceeded the most efficient slope recommended by Lehmann65 by 13 to 18 degrees. Also, substituting the 8.5 inches for “h” and 9.0 inches for “d” in the formula gives the result 2(8.5) + 9.0 = 26.0 inches, which is 1.2 inches greater than the ideal.
Other assessment tools Other ergonomics assessment tools that have been used previously in the facility to identify risk factors related to the various types of injuries and discomforts reported by the workers are the Rapid Upper Limb Assessment (RULA),78 the Rapid Entire Body Assessment (REBA),49 the Job Strain Index (JSI),82 and the Washington State Caution/Hazard Zones (WAC 296-62-051).136 Each of these tools focuses almost exclusively on the upper extremities, with the possible exception of REBA. Although REBA does not address stresses to the lower extremities specifically, it does include the effect of the legs in its postural analysis of the entire body. REBA is a postural analysis tool developed especially for the type of unpredictable working postures found in health care and other service industries.49 Because the working postures of a maintenance and service technician are often unpredictable, REBA was applied after the accident, in this particular case to determine the “action level” (i.e., risk level and action required) of the task of “descending the staircase while carrying a 24-pound tool.” The results of REBA are summarized below: ● Score A (trunk, neck, and legs) = 7 (on a scale of 1 to 12) ● = 4 + 2 (load/force: > 10 kg for the 24-lb tool) + 1 (load/ force: shock or rapid buildup of force from “misjudgment” of step)
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Score B (upper arms, lower arms, and wrist) = 1 (on a scale of 1 to 12) Score C (combination of scores A and B from Table C) = 7 (on a scale of 1 to 12) REBA score = 9 (on a scale of 1 to 15) ● = 7 (score C) + 1 (activity score: static load of carrying tool) + 1 (activity score: action caused rapid large range in postures or an unstable base) REBA action level = 3 (on a scale of 0 to 4) ● “High” risk level requiring action “necessary soon.”
In retrospect, if REBA had been applied beforehand, it would have identified the task as “high” risk in need of corrective action soon, but a question remains: What would have, or should have, triggered the necessity for an assessment, since simply returning a tool to the tool crib typically would not be considered a particularly hazardous task? Answer: The repairs to the bridge should have prompted a safety inspection and an ergonomics assessment of the “changes” made to the walking and working surfaces over the bridge.
Conclusions and corrective actions As a result of the accident and injury and following the assessments according to OSHA 29 CFR 1910.24 (e) and (f), Lehmann’s65 empirical data, and REBA, the following conclusions were made and corrective actions implemented: 1. The first three steps on the descending staircase of the bridge were replaced. The new risers were each 8-1/2 inches high and the tread runs 9 inches deep (accuracy ±1/8 inch). A complete inspection of the entire bridge and staircase was performed, and an inspection schedule of all bridges and staircases throughout the facility was developed. 2. The leading edges of all the steps at the bridge were made clearly identifiable using yellow and black diagonally striped tape. A plan and schedule to identify unmarked steps and to apply tape as needed was implemented. 3. The following long-term plans were made (Case Study Part 2 covers the long-term accommodations in greater detail): a. Reduce the slopes and change the risers and tread runs of the staircases at the location of the accident and throughout the facility to match Lehmann’s65 recommendations as closely as possible. b. Relocate the tool crib and strategically locate tool storage cabinets to minimize transit hazards (i.e., climbing and descending stairs), distances and times.
Case study part 2: Accommodations for chronic knee pain and work restrictions while walking, while climbing stairs, and during static standing subsequent to the knee injury described in case study part 1 The worker and task The 52-year-old maintenance and service technician described in the first part of this case study returned to his regular job in early June 2001, about 7 weeks after his knee injury. Although modifications had been made to the staircase that contributed to his injury and to many of the other staircases to bring them into
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compliance with OSHA 29 CFR 1910.24 (fixed industrial stairs),91 the job still required the following physical activities: ● Frequent walking on various surfaces; ● Ascending and descending staircases three to five times a day while carrying tools; ● Climbing portable and fixed ladders four to five times per week; ● Occasionally climbing on various machines and structures to perform maintenance and service tasks; ● Static standing on a concrete floor for up to an hour at a time; ● Occasionally crouching, once or twice a day, to work on low level equipment. Also, the safety hazards in the plant had not changed; therefore it was a requirement to wear full foot protection and all the personal protective equipment described in Case Study Part 1.
Modifications made and planned during the worker’s absence During the injured worker’s 7-week absence, the first three steps on the descending staircase of the bridge at the location of the accident were replaced with steps of the correct design and dimensions. Inspections and repairs of the most frequently used bridges and staircases throughout the facility were completed, and the leading edges of most of the steps were made clearly identifiable using yellow and black diagonally striped tape. In addition to the above modifications, the following longterm plans were made: 1. To reduce the slopes and change the risers and tread runs of the staircases at the location of the accident and throughout the facility to match Lehmann’s65 formula as closely as possible. 2. To relocate the tool crib and strategically locate tool storage cabinets to minimize transit hazards, such as climbing and descending stairs while carrying tools and excessive walking distances and times.
Physical discomforts, limitation, and work restrictions Upon returning to his job, the worker felt confident in his ability to perform the essential functions of the job and was relatively satisfied with the progress of his recovery. However, he reported mild to moderate pain and occasional swelling and joint stiffness, especially after walking for more than about 2 hours, standing for more than an hour, and especially after climbing stairs of slopes greater than about 40 degrees, climbing ladders more than twice daily, or crouching for more than a minute or two. Postoperative medical reports from the physician of record stated that the surgery to repair the medial collateral ligament in the right knee, as well as the subsequent recovery, had progressed with no complications; however, some preexisting degenerative joint disease (osteoarthritis) was discovered. The physician’s report placed restrictions on duration and frequency of walking, static standing, climbing stairs and ladders, and crouching and stressed the importance of avoiding reinjury from a slip, trip, or fall. A written opinion and functional capacity evaluation from a physical therapist stated that the worker had participated cooperatively in his rehabilitation program thus far and was progressing reasonably well; however, it would take approximately 1 year for
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him to reach maximum improvement in strength and range of motion. In summary, the opinions from the worker himself, the physician of record, and the physical therapist provided the following work restrictions for which reasonable accommodations were to be made during the first 6 to 8 weeks of his return to work (work restrictions to be reassessed after each 6- to 8-week period): 1. Walking is to be limited to 2 hours per day. 2. Static standing must not exceed 1 hour per day. 3. Staircases with slopes greater than 40 degrees are to be avoided. 4. Climbing portable and fixed ladders is to be restricted to twice daily. 5. To prevent unexpected or unnatural loading of the knee (i.e., twisting, lateral stress, hyperextension, extreme flexion, etc.), the most obvious slip, trip, and fall hazards should be identified and removed wherever practicable. 6. All crouching, squatting, kneeling, or any activity that requires the right knee to be flexed more than 90 degrees is to be avoided. 7. Climbing on structures without regulation steps, grab bars, walking platforms, and handrails must be avoided. 8. Jumping down from platforms or other structures is to be prohibited.
Assessment methods and tools In addition to ensuring compliance to the above restrictions for the injured worker, the following safety standards and ergonomics guidelines were to be enforced for the purpose of minimizing risk of injury (or reinjury) to any of the workers: 1. All staircases were to be equipped with railings and guards in compliance with OSHA 29 CFR 1910.23 (d)(1)(i) through (v).87 2. The most frequently used staircases were to be modified so that the tread heights and depths fit as closely as possible the following formula recommended by Lehmann.65 According to Kroemer and Grandjean,59 “stairs of these dimensions are not only the most efficient but also seem to cause the fewest accidents.” 2h + d = 630 mm (24.8 in), where h = riser height and d = tread depth 3. All portable ladders were to comply with OSHA 29 CFR 1910.25 (Portable wood ladders),91 and 1910.26 (Portable metal ladders),92 and with 1910.27 (Fixed ladders).93 4. All walking surfaces were to be inspected and brought into compliance with OSHA 29 CFR 1910.22 (General requirements)86 regarding housekeeping and aisles and passageways.
Controls and interventions Table 7e.2 shows the controls and interventions that were implemented over a period of approximately 90 days to facilitate compliance to the prescribed work restrictions, safety standards, and ergonomic recommendations.
Three-year follow-up In June 2004, a brief telephone interview of the injured worker was done to determine his condition and to check the current status and effectiveness of the workplace modifications. In summary,
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Table 7e.2 List of controls and interventions to facilitate compliance to work instructions, safety standards and ergonomic recommendations Restriction, standard, or guideline
Control or intervention
Walking < 2 hours per day
An electric-powered cart was purchased for transportation across flat surfaces. The main tool crib was moved to a central location and three tool cabinets were placed near the three most frequently visited work areas. Antifatigue matting was placed on the concrete floors in eight locations. Five adjustable-height standing support stools were placed where “standing work” was common. Five bridges with staircases were modified to comply with the formula 2h + d = 630 mm (24.8 in) which reduced their slopes from approximately 43 to about 35 degrees. All frequently used staircases with slopes > 40 degrees that couldn’t be modified were marked accordingly. A mobile “cherry picker” was purchased for the maintenance and service department. A videotape of all walking surfaces throughout the facility was developed and presented to management and all maintenance and surfaces technicians. A 1-year corrective action plan with monthly status checks was developed. A 2-hour training program in “preventing slips, trips, and falls” was given to all maintenance and service technicians. Two large electric motors and one pump were raised from floor level to elbow height. Two standing support stools were placed at these locations, and four adjustable “low stools” were placed near four machines where low-level work is performed regularly. Steps with slip-resistant treads, grab bars, and walking platforms were installed (welded) to two machines that are climbed on regularly.
Static standing < 1 hour per day Avoid staircase slopes > 40 degrees
Climbing ladders < twice daily Eliminate slip, trip, and fall hazards, and all walking surfaces must comply with 29 CFR 1910.2286 No crouching, squatting, or kneeling
No climbing on structures without steps, grab bars, etc.; and no jumping down from platforms All staircases must have railings and guards per 29 CFR 1910.23 (d)(1)(i) through (v)87
Frequently used staircases should comply with the formula, 2h + d = 630 mm
All ladders must comply with 29 CFR 1910.25, 26, and 2791-93
Stairways < 44 inches wide were inspected to comply with: Both sides enclosed–hand rail on right side descending One side open–stair railing on open side Both sides open–stair railing on each side Stairways > 44 inches but < 88 inches wide were checked for compliance with: Hand rail on each enclosed side Stair railing on each open side Stairways ≥ 88 inches wide were checked for: Hand rail on each enclosed side Stair railing on each open side Intermediate stair railing midway Although the bridge and staircase at the accident location plus four other bridges in the main walkway of the facility had been made OSHA compliant since the accident, they were further modified to comply also with the Lehmann formula. For example, the average riser and tread depth of the 43-degree steps at the accident location were changed from 8-1/2 and 9 inches, respectively, to 7-1/4 and 10-1/4 inches, which reduced the slope to about 35 degrees and required the bridge to be lowered and the staircases to be lengthened. All ladders were inspected and required to be in good condition or otherwise removed from service and tagged. A 2-hour training program in ladder safety, including maintenance and utilization of ladders, was given to all maintenance and service technicians.
the injured worker was still actively employed as a maintenance and service technician but in a more supervisory role. He estimated that his workload had been reduced approximately 20% to 30% since the time of his accident and shortly thereafter. His work restrictions have been lifted, but he still experiences occasional stiffness and discomfort in his right knee; however, he sincerely believes that the modifications to the bridges, stairways, and the other walking-working surfaces have made his
job, and the work of all the maintenance and service technicians, safer and less physically demanding. Since his accident in April 2001 and following the implementation of the workplace modifications described above, there have been no lost-time injuries reported from slips, trips, and falls according to the OSHA 300 logs. Comparatively, during the 3 years before the accident described in this case study there had been three other lost time accidents from slips, trips, and falls.
Chapter 7e
Summary and conclusions This two-part case study describes workplace modifications that were applied, in part 1, for the prevention of the recurrence of an acute injury resulting from a fall while descending a staircase and, in part 2, to accommodate the subsequent long-term pain, discomfort, and work restrictions of the injured worker. The task that was being performed when the injury occurred was assessed using the OSHA standard for walking-working surfaces, namely related to staircase design and construction and an ergonomic formula that suggests an efficient and safe relationship between staircase riser, tread depth, and slope. An ergonomic assessment of the task also was performed using the REBA tool. Each assessment method discovered noncompliances and risk factors that were determined to be likely contributors to the accident. The workplace modifications were directed toward correcting the noncompliances and eliminating or significantly reducing the ergonomic risk factors that were identified. A brief follow-up approximately 3 years after the accident indicated that the modifications were instrumental in allowing the injured worker to return to his regular job and to prevent recurrence of a similar accident and injury.
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CHAPTER
Ankle and Foot
8
CHAPTER
8a
Epidemiology of the Ankle and Foot Victor Valderrabano and Beat Hintermann
Acute and chronic injuries of the foot and ankle are among the most common injuries in the musculoskeletal system. Based on 15,000 completed questionnaires by family shoe store customers, it was determined that 40% of the population in the United States has foot problems, 12% of which have had surgery and 7% of which have been untreated.51 It has been reported that for every 300 men working in heavy industry, 15 working days per month are lost as a result of foot problems, 65% of which are the result of trauma.31 The amount of athletically related injuries is substantially increasing due to the aging population, the growing popularity of recreational sports activity in our society, and the greater numbers of professional active athletes. In sports practice, however, it is often difficult to distinguish and strictly separate work-related from recreation-related injuries. The following general comments on the epidemiologic assessment of disorders and injuries to the foot and ankle are meant to show the general problems and difficulties of attempting to reveal and compare data from a literature review. More detailed considerations about epidemiology are made separately for work-, military-, and sport-related injuries, although as mentioned earlier, strict differentiation between these activities is often not possible. The number of athletically related injuries has grown coincident with an enlarging search by the public for specialists to provide the necessary treatment. Hence, it is not surprising that athletic-related injuries are at this time among the best investigated. The knowledge gleaned from such specific studies has contributed to a better understanding of injuries occurring during work and military service and has led to improvements in equipment. Shoe construction and design, for example, have improved markedly due to the research activities of sport shoe companies.
METHODOLOGY OF EPIDEMIOLOGIC STUDIES: CRITICAL ASPECTS
injuries comes from accounts of case studies, many of which report an injury rate but often fail to define accurately the population at risk. For instance, the prevalent idea that runners who over-pronate are at a greater risk for injury, as reported by James et al,67 was fostered by noting that 58 of their 180 patients had a pronated foot configuration. This study does not take into consideration the total number of people in the running population from whom this select group was derived who also pronate but have not been injured. Another liability of epidemiologic studies is their failure accurately to define the factor to be analyzed. Sport injury studies show significant variations in the definition of what constitutes an injury. It is difficult, for example, to compare studies where an injury is anything that causes an athlete to require medical attention and lose time from participation15 with those that have much stricter definitions and classifications.62,132,134 The comparison difficulties are increased further when different sports and participation levels are compared. There may be significant differences between the injury of a recreational runner and that of a professional rugby player.26 In addition, elite and endurance athletes are characterized by the psychologic “iceberg” profile, which includes scores below the population average on mood states such as tension, depression, anger, fatigue, and confusion along with above average scores on vigor.92 During years of hard training, pain recognition and processing by the central nervous system may change. Finally, the homogeneity of the population being studied is important. This relates to such considerations as exposure to injury, age and gender differences, preexisting injury, and other variables that may significantly confound risk.27 Several studies have demonstrated, for instance, that weekly running mileage is the single most critical factor affecting injury risk in the running population.85,136 At distances of over 64 km (40 miles) per week, the injury rate seems to increase exponentially. Through all these studies, other risk factors have not been confirmed.
WORK-RELATED INJURIES Epidemiology Attempts to characterize and quantify work-related injuries to the foot and ankle are few. Jobs involving extensive manual material handling or vehicular operations are those most often listed by employees with foot-related injuries.
Etiology One of the goals of preventive medicine is to reduce the health risk of both occupational exposure and athletic participation through recognition and control of the risk factors. From the vantage point of careful epidemiologic study, it is possible to identify and quantify risk along with the incidence and prevalence of injury for a given set of conditions.107 To analyze epidemiologic data properly, it is critical for the population being analyzed to be assiduously defined. Many studies of athletic injuries that have engendered prejudicial thinking about injury causes are flawed because of their methodology.27 Most of the existing information on observed causes of athletic
Work-related foot and ankle injuries have been associated with falling from ladders;100 being struck by boxes, metal objects, or vehicles; being caught in, under, or between vehicles or machinery;98 and having cut or laceration injuries. O’Sullivan et al100 showed that ladder fall injuries are associated with foot fractures, the male gender (89%), a median length and hospital cost of 1 week and US$3950, respectively, and a median duration of disability and unemployment of 6 weeks. From a total of 990 work-related injuries to the foot, being struck accounted for 58% across occupational groups.98 Regardless of
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Epidemiology of the ankle and foot
the industry group, metal items and vehicles were related to 51% of all work-related foot injuries. Bazroy et al7 found 15% of cuts and laceration injuries to the foot and ankle in a glass bottle manufacturing plant. Significant risk factors were age (less than 30 years) and experience (less than 2 years). Technical factors responsible for injury were a hazardous work site in 37 cases (38.5%), inadequate protection with safety wear in 32 cases (33%), and proximity to machines in 14 cases (14.6%). Human factors identified were lack of protective wear in 43 episodes (45%), overconfidence in 18 episodes (18.7%), and timing error while working with machines in 11 episodes (11.4%).
Prevention To reduce the incidence of foot injuries, workers in many industries are required to wear safety footwear incorporating a steeltoed cap. In Australia, an investigation of 321 workers employed in a broad range of work activities and required to wear safety footwear revealed an extremely high percentage of subjects (91%) reporting one or more foot problems that were verified by a professionally trained podiatrist.84 Most of these subjects believed that the safety footwear either caused the problem or adversely affected an existing foot condition. The main shoe concerns were excessive heat (65%), inflexible soles (52%), weight (48%), and pressure from the steel-toed cap (47%). As the priority, safety may obviously conflict with comfort. Ideally, knowledge would compromise with experience in choosing shoes for industry workers to allow the best possible supply of safety footwear.
MILITARY-RELATED INJURIES Epidemiology Lower limb injuries, mainly to the foot and ankle, are the most common injuries in military service. In a survey of 350 male recruits of the Royal Australian Army Corps, Rudzki115 reported an 80% rate of foot and ankle injuries. Among the U.S. Marine Corps, training-related initial injuries to the foot were found at a rate of 3.0 new injuries per 1000 recruit-days.80 The highest specific rates of injuries occurred with stress fractures to the foot (0.56 per 1000 recruit-days), ankle sprains (0.53), and Achilles tendinitis (0.39). In a prospective study, Bush et al21 examined the epidemiology of blisters and their association with subsequent injuries in 2130 male U.S. Marine Corps recruits, who experienced an incidence of 2.05 blisters per 100 recruit-months. Recruits with blisters were 50% more likely to experience an additional trainingrelated injury. In combination with other related injuries, blisters resulted in 159 clinic visits, 103 days of assigned light duty, and 177 days lost from training. Among an air assault division, foot and ankle injuries were the most prevalent and severe category of injury for combat unit soldiers.39 In a 1-year period, the average combat unit soldier sustained 0.16 foot injuries with an estimated 3.2 effective duty days lost. A prospective study of 295 male Israeli military recruits reported a 31% incidence of stress fractures,90 most of which (80%)
were in the tibial or femoral shaft, whereas only 8% occurred in the tarsus and metatarsus. Excessive rates of stress fractures were found also by other authors.13,14,47,114
Etiology Stress fractures (Fig. 8a.1) are common injuries sustained during military training. Improper advance physical preparation and excessive physical demands during military service may cause most of these injuries to the foot and ankle.13,14,48,72 Typically, fatigue fractures have been seen mostly in the first months of service, indicating an acute overuse injury of bones.114 In the past, pes planus or flatfeet have been a disqualifying factor for military service. Specific studies, however, have shown that those recruits with flat or pronated feet had no greater incidence of stress fracture than the normal population.49 Rudzki116 showed that abnormalities of the foot (pes planus, pes cavus, hallux valgus) were not significant factors in the development of injury during recruit training. In contrast, another study, this one involving Israeli military recruits, showed that those with low arches had a higher incidence of metatarsal stress fractures than did those with higher ones, whereas the number of stress fractures of the tibia and femur was lower in low-arch than in high-arch feet.121 Heavy loads have been recognized as a risk factor for foot and ankle injuries during endurance exercises in the military. Reynolds et al105 reported that 36% of soldiers were injured during a 161-km march over 5 days carrying an average load mass of 47 kg. In this study smoking and younger age (< 20 years) were independent risk factors for injuries. Other causes of military-related foot and ankle injuries are cold weather injuries30,88,128 and inflammatory foot lesions.63 Milgrom et al88 showed evidence of cold weather being a risk factor for Achilles paratendinitis. They explained that a fall in temperature of the Achilles paratendon may increase the viscosity of the lubricant, in turn increasing friction and risk for Achilles paratendinitis.
Prevention In general terms, “warming up” before exercising may be one of the most important factors in lowering acute foot and ankle injuries.88 Meticulous foot care such as skin and nail hygiene may prevent infections and blisters. Furthermore, higher quality and ergonomics of shoes, insoles, and equipment may avoid overload injuries effectively. To determine the effect of appropriate shoe fit and training shoe type on the incidence of overuse injuries, the Israeli Defense Forces Medical Corps conducted a prospective study.38 Among infantry recruits, they found that three shoe widths for each shoe length size were necessary to adequately accommodate the recruit population’s foot anatomy. Recruits compensated for the lack of available shoe widths by choosing larger shoe sizes, which did not result in a higher incidence of overuse injuries. Switching to tennis sport shoes substantially reduced calcaneal stress fractures in military recruits.52 A study of South African
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B
Figure 8a.1 Stress fracture metatarsal V (Jones fracture). (A) Stress fracture of the fifth metatarsal in a basketball athlete (symptoms: chronic pain on the lateral aspect of the midfoot and sport disability after 5 months of conservative treatment). (B) Surgical treatment with open reduction and internal fixation (intramedullary compression screw).
military recruits reported a reduction in overuse injuries by incorporating a shock-absorbing neoprene insole into the shoe used in training.119 Surprisingly, however, no mid- to long-term studies have systematically assessed the effectiveness of footwear improvements on soldier fitness.
SPORT-RELATED INJURIES
If injury rates for the foot and ankle are determined from studies performed for various sports (Table 8a.1), the magnitude of the athletic injury problem can be estimated by multiplying these rates by the number of participants in the given sport. Obviously, some sports have an extremely high risk for injuries to the ankle or foot (Table 8a.1), whereas the injury rate is minimal in others, such as golf, boating, cycling, equestrian, fishing, parachuting, or bowling.
Epidemiology Etiology Injuries to the lower extremities constitute most injuries in most sports, especially those involving running, jumping, and kicking. Twenty-five percent of 12,681 injuries in the top 19 most common sports injuries seen in a multispecialty sports medicine clinic occurred at the ankle and foot. The percentages of foot and ankle injuries varied substantially from sport to sport, as did the proportion of sprains versus overuse injuries at each location.46
The risk of sustaining an injury in a given sport may depend on different factors such as velocity, exposure to other players or obstacles, playing environment, training techniques, and equipment. These are among some of the extrinsic factors, whereas the individual’s physical and personality traits constitute the intrinsic factors.27 The factors most associated with injuries to the foot
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Table 8a.1
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Epidemiology of the ankle and foot
Foot and ankle injury rates in high-risk sports: a literature review
Sport
First author
Year
Skill level
Ankle injury
Foot injury
Ballet Basketball
Garrick43 Henry56 Zelisko143 Prebble104 Washington137 Rovere112 du Toit33 Moretz91 Sutherland127
1986 1982 1982 1999 1978 1983 2001 1978 1976
Park101 McLennan86 Tomczak131 Johansson71 Hintermann60 Gottlieb50 Temple129 Marti85 Walter136 Bishop12 Smith123 Brown18 Pino103 Bladin15 Bridges17 Ekstrand34 Nielsen95 Berger-Vachon9 Woods141 Berson10 Soderstrom124 Schafle117 Solgard125
1980 1983 1989 1986 1992 1980 1983 1988 1989 1999 1982 1987 1989 1993 2003 1983 1989 1986 2003 1978 1982 1990 1995
Various levels Professional Professional Various levels Various levels Students Various levels High school Amateur High School College Professional Junior NA NA Elite Various levels Recreational NA NA Recreational Professional Age 11-19 yr National males Recreational Various levels Various levels Swedish senior division Various levels French amateur leagues Professional Recreational NA National amateur Various levels
17% 18% 19% 33% 17% 22% F&A 31% 0% 0% 7% 0% 4% 41% 40% 26% 24% 19% 26% 30% 15% 36% 29% 8% 26% F&A F&A 17% 36% 20% 11% 21% 20% 18% 31%
22% 6% 4% NA 15% 15% 33% 8% 0% 0% 10% 0% 1% 8% 35% 13% 11% 11% 26% 10% 16% NA 8% 8% 3% 23% 10% 12% 8% NA NA 2% 7% 6% NA
Dance
Football Ice hockey
Mountaineering Orienteering Running
Skating (ice) Snowboarding
Soccer
Squash/racquetball Volleyball
F&A, foot and ankle; NA, not available. Adapted from Clanton TO, Wood RM: Etiology of injury to the foot and ankle. In JC DeLee, D Drez, MD Miller, eds: Orthopaedic sports medicine—principles and practice. Philadelphia, 2003, W.B. Saunders, pp. 2224-2274.
and ankle in sports include anatomic or biomechanical abnormalities, lack of flexibility, poor strength, muscle imbalance, type of shoe and/or use of orthoses, and type of playing surface.26,27
Anatomic/biomechanical abnormalities Various anatomic conditions have been frequently associated with athletic injuries: Alignment of the lower extremity and/or over-pronation has been associated with injuries to the knee, ankle, and foot, and foot configuration has been associated with stress fractures of the lower extremity (Fig. 8a.2). The belief that runners who over-pronate initially have a higher risk of sustaining a running-related injury is still held by most runners
and their coaches, although no reliable study has supported this assumption. Probably the most comprehensive study of runningrelated injuries, the Ontario cohort study, showed that none of the anthropometric variables, such as femoral neck anteversion, knee and patella alignment, rearfoot valgus, pes cavus/planus, and running shoe wear pattern, was significantly related to risk.136 Foot and ankle injuries in dancing such as ankle sprains, fatigue fractures, or tendon ruptures have been related to poor technique and malalignment.19,32,66,82 Kinetic chain dysfunctions of the foot have been described in dancers secondary to primary injuries.82 Indeed, anatomic/biomechanical alterations appear to be causally related to injury. Busseuil et al and other reports have
Chapter 8a
Figure 8a.2 Foot and ankle overload injuries. Foot and ankle overload injuries (stress fractures, tendonitis, and others) are very common in endurance sports, as marathon running. (Picture: IronMan Triathlon, Zürich, Switzerland, 2003.)
shown that hindfoot valgus correlates with a higher risk for foot and ankle injuries.22,27,58 The use of inverting shoe orthotics in athletes with over-pronation may significantly prevent overuse foot and ankle injuries.27,58,140
Flexibility and stability Lack of flexibility as a result of limited joint motion is a common cause of injuries to the foot and ankle. Restricted dorsiflexion at the ankle joint is a factor in the anterior ankle pain (soccer ankle) often seen in soccer players that is associated with anterior tibial osteophytes and/or a meniscoid lesion.37 Two different hypotheses have been described to explain the formation of talotibial osteophytes in the anterior ankle impingement syndrome: hyperplantar flexion vs. recurrent ball impact. In a biomechanical study, however, Tol et al130 supported the hypothesis that spur formation in anterior ankle impingement syndrome is related to recurrent ball impact, which can be regarded as repetitive microtrauma to the anteromedial aspect of the ankle. In addition, other problems around the foot and ankle, including turf toe,25,111,138 bunions,6 midfoot strain and plantar fasciitis,5,28,108,109 ankle sprains,36,44,65 Achilles tendonitis,139 calf strains,1,34 and hyperpronation22,27,58 are believed to be due to restricted ankle dorsiflexion. Although these conditions have been related to a tight Achilles tendon, however, no study has yet confirmed such an association. A deficit of dorsiflexion at the first metatarsophalangeal joint, as is typically the case in hallux rigidus,83 has been related to turf toe injuries.25,138 Limitation of motion at the interphalangeal joint is often connected to deformities such as hammer toe or mallet toe and thus creates a problem.24 On the other hand, hypermobility can cause injury problems also at the foot and ankle. The hypermobility syndrome has been described as a potential source of musculoskeletal symptoms.27 In most cases this syndrome has no association with connective tissue disorders, including Down syndrome, Marfan syndrome,
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Sport-related injuries
Ehlers-Danlos syndrome, and osteogenesis imperfecta. In certain sports, however, high flexibility is needed. Ballet dancers, divers, and gymnasts are particularly noted for the tremendous mobility in their feet and ankles that allows them to achieve maximum plantar flexion so that the foot is parallel to the lower leg. Although such increased mobility has obvious advantages, an increased incidence of injury was noted in those ballet dancers who have greater mobility.78 Alternatively, maximum plantar flexion can create posterior ankle pain from impingement. A pathologic increase in joint laxity, ankle instability27,62 is seen commonly in a few high-risk sports activities such as soccer, basketball, orienteering, and others (Table 8a.1). Instability in the ankle joint can be classified as lateral, medial, or rotational instability and as acute or chronic. Chronic ankle instability (CAI) has become very epidemiologically important in sports medicine and orthopedics in recent years, leading to increased health care costs and risk of posttraumatic osteoarthrosis of the ankle.53,54 It is well known that ankle sprains are among the most common injuries occurring during sports activities,44 caused in 85% of the cases by an inversion trauma.4 More than 23,000 ankle sprains occur per day in the United States.74 Although most of these ligamentous ankle injuries can be treated successfully with physical rehabilitation and nonoperative treatment, 20% to 40% of patients with ankle injuries go on to experience CAI and subsequent disability.16,40 The most common predisposition factor for CAI seems to be the history of having suffered an ankle sprain in the past.36,142 The pathomechanism involved in CAI may be mechanical instability133 (posttraumatic ligament laxity, intraarticular pathologies, altered joint mechanics), functional instability40,41,57 (proprioception, neuromuscular control, or strength deficit), or a combination of both.133 Concerning the link between proprioception and neuromuscular joint control, it has been demonstrated that CAI leads to deficits in ankle proprioception, nerve conduction velocity, neuromuscular response times, postural control, and strength. Evidence suggests that alteration in muscle-spindle activity of the muscles stabilizing the ankle may be more important than altered articular mechanoreceptors.76 Strength reduction for eversion and inversion has been described.55,73
Strength The belief that weak musculature predisposes an individual to sports injury has been supported by various studies. Soccer players who sustained a minor injury during the preceding 2 months with subsequent inadequate rehabilitation and poor muscle strength had a 20% increase in risk for a more serious subsequent injury.34,36 Among 1139 young soccer players, 216 injuries, most involving the ankle joint, were observed during a summer training camp.3 The highest incidence of injury occurred in boys who were tall and had weak grip strength, which suggests that skeletally mature but muscularly weak players were at increased risk for injury as compared with their peers. Other studies concluded that strength differences of more than 10% between the right and left legs increases the risk for injury.8,20 This finding corresponds to the observation that the institution of a prophylactic program, including rehabilitation to the point that 90% of muscle strength had been regained, reduces the incidence of injury in soccer players by 75%.35 Other studies also have shown that improving strength can reduce the risk for reinjury.2,34
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Shoe wear and orthoses Foot fixation on a playing surface resulting in abnormal torque is the most commonly cited etiologic factor for noncontact injuries to the knee and ankle.27 Obviously dependent on the playing surface, these injuries are often attributed to the shoe-surface interface. This aspect is discussed in a later section.
A shoe that is fitted improperly and overly high causes pressure-related pain at the site of bunions and bunionettes. As examples, one can see aggravation of a bunion in a metatarsus primus varus or an accessory navicular from an ice skating boot and irritation of the Achilles tendon from many varieties of shoe wear. It could be that local pressure at the heel may in some
A
B
C
D
Figure 8a.3 Fracture of the lateral process of the talus (LPT): “snowboarder’s ankle.” The LPT fracture is a snowboarding-specific foot and ankle injury that can easily be missed by being considered a simple ankle sprain. The most frequent injury mechanism is a combination of axial impact, dorsiflexion, external rotation, and eversion. Early and appropriate treatment based on fracture type may determine the outcome. (A) Acute lesion with swelling and beginning hematoma. (B) Computed tomography with imaging of the displaced LPT fracture. (C) Intraoperative situs after removal of the LPT fragment (D) in preparation for internal fixation with two screws.
Chapter 8a
cases produce retrocalcaneal bursitis.139 The painful irritation of the retrocalcaneal bursa often seen in runners and cross-country skiers,61 however, is likely to be caused less by an improperly fitted shoe heel than by friction resulting from gliding of the tendon over the posterior calcaneal bone due to eversion-inversion movement of the calcaneus.61 When the shoe is too short, the toes jam into the end and nail problems occur; a shoe that is too loose allows the foot to slide, and blisters result. A lack of cushioning and/or support by the shoe has been implicated also as a specific factor in overuse injuries.96,97 Whereas some reports have shown beneficial effects of cushioned shoes in reducing injuries,94,119 other studies have been less conclusive or have shown no benefit from increased shock absorption in either shoes or insoles.42,87,89 The authors hypothesize that excessive cushioning can actually be an etiologic factor in injury by dampening the body’s own sensory feedback mechanism coming from the plantar surface of the foot, a “pseudo-neurotropic” effect that has been shown by other authors as well.110 The importance of proper shoe equipment is exemplified by snowboarding over the last decades. One of the main reasons for increase of foot and ankle injuries and fractures of the lateral process of the talus (LPT) among snowboarders was the snowboarding shoe-binding equipment23,29,77 (Fig. 8a.3). According to Kirkpatrick et al,77 LPT fractures occurred in 63% of their observed cases in soft boots, 23% in hard boots, and 14% in hybrid boots. They further showed, however, that most riders use soft boots (78%), followed by hard boots (15%), and hybrid boots (7%),77 perhaps explaining the increased incidence of the LPT fractures using soft boot technology.135 Torque is one of the most dangerous forces to which the body is subjected in sports.27 Cleating of the athletic shoe is designed to improve traction for more efficient performance but can significantly contribute to rotational load.118 The number, length, and pattern of the cleats132 as well as the outsole material and sole pattern106 have been shown to influence traction substantially. In a high school football program that has been studied, the number of ankle injuries was halved by changing from the traditional seven-cleated grass shoe to a soccer-style shoe.113 On the other hand, a lack of traction can potentially cause injury by increasing the frequency of slips and falls.27 In one study, for example, slipping on wet tennis surfaces was a factor in 21% of injuries.11 Obviously, superior performance demands maximum traction, but at some point this can exceed the body’s ability to handle the load.
Playing surfaces Resurfacing and maintaining grass practice and game fields can reduce injury rates about 30%.93 Several studies of soccer,64 dance,45 and ice hockey120 indicated also that the playing surface is a factor relevant to injury. In softball, Janda et al69 found that the main recreational injuries were related to sliding into fixed bases. They showed that reduction of serious injuries could be obtained by using breakaway bases, which demonstrates also a potential for significant savings in medical care costs.68,70 In running, however, although the opinion is widely held that hard surfaces and hills are big factors in injuries, several studies did not prove a relationship between surface and injury.81,136
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References
Prevention As mentioned in the preceding section, analysis of risk factors sometimes makes it possible to intervene in a way to reduce or eliminate the risk factor and thereby lower the risk for injury. This is indeed the aim of preventive sports medicine. Examples of such intervention include rule changes in football to eliminate the “crackback” block102 and improved generations of synthetic grass and underpadding brought about by research into the relationship between artificial turf and injury.79,122 In softball and baseball, interventions such as breakaway bases, batting helmets, face shields on helmets, lighter mass balls, and teaching and reiteration of the fundamentals of softball and baseball all have been effective in preventing millions of injuries and billions of dollars in health care costs each year in the United States.68 During a 3-year follow-up in junior elite cross-country skiers, the prevalence of overuse injuries to the lower extremity decreased from 62% to 22% when individual shoe adaptations and/or orthotic devices were made.59 Supervision by a doctor and physiotherapist;35 reduction in muscle tightness;34 use of shockabsorbent insoles,94,119 orthotic devices,121 external support75 or prophylactic ankle taping;99 and injury prevention through barefoot adaptations110,126 are among some of the preventive means to reduce injuries to the foot and ankle.
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Hertel J: Functional instability following lateral ankle sprain. Sports Med 29:361-371, 2000. Hintermann B: Long-term results after static correction of the lower extremity in young cross-country skiers. Swiss Praxis 81:389-393, 1992. Hintermann B: Shoe supports and corrective shoes in performance athletes—a 3-year study in young cross-country skiers. Schweiz Rundsch Med Prax 81:389-394, 1992. Hintermann B, Hintermann M: A study of the 1991 Swiss 6-days orienteering event. Sci J Orienteering 2:72-78, 1992. Hintermann B, Holzach P: Sub-Achilles bursitis—a biomechanical analysis and clinical study. Z Orthop Ihre Grenzgeb 130:114-119, 1992. Hintermann B, Valderrabano V, Boss A, Trouillier HH, Dick W: Medial ankle instability: an exploratory, prospective study of 52 cases. Am J Sports Med 32:183-190, 2004. Hodges GR, DuClos TW, Schnitzer JS: Inflammatory foot lesions in naval recruits: significance and lack of response to antibiotic therapy. Mil Med 140:94-97, 1975. Hoff GL, Martin TA: Outdoor and indoor soccer: injuries among youth players. Am J Sports Med 14:231-233, 1986. Holmer P, Sondergaard L, Konradsen L, Nielsen PT, Jorgensen LN: Epidemiology of sprains in the lateral ankle and foot. Foot Ankle Int 15:72-74, 1994. Howse J: Disorders of the great toe in dancers. Clin Sports Med 2:499-505, 1983. James SL, Bates BT, Osternig LR: Injuries to runners. Am J Sports Med 6:40-50, 1978. Janda DH: The prevention of baseball and softball injuries. Clin Orthop 409:20-28, 2003. Janda DH, Wild DE, Hensinger RN: Softball injuries. Aetiology and prevention. Sports Med 13:285-291, 1992. Janda DH, Wojtys EM, Hankin FM, Benedict ME, Hensinger RN: A three-phase analysis of the prevention of recreational softball injuries. Am J Sports Med 18:632-635, 1990. Johansson C: Injuries in elite orienteers. Am J Sports Med 14:410-415, 1986. Jones RO, Christenson CJ, Lednar WM: Podiatric utilization referral patterns at an Army medical center. Mil Med 157:7-11, 1992. Kaminski TW, Hartsell HD: Factors contributing to chronic ankle instability: a strength perspective. J Athl Train 37:394-405, 2002. Kannus P, Renstrom P: Treatment for acute tears of the lateral ligaments of the ankle: operation, cast, or early controlled mobilization. J Bone Joint Surg Am 73:305-312, 1991. Karlsson J, Andreasson GO: The effect of external ankle support in chronic lateral ankle joint instability. An electromyographic study. Am J Sports Med 20:257-261, 1992. Khin MH, Ishii T, Sakane M, Hayashi K: Effect of anesthesia of the sinus tarsi on peroneal reaction time in patients with functional instability of the ankle. Foot Ankle Int 20:554-559, 1999. Kirkpatrick DP, Hunter RE, Janes PC, Mastrangelo J, Nicholas RA: The snowboarder’s foot and ankle. Am J Sports Med 26:271-277, 1998. Klemp P, Chalton D: Articular mobility in ballet dancers. A follow-up study after four years. Am J Sports Med 17:72-75, 1989. Levy IM, Skovron ML, Agel J: Living with artificial grass: a knowledge update. Part 1. Basic science. Am J Sports Med 18:406-412, 1990. Linenger JM, Shwayhat AF: Epidemiology of podiatric injuries in US Marine recruits undergoing basic training. J Am Podiatr Med Assoc 82:269-271, 1992. Macera CA, Pate RR, Powell KE, Jackson KL, Kendrick JS, Craven TE: Predicting lowerextremity injuries among habitual runners. Arch Intern Med 149:2565-2568, 1989. Macintyre J, Joy E: Foot and ankle injuries in dance. Clin Sports Med 19:351-368, 2000. Mann RA: Intermediate to long term follow-up of medial approach dorsal cheilectomy for hallux rigidus. Foot Ankle Int 21:156, 2000. Marr SJ, Quine S: Shoe concerns and foot problems of wearers of safety footwear. Occup Med Lond 43:73-77, 1993. Marti B, Vader JP, Minder CE, Abelin T: On the epidemiology of running injuries. The 1984 Bern Grand-Prix study. Am J Sports Med 16:285-294, 1988. McLennan JG, Ungersma J: Mountaineering accidents in the Sierra Nevada. Am J Sports Med 11:160-163, 1983. Milgrom C, Burr DB, Boyd RD, Robin GC, Higgins WL, Radin EL: The effect of a viscoelastic orthotic on the incidence of tibial stress fractures in an animal model. Foot Ankle 10:276-279, 1990. Milgrom C, Finestone A, Zin D, Mandel D, Novack V: Cold weather training: a risk factor for Achilles paratendinitis among recruits. Foot Ankle Int 24:398-401, 2003. Milgrom C, Giladi M, Kashtan H, et al: A prospective study of the effect of a shock-absorbing orthotic device on the incidence of stress fractures in military recruits. Foot Ankle 6:101-104, 1985. Milgrom C, Giladi M, Stein M, et al: Stress fractures in military recruits. A prospective study showing an unusually high incidence. J Bone Joint Surg Br 67:732-735, 1985. Moretz A III, Rashkin A, Grana WA: Oklahoma high school football injury study: a preliminary report. J Okla State Med Assoc 71:85-88, 1978. Morgan WP, Costill DL: Selected psychological characteristics and health behaviors of aging marathon runners: a longitudinal study. Int J Sports Med 17:305-312, 1996. Müller FO, Blyth CA: A survey of 1981 college lacrosse injuries. Phys Sports Med 10:87-93, 1982.
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94. Mundermann A, Nigg BM, Humble RN, Stefanyshyn DJ: Foot orthotics affect lower extremity kinematics and kinetics during running. Clin Biomech 18:254-262, 2003. 95. Nielsen AB, Yde J: Epidemiology and traumatology of injuries in soccer. Am J Sports Med 17:803-807, 1989. 96. Nigg BM, Bahlsen AH, Denoth J, Lüthi SM, Stacoff A: Factors influencing kinetic and kinematic variables in running. In BM Nigg, ed: Biomechanics of running shoes. Champaign, IL, 1986, Human Kinetics, pp. 139-159. 97. Nigg BM, Stergiou P, Cole G, Stefanyshyn D, Mundermann A, Humble N: Effect of shoe inserts on kinematics, center of pressure, and leg joint moments during running. Med Sci Sports Exerc 35:314-319, 2003. 98. Oleske DM, Hahn JJ, Leibold M: Work-related injuries to the foot. Data from an occupational injury/illness surveillance system. J Occup Med 34:650-655, 1992. 99. Olmsted LC, Vela LI, Denegar CR, Hertel J: Prophylactic ankle taping and bracing: a numbers-needed-to-treat and cost-benefit analysis. J Athl Train 39:95-100, 2004. 100. O’Sullivan J, Wakai A, O’Sullivan R, Luke C, Cusack S: Ladder fall injuries: patterns and cost of morbidity. Injury 35:429-431, 2004. 101. Park RD, Castaldi CR: Injuries in junior ice hockey. Phys Sports Med 8:81-90, 1980. 102. Peterson TR: The cross-body block, the major cause of knee injuries. JAMA 211:449-452, 1970. 103. Pino EC, Colville MR: Snowboard injuries. Am J Sports Med 17:778-781, 1989. 104. Prebble TB, Chyou PH, Wittman L, McCormick J, Collins K, Zoch T: Basketball injuries in a rural area. WMJ 98:22-24, 1999. 105. Reynolds KL, White JS, Knapik JJ, Witt CE, Amoroso PJ: Injuries and risk factors in a 100-mile (161-km) infantry road march. Prev Med 28:167-173, 1999. 106. Rheinstein DJ, Morehouse CA, Niebel BW: Effects on traction of outsole composition and hardnesses of basketball shoes and three types of playing surfaces. Med Sci Sports 10:282-288, 1978. 107. Rice SG: Epidemiology and mechanisms of sports injuries. In CC Teitz, ed: Scientific foundations of sports medicine. St. Louis, 1989, Mosby-Year Book, pp. 3-23. 108. Riddle DL, Pulisic M, Pidcoe P, Johnson RE: Risk factors for plantar fasciitis: a matched case-control study. J Bone Joint Surg Am 85A:872-877, 2003. 109. Riddle DL, Pulisic M, Sparrow K: Impact of demographic and impairment-related variables on disability associated with plantar fasciitis. Foot Ankle Int 25:311-317, 2004. 110. Robbins S, Waked E: Humans amplify impact to compensate instability caused by shoe sole materials. Arch Phys Med Rehabil 78:463-467, 1997. 111. Rodeo SA, O’Brien S, Warren RF, Barnes R, Wickiewicz TL, Dillingham MF: Turf-toe: an analysis of metatarsophalangeal joint sprains in professional football players. Am J Sports Med 18:280-285, 1990. 112. Rovere GD, Webb LX, Gristina AG, Vogel JM: Musculoskeletal injuries in theatrical dance students. Am J Sports Med 11:195-198, 1983. 113. Rowe ML: Varsity football. Knee and ankle injury. N Y State J Med 69:3000-3003, 1969. 114. Ruckert KF, Brinkmann ER: Fatigue fractures of the calcaneus in soldiers of the Federal Forces. MMW Munch Med Wochenschr 117:681-684, 1975. 115. Rudzki SJ: Injuries in Australian Army recruits. Part II. Location and cause of injuries seen in recruits. Mil Med 162:477-480, 1997. 116. Rudzki SJ: Injuries in Australian Army recruits. Part III. The accuracy of a pretraining orthopedic screen in predicting ultimate injury outcome. Mil Med 162:481-483, 1997. 117. Schafle MD, Requa RK, Patton WL, Garrick JG: Injuries in the 1987 national amateur volleyball tournament. Am J Sports Med 18:624-631, 1990. 118. Schläpfer F, Unold E, Nigg BM: The frictional characteristics of tennis shoes. In BM Nigg, BA Kerr, eds: Biomechanical aspects of sport shoes and playing surfaces. Calgary, Canada, 1983, The University of Calgary, pp. 153-160.
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References
119. Schwellnus MP, Jordaan G, Noakes TD: Prevention of common overuse injuries by the use of shock absorbing insoles. A prospective study. Am J Sports Med 18:636-641, 1990. 120. Sim FH, Simonet WT, Melton L J III, Lehn TA: Ice hockey injuries. Am J Sports Med 15:30-40, 1987. 121. Simkin A, Leichter I, Giladi M, Stein M, Milgrom C: Combined effect of foot arch structure and an orthotic device on stress fractures. Foot Ankle 10:25-29, 1989. 122. Skovron ML, Levy IM, Agel J: Living with artificial grass: a knowledge update. Part 2. Epidemiology. Am J Sports Med 18:510-513, 1990. 123. Smith AD, Micheli LJ: Injuries in competitive figure skaters. Phys Sportsmed 10:36-47, 1982. 124. Soderstrom CA, Doxanas MT: Racquetball. A game with preventable injuries. Am J Sports Med 10:180-183, 1982. 125. Solgard L, Nielsen AB, Moller-Madsen B, Jacobsen BW, Yde J, Jensen J: Volleyball injuries presenting in casualty: a prospective study. Br J Sports Med 29:200-204, 1995. 126. Stacoff A, Kalin X, Stussi E: The effects of shoes on the torsion and rearfoot motion in running. Med Sci Sports Exerc 23:482-490, 1991. 127. Sutherland GW: Fire on ice. Am J Sports Med 4:264-269, 1976. 128. Taylor MS: Cold weather injuries during peacetime military training. Mil Med 157:602-604, 1992. 129. Temple C: Sports injuries. Hazards of jogging and marathon running. Br J Hosp Med 29:237-239, 1983. 130. Tol JL, Slim E, van Soest AJ, van Dijk CN: The relationship of the kicking action in soccer and anterior ankle impingement syndrome. A biomechanical analysis. Am J Sports Med 30:45-50, 2002. 131. Tomczak RL, Wilshire WM, Lane JW, et al: Injury patterns in rock climbers. J Osteopath Sports Med 3:11-16, 1989. 132. Torg JS, Quedenfeld TC, Landau S: The shoe-surface interface and its relationship to football knee injuries. J Sports Med 2:261-269, 1974. 133. Tropp H, Odenrick P, Gillquist J: Stabilometry recordings in functional and mechanical instability of the ankle joint. Int J Sports Med 6:180-182, 1985. 134. Valderrabano V, Hintermann B, Wischer T, Fuhr P, Dick W: Recovery of the posterior tibial muscle after late reconstruction following tendon rupture. Foot Ankle Int 25:85-95, 2004. 135. Valderrabano V, Perren T, Ryf C, Rillmann P, Hintermann B: Snowboarder’s talus fracture—treatment outcome of 20 cases after 3.5 years. Am J Sports Med 6:871-880, 2005. 136. Walter SD, Hart LE, McIntosh JM, Sutton JR: The Ontario cohort study of runningrelated injuries. Arch Intern Med 149:2561-2564, 1989. 137. Washington EL: Musculoskeletal injuries in theatrical dancers: site frequency, and severity. Am J Sports Med 6:75-98, 1978. 138. Watson TS, Anderson RB, Davis WH: Periarticular injuries to the hallux metatarsophalangeal joint in athletes. Foot Ankle Clin 5:687-713, 2000. 139. Wilder RP, Sethi S: Overuse injuries: tendinopathies, stress fractures, compartment syndrome, and shin splints. Clin Sports Med 23:55-81, 2004. 140. Williams DS III, McClay Davis I, Baitch SP: Effect of inverted orthoses on lowerextremity mechanics in runners. Med Sci Sports Exerc 35:2060-2068, 2003. 141. Woods C, Hawkins R, Hulse M, Hodson A: The Football Association Medical Research Programme: an audit of injuries in professional football: an analysis of ankle sprains. Br J Sports Med 37:233-238, 2003. 142. Yeung MS, Chan KM, So CH, Yuan WY: An epidemiological survey on ankle sprain. Br J Sports Med 28:112-116, 1994. 143. Zelisko JA, Noble HB, Porter M: A comparison of men’s and women’s professional basketball injuries. Am J Sports Med 10:297-299, 1982.
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8b
Anatomy and Biomechanics of the Ankle and Foot Victor Valderrabano and Beat Hintermann
FUNCTIONAL FOOT AND ANKLE ANATOMY A part of the lower extremity, the foot (pes), consists of 28 bones (Fig. 8b.1): 7 tarsal bones (talus, calcaneus, navicular, cuboid, medial, intermediate, and lateral cuneiforms), 5 metatarsal bones, 14 phalanges (two phalanges of the great toe, the other toes each three phalanges), and 2 sesamoid bones at the first metatarsophalangeal joint. The skeletal framework of the foot is divided into the tarsus (seven irregular bones), which is often subdivided into midfoot (navicular, cuboid, and the three cuneiforms) and hindfoot (calcaneus and talus). A total of 13 tendons crosses the ankle joint (extrinsic muscles) and inserts at a bone of the foot. Many more intrinsic muscles originate and insert within the foot itself. Over 100 ligaments are described in the foot and ankle, where they act as static stabilizers of the complex interplay of all the foot and ankle joints.
OSTEOLOGY Talus The talus consists of a body (corpus tali), a neck (collum tali), a head (caput tali), two processes (posterior and lateral talus processes), and a trochlea tali. The trochlea tali is wider anteriorly than posteriorly, which stabilizes the bony ankle mortise in dorsiflexion. The talus further shows a conic shape with radius smaller on the medial side than the lateral side, allowing the movement transfer from the foot to the lower leg and vice versa. In a cadaver study of 100 specimens, Inman29 determined that the medial angle of orientation of the talus (medial facet) measured 83.9 degrees with a range of 70 to 90 degrees. The lateral angle of orientation (lateral facet) formed a lateral angle averaging 89.2 degrees with a range of 80 to 95 degrees. From this data, Inman determined that the talus is not a cylinder but rather a section of a frustum of a cone, the apex of which is directed medially. Unique for the talus is its being covered by cartilage on two thirds of its surface and its having no muscular attachments. The inferior surface of the talus rests on the sustentaculum tali of the calcaneus, whereas anteriorly the bone articulates with the navicular. The talus articulates with the tibia and fibula in the ankle mortise (talocrural joint) and with the calcaneus (subtalar joint) and navicular (talonavicular joint) distally. The blood supply of the talus is performed by the posterior tibial artery (branch to the tarsal canal, branches to the deep fibers of the deltoid ligament), the anterior tibial artery/dorsalis pedis artery (branches to the neck, branch to the sinus tarsi), and the posterior peroneal artery.
Calcaneus
Phalanges
Cuneiform Medial Intermediate Lateral Navicular
Talus
I
The largest bone of the foot, the calcaneus (heel bone) projects posterior to the ankle joint to provide leverage for the triceps surae muscle group and origin for the plantar fascia. The lower surface of the posterior end of the bone (tuber calcanei) has rounded medial and lateral processes that provide contact surfaces during locomotion. Anteriorly the calcaneus articulates with the cuboid, and superiorly and medially the sustentaculum tali supports the talus at the subtalar (talocalcaneal) joint.
Metatarsals I–V
II III
Navicular
IV V Cuboid
Calcaneus
Figure 8b.1 Bones of the foot. The foot consists of 7 tarsal bones (talus, calcaneus, navicular, cuboid, medial, intermediate, and lateral cuneiforms), 5 metatarsal bones, 14 phalanges (two phalanges of the great toe, the other toes each three phalanges), and 2 sesamoid bones beneath the first metatarsophalangeal joint.
The navicular lies anterior to the talus on the medial side of the foot. It articulates proximally to the talus with an oval-concave articular surface, distally with the three cuneiform bones, and laterally with the cuboid. The navicular tuberosity serves plantar-medially as insertion structure for the posterior tibial tendon.
Cuneiform bones (medial, intermediate, and lateral) Lying in a series across the anterior surface of the navicular, the cuneiform bones articulate with the cuboid and the first three
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metatarsal bones. The medial cuneiform serves on its dorsal aspect as insertion structure for the tibial anterior tendon.
Cuboid The cuboid articulates posterior with the calcaneus, anteriorly with two lateral metatarsal bones, and medially with the lateral cuneiform. On the medial side the cuboid shows a groove for the peroneus longus tendon.
Metatarsals The metatarsals are long bones that each have a base, body, and head giving rise to five rays that culminate in a toe. The five metatarsal are numbered from medial to lateral I-V. The first metatarsal has a distal plantar cristae that articulates with the two sesamoids: the fibular/lateral and the tibial/medial sesamoid.
Phalanges The toes consist of short phalangeal bones: proximal, middle, and distal in the four lateral toes and proximal and distal in the hallux.
Subtalar joint The subtalar or talocalcaneal joint consists of the bony articulation of the talus and calcaneus building the posterior, medial, and anterior joint facets. The posterior facet is larger than the anterior and middle facets, is convex in shape, and articulates with the talar body. Situated on the sustentaculum tali, the middle facet is slightly concave. The anterior facet is concave and normally located just lateral to the middle facet. The middle and anterior facets articulate with the talar head. Between the posterior facet and the anterior and middle facets lies the tarsal canal, which opens broadly laterally and forms the sinus tarsi. The subtalar joint is stabilized by four ligaments, both intrinsic and extrinsic.71 The intrinsic ligaments are the interosseus talocalcaneal ligament, which fills the tarsal canal, and the cervical ligament (bifurcated ligament), which fills the sinus tarsi. Both the interosseus talocalcaneal ligament and cervical ligament can be injured in lateral ankle sprains or aggravated by conditions such as inflammatory arthritis, leading to subtalar instability.42 The extrinsic ligaments of the subtalar joint are the calcaneofibular ligament, the lateral talocalcaneal ligament (beneath the calcaneofibular ligament), the tibiocalcaneal ligament (superficial deltoid), the medial talocalcaneal ligament (medial talus tubercle-sustentaculum tali), and the posterior talocalcaneal ligament (lateral talus tubercle-posterior calcaneus).
Transversal tarsal and tarsometatarsal joints ARTHROLOGY Ankle joint The ankle or talocrural joint consists of the bony articulation of the distal tibia (tibial plafond), the medial malleolus and lateral malleolus (fibula), and the dome of the talus. The ankle joint is stabilized by several ligaments: the deltoid ligament (medial collateral ligament; complex arrangement of several ligaments in a deep and superficial layer6), the lateral collateral ligament complex (anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament), the anterior and posterior inferior tibiofibular ligament, the transverse tibiofibular ligament, and the interosseus ligament. Close11 found the deltoid ligament to be a strong restraint limiting talar abduction. With all lateral structures removed, the intact deltoid ligament allowed only 2 mm of separation between the talus and medial malleolus. When the deep deltoid ligament was released, the talus could be separated from the medial malleolus by a distance of 3.7 mm. The tibiocalcaneal ligament (the strongest superficial ligament) specifically limits talar abduction, whereas the deep portions resist more external rotation as well.16,61,62 In dorsiflexion, the posterior talofibular ligament is maximally stressed and the calcaneofibular ligament is taut, whereas the anterior talofibular ligament is loose. In plantar flexion, however, the anterior talofibular ligament is taut, and the calcaneofibular and posterior talofibular ligaments become loose.13,63,70 Some variation of this tension pattern is allowed by the different patterns of divergence between the anterior talofibular and calcaneofibular ligaments.
Chopart’s joint is the transversal tarsal joint built proximally by the talus and calcaneus and distally by the navicular and cuboid. Important ligaments within and around this joint are the plantar calcaneonavicular ligament (spring ligament; coxa pedis), the calcaneonaviculocuboid ligament (bifurcated ligament), the dorsal talonavicular ligament, and the dorsal and plantar calcaneocuboid ligaments. Lisfranc’s joint is the tarsometatarsal joint between proximally the cuneiforms and cuboid and distally the basis of the five metatarsals.59 The tarsometatarsal joints are stabilized by dorsal, plantar, and interosseus ligaments. The Lisfranc ligament is a strong plantar ligament that connects the medial cuneiform to the base of the second and longest metatarsal bone. In about 20% of patients, two separate bands of the Lisfranc ligament (dorsal and plantar) are present. Between the bases of the first and second metatarsals there are no ligaments, creating a relative weakness between the first and the other metatarsals. Another important midfoot and arch stabilizer is the plantar aponeurosis (also called plantar fascia). A strong fibrous tissue, the plantar aponeurosis has three components: central, medial, and lateral. The plantar aponeurosis arises from the os calcis and inserts into the metatarsals and the plantar aspects of the toes, making possible the windlass mechanism described by Hicks.23
Metatarsophalangeal joints The metatarsophalangeal joint of the hallux is different from those of the other toes by the sesamoid mechanism. Here the
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sesamoids articulate on their dorsal surfaces with the medial and lateral facets on the plantar aspect of the first metatarsal head. An intersesamoidal ridge (crista) separates these facets. The two sesamoids, lateral and medial, are incorporated into the two tendons of the flexor hallucis brevis. The first metatarsophalangeal joint is further stabilized on the plantar medial and lateral side by the fan-shaped collateral ligaments and sesamoidal ligaments. The hood ligaments of the extensor expansion and the capsule form the stabilizing structures dorsally.
FOOT ARCHES Morphologically, the foot may be described as having three arches. Longitudinally, the arch of the foot is higher on the medial than on its lateral side. The former involves the calcaneus, talus, navicular, cuneiforms, and three medial digits; the latter, although also arising from the calcaneus, proceeds through the cuboid and two lateral digits. In the midfoot region, the arch in the transverse plane is observed passing through the talus and navicular on the medial side to the calcaneus and cuboid on the lateral side. This arch gradually flattens anteriorly so that the heads of the metatarsal bones are all in the same plane. The arches are dynamically maintained by the following: ● The keystone effect of the talus, cuboid, and middle cuneiform within the medial, lateral, and transverse arches, respectively. The articular surfaces of these bones form a wedge that drops into place between adjacent bones. ● The bowstring effect of the plantar ligaments. The plantar calcaneonavicular (spring) ligament maintains the medial arch, whereas the short and long plantar ligaments maintain the lateral arch. ● The intrinsic and extrinsic muscles of the foot, which assist in maintaining the arches. Morphologically, it is convenient to describe the foot in terms of three discrete arches; however, when forces distributed throughout the foot are considered, there is a complex interplay of stresses that acts among all the components of a single dynamic structure. Clinically-morphologically and based on plantar pressure assessment, the human arch can generally be described as normal, high (pes cavus), or flat (pes planus) (Fig. 8b.2).
BIOMECHANICS OF THE FOOT AND ANKLE The foot is a specialized organ with the following contrasting characteristics (Fig. 8b.3): ● Support of body mass; ● Static and dynamic balance; ● Facilitation of locomotion. These characteristics are achieved by large muscles located in the shank, smaller intrinsic muscles of the foot, bony levers, and various degrees of joint mobility within the foot and ankle. Adequate muscular development and joint function are essential for normal gait and foot mechanics.
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Measurement of foot and ankle movement The ankle joint complex allows for relative movement between the foot and the leg. The following paragraphs concern possibilities to assess this movement, specifically addressing the clinical and functional assessment and the three-dimensional assessment.
Clinical and functional assessment Rotational movement between two segments occurs around a momentary axis of rotation determined primarily by the shape, the ligamentous structures, and the muscle-tendon units of the joint. Rotations describing the functional movement of two adjacent segments are those occurring around functional axes. The ankle joint complex is a peculiar joint in the sense that during locomotion one can estimate the location of two of the three bones that make up the joint, the tibia, and the calcaneus. It is practically impossible, however, to estimate the location of the talus during locomotion. Additionally, it is extremely difficult to determine the ankle joint axes87 around which the actual rotational movements occur. Consequently, it is difficult to describe the movement of the ankle joint complex by using functional axes. Movement of the foot, however, can be determined much more easily in a clinical environment by defining foot axes such as the anteroposterior, the mediolateral, and the inferosuperior axes. Movement of the foot can be defined with respect to the direction of locomotion,58 the position of the foot with respect to a laboratory coordinate system, or the position of the foot with respect to the leg. Specific descriptions of foot movement may be advantageous for specific questions. Foot movement with respect to the direction of movement of the center of mass may be appropriate for energy considerations. Foot movement relative to the leg may be appropriate for local loading aspects.83-85 In any case, it is crucial to define the system of reference clearly, because the results depend on it.
Three-dimensional assessment The rapid development of technology has provided gait analysis systems offering the possibility for three-dimensional movement analysis.58 This development is not without concerns, two of which, the use of two-dimensional analysis and the sequence of angle determination, are discussed shortly. For many questions, a two-dimensional approach is appropriate, and errors resulting from these restrictions are minimal. It is therefore appropriate to first check whether three-dimensional analysis is really necessary and what errors occur by changing to two-dimensional analysis. A three-dimensional rotational movement subdivided into its three rotational components provides different results depending on the sequence of the rotations chosen.1 One can easily verify this by moving the arm from an “initial position” where the arms are alongside the body with the palms facing its sides to a “final position” where the arm points horizontally at a 45-degree angle from the sagittal plane and the palms face the sides. The angular components used are extension, abduction, and axial rotation. One may reach the final position by first moving the arm upward and second by abducting it 45 degrees. This would correspond to an FL-abduction-axial rotation sequence with the values 90-45-0 degrees. One may reach the
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A
B
C
D
Figure 8b.2 The dynamic pedobarography (A) allows an objective and accurate assessment of the plantar pressure distribution (system used here: Emed, Novel, Munich, Germany). Variables such as contact area, peak forces, and center of pressure (COP) can be evaluated graphically and numerically. (B) The feet of a subject with normal arch; (C) the feet of a subject with a high arch (cavus foot); (D) the feet of a subject with a flatfoot deformity.
same final position, however, first by axially rotating the arm 45 degrees and second by extending the arm 90 degrees. This corresponds to an axial rotation-FL-abduction sequence with the values 45-90-0 degrees. Both movement sequences include 90 degrees of extension. The first movement sequence, however,
includes 45 degrees of abduction and no axial rotation, whereas the second movement sequence includes no abduction but 45 degrees of axial rotation. It is therefore important to understand for which movement analyses the sequence of the angular components is crucial.
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Many authors have argued about the appropriateness of some of the sequences.1,17 However, logical arguments described earlier54 that have used anatomic definitions of flexion-extension, abduction-adduction, and axial rotation indicate that the appropriate sequence in agreement with the definition of these movements for all human joints is as follows: In general Flexion-extension Abduction-adduction Axial rotation
For the ankle joint complex Plantar flexion-dorsiflexion Abduction-adduction Inversion-eversion
ANKLE JOINT COMPLEX MOTION Anatomic and biomechanical studies indicate that the ankle moves not as a pure hinge mechanism2,22,26,39 but rather in the sagittal, coronal, and transverse planes.39,41
Rotational axis and movement transfer of the ankle joint An early anatomic study pointed out that the wedge of the talus and the differing medial and lateral talar dome radii of curvature implied that tibiotalar congruency could not be maintained through sagittal motion unless the talus exhibited coupled axial rotation.2 The joint axis tends to incline down laterally when projected onto a frontal plane and posterolaterally when projected onto a horizontal plane.3,29,39 Because of this oblique orientation, dorsiflexion of the ankle results in eversion of the foot, whereas plantar flexion results in inversion. When the foot is fixed on the ground, dorsiflexion causes internal rotation of the leg, and plantar flexion causes external rotation.2,7,24,38, 67,73,84,93 This has been substantiated in kinematic tests of loaded cadaver ankle specimens.47,84 Having studied sagittal plane motion relative to the tibiotalar joint surface, Sammarco67 explained that the motion between the tibia and talus takes place about multiple instant centers of rotation. Ankles taken from plantar flexion to dorsiflexion showed a tendency toward distraction early in motion, followed by a sliding movement through the midportion that ends in compression at the end of dorsiflexion. This process was reversed when the joint was moved in the opposite direction. Locations and patterns of instant centers varied among different individuals, direction of motion, weight-bearing states, and pathologic states. An unstable ankle demonstrated normal gliding during weight bearing, but non-weight-bearing motion was grossly abnormal. Using stereophotogrammetry, Lundberg et al39 performed a three-dimensional evaluation of the joint axis in eight healthy ankles. They explained that talar rotation occurs about a dynamic axis during sagittal plane movement of the ankle, which in each subject lay close to the midpoint of a line between the tips of the malleoli. Plantar flexion axes were more horizontal and inclined down and medially compared with those of dorsiflexion. Most interestingly, no frontal plane movement occurred between the talus and the tibia during inversion/eversion of the loaded foot within a physiologic range of motion.
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Ankle joint complex motion
Van den Bogert et al87 showed a subject-specific threedimensional model of the ankle joint complex for calculation of the ankle and subtalar joint axis. The talocrural and subtalar joints were modeled as a three-segment system connected by two ideal hinge joints. A mathematical formulation was developed to express the three-dimensional translation and rotation between the foot and shank segments. Their results showed that the lateral side of the talocrural axis was directed slightly posterior (6.8 ± 8.1 degrees) and inclined down by 7.0 ± 5.4 degrees. Further, they showed that the inclination of the subtalar joint axis from the horizontal plane was 37.4 ± 2.7 degrees and the medial deviation was 18.0 ± 16.2 degrees. Leardini et al31 developed a mathematical model to explain the multiaxial motion of the ankle in the sagittal plane. These authors described a four-bar linkage model showing the talus/calcaneus and tibia/fibula rotating about one another on inextensible line segments that represent the calcaneofibular and tibiocalcaneal ligaments without resistance. Motion between the polycentric polyradial trochlea consisted of a combination of “rolling” and “sliding” motions. In this model, rotation is dictated by the most anterior fibers of the anterior talofibular and calcaneofibular ligaments. Leardini30 later observed that these specific fiber bundles were isometric through the range of sagittal motion of the ankle. The instant center of rotation translates from a posteroinferior to a superoanterior position, a finding consistent with several studies suggesting that the ankle is incongruent and rotates about a transient center.68,69,73 The complex and dynamic nature of the ankle’s axis of rotation may be one reason for poor results in total ankle replacement surgery and has important implications for the design of total ankle prostheses.
Ankle range of motion Overall values found in the literature for normal range of motion in the ankle range from 23 to 56 degrees of plantar flexion and from 13 to 33 degrees of dorsiflexion22,34,35,38,50,64,66,78,84,92,93 (Fig. 8b.3C and 8b.3D). Ten to 15 degrees of plantar flexion and 10 degrees of dorsiflexion are used during walking.66 About 14 degrees in range of motion are used in the stance phase of gait, whereas 37 degrees are needed for ascending and 56 degrees for descending stairs.78 In the diseased ankle, dorsiflexion is typically decreased and limits daily activities, especially in the presence of pain. Ten to 15 degrees of dorsiflexion are all that are needed for daily activities in patients who do not rely on their ability to ascend and descend stairs.39 The goal in total ankle replacement should therefore be to provide a minimum of 10 degrees of dorsiflexion and 20 degrees of plantar flexion for an appropriate push-off. Several factors influence sagittal plane motion of the ankle. Healthy older individuals demonstrate decreased plantar flexion.36,50,66 Sagittal motion (primarily dorsiflexion) has been found to increase significantly by assessing subjects while bearing weight as compared with passive measuring.35,64 Rotation of the ankle in the transverse plane is usually reported relative to instability,43,79 but transverse plane motion is coupled with that in the sagittal plane.11,37,39,46,66 Transverse plane motion is noted also during normal gait.11,37,38,73 Lundberg et al39
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A
B
C
D
Figure 8b.3 The function of the foot and ankle. The foot and ankle function mainly as a locomotion organ, allowing the plantigrade ambulation and providing support of body mass and static and dynamic balance. Anterior view of the weight-bearing static position of both feet (A), lateral view (B); plantar flexion of the ankle joint complex during heel rise test (C), dorsiflexion of the ankle joint complex during heel standing test (D).
observed 8.9 degrees of external rotation of the talus as the ankle moved from neutral position to 30 degrees of dorsiflexion, whereas a small amount of internal rotation occurred with plantar flexion from neutral to 10 degrees followed by external rotation at terminal plantar flexion.38 Michelson and Helgemo46 reported that dorsiflexion resulted in an average of 7.2 ± 3.8 degrees of external rotation of the foot relative to the leg with ankle dorsiflexion and 1.9 ± 4.12 degrees of internal rotation with
plantar flexion. In unloaded specimens, some coupling between the ankle and subtalar joints was observed also with sagittal plane motion.73 With dorsiflexion, there was internal rotation at the subtalar joint and external rotation at the ankle joint. The idea that this coupling is caused by tensioning of the deltoid ligament is supported by the findings of McCullough and Burge,43 who described greater external rotation of the talus after deltoid ligament sectioning.
Chapter 8b
Described as varus or valgus rotation, coronal motion may also be described as inversion or eversion. Michelson et al45 observed that plantar flexion of the ankle was associated with internal rotation and inversion. They attributed coronal plane motion to the position of the deltoid ligament, showing that after progressive medial ankle destabilization, talar external rotation and inversion increased.
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Internal forces and contact area
loaded conditions is provided by the articular surfaces. This has important implications in the design of total ankle prostheses and may explain poor results with prosthetic designs that expose the ankle ligaments to eversion and inversion forces while the ankle is loaded.84 During most activities, the soft tissues are the major torsional and anteroposterior stabilizers of the ankle,8,9 whereas its articulating surface geometry is the major inversion/eversion stabilizer, with collateral ligaments playing a secondary role.43,79
Restraints of ankle motion The stability and integrity of the ankle joint depends on articular geometry and ligamentous attachments. Ankle ligaments have a passive tracking and stability effect on the joint. On the medial side, the strong deep deltoid ligament is a secondary restraint against lateral and anterior talar excursion,6,19,63 whereas on the lateral side, the relatively weak anterior talofibular ligament is the only restraint against anterior talar excursion.32,48,63 The anterior talofibular ligament is that which is most susceptible to injury and subsequent insufficiency,4 often leading to anterolateral dislocation of the talus out of the mortise and posterior dislocation of the fibula, respectively. In such a case, reconstruction of the anterior talofibular ligament (or “ligament balancing”) may be advised when unconstrained prostheses are used for total ankle replacement. Several studies27,74 reported the effects of the lateral ligaments on axial rotation of the loaded ankle. Hintermann et al27 observed that the rotation of the tibia occurring after sectioning of the anterior talofibular ligament was more profound from neutral to plantar flexion than that observed in 10 to 20 degrees of dorsiflexion. When the deltoid ligament was sectioned, no tibial rotation was observed. This finding is consistent with those of Michelson et al,44 whose report suggested a motion-coupling role for the deltoid ligament in addition to stabilization. During walking, rotation occurs about a vertical axis.11,33 Rotatory stability is provided by tension in the collateral ligaments, by compression of the medial and lateral talar facets against their corresponding malleoli, and by the shape of the articular surfaces.19,43,74,79 Because of the truncated conical shape of the talus with its medially directed apex, the three separated lateral ligaments control the greater movement on the lateral side, whereas the deltoid ligament controls the lesser movement on the medial side. This has important implications for ligament balancing in total ankle replacement, because nonanatomic prosthetic design and/or inappropriate implantation may provoke medial ligament stress with consequent pain, posteromedial ossification, and loss of range of motion82 or lateral ligament insufficiency with consequent lateral ankle instability, respectively. Stability in the loaded ankle depends on articular shape.19,43,74,79 Stormont et al79 performed serial sectioning of the ankle ligaments and subjected the ankle to physiologic torque and loads. The articular surface accounted for 30% of ankle stability in rotation and 100% of ankle stability in inversion and eversion. In a similar study, McCullough and Burge43 found that with increased loading of the ankle, increased rotatory forces are necessary to cause displacement. The congruity of the articular surface of the ankle joint thus creates an inherently stable articulation with loading, and no ligamentous restraints exist in inversion and eversion. The sole restraint of the joint under
INTERNAL FORCES AND CONTACT AREA External forces acting on the human foot, geometric alignment of the foot and the leg, muscle forces, and segmental inertia forces are responsible for the internal forces acting in joints and on ligaments and tendons. Mathematical models are used to estimate the magnitude of forces in internal structures such as joints, tendons, and ligaments. These estimations use several (sometimes different) assumptions that are still being discussed in the literature.21 However, the order of magnitude of the estimated forces is assumed to be correct. Typically, the geometry of the acting forces (the distance from the line of action of an acting force to a joint of interest) is the most important factor that determines the internal forces. Technically, the internal forces in the anatomical structures of the human foot can be either measured directly in vitro or calculated from in vivo pressure distribution of the foot sole; in most cases the pedobarography technique using pressure distribution sensors is applied (Fig. 8b.2)12,87 The results of pressure distribution measurements have been used as localized input into the different foot structures to provide a possible means of quantifying internal forces in joints, ligaments, and tendons of the foot, an estimation that cannot be performed using the ground reaction force as input. In the ankle joint, a vertical load of 5.2 times body weight has been found during gait.78 In diseased ankles, the joint load decreased to approximately three times body weight, and the same values have been noted in replaced ankles.78 Anteroposterior and lateral shear forces during gait have been estimated to reach levels of two and three times body weight, respectively. With an interface area of 7 cm2, the average compressive load per unit area at the interface during gait would be approximately 3.5 MPa in a person of 700 N body weight. The complex geometry of the mortise and trochlea of the talus influences load characteristics.5,7,39,41,80 Reports of whole ankle contact area vary from 1.5 to 9.4 cm2 depending on load and ankle position.90 The tibiotalar area, however, accounts for only approximately 7 cm.2,78 Controversies exist about changes in the contact area as a function of flexion position5,7,41 that may be attributed to differences in load, position, and measurement technique.32 Calhoun et al7 found that contact surface area increased from plantar flexion to dorsiflexion and that force per unit area decreased proportionately. They observed also that the medial and lateral facets had greatest contact with the malleoli in dorsiflexion. In another study, using a dynamic model, progressive lateral loading with concomitant medial unloading was observed during dorsiflexion and associated external rotation.46
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Anatomy and biomechanics of the ankle and foot
Ground reaction and gravitational, ligament, and muscle forces produce a mixture of three-dimensional compressive, shear, and torsional loads in the ankle joint. Therefore, one may easily assume that force may not necessarily be directly perpendicular to the bone-implant interface but more angular. This introduces shear forces in addition to those of direct compression.
GROUND REACTION FORCES AND PRESSURE DISTRIBUTION Whenever the foot is in contact with the ground, forces act from the ground onto the foot and vice versa. These ground reaction forces are resultant forces that correspond to the movement of the center of mass and gravity. Typically subdivided into impact and active forces, ground reaction forces are determined by movement of the various segments involved in the locomotion process. Among the axes of the xyz coordinate system, they can be divided into the vertical, anteroposterior, and mediolateral force. Different for various activities, ground reaction forces can easily exceed body weight several times.56 In normal walking the vertical ground reactive force shows a typical two-peak active force pattern in a level around the body weight,58 the first peak associated with deceleration and the second with acceleration. In running at a speed of 4 m/s, the vertical component of the ground reaction force typically shows a single peak that increases into about two to three times body weight.56,58 As integral quantities, the ground reaction forces are limited in providing information on local phenomena, especially those specific to the foot. Pressure distribution measurement over the whole contact area of the foot sole provides more accurate information. Ground reaction forces and plantar pressure distribution can typically be measured either by the Kistler force plate technique (piezoelectric elements, as in the case of the classic motion analysis) or by computerized pedobarography systems (Fig. 8b.2). In the pedobarography (plates or insoles equipment, static or dynamic measurement) many hundreds of small force plates or sensors measure the force of the plantar aspect of the foot perpendicular to the surface.56,57,82,86 Compared with the Kistler plate technique, pedobarography pressure distribution sensors are better suited to provide more local information. Pressure distribution sensors are used in the form of insoles to assess foot-specific problems within the shoe, as in diabetic patients,20 or in the form of plates to assess postoperative outcome after orthopedic treatment, as in fracture reduction,81 total ankle replacement,28,82 tendon rupture repair,86 or fusion.14
SHOE CONSIDERATIONS The shoe’s main function is to protect the foot sole from the hazards of the environment and furthermore to facilitate running, to stabilize and treat foot deformities, and to serve as symbol in the society and fashion world (Fig. 8b.4). Without shoes, the foot has a natural ability to allow for torsional motion between the hind- and forefoot. Shoes often have torsional stiffness that decreases this physiologic movement. Studies have suggested that low torsional stiffness is advantageous, especially
Figure 8b.4 Picture of a normal shoe (Küzli AG, Schuhfabrik, Windisch, Switzerland).
for movement involving landing on the forefoot as is typical in volleyball or basketball.75,77 It is believed, however, that excessive cushioning found in modern shoewear prevents appropriate sensory feedback and results in a “pseudo-neurotropic” effect in running.65 The sensibility potential of the foot sole is the main reason that professional gymnasts and some dancers perform with no shoes or minimally shod feet. Stacoff and Lüthi76 reported that shoewear has been recorded as a source of injury since the early Greeks. Having been the norm in ancient times, barefoot running received international attention with Zola Budd’s 3000-m Olympics participation in 1984 (www.runningbarefoot.org). During barefoot running, the least amount of pronation and therefore injuries occur.75 Lysholm and Wiklander40 showed in 60 runners with 55 injuries within 1 year that shoe and surface problems were the primary sources of injury. Considering that impact forces are the critical variable in the pathophysiology of sports-related pain and injury,51 however, cushioning and shock absorption in sport shoes protect athletes and military recruits from overload injuries.15,49,72 By influencing impact loads, shoe material properties affect exposure to injury, as in cases of intraarticular cartilage damage and osteoarthritis.60,88,89 Excessive ankle joint eversion has been typically associated with the development of overuse injuries in locomotion.10,18,91 Subjects with injuries typically have foot eversion movement that is about 2 to 4 degrees greater than that of those with no injuries. Further, it has been suggested that a combination of excessive ankle joint eversion and substantial movement transfer of foot eversion into internal tibial rotation is a good predictor of the development of overuse injuries, especially in the knee.25,26 It has been proposed that movement transfer between foot eversion and tibial rotation is small for subjects with low arches and high for those with high arches.53 Consequently, subjects with high arches and excessive ankle joint eversion are more susceptible to overuse injuries. Ankle joint eversion is substantially influenced by shoes. Differences in ankle joint eversion for a subject using different running shoes are considerable. It is easily possible that the
Chapter 8b
maximal ankle joint eversion movement is 31 degrees for one and 12 degrees for another running shoe.52 Although medial support in a shoe may provide comfort and increased stability to the foot and leg and may reduce maximal ankle joint eversion, it may also increase internal rotation of the tibia. It is assumed that this change is associated with an increased inclination of the subtalar joint axis.53
12. 13. 14.
15.
16.
SHOE INSERTS AND ARCH SUPPORTS Shoe inserts and foot arch supports are often used successfully in the conservative treatment and prevention of occupational and sports injuries. They limit overuse of the foot structures, increase foot-leg stability, and/or change foot function. The prescription of these aids is typically based on the clinical expertise of the physician, plantar pressure distribution measurement (pedobarography), and plaster cast analysis or other moldings. Many problems are treated successfully with these strategies. Possible indications include tibialis posterior tendon dysfunction (stage I/II), medial ankle instability, plantar fascitis, and forefoot metatarsal collapse, among others. In most applications, however, the mechanical functioning of such orthoses is not well understood. In a recent biomechanical study involving lower extremity kinematic, kinetic, and electromyographic analysis, Mundermann et al49 showed the importance of comfort in foot orthoses. They concluded that evaluations of foot orthoses using comfort reflect not only subjective perceptions but also differences in functional biomechanical variables. Prescription of inserts and/or orthotics is a difficult task, however, and the correlation of clinical, design, and biomechanical variables is not well understood.55 Further research is needed to develop new measurement methods and to improve the functional-mechanical understanding of shoe inserts and arch supporting orthoses.
17.
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22. 23. 24. 25. 26. 27.
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CHAPTER
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Foot and Ankle Disorders in the Workplace Ross Taylor and G. James Sammarco
Workplace injuries of the foot and ankle represent a unique set of challenges within occupational medicine. The average adult takes approximately 7500 steps per foot in the course of an average day. The foot may be subject to forces in excess of twice body weight during routine activities. The workplace is even more demanding with requirements for ambulation on uneven surfaces, balancing on scaffolds, ladder climbing, and carrying heavy loads commonplace. Although the foot and ankle are supremely adapted to perform these functions, injuries may make these routine occupational activities impossible. Furthermore, underlying systemic conditions such as vascular disease, diabetes, obesity, and tobacco abuse frequently complicate the lower extremity injury or disease process and compound diagnostic and treatment dilemmas. Successful treatment begins with timely and accurate diagnosis. This requires not only skilled history taking but also a solid fund of anatomic knowledge. An understanding of the multitude of pathologic entities that affect the foot and ankle is a prerequisite. The occupational medicine practitioner must rely on this understanding to not only arrive at a working diagnosis but to determine the contribution of nonoccupational factors in the worker’s disease process. Once diagnosis has been established, expeditious treatment is of paramount importance. Whenever possible, the worker should be returned to modified duty during the rehabilitation process to minimize the psychosocial impact of occupational impairment. It is hoped that the reader may take away from this chapter an understanding of the broad spectrum of injuries to the foot and ankle incurred in the workplace setting. All too often a swollen and painful foot with negative radiographs is dismissed as a “sprain.” Only when the patient fails to improve in a reasonable period of time are additional possibilities considered. This leads to an untold waste of human resources and is often avoidable were the treating practitioners more thorough in their approach to injuries of the foot and ankle. This chapter is intended to serve as a foundation of knowledge regarding workplace injuries to the foot and ankle upon which successful diagnosis, treatment, and return to work can be efficiently executed.
EPIDEMIOLOGY The Bureau of Labor Statistics data indicate a total of 1.3 million injuries and illnesses required recuperation away from work beyond the day of injury in private industry in 2003.25 Conditions of the foot or ankle constituted approximately 125,000 of these injuries or approximately 9.5%. Those involved in occupations
related to trade, transportation, and utilities demonstrate the highest number of foot and toe injuries, comprising 35% of all foot and toe injuries recorded. Construction constitutes the second most represented occupational category, recording nearly 16% of foot or toe injuries. Sprains and strains were the most common type of injury of the ankle, constituting almost 70% of all ankle injuries. On the other hand, fractures are the most common nature of injury recorded in the foot or toes, comprising 26% of such injuries. The most typical event leading to injury was falling to a lower level for ankle injuries (20%) versus contact with objects for foot injuries (86%). A contributing source of injury is noted to be floors, walkways, or ground surfaces most commonly for both foot (20%) and ankle (40%) injuries but was more commonly found to be parts and materials (23%) for toe injuries. The median number of days of work missed per injury of the foot was seven days and for toe injuries, six days.
APPROACH TO THE PATIENT WITH WORK-RELATED FOOT AND ANKLE INJURY The first and perhaps most important step in returning the injured worker to their preinjury status when possible is prompt and accurate diagnosis. This is all too evident in cases in which the initial diagnosis is incomplete or inaccurate, leading to the initiation of incorrect or inadequate treatment. Subsequently, physical therapy may be initiated when immobilization is more appropriate or vice versa. The result of failure at the diagnosis level is not only a disgruntled worker but also increased expenses related to multiple referrals and time away from work. Accurate diagnosis begins with a thoughtful history. Often, the history is straightforward and that of traumatic injury. For instance, a fall from a height with sudden onset of heel or leg pain may suggest a calcaneus or distal tibia fracture. Ankle sprain or fracture often occurs when the ankle is forcibly rolled in inversion. Twisting of the ankle in external rotation suggests high ankle sprain or ankle fracture. Midfoot fracturedislocation may occur with a crushing mechanism to the foot, such as when heavy machinery rolls onto the foot or a large object is dropped directly onto the foot. Metatarsal or toe fractures can result when such a force is applied across the unprotected forefoot. Hyperdorsiflexion of the toes may result in injury to the plantar plate or cartilage of the hallux metatarsophalangeal (MTP) joint. Certainly, traumatic injury simplifies history taking. When the worker gives a history of onset of pain during routine activities, the differential diagnosis expands dramatically and the line between work-related injury and a degenerative or inflammatory disorder is less than distinct. More controversial is the role of repetitive overuse in the work-related injury. Diseases such as plantar fasciitis, hallux valgus, tarsal tunnel syndrome, interdigital neuroma, lesser toe deformities, adult acquired flatfoot, and osteoarthritis may present in the workplace. Guyton et al9 applied Koch’s postulates to examine the possible relationship between cumulative industrial trauma and causation of these seven disorders but found no association. Nonetheless, these are important disease entities that may be perceived as initiated by work-related activities. In the interest of confining the scope of this chapter to injuries of less controversial etiology, these processes are excluded from this chapter.
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Examination of the foot and ankle begins with observation of the patient in the standing position whenever possible. Overall alignment of the foot and ankle should be noted as well as any asymmetry between sides. Swelling, edema, and ecchymosis should be noted at this time, as well as any lacerations or obvious abrasions. The position of the foot or ankle may provide insight into the potential for injury to various structures. For instance, accentuation of the longitudinal arch of the foot (cavus foot) predisposes the worker to injuries over the lateral side of the foot and ankle such as ankle sprain, peroneal tendon tear, or fracture of the base of the fifth metatarsal. A flattened arch may suggest medial ankle sprain or injury to the posterior tibial tendon. Inspection of gait is fundamental as well, primarily to note the presence or absence of shortening of stance (antalgia) on the affected side. Careful range-of-motion assessment of the ankle, hindfoot, midfoot, and forefoot joints should be performed with special attention to any limitations of motion that may call attention to injury of each respective joint or associated muscle group. Localization of pathology is facilitated through palpation of the easily appreciated bony and tendonous structures of the foot and ankle. Thorough neurovascular examination is essential. The practitioner must resist the temptation to rely solely on history and physical examination even when the diagnosis seems obvious. Quality weight-bearing radiographs in the anteroposterior (AP), lateral, and mortise planes are standard for evaluation of the ankle. Radiographic examination of the foot should consist of AP, lateral, and oblique projections. When thorough history, examination, and standard radiographs fail to yield a diagnosis, specialized radiographic views may be helpful. Stress views, magnetic resonance imaging (MRI), computed tomography (CT), and radionuclide studies are all powerful tools when applied in the appropriate setting.
external fixation and delayed open reduction and internal fixation (ORIF). Complications after treatment are common and include full thickness skin loss, infection, and posttraumatic arthritis. McFerran et al13 reported a major complication rate of 42% after operative treatment of severe tibial pilon fractures. Long-term impairment is common and is usually due to pain and stiffness secondary to posttraumatic arthritis.
Ankle fractures Ankle fractures are typically the result of sudden twisting, inversion, or eversion of the ankle. Immediate onset of pain and swelling usually ensues. Depending on the severity of the injury, weight bearing may be impossible. Examination reveals swelling, tenderness, and ecchymosis about the ankle. These injuries vary considerably with respect to severity, treatment, convalescence, and potential for long-term impairment. Isolated fractures of the distal fibula are the most common ankle fractures. Unless open or widely displaced, these relatively low-energy injuries are amenable to closed treatment. Closed treatment requires four to six weeks of non–weight bearing in a short leg cast followed by an additional four to six weeks of weight bearing in a removable cast. Once weight bearing is begun, physical therapy is initiated, focusing on strengthening, range of motion, and edema reduction. Work-specific therapy may begin in a soft or lace-up ankle brace once resisted ankle eversion strength cannot be overcome by the examiners hand (Fig. 8c.1).
OVERVIEW OF WORKPLACE INJURIES Ankle Five percent of all work-related injuries requiring time away from work in 2003 involved in the ankle.25 This section presents an overview of workplace ankle injuries divided into two major subsections, the first devoted to fractures and the second to sprains. Of course, injuries to the ankle are seldom this black and white. Included in the section on ankle fractures is a section on tibial pilon fractures. Although not ankle fractures per se, tibial pilon fractures involve and profoundly affect the ankle and are therefore included. The section on ankle sprain includes a discussion of fractures and other pathology that may present similar to ankle sprains, so that the reader may keep these injuries in mind when evaluating a seemingly straightforward ankle sprain.
Fractures about the ankle Tibial pilon fractures Fractures involving the distal weightbearing articular portion of the tibia are termed tibial pilon fractures. These fractures represent high-energy injuries and occur most commonly after a fall or motor vehicle crash. Not only are these fractures frequently comminuted, but they represent severe soft tissue injury to the ankle as well. These injuries are seldom amenable to closed treatment and often require immediate
Figure 8c.1 Examination of ankle evertor strength. The patient is asked to evert the ankle against resistance.
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At this point, part-time light duty work may begin. Return to unrestricted duty may take three to four months after injury. Maximum medical improvement is typically reached within six months of injury. Isolated fractures of the medial malleolus are less common. Unlike isolated fractures of the lateral malleolus, these injuries are typically displaced and relatively unstable. When combined with a fracture of the proximal fibula, this injury represents a highly unstable injury pattern with rupture of the syndesmotic membrane (Massoneuve fracture). Nonetheless, if nondisplaced and stable, they may be treated closed using a similar protocol as outlined for isolated fractures of the lateral malleolus. More commonly, these injuries require ORIF. After ORIF, a six to twelve week period of short leg casting with non–weight-bearing restriction is instituted until healing has occurred as determined by lack of tenderness and bridging bone on radiographs. A six week course of protected weight bearing is combined with physical therapy focusing on strengthening, range of motion, and edema reduction. Work-specific therapy may begin in a soft or lace-up ankle brace once resisted ankle eversion strength cannot be overcome by the examiners’ hand. At this point, parttime light duty work may begin. Return to unrestricted duty may take six months or more after injury. Maximum medical improvement may not be achieved for nine to twelve months after injury. Often, medial and lateral malleolar fractures occur in combination, creating an unstable bimalleolar ankle fracture. Fracture of the posterior articular surface of the distal tibia in association with lateral, medial, or bimalleolar fracture is not uncommon as well. Bimalleolar and trimalleolar ankle fractures are almost always unstable and may even be open. Immediate closed reduction is performed under conscious sedation followed by emergent ORIF for open fractures or ORIF within the first few days of injury for closed fractures. Syndesmotic fixation may be required if the distal fibula fracture occurs more than 3.5 cm above the level of the ankle joint. The temptation to rely on internal fixation alone for fracture stability is dangerous. Short leg casting and non–weight-bearing restriction for eight to twelve weeks is required while the fractures heal. Syndesmotic screws are removed before the institution of weight bearing at approximately eight weeks after surgery. Although the rehabilitation phase is similar to that after ORIF of isolated malleolar fractures, prolonged pain and stiffness is common. Engelberg et al8 noted residual physical effects, including pain and stiffness, for up to 20 months after injury. Unfortunately, posttraumatic arthritis occurs in as many as 14% of ankle fractures, often beginning within two years of the injury.12 Persistent symptoms of pain, stiffness, and swelling beyond the typical course should prompt suspicion that posttraumatic arthritis is imminent. Examination usually demonstrates persistent ankle swelling, tenderness, and decreased range of motion. Weight-bearing radiographs may show joint space narrowing, osteophyte formation, and subchondral collapse. Bracing in an ankle foot orthosis, oral antiinflammatory medications, and a single intraarticular corticosteroid injection may be beneficial. Ultimately, surgical intervention may be required. Although ankle arthroscopy has a limited role, it may be helpful in osteophyte excision. Ankle arthrodesis is often required. Workers who do progress to posttraumatic arthritis may be
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unable to return to physically demanding occupations especially after ankle fusion.
Ankle sprain Acute inversion injury of the ankle may occur with minimal energy such as when handling heavy objects on an uneven surface such as a ramp or when stepping on an unexpected object on the floor. Higher energy ankle sprains may occur when the worker unloads from a higher level such as a truck cab or bed onto an uneven or unstable surface. Regardless of the mechanism, disruption of one or more of the lateral ankle ligaments occurs, resulting in pain and often impressive swelling over the anterolateral aspect of the ankle. Weight bearing is often but not always limited secondary to pain. Grading of ankle sprain is clinical with an anatomic basis. The clinical hallmark of grade I ankle sprain is isolated tenderness over the anterolateral aspect of the ankle. Range of motion of the ankle and hindfoot is usually limited by pain and swelling. The patient is typically able to bear weight, although with discomfort. This injury represents a partial tear of the anterior talofibular ligament. Grade II ankle sprain is suggested by pain prohibitive of weight bearing after the acute inversion injury. Tenderness is still localized to the anterolateral ankle. Complete disruption of the anterior talofibular ligament is likely to have occurred at this stage. Finally, disruption of both the anterior talofibular ligament and calcaneofibular ligament occurs in grade III sprain. Examination reveals tenderness both laterally and medially along the deltoid ligament and is often accompanied by massive swelling. Radiographs of both the ankle and foot should be obtained to rule out fracture. Treatment is the same initially for all grades of sprain. Immobilization, either in an ankle stirrup splint or a removable fracture boot, is combined with ice, compression, and elevation. This is conveniently summarized in the pneumonic RICE: rest, ice, compression, and elevation. Although pain is often prohibitive of weight bearing, ambulation may be encouraged in a removable fracture boot with the aid of crutches. Physical therapy should be initiated as soon as possible. Initial modalities should be aimed at edema reduction including elevation, inflatable foot pump, and active range of motion in a whirlpool. Within one week of injury, strengthening exercises of the peroneal muscles and proprioceptive training are initiated. Once the patient demonstrates return of peroneal function such that ankle eversion strength cannot be overcome by the examiner’s hand, they are graduated to a lace-up ankle brace with Velcro inversionresistant straps such as an ASO brace (Medical Specialties, Inc., Charlotte, NC, USA). Discontinuation of immobilization and physical therapy before this endpoint is reached predisposes the patient to risk of recurrent sprain and chronic ankle instability. Anticipated return to work depends on the grade of injury. Generally, patients with all grades of ankle sprain may be returned to work at the sedentary level within one to two weeks of injury. Advancement to full duty should be withheld until peroneal muscle strength, swelling, and range of motion are within 90% of the opposite side. This may take as little as four weeks for grade I sprains and as long as eight weeks for grade III sprains.
Persistently painful ankle sprain Unfortunately, as many as 20% to 40% of patients who sustain a grade III ankle sprain
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Figure 8c.2 Lateral radiograph of the ankle showing abnormal anterior translation of talus with anteriorly applied stress.
experience continued pain and stiffness beyond eight weeks postinjury. Although this is most often due to inadequate rehabilitation, other etiologies must be considered, including ankle instability, tears or tendonitis of the peroneal tendons, impingement lesions, osteochondral lesions of the talus, and occult fractures.
Ankle instability Instability of the ankle is not uncommon after ankle sprain. Ankle instability may be functional or mechanical; in both types the patient may complain of sudden giving way of the ankle as it rolls into inversion on uneven or unstable surfaces. Mechanical instability, unlike functional instability, may be readily demonstrated by examination by a positive anterior drawer test and confirmed by positive stress radiographs (Figs. 8c.2 and 8c.3). Regardless of the type of ankle instability, the response is usually favorable to aggressive physical therapy emphasizing peroneal muscle strengthening and proprioceptive training. If symptoms and findings persist, surgical reconstruction of the lateral ankle ligaments may be indicated. Return to full duty at the heavy demand capacity may require 12 to 16 weeks, until which the worker may benefit from continued proprioceptive training and peroneal strengthening.
Tear of peroneus longus or brevis tendon The peroneus longus and brevis tendons are important dynamic stabilizers of the ankle. Originating from the fibula and interosseous membrane, the peroneus longus and brevis muscles give rise to their respective tendons above the ankle joint. Sitting anterior to the longus at the level of the ankle joint, the peroneus brevis is cup shaped in cross-section and cradles the peroneus longus tendon posteriorly as they are redirected anteriorly around the tip of the distal fibula. Both tendons are held firmly in a groove in the posterior fibula distally by the superior and inferior peroneal retinaculum. At this level the peroneal tendons are susceptible to either tearing or subluxation out of the fibular groove with failure of the peroneal retinaculum. The exact incidence of peroneal tendon tears or subluxation with ankle sprain is speculative.20 Most tears are longitudinal and probably heal with treatment of the sprain.
Figure 8c.3 Anteroposterior radiograph of the ankle showing abnormal varus angulation of the talus with medialward stress.
A tear of one or more of the peroneal tendons should be suspected if lateral ankle pain persists beyond the expected course of improvement for ankle sprains. Typically, these patients demonstrate a varus heel and high arch. Tenderness is often greatest along the course of these tendons, particularly posterior to the tip of the distal fibula when the peroneus brevis is involved and in the soft spot just proximal to the base of the fifth metatarsal about the plantar lateral midfoot when the peroneus longus is involved.18 MRI examination usually confirms the diagnosis. These patients often have residual instability of the ankle and deserve an additional six week course of physical therapy devoted to strengthening of the peroneus brevis and longus tendons. Surgical repair is indicated if conservative treatment fails. Simultaneous surgical treatment of ankle instability may be necessary if stress radiographs are positive. The return to work protocol is similar to that after lateral ankle ligament reconstruction. Subluxation or dislocation of the peroneal tendons may be diagnosed acutely. The examiner has the patient dorsiflex the ankle against resistance and a palpable pop may be elicited over the peroneal tendons (Fig. 8c.4). Overt dislocation may be seen as an abnormal prominence of these tendons coursing over rather than behind the lateral malleolus (Fig. 8c.5). A six week course of casting the ankle in the inverted position with a felt pad posterior to the lateral malleolus is often successful if the condition is discovered and treated early. Delayed presentation
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Figure 8c.4 The examiner has the patient dorsiflex the ankle against resistance and a palpable pop may be elicited over the peroneal tendons (arrow).
Figure 8c.5 Overt dislocation may be seen as an abnormal prominence of the peroneal tendons coursing over rather than behind the lateral malleolus (arrow).
of this problem often requires surgical reconstruction of the peroneal retinaculum and deepening of the peroneal groove.
ankle sprains.1 That said, not all osteochondral lesions of the talus are due to trauma. Canale and Kelly3 noted that only 67% of medial talar dome lesions are associated with injury. Tenderness is usually nonspecific but may be greatest over the dome of the talus when the ankle is hyperplantarflexed. These lesions may be staged by radiographic appearance using the Berndt and Harty classification (Table 8c.1).1 Stage I or II lesions usually respond to an initial period of non–weight bearing with cast immobilization, followed by progressive weight bearing and mobilization to full weight bearing within 12 to 16 weeks. Failure of nonsurgical treatment or advanced stage III or IV lesions may require surgical management.
Impingement lesion Persistent anterolateral ankle pain in the absence of specific findings on examination and MRI should prompt suspicion of an anterolateral ankle impingement lesion. Due to single or repeated ankle sprains, hypertrophy of the anterior tibiofibular or talofibular ligament may occur, resulting in a painful pinching sensation over the front of the ankle with dorsiflexion as this tissue subluxes into and out of the ankle joint. Diagnosis may be confirmed if pain resolves with sterile saline injection into the ankle joint. This syndrome commonly resolves with rest as edema around the ankle subsides. Nonetheless, persistence of this problem may result in the need for arthroscopic debridement.
Osteochondral lesion of the talus Injury to the cartilage and subchondral bone of the talus occurs in as many as 6.7% of
Occult fracture Fractures of the anterior process of the calcaneus and injuries to the posterior process of the talus may be overlooked on initial examination and radiographs after inversion injury to the ankle. Fracture of the anterior process of
Table 8c.1 Berndt and Harty classification of osteochondral lesions of the talus, radiographic appearance, and recommended treatment options Berndt and Harty stage
Radiographic appearance
Treatment options
I
Subchondral bone compression
II
Partially detached osteochondral fragment
III
Completely detached nondisplaced osteochondral fragment
IV
Displaced osteochondral fragment (loose body)
Non–weight bearing in short leg cast for 6 weeks Surgery reserved for persistent symptoms Non–weight bearing in short leg cast for 6 weeks Surgery reserved for persistent symptoms Surgical treatment: either excision, drilling, and curettage or internal fixation Osteochondral autografting Surgical treatment: either excision, drilling, and curettage or internal fixation Osteochondral autografting
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the calcaneus may be detected with plain radiographs (Fig. 8c.6) or CT (Fig. 8c.7). If detected acutely, anterior process of the calcaneus fractures are best treated non–weight bearing in a removable cast, with institution of range-of-motion and strengthening exercises beginning 5 to 7 days after injury. ORIF may be required for large displaced fractures propagating through the calcaneocuboid or subtalar joints. Delayed presentation is common and is best treated with excision of the fragment with or without subtalar or talonavicular arthrodesis. These fractures may require 2 to 3 months for healing, at which point physical therapy may begin. Paulos et al15 noted that 17 of 20 posterior processes of the talus fractures (Shepherd’s fractures) after inversion injuries were missed. Confusion arises from the frequent presence of an accessory ossicle originating from the posterior process of the talus (os trigonum). Fracture may occur either through the synchondrosis between the os trigonum and posterior talus or through the posterior process itself. Examination reveals posterior ankle pain on forced plantarflexion of the ankle. CT, technetium bone scan, or MRI are helpful when confusion regarding diagnosis exists. Acute injuries are treated in a short leg walking cast for 4 to 6 weeks until fracture union occurs or symptoms resolve. If pain persists or if these injuries are discovered late, excision after diagnostic injection is recommended. Figure 8c.6 Lateral radiograph showing anterior process of the calcaneus fracture.
FOOT Almost 5% of all work-related injuries requiring time away from work in 2003 involved in the foot or toes.25 Like the section on ankle injuries, this section is divided into sections on fractures and on sprains and dislocations. Three sections are also included relating to nerve injuries, chronic regional pain syndrome, and crush injuries. The reader must keep in mind that although these topics are all individualized to facilitate discussion, they seldom occur in isolation. For instance, sprains or dislocation of the tarsometatarsal (TMT) joints are usually accompanied by fractures of one or more metatarsal or tarsal bones, and these injuries must be considered together. Nerve injuries are discussed individually but commonly coexist with significant disruptions to the major bony or ligamentous structures of the foot. This section clarifies these relationships whenever possible.
Fractures of the foot This section provides an overview of work-related fractures of the foot, including fractures of the calcaneus, talus, midtarsal bones of the midfoot, metatarsals, sesamoids, and the phalanges of the toes.
Calcaneus fracture In 1916, Cotton4 commented, “the man
Figure 8c.7 Computed tomography confirming anterior process of the calcaneus fracture.
who breaks his heelbone is done.” Fortunately, advances in operative technique and improved understanding of operative indications have since improved this outlook. Nonetheless, these remain one of the most challenging injuries to treat in the workers’ compensation population. Calcaneus fractures are almost always the result of a highenergy crushing mechanism such as a fall from a height or motor vehicle crash. Ipsilateral fractures of the medial malleolus, tibial plateau, or lumbar spine are commonplace. These patients must
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X-RAY
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Figure 8c.8 Radiograph showing the tuber angle of Böhler (From Borrelli J Jr, Torzilli PA, Grigene R, Helfet DL: Effect of impact load on articular cartilage: development of an intraarticular fracture model. J Orthop Trauma 11(5):319-326, 1997, and from Sanders R: J Bone Joint Surg Am 82(2):225-250, 2000.)
be approached as any potential multisystem trauma using standard trauma protocols; injuries to the head, chest, abdomen, spine, and pelvis take obvious precedence. Once more significant injuries have been ruled out, evaluation of the potential calcaneus fracture is performed. The patient usually complains of heel pain. Shortening and widening of the hindfoot may be seen. Tenderness, swelling, and ecchymosis are typical. Standard radiographic assessment of the ankle and foot should be performed. Lateral radiograph of the heel is useful to quantify the degree of calcaneal shortening by measurement of Böhler’s angle (Fig. 8c.8). Produced by the acute intersection of a line drawn parallel to the posterior tuberosity and another connecting the highest point on the anterior process to that of the posterior facet, a Böhler angle normally measures 20 to 40 degrees. Intraarticular step-off of the posterior facet may be visualized using Brodén’s view (Figs. 8c.9 and 8c.10). Axial projection is helpful to demonstrate widening and the degree of varus malalignment of the posterior tuberosity. Although radiographs are essential, the CT has become a vital assessment tool in evaluation of the calcaneus fracture. Semicoronal cuts through the posterior facet of the subtalar joint are obtained to ascertain the number of intraarticular fracture lines, the degree of intraarticular step-off, and the magnitude of varus malalignment. Immediate treatment is aimed at reducing the impact of soft tissue injury. Ideally, a Jone’s cotton compressive dressing and a posterior splint are applied. Admission to the hospital is recommended for ice, elevation, and observation for compartment syndrome. Compartment syndrome of the foot should always be suspected prompting low threshold for manometry and subsequent fasciotomies. Over the ensuing days, massive soft tissue swelling often develops with subsequent fracture blisters. Sterile decompression of nonhemorrhagic fracture blisters followed by application of nonadherent dressing should be
Figure 8c.9 Schematic drawings showing the technique for making Brodén’s views. With the patient supine, the x-ray cassette is placed under the leg and the ankle. The foot is in neutral flexion, with the leg internally rotated 30 to 40 degrees. (From Burdeaux BD Jr: Reduction of calcaneal fractures by the McReynolds medial approach technique and its experimental basis. Clin Orthop (177):87-103, 1983.)
Figure 8c.10 The x-ray beam is centered over the lateral malleolus and four radiographs are made, with the tube angled 40, 30, 20, and 10 degrees toward the head of the patient. (From Sanders R: J Bone Joint Surg Am 82(2):225-250, 2000.)
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Figure 8c.11 Classification of intraarticular calcaneal fractures according to Sanders et al: type I, nondisplaced fractures; type II, displaced fractures; and type III, comminuted fractures. (From Sanders R: J Orthop Trauma 6:254, 1992, and From Sanders R: J Bone Joint Surg Am 82(2):225-250, 2000.)
performed within the first week of injury. Definitive treatment depends on the integrity of the overlying soft tissues, presence of comorbid conditions, and classification of the fracture. Numerous classification systems for calcaneus fractures exist. Sanders et al23 devised a useful classification based on CT (Fig. 8c.11). This system is based on the number and position of displaced intraarticular fracture lines propagating into the widest segment of the posterior facet of the subtalar joint as seen on coronal CTs ● Type I fractures are defined by the absence of displacement regardless of the number of fracture lines. ● Type II represent displaced fractures defined by a single intraarticular fracture line. ● Type III fractures are displaced fractures defined by two intraarticular fracture lines. ● Type IV represent displaced fractures defined by three or more intraarticular fracture lines.
Each type is further divided into subtypes based on the location of the fracture lines. Classification of calcaneus fractures has become a vital tool in determining both the treatment and prognosis of these injuries. Closed treatment is indicated for Sanders type I fractures or when poor quality soft tissues prevent safe surgical incisions. Tobacco dependence, diabetes, and vascular disease may dictate closed treatment as well due to inordinately high potential for wound complications postoperatively.21 Early mobilization is preferable to prolonged immobilization. The patient is placed in a removable CAM walker boot and begins range-of-motion exercises of the ankle and foot within two weeks of the injury. Partial weight bearing may commence within six weeks of injury. The patient may be advanced to weight bear as tolerated, and within 12 weeks the boot may be discontinued altogether. The worker may then resume regular shoe wear, although a larger size may initially be required to accommodate heel widening.
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A full-length custom-molded or over-the-counter heel insert may provide additional comfort. A return to unrestricted duty may take up to six months. Surgical treatment is indicated for all open fractures. Sanders type II, III, and IV fractures generally benefit from surgical treatment; however, surgery is best deferred for 7 to 14 days until swelling has improved as indicated by circumferential skin wrinkling. Surgery through skin blisters should be avoided. Although ORIF is preferable whenever possible, primary subtalar arthrodesis may be indicated when two or more displaced intraarticular fracture lines extend into the subtalar joint, as in Sanders type IV fractures. Coughlin,5 Sanders,22 and others recommended a lower threshold for primary arthrodesis in workrelated calcaneus fractures. Coughlin5 demonstrated that return to work was delayed from an average of 6 months to 18 months, and treatment cost nearly doubled when ORIF failed and delayed subtalar arthrodesis was required. Unfortunately, 10% to 20% of patients who undergo ORIF of calcaneus fractures sustain postoperative complications such as delayed wound healing, infection, or sural neuritis.24 Wound complications may be twice as likely in tobacco users, and smoking cessation should be included in the treatment plan. As with all periarticular lower extremity fractures, posttraumatic arthritis is common. Coughlin5 reported that 7 of 16 intraarticular calcaneus fractures that underwent initial ORIF later required subtalar arthrodesis. Anterior impingement of the ankle; peroneal tendon subluxation, dislocation, or tendonitis; and chronic heel pain are all potential long-term sequelae of calcaneus fractures. After surgical treatment, the limb is immobilized in a fracture brace or short leg cast. Strict elevation is maintained for the initial four weeks after surgery to minimize edema and potential wound complications. After four weeks, physical therapy is begun at a frequency of three visits weekly. Range-of-motion, edema control, and strengthening exercises are performed. Partial weight bearing begins six weeks after surgery, and full weight bearing is usually delayed until 12 weeks after surgery. Immobilization and non–weight-bearing restriction is extended to at least eight weeks postoperatively after primary arthrodesis. Most patients may return to part-time sedentary work while maintaining strict elevation of the foot between four and six weeks after surgery. Progression to part-time light duty with hourly elevation breaks lasting 15 minutes may begin 12 weeks after surgery. Progress is usually gradual, and it may take four to six months before a full eight hour light duty shift is tolerable. A return to full duty may take a year or more. Chronic swelling and pain may limit tolerance to standing and walking. Uneven surfaces such as those encountered in the roofing and construction trades may be intolerable. Pain and stiffness may preclude occupations requiring ladder climbing and balancing on scaffolding. Unfortunately, workers within these professions are disproportionately represented among those who sustain calcaneus fractures. Work hardening and functional capacity evaluation are helpful to establish long-term work restrictions.
Talus fractures Fractures of the talus are divided into those of the neck, body, and posterior or lateral processes. Fractures of the neck of the talus are typically caused by dorsiflexion of the ankle beyond the physiologic range of motion, such as when the
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brake pedal foot is forced dorsally with the direct impact of a motor vehicle crash. The anterior aspect of the distal tibia acts as a wedge, splitting the talus at the neck. Fractures of the talar body occur from axial loading such as those seen in falls from a height. Lateral process fractures are avulsion injuries of the origin of the lateral talofibular ligament and generally occur with inversion injury. Posterior process fractures result from hyperplantarflexion and impingement between the posterior aspect of the tibia and the calcaneus. The injured worker with a talus fracture complains of pain about the ankle joint. Swelling, tenderness, and ecchymosis are usually present. Forced plantar flexion of the ankle reproduces pain when posterior process fractures are present. High-energy talar neck or body fractures may present with skin tenting or even extrusion of the talar body. Open injuries are commonplace. Coexisting injuries are common and must be ruled out using standard trauma protocols. Radiographic examination consists of AP, mortise, and lateral views of the ankle. Lateral, AP, and oblique views of the foot must be obtained. A talar neck view is helpful and is obtained by elevating the lateral border of the foot 15 degrees off the plantar placed x-ray cassette and canting the x-ray gantry 15 degrees away from the ankle toward the forefoot (Fig. 8c.12). CT has become the standard for evaluating talus fractures and may reveal fractures or comminution not appreciated on standard radiographs. Nondisplaced fractures of the neck or body of the talus may be treated closed. As soon as swelling permits, a short leg cast is applied. Non–weight-bearing restriction is enforced for six to eight weeks until healing occurs. Displaced talar neck or body fractures may be accompanied by dislocation of the ankle or subtalar joint and should undergo urgent reduction followed by
Figure 8c.12 Radiographic positioning for the oblique view of the talar neck, as described by Canale and Kelly.3 (From Fortin PT, Balazsy JE: Talus fractures: evaluation and treatment. J Am Acad Orthop Surg 9(2):114-127, 2001.)
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ORIF as soon as soft tissues permit. Open injuries require emergent irrigation, debridement, and stabilization. Immobilization in a short leg cast may be required for up to four months. After four months, the weight-bearing status is advanced to allow weight bearing as tolerated in a fracture boot. After cast removal, rangeof-motion and strengthening exercises as well as edema reduction techniques are performed three times weekly in physical therapy. Fractures of the posterior process are often difficult to distinguish from injury to the os trigonum. Fortunately, treatment is similar. If symptoms persist beyond a six week course of casting, excision of the symptomatic os trigonum or posterior process fragment after positive diagnostic injection is recommended. Nondisplaced fractures of the lateral process are under-diagnosed. If discovered, late excision may be required; otherwise they may be treated with a six week course of short leg casting with a non–weight-bearing restriction. Large displaced fragments may require ORIF, whereas comminuted fractures may benefit from excision. Long-term complications of talus fractures are common and include posttraumatic arthritis and avascular necrosis. Elgafy et al7 reported high rates of posttraumatic arthritis of the subtalar joint (53%) and ankle joints (25%) after fracture of the talus in a series of 60 talus fractures. Failure of conservative treatment may necessitate subtalar or ankle arthrodesis. Reported rates of avascular necrosis vary but may approach 100% of severely displaced fractures. Subchondral lucency of the dome of the talus on AP radiographs of the ankle occurring between six and ten weeks after fracture (Hawkins sign) is considered diagnostic of viability of the talar dome.10 Limitation of weight bearing using a patellar tendon bearing ankle foot orthosis may be required for up to a year while the talus revascularizes. Workers with conservatively treated fractures of the talus may return to sedentary duty within two to three weeks of injury. After surgical management, the requirement for strict elevation precludes return to sedentary work until four weeks postoperatively. Once full weight bearing is achieved, part-time light duty with frequent rest breaks may be initiated. Patients with conservatively treated talus fractures may be returned to full duty three to four months after injury, whereas those with displaced fractures treated surgically may require 6 to 12 months depending on the presence of avascular necrosis (AVN) or osteoarthritis. Work hardening, functional capacity evaluation, and even occupational change may be required.
Tarsal bones of the midfoot fractures The midtarsal bones are important in maintaining the geometry of the foot. They may be thought of as constructing two columns, medial and lateral. The medial column consists of the navicular proximally and the three cuneiforms distally. The cuboid constitutes the lateral column. The analogy to columns is important, because fractures of tarsal bones within either column tend to result in loss of pedal length either medially or laterally with profound effects on the shape and function of the foot. Crush fractures of the cuboid may result in lateral column shortening, midfoot abduction, and pes planus. Pes cavus may occur with shortening of the medial column, usually secondary to navicular fractures. Furthermore, fractures of the midfoot bones are usually intraarticular, and these injuries may result in posttraumatic arthritis. Often, midtarsal fractures are but one component of high-energy
crush injuries with coexisting skin compromise, nerve injury, or compartment syndrome. Once the soft tissues are stabilized, treatment of these injuries should focus on maintaining column geometry and articular congruity. Posttraumatic arthritis is common after these fractures, and highly comminuted fractures may require primary intertarsal arthrodesis. Return to work varies widely depending on the severity of the injury. Isolated nondisplaced fractures treated closed may be returned to sedentary duty almost immediately. A patient with injuries requiring ORIF or primary arthrodesis may expect a delay in returning to full unrestricted duty of three to six months.
Metatarsal fractures Metatarsal fractures may occur through either or both the base or shaft of the metatarsals. When one or more metatarsal base fractures are accompanied by midfoot tenderness, the diagnosis of TMT fracture dislocation must be entertained. TMT fracture dislocations are unstable injuries that often require operative stabilization; these are covered in the section pertaining to these injuries. On the contrary, isolated metatarsal fractures generally respond well to conservative treatment. The injured limb is initially elevated in a soft compressive dressing to control swelling. This is then changed to a hard-soled shoe or removable fracture boot for four to six weeks. Weight bearing to pain tolerance is permitted during this time. Sedentary work may be permitted until radiographic healing has occurred. Once healing is evident radiographically, the patient may begin part-time light duty. During this time, physical therapy is performed, aimed at edema reduction and strengthening. Residual forefoot pain is best treated with a semirigid custom foot orthotic. A return to heavy duty is usually possible within 8 to 12 weeks of injury. Certain metatarsal fractures require special attention. Displaced fractures of the first metatarsal require anatomic reduction. If anatomic reduction cannot be maintained, then operative stabilization may be required. Fractures of the proximal fifth metatarsal metadiaphyseal junction (Jones fracture) are important to recognize because these have a significant rate of nonunion (Figs. 8c.13 and 8c.14). These injuries are best treated with non–weight-bearing cast immobilization for 6 to 8 weeks. The rate of successful union with this treatment has been reported to be between 72% and 93%.17 Sesamoid fractures Fracture of the medial or lateral sesamoid bones of the foot may occur either acutely or in response to stress. Acute injuries are usually the result of sudden hyperdorsiflexion injury to the hallux MTP joint. This may result in transverse fracture more commonly of the medial sesamoid (Fig. 8c.15). Stress injuries are most common in athletes and dancers and usually demonstrate a stellate fracture pattern. Point tenderness is usually found directly beneath the involved sesamoid. Radiographic studies should include basic AP, lateral, and oblique projections of the foot. Specialized axial and oblique sesamoid views may also be helpful (Figs. 8c.16 and 8c.17). Radiographic studies may be somewhat confusing due to the high incidence of bipartite sesamoids (5-30%). MRI or technetium-labeled red blood cell radionuclide study may be useful when radiographs are nondiagnostic. Acute fractures deserve a six week course of non–weightbearing restriction in a short leg cast. The worker may then
Chapter 8c
Figure 8c.13 Anteroposterior radiograph of a typical acute Jones fracture (arrow). The fracture line is intraarticular and involves the fourth-fifth intermetatarsal articular facet. (From Rosenberg GA, Sferra JJ: J Am Acad Orthop Surg 8(5):332-338, 2000.)
Figure 8c.16 sesamoid.
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Sesamoid oblique view showing fracture of the medial
return to part-time light duty in a semirigid foot orthosis with relief under the affected sesamoid and a metatarsal bar. Although unrestricted duty may generally be resumed within three months, kneeling may prove especially difficult as it requires maximum dorsiflexion of the hallux MTP joint. Work hardening and physical therapy should focus specifically on the restoration of painless dorsiflexion of the great toe.
Phalangeal fractures Fractures of the toe phalanges are the most common osseous injury to the foot in the general population.6 Phalangeal fractures are best treated with closed reduction
Figure 8c.14 Lateral radiograph of a typical acute Jones fracture (arrow). The fracture line is intraarticular and involves the fourth-fifth intermetatarsal articular facet. (From Rosenberg GA, Sferra JJ: J Am Acad Orthop Surg 8(5):332-338, 2000.)
Figure 8c.15
Intraoperative photo showing medial sesamoid fracture.
Figure 8c.17 Sesamoid axial view showing lateral (A) and medial (B) sesamoids.
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under digital block anesthesia, followed by buddy taping to the adjacent medial toe. A hard-soled shoe is worn until cessation of pain, tenderness, and swelling herald fracture healing, usually within four weeks. The worker is then returned to regular duty with preventative measures such as steel-toed shoes in place. Unstable closed reductions that manifest as obvious toe deformity require percutaneous pinning. These patients need to remain non–weight bearing on the affected extremity until the pin is removed, usually around six weeks after injury. Displaced intraarticular fractures of the hallucal proximal phalanx may benefit from ORIF with a return to light duty between six and ten weeks after injury. Persistent swelling or pain should always be taken seriously, because it may belie fracture nonunion. This may be addressed with operative fixation and grafting. Residual disability is uncommon.
Sprains and dislocations Ligament injuries may occur about any joint in the foot, but most commonly occur about the TMT and the hallux MTP joints. Strong ligamentous attachments and highly congruent articulations, particularly about the TMT joint, may result in coexisting fractures when these joints are injured.
TMT joint injuries The TMT joint, also known as Lisfranc’s joint, is the stable articulation between the five metatarsal bases and the midtarsal bones (medial, middle and lateral cuneiforms, and the cuboid). The most important of these articulations is the second TMT joint. The second TMT joint is a stable mortise created proximally by the geometry of the three cuneiform bones. These bones create a three-sided notch into which sits the base of the second metatarsal (Fig. 8c.18). The second metatarsal is the only metatarsal to articulate with three tarsal bones and is anchored in its mortise by Lisfranc’s ligament. Lisfranc’s ligament originates from the plantar aspect of the medial cuneiform and extends to the base of the second metatarsal. Injury to this ligament has a destabilizing effect on the midfoot that may lead to deformity, dysfunction, and pain if not recognized and treated. Although motor vehicle crashes are the most common cause of injury to the TMT joint, these injuries are also frequently seen in the industrial setting. They may occur as a result of direct trauma such as a crush as seen in a forklift injury or as the result of a sudden twisting and axial loading of the plantar flexed foot. The Napoleonic era surgeon Lisfranc provided insight into the mechanism of injury by noting it to occur in cavalry with traumatic dismount from the stirrup. The severity of these injuries varies considerably. Mild sprains are characterized by mild midfoot tenderness and swelling. Radiographic appearance is normal. Minor sprains may be treated with rest, ice, and elevation followed by immobilization in a removable fracture boot with early institution of weight bearing. Sedentary work restriction is placed for four to six weeks or until tenderness has resolved. Unfortunately, these injuries are often underestimated in terms of severity or missed outright. Moderate and severe sprains are usually characterized by pain prohibitive of weight bearing. Examination reveals marked swelling, tenderness, and ecchymosis about the midfoot. Ecchymosis localized to the plantar aspect of the midfoot beneath the first TMT joint may be seen (Fig. 8c.19).
Figure 8c.18 (A) Anteroposterior view of the bony and ligamentous anatomy of tarsometatarsal joint complex I through V = metatarsal bones. (From Myerson MS: Fractures of the midfoot and forefoot. In MS Myerson, ed: Foot and ankle disorders. Philadelphia, 2000, W.B. Saunders, pp. 1265-1296.) (B) Coronal section through the metatarsal bases illustrating the Roman arch configuration. (From Lenczner EM, Waddell JP, Graham JD: Tarsal-metatarsal (Lisfranc) dislocation. J Trauma 14(12):1012-1020, 1974, and from Thompson MC, Mormino MA: Injury to the tarsometatarsal joint complex. J Am Acad Orthop Surg 11(4):260-267, 2003.)
Radiographic findings are often subtle, consisting of widening between the base of the second metatarsal and medial cuneiform. Widening of more than 2 mm compared with the opposite side is considered diagnostic of unstable injury. A fleck of bone may be seen in this interval on radiographs representing avulsion of the origin of Lisfranc’s ligament from the medial cuneiform. Disruption of normal continuity between the medial cortex of the second metatarsal base and middle cuneiform or between the medial base of the fourth metatarsal and cuboid are
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removal, so that work hardening may begin shortly thereafter. A custom semirigid foot orthosis is often beneficial. Although light duty may begin five months after injury, it may be six to nine months before a return to regular duty may occur. Unfortunately, posttraumatic arthritis is common after unstable injuries, particularly when these injuries are missed. Persistent midfoot pain, tenderness, and joint space narrowing are suggestive of posttraumatic arthritis. When rigid foot orthosis and oral and injected antiinflammatory medications fail, surgical arthrodesis of the midfoot may be required. Calder et al2 noted a poor outcome in 13 of 46 patients with unstable work-related TMT joint injuries. In this study, delay in diagnosis of more than six months and the presence of a workers’ compensation claim were associated with a poor outcome. Permanent change in occupation is often necessary, and a functional capacity evaluation may be useful in establishing recommendations for future employment.
Figure 8c.19 Ecchymosis localized to the plantar aspect of the midfoot beneath the first tarsometatarsal (TMT) joint as seen with TMT joint fracture dislocation.
also diagnostic of unstable injury. Comparison views of the opposite foot are helpful. Clinical signs and symptoms, even in the setting of negative comparison radiographs, warrant CT of the midfoot. Even when plain radiographs are normal, fractures of one or more metatarsal bases or their corresponding tarsal bones may be seen on CT belying an unstable injury to the TMT joint complex. Fracture dislocation of one or more metatarsal bases, the cuneiform, or cuboid bones is not uncommon. Soft tissue injury may be marked, with skin tenting or even skin penetration occurring. Compartment syndrome must always be suspected. Tense edema of the foot, paresthesias in the toes, and midfoot pain with flexion-extension of the toes are all supportive of the diagnosis of compartment syndrome. Threshold should be low for manometric examination of the foot and subsequent fasciotomies, as the sequelae of missed compartment syndrome are unacceptable and may include disabling deformity and neurologic injury. Treatment of an unstable TMT joint injury requires surgical stabilization. Minimally displaced injuries may be treated with closed reduction and internal fixation, whereas more severe and open injuries require ORIF. Transarticular fixation must be removed before weight bearing is resumed, usually between three and four months after surgery. Nonetheless, range-of-motion and strengthening exercises may be instituted before hardware
MTP joint injuries Injuries to the MTP joint are most common about the great toe. Popularized in the sports medicine literature as “turf toe,” hallux MTP joint injuries are not uncommon in the industrial setting. Typically occurring with hyperdorsiflexion of the hallux MTP joint, these injuries may result in both compression injuries to the dorsal articular cartilage of the first metatarsal head in addition to tensile damage to the MTP joint capsule structures. Osteochondral defect of the first metatarsal head; rupture of the plantar plate, collateral ligaments, or flexor hallucis brevis tendon; and bony injury to the sesamoids are all within the spectrum of injury to the hallux MTP joint. Mild injuries represent stretch injuries to the plantar joint capsule. Tenderness is isolated to the plantar and occasionally the dorsal aspects of the hallux MTP joint. Radiographs are typically negative. Acutely, rest, ice, and immobilization and antiinflammatory medications are helpful. Taping of the great toe should be instituted to limit extension of the MTP joint. Weight bearing is allowed in a wooden-soled shoe until tenderness resolves. Moderate to severe injuries represent complete disruption of the plantar plate of the hallux MTP joint. Fracture of either medial or lateral sesamoid or disassociation of the bipartite sesamoid may be present. Osteochondral injury to the dorsal head of the first metatarsal may coexist. Examination reveals tenderness, swelling, and ecchymosis about the hallux MTP joint. Pain occurs with any attempt at range of motion, and the hallux MTP joint may be unstable with dorsal translation. Radiographs are negative unless unreduced dislocation of the MTP joint, avulsion fracture of the base of the proximal phalanx, or sesamoid fracture disassociation are present. Rest, ice, immobilization, and antiinflammatory medications are helpful in the acute stage. Irreducible dislocation may require open reduction. As with mild injuries, protected weight bearing in a wooden-soled shoe and taping are instituted. Even with mild injuries, return to unrestricted or heavy work may take as long as six months. Initially, sedentary work may be initiated in a wooden-soled shoe. Once swelling and tenderness have resolved, the worker may return to light duty in a standard shoe containing a low-profile rigid foot orthosis with a Morton’s forefoot extension (Fig.18c.20). Return to unrestricted
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Figure 8c.20 Low-profile rigid foot orthosis with a Morton’s forefoot extension (Springlite Inc., Salt Lake City, UT, USA).
duty is delayed until full painless motion of the hallux MTP joint has returned as compared with the opposite side. Persistent pain after these injuries should not be dismissed. If symptoms continue beyond three months, MRI examination is warranted to detect either a stress fracture of the sesamoid or an osteochondral injury to the first metatarsal head. Stiffness and pain persisting six months beyond injury should prompt suspicion of posttraumatic arthritis. Posttraumatic arthritis of the hallux MTP joint, or hallux rigidus, is treated with antiinflammatory medications and a rigid foot orthosis with a Morton’s forefoot extension. Refractory pain may require surgical treatment. Dorsal cheilectomy is indicated if the joint space is largely preserved; hallux MTP arthrodesis is reserved for end-stage arthritis. Return to heavy labor is a reasonable goal after surgical management of hallux rigidus; however, a steel-toed shoe and a rigid orthotic with a Morton forefoot extension are advised. Injuries to the lesser MTP joints should not be discounted. Hyperdorsiflexion injury may result in rupture of the plantar plate with delayed claw toe deformity. Dorsal dislocation may require open reduction if unreducible. Acutely, immobilization in a Budin splint (Apex Foot Health Industries, Inc., Teaneck, NJ, USA) and buddy taping is helpful. The patient may be graduated to a full-length rigid insert with a metatarsal bar once swelling and tenderness have resolved.
Nerve injuries Peripheral nerve disorders are common sequelae of traumatic events in the lower extremity. Painful and hypersensitive areas of perineural scarring may occur either along a nerve (neuroma in continuity) or at a site of nerve transaction (stump neuroma). Adhesive neuralgia may affect a length of nerve in response to either injury or surgery. Delayed diagnosis of compartment syndrome may result in ischemic nerve damage. Given the lack of objective findings and the often disabling symptomatology associated with peripheral nerve lesions, these injuries represent formidable diagnostic and treatment challenges in any setting.
Typical complaints that should alert the practitioner to underlying nerve injury include numbness, burning pain, or hypersensitivity in the distribution of one or more sensory nerves of the foot. Percussion along an injured nerve with the examiners fingertip may reproduce descending paresthesias (Tinel’s sign). Thorough neurologic examination may uncover underlying radiculopathy or peripheral neuropathy predisposing to nerve injury.19 Peripheral nerve blocks are helpful in both localizing pathology and determining potential response to treatment. Electrodiagnostic studies should also be performed early to document the location and degree of nerve injury and to uncover contributing pathology such as radiculopathy or neuropathy. Treatment of peripheral nerve injuries in the acute setting involves direct surgical repair of transected essential motor nerves including the tibial and common peroneal nerves. Although primary repair of sensory nerves such as the distal superficial and deep peroneal nerves and the sural and saphenous nerves is controversial, clean lacerations may benefit from epineural suturing. Return of sensory function from the site of repair is gradual and may be followed by descending percussion sensitivity that is generally thought to proceed at 1 mm/day. Electrodiagnostic testing is indicated three months after repair to confirm recovery of nerve function. Stretch injuries such as those to the superficial peroneal nerve after inversion injury of the ankle are best managed in the acute stage by splinting the affected extremity in neutral alignment to minimize further nerve tension. Crush injuries should be monitored for compartment syndrome with a low threshold for compartment manometry and subsequent fasciotomies. All nerve injuries should also be treated with early initiation of nerve stabilizing medications such as gabapentin, followed by physical therapy desensitization techniques such as contrast baths, transcutaneous nerve stimulation, and range-of-motion exercises.16 Many optimally treated patients with peripheral nerve injuries progress to chronic neuralgia. Pharmacologic therapy should be initiated and may include topical agents such as lidocaine patches and capsaicin cream. Antiepileptic and antidepressant medications such as Neurontin and amitriptyline should be initiated at initially low dosages and may be titrated to effectiveness. Physical therapy desensitization techniques, including contrast baths, transcutaneous nerve stimulation, and range-of-motion exercises, are helpful as well. Finally, surgical management may benefit patients with welldefined nerve lesions who have failed all other treatment. Neuroma resection with stump burial is most effective in patients who respond favorably to diagnostic injection with local anesthetic. Adhesive neuralgia may respond to neurolysis with or without a vein-wrapping procedure. Patients with peripheral nerve lesions who fail conventional pharmacologic, physical therapy, and surgical treatment may benefit from application of an implanted peripheral nerve stimulator. In summary, treatment of peripheral nerve injuries involves a multimodality approach incorporating pharmacologic agents, physical therapy desensitization, and surgery. Treatment of associated pathology such as ligamentous disruption, fracture, or compartment syndrome is a prerequisite for successful treatment of peripheral nerve injuries. Nonetheless, these injuries remain among the most challenging conditions to treat for the occupational physician.
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Chronic regional pain syndrome Chronic regional pain syndrome may occur in response to either noxious or nonnoxious stimuli to the extremity. Chronic regional pain syndrome is divided into types I and II. Type I develops after an initial event that may or may not have been traumatic. Type II generally develops after nerve injury. Both types I and II result in pain, allodynia (painful response to nonpainful stimuli), and hyperalgesia often involving the entire distal extremity. Autonomic dysfunction is common and may manifest as color or temperature changes and hyperhydrosis. The involved extremity may appear cool and mottled or warm, erythematous, and swollen. Trophic changes may include a smooth shiny appearance to the skin with thickened or thinned toenails. Radiographs may show nonspecific osteopenia. A threephase, technetium-labeled, red blood cell radionuclide study may show nonspecific periarticular uptake on all phases. Early initiation of appropriate treatment is paramount to successful management of this challenging disorder. Physical therapy, medications, and regional anesthesia are all important therapeutic tools. Lee and Kirchner11 outlined a stepwise and sensible physical therapy protocol. Initial therapy focuses on mobilization and desensitization. Once the injured worker becomes tolerant of limb manipulation, flexibility and edema reduction techniques are used. Isotonic strengthening, stress loading, and aerobic conditioning are followed by vocational rehabilitation, work hardening, and functional capacity evaluation. Adjunctive medications include antidepressants such as amitriptyline and antiepileptics such as gabapentin. Regional anesthesia techniques may be an effective compliment to physical therapy and medications. Lumbar sympathetic blocks or combined somatic-sympathetic blocks may be helpful especially when combined with physical therapy.
Crush injury Crush injuries of the foot represent a subgroup of high-energy foot trauma resulting in both bony and soft tissue injury with far-reaching treatment and rehabilitation implications. The preponderance of these injuries in the industrial setting has been well documented.14 Crushing was responsible for 7.4% of all foot and toe injuries incurred in private industry in 2003.23 Management of these injuries begins with standard trauma protocols. Once life-threatening injuries have been ruled out, stabilization and assessment of the injured extremity commences. Neurovascular examination is followed by soft tissue evaluation. Compartment syndrome should be anticipated and early manometry performed, followed by fasciotomies of the foot if compartment pressures are elevated. Treatment requires aggressive surgical decontamination, debridement of nonviable tissues, bony stabilization, and early soft tissue coverage. Broad spectrum antibiotic coverage is required for open injuries. Unfortunately, long-term morbidity is common after crush injuries of the foot. Associated problems include deformity, stiffness, chronic neuralgia, posttraumatic arthritis, and chronic regional pain syndrome. The series of Myerson et al14 noted that only 46% of patients with crush injuries to the foot sustained a good outcome. Poor outcome was noted more commonly in those sustaining either chronic neuralgia or chronic regional pain syndrome.
RETURNING THE FOOT- AND ANKLE-INJURED WORKER TO WORK Correct and timely diagnosis is the first step in treatment of the worker with foot or ankle injury. Incorrect diagnosis may lead to unnecessary tests, inappropriate treatment, prolonged disability, and perceptions of malingering for secondary gain among the employer, insurance carriers, and physicians. It is hoped that the information within this chapter may guide the diagnostician in timely diagnosis. Nonetheless, even the most astute diagnostician may be confounded. Early referral to an orthopedic foot and ankle specialist may be beneficial when the diagnosis is less than clear. Once the diagnosis is established and treatment plans are in place, it is important to discuss with the injured worker an appropriate timetable for return to work. This includes a timetable for return to modified or part-time duty. The nurse case manager should establish whether modified duty is available. Obviously, acutely after severe injury or surgical treatment, strict elevation requirements make return to even sedentary duty impractical. Once the patient can tolerate short periods with the injured extremity in the dependent position, part-time sedentary duty should be instituted. This may be advanced to part-time light duty with hourly elevation breaks once weight bearing is no longer contraindicated. As range of motion, strength, and endurance improve through physical therapy, the work day may be elongated until the appropriate shift length is tolerable. Functional capacity evaluation may be useful at this point to delineate deficiencies in task-specific functions and guide subsequent work hardening. Work hardening may succeed in preparing the worker for his or her previous physical work capacity. If the worker fails to meet these expectations, an additional functional capacity evaluation or even an independent medical evaluation may be useful. Despite many advances in caring for foot and ankle injuries, return to work is not always possible at the injured worker’s previous occupational level. It is perhaps paradoxical and cruel that those most likely to sustain lower extremity impairment are those whose occupations are most dependent on lower extremity functions. For example, roofers and construction workers are among the trades most likely to sustain a fall from a height with a resulting lower extremity fracture. Many of these fractures are periarticular and may result in arthritis and joint stiffness even when optimally treated. It is easy to see how arthritis and joint stiffness may make balancing on uneven surfaces, climbing ladders, and negotiating scaffolding impossible. Even in the event of a highly motivated patient and optimal treatment, the return to a previous occupational level is not always feasible. Should return to the previous occupation be unlikely, this should be established with the patient as soon as possible.
CONCLUSION In general, the treatment of foot and ankle disorders incurred in the workplace is even more challenging than in the population at large. Workers frequently perform demanding tasks while standing and walking on often dynamic and uneven terrain.
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Their occupation may require prolonged standing and walking while carrying heavy objects. Furthermore, resting the injured extremity is often difficult even when not working due to the weight-bearing demands of everyday life. Because people’s livelihoods are often at stake, timely and accurate diagnosis becomes even more important. The successful diagnosis of the worker with a foot and ankle injury requires an understanding of the broad range of diagnostic possibilities in the foot and ankle. In addition to fractures, sprains, and dislocations, peripheral nerve and crush injuries are common about the foot and ankle in the industrial setting. A well-directed and comprehensive history and physical examination when combined with appropriate imaging studies usually yields a correct diagnosis. Once a clear diagnosis has emerged, a stepwise treatment plan may be implemented. Consideration of underlying medical conditions is an important consideration in devising a treatment strategy. The nurse case manager and physical therapist are integral treatment team members in executing the plan of care. Physical therapy, orthotics, functional capacity evaluations, and work hardening are all useful treatment tools in rehabilitating the worker as a final phase of treatment. Restoring an injured worker to the workplace is indeed a difficult and challenging endeavor. It is hoped this chapter may serve as a general guide to approaching the worker with a foot and ankle ailment and thus positively impact the diagnosis, treatment, and rehabilitation of these patients.
4. 5. 6. 7. 8.
9.
10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.
REFERENCES 1. 2. 3.
Berndt AL, Harty M: Transchondral fractures (osteochondritis desiccans) of the talus. J Bone Joint Surg 41A:988-1020, 1959. Calder JD, Whitehouse SL, Saxby TS: Results of isolated Lisfranc injuries and the effect of compensation claims. J Bone Joint Surg Br 86(4):527-530, 2004. Canale ST, Kelly FB Jr: Fractures of the neck of the talus: long-term evaluation of seventy-one cases. J Bone Joint Surg Am 60(2):143-156, 1978.
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Cotton FJ: Os calcis fracture. Ann Surg 64-80, 1916. Coughlin MJ: Calcaneal fractures in the industrial patient. Foot Ankle Int 21(11): 896-905, 2000. DeLee J: Surgery of the foot. In R Mann, ed: Fractures and dislocations of the foot. St. Louis, MO, 1980, C.V. Mosby, pp. 729-749. Elgafy H, Ebraheim NA, Tile M, Stephen D, Kase J: Fractures of the talus: experience of two level 1 trauma centers. Foot Ankle Int 21(12):1023-1029, 2000. Engelberg R, Martin DP, Agel J, Obremsky W, Coronado G, Swiontkowski MF: Musculoskeletal function assessment instrument: criterion and construct validity. J Orthop Res 14(2):182-192, 1996. Guyton GP, Mann RA, Kreiger LE, Mendel T, Kahan J: Cumulative industrial trauma as an etiology of seven common disorders in the foot and ankle: what is the evidence? Foot Ankle Int 21(12):1047-1056, 2000. Hawkins LG: Fractures of the neck of the talus. J Bone Joint Surg Am 52(5): 991-1002, 1970. Lee KJ, Kirchner JS: Complex regional pain syndrome and chronic pain management in the lower extremity. Foot Ankle Clin 7(2):409-419, 2002. Lindsjo U: Operative treatment of ankle fracture-dislocations: a follow-up study of 306/321 consecutive cases. Clin Orthop 199:28-38, 1985. McFerran MA, Smith SW, Boulas HJ, Schwartz HS: Complications encountered in the treatment of pilon fractures. J Orthop Trauma 6(2):195-200, 1992. Myerson MS, McGarvey WC, Henderson MR, Hakim J: Morbidity after crush injuries to the foot. J Orthop Trauma 8(4):343-349, 1994. Paulos LE, Johnson CL, Noyes FR: Posterior compartment fractures of the ankle: a commonly missed athletic injury. Am J Sports Med 11(6):439-443, 1983. Raikin SM: Nerve injuries to the foot and ankle in the industrial setting. Foot Ankle Clin 7(2):351-366, 2002. Rosenberg GA, Sferra JJ: Treatment strategies for acute fractures and nonunions of the proximal fifth metatarsal. J Am Acad Orthop Surg 8(5):332-338, 2000. Sammarco GJ: Peroneal tendon injuries. Orthop Clin North Am 25(1):135-145, 1994. Sammarco GJ, Chalk DE, Feibel JH: Tarsal tunnel syndrome and additional nerve lesions in the same limb. Foot Ankle 14(2):71-77, 1993. Sammarco GJ, DiRaimondo CV: Chronic peroneus brevis tendon lesions. Foot Ankle 9(4):163-170, 1989. Sanders R: Displaced intra-articular fractures of the calcaneus. J Bone Joint Surg Am 82(2):225-250, 2000. Sanders R: Intra-articular fractures of the calcaneus: present state of the art. J Orthop Trauma 6(2):252-265, 1992. Sanders R, Fortin P, Dipasquale T, Walling A: Operative treatment in 120 displaced intraarticular calcaneal fractures: results using a prognostic computed tomography scan classification. Clin Orthop 290:87-95, 1993. Sangeorzan BJ, Benirschke SK, Sanders R, Carr JB, Thordarson DB: The literature on calcaneal fractures is highly controversial. Foot Ankle Int 22(10):844-845, 2001. U.S. Bureau of Labor Statistics: Lost work time injuries and illnesses: characteristics and resulting days away from work. http://www.bls.gov/iif/home
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8d
Treatment and Indications for Surgical Treatment of Foot and Ankle Injuries Per A. F. H. Renström, Ulf Eklund, and Tönu Saartok
Injuries to the foot and ankle are common at work and during recreation. The foot is an anatomic masterpiece involving 28 bones, 19 muscles and tendons, and 115 ligaments. Many of these structures may be injured in one way or another, and it is important to secure a correct diagnosis if treatment is to be successful. This chapter includes a description of the different injuries that can occur in the foot and ankle with a focus on describing how these can be diagnosed and treated and when surgery is indicated. Included is an evaluation of when it is possible to return to work after surgery in each case. Because the foot and ankle are pathways for the impact of body weight and gravity, problems in these body parts are common, especially in active people. In industrial life, not only are people walking a great deal on hard surfaces, but they are also climbing, jumping, and so forth, thereby increasing the risk of foot and ankle injuries. Many of these injuries such as fractures and ligament and tendon ruptures are acute, and their treatment is seldom controversial. Probably most injuries, however, are overuse injuries that constitute a great clinical, diagnostic, and therapeutic problem. In these cases treatment and indications for surgery are often controversial, many times because the exact diagnosis is not clear. In this chapter we try to shed some light on these injuries, suggest indications for surgery, and estimate the postoperative time to return to work.
ANKLE SPRAINS In spite of the high frequency of ankle injuries, clinical diagnostic techniques and methods of treatment vary greatly, perhaps because the biomechanics of the ankle joint, its ligaments, and their clinical evaluation are not fully known. The anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament function as a unit. These may alternatively resist a specific motion, so the primary stabilizing ligament depends on foot position. As the foot plantar flexes, for example, strain in the ATFL increases, whereas that in the CFL decreases. Although the ATFL is the weakest ligament, it is clinically the most significant, involved as it is in 85% of common inversion ankle sprains and in 20% of those in combination with the CFL. Clinical ligamentous damage is primarily a function of tensile loading and is only secondarily affected by twisting or sheer forces. The most common mechanism of injury to the lateral ligaments of the ankle is plantar flexion and thereafter gradually increasing
progression to inversion. The lateral joint capsule tears first, followed by rupture of the ATFL, which causes hemarthrosis and subsequently subcutaneous ecchymosis. With further inversion, the CFL ruptures, and the posterior talofibular and deltoid ligaments sustain varying degrees of injury. In acute ankle sprains, the ATFL tears alone in 60% of cases, the ATFL tears in combination with the CFL in 20%, the posterior talofibular ligament tears in 10%, and the deltoid ligament tears in 3%. Treatment of severe grade III lateral ankle ligament tears has generated much controversy, but a critical review of the literature shows that functional treatment provides the quickest recovery to full range of motion (ROM) and return to work and physical activity without major residual problems.5 Functional treatment should include a short period of protection by tape, bandage, or brace along with early weight bearing. In most acute cases, this is recommended as the treatment of choice. ROM exercises and neuromuscular training should begin early. If residual problems persist after functional treatment, delayed surgical reconstruction or repair can be performed even years after the injury, with results comparable with those after primary repair. Some authors have recommended early surgical repair of acute severe ankle sprains in young athletes. Indications for acute repair for athletes listed by Leach and Schepsis7 are (1) a history of momentary talocrural dislocation with complete ligamentous disruption, (2) a clinical anterior drawer sign, (3) 10-degree or more tilt on the affected side with stress inversion testing, (4) clinical or radiographic suspicion of tears in both the ATFL and CFL, and (5) osteochondral fracture. Most techniques described for acute repair of ankle ligament injuries are similar. However, 10-20% of patients treated functionally develop residual problems. If a patient has continuous pain and swelling 3 to 4 months after an ankle ligament sprain, attention should be refocused to possible intraarticular (such as cartilage) lesions or other differential diagnoses. It is very important to be aware of the many differential diagnostic possibilities.
Chronic ankle instability Chronic ankle instability may be either mechanical or functional. Characterized by ankle mobility beyond the physiologic ROM, mechanical instability is measurable by the anterior drawer and talar tilt tests, respectively. Mechanical instability is considered to be present if anterior translation is more than 10 mm (or more than 3 mm greater than that of the uninjured ankle) or when talar tilt is more than 9 degrees (or 3 degrees greater than the uninjured ankle). Functional instability is a subjective feeling that the ankle is giving way during physical activity or walking on uneven ground. Chronic ankle instability, regardless of type, that presents with pain, recurrent giving way, and/or positive stress testing is an indication for operative treatment.
Surgical treatment The combination of mechanical and functional instability is the most frequently reported indication for delayed surgery. More than 50 procedures and modifications thereof have been described for treating chronic ankle instability. These can be loosely grouped
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as nonanatomic reconstructions or anatomic repairs. The reported success rates for nearly all these procedures are more than 80%. Nonanatomic reconstructions use another structure or material to substitute for the injured ligaments in the aim to stabilize the joint. Structures commonly used for grafting are the fascia lata or the peroneus brevis tendon. Numerous modifications of these classic procedures have been described. Anatomic reconstruction is based on the 1966 Broström report3 that direct suturing and repair of chronic ankle ligament injuries was possible and also successful promptly or many years after the initial injury, even if the ends of the ligament could be detected at surgery. Others reported that the elongated ligaments had healed encased in fibrous scar tissue. Several authors reported successful imbrication, or shortening, and reimplantation of the ligaments to bone to achieve good results. The Peterson procedure, for example, includes shortening of the ligament, repair through bony tunnels, and imbrication with local tissue.9 This anatomic technique repairs both the ATFL and the CFL, whereas most nonanatomic reconstructions, except for the Elmslie procedure and the Chrisman-Snook modification, repair only the ATFL. Repair of the CFL appears to be important, because insufficiency of this ligament may be a factor in the development of subtalar instability. Anatomic repair of both the ATFL and CFL through bony tunnels produces good long-term results and is recommended as the initial and standard procedure in most cases. If anatomic repair fails, a tenodesis procedure such as the Chrisman-Snook reconstruction is a good alternative. Nonanatomic reconstructions are indicated in patients with moderate arthritis or generally lax joints. After surgery and mostly depending on the pain, it is possible to return to a desk job within 1 to 2 weeks, wearing an ankle orthosis for about 6 weeks. However, the patient will depend on crutches during this period. Return to walking and more active work is possible after the healing and rehabilitation period, which most commonly lasts 3 to 4 months after surgery.
CHRONIC ANKLE PAIN Persistent ankle pain has been attributed to many causes, including incomplete functional rehabilitation. It has also been attributed to chondral or osteochondral lesions of the talus, occult fractures, and impingement syndromes.
Osteochondral lesions of the talus Osteochondral fracture, talar dome fracture, transchondral fracture, and osteochondritis dissecans are currently believed to be similar lesions. The etiology is traumatic, either as a single event or as multiple microtraumatic insults. Osteochondral lesions are arthroscopically staged in four levels. Stage I is a compression injury causing microscopic damage to an area of subchondral bone. Plain radiographs are negative. In stage II, a partially detached osteochondral fragment is detectable on careful examination of an adequate series of plain radiographs. In stage III, the osteochondral fragment is completely detached but remains in anatomic position, and in stage IV, the detached fragment is displaced elsewhere in the joint.
The patient usually has a history of a sprained ankle. Sometimes a “pop” can be heard. With a recent injury, moderate or severe lingering swelling of the joint can be seen. Tenderness is typically located just distal to the anterior tibiofibular syndesmosis or behind the medial malleolus, depending on the location of the lesion. After an inversion injury, the symptoms of a concomitant anterolateral osteochondral lesion may be “masked” in the signs of the ligament tear. When an osteochondral lesion is suspected, a careful plain radiographic examination is needed with anteroposterior, lateral, and oblique views of the ankle. Mortise views in plantar flexion should disclose a posteromedial lesion, and the corresponding view in dorsiflexion reveals an anterolateral lesion. If the patient is treated for a ligament injury alone (usually immediate functional rehabilitation), the symptoms persist, such as pain just distal to the anterior syndesmosis, recurrent swelling, or even catching or locking. A renewed plain radiograph investigation usually continues to be negative, calling for a bone scan of the ankle, which is very sensitive although not specific. If the bone scan is “hot” over the talus, further evaluation by plain tomography, computed tomography (CT), magnetic resonance imaging (MRI), or possibly diagnostic arthroscopy accurately determines the exact location and extent of the lesion. Appropriate staging and early treatment of osteochondral lesions of the talus provide the best results. Healing depends on capillary overgrowth of the injury site from the body of the talus. Immobilization of the area seems to be necessary to prevent the frictional effects of an uneven joint surface and potential progress of the lesion into more advanced stages, leading to nonunion. Lesions in stages I-III without established nonunion signs such as marked sclerosis, gross uneven joint surfaces, or osteoarthrosis are treated with a non–weight-bearing lower leg cast for 6 weeks, followed by a weight-bearing cast until radiographic evidence shows healing. An intraarticular injection of 10 ml lidocaine can be effective in stage I lesions. Delayed nonoperative treatment of stage III lesions often fails. These lesions, as well as stage IV lesions, are often treated early surgically to prevent further deterioration of the joint. An experienced arthroscopic surgeon reaches many of these lesions arthroscopically (removal of the detached lesion and debridement of the lesion bed), but open approaches are occasionally needed. Reattachment of the osteochondral lesion might be considered in the acute phase. Proper intraarticular access occasionally requires osteotomy of the medial or lateral malleolus. If an osteotomy is performed, it is essential that subsequent internal fixation is rigid to allow the important early motion in rehabilitation. Postoperative weight bearing is delayed 2 to 6 weeks (a full 6 weeks if osteotomy of the medial malleolus was performed). The prognosis after early nonoperative treatment in stages I-III is good in 75% of cases. The results of surgery are mixed, with reports that it yields a 40% to 80% rate of good results in late stage III and in stage IV lesions. Advanced lesions, where treatment has been delayed more than 1 year, historically have had a poor outcome.8 More recent treatment options such as osteochondral grafting or autologous chondrocyte transplantation, however, seem to yield promising results. Return to work that involves walking is possible within 2 to 3 months of nonsurgical treatment and 1-4 months after surgery, depending on the extent of the lesion and the method used.
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Loose bodies in the ankle Typically seen on plain radiographs, loose bodies in the ankle are often related to intermittent pain, swelling, and clicking. They emanate either from a stage IV transchondral fracture of the talus, from osteophytes on the anterior distal rim of the tibia or the dorsal neck of the talus, or, if multiple, from “synovial osteochondromatosis.” Posteriorly located loose bodies must be differentiated from an extraarticular os trigonum. Chip fractures may appear as loose bodies as well. Pure chondral loose bodies from lesions in the tibial plafond, in the talar dome, or from synovial chondromatosis cause the same symptoms. If plain radiographs are negative, however, more advanced measures such as MRI or arthroscopy are needed. Arthroscopic removal of loose bodies by a skilled arthroscopic ankle surgeon is the treatment of choice. Return to walking work is possible after 2-6 weeks.
Impingement syndromes Impingement synovitis of the lateral ankle after an inversion injury is not uncommon. Symptoms can fully mimic those of an anterolateral talar osteochondral lesion. Radiographic evaluation such as contrast-enhanced MRI used for detecting osteochondral pathology should reveal soft tissue abnormalities also. In the absence of concomitant chronic ligamentous instability, treatment of impingement synovitis involves the surgical removal of impinging tissue by way of the arthroscope. When lateral ligamentous insufficiency is present also, open removal of impinging chronic synovitis tissue together with an appropriate stabilizing procedure is recommended. Provided that no chondral lesions are present, postoperative results are generally excellent. Residual symptoms after ankle inversion sprains are quite common and are most often due to both mechanical and functional instability of the joint. Occasionally, however, anterolateral ankle pain and a feeling of giving way persist in spite of normal stability and well-performed functional rehabilitation. Examination reveals tenderness just anterior to the lateral malleolus, especially in dorsiflexion. Additionally, at times a snapping phenomenon from this region can be elicited when the foot is tested for inversion stability. In these instances, a meniscoid lesion of the ankle should be suspected. In such cases, both radiographs and bone scintigraphy are normal, thereby excluding osteochondral lesions. A possible etiology is local fibrosis that has developed after posttraumatic impingement synovitis after the inversion injury. Possibly torn strands or distal parts of the ATFL are caught in the talofibular joint, with subsequent synovitis and ultimately fibrosis developing. An intraarticular injection of 10 ml lidocaine may limit the pain. Together with a limited dorsiflexion, this test with local anesthesia secures the diagnosis. On surgical exploration, which is readily done arthroscopically, the lesion has a hyalinized meniscoid appearance. In most patients, simple excision of the lesion and surrounding reactive synovitis leads to full recovery. After an impingement syndrome that involves impingement synovitis or a meniscoid lesion that has been treated surgically, return to work may vary but should be possible within 1 to 3 months, depending on the type of job. The results and the prognosis after surgical treatment are usually good.
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Osteophytes at the anterior rim of the tibia, often called “soccer player’s ankle,” is a condition with decreased dorsiflexion and pain over the anterior part of the ankle joint. Dorsiflexion is blocked because of the formation of osteophytes on the distal anterior rim of the tibia and sometimes on the corresponding area of the dorsum of the talar neck. The osteophytes probably result from repetitive traction microtrauma to the ankle joint capsule with subsequent bleeding and ultimately reactive osteophyte formation. The history, clinical examination, and plain radiographs reveal the condition. Apart from soccer, the condition is seen also in sports such as American football and orienteering but only rarely in recreational athletes. The incidence in workers is unknown, but in occupations requiring repetitive traction of the anterior capsule of the ankle, this condition may appear. Although ankle dorsiflexion is not always fully restored, removal of the osteophytes openly or arthroscopically, followed by rapid rehabilitation consistently yields good or excellent results. After an impingement syndrome due to anterior osteophytes, return to work should be possible within 1 to 3 months, depending on the type of job. The results and the prognosis after surgical treatment are usually good.
Sinus tarsi syndrome Patients with a history of multiple lateral ankle sprains occasionally have residual pain and tenderness to palpation 2 cm anterior and distal to the tip of the lateral malleolus. This area, the sinus tarsi, is a funnel-shaped cavity bordered by the talar neck superiorly, the anterolateral calcaneus inferiorly and posteriorly, and the interosseous talocalcaneal ligament anteriorly. Recurrent subtalar sprains may cause microruptures in this broad flat ligament, leading to a chronic inflammatory reaction. The diagnosis is determined from the patient’s history and localized tenderness slightly but significantly distal to the ATFL. Usually, subtalar motion is impaired and may present with dull pain. Typically, ankle joint stability is not affected. Radiographs are negative, so the easiest way to diagnosis is a local anesthetic block into the sinus tarsi, which gives immediate pain relief. Initial treatment consists of rest and nonsteroidal antiinflammatory drugs (NSAIDs). Steroid injection into the sinus tarsi has proven helpful.6 In the rehabilitation phase, peroneal remobilization is emphasized because a sinus tarsi syndrome may be related to functional instability of the ankle joint. In the rare cases where symptoms persist, surgical “decompression,” that is, excision of the sinus tarsi contents (ligaments, fat), has been successful. Return to work may vary but is often possible 1 to 2 months after surgery.
Arthrosis of the ankle Compared with that of the hip and knee, the incidence of ankle arthrosis is low. It is most commonly seen after a fracture around the ankle, especially when fracture healing was allowed in a nonanatomic position. This leads to incongruency of the ankle mortise and often to rapid development of arthrosis. Other predisposing factors include severe ligamentous laxity and stage III-IV osteochondral lesions of the tibial plafond or the talar dome.
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As yet, no curative treatment has been found for articular surface injury and/or degeneration. Symptomatic treatment aiming at unloading the surfaces and reducing the reactive inflammation is easy and often very helpful for pain control. Especially with catching and locking sensations from detached osteophytes or pieces of cartilage, arthroscopic or open debridement and loose body removal may occasionally be an option. In severe cases, more extensive treatment must be considered; ankle arthrodesis is a reliable and well-proven way to relieve pain. Empirically, the functional disability of the arthrodesis often is well compensated in young patients. In selective cases where the ankle mobility and soft tissue quality are preserved, total ankle replacement is a recent treatment alternative. Return to work is often possible 1-2 months after arthroscopic procedures but may take 3-6 months after arthrodesis or total ankle replacement.
TENDON INJURIES AROUND THE ANKLE Traditionally, the term tendinitis has been used to describe most tendon overuse injuries. The tendon itself, however, consists of dense connective tissue with little inherent vascularity and is not predisposed to inflammatory change. Instead, the term tendinosis is used to define structural, most often degenerative, tendon changes. The surrounding tendon sheath, the peritenon, is usually highly vascularized and subject to inflammation or peritendinitis (paratenonitis) when overused. Tendon disease (excluding ruptures) can thus be described as tendinosis, peritendinitis (paratenonitis), or a combination. The symptom of pain from the tendon itself or paratenon is usually termed tendinopathy.
Achilles tendon overuse injuries Achilles tendon overuse injuries are common. Predisposition to these injuries can result from a number of intrinsic and extrinsic factors: lower extremity malalignment such as hyperpronation, increased femoral anteversion, or cavus foot and a tight Achilles tendon with poor flexibility. In recreational running athletes, poor shoes, hilly tracks, and training errors (such as sudden changes in mileage or speed and improper warm-up and cool-down) are related to heel cord overuse problems. The main symptom is pain, typically located 2-6 cm above the Achilles tendon insertion on the calcaneus. This region of the Achilles tendon complex is considered vulnerable and prone to overuse because of poor vascularity. Physical examination should include an evaluation of alignment and flexibility of the heel cord and inspection/palpation of the cord, the insertion, and the retrocalcaneal area, respectively. Four major differential diagnoses must be considered: 1. Peritendinitis is manifested as inflammation of the surrounding paratenon with crepitation occasionally present. 2. Tendinosis, or degenerative changes within the tendon itself, is characterized by gradual onset of pain and stiffness and localized tenderness and swelling of the tendon complex. 3. Partial rupture typically causes a sudden onset of pain. The condition is relatively rare and must be distinguished from the much more common total tendon rupture discussed below. Clinical examination reveals localized swelling and
distinct tenderness. The healing potential of partial Achilles tendon tears is poor, with more than 80% of patients having residual problems after 5 years.1 4. Retrocalcaneal bursitis, an inflammation of the bursa between the calcaneus and the anterior aspect of the Achilles tendon, is characterized by pain combined with tenderness and swelling anterior to the distal part of the heel cord. With time and when left untreated, the anterior fibers of the tendon insertion are severed, necessitating more extensive treatment and prolonged recovery period. Except in cases of partial tears, treatment of Achilles tendon overuse injuries is primarily conservative, the cornerstones being correction of malalignment, ice, and, most often, medication for pain control, ankle ROM exercises, and both stretching and strengthening of the plantar flexors and dorsiflexors of the ankle. For tendinosis types of lesions, daily eccentric strength training of the gastrocsoleus complex has proven successful in about 7 of 10 patients and is now considered to be the initial treatment and rehabilitation for most cases of tendinopathy. A 1-cm heel wedge can be useful also in reducing symptoms during daily activities like walking. We strongly advise against the use of local corticosteroid injections in the treatment of heel cord injuries. If conservative measures fail in spite of a 3- to 6-month period of adequate rehabilitation, surgery is indicated. Preoperatively, radiographic investigation excludes calcifications, and MRI or ultrasonography reveals the extent of structural changes within and around the tendon. These images help the surgeon chose and plan the appropriate procedure. Recently, Doppler-ultrasound investigations have been shown to reveal the presence of any pathologic neovessel formations anterior to the tendon, which seem to be associated with the pain of Achilles tendinopathy. Experimentally, ultrasound-guided sclerosing injections of the neovessels anterior to the tendon have shown promising results in control of the pain. Surgery for chronic peritendinitis includes removal of the thickened, scarred paratenon. A partial tear or tendinosis involves an incision longitudinally in the tendon and careful removal of pathologic tissue, after which the tendon should be closed carefully by adapting sutures side to side. In retrocalcaneal bursitis, the bursa should be removed and an excision osteotomy of the superior corner of the calcaneal tuberosity should be carried out. Postoperative care usually involves immobilization for about 10 days followed by mobilization that allows plantar flexion of 0-20 degrees in a walking boot. With appropriate indications and carefully monitored postoperative rehabilitation for 4-6 months, surgery yields good results in more than 80% of patients. After surgery, return to work depends on the diagnosis and the type of job. The patient can return to desk work within the first week but should keep the leg elevated. If the patient has mobile work that includes much walking, he or she can return to limited activities after 1 month using the walking boot. Return to full activity is usually possible 3-4 months after surgery. After sclerosing injections, the amount of pain reduction controls the return to work, which may vary significantly from 2-4 weeks to months. Another diagnosis to consider, complete Achilles tendon rupture most commonly occurs in active people around 40 years
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of age. As learned from sports activity, the most common injury situation involves a sudden change of motion, including dorsal ankle hyperextension. The typical history is a sensation of sudden pop and immediate but moderate local pain. Injured people often believe that somebody has hit the ankle from behind. Failure or impaired ability to plantar-flex the foot is typical as shown by squeezing the unweighted calf muscles (Thompson’s test). Before significant local swelling sets in, there is a clearly palpable gap at rupture level, typically 2-6 cm above the distal insertion. Recommended treatment for active people is most commonly surgical, allowing early tension to be put on the tendon for proper orientation of the healing collagen and better possibility to regain full strength. Early motion in the form of plantar flexion from 0 to 20 degrees is permitted after 1 week, and the patient can walk with this ROM in a walking boot after 2-3 weeks. The boot is usually discarded after 6 weeks. An alternative option for less active people, nonsurgical treatment involves at least 6-8 weeks of immobilization and a longer rehabilitation. With nonsurgical therapy, the risk for rerupture is much higher, and early motion is not possible. After a complete Achilles tendon tear, return to a desk job depends on crutch walking but is possible within 3 to 5 days regardless of treatment. If surgery has been performed, the patient can often walk reasonably well within 1 month using a walking boot and can walk properly and resume full activity 3-4 months after surgery. After nonsurgical therapy, return to demanding physical activity or work is usually not possible for 4-9 months.
Peroneal tendon injuries The peroneus longus and brevis tendons run down the lateral aspect of the ankle and midfoot to their insertions on the plantar side of the medial side of the midfoot (first metatarsal, medial cuneiform, and navicular) and on the proximal end of the fifth metatarsal, respectively. The tendons pass behind the lateral malleolus beneath the two retinacula, which hold them in position. Peroneal peritendinitis or tendinosis is typically elicited via stenosis under these retinacula. A longitudinal tear can occur as a result of either acute trauma or overuse. A common predisposing factor to the various forms of peroneal tendon disease is distortion of the local anatomy caused either by a fracture of the lateral malleolus or the calcaneus or by an ankle sprain. Pain, swelling, and joint sheath tenderness are located posterior and inferior to the lateral malleolus. Pain may be increased on weight bearing, but forced plantar flexion and inversion as well as resisted eversion of the ankle are even more painful. Physical examination must include an evaluation of tendon stability as discussed below. Subtalar motion usually is decreased. Primarily nonsurgical, treatment includes active rest, ice, NSAIDs, and crutches as acute measures. The addition of casting or a walking boot can possibly be helpful in some patients. Surgery to correct the cause is only occasionally necessary. Recurrent subluxation or dislocation of the peroneal tendons is an important differential diagnosis. The initial mechanism for this injury involves significant internal rotation in combination with inversion. There is sudden pain and a sensation of dislocation or subluxation over the lateral malleolar region.
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Treatment of these injuries is normally surgical; however, a nonoperative approach using a below-knee cast may be warranted in the acute setting. For recurrently disabling dislocations or subluxations, tendon stabilizing surgery that imbricates or reconstructs the stabilizing retinacula is the only meaningful treatment. Deepening of the peroneal groove is sometimes indicated. If the tendon has also a chronic pathologic condition, surgical incision and removal of the pathologic tissue can be valuable, although this procedure is not very common. After surgery, return to a desk job wearing a cast or a walking boot is possible within the first week. For people with more demanding duties, however, the rehabilitation time is 6 weeks in a walking boot followed by 6 weeks of rehabilitation, making return to harder labor possible after 3-4 months.
Flexor hallucis longus tendon overuse problems Overuse problems in the flexor hallucis longus tendon complex are common in ballet dancers because of frequent and forceful plantar flexion of the ankle and great toe (plié and point work). Repetitive push-off maneuvers also transmit substantial forces across the tendon and its sheath with possible irritation, swelling, and nodulus formation following. The result is pain and sometimes catching or even locking of the tendon, so-called functional hallux rigidus. Symptoms are most often located behind the medial malleolus where the tendon passes through a narrow fibrous tunnel, thereby predisposing to impingement. Other tight areas for flexor hallucis longus tendon passage are under the base of the first metatarsal and between the great toe sesamoids. Therapy consists of active rest, ice, NSAIDs, and crutches in the acute phase. A longitudinal arch support with firm soles is often helpful. Plié and point work in dancers, as well as similar forced toe-off exercises in labor, must be avoided until the patient is symptom free. If symptoms persist, especially if they are stenotic, surgery is indicated. At surgery, the fibrous tunnel is divided, and tenosynovectomy and tendon debridement are performed. When explored, local swelling of the tendon proper often reveals a partial rupture, necessitating scar tissue excision and tendon reconstruction. Postoperatively, the ankle is immobilized up to 10 days followed by a rehabilitation program for at least 1-2 months. Whereas return to desk jobs can occur within weeks, hard labor becomes possible after 2-4 months.
Tibialis posterior tendon overuse problems Posterior tibial tendon injuries due to overuse are seen in young active persons such as runners. Hyperpronation is a strong predisposing factor because mechanical demands on the tendon along its course behind the medial malleolus to the insertion on the navicular bone are significantly increased. Repetitive microtrauma leads to inflammation in the tendon sheath followed by partial tears and scar formation in the tendon itself. Complete ruptures are seen mostly in the elderly. Long-standing unidentified
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posterior tibial tendon ruptures or other causes of tendon insufficiency result in a unilateral flatfoot and highly or totally impaired independent toe rise. Clinical findings include tenderness and often swelling along the course of the tendon behind and beneath the medial malleolus. Early on, crepitus is frequently present. Passive pronation or resisted supination of the midfoot exacerbates the pain. Treatment in the acute phase includes active rest, ice, NSAIDs, and a medially posted orthotic. In severe cases, a short leg non–weight-bearing cast or walking boot for 2 weeks usually relieves the pain. After careful biomechanical evaluation, patients with flatfoot deformities need more advanced orthotic treatment. In chronic cases, surgical exploration is considered to address potential tenosynovitis, tendinosis, tendon tear, and stenosis along the tendon course. Return to work depends on the resolution of pain. After surgery, 2 to 4 months is often needed for healing and rehabilitation before pain-free walking is possible.
SUBTALAR JOINT INJURIES Subtalar joint dislocations Subtalar joint dislocations or subluxations are infrequent, but when occurring they are caused by a fall from a height or a traffic accident. Substantial torsional force is required to accomplish these partial or total dislocations due to the pronounced inherent bony and ligamentous (medially the deltoid and laterally the calcaneofibular and talocalcaneal) stability of the subtalar joints. These injuries are classified according to the direction taken by the foot in relation to the talus, thus medial, lateral, posterior, or anterior. Medial dislocation is by far the most common subtalar dislocation reported, the injury mechanism being forced inversion. The condition is very painful to the hindfoot, and the deformity in total dislocations is marked, with the midfoot and forefoot severely adducted. Prompt management is crucial because of potential compromise of neurovascular structures. Anteroposterior and lateral radiographs of the ankle and foot are taken without delay. Fractures of the malleoli, talus, fifth metatarsal, or navicular sometimes accompany these injuries. An attempt at closed reduction under intravenous sedation may be justified, but if not successful, immediate open surgical reduction must follow. Once reduced, the subtalar and talonavicular joints are typically stable, and no internal fixation is needed. Postoperatively, immobilization in a short leg non–weight-bearing cast for 3 weeks is recommended, followed by gradual ROM exercises and progressive weight bearing. Provided that subtalar dislocations are treated promptly and reduction is successful, the prognosis is satisfactory in many patients. Severe soft tissue problems and associated fractures tend to worsen the outcome. Late complications include impaired subtalar motion, arthrosis of the joints affected, and persistent swelling and pain. In those cases, a subtalar arthrodesis is sometimes warranted. Return to work depends on the resolution of pain. After successful closed reduction, the return to desk jobs is possible within weeks, whereas surgical intervention often requires a rehabilitation time of 2-4 months before the patients return to physically more demanding jobs.
FRACTURES Fracture of the talus The talus holds a key position in the ankle joint, that of linking the leg and the foot. It articulates to the tibia and fibula, calcaneus, and navicular. More than 60% of the surface is covered with articular cartilage, which leaves only a limited area for nutritional blood supply. Talar blood supply may be easily compromised with trauma and/or surgery in this region. Apart from the common minute avulsions from the lateral part of the talar neck after lateral ankle sprains, substantial trauma is required to fracture the talus. Most commonly, a talar neck fracture is sustained from a forceful passive dorsiflexion of the ankle joint, as occurs when landing on the feet after a fall from a height. In this situation, the anterior margin of the distal end of the tibia is thrust into the dorsal talar neck. The patient has significant ankle swelling and pain. Radiographs give details as to the fracture pattern and possible subluxation or dislocations. Displaced fractures require reduction and rigid fixation, followed by early non–weight-bearing ROM exercises. For undisplaced fractures, 6-8 weeks of immobilization in a neutralposition short leg cast is recommended. Weight bearing is delayed until radiographic union is evident. The prognosis after displaced unreduced fractures is poor. Better results are achieved after anatomic reduction and stable screw fixation. Even with apparently nondisplaced fractures, however, ankle joint arthrosis develops in one third of the patients at late follow-up. Return to work depends on the outcome of fracture treatment. In successful cases, patients may return to manual labor in 3-6 months, but nonunions and ankle joint arthrosis may lead to life-long handicaps.
Fractures of the calcaneus As with talar fractures, substantial force is required to fracture the calcaneus. Landing on the heel after a fall or jump from a height is the most frequent injury mechanism. Partly because of the associated significant swelling, a calcaneal fracture is very painful. Initial care should always include strict elevation of the foot above the heart level of the patient. Plain radiographs yield the diagnosis, but further imaging using CT gives additional valuable information regarding the extent of the fracture and its effect on the subtalar joints. The risk of compartment syndrome in the intrinsic muscle compartments of the foot necessitates monitoring the clinical course and compartment pressures and performing a fasciotomy when indicated (pressure above 35 mm Hg) to prevent ischemic muscle injuries and clawing of the toes. The treatment of calcaneal fractures is still controversial. Because of the topographic complexity of the bone and the variable fracture patterns, it is difficult to obtain comparable groups when different treatments are evaluated. A full spectrum of treatment modalities ranging from reduction, surgery, or immobilization, to closed reduction and immobilization, to open reduction and internal fixation is used. At present, however, surgical treatment is increasingly favored. The main indications for surgical intervention are
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severely disrupted posterior subtalar facets, significant upward displacement of the calcaneal tuberosity, or valgus displacement of the tuberosity of the calcaneus with abutment against the lateral malleolus. If a nonoperative approach is chosen, early motion is recommended, whereas weight bearing is delayed for at least 8 weeks. Operative treatment requires care by an orthopedic surgeon with extensive hindfoot fracture experience. Regardless of treatment, the long-term prognosis after calcaneal fractures is guarded. Eighty to 90% of patients have residual symptoms. Typically, subtalar mobility is significantly inhibited. In many cases, a permanent custom-made heel orthotic is required to control pain and swelling. Depending on the location and extent of the injury, return to work varies but takes at least 3-6 months if repetitive weight bearing is demanded in the job. It is sometimes impossible to return to hard work because of persistent pain during walking.
STRESS FRACTURES Stress fractures of the foot and ankle Stress fractures of the foot and ankle, typically in the distal fibula, tibia, calcaneus and navicular bone, and metatarsals, are common in athletes and probably workers. Bone is continuously adapting to new loading patterns. A stress or fatigue fracture is the failure point in this normal adaptive process. Pain in the periosteum is an early warning sign of overloading. If fatigue and microdamage occur too rapidly, new bone cannot develop fast enough, the bone weakens, and a stress fracture may gradually develop. During gait the muscles play a major role in energy absorption. Muscle fatigue impairs shock absorption, leading to altered stress distribution and increased compressive loads on the bone with a greater risk for stress fracture. A complementary contributing factor in the possible development of a stress fracture is biomechanical imbalance such as skeletal asymmetry and leg length discrepancy. A short leg is more susceptible to stress reaction and fracture. Some anatomic abnormalities predispose to stress reactions, although unpredictably. A rigid foot, for example, puts increased stress on the metatarsals. Hard surface running places the second metatarsal at risk if a tight heel cord, a long second metatarsal, or a flexible nonsupportive great toe is present also. Other factors include exercise or prolonged walking on hard surfaces, improperly supportive shoes, and injury to the opposite extremity, causing the patient to protect the injured limb by placing more weight on the contralateral limb. The common clinical course includes insidious onset of pain that initially is vague. With continued stress, pain increases and becomes more localized with possible soft tissue swelling. Clinical examination reveals distinct tenderness over the lesion. The early diagnosis is verified by scintigraphy or MRI followed by CT, whereas plain radiographs typically become positive at 3-8 weeks. Treatment consists of activity modification to the limits of comfort. Nongravity exercises are initiated, and casting is recommended only with multiple fractures, intolerable pain, or fragmentation. Healing of a properly treated stress fracture occurs in 1-4 months but could take 6 months. A useful clinical healing test is having the patient hop on the affected limb without pain. In multiple
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or recurrent stress fractures, screening for endocrine and/or nutritional dysfunction, especially in underweight persons, is indicated.
Hindfoot stress fracture Although relatively uncommon, calcaneal stress fractures have been reported in military recruits in vigorous physical training for more than 16 hours a day. Diffuse pain about the heel is aggravated by its compression from a medial to lateral direction. Pain is not localized only to the plantar aspect of the heel. Treatment includes weight bearing with crutches as tolerated, a shockabsorbing heel insert, and pain control as required. At least 8 weeks are usually required for healing. The regimen of no-weight or partial weight bearing of these injuries makes it possible for white-collar workers to return to their jobs within weeks, whereas the return to heavy and demanding labor may take several months.
Metatarsal stress fractures Every fifth stress fracture (17-20%) in the lower extremity is located in the metatarsals, and the second ray is the most common site. Surgery for hallux valgus is related to stress fracture of the second metatarsal because of altered loading patterns. Hypermobility of a metatarsal can predispose to adjacent metatarsal stress fracture. Typical locations of metatarsal fractures are first metatarsal-medial base, second and third-distal diaphysis, fourth-middle or distal diaphysis, and fifth-proximal (junction metaphysis/diaphysis). Symptoms typically progress slowly in a “crescendo” effect. It can take 1-2 months or more before stress fractures become visible on plain radiographs. A bone scan, MRI, or possibly CT is the key to early radiographic confirmation of a stress fracture. Metatarsal stress fractures are generally treated nonoperatively; early in nondisplaced fractures, activities are limited for 4 weeks. Running in 3-4 feet of water is beneficial, because the forefoot then usually is protected from heavy repetitive loading. Stress fractures through the fifth metatarsal, however, need special attention. Nonoperative treatment implies 6-8 weeks of non–weight-bearing casting. Less restricted nonoperative treatments have shown high failure rates. An increasing number of investigators advocate early internal fixation because this markedly decreases healing time and return to strenuous activities.4 Signs of chronicity of the fracture, such as cortical thickening and intramedullary sclerosis, strongly indicate that only open treatment will be successful. Surgical alternatives are curettage, bone grafting, and cerclage fixation of the fracture; drilling of the medullary canal followed by malleolar screw fixation without opening the fracture; or combinations of these. Postoperative casting time varies from 2 to 8 weeks, and the return to strenuous activities, or heavy labor, requires clinical and radiographic evidence of healing, most often 8-12 weeks.
Hallux sesamoid stress fractures Hallux sesamoid stress fractures are rare, much rarer than sesamoiditis, a difficult differential diagnosis. Bipartition of a sesamoid is not uncommon, so radiographic diagnosis is difficult also. Furthermore, scintigraphy in both stress fractures and sesamoiditis is positive. Stress fractures, however, do not heal with immobilization or prolonged inactivity. If other causes of pain can be excluded, a sesamoid stress fracture is treated with excision of the bone, with usually a good outcome thereafter. It should be noted that surgical access to the lateral sesamoid is
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difficult and its safe removal requires significant surgical experience in this area.
Tarsal navicular stress fracture In nonathletes, navicular stress fractures are uncommon. The condition is characterized by an insidious onset of vague arch pain, increased pain in the midfoot with motion, and limited dorsiflexion of the ankle. Activity increases the discomfort. Typically, but not always, tenderness is localized over the navicular bone. Plain radiographs are most often normal, and a bone scan (or MRI) is required for diagnosis. Plain tomography or CT also may delineate the extent of the injury. The fracture is typically sagittally oriented in the central third of the bone, due possibly to the relative avascularity of this part of the navicular. Treatment of acutely displaced fractures calls for open reduction and internal fixation. To heal uneventfully, nondisplaced fractures should be treated with a non–weight-bearing cast for 6-8 weeks. In patients not casted or those given a weight-bearing cast, the complication rate is high with delayed union, nonunion, or recurrence of the fracture, calling for surgical bone grafting. Postoperatively, the lower leg is immobilized in a non–weight-bearing cast until union has occurred, which may take 2-4 months. After surgery, return to a desk job is possible within a week, whereas resumption of weight-bearing or other types of heavy work may take 3-4 months.
HEEL PAIN Heel pain is a common and potentially disabling condition with many possible causes. Distinction of these is important because treatment and the expected outcomes differ. A thorough history of the patient’s complaints and pain and a careful physical examination are mandatory tools in establishing a correct diagnosis. These include an evaluation of the patient’s characterization of the pain, including onset, duration, nature, localization, and relation to work and/or physical activity. Alignment of the lower part of the leg, ankle, and foot; the ROM of the ankle and subtalar joints; and the status of the longitudinal and transverse arches of the foot should be determined. Skin abnormalities such as discoloration, wounds, bumps, blisters, and tender areas, including reactions to the tapping of nerve branches (Tinel’s sign), should be noted.
Heel pain syndrome Pain localized over the origin of the plantar fascia on the anteromedial calcaneal tuberosity is termed heel pain syndrome or plantar fasciitis. Preceded by overuse, the onset is insidious. The pathogenesis is believed to be traction periostitis and microruptures of the origin of the plantar fascia. Symptoms include morning stiffness and pain that resolve during the day. Pain increases after prolonged walking, however, and jumping and running can be intolerable. Palpation reveals pain in the very localized area just described that is typically not elicited with passive dorsiflexion of the toes, which causes traction on the plantar fascia. Plain radiographs are negative and may or may not show a calcaneal spur.
Conservative treatment consists of active rest, pain control with NSAIDs, and usually an orthotic device (shock-absorbing heel cup or a custom-made nonrigid orthosis). Stretching exercises of the plantar fascia and the Achilles tendon are advocated. Within a 3-month time frame this treatment is usually successful, but up to 1 year may be required in some cases. In refractory cases, a corticosteroid injection may be considered, but it is crucial that the cortisone is deposited deep to the plantar fascia to avoid plantar fat pad atrophy. In the few cases in which disabling symptoms persist, surgical treatment such as proximal plantar fascia release is indicated. The time needed for healing and rehabilitation is 2-5 months.
Heel spurs The relation between plantar heel pain and a heel spur on radiographs is considered to be very poor. Only half of the patients with heel pain have a spur, and of all people with a heel spur, only 10% to 15% have heel pain. Indeed, a heel spur, when present, is located deep to the origin of the plantar fascia, in the non–weight-bearing substance of the flexor digitorum brevis muscle.
Plantar fasciitis True plantar fasciitis is an inflammation of a greater part of the plantar fascia, with pain on passive dorsiflexion of the toes and tenderness over the proximal area of the plantar fascia. Symptoms therefore predominate in the plantar aspect of the midfoot rather than the heel. Special orthotics designed to relieve the pressure on the plantar fascia should be used. If symptoms persist in spite of adequate rest and orthotic use (at least 36 months), surgery such as proximal plantar fascia release should be considered.
Plantar fascia rupture and heel spur fracture Plantar fascia rupture and heel spur fracture are characterized by pain in the same area as in heel pain syndrome, but the onset is sudden. Ruptures of the plantar fascia are not common, but these are reported most often in the literature after cortisone injection in the plantar fascia. In patients with acute trauma or persistent pain, a special x-ray projection (45 degrees medial-oblique) that can reveal a fractured spur should be taken. Treatment is primarily conservative: active rest, NSAIDs, crutches, and very gradual resumption of weightbearing activities over a 6- to 10-week period. If symptoms persist and nonunion is suspected, surgical removal of the detached fragment must be considered.
Fat pad atrophy The plantar fat pad of the heel is a highly structured tissue designed to withstand repetitive impact loads. If the structure fails, as could happen after long-time overuse, the shock-absorbing capacity of the tissue markedly decreases, usually resulting in pain.
Chapter 8d
On clinical examination, the heel pad feels softer and thinner with the underlying calcaneal tuberosity readily palpable. Maximum tenderness is located centrally on the weight-bearing area of the heel, as opposed to the anteromedial tenderness location in heel pain syndrome. Treatment is nonsurgical, using support with a cushioned heel cup and soft-soled shoes. Because they may aggravate the atrophy, local cortisone injections are contraindicated.
Fat pad inflammation Inflammation of the fat pad produces symptoms similar to those of fat pad atrophy except for the lack of palpable thinning or softening of the heel pad. In this situation, the supportive heel cup should be semirigid rather than cushioned. Prognosis is usually good, but symptoms may need over 6 months to resolve completely. Again, local cortisone injections are contraindicated. After a period of heel pain, return to work varies with the various diagnoses as described above. Most people can work during nonsurgical treatment of heel pain, but walking should be restricted. After surgery for heel pain (which involves mostly release of the plantar fascia), the healing and rehabilitation time needed to return to walking is usually around 2-4 months. Sometimes tenderness remains, and the rehabilitation time may then be prolonged.
NERVE INJURIES Manifestations of peripheral nerve injuries include paresis/paralysis of extrinsic and intrinsic muscles, sensory defects, pain and contractures, and a risk for secondary changes such as pressure ulcers and neuropathic arthropathy. In a neurologic examination of the foot and ankle, careful assessment of sensory, motor, and sympathetic function is important. The examination should include evaluations of gait, heel and toe walking, and the Trendelenburg sign in the hip. The presence of muscle paralysis, stiffness, contracture, spasticity, ataxia, pain, and fixed or functional present deformity should be registered. Foot contractures are studied first with flexed knees, then with straightened knees to evaluate the effect of the heel cord on the deformity. Cavus, planus, varus, valgus, and equinus of the whole foot and forefoot are assessed together with flexibility of the arches as well as claw toes or hammer toes. Skin moisture reflects sympathetic function, and peripheral nerve disease is often accompanied by sympathetic degeneration with resulting dry, thin skin. Tinel’s sign is closely evaluated as regards presence, intensity, and location. Documentation with drawings and photographs of areas with nerve dysfunction is very helpful in the assessment and treatment of nerve disorders. Causalgia, or reflex sympathetic dystrophy, is characterized by overactivity of the sympathetic nervous system because of irritative lesions of sympathetic nerve fibers. Burning pain and dry hot skin are typical manifestations. A sympathetic nerve block often improves symptoms. Charcot deformity is a joint deformity that can occur in conjunction with any neuropathy, with sensory deficit developing in a joint subjected to loading of the body weight. This is commonly seen in the midfoot joints in conjunction with diabetes mellitus.
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Classification Five degrees of nerve injury are traditionally distinguished, depending on the severity: I. First degree: Conduction deficit, axon intact. Prognosis is good. II. Second degree: Axon severed but intact endoneurium, Wallerian degeneration. Regeneration follows the pattern of regrowth. Axon regeneration averages 1 to 2 mm/day and is typical of a second-degree injury. III. Third degree: Disorganization of internal structure of the funiculi, minor perineurium changes, irregular regeneration. In a third-degree injury, regeneration is blocked by disorganization of the Schwann’s cell tubes. As soon as it is evident that recovery is slowed or absent (Tinel’s sign along nerve route), exploration is considered. Distal tingling on percussion over a nerve marks the most distal point of regenerating sensory axons. This is very useful in mapping nerve regeneration. IV. Fourth degree: Axonal rupture, funicular and perineural disruption. The nerve trunk is intact, but nerve bundles are disorganized. Spontaneous functional recovery is rare. V. Fifth degree: Loss of continuity of the nerve trunk. Fourthand fifth-degree injuries may not be distinguishable unless an open injury has revealed the nerve status. Although motor nerve fibers are usually more susceptible to compression and are therefore the first to fail and the last to recover, this is not always true. Most compression neuropathies recover by the sixth month; when they do not, intraneural fibrosis and disorganization have occurred. Neurolysis, both external and internal, offers some hope of improvement. When severe third- and fourth-degree lesions are present with no further chance of recovery, resection of the lesions with autografting can improve the outlook, although only in selected cases.
Entrapment neuropathies The pathogenesis of nerve entrapment is considered to be gradual constriction by anatomic structures about a nerve and its chronic compression against a nonyielding structure. Nerve entrapments usually give mixed motor and sensory symptoms, the latter of which typically come relatively late. The relationship between nerve fiber size, motor/sensory containment, and vulnerability to compression is uncertain. Many believe that sensory fibers are more resistant to compression than motor fibers are, but others disagree. Entrapment of a sensory or mixed nerve results in tenderness over the entrapment point. If the compression has produced axonal interruption, Tinel’s sign may be elicited at the point of compression. Electromyographic and nerve conduction studies can be helpful in identifying and localizing an entrapment lesion.
Valleix phenomenon Pain and hypersensitivity are sometimes seen proximal to a nerve compression. Blocking the nerve at the entrapment site relieves the proximal symptoms. It is postulated that compression can result in proximal nerve hyperirritability. External decompression leads to the relief of symptoms, provided that intraneural fibrosis is not established. Intraneural fibrosis is often present
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once motor denervation has occurred (as determined by atrophy and denervation signs on electromyography). Hence, surgery should not wait until late in the process. If intraneural fibrosis has indeed developed, however, intraneural neurolysis under adequate magnification can yield some symptom improvement.
Entrapment of the common peroneal nerve The common peroneal nerve, which transmits motor innervation to the peroneal muscles and to the extensors of the foot and ankle, is vulnerable to compression at the fibular head and neck. An intraneural or extraneural ganglion (with or without connection with the tibiofibular joint), an enlarged fabella, or a bone tumor in the proximal fibula are the most common causes of compression at this level. The peroneus longus muscle has two heads: a superficial head attaching to the head of the fibula and a deep head inserting at the fibular neck, below the nerve. After subtalar motion of the foot, the nerve slides back and forth between the two muscle heads, potentially leading to nerve compression. These injuries can be part of overuse syndromes. People who wear wooden shoes, walk on hard floors extensively, or make repeated flexion motions in their jobs may be prone to this kind of injury. Symptoms include pain and hypoesthesia in the lateral leg and ankle, a “weak ankle” feeling, and even occasionally footdrop. Objectively, there is a positive Tinel’s sign at the compression site together with sensory deficit and peroneal weakness. In most cases, external decompression gives relief. Intraneural neurolysis is indicated when intraneural fibrosis is present. It should be noted that the peroneus longus muscle is a powerful plantar flexor of the first ray; it maintains the medial longitudinal arch of the foot and is an important subtalar evertor. Weakness of this muscle leads to an altered distribution of the load on the foot when standing; more load must be borne by the second and third metatarsal heads, with potential metatarsalgia following. The lateral cutaneous nerve of the calf and the sural communicating nerve, both sensory, emerge in the popliteal region from the common peroneal nerve. Compression at this level leads to pain on the lateral side of the lower leg, and/or dorsolateral foot. Local anesthesia blocks at the maximum point of tenderness usually relieve the pain permanently.
Entrapment of the superficial peroneal nerve From the division of the common peroneal nerve high in the lower leg, this strictly sensory nerve travels between the anterior intermuscular septum and the fascia of the lateral compartment and emerges one or two nerves through the fascia at the junction between the middle and distal third of the lower leg. It runs subcutaneously in front of the lateral malleolus to innervate the major part of the dorsum of the foot. The anatomy of the terminating branches varies greatly, and they are at risk in surgery around the first metatarsal head. Transverse skin incisions on the dorsum of the foot should be avoided. The nerve can be trapped where it pierces the fascia. Recurrent ankle sprains, causing stretching of the nerve, predispose to this condition. Pain located over the lateral aspect of the calf and ankle and in the dorsolateral foot can be exacerbated by inversion and plantar flexion of the ankle. Objectively, local tenderness and a positive Tinel’s sign are present. Three to 5 ml of a
local anesthetic relieves the symptoms, sometimes permanently, and perineural cortisone may be tried as an additional nonoperative measure, but occasionally pain recurs and requires surgical decompression.10 Peripheral branches on the dorsum of the foot may be compressed by tight shoes such as ski boots, cicatrix, or tarsometatarsal joint osteophytes, and produce entrapment symptoms. In these cases, preventive appropriate shoe correction is mandatory. Treatment with local anesthetics and sometimes a local cortisone injection is usually successful. Occasionally, decompressive surgery, including osteophyte removal, is necessary.
Entrapment of the deep peroneal nerve The deep peroneal nerve runs together with the anterior tibial artery on the anterior aspect of the ankle, beneath the extensor retinaculum, and then between the extensor hallucis longus and the extensor digitorum longus tendons to the dorsum of the foot. A motor branch runs laterally on the mid-dorsum of the foot to the extensor digitorum brevis muscle, terminating with sensory innervation of the first dorsal web space. Compression between the fascia and adjacent skeleton (osteophytes from the medial tarsometatarsal joint) leads to pain over the dorsum of the foot with occasional radiation into the first web space, where local tenderness also is present. Tinel’s sign is sometimes positive, and hypoesthesia in the first dorsal web space may be present. During treatment, tight shoes must be avoided at least temporarily. Surgical removal of osteophytes may be necessary, with care taken to not injure the nerve.2
Entrapment of the posterior tibial nerve and branches A mixed motor and sensory nerve, the posterior tibial nerve runs together with the posterior tibial artery behind the flexor digitorum longus tendons in the distal third of the lower leg. Covered by the flexor retinaculum, it then courses behind and below the medial malleolus. At this point, the posterior tibial nerve gives rise to the medial calcaneal nerve, a sensory branch that pierces the flexor retinaculum together with a small artery, runs directly under the posterior calcaneal tubercle, and innervates the skin of the heel pad. This nerve may be involved in heel pain syndrome. The tibialis posterior nerve divides beneath the flexor retinaculum to form the medial plantar nerve and the lateral plantar nerve, which correspond respectively to the median and ulnar nerves of the hand. The medial plantar nerve runs under the anterior part of the calcaneal tuberosity; gives motor branches to the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and lumbrical muscles; and provides sensation to the medial part of the sole, including the medial 31/2 digits. The lateral plantar nerve also runs down along the medioplantar aspect of the calcaneal tuberosity along its course to the lateral part of the plantar pedis and the lateral 11/2 digits. Motor branches run to the adductor hallucis muscle, the interossei, and the small muscles on the lateral aspect of the foot. Although entrapment of the posterior tibial nerve at the level of the knee or lower leg is rare, it is frequent within the fibroosseous tunnel behind and distal to the medial malleolus, where it is referred to as tarsal tunnel syndrome. This syndrome is characterized by burning pain on the sole of the foot, often
Chapter 8d
accentuated by ambulation but characteristically also annoying at night. Predisposing factors include chronic instability and/or edema, hyperpronation, and a posterior bony prominence of the talus. Motor deficits and intrinsic muscle paresis/paralysis typically come late. Tarsal tunnel syndrome is positively correlated with pregnancy, as is carpal tunnel syndrome, with which this condition has many similarities. Objectively, a positive Tinel’s sign is usually present together with numbness of the sole and tenderness behind and below the medial malleolus. Delayed nerve conduction of the medial and lateral plantar nerves further supports the diagnosis. The treatment of choice is surgical decompression, which involves dividing the flexor retinaculum and freeing the nerve proximally and distally. Internal neurolysis is indicated if the nerve is fibrotic. If it is symptomatic by causing compression of the nerve, occasionally an os trigonum is removed.
Jogger’s foot Entrapment of the medial and/or lateral plantar nerves is occasionally seen as they pass under the abductor hallucis muscle. “Jogger’s foot” is a medial plantar neuropraxia causing burning heel pain, aching arch, and loss of sensation on the sole of the foot behind the great toe. The entrapment site is typically the point where the abductor hallucis crosses the navicular tubercle. Anesthetic blocks, steroids, and antivalgus orthotics are initial treatment modalities, with surgical decompression sometimes indicated.
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although some prefer a transverse plantar incision near the MTP joint crease. Surgery usually yields a 75% to 80% rate of good or excellent results. If secondary surgery is attempted, a longitudinal plantar approach is recommended by most authors to achieve the necessary more extensive exposure.
Entrapment of the sural nerve Entrapment of the sural nerve can occur anywhere along its course from the popliteal fossa to the toes. Purely sensory, the sural nerve arises from the tibial nerve 3 cm above the knee joint, runs deep to the deep fascia of the calf to the distal third of the lower leg where it becomes superficial, runs behind the lateral malleolus, and innervates the lateral aspect of the sole. The nerve is often sacrificed when used for nerve grafting with minor or no subjective problems thereafter. Inadvertent traumatization, however, could cause annoying discomfort. Conditions that may include local sural nerve compression include Achilles tendon peritendinitis, recurrent ankle sprains, lateral calcaneal or subtalar joint problems, and fractures of the base of the fifth metatarsal. Symptoms include shooting pain and paresthesias along the course of the nerve. Local tenderness and a positive Tinel’s sign are characteristic. Occasionally, numbness is noted. Nonoperative treatment includes avoidance of external nerve compression as well as NSAIDs and occasionally a local block. If these measures fail, surgical decompression is advised.
Entrapment of the saphenous nerve Morton’s neuroma The plantar interdigital nerves are terminal branches of the medial and lateral plantar nerves. Morton’s neuroma is currently believed by most investigators to be the reaction of a plantar interdigital nerve compression. The condition is characterized by metatarsal pain, often poorly localized but at times clearly radiating into the toes (usually the third and fourth but possibly any or all). Pain is aggravated by ambulation and by tight shoes. With dorsiflexion of the metatarsophalangeal (MTP) joints, the plantar interdigital nerves and vessels are angulated over the leading edge of the transverse metatarsal ligament at or just proximal to the bifurcation of the nerve to two adjacent toes. Irritation to the nerve results in pseudotumor formation. The third-space plantar nerve is formed from both the medial and lateral plantar nerves, which possibly explains why this nerve is larger and more fixed than the other interdigital nerves and therefore more prone to compression. Other factors predisposing to this condition include cavus foot, high-heeled shoes, and weakness of the intrinsic and peroneal muscles. Treatment consists of shoe correction to diminish pressure on the metatarsal heads. In reducing MTP motion, a metatarsal bar is often helpful. The bar should be placed posterior to (not at the level of) the metatarsal heads and preferably between the two soles of the shoe. The shoe also should have a wide toe box and a low heel. A metatarsal pad set just behind the point of tenderness may be a successful alternative. NSAIDs and local steroid injections are advocated by some investigators. Foot exercises meant to strengthen the intrinsic, the peroneus longus, and the tibial posterior are recommended. In refractory cases, surgical removal of the compressed part of the plantar interdigital nerve is warranted, usually through a dorsal longitudinal approach,
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At foot and ankle level, entrapment of the exclusively sensory saphenous nerve is rare. This nerve crosses over the tibia in a posteromedial to anterior direction 5-7 cm above the ankle joint and together with the greater saphenous vein runs anterior to the medial malleolus. It innervates the proximal medial part of the dorsum of the foot. Depending on the nerve involved and the type of surgery performed, return to work varies. If decompression is carried out, the patient can return to work after a couple of weeks, even to a job that requires walking. Surgery that involves excision or extensive release may require longer recovery, and return to work is then possible in 2-4 months.
MIDFOOT INJURIES Midtarsal sprains The midtarsal or transverse tarsal joint, often called Chopart’s joint, that is, the talonavicular and calcaneocuboid joints, holds a key position in the medial and lateral longitudinal arches. It also acts together with the subtalar joints in inversion and eversion. Midtarsal sprains are potentially disabling injuries, with healing times often much longer than anticipated. In general, substantial force is required to cause significant injury to these joints, for example, when the front foot is caught and the person falls and twists them. A comprehensive classification system has been developed that ranges from nondisplaced ligamentous injuries, through subluxations, to dislocations. Fractures of adjacent bones may or may not be present. Soft tissue engagement can be significant.
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In addition to plain radiographs, CTs, including three-dimensional reconstructions, or MRIs are most helpful in delineating the extent of severe injuries in this region. Undisplaced injuries are normally treated nonsurgically. Because of potential instability, 6 weeks in a non–weight-bearing cast followed by 2 weeks in a walking cast is recommended. During rehabilitation, a shoe with a firm sole and a longitudinal arch support should be worn. Displaced fractures, subluxations, and dislocations all need to be reduced. Occasionally, closed reduction is successful, but usually open means are required. Internal fixation is performed followed by restricted weight-bearing casting for 3-6 weeks. The prognosis after midtarsal injuries is highly dependent on whether reduction is achieved. Nonreduced injuries and extensively comminuted fractures often do poorly. In these cases a future arthrodesis, with prolonged time back to work, must be considered.
Tarsometatarsal injuries (Lisfranc’s joint) The second metatarsal base is the primary bony stabilizer of the tarsometatarsal articulation, sitting in a tight mortise between the distal parts of the first and third cuneiforms. The cuneiforms and the metatarsal bases are wedge shaped, being wider dorsally, and thereby contribute to the metatarsal transverse arch. Motion in the joints is restricted, but together they allow some pronation and supination of the forefoot. Severe trauma to Lisfranc’s joint caused by direct or indirect forces on the midfoot can result in a varying pattern of fractures and dislocations. Indirect forces along the metatarsals may result in dislocation of the joint, with or without fractures through the plantar aspect of the metatarsal base. After fracture-dislocation of the Lisfranc joint complex, soft tissue injuries are often extensive, and because these tissues would be further compromised, tourniquet should be avoided. Injuries to Lisfranc’s joint are notorious for missed initial diagnosis and inadequate treatment. The most constant reliable radiographic sign is a slight widening between the bases of the first and second metatarsals, between the second and third metatarsals, or between either of the cuneiforms. Fractured fragments should be sought between the first and second metatarsal bases and between the medial and middle cuneiforms. For adequate descriptions of radiographic findings, oblique views are necessary. The goal of treatment is a stable anatomic reduction. Because of interposing soft tissues or fractured fragments, reduction is rarely successful by closed means. Open reduction/internal fixation is recommended; transfixion is accomplished with Steinmann pins or Kirschner wires (note that a standard Kirschner wire alone will not hold the first metatarsal rigidly enough) or by using appropriate screws as temporary (16 weeks) internal fixation. Postoperatively, partial weight bearing for 6 weeks is recommended, followed by a walking cast for 4 to 6 weeks thereafter. Combinations with lower leg, calcaneal, or ankle fractures are common, and, most importantly, the risk of compartment syndrome is substantial. Intracompartmental pressure measurements are mandatory, and when indicated fasciotomy should be performed without delay. Provided that the injury is closed and reduction/fixation is adequate, the prognosis is good. If good primary reduction is achieved, later degenerative arthritis may
occur but is surprisingly benign and nonsymptomatic. However, open injuries and inadequate reduction most often lead to unsatisfactory end results.
MTP sprains and dislocations Repetitive hyperextension loads on the first MTP joint predisposes to injury on the plantar aspect of the capsule around it. Alternatively, the dorsal aspect of the joint is sprained after a hyperflexion event. The clinical picture consists of local pain, tenderness, and swelling. In grade III injuries, stability is compromised, and osteochondral damage is occasionally seen. Treatment of MTP sprains is normally nonoperative. Ice, compression, and elevation are used acutely. Initial immobilization is required with weight bearing as tolerated, but even then the recovery time is often longer than 10 weeks. Whereas NSAIDs are beneficial for pain control, injections of local anesthetics or steroids are potentially aggravating to the injury and should be avoided. A plantar orthosis (steel or Orthoplast®) limiting dorsiflexion of the first MTP joint is used during rehabilitation. Surgical capsule repair and removal of loose bodies is only occasionally indicated. Strenuous activities such as running and jumping are resumed only after the patient is asymptomatic. Forced hyperextension of the MTP joints beyond physiologic limits may lead to rupture of the plantar plate either through the sesamoids as fractures or proximally. The latter is irreducible because of blocking from the plantar plate. Reduction is performed with a transverse plantar incision over the prominent metatarsal head. Great care must be taken not to sever the plantar digital nerves. The dislocation is reduced by grabbing the torn end of the plantar plate and manually relocating the phalanx to its normal position. Once reduced, the joint is usually stable. Postoperatively, a cast is worn for 4 weeks with weight bearing as tolerated. Dislocations with sesamoid fractures are usually readily reducible by closed means. MTP joint dislocations of the lesser toes can typically be reduced by closed means. Once reduced, the joint is usually stable, and crossover taping is sufficient.
Metatarsal fractures Soft tissue coverage of the dorsum of the foot is thin, vulnerable, and suboptimally supplied with blood. Strong ligamentous connections are present between the metatarsal necks distally and strong bands between the bases except the first and second, where the soft tissue connection is located between the second base and medial cuneiform. Common in industry, the injury often results from a direct blow to the dorsum of the foot caused by a heavy object. Shoes with steel-reinforced toe boxes protect the toes but not the metatarsals. Direct force on the metatarsals usually results in transverse neck fractures of the second, third, and/or fourth, whereas indirect force leads to spiral shaft fractures. The common plantar flexion-inversion trauma results in a fifth metatarsal base fracture. After severe injuries to the midfoot, compartment pressures in the foot should be carefully monitored and fasciotomy performed when indicated.
Chapter 8d
Treatment of nondisplaced fractures affecting the lesser metatarsals includes the use of a firm metatarsal pad, circumferential taping, and a firm boot with a crepe sole. Undisplaced fractures through the first metatarsal require a carefully molded non–weight-bearing short leg cast for 2 weeks followed by progressive weight bearing as soon as tolerated. In the treatment of displaced fractures, sagittal-plane displacement inevitably leads to altered weight distribution across the forefoot and should be avoided. Normally, the load on the first metatarsal head is twice that of any of the others (including the fifth), and moderate frontal-plane displacements are not as critical. Displaced first metatarsal fractures are best treated with open reduction and internal fixation. Chinese woven wire traps can be used to distract the hallux longitudinally and aid reduction. An elastic bandage around the ankle can be used for countertraction. It is crucial to regain length. The metatarsal is then temporarily transversely transfixed to the second ray. If possible, rigid internal fixation is used; if not, multiple pins are used to secure the fractures. If the fracture is open and major soft tissue problems are present, wound care is possible only through the use of external fixation of the fracture. With only one displaced metatarsal fracture, closed reduction is attempted. If successful, 6 weeks of non–weight-bearing casting follows. With multiple fractures, surgical fixation using either screws and plates or intramedullary retrograde pinning is recommended. Casting is unnecessary after stable internal fixation. With fractures through the metatarsal neck, closed reduction is virtually impossible, and fixation with Kirschner wire is commonly used. Work that involves much walking after midtarsal injuries may often require a long recovery time. These injuries are often either missed or contribute to secondary problems, and a treatment time of 3-6 months is frequently required. It is of greatest importance to secure a correct diagnosis early to provide optimal treatment and facilitate early return to work.
FOREFOOT PROBLEMS Hallux rigidus Hallux rigidus is stiffness of the hallucal MTP articulation, usually secondary to arthrosis of the joint. The etiology can be (1) juvenile hallux rigidus secondary to osteochondritis dissecans of the first metatarsal head in some cases; (2) gout, especially in bilateral hallux rigidus in men; (3) posttraumatic arthrosis of the joint; and, (4) most commonly, idiopathic arthrosis of the joint, primarily in middle-aged women, with or without the presence of a hallux valgus. Radiographs reveal a crown of osteophytes on the dorsal part of the metatarsal head and around the proximal part of the proximal phalanx. Local pain and tenderness with a varying degree of ROM restriction is clinically evident. Treatment is initially nonoperative: rest, ice, NSAIDs, and shoes with stiff rocker-bottom soles. Steroid injections are often beneficial. In contrast to a true metatarsal bar, the metatarsal rocker bar is curved rather than flat. It should never be put proximal to the MTP level because it would then only accentuate the bending of the sole. A combination with moderate heel elevation is often beneficial to rocker-bottom sole function.
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Persistent pain when pushing off is a problem for many patients, who therefore ask for surgery. A number of surgical procedures are available to treat hallux rigidus including: removal of osteochondrotic loose bodies, removal of osteophytes, wedge osteotomies, Keller procedure, arthrodesis, and Silastic implants. For very demanding patients, however, arthrodesis is often preferred and is the treatment of choice today. The Keller procedure (extirpation of the base of the proximal phalanx) potentially results in a short unstable great toe that would impair push-off ability. Silastic implants are contraindicated because of synovitis and even implant breakage after strenuous loading. Other interposition arthroplasties are currently evaluated in clinical studies. Because to date there is no optimal treatment for every patient with hallux rigidus, individual solutions must be sought. After surgery with arthrodesis, return to a desk job is often possible within a week. Return to work that involves walking requires 3 to 6 months of healing and rehabilitation.
Hallux valgus Patients with hallux valgus and bunions invariably have pronation deformities causing lateral pressure on the hallux. As it is forced laterally, the medial portion of the first metatarsal head is uncovered and forms most of the dorsomedially directed bunion. The extensor hallucis longus tendon pull is displaced laterally, further accentuating the hallux valgus deformity. The incidence of hallux valgus is much greater in women than in men, probably partly because of the use of high-heeled and pointed-toe shoes. Patients seek help because of recurrent pain/tenderness over the bunion or because of cosmetic problems and difficulties in finding appropriate shoes. Objectively, both the longitudinal and the transverse arches are insufficient. A very broad splayfoot is sometimes seen. The bursa over the bunion may be intensely inflamed: red, hot, swollen, and very tender. The great toe is angled laterally and may even be overriding or underriding the second and third toes. A hammer toe deformity of one or more of the lesser toes is often present. In most patients, management of hallux valgus is nonsurgical. Orthotics correcting arch insufficiency are most beneficial, and shoe modifications are in order. It is crucial to relieve pressure on the bunion; a ring-shaped pad around it is sometimes helpful. Indications for surgery can vary and include a valgus angle of more than 15 degrees, toes lying on top of each other, recurrent painful bursitis, painful calluses, or inability to wear shoes. A great number of surgical procedures address bunion and the angular deformity. After surgery, return to work depends on the technique used. After a simple bunionectomy, it is possible to return to work within 4 to 6 weeks. If an osteotomy is carried out, return to walking work is not possible until a healing time of 3-5 months has elapsed.
Hammer toes Characterized by hyperflexion of the proximal interphalangeal joints, hammer toes may develop secondary to collapse of the transverse arch of the forefoot. Painful corns on the dorsum of
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the proximal interphalangeal joints develop. If joint range of motion is unaffected, conservative treatment is advocated, including an arch-correcting orthotic, adequately roomy shoes, possibly toe manipulation to maintain mobility, and strapping of the toe in extension. If the toes are hyperflexed and restrict walking or if major corns and callosities are causing pain, surgery is indicated. With established flexion contracture of the proximal interphalangeal joint, excision of the distal end of the proximal phalanx is often gratifying. In early stages when flexion contracture is redressable, a flexor tendon tenotomy through a minimal incision under local anesthesia usually is enough and requires no or minimal postoperative recovery. Return to work is often possible 1 month after hammer toe surgery.
The sesamoids The sesamoids are two bones located on the plantar aspect of the hallucal MTP joint. The medial sesamoid is somewhat larger and bears more of the load, whereas the lateral sesamoid lies toward the first web space. From several ossification centers, the sesamoids ossify in early childhood. Partition is common, however, with 10% of the population having bipartite sesamoids (unilateral in 75% of those but bilateral in 25%; 15% having an interphalangeal sesamoid as well). The sesamoids have articular facets located superiorly toward the metatarsal head. The facets are enclosed in the joint capsule, and the remainder of the sesamoids is embedded in the flexor hallucis brevis tendons. The flexor hallucis longus tendon passes between the sesamoids. Injury mechanisms result from a direct blow caused by a fall from a height, typically resulting in a comminuted fracture, or forced hyperextension of the hallux leading to avulsion (transverse) fractures of the sesamoid. Such patients typically have a dislocated first MTP joint. Stress fractures are increasingly common, specifically in competitive athletes involved primarily in running or dancing. It is often very difficult to distinguish a stress fracture from a bipartite sesamoid. Radiographs (anteroposterior, lateral, and axial tangentials of the sesamoids, not the entire foot) may show smooth or irregular edges. A stress fracture is often undetectable on initial plain x-ray films. A bone scan shows increased uptake in stress fractures but possibly also in sesamoiditis. To further complicate the picture, osteochondral lesions of the sesamoid have been described also. As opposed to sesamoid fractures resulting from a single traumatic event, sesamoid stress fractures seem to have poor healing potential. The fracture will not heal despite 6 weeks of casting and months of activity restriction. Excision is recommended, with potentially good results. Successful surgery, however, requires very careful technique to avoid the introduction of disabling complications such as neuromas, hallux valgus/varus, or cock-up deformity.
A common predisposing factor to metatarsalgia is altered forefoot biomechanics, extrinsic or intrinsic, caused by the following: ● High-heeled shoes, which significantly alter the load from the hindfoot to the MTP region; ● Equinus foot, especially when caused by a tight heel cord and/or anterior impingement of the ankle, thereby preventing ankle dorsiflexion; ● Cavus foot, where support is maintained only by the metatarsal heads and the heel (and not also by the lateral longitudinal arch), resulting in overload of the forefoot; ● Irregular distribution of load between the metatarsal heads. In the static standing position, all metatarsal heads bear load, the first metatarsal head bearing double the load of the others. In the dynamic take-off phase of walking and running, this relative first ray overload is even more evident. A disturbance of this load distribution between the metatarsals may be caused by an abnormally short or hypermobile first ray or by a long second metatarsal. With a hypermobile first metatarsal, a significant part of the load is transferred to the second and third rays. In most cases, treatment is conservative. Supporting orthotics that relieve the overload on the metatarsal heads are often beneficial. With a hypermobile first ray, a pad is tried just proximal to the second and third metatarsal heads and/or underneath the first ray. Stretching a tight heel cord is essential. If significant discomfort persists in spite of adequate orthotics and flexibility treatment over a 6-month period, surgery must be considered. Here soft tissue and skeletal corrections may be indicated. Capsulitis of the second MTP joint is related to hallux valgus, a condition in which the hallux forces the second toe to sublux dorsally. Tenderness over the dorsal capsule and pain on passive dorsiflexion of the second MTP joint is diagnostic. Typically, no interdigital pain or tenderness is present. Strapping of the second toe in a reduced plantar-flexed position is usually helpful. Rarely an extensor tenotomy, with or without capsulotomy, is required.
SKIN CONDITIONS Corns Soft corns are interdigital clavi formed between toes as a result of pressure between adjacent phalangeal condyles. Hard corns represent accumulations of keratin layers of skin, typically on the dorsum of the toes, to prevent ulceration of the skin from chronic pressure that is usually extrinsic. Relief of this pressure is the key to successful treatment. The corn should be softened and pared judiciously. Occasionally, surgical removal of intrinsic pressure is necessary, for example, with a prominent phalangeal condyle, a hammer toe, or a hallux valgus.
Calluses Metatarsalgia Metatarsalgia, or pain in the MTP region, is a condition with many possible causes. Hallux rigidus, sesamoiditis, stress fractures, and Morton’s neuralgia are discussed elsewhere in this chapter.
Calluses are hyperkeratotic lesions similar to corns that form on the plantar aspect of the foot after weight-bearing and shearing forces. Typical lesion areas are under the metatarsal heads and under the heel. Underlying structural deformities such as an
Chapter 8d
insufficient transverse arch, forefoot varus or valgus, a plantarflexed first ray, or a long second ray are common. Local treatment of calluses equals that of corns; custom-made orthotics are generally needed. If these measures prove insufficient, a rare event, surgical correction of an underlying deformity must be considered. The diagnosis of a cutaneous lesion is sometimes difficult. Scar formation, warts, inclusion cysts, and foreign body inclusions all may have the appearance of a corn or a callus. A careful history, clinical examination, and occasionally soft tissue radiographs are needed. In doubtful cases, referral to a highly specialized institution without touching the lesion is indicated.
Warts (Verrucae vulgares) A wart is the result of a papillomavirus infection that is transferred between individuals in showers, saunas, and locker room floors. The incubation period is 1-6 months. Typically located on the sole of the foot, the warts are round or oval and gray-white, have a crack or a dark spot in the center, and are often tender to pressure. They are commonly multiple. Primary plantar wart treatment consists of weekly paring and application of keratolytics (including 50% trichloroacetatic acid or 40% salicylic acid). Failure of this treatment to eradicate the wart may warrant the use of careful electrosurgery after infiltration of local anesthetic with epinephrine. We advise against excision of a wart by scalpel or curet because of the risk of scar formation from inadvertent penetration of the basilar layer of the skin. When all else fails, x-ray therapy may be considered provided that it is given by an experienced operator. Prevention is crucial, and the use of bath shoes in humid areas is strongly recommended.
Blisters Blisters result from shearing irritation of the skin typically caused by the improper fitting of shoes and/or socks. The epidermal layers split, and the cavity formed is filled with a clear fluid. Treatment consists of prompt removal of extrinsic irritant and if needed, clean aspiration of the fluid. Deroofing the blister should be avoided because the overlying skin is a good dressing and helps prevent secondary infection.
Fungal infections (Tinea pedis) Occasionally referred to as “athlete’s foot,” fungal infections may develop in circumstances where foot hygiene is inadequate. The most common infecting organisms are Trichophyton rubrum and Trichophyton mentagrophytes. Tinea pedis exists in both “dry” and “wet” varieties. Predominant sites of infection are the web spaces. The dry form appears as gray-white scaling of the skin, whereas in the wet vesicular form, the web space skin has a macerated appearance. Diagnosis can be made by revealing hyphae and mycelia by light microscopic examination of scrapings from scaling and vesicle walls. Treatment of the dry form of tinea pedis consists of local antifungal spray, whereas the wet form is best treated with potassium
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Nails
permanganate or silver nitrate. A secondary bacterial infection may necessitate erythromycin administration. Prevention such as good foot hygiene, including frequent change of socks; shoes allowing adequate aeration; and avoidance of barefoot walking in locker rooms is essential.
NAILS Ingrown toenails Ingrown toenails are common and potentially disabling. Posttraumatic nail deformation caused by injury of the nail matrix may elicit the problem. The shape of toenails is congenitally different, with some types being flatter whereas others are folded. Frequently, the lateral and medial edges of a folded toenail conflict with the adjacent nail. The problem grows when external pressure is increased from a tight sock or a shoe with a narrow toe box. If the edge of the nail penetrates the skin, bacterial infection and voluminous granulation tissue result. The condition, which is most painful, typically engages the lateral aspect of the great toe, but any toe could be affected. Prevention is essential and includes good foot hygiene, properly fitting footwear, and appropriate nail trimming habits. Once a week the nails should be cut transversely because they may grow down into the nail fold if cut to a rounded outline. Once established, the acute-phase infection should be drained and the area soaked in an antiseptic solution followed by a dry cover. Surgery should be avoided in the acute phase because of the high risk of postoperative infection, including potential osteomyelitis. In chronic cases, the ingrown part of the nail, including the nail matrix of that part, should be surgically removed. At least 3 weeks should be allowed for healing postoperatively. After surgery for ingrown toenails, return to work is possible in 3-6 weeks. These conditions are painful.
Subungual hematomas (Black nail, “Tennis toe,” “Soccer toe”) Bleeding of the nail bed can be the result of a direct blow to the nail from being trodden on or from a toe box that is too narrow. The hematoma shines through the nail and renders it black or dark blue. The condition may be very painful in the acute stage. The hematoma is evacuated through a small hole through the nail made with a red-hot straightened paper clip or similar tool. Most often painless, the procedure gives immediate relief and preserves the nail, which would otherwise fall off after 2-4 weeks because of disruption of its blood supply.
Subungual exostosis As a result of repetitive direct blows such as a basketball player’s forefoot repeatedly being trod upon, reactive exostosis formation may develop on the dorsal aspect of the outer phalanx of the toe underlying the nail. Intense tenderness prompts treatment, typically nail removal and occasionally removal of the exostosis as well.
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Fissures
4. 5.
Very painful and most disabling, fissures of the weight-bearing area of the sole are correlated mainly with hyperkeratosis but are seen also in conjunction with psoriasis, fungal infection, obesity, and shoes without counters. Hyperkeratosis-related fissures are treated with topically applied salicylic acid. Steroid ointments or creams might be added for a limited time. A concomitant fungal infection may need oral antifungal treatment.
6. 7.
8. 9. 10.
Fungal nail infections Fungal infections of nails respond to oral antifungal treatment only. Treatment typically must extend beyond 3 months. Because oral antifungal drugs may be liver toxic, liver function needs to be monitored. In some instances it may be reasonable to refrain from treatment.
REFERENCES 1. 2. 3.
Allenmark C: Partial Achilles tendon tears. Clin Sports Med 11(4):759-770, 1992. Baxter DE, Thigpen CM: Heal pain, operative results. Foot Ankle 5(1):16-25, 1984. Broström L: Sprained ankles. V. Treatment and prognosis in recent ligament ruptures. Acta Chir Scand 132:537-550, 1966.
DeLee JC, Evans JP, Julian J: Stress fracture of the fifth metatarsal. Am J Sports Med 11(5):349-353, 1983. Kannus P, Renström P: Treatment for acute tears of the lateral ligaments of the ankle. J Bone Joint Surg 73A:305-312, 1991. Komprda J: Le syndrome du sinus du tarse. Ann Podol 5:11-17, 1966. Leach RE, Schepsis AA: Acute injury to ligaments of the ankle. In CM Evarts, ed: Surgery of the musculoskeletal system, Vol. 4. New York, 1990, Churchill Livingstone International, pp. 3887-3913. Pettine K, Morrey B: Osteochondral fractures of the talus. J Bone Joint Surg 69B(1):89-92, 1987. Renström P, Kannus P: Management of ankle sprains. Oper Techn Sports Med 2(1):58-70, 1994. Styf J: Entrapment of the superficial peroneal nerve: diagnosis & results of decompression. J Bone Joint Surg 71B:131-135, 1989.
SUGGESTED READINGS Coughlin MJ, Mann RA: Surgery of the foot and ankle, ed 7. St. Louis, 1999, Mosby. Greer Richardson E, ed: Orthopedic knowledge update: foot and ankle 3. Chicago, 2004, American Academy of Orthopedic Surgeons. Hansen ST: Functional reconstruction of the foot and ankle. Philadelphia, 2000, Lippincott Williams & Wilkins.
CHAPTER
8e
Adaptation of Workers with Foot and Ankle Disorders to the Workplace: Case Studies Mooyeon Oh-Park, Dennis D. J. Kim, and Peter Sheehan
Treating injured workers is a challenging task for most clinicians, especially given the fact that a significant number of workers may not be able to return to work even after successful medical or surgical treatment of injury. In addition, patient care is complicated by other factors, including the level of patient motivation to achieve full recovery, the system of compensation and disincentives, and the influence of legal counsel. Despite these challenges, clinicians are often relied on to treat functional impairment and subsequent disabilities to achieve the goals of care for injured workers: restoring function and timely returning to work after successful treatment of the underlying pathology. Although extensive information regarding the treatment of foot and ankle pathologies is available in the literature, little has been described about the types of measures necessary to minimize deleterious functional impairment on return to the workplace.
Table 8e.1
In this chapter, we first describe the biomechanical demands of the foot and ankle in the workplace and specific anatomic and physiologic deficits after foot and ankle injuries. Then we describe how the disabilities from foot and ankle injuries may be reduced by various adaptation processes such as ergonomic modification, adaptation of work activity procedures, and the appropriate utilization of footwear and orthoses. The adaptation process begins by identifying the main deficits of the worker that led to the impairment and subsequent disability. Evaluation of workers consists of gait examination, range of motion (ROM) of individual joints, manual muscle testing, proprioceptive sensation, and examination of footwear. It is important to note that biomechanical derangement of the foot and ankle inevitably influences knee, hip, and low back proximally because the foot and ankle are the terminal parts of the closed kinetic chain providing the base of support.32 Clinicians therefore need to evaluate the entire lower limb as one biomechanical unit. The ROM of individual joints should be assessed considering the functional demands of the specific work activities described later in this chapter. Footwear and orthoses play an important role in management of foot and ankle disorders (Table 8e.1). When treating a working population, clinicians should take work activities into consideration in prescribing footwear or orthoses because certain appliances may interfere with work activities despite providing excellent symptom relief. Solid plastic ankle foot orthoses (AFOs), for example, may relieve the pain of the worker with posttraumatic ankle arthritis but greatly interferes with work activities such as kneeling, crouching, or fast walking. In this situation, an articulated AFO with limited ROM or a leather anklet would be a better
Clinical indications and function of footwear modifications
Type of modification Cushion heel Beveled heel Rocker sole
Toe spring Rigid sole (steel shank) Removable rigid insole (carbon plate) Heel lift
Clinical indications
Simulated function
Advantages and limitations
Limited ROM of ankle PF Ankle fusion, arthritis Same as cushion heel
Simulates PF of ankle, reduces the kinetic demand on ankle dorsiflexors Same as cushion heel, delays initial contact during gait Reduces dorsiflexion of 1st MTPJ, reduces pressure on metatarsal head, simulates DF of forefoot
Relatively costly
Limited ROM of ankle DF Ankle fusion, arthritis Hallux rigidus/limitus Hallux limitus Pain or instability of midfoot Hallux limitus Painful instability of midfoot Hallux limitus Equinus deformity of forefoot Equinus deformity of ankle
Simulates DF of forefoot Stabilizes the midfoot, reduces DF of 1st MTPJ Stabilizes midfoot, reduces DF of 1st MTPJ Accommodates ankle equinus and forefoot equinus
DF, dorsiflexion; MTPJ, metatarsophalangeal joint; PF, plantar flexion; ROM, range of motion.
Relatively inexpensive Heavy, may affect balance, requires rigid sole
Does not require additional modification of footwear, lightweight Caution in diabetic patients, heavy Caution in diabetic patients, lightweight, can be inserted in footwear >1/4” heel lift usually needs to be placed on the outsole of footwear, footwear with high top design is preferable
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option than a solid AFO because it allows a considerable amount of motion. Many injured workers may experience unexpected functional impairment after resuming their work activities. Work-simulation and work-hardening sessions incorporating the adaptation process are often necessary to provide injured workers an opportunity to assess their ability to return to work.
BIOMECHANICAL DEMANDS OF THE FOOT AND ANKLE IN THE WORKPLACE Knowledge of biomechanical demands of the foot and ankle in the workplace enables clinicians to prepare the necessary adaptations when returning injured workers to their duties.
Common work activities
Walking About 10 degrees of ankle dorsiflexion with the knee in extension is required for normal walking.40 If a worker has limited ankle dorsiflexion secondary to contracture or pain, the tibia cannot advance forward during the stance phase. Compensatory motions such as hyperextension of the knee, early heel rise, excessive pronation of the subtalar joint, or shortened step length on the contralateral side are therefore noted during gait.
SPECIFIC DEFICITS AFTER FOOT AND ANKLE INJURIES After foot or ankle injuries, workers may have impairments related to abnormal ROM of specific joints, neurologic deficits, pain, edema, or any combination of these problems even after initial medical and surgical interventions. The functional impact of these deficits is described in this section.
Floor-to-waist lifting Floor-to-waist lifting in full squat position requires maximum ankle dorsiflexion and transfer of the center of body forward, especially when lifting an object without a handle. Because workers with lack of ankle dorsiflexion range are unable to perform full squats, they often compensate by flexing the hip and the spine. Because of an increased lever arm between the load and the lumbar spine, this lifting technique increases the demand on back extensors. Workers need to take special precautions to maintain lumbar lordosis as much as possible during lifting to protect their backs from injury.22
Carrying a load According to one biomechanical study, carrying a load on the side of an affected hip exerts less stress on it than carrying a load on the contralateral side.29 However, there are no studies available regarding whether this same principle can be applied to patients with foot or ankle disorders. Carrying a load on the opposite side of injury theoretically increases the moment arm of the load and may place additional stress on the affected ankle and foot. By reducing the moment arm of a load, however, carrying it on the side of injury may change the angle of weight bearing, causing stress on the lateral side of the ankle. Workers therefore usually find themselves using the side that produces fewer symptoms.
Kneeling Kneeling is defined as supporting the body weight on both knees, a position requiring nearly full ankle plantar-flexion. Workers who lack full plantar-flexion range may compensate with hyperextension of the metatarsophalangeal (MTP) joints and slight ankle plantar-flexion.
Crouching In crouching with one knee up and one down, the worker needs full ankle dorsiflexion in the forward limb. Without ankle dorsiflexion, he or she can compensate with external rotation of the hip and eversion of the subtalar joint. The backward limb with the knee in contact with the floor requires full plantar flexion of the ankle; otherwise, the worker can compensate with slight plantar flexion and MTP hyperextension.
Abnormal ROM Pain-free normal ROM of the ankle, subtalar, midtarsal, and first MTP joints are prerequisites for normal function of the foot and ankle. Limited and excessive ROM of these joints interferes with normal gait and work activities. When excessive ROM of a certain joint is noted during evaluation, the clinician should differentiate the causes for excessive ROM, distinguishing a structural instability from a compensatory response for limited ROM of the other joints. The pain associated with excessive ROM can be improved by wearing footwear or orthoses designed for the control of excessive motion.
Equinus of the ankle (limited ROM of ankle dorsiflexion) Equinus deformity of the ankle is a common abnormality after foot and ankle injuries. Frequently seen also in patients with spastic gastrocsoleus muscles from various neurologic disorders, it has a profound effect on the entire lower limb during closed kinetic motion. It affects proximal joints, especially driving the knee joint into hyperextension during weight bearing, and distal joints, as is seen with excessive pronation of the subtalar and midtarsal joints.6 Long-standing excess pronation leads to painful arthrosis in these joints and may cause a rotatory stress to the knee joint at the same time. Finally, patients may compensate for the deformity by externally rotating their lower limbs, thus shortening the lever arm for the ground reaction force. This compensatory gait may be necessary for the patient to accommodate the functional deficit in the workplace, although this gait deviation may cause pain or instability of the medial knee later. In this instance, the clinician should weigh the benefit and the potential harm of the deviation before correcting the gait.6 To manage equinus deformities, clinicians should emphasize preventive measures, including early weight bearing, preventive orthoses, and physical therapy. Physical therapy should initially be instituted under the supervision of a therapy team so the patient can properly learn heel cord stretching exercises before continuing them at home. The patient’s foot should be placed in
Chapter 8e
neutral or slightly supinated position during this exercise to avoid undesirable stretch of the midfoot instead of the heel cord. To avoid its profound effect on the lower limb, equinus deformity can be accommodated by a heel lift inside (up to 1/4-inch heel lift) or outside (higher than 1/4-inch lift) the footwear. Footwear with high-top design may accommodate a heel lift of up to 3/8 inch. The heel lift should be lowered gradually to avoid development of pain in the calf or other proximal parts of the body that can occur from abruptly changing the height. Forefoot equinus is a deformity of the plantar-flexed forefoot relative to the hindfoot that is often mistaken for the ankle equinus deformity. Etiologies of the acquired forefoot equinus include posterior compartment syndrome, nerve injury, or surgery. Workers with forefoot equinus may complain of pain on the anterior ankle or posterior knee due to compensatory dorsiflexion of the ankle and hyperextension of the knee on weight bearing. Because the ankle is already in maximum dorsiflexion, further stretching of the gastrocsoleus muscle may exacerbate the ankle and knee pain further. In this instance, a heel lift in high-top footwear can accommodate the deformity if surgical correction is not contemplated.
Calcaneocavus (limited ROM of ankle plantar flexion) A patient may develop limited ankle plantar flexion after rupture of an Achilles tendon, after fractures of the ankle or hindfoot, or as a neurologic sequelae.10,28 Management of this deformity is often much more challenging than that of equinus deformity. Workers experience excessive knee flexion during weight bearing, resulting in increased work demand for the knee extensors. Over a period of time, workers may develop painful knee conditions such as patellofemoral stress syndrome. Excessive stress on the heel during the early stance phase of gait causes pain, callus, or ulceration around it. High-top footwear with a silicone heel cup is often helpful to reduce the callus formation and heel pain.
Limited ROM of ankle plantar flexion and dorsiflexion and ankle arthrodesis Injury or a subsequent surgical procedure such as arthrodesis may result in marked restriction of ankle dorsiflexion and plantar flexion. As mentioned earlier, lack of ankle motion results in marked change in gait and may cause abnormal compensatory motions of the adjacent joints. Clinicians should be aware of possible modifications of footwear that can compensate for lack of motion in the ankle, which in turn can improve gait and halt abnormal compensatory motions. A cushioned or beveled footwear heel, for example, simulates plantar flexion and thus assists initial contact and loading response of the gait. A rocker sole or a toe-spring also can be used to correct the impaired dorsiflexion of the ankle, thus improving the late stance phase of the gait. Ankle ROM abnormalities are often seen after surgical interventions. Ankle arthrodesis is performed for comminuted fracture, nonunion, or posttraumatic arthritis. The general recommendation for the ankle position for arthrodesis is neutral (90 degrees). Postprocedure, these patients may have abnormal flexion momentum of the knee when wearing footwear because most footwear have heels at least 1/2 - 3/4 inches high that tilt the tibia forward.
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Specific deficits after foot and ankle injuries
Figure 8e.1
Rocker sole.
Patients therefore need to choose footwear with lower heels to minimize the abnormal knee flexion momentum that may cause painful knee conditions over time. Arthrodesis of the ankle in plantar flexion is not recommended because of possible development of painful subtalar and midtarsal arthrosis later on.9 An ankle fused in slight plantar flexion can be accommodated with footwear with a heel lift, although there is no study available investigating the long-term effect of such modifications after arthrodesis.
Hallux limitus Limited motion of the first MTP joint occurs after forefoot injury or arthritis secondary to a collapsed medial arch. Compensatory gait patterns such as external rotation of the entire lower limb or lateral toe break during push-off are frequently observed among such workers. Rocker-sole and steel-shank footwear are commonly recommended for workers with painful ROM of the first MTP joint (Fig. 8e.1). This modification, however, makes the footwear heavy and may not be appropriate for patients whose balance is impaired by the reduced area of support. Footwear with a toe-spring design can be used without the additional weight of a rocker sole and usually does not affect balance.
Neurologic deficit Weakness of ankle dorsiflexors is one of the most common neurologic deficits affecting the foot and ankle. Various etiologies causing this weakness include peripheral nerve injuries, plexopathy, lumbosacral radiculopathy, and compartment syndrome as well as central nervous system disorders. Many workers with isolated weakness of ankle dorsiflexors are able to return to work with proper orthotic management even if neurologic recovery is not complete. Ankle dorsiflexors contract eccentrically during the early stance phase for loading of the foot and contract concentrically during the swing phase for the leg to clear the ground. Footwear with high-top designs and elevated heels reduce this biomechanical demand of ankle dorsiflexors and minimize the need for heavy bracing. High-top athletic footwear or boots with a 1/2-inch heel lift are often sufficient for workers with minimal weakness,
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especially when early neurologic recovery is anticipated. This approach, however, may cause development of a tight heel cord over time, so workers should be educated to perform exercises to stretch it. For workers with significant weakness, a posterior leaf-spring orthosis can be used inside the footwear. Posterior leaf-spring orthosis is a good choice because it is lightweight, flexible, and aesthetically favored by wearers. For workers with severe sensory loss, deformity, or fluctuating edema, a conventional AFO with a double upright and protective insole is recommended. Workers with a combined weakness of ankle plantar flexion and dorsiflexion generally require more restrictive orthoses. As with workers whose ankle dorsiflexion alone is weak, footwear with high-top design and elevated heel confines the ankle and minimizes the need for heavy bracing. Molded ankle orthoses such as the Arizona or Baldwin AFO are available, although they tend to be more costly and bulky and may require footwear in a large size. Semisolid or solid AFOs restrict ankle motion and interfere with work activities, so clinicians should be cautious in prescribing these restrictive orthoses for the working population. Significant sensory loss can occur after nerve injury or neuropathy from medical diseases such as diabetes mellitus. Compensation for sensory deficit is not possible, and it is more difficult to manage than muscle weakness. Some workers develop neuropathic discomfort, balance impairment due to poor proprioceptive feedback, or ulcerations in the foot. A lightweight AFO with a wide calf band and semirigid ankle design may provide some proprioceptive input from the floor to the more proximal leg for balance. For ulceration of the insensate foot, attentive wound care is essential, as described in a later section.
Foot and ankle pain Pain is a major reason that workers cannot return to work and seek medical attention. When pain is the main deficit causing disability, evaluation of injured workers is a challenging task. Workers may experience persistent pain from subtle minor injuries even after the obvious injuries are treated. This residual pain from subtle injury can easily be misinterpreted as a psychologic etiology, although workers are in fact suffering from real structural problems. Minor injuries can initiate symptoms in previously degenerated yet asymptomatic structures, causing etiologic confusion for clinicians. In this section, general principles of how to approach workers with foot pain are described. Diagnosis and surgical treatment of individual pathologies are not discussed in this chapter. Precise history taking provides clues for the nature of pain and guides the direction of treatment. If the pain is markedly exacerbated by ambulation as compared with quiet standing, proper control of the painful motion would be the main direction of management regardless of etiologies. Application of several layers of Unna’s paste bandage and footwear with a rocker sole and cushion heel may provide relative immobilization of the ankle in the initial phase of the treatment. This is a useful temporary trial before prescribing definitive orthosis for control of ankle motion. Pain may also present during specific ROM of joints. For example, workers with anterior impingement of the ankle experience pain from its dorsiflexion. A heel lift and rocker sole reduces the demand for ankle dorsiflexion and may provide
pain relief. An orthosis controlling the ankle dorsiflexion is bulky and difficult to use in the workplace. It is not uncommon for workers to experience pain in locations different from those of the injured structures. Patients with hallux limitus or plantar fasciitis may develop lateral foot pain from walking on the lateral foot to avoid weight bearing on the painful medial side (lateralization of pain). In other cases, the location of the discomfort may change as the disease progresses. A patient with tibialis posterior tendon insufficiency, for example, may develop pain on the lateral hindfoot at a later stage as the pronation deformity progresses even though the pain was initially on the medial side. This lateralization of pain may confuse clinicians attempting to diagnose and treat the primary pathology.
Case: Burning pain around the medial ankle A 45-year-old electrician in a large city hospital presented with burning pain on the medial side of the right ankle. Pain was more prominent when standing and was relieved by sitting. The patient had sustained a right Achilles tendon rupture and subsequent surgery at the age of 22 from a work injury and had equinus deformity of the right foot. On physical examination, Tinel’s sign was present on the medial side of the ankle. An electrodiagnostic for tarsal tunnel syndrome was negative. Because of the tight heel cord, significant pronation was noted on the right side on weight bearing. A tender point reproducing the symptom was identified along the location of the saphenous nerve. The patient was diagnosed as having a saphenous neuroma near the old operation scar aggravated by pronation of the foot. A detailed history revealed that the patient had recently changed his working boots to low-heeled athletic footwearthat stretched the saphenous nerve due to compensatory pronation for his tight heel cord. The patient’s pain wassignificantly reduced by 3/8-inch heel lifts placed inside the shoes, and he subsequently returned to work without any further intervention. The patient was instructed to wear his old working boots or basketball sneakers with elevated heels inside them.
Edema of the lower leg Persistent swelling of the lower leg may prevent patients from returning to work even after initial treatment is successful. In many instances, the edema is due to multiple factors, including residual inflammation, venous and lymphatic insufficiency, reduced elasticity of soft tissues, and dependent position of the legs.33 Provided that arterial supply is not compromised, compression treatment such as Unna’s paste bandage, elastic bandaging, and compression stockings is the mainstay of treatment. In particular, Unna’s paste bandage, a zinc oxide–impregnated nonelastic gauze, can be used as an effective initial treatment of edema (Fig. 8e.2). It does not yield circumferentially while the bandage remains in contact with the skin. This causes a compression force around the leg while its contour keeps changing with ankle motion, especially during ambulation. In so doing, the bandage acts like the natural pump of the calf muscle in
Chapter 8e
Figure 8e.3
Figure 8e.2
Unna’s paste boot bandage.
mobilizing interstitial fluid.23 The greatest advantage of the bandage is that of allowing the worker to return to standing activities while controlling the edema at the same time. Workers can wear regular footwear and continue to perform physical therapy with the bandage in place. Unna’s paste bandage is also inexpensive, readily applicable, and easily removable. During the application, it should be cut frequently and applied evenly in contact with the skin to avoid excessive constriction that may result in a local purpura or skin abrasion. To maintain its effectiveness, the bandage must be kept dry in the shower. As mentioned earlier, Unna’s paste bandage should not be applied to the patients with significant arterial insufficiency of the lower limb.
FOOTWEAR AT THE WORKPLACE Direct injuries to the foot and ankle form a substantial proportion of all reported occupational accidents. In addition, many injuries to other parts of the body result from slips, trips, and falls partially attributable to inappropriate footwear. Patients working in specific occupations are obligated to wear various types of safety shoes for protection from environmental hazards or injuries at the workplace. The special features, advantages, and potential problems of the safety footwear used in the workplace are reviewed in this section. Military shoes and footwear for women in the workplace are also described briefly.
Safety shoes Regardless of manufacturer, most safety footwear has common features such as a reinforced toe cap and steel plates for protection
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Footwear at the workplace
Safety shoes.
of the plantar sole (Fig. 8e.3). Further specialized footwear is available also to protect against cutting injuries or environmental hazards related to chemicals, extreme temperature, or electricity.12 Each country has different standards and methods of assessing the level of protection against various hazards for safety shoes. To assess the level of protection against impact to the toes, for example, the American National Standard Institute standards have a single pass-fail figure for all sizes of the footwear, whereas the European standards have a sliding scale that increases with footwear size.
Features of safety shoes The toes are most vulnerable to injuries and also the easiest to protect effectively with the least ergonomic penalty. Protective toe caps are a compulsory requirement of most safety footwear standards. For example, European standards for personal protective equipment require protection against 200 Joules for the toe area12 that is achieved mostly by a carbon steel toe cap. Plastic toe caps, however, are used in environments where metal cannot be used such as when handling munitions or inflammable chemicals. Protection of the plantar sole against penetration injury is provided by a stainless steel plate in the outsole layer. Material that resists penetration, strain, and corrosion is used to make a plate large enough to cover most of the plantar surface. Although penetration testing is standardized throughout the world, slight differences exist in the minimum permitted penetration force, which is 1100 N in Europe and 1200 N in the United States.12 Specific outsole materials are used in specific footwear for slip resistance. To secure the optimal effect of slip resistance, workers need to replace the footwear on a regular basis to avoid using worn outsoles. Currently, no method of testing is available for the durability of slip resistance. Prevention of slip injuries should involve measures such as educating workers, avoiding the use of floor polish, and abrading the outsoles of new footwear.25 Heat insulation is a special feature of safety shoes to prevent injury and discomfort for the workers standing on hot surfaces such as the tar used to pave roads. The outsoles of the footwear are produced from materials with a high melting point such as vulcanized rubber marked with the code “HI” (heat insulation).
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Adaptation of workers with foot and ankle disorders to the workplace: case studies
Potential problems of safety shoes Wearing safety shoes may cause several problems at the expense of protective features. One study showed that a high percentage of workers (91%) complained of foot problems caused or exacerbated by safety shoes.26 The common complaints were intolerable heat, inflexible soles, shoe weight, and pressure from steel toe caps. Workers wearing rubber boots in the meat packing or fishing industry may develop allergic reactions to the material or develop mycotic and bacterial lesions from plantar hyperhidrosis.4 Clinicians should be aware of potential foot problems related to the use of safety shoes in workers with certain medical conditions. Patients with diabetic neuropathy, for example, may develop ulcers on the dorsum of the toes or plantar forefoot from hard soles and steel toe caps. Unfortunately, there are not many choices in terms of the width and shape of safety shoes currently available. Workers with wide forefeet may settle for wearing larger sizes. In these instances, excessive room around the heel may cause undesirable slipping during ambulation. To compensate, a soft heel cup can be placed inside the footwear to provide a snug fit.
Case: Toe blisters from wearing safety footwear A 49-year-old man with a 10-year history of non–insulindependent diabetes mellitus presented with plantar ulceration at the right hallux (Fig. 8e.4). The patient was working as a housekeeper in a large municipal hospital. A few days before presentation, the patient had noticed a blood stain on his sock. He had recently changed footwear from athletic walking sneakers to safety shoes with hard soles and steel toe caps that had been given to him by a colleague at work. The patient developed blisters on the plantar aspect of the right hallux that had caused no discomfort because his foot was insensate from diabetic neuropathy. Treatment involved use of an Aircast walker with a thick insole and local relief. To prevent recurrence of the ulcerations, the patient was instructed to substitute orthopedic footwear with soft insoles for the safety shoes. He was placed in a job-retraining program also.
Figure 8e.4 Ulceration on the plantar aspect of hallux after wearing safety shoes.
Military shoes Military shoes merit discussion because they can cause significant morbidities in recruits who are expected to perform strenuous physical feats. Recruits can develop various foot and ankle injuries ranging from skin blisters to ligament sprains, tendonitis, and stress fractures. Continuous efforts have been made by the researchers in the field of military medicine to improve military shoes and reduce such injuries. One study of military shoes showed that three different widths for each shoe length were necessary to accommodate the feet of military recruits.14 Interestingly, this study also showed that choosing larger shoe sizes to accommodate the necessary width when appropriate widths were unavailable did not necessarily increase the incidence of overuse injuries.14 To reduce overuse injuries of the foot and ankle among military recruits, various insoles have been tried.17,41 One study indicated that to attenuate peak pressure during running and marching, Sorbothane is superior to other insole materials such as viscoelastic polymetric, polymetric foam, and Saran.41 Once worn out, these insoles lose their shock-absorbing ability,11 but custommade insoles have nevertheless been reported to decrease the incidence of stress fractures among military recruits.13,27 Additional appliances may help prevent ankle injuries or reduce the development of severe foot blisters. Ankle injuries are especially common during parachute training, accounting for 30% to 60% of all parachuting injuries. In one study, an ankle brace applied outside the boots significantly reduced ankle inversion injuries without increasing injuries to other parts of the body.2 Foot blisters are common and can be severe enough to require medical treatment. Knapik et al21 reported that the incidence and the severity of foot blisters can be reduced with dense woolpolypropylene socks combined with polyester liner as compared with standard military issued socks during training. Two layers of socks probably absorb the friction better than a single layer as this principle has been practiced in various sports activities.
Footwear for female workers Certain professions require female workers to wear footwear designed for the aesthetic features rather than for the health of the foot and ankle. Women’s high-heeled shoes, especially pumps, contribute to many problematic foot disorders including bunion formation, interdigital neuritis, metatarsalgia, hump pump, and tight heel cords. Most of these conditions improve with roomier footwear without extensive medical treatment. If employees are required to wear high-heeled shoes, they need to be educated to choose those with a proper wedge angle to reduce anterior slippage of the foot. Pumps without proper suspension require an extremely tight fit to prevent the foot from slipping out. High-heeled shoes with proper closure and suspension such as straps or laces are preferable to pumps because they do not need to fit tightly. Another common problem women tend to develop is pain in the calf and in other parts of the body when they have changed abruptly from high- to low-heeled shoes, possibly due to biomechanical compensation for tight heel cords.32 In such cases, a gradual change over several months to low-heeled shoes is generally recommended for patients whose heel cords are tight.
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Adaptations for common conditions
FOOT ORTHOSES
ADAPTATIONS FOR COMMON CONDITIONS
Foot orthoses (FOs) were introduced in the working population not only for foot and ankle problems but also for suprapedal conditions such as low back pain.19 Although literature is available regarding the application of FOs, there is no general consensus about the benefits of their use by workers. Application of generic foot insoles (orthoses) without consideration of the distinct abnormal biomechanics of each patient did not show consistent benefit. The goals of orthotic management in painful foot conditions are pain relief, accommodation of limited ROM, and restoring the normal alignment of the foot and ankle. Clinicians should keep in mind that foot pain can be relieved even without complete restoration of the normal alignment. Successful orthotic treatment depends on understanding the biomechanics of the foot and the suprapedal segment. Clinicians need to interrelate the patient’s biomechanical abnormalities and the design of FOs; they may consider trying temporary insole modifications before prescribing definitive FOs.
Although similar principles may be applied to other types of foot injuries, this chapter focuses on adaptation for the most common and troublesome conditions.
Preparatory trials If a patient’s discomfort improves with the preparatory trials of an insole such as posting, padding, or heel lifting, the clinician can feel confident that customized FOs with these features are beneficial. Because such FOs are highly costly and not always modifiable, clinicians should be familiar with the practice of using preparatory trials before prescribing them. Patients wearing FOs require regular follow-up, and depending on the material and their activity level, the FOs need to be replaced every 3 to 6 months. Details of different types of FOs are described under individual foot and ankle conditions below and later in this chapter.
Pronation control An FO for pronation control is designed to decrease rather than completely correct pronation.30 Because normal walking requires a certain degree of pronation, complete correction may cause pain in the lower limbs and back. Orthotic management for pronation control will not be successful if tight heel cord, a major biomechanical culprit for excessive pronation, is not addressed. Accommodation of tight heel cord with proper heel lift should be incorporated in the design of the selected FOs and shoes.
Supination control Workers with cavus foot are prone to stress fractures, heel pain, or lateral ankle sprains. FOs are often designed to reduce ankle inversion and to provide shock absorption. The medial arches of the FOs are built to accommodate the high arches of cavus feet. FOs with an excessively high medial arch, however, may increase ankle inversion injury or cause pain on the lateral foot. Cautiously designed arches and appropriate lateral balancing of the FOs are necessary to minimize the sliding of the foot laterally.
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Ankle sprain As the most common foot and ankle injury, ankle sprain accounts for more than 70% of all ankle injuries requiring absence from work.3 Ankle sprain is generally treated with shortterm rest, ankle bracing, and physical therapy. Edema and pain caused by the sprain are exacerbated during standing or walking and further delay return to work. Along with Unna’s paste bandage to control edema (the details of which are described earlier), relative immobilization allows workers to resume standing and walking early. The mainstay of physical therapy after lateral ankle sprain includes strengthening of the ankle evertors in a progressive manner and stretching of the heel cord followed by proprioceptive training.24,34 Isometric strengthening of ankle evertors can be performed at the workplace by pushing the lateral side of the foot against a stationary object such as the leg of a desk. A lateral hindfoot wedge placed under the insole reduces hindfoot inversion during the initial contact period of the gait cycle. Although anklets, high-top shoes, or boots have been recommended as a preventive measure, their effectiveness in preventing ankle sprain is controversial.15,18,37 Because footwear with excessively worn lateral heels increases ankle inversion, clinicians should examine workers’ footwear as part of the evaluation. Lingering pain or instability after ankle sprain should be evaluated for possible concurrent pathologies such as syndesmosis lesion, pericuboidal soft tissue injuries, Lisfranc’s joint injuries, talar dome injury, peroneal tendon pathology, subtalar joint instability, or peroneal nerve injury. Recurrent ankle sprain should alert the clinician to look for underlying instability of the ankle or subtalar joints, cavus deformity, weakness of the ankle evertors, or tight heel cord.1,8 Treatment of these conditions is beyond the scope of this chapter.
Case: Swelling and discomfort after lateral ankle sprain A 43-year-old man working in a movie theater fell on the stairs and sustained lateral ankle sprain. A radiologic study excluded fracture or dislocation, and the patient was treated with ice and elastic bandage in an emergency room. Because of persistent discomfort and swelling of the lateral ankle, especially during standing, the patient could not return to full-time work. A short Unna’s paste bandage was applied with a horseshoe pad around the lateral malleolus for 3 weeks, during which time the patient returned to full-time work with a weekly change of bandage. A lateral wedge was placed in his walking athletic footwear to decrease ankle inversion.
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Adaptation of workers with foot and ankle disorders to the workplace: case studies
Ankle arthrosis after fracture A major complication of ankle and pilon fractures is posttraumatic arthrosis, which correlates with the severity of the original injury and the adequacy of fracture reduction.16,36 Workers with posttraumatic arthrosis present with stiffness, pain, and difficulty with prolonged ambulation and standing. In conjunction with footwear that has rocker soles and cushion heels, FOs designed for limiting the painful range of the ankle may reduce the pain significantly. A patient with a collapsed talus after a fracture may complain of anterior ankle pain due to anterior impingement during dorsiflexion. In these instances, an anklet or an AFO with a heel lift (or, alternatively, high-heeled Western boots) may reduce the impingement and provide symptom relief. Job modification and nonsteroidal antiinflammatory medications can provide additional benefit. Surgical treatment options are reserved for cases refractory to conservative treatment. Total ankle arthroplasty has been recently advocated for posttraumatic arthrosis, although its long-term result has not been defined. This procedure should be undertaken cautiously in the working population, which is typically young and engaged in a high level of physical activity.
Heel pain Heel pain is a common complaint of workers engaging in activities that require prolonged standing. The etiology of heel pain can include fat pad atrophy, heel spur bursitis, plantar fasciitis, nerve entrapment, Haglund deformity, and calcaneal stress fracture. Plantar fat pad atrophy, which causes pain after standing for a period of time, is quite disabling in workers such as parking attendants, security guards, or operating surgeons. In most patients, the pain usually improves with a change to footwear with soft heels and insoles. Additional cushioning can be provided by a soft heel lift such as a silicone heel cup. In some patients, heel pain may persist despite the above measures because a silicone heel cup cannot prevent the fat pad from spreading as it bears weight. In these instances, low-dye taping can be used as an additional measure to contain the fat pad. Plastic heel cups (Helfet) are traditionally used to prop the heel pad. Because they are made of relatively inflexible materials, they may cause discomfort in some patients unless a precise fitting is achieved. Plantar fasciitis is typically painful in the morning, although it can be symptomatic whenever standing. Heel lifting reduces the discomfort, most likely by reducing tension in the plantar fascia and shifting body weight to the forefoot. The workers should stretch the plantar fascia and heel cord several times per day. Adequate stretching of the plantar fascia during the night frequently reduces the morning pain. A night splint has been recommended for this purpose, although it is bulky and cumbersome. Gently wrapping the foot with an elastic bandage to keep the MTP joints in dorsiflexion seems to be one of the effective alternatives.
Tibialis posterior tendon insufficiency Patients with this condition present with an initial complaint of pain in the medial hindfoot and progressive pronation deformities.
Because the initially flexible deformities frequently become rigid over time, aggressive orthotic treatment with direct control of the subtalar and midtarsal motion should be introduced in the early stages of the condition.35,39 A plain FO with a medial wedge is usually not effective in this condition because it cannot control the forefoot abduction or the motion of subtalar and midtarsal joints effectively. Once the axis of the subtalar joint is medially deviated as the pronation deformity progresses, a simple arch support is not able to provide any corrective force to the pronating foot on weight bearing.20 The University of California Biomechanical Laboratory (UCBL) supramalleolar orthosis provides direct control of calcaneal motion, restoring proper alignment of the subtalar and midtarsal joints. These orthoses can be used in regular footwear and allow the patients to continue their work activities (Fig. 8e.5). For the more advanced cases, a short rear-entry articulated AFO (Marazano AFO) has been advocated. Tight heel cord, a common sequela of this condition, contributes also to the development of permanent deformities. Orthotic management is often frustrating in patients with tight heel cord, rigid deformity, and arthritic changes of subtalar and midtarsal joints. Various surgical procedures are advocated for patients with an advanced stage of the condition. If surgery is not feasible, a rigid polypropylene AFO or Baldwin orthosis can be prescribed.5 Bulky and restrictive, these orthoses may, however, interfere with the activities at work.
Case: Insidious onset of medial hindfoot pain in a nurse’s aide A 55-year-old woman working as a nurse’s aide developed insidious onset of pain on the left medial aspect of the hindfoot 6 months ago. She also noticed that the medial arch of her left foot was collapsing and her forefoot was turning progressively outward. On physical examination, maximum tenderness was noted on the tibialis posterior tendon, and pain was precipitated by passive eversion and active inversion. The patient had flexible pronation deformity of the left foot with a slightly tight heel cord. Passive ROM of the ankle was up to neutral. She was diagnosed as having stage II tibialis posterior tendon insufficiency, and a supramalleolar orthosis was prescribed (Fig. 8e.5). The patient was able to work wearing the supramalleolar orthosis inside athletic footwear. A 1/4-inch heel lift was provided on the contralateral side to balance the limb length bilaterally.
Midfoot arthrosis and pain The functional significance of midfoot injuries is often unrecognized by practitioners.7 Workers may sustain midfoot injuries despite wearing standard safety shoes because the protective toe cap ends around the MTP joints. A device available for the protection of the dorsum of the midfoot is not favored by workers due to the restriction of motion.12 Midfoot crush injuries with nerve damage or compartment syndrome can prolong recovery and require as long as 1 to 2 years before return to work is possible. Many of these patients are not
Chapter 8e
Figure 8e.5
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Adaptations for common conditions
Supramalleolar orthosis. Figure 8e.6
capable of returning to heavy-duty industrial jobs and require vocational retraining.1 To return to work, patients often require rigid FOs in rocker-soled shoes to reduce the motion of the transverse tarsal and Lisfranc’s joints.
Painful forefoot conditions Roomy footwear is the prerequisite for successful treatment of painful forefoot conditions such as interdigital neuritis, painful calluses, and metatarsalgia of various etiologies. Frequently used to remedy such painful conditions, a metatarsal pad should be placed close to the target metatarsal head.38 According to plantar pressure recording during ambulation, the area of peak pressure of the second metatarsal head moves 6 to 8 mm distally from that of the standing position (unpublished data). Placed too proximally, therefore, a metatarsal pad may be ineffective in relieving pain. For the plantar pain of the second MTP joint, clinicians should look for underlying biomechanical abnormalities such as subluxation of the second MTP joint or short first metatarsal or first ray insufficiency. Morton’s extension to the hallux or posting under the first ray is incorporated into the FO in addition to metatarsal pad that be placed next to the second metatarsal shaft. A spring-carbon plate effectively limits the forefoot motion and can be used in conditions such as painful hallux limitus, turf toe, or stress fracture of the metatarsals.
Foot problems in workers with diabetes mellitus Complications of the foot and ankle such as Charcot neuroarthropathy or ulcerations in patients with diabetes mellitus are manageable conditions without definitive cure. The important role of the clinician is therefore prevention and early recognition of these potentially disastrous complications and long continuous follow-up. A foot that is warm and swollen after minor trauma should alert the clinician to the possibility of early developing Charcot neuroarthropathy. Workers with a small callus
Total contact cast.
under the metatarsal head may already be harboring a full-thickness ulceration beneath it that can lead eventually to limb loss. In addition to treating the medical conditions, clinicians should manage these workers with long-term plans such as major job modification or retraining for different vocations.
Neuropathic ulceration Neuropathic ulceration usually occurs on the plantar surface of the foot. Off-loading plantar pressure and reducing weight bearing are the key components of treatment. The most effective method of off-loading, total contact casting maintains the ambulatory state. With such a cast, the patient with superficial noninfected ulcers may be able to return to sedentary work (see Fig. 8e.6). Workers with insensate feet may not be able to tolerate safety shoes with steel toe caps and hard soles because of the risk of ulceration. Clinicians may advise such patients to consider vocations that do not require safety shoes.
Charcot neuroarthropathy Ankle and foot injuries such as fracture, dislocation, or even minor ankle sprains in the diabetic population should be treated with extreme alertness because of the potential risk of Charcot neuroarthropathy, the major complication that leads to amputation of the lower limb. Beginning with intense inflammation of soft tissues, joints, and bones, Charcot neuroarthropathy eventually results in fractures, dislocations, and gross deformities. It may then cause an increase in plantar weight-bearing pressure and ulceration of the insensate foot. To prevent disastrous sequela, the patient requires a period of immobilization without weight bearing by the injured lower limb that is much longer than that of nondiabetic patients. Even without a history of significant trauma, unilateral swelling of the foot should alert the clinician to possible development of Charcot neuroarthropathy. Redness, swelling, and warmth are often confused with infection or cellulitis, but these diagnoses can be eliminated if there are no constitutional symptoms or open wound and the midfoot and hindfoot are involved.
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Adaptation of workers with foot and ankle disorders to the workplace: case studies
In the acute stage of Charcot neuroarthropathy, a total contact cast is applied for optimal immobilization; this can be changed to a custom-made AFO in later stages. A Charcot restraint orthotic walker and patellar tendon bearing AFOs are ideal to relieve weight on the lower limb, but these appliances are cumbersome and may reduce patient compliance. An orthosis of hybrid design, an AFO with a leather calf piece and double uprights attached to the shoe, can be an alternative when the patient has reached a coalescing or healing phase (Figs. 8e.7 and 8). Because treatment of diabetic neuroarthropathy is a long, tiring process, the patients should be educated to expect it.
Case: Persistent swelling and increased temperature of the foot after minor injury
Figure 8e.7 Ankle foot orthosis with hybrid design (double uprights with leather calf piece attached to the shoe).
A 36-year-old man with a 20-year history of insulindependent diabetes mellitus twisted his right ankle during carpentry work and sustained a fracture at the right fifth metatarsal base. In spite of treatment with a hard-soled shoe for 3 months in another health care facility, the patient had persistent swelling and local warmth of the foot for 12 months, a history typical of Charcot neuroarthropathy. The patient was subsequently treated with a total contact cast for 11 weeks until the clinical signs of the consolidation phase appeared, followed by several months of bracing (Figs. 8e.7 and 8e.8).
Partial foot amputation Workers with partial foot amputation frequently develop equinovarus deformity of the residual foot due to muscle imbalance between the strong plantar flexors-invertors and relatively weak dorsiflexors-evertors. Recurrent skin breakdown occurs mostly on the plantar aspect of lateral-distal stump. Stretching the gastrocsoleus muscle by exercise is not feasible in most cases due to the short lever arm of the residual foot, poor condition of the plantar skin, and long-standing contracture of the heel cord as well as the ankle capsules. Surgical correction of equinovarus deformity with an Achilles tendon lengthening, Achilles tenotomy, or gastrocnemius recession should be implemented early. A short high-top shoe with a molded insole and rocker sole (stubby shoe) is a good choice to prevent recurrent ulceration of the residual foot, although workers may dislike its unaesthetic appearance. Workers with limited ankle ROM after partial foot amputation may use partial foot prostheses. Orthopedic footwear with a toe filler, steel shank, and rocker sole has been also recommended for these patients. Such a shoe, however, is heavy, affects the patient’s balance, and requires heel lift of the other shoe.
Venous and lymphatic disorders
Figure 8e.8 Ankle foot orthosis with hybrid design (double uprights with leather calf piece attached to the shoe).
Complications of venous insufficiency are dependent edema on standing, recurrent ulceration of the leg, and contracture of the heel cord. Compression therapy with Unna’s paste boot or multiplayer compression bandaging followed by the application of compressive stockings is the mainstay of treatment for venous insufficiency as long as patients do not have significant
Chapter 8e
arterial insufficiency. Patients should be educated to apply the compressive stockings and footwear in the morning, when edema is less prominent. For workers engaging in physically demanding jobs such as construction, surgical closure of the leg ulceration should be considered early to avoid the contracture of the heel cord that may further compromise foot and ankle function.31 Acquired lymphedema of the lower limb may develop in the working population due to medical or surgical conditions. Optimal control of lymphedema can be achieved by short-stretch bandaging combined with manual lymphatic drainage, comprehensive decongestive therapy, and compression stockings. Currently, the cost of these treatment measures is a major burden.
14.
15. 16. 17.
18. 19. 20.
21.
CONCLUSION The ultimate goals of care for workers with foot and ankle injuries are restoring function and allowing a timely return to work. Clinicians should be knowledgeable about the details of various adaptation measures such as footwear and FOs with realistic expectations and goal setting. By using present technologies based on sound biomechanical principles, most injured workers may be able to resume useful function and satisfactory quality of life. Clinicians should have a long-term plan in the early stage of management so that a major job modification or retraining can be implemented if necessary.
22. 23. 24. 25. 26. 27.
28. 29.
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References
Finestone A, Shlamkovitch N, Eldad A, Karp A, Milgrom C: A prospective study of the effect of the appropriateness of foot-shoe fit and training shoe type on the incidence of overuse injuries among infantry recruits. Mil Med 157(9):489-490, 1992. Gross MT, Liu HY: The role of ankle bracing for prevention of ankle sprain injuries. J Orthop Sports Phys Ther 33(10):572-577, 2003. Helfet DL, Koval K, Pappas J: Intra-articular fractures of the distal tibia. Clin Orthop 298:221-228, 1994. House CM, Waterworth C, Allsopp AJ, Dixon SJ: The influence of simulated wear upon the ability of insoles to reduce peak pressures during running when wearing military boots. Gait Posture 16(3):297-303, 2002. Karlsson J, Andreasson G: The effect of external ankle support in chronic lateral ankle joint instability. Am J Sports Med 20(3):257-261, 1992. Kelaher D, Mirka GA, Dudziak KQ: Effects of semi-rigid arch-support orthotics: an investigation with potential ergonomic implications. Appl Ergon 31(5):515-522, 2000. Kirby KA, Green DR: Evaluation and nonoperative management of pes valgus. In SJ DeValentine, ed: Foot and ankle disorders in children. New York, 1997, Churchill Livingstone, pp. 295-327. Knapik JJ, Hamlet MP, Thompson KJ, Jones BH: Influence of boot-sock systems on frequency and severity of foot blisters. Mil Med 161(10):594-598, 1996. Lechner DE: The role of functional capacity evaluation in management of foot and ankle dysfunction. Foot Ankle Clin North Am 7(2):449-476, 2002. Lippmann HI, Briere J-P: Physical basis of external supports in chronic venous insufficiency. Arch Phys Med Rehabil 52(12):555-559, 1971. Lynch SA, Renstrom PA: Treatment of acute lateral ankle ligament rupture in athlete. Sports Med 27:67-71, 1999. Manning DP, Jones C: The effect of roughness, floor polish, water, oil and ice on underfoot friction. Appl Ergon 32(2):185-196, 2001. Marr SJ, Quine S: Shoe concerns and foot problems of wearers of safety footwear. Occup Med 43(2):73-77, 1993. Milgrom C, Giladi M, Kashtan H, et al: A prospective study of the effect of a shockabsorbing orthotic device on the incidence of stress fractures in military recruits. Foot Ankle 6(2):101-104, 1985. Myerson M, Quill GE Jr: Late complications of fractures of the calcaneus. J Bone Joint Surg 75A:331-341, 1993. Neumann DA: An electromyographic study of the hip abductor muscles as subjects with a hip prosthesis walked with different methods of using a cane and carrying a load. Phys Ther 79(12):1163-1173, 1999. Oh-Park M: use of athletic footwear, therapeutic shoes, and foot orthoses in physiatric practice, state of the art reviews. Phys Med Rehabil 15(3):569-585, 2001. Owens JC: The postphlebitic syndrome: management by conservative means. In J Bergan, J Yao, eds: Venous problems. Chicago, 1978, Year Book Medical Publishers, pp. 369-382. Rendall GC, Thomson CE, Boyd RM: Sports injuries. In D Lorimer, G French, S West, eds: Neale’s common foot disorders. New York, 1997, Churchill Livingstone, pp. 65-117. Ruschhaupt WF, Fernandez BB: The swollen limb. In JS Young, JW Olin, JR Bartholomew, eds: Peripheral vascular diseases. St. Louis, 1996, Mosby-Year Book, pp. 669-679. Smith RW, Reischl SF: Treatment of ankle sprains in young athletes. Am J Sports Med 14:456-471, 1986. Steb HS, Marzano R: Conservative management of posterior tibial tendon dysfunction, subtalar joint complex, and pes planus deformity. Clin Podiatr Med Surg 3:439-451, 1999. Vander Griend R, Michelson JD, Bone LB: Fractures of the ankle and the distal part of the tibia. Instr Course Lect 46:311-321, 1997. Verhagen EA, van Mechelen W, de Vente W: The effect of preventive measures on the incidence of ankle sprains. Clin J Sport Med 10(4):291-296, 2000. Wang Y, Kim D, Oh-Park M: Plantar pressure measurement under the second metatarsal head with simple modifications of the insole in athletic footwear: a pilot study. Arch Phys Med Rehabil 82(9):poster 186, 2001. Wapner KL, Chao W: Nonoperative treatment of posterior tibial tendon dysfunction. Clin Orthop 365:39-45, 1999. Wernick J: Lower extremity function and normal biomechanics. In Valmassy RL, ed: Clinical biomechanics of the lower extremities. St. Louis,1996, Mosby-Year Book, pp. 1-56. Windle CM, Gregory SM, Dixon SJ: The shock attenuation characteristics of four different insoles when worn in a military boot during running and marching. Gait Posture 9(1):31-37, 1999.
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Functional Performance Testing Michiel Reneman and Harriët Wittink
Musculoskeletal pain represents a significant burden to all sectors of the population, with many working days lost due to back pain and muscle/joint pain. A study72 found that the prevalence of arthritis, back pain, headache, and other musculoskeletal conditions was 57% among the fully employed compared with 59% among the underemployed and with 63% among the unemployed (p < 0.01). The cost due to lost productivity time because of these common pain conditions to employers is an estimated $80 billion per year. Job requirements that exceed the worker’s physical abilities, a decline in physical abilities for instance due to progressive musculoskeletal illness (such as arthritis), or advancing age may lead to musculoskeletal impairments that may cause a loss of function severe enough to render a worker unable to meet the physical requirements of the job. The National Institute for Occupational Safety and Health report on Musculoskeletal Disorders (MSDs) and Workplace Factors60 examined the epidemiologic evidence for a relationship between physical workplace factors and low back MSDs. Strong evidence was found for the association between back disorders, work-related lifting and forceful movements, and whole body vibration. Evidence was found for the association between back disorders and heavy physical work (especially in combination with awkward postures). For neck MSDs, there is a strong evidence for an association with high levels of static contraction, prolonged static loads, or extreme working postures involving the neck/shoulder muscles. There is evidence for an association between neck MSDs and highly repetitive work and forceful exertion. Acute pain complaints are usually self-limiting, but if they become chronic the consequences are serious. Musculoskeletal impairments are the most common causes for occupational disability and loss of work. The consequences in terms of the distress of patients and their families, for employers in terms of sickness absence, and for society as a whole in terms of welfare benefits, lost productivity, and health care costs are enormous. It is the loss of function that creates disability. Disability is defined as the inability of the individual to meet expectations normal for one’s age and gender as well as one’s social and cultural environment.57 In recent years it has been recognized that the information about a worker’s medical impairment is not a valid predictor of
inability to work. Physical measurements such as tests for range of motion and muscle strength were shown to be poorly related to functional abilities and to have little value in predicting disability. Self-report measures of function and disability may be strongly influenced by psychosocial factors and are considered subjective by definition. Self-report assessments frequently do not agree with more objective measures such as observing the patient performing functional activities and the results of physical examination. Medical assessment, performed by physicians, of the ability to perform work-related activities is based on a more or less standardized interview and a physical examination. A direct comparison between expert assessments and a direct performance evaluation has not yet been performed, likely because of the poor psychometric properties of the expert assessments. From a need for a more objective measure of a person’s physical capacity for work, functional capacity evaluations (FCEs) have been developed. The introduction of FCEs cannot be tracked to a specific point in time; however, the practice is regarded as originating in the United States in the 1970s. Physicians were asked to assess the work ability of injured patients but were unable to do so based on a history and physical examination only. They in turn asked physical and occupational therapists to measure the patient’s ability to work. The therapists compiled existing and selfdeveloped tests into a battery of tests and named them FCEs. The original definition of FCE was “a systematic process of measuring and developing an individual’s capacity to dependably sustain performance in response to broadly defined work demands.”51 Over the past three decades FCEs have become big business as judged by the more than 1 million websites available on the Internet. Describing FCEs and their components requires a clarification of the terminology commonly used in this area. Since the introduction of FCEs, there has been a general inconsistency in the terms used to describe the evaluation itself, its procedures, and results. Terms such as functional capacity evaluation, functional capacity assessment, physical capacity evaluation, physical performance analysis, work capacity evaluation, work tolerance screening, and functional ability evaluation were and still are used interchangeably, in some
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Table 9.1
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Definition of terms
Terms
Definition
Evaluation
The process of obtaining and interpreting data necessary for understanding the individual, system, or situation. This includes planning for and documenting the evaluation process, results, and recommendations, including the need for intervention and/or potential change in the intervention plan.36 Specific tools, instruments, or interactions used during the evaluation process with comparison of the affected body part to the norm. An assessment is a component part of the evaluation process.36 Obtaining and reviewing data relevant to a potential patient to determine the need for further evaluation and intervention. A standardized procedure of measurement. The limits of the anatomic, physiologic, and psychologic systems of the person (depends on age, gender, genes, etc.). Physical capacities refer to a level of functioning, often referred to as “impairments” in the terminology of the World Health Organization’s International Classification of Functioning (ICF). Impairments may include static and dynamic muscular strength, flexibility of the joints and surrounding tissues, coordination, gait, balance, posture, and muscular and cardiovascular endurance. Capacity as modified by individual behavioral attitudes, in addition to external factors such as injury, pain, environmental and social stressors—the quality of being able to perform; a quality that permits or facilitates achievement or accomplishment. The act or process of functioning, sometimes measured by a performance scale or a performance test. Broad categories of human activity that are typically part of daily life, also called functional measures. They are activities of daily living, work and productive activities, and play or leisure activities and include sitting, standing, walking, kneeling, squatting, lifting, pushing, pulling, carrying, and manual dexterity.
Assessment Screening Testing Capacity
Ability Performance Performance areas
instances mistakenly.1 The words assessment, evaluation, testing, screening, capacity, performance, ability, functional, and physical are used interchangeably, causing significant confusion. For clinicians and researchers to understand each other, a common language with clear definitions of terms is imperative (Table 9.1). We chose to use the term functional performance evaluation (FPE) in this chapter, realizing that the acronym FCE is more widely known in the field. The reasoning for this is that in its essence the FPE is an evaluation of a person’s ability to perform activities. An elaboration of the differences between “performance” and “capacity” is presented below. Placed into the context of work, the FPE becomes a test to measure the individual’s ability to meet or exceed the physical demands of the work, with specific reference to a job and the tasks involved (in turn specified into duration, load, and repetitions).
PURPOSES The measurement of the ability of a person to perform workrelated activities can be used to serve several purposes (listed below). They may not be used for all these purposes with every client but should depend on the client need, referral request, or clinical or administrative requirements. Selection of type and components of an FPE may be guided by the purpose for which it is used. A clear understanding from the referral source regarding the purpose of the FPE is essential in choosing an FPE. The purposes of FPEs are as follows38: 1. To determine the need for intervention and treatment, and to design and plan treatment. The perspective here is mainly clinical to determine whether an intervention is necessary and to design a program to improve on those activities that have shown to be deficient.
2. To determine an individual’s ability to perform the demands required in relation to the work context. The perspective here is both administrative and clinical. From the administrative viewpoint, the purpose is to ensure a safe and speedy return to work, thereby reducing costs. From a clinical viewpoint, the purpose is to ensure that the match or mismatch between the individual’s level of function and the work demands has been identified to lower the risk of further injury and to implement appropriate work modifications if necessary. In evaluations where return to a former job is an issue, a job analysis should be performed to determine the tasks required for the job. A good job analysis requires a work site visit during which, for instance, the frequency, duration, intensity, and the distance a person must lift, bend, and reach is identified and recorded, in addition to other factors that might affect the worker, such as sitting time, desk height, uneven floors, and the timing of breaks. If a job analysis cannot be done, a detailed quantifiable job description reflecting the critical job requirements, such as employers are required to have, is essential. The results from the FPE can then be compared with the job demands. Needless to say, the FPE tests should focus on the specific tasks the worker might have difficulty with. In a case of preemployment testing for a potential job, a more comprehensive and generic assessment is needed to avoid a potential mismatch between the worker and the job demands. 3. To determine sincerity of effort and consistency of effort during assessment. Assessment results may be considered when a determination regarding the level of disability is made related to financial compensation. This has an administrative purpose, especially in litigious situations where assessments of function are used for medicolegal purposes. From a clinical viewpoint, determining sincerity or consistency of effort and underlying causes of submaximal performance may assist in guiding the
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focus of treatment. For example, an individual producing submaximal effort may be anxious about reinjury or return to work and may require intervention with a behavioral rather than a physical emphasis. 4. To document outcome, achievement of goals, and or effectiveness of the program. The viewpoint is primarily an administrative one, with the emphasis on demonstration of achievement of program goals. 5. To determine the level of disability. This may be used for the settlement of a workers’ compensation claim or to determine whether the disability is permanent or temporary. If disability assessment is at issue, the FPE should correspond to the information requested by the person determining the level of disability.44 6. To develop and improve treatment resources for service provision and research.
What to measure Most authors agree that the test components of the FPE include the medical history, in which the individual factors associated with MSDs60 such as age, gender, physical activities/fitness, strength, anthropometry (body mass index), and cigarette smoking, should be noted; physical examination to quantify physical impairment and to determine any contraindications for testing; work history; pain assessment; and a variety of work-related performance tests and self-reported functional limitations. There exists disagreement as to how these components should be filled.44 In the following section the work-related performance tests and the self-reported functional limitations are discussed.
Work-related performance tests The contextual relationship of FPEs with work can easily be understood from its original purpose. FPEs are predominantly inspired by the taxonomy described in the U.S. Department of Labor’s Dictionary of Occupational Titles (DOT). This taxonomy, although never formally tested for its validity, has gained support in many countries around the world. The DOT classification is similar to selected domains of the International Classification of Functioning (ICF) and classifications such as a back-specific classification called the functional assessment taxonomy.33 Among others, the DOT provides information about the work characteristics of most jobs in the United States in terms of the physical demands these jobs place on the workers. The demand classification is based on certain principles assumed or demonstrated to be key elements in the nature of work. These key elements are defined in the DOT as the physical demands of a specific job and are called job factors. There are 20 job factors, with some of them broken into subfactors: standing, sitting, walking, lifting, carrying, pushing, pulling, climbing, balancing, stooping, kneeling, crouching, crawling, reaching, handling, fingering, feeling, talking, hearing, and seeing. These job factors then express both the requirements of the job and the capacities a worker must have to meet or exceed those demands. It has been stated that the content validity of FPEs based on the DOT is sufficient and that most of the commercially available FPEs cover many to all of these work characteristics.40
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Purposes
Additionally, all jobs in the U.S. economy have been classified into the following five levels of exertion: sedentary, light, medium, heavy, and very heavy (Table 9.2). The physical demands strength rating reflects the estimated overall strength requirement of the job, expressed in terms of the letter corresponding to the particular strength rating. It represents the strength and endurance requirements, which are considered to be important for average successful work performance (see http://www.oalj.dol.gov/ public/dot/refrnc/dotappc.htm, accessed August 31, 2003). In their systematic review of FCEs, King et al44 found little evidence in the literature of the inclusion of physical fitness assessments in FPEs. This is in contrast to the finding that the development of most FPEs is inspired by the DOT, in which the energy requirements of jobs are defined. The level of aerobic fitness directly affects the amount and intensity of physical activity an individual is able to perform. Most physical activities are described in terms of their energy or metabolic cost.2,5 Physical activities are coded in metabolic equivalent (MET) intensity levels. One MET is considered a resting metabolic rate obtained during quiet sitting and equals an oxygen uptake of 3.5 ml/kg/min. The oxygen cost for physical activities ranges from 0.9 MET for sleeping to 18 MET (running at 10.9 mph).2 Aerobic fitness matters a great deal when performing physically demanding work. Workers with physically demanding jobs include firefighters, the police and military, waste collectors, and home care workers. For instance, firefighters need to be highly aerobically fit to perform their job duties. Oxygen uptake during fire suppression is about 25-35 ml/kg/min (7-10 METs), which reflects how very physically demanding firefighting is. Based on this observation 38-42 ml/kg/min has been most frequently cited as the desirable VO2max level.71 This is average fitness for healthy males under 50 years of age, but an average fit female of any age would not have this aerobic capacity. If the aerobic demand of work cannot be met, premature fatigue can put a person at risk for injury. For instance, it has been shown that inactive firefighters have a 90% greater risk of myocardial infarction than those who are aerobically fit,58 and Linden48 showed an inverse relationship between maximal oxygen uptake and absenteeism in custom officers. Studies investigating workers ought to describe the energy demand level of their job as set forth by the U.S. Department of Labor (Table 9.2). Because of the proven importance of aerobic fitness in the determination of work capacity,5 aerobic testing should be part of an FPE.
Self-reported functioning Historically, an assessment of functional capacity was made by asking patients about their activity levels. A large variety of questionnaires has been developed to measure patients’ perceptions of their physical activity level and disability. Studies in patients with chronic pain, however, have identified discrepancies between self-report of physical activity and actual level of physical activity. In a number of these studies, the reported physical activity level was clearly lower than the observed level. Objective measurement of functioning as by FPE therefore seems warranted. When comparing the results of FPEs with the results of questionnaires, it has been shown that the outcomes are substantially different and correlate moderately at best.27,47,66
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Table 9.2
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Physical demands strength rating
Physical demand level
Occasional* 0–33% of the work day
Frequent* 34–66% of the work day
Constant* 67–100% of the work day
Sedentary Light
10 lbs. 20 lbs.
Medium Heavy Very heavy
21-50 lbs. 50-100 lbs. Over 100 lbs.
Negligible 10 lbs. and/or walk/stand/ push/pull of arm/leg controls 10-25 lbs. 25-50 lbs. Over 50 lbs.
Negligible Negligible and/or push/pull of arm/leg controls while seated 10 lbs. 10-20 lbs. Over 20 lbs.
Typical energy required 1.5–2.1 METs 2.2–3.5 METs 3.6–6.3 METs 6.4–7.5 METs Over 7.5 METs
*Amount of force exerted to lift, carry, push, pull, or otherwise move objects, including the human body (1 lb = 0.45 kg). METs, metabolic equivalents.
In one of these studies, 64 patients suffering from nonspecific chronic low back pain (CLBP) rated themselves on three different well-known low back–specific questionnaires as moderately to severely disabled. The questionnaires were the Roland Morris Disability Questionnaire,67 the Oswestry Back Pain Disability Scale,18 and the Quebec Back Pain Disability Scale.45 These same patients, however, were able to perform activities at a physical intensity level consistent with moderate to heavy work (classification DOT). Correlations between the questionnaires and the FPE results were poor to moderate.66 Another striking example of the difference between self-reports and actual activity levels was described by Verbunt et al.78 The activity levels of patients suffering from CLBP and matched healthy control subjects were measured continuously for 2 weeks using a triaxial accelerometer. The results demonstrated that the mean activity levels of the patients, who had rated their disability as substantial, did not differ significantly from the control subjects. It is clear that instruments based on self-report or based on performance measure different dimensions of the same construct. One of the reasons for this discrepancy might be that psychosocial factors, such as depression and disability status, appear to have a larger effect on self-report than on performance testing.83 Unfortunately, affective states appear to influence functional performance as well. Poorer achievement on physical performance testing of patients with CLBP has been linked to fear of injury during movement, depression, pain expectations, pain increase during testing, and the presence of a solicitous spouse.49,79,82,83 FPEs have been justly criticized for their lack of measurement of psychosocial variables that might influence testing and that may interfere with successful return to work. In conclusion, a performance measure should be used to measure “a person’s ability to perform an activity.” Questionnaires can be used to measure “a person’s self-reported ability to perform an activity” and to measure the psychosocial factors that might influence both self-report and performance. It is advocated to use both performance-based and self-report measures to obtain a more comprehensive picture of a person’s disability.
CHARACTERISTICS OF AN EFFECTIVE FUNCTIONAL PERFORMANCE EVALUATION When developing evaluations, both legal constraints and professional practice standards should be applied.
Legal constraints Legal constraints challenge the validity of FPEs. Various pieces of legislation, such as the Americans With Disabilities Act (1990), the Age Discrimination Employment Act (1967), and the Federal Uniform Guidelines of Employee Selection Procedure (1978), require that function tests not discriminate against age and sex and that appropriate accommodation in testing is created for those who have impairments. Caution should be used when comparing an individual’s performance with normative data, because the Americans With Disabilities Act prohibits this method to make decisions regarding return to work, and denying a job to an individual with a disability based on data that compares his or her functioning with that of the general population is illegal. The effects of age are confounded with work capacity. Aerobic fitness declines with age.3 Both muscle contractile and mitochondrial protein decrease with aging in sedentary humans resulting in decreases in muscle strength and endurance. With regard to lifting, Matheson et al50 studied 531 healthy subjects and found that age made a significant contribution to lift capacity, which continued to be significant even when resting heart rate and body mass were considered, suggesting that agelinked decrements in aerobic capacity and musculoskeletal strength may have a potentiating effect on decrements in lift capacity. Age can therefore be a justifiable reason for early retirement in persons with physically demanding jobs. The most important legal constraint on functional testing, aside from discrimination, is that it be evidence based (Daubert v. Merrell Dow Pharmaceuticals, 1993). This case law requires that peer-reviewed publications in scientific journals be given precedence in determining acceptability of test-based evidence. It also sets standards for legally acceptable scientific evidence. Scientific peer review is essential for acceptability. Thus, when big money is resting on an FCE, its credibility can be destroyed by the opposing attorney when the test cannot meet those standards.55
Professional practice standards The American Psychological Association and the American Physical Therapy Association published professional practice standards for measurement. In these models, there are five issues that must be addressed in the selection and use of any functional
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Characteristics of an effective functional performance evaluation
test in a patient population. These issues, presented in hierarchical order, are as follows: ● Safety: Given the known characteristics of the patient, the procedure should not be expected to lead to injury. ● Reliability: The test score should be dependable across evaluators, patients, and the date or time of test administration. ● Validity: The interpretation of the test score should be able to predict or reflect the patient’s performance in a target work setting. ● Practicality: The cost of the test procedure should be reasonable and customary. Cost is measured in terms of the direct expense of the test procedure plus the amount of time required of the patient, plus the delay in providing the information derived from the procedure to the referral source. ● Utility: The usefulness of the procedure is the degree to which it meets the needs of the patient, referrer, and payer.
Safety The safety of testing depends on a number of factors that include the physical health of the patient, equipment safety, a “tried and tested” protocol, and the experience of the evaluator. No testing performed on the patient should lead to reinjury or a new injury. Qualified professionals should administer the FPE using a standardized protocol, both to ensure the patient’s safety and to increase the reliability of the FPE. The medical history and the physical examination to quantify physical impairment together ought to determine any medical contraindications for testing. Medication use should be noted because a variety of medications (such as alpha/beta-blockers, Ca2+ channel blockers) affects a normal exercise response and thus interferes with physiologic measurement of the workload (i.e., by heart frequency). Safety criteria used during FPEs usually consist of the following. The evaluator must know of any medical constraints before testing. The client should be instructed that he or she may terminate testing at any point if deemed appropriate. A heart rate monitor should be worn to prevent the heart rate rising over a predetermined maximum. Most studies use a maximum of 85% of the client’s predicted average maximum (220 – age). Finally, the evaluator should terminate testing when the client is at risk during the evaluation. This involves a professional judgment based on medical information, the client’s history, the physical examination, and the performance during the functional evaluation. No peer-reviewed data are available on how often the evaluator would terminate testing for this reason. The authors know of no reports in which new or reinjuries during or resulting from FPEs are described. Among others, evaluators may observe quality of movement, spinal alignment, and body mechanics as a part of their safety determinations. With regards to the latter, the use of a squatting technique is usually advocated over a stooping technique. A review of the biomechanical literature, however, has revealed no significant differences in spinal compression between the two techniques.77 Maximal symptom-limited aerobic testing is safe, although various facilities require supervision of a physician during testing. The American Heart Association analyzed eight studies related to sudden death during exercise testing.21 The reported
rates were 0 to 5 per 100,000 exercise tests. A survey of the Veterans Affairs Health Care System exercise laboratories found an event rate of 1.2 per 10,000 tests of major cardiac events (myocardial infarction, ventricular tachycardia) and no deaths during 75,828 exercise tests performed within the last year.56 In summary, it can be concluded that the risk of medical complications is related to the underlying disease, and it appears that the rate of death for patients, during exercise testing, is 2 to 5 per 100,000 clinical exercise tests. For details on cardiovascular testing see http://ajrccm.atsjournals.org/cgi/content/full/167/2/211.
Reliability Reliability involves the extent to which an evaluation is consistent and free of error. This consistency may be over time (test-retest reliability); between different raters, observers, or evaluators (interrater reliability); between more than one identical session rated by the same evaluator (intrarater reliability); or between equivalent parts of the same test (internal consistency). Although all types of reliability are important, establishment of test-retest and interrater reliability are deemed most important in FPEs, because it ensures that any change found in the assessment is the result of change in the individual and not the result of measurement inconsistencies over time or between examiners. A number of factors may influence the reproducibility of results. An important factor to consider is that of a potential learning effect and therefore the need for preliminary/ familiarization testing. Patients should practice the test at least once to prevent undue anxiety and to increase mechanical efficiency, especially when equipment is used with which the patient is not familiar. An additional factor that may influence the reproducibility of measurements is the time of testing. Preferably, repeated testing should be undertaken at the same time of day, as significant diurnal variation in results has been reported.25 Furthermore, the testing protocol, procedure, and instructions to the patient must be rigidly controlled, because these have been shown to significantly affect performance.31,73 Finally, disease severity (pain severity) may also affect the variability of some measurements during exercise42,82 and may affect the interpretation of results in some patients with more severe disease. An area that may benefit from further development is that of internal consistency. By examining the correlation between test items, it may be possible to streamline evaluation batteries to include only those items that assess necessary activities, rather than duplicating items that assess the same or similar activities.
Reliability of evaluating work-related activities The most recent review of the scientific evidence of the reliability of FPEs was published in 1999.39 It was clearly demonstrated that the evidence for reliability of a wide range of FPEs ranged from nonexistent to being investigated and reported in sufficient detail. There did not appear to be a single FPE that had been thoroughly and comprehensively investigated for all relevant aspects of reliability. Since then, however, developers of FPEs appear to have greater appreciation of the need to investigate and report the reliability. To the authors’ knowledge, since and including 1999, a number of papers have been published or have been accepted for publication in peer-reviewed journals (PubMed, key word: functional capacity evaluation reliability,
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1999-2003). Reports containing new data of different aspects of reliability were identified about the following FPEs: ● Baltimore Therapeutic Equipment Primus FPE: Test-retest reliability of handgrip and lifting of 30 healthy subjects was good, both for strength and for endurance protocols.47 The reliability of three other tests was also studied, with similar results, but it may be questioned whether tests of isolated wrist flexion and extension and elbow flexion should be considered as functional. ● Ergos Work Simulator: Test-retest reliability of seven upper extremity items were tested on 12 healthy subjects, indicating good reliability.10 Similar to the Baltimore Therapeutic Equipment Primus FPE, it may be questioned whether some of the tests studied should be considered as “functional” activities. ● Functional Range of Motion Assembly Test: Test-retest reliability of three items was tested on 51 healthy adults. Results indicate moderate to good reliability.52 ● Isernhagen Work Systems FPE: Five separate reports of interrater and intrarater as well as test-retest reliability of the material handling items indicate good overall reliability in healthy subjects and patients.24,30,41,61,63 Test-retest reliability of two tests measuring maximum holding times of static postures indicated good reliability in healthy young adults.64 Test-retest reliability of almost all items of the Isernhagen Work Systems FPE, tested on 30 patients with CLBP, indicated a wide range of reliability, varying from unacceptable to good.12 ● Physical Work Performance Evaluation: Test-retest reliability of nine main items of this FPE was tested on 24 subjects with stable physical injuries (mainly back disorders). The results indicate moderate to substantial reliability of the items tested.76 Although many FPEs have still not demonstrated reliability in peer-reviewed journals, the developments are positive. A number of studies are performed with reasonable to good scientific scrutiny, using both injured and uninjured samples, by different researchers independent from each other. The studies demonstrate that performance-based measurements, such as FPEs, can be used to reliably evaluate a person’s functional capacity. They also demonstrate that although reliable at the group level, the performances of injured individuals (with CLBP) may vary substantially between occasions.12 It appears that this variance can in large part be attributed to the variance in patient performances rather than measurement inconsistencies over time or between raters.30 Further research is needed, however, to confirm this suggestion. Most of the recently published studies have used the IWS FPE. This may be positive for the body of knowledge of the Isernhagen Work Systems FPE but not to the field of FPEs as a whole, because it is currently not known if, or to what extent, the knowledge gained from one FPE can be generalized to other FPEs.
Reliability of evaluation aerobic capacity The intraindividual day-to-day variation in measuring aerobic fitness (VO2max) is between 4% and 6% in persons with no known cardiovascular disease,69 but the variation is larger in persons with known chronic obstructive pulmonary disease (6-10%).13 There is no information on the reliability of maximal symptom limited cardiopulmonary testing in persons with musculoskeletal pain.
Validity Validity is usually considered to be the extent to which an instrument measures what it is intended to measure. The validity of a test refers to the appropriateness, meaningfulness, and usefulness of the specific inferences made from the test results. Validity depends on the purpose of the assessment and therefore the test objectives. It is not a universal characteristic of an assessment. No single measure is sufficient from which to determine an assessment’s validity. These aspects imply that multiple studies of the various forms of validity are required and that validity must be evaluated within the context of the test’s intended purpose and a specific population. Several forms of validity are relevant to FPEs: face, content, criterion-related (concurrent and predictive), and construct validity (Table 9.3).
Sincerity of effort A confusing and inappropriate use of the term validity occurs in some work-related assessments. The terms validity profile, valid, conditionally valid, conditionally invalid, and invalid effort are used by some FPEs. These terms do not refer to the validity of the instrument or test battery results but rather to the level of effort exerted by the client performing the assessment. They are used to describe the level or sincerity of effort exerted by a client and are not related to the measurement concept of validity. The reader should be aware of this use of the term and note that there is no scientific justification for the use of the term validity profile as that term relates to functional testing.40 This subject of effort levels, sincerity of effort, and pain behaviors is one of great importance for any form of performance testing, including FPEs. The term capacity connotes the maximum ability of the evaluee, beyond the level of tolerance that is being measured.50 Capacity is the evaluee’s potential, determined by physiologic factors.80 The use of the term capacity is somewhat misleading, because capacity is rarely measured in a performance task, unless the evaluee is highly motivated and trained to perform that particular task. Examples of maximum task performance are found when experienced athletes compete. When the evaluee is an injured worker, the functional capacity is usually inferred from evaluation of task performance. Even when the evaluation task is designed to measure the evaluee’s maximum performance level, this is achieved rarely. The maximum level of performance that can be measured is the portion of capacity the evaluee is willing to muster. Thus, the performance of the individual depends both on his or her abilities to perform and his or her motivation to perform. Two items are of paramount importance in this: (1) how can capacity and performance be differentiated when evaluating an individual (are the results reflective of maximal or submaximal physical abilities) and (2) what factors determine the motivation of a patient to perform? Neither question can be answered with scientific certainty at this time. Methods that are being used to differentiate between a maximal and a submaximal performance (also referred to as sincerity of effort) are Waddell’s nonorganic signs, descriptions of pain behavior and symptom magnification, coefficients of variation, correlations between musculoskeletal evaluation and function, grip measurements, and the relations between heart rate and pain intensity. Despite the widespread use of these methods, up to 1998 little had been published to address their reliability and
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Table 9.3
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Definitions of validity40
Face validity Content validity
Criterion validity
Concurrent validity Predictive validity Construct validity
When a work-related assessment appears to measure what it intends to measure and it is considered a plausible method to do so. The degree to which test items represent the performance domain the test is intended to measure. Content validity is usually determined by a panel of experts who examine the relationship between test objectives and test items or by knowledge of the normal practices used. The systematic demonstration of the extent to which test performance is related to some other valued measure of performance or external criterion. It is composed of concurrent and predictive validity and is considered to be the most practical approach to validity testing and the most objective. Examines the correlation between two or more measures given to the same subjects at approximately the same time so that both reflect the same incident of behavior. Compares a subject’s performance at the initial time of testing with performance obtained at a future date with another highly valued measure or “gold standard.” For work-related FPEs a client’s success when returning to work is a highly valued criterion. The extent to which a test can be shown to measure a hypothetical construct. For example, a work-related assessment may be considered to have some support for construct validity if it is able to differentiate between clients who are able to lift safely and those who do not, where the construct being measured is safe lifting ability (also called discriminant validity). Known Groups Method is the most general type of evidence and involves the ability of the test results to discriminate between groups which are known to be different (e.g., different diagnostic groups; different age groups; different occupational groups) in a theoretically appropriate manner. Correlation with other tests involves the examination of the degree of convergence and/or divergence with other tests that are presumed to measure the same or different constructs or traits.
FPEs, functional performance evaluations.
validity specific to the FPE setting.46 Two studies published since then have tested strategies to differentiate between maximal and submaximal performance in a lifting test. Both studies report promising results with regards to the sensitivity and the specificity of their methods to differentiate between maximal or submaximal effort levels.19,43 Both studies used healthy subjects, which may not be representative for patients with musculoskeletal injuries. Additionally, both studies dichotomized between maximal and submaximal, suggesting a greater difference than presented in daily practice. There are large differences with the group labeled as “submaximal,” because all subjects performing between 10% and 90% of their maximum would fall into that category. The challenge for future developments in this area is to develop and test methods to differentiate between all levels of effort (from light to maximum), not only on healthy subjects but on relevant patient groups as well. Until then, clinicians should remain careful in classifying their patients’ performance levels. The second question deals with factors determining the motivation of a patient to perform during an FPE. Watson80 developed a model in which task performance during a performance evaluation of patients with chronic pain is explained. Other than physiologic factors, the following nonphysiologic factors are postulated in the model: task familiarity and learning, self-efficacy, pain self-efficacy, fear avoidance beliefs, current pain level, and outcome expectancy. Based on these factors, a patient may be motivated to perform to maximum capacity or to terminate an activity before reaching maximum. It is important to not only assess the extent to which a client is willing to perform to his or her physical maximum, but also the reason(s) why he or she performs as such. This assessment may require knowledge beyond the professional capabilities of functional capacity evaluators, often physical or occupational therapists. Consistent with all major standards and guidelines of chronic
pain and work injury management, it is advocated to use the services of a clinical psychologist or a behavioral therapist to assess these aspects in conjunction with the evaluation of the functional capacity. Their assessments, however, should meet the same criteria of reliability and validity as any other assessment and should not rely on self-reports or clinical expertise only.
Validity of evaluating work-related activities The last review of the scientific evidence of the validity of FPEs was published in 1999.40 It was demonstrated that the evidence for validity of a wide range of FPEs ranged from nonexistent to being investigated and reported in sufficient detail. Very few FPEs were able to demonstrate adequate validity in more than one area or with more than one study. Since then, as was the case with the reliability, developers of FPEs appear to have greater appreciation of the need to investigate and report the validity. To our knowledge, since and including 1999, several articles have been published or have been accepted for publication in peer reviewed journals (Pubmed, key word: functional capacity evaluation validity, 1999-2003). Reports containing new data about different aspects of the validity were identified for the following FPEs: ● Baltimore Therapeutic Equipment Work Simulator: Real and simulated lifting tasks were compared. The results suggest the Baltimore Therapeutic Equipment Work Simulator overestimates real lifting endurance performance in healthy men. Lower physiologic stresses during the simulated task suggest a significant difference between the real and simulated loads.75 ● DOT Residual Functional Capacity battery: Stooping, climbing, balancing, crouching, feeling shapes, handling left and right, lifting, and carrying appear to have construct validity in chronic pain patients. In a sample of 155 chronic pain patients, the DOT Residual Functional Capacity battery
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could not predict employment levels. However, if a patient passes certain items of the FPE and has a pain level less than 5.4 (scale, 0-10), that patient has a 75% chance of being employed at 30 months after treatment at the pain facility. It was concluded that some DOT Residual Functional Capacity battery job factors demonstrate a predictive validity in the “real work world.”20 A study on functional capacity and psychologic measures concluded that psychologic variables were related to measures of functional capacity measured at the admission stage of a rehabilitation program and that psychologic measures at admission were not good predictors of later functional capacity measures. Additionally, functional capacity measures were identified as important predictors of followup employment outcome, but return to work could not be predicted without taking pain into account.16 Functional Assessment Screening Test: Some evidence was described to confirm criterion validity because performance of patients with CLBP was inversely related to self-reported depression, disability, and different dimensions of pain experience.68 The strength of the relationships, however, was not reported. Gibson Approach to FPE: An expert review performed by five occupational therapists supported the content validity of aspects of this FPE.26 Isernhagen Work Systems FCE: In a large cohort of patients (n = 650; diagnoses not specified) studied retrospectively, gender and time off work were found to be the strongest predictors of whether or not the patients returned to work, with performance on a lifting task adding little but significantly to the prediction. Of those who did return to work, the performances on two lifting tasks were related to the level of work they returned to.52 A study that examined the ability of this FPE to predict a timely return to work in a workers’ compensation environment by a worker suffering from low back pain found that better performance on FPE was weakly associated with faster recovery; however, the amount of variation explained was small.28,29 One task in the FPE was as predictive as the entire protocol. Another study that examined the ability of this FPE to predict sustained recovery in a workers’ compensation environment by a worker suffering from low back pain found that better FPE performance as indicated by a lower number of failed tasks was associated with higher risk of recurrence. The validity of the FPE’s purported ability to identify claimants who are “safe” to return to work is suspect.28,29 Two separate studies confirm the concurrent and the construct validity of this FPE, as it relates poorly to moderately to different forms of self-reported disability.28,29,66 A moderate relation between FPE performance and pain intensity was found,28,29,65 and the relation between FPE performance and kinesophobia was found to be nonexistent.65 Self-reports of function or prediction of function was poorly related to actual function on tests measuring maximum holding times of maintaining postures.62 Yet another study found preliminary evidence in support of the ecologic validity of this FPE; test results were not relevantly influenced by differences in test conditions.64
Although many FPEs have still not demonstrated aspects of their validity in peer-reviewed journals, the developments are
positive as well. A number of studies concerning different aspects of validity are published. As was the case with reliability, most of the recently published studies concern the Isernhagen Work Systems FPE. Again, this may be positive for the body of knowledge of the Isernhagen Work Systems FPE but not to the field of FPEs as a whole, because it is currently not known if, or to what extent, the knowledge gained from one FPE can be generalized to other FPEs. One study in which upper lifting performance was tested according to two FPE protocols revealed significant differences in results.37 This indicates that differences in operational definitions of the activity tested, for example lifting height and repetitions, really do matter. Even though the amount of evidence is limited, it is suggested that generalization between FPEs should not be made unless great care is used. In conclusion, the following can be derived from previous40 and the above-mentioned publications. The construct validity of FPEs based on the DOT classification is confirmed with regards to the choice of activities that make up the evaluation. It has been demonstrated clearly that the results of functional capacity measurements differ substantially from results of selfreports. Psychologic factors are known to influence test results, but the extent to which they do, however, remains unclear and warrants future research. The predictive power of FPEs with regards to their ability to predict safe and lasting return to work has not been clearly demonstrated and the results of different studies appear to conflict. It may be questioned whether FPEs will ever be found valid for the prediction of a safe and lasting return to work. The construct of “workability” is widely regarded as a multidimensional construct. Whether a patient successfully returns to work or not depends on more than functional capacity by itself. It is paramount that an instrument measuring a single dimension cannot be expected to assess a multidimensional construct. It is therefore by definition incorrect to suggest or to claim that the results of an FPE should be able to predict a person’s work ability or, even more complex, a successful return to work. At best, one may expect from an FPE, in conjunction with endurance testing, to measure an individual’s functional ability to perform work-related activities. This should be seen as one of the prerequisites for a successful return to work. Seen in this light, the role of the physical domain may prove to be a modest one.
Validity of testing aerobic capacity The gold standard for determining absolute VO2max in an individual is by metabolic measurement system analysis of O2 and CO2 gas in expired air at regular intervals and attainment of a maximum heart rate of at least 90% of age predicted maximum (220 – age), a plateauing of VO2 and respiratory exchange ratio (RER) >1.0.4,6,74 In normal subjects, the highest VO2max is obtained with treadmill testing due to the quantity of the muscle mass involved, followed by bicycle testing. VO2max achieved by bicycle testing is reported to be 5-15% lower than with treadmill testing in normal subjects.34,35 Astrand and Rodahl5 report a 5-7% difference in maximal oxygen uptake between treadmill and bicycle testing in well-trained subjects. Predicted VO2max ml/kg/min estimated from arm exercise testing is 60-70% of leg exercise in normal subjects. Normal females reach 65-75% of male VO2max.6 The lower oxygen uptake capacity in women may have to do with their
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lower hemoglobin concentration and higher body fat content. In both genders, oxygen uptake peaks at 18-20 years of age, followed by a gradual decline with age. At the age of 65, the mean value is about 70% of what it is for a 25-year-old individual. Not much is known about the validity of exercise testing in patients with chronic pain, because historically exercise testing was mostly used in athletes, healthy subjects, or subjects with cardiac and pulmonary problems. One study81 compared treadmill, bicycle, and upper extremity ergometry (UBE) exercise testing in a small (n = 30) sample of patients with CLBP. Indirect calorimetry was used to determine oxygen uptake, and a threelead electrocardiogram was used to determine heart rates at each minute of testing. Subjects were encouraged to “do as much as you can.” The researchers used the modified Bruce treadmill test, the Astrand-Rhyming bicycle test, and a UBE test. The testing response for patients with CLBP was remarkably similar to that of normal subjects. Significantly higher heart rates, peak VO2, and predicted VO2max ml/kg/min were achieved by the modified Bruce treadmill test than with the bicycle or UBE tests, despite pain, consistent with normal subjects. Also, peak and predicted VO2max showed gender differences consistent with published results for normal subjects, supporting criterion validity of aerobic testing in patients with CLBP by treadmill, bicycle, or UBE. Further criterion validity for treadmill testing in patients with CLBP was supported by the finding that prediction equations for estimated maximum oxygen consumption (VO2max) in patients with CLBP equal those in healthy sedentary men and active women.54 The treadmill is the most commonly used mode of testing and is the apparatus of choice in the laboratory because exercise intensity is easily determined and regulated. Most clinics have access to a treadmill, making this a practical test. Determining aerobic uptake by indirect calorimetric measurement is time consuming and costly, however, and therefore not always of practical use in the clinic. A variety of (submaximal) tests has been developed estimating aerobic capacity when direct measurement is not possible. These tests usually involve running/ walking for a given time or distance, such as the 12-minute walk/run test, the shuttle test, and various step tests.70 Longer distances and shorter test times are associated with higher levels of aerobic fitness. Other tests estimate VO2max by submaximal testing and extrapolation to maximal heart rate by treadmill walking or bicycling against a predetermined load with measurement of heart rates.3,7,14,23 These tests were mostly developed for testing aerobic fitness in healthy people and were validated by comparing actual measured VO2max with predicted VO2 or to the test performance. The validity of a number of these tests was established for patients with cardiac or pulmonary problems,17,32 but little has been done to validate these tests in patients with chronic pain. In one study,84 30 patients with CLBP underwent bicycle ergometer testing using the Astrand-Rhyming method. Predicted VO2max was calculated, both by using the nomogram and by extrapolating VO2 values obtained by indirect calorimetry. The predicted VO2max values derived from the nomogram were age corrected as suggested by Astrand and Rodahl.5 There were no significant differences between the nomogram and calorimetric predicted VO2max values (p > 0.59) for the sample. Individual predicted values by the nomogram method, however, were shown to underestimate predicted VO2max by as much as
41% and overestimate predicted VO2max by as much as 38%. On average, an error of 20% should be taken into account. Similarly, estimating aerobic fitness in METs from a Bruce treadmill test, by comparing the level reached by the patient with established MET norms for that level, results in significant underestimation and overestimation of individual fitness levels ranging from 25% to 33%.84 It is important to understand that the most accurate, and therefore valid, way to measure VO2max in a single individual is through direct measurement of maximal oxygen uptake. When determining fitness for duty it is extremely important to “get it right” as a person’s health and safety might be at stake, not to mention his or her job security. Aerobic fitness has construct validity in physically demanding work. A vast body of knowledge has been accumulated on the energy cost of physical work. In general, a person can carry on all day without fatigue if the workload is less than 40% of the individual’s maximal aerobic fitness. Ergo, the less fit a worker is, the less load this person can tolerate (or tolerate the same load for a shorter amount of time). Pohjonen59 investigated the effect of aerobic capacity of home care workers on their ability to work and found that poor average maximal oxygen consumption (l.min-1; odds ratio, 3.1) indicated a high risk for reduction in work ability, supporting the content validity of aerobic fitness. A combination of back strength and aerobic fitness explained 31- 41% of the total variance of lifting ability in healthy females.53 No such data are yet available on persons with MSDs. The predictive validity of aerobic fitness is mixed. As stated before, inactive firefighters have a greater risk of myocardial infarction than those who are aerobically fit.58 Low cardiovascular fitness level was a risk factor for disabling back pain in a prospective longitudinal study among aerospace manufacturing workers.8 In their landmark article, Cady et al15 reported that the frequency of injuries among firefighters was 10 times higher for the least-fit group than for the most-fit group (n = 266 in the least-fit group, n = 259 in the most-fit group). The cost per claim for the 19 injured men from the least-fit group was 13% more than for the 36 injured men from the middle-fitness group. Unfortunately, fitness levels were a composite of strength, flexibility, and aerobic fitness, and it is unclear which component of the fitness score was most important to the outcome. Similar composite measures of fitness were identified as risk factors for training injuries in the military.9 Boyce et al,11 however, reported that only 7% of absenteeism could be explained by age, sex, and physical fitness among 514 police officers 35 years or older.
Practicality Full-length FPEs usually require 4 to 6 hours of both the patient’s and the evaluator’s time. Some FPEs divide this time over consecutive days to evaluate the effects of the evaluation of the first day, whereas other FPEs take up to a total of 22 hours to perform, divided over multiple days. It has been suggested that FPEs should shorten the time needed to collect data to meet consumer demand.44 This suggestion seems reasonable; the length or comprehensiveness of the FPE should be tailored to the purpose of the evaluation, and the results of recent studies suggest that is quite possible to do so. A shortened version has been suggested as a screen to filter out those individuals who self-limit their performances due to pain behaviors.68 The need
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for a 2-day evaluation for patients with CLBP could not be confirmed.61 Most recently, a strategy has been described to develop a job-specific FPE derived from a full-length protocol, reducing evaluation time from 6 to 1.5 hours.22 Additionally, research is warranted to streamline evaluation batteries to include only those items that assess necessary activities rather than duplicating items that assess the same or similar activities. It has not been shown that longer FPEs are superior to short FPEs.
3.
Utility
9.
An FPE needs to have utility. There should be a justifiable reason to perform an FPE; otherwise, such a test adds to the health care burden unnecessarily. To be of value the test must help the individual, physician, health care personnel, payer, and employer to determine the individual’s physical ability. It should be able to identify an injured worker’s ability to return to his or her usual work or be able to determine a person’s fitness for duty in case of a preemployment assessment. It can also be used as a preprogram measure in functional restoration or work-hardening programs to identify rehabilitation needs and targets and to serve as an outcome measure postprogram. Finally, an FPE should be able to identify persons with symptom magnification or malingering.
CONCLUSION
4. 5. 6. 7. 8.
10.
11. 12.
13. 14.
15. 16.
17. 18.
The results of performance-based evaluations of work-related activities are distinctly different from other types of evaluations. They are, however, still not always incorporated into standardized assessment batteries. The reasoning for this is unknown. It is speculated that disadvantages believed to accompany FPEs, one of which being the duration of the evaluation (several hours), weigh heavily in the decision-making process. FPEs may thus be impractical and expensive. Additionally, the psychometric properties of FPEs have been critically reviewed in the past. The results of these reviews have repeatedly shown that FPEs lack foundation regarding reliability and validity. Recent scientific developments of some FPEs have been presented here. The results should force the general opinion into a more optimistic direction. The strength of assessing the functional domain by means of a reliable and valid FPE may be to confirm or refute a patient’s belief that his or her capacities are insufficient to perform work. From a cognitive-behavioral perspective, such a belief to be proven false through an FPE is beneficial, because it confronts the patient with maladaptive behaviors and belief systems. The effect of such a confrontation may allow for introduction of different, more effective, and efficient interventions directed toward a safe and lasting return to work.
19.
20.
21.
22. 23.
24. 25. 26. 27.
28.
29.
30. 31.
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References
Reneman MF, Dijkstra SJ, Jorritsma W, Muskee C, Schiphorst Preuper HR, Goeken LN: Assessment and treatment of chronic work-related pain disorders in an outpatient university rehabilitation setting in The Netherlands. Work 16:23-30, 2001. Reneman MF, Jaegers SM, Westmaas M, Goeken LN: The reliability of determining effort level of lifting and carrying in a functional capacity evaluation. Work 18:23-27, 2002. Reneman MF, Joling CI, Soer EL, Goeken LN: Functional capacity evaluation: ecological validity of three static endurance tests. Work 16:227-234, 2001. Reneman MF, Jorritsma W, Dijkstra PU: The relationship between kinesiophobia and performance in a functional capacity evaluation. J Occup Rehabil 13(4):277-285, 2003. Reneman MF, Jorritsma W, Schellekens JM, Goeken LN: Concurrent validity of questionnaire and performance-based disability measurements in patients with chronic nonspecific low back pain. J Occup Rehabil 12:119-129, 2002. Roland M, Morris R: A study of the natural history of back pain. Part I. Development of a reliable and sensitive measure of disability in low-back pain. Spine 8:141-144, 1983. Ruan CM, Haig AJ, Geisser ME, Yamakawa K, Buchholz RL: Functional capacity evaluations in persons with spinal disorders: predicting poor outcomes on the Functional Assessment Screening Test (FAST). J Occup Rehabil 11:119-132, 2001. Shephard RJ: Tests of maximum oxygen intake: a critical review. Sports Med 1:99-124, 1984. Siconolfi SF, Garber CE, Lasater TM, Carleton RA: A simple, valid step test for estimating maximal oxygen uptake in epidemiologic studies. Am J Epidemiol 121:382-390, 1985. Sothmann MS, Saupe K, Jasenof D, Blaney J: Heart rate response of firefighters to actual emergencies: implications for cardiorespiratory fitness. J Occup Med 34:797-800, 1992. Stewart W, Ricci J, Chee E, Lipton R: Work-related cost of pain in the US: results from the American Productivity Audit. IASP/10th World Congress on Pain, Abstract 697-P331, 2002. Swinburn CR, Wakefield JM, Jones PW: Performance, ventilation, and oxygen consumption in three different types of exercise test in patients with chronic obstructive lung disease. Thorax 40:581-586, 1985. Taylor HL, Buskirk E, Henschel A: Maximal oxygen intake as an objective measure of cardiorespiratory performance. J Appl Physiol 8:73-80, 1955. Ting W, Wessel J, Brintnell S, Maikala R, Bhambhani Y: Validity of the Baltimore therapeutic equipment work simulator in the measurement of lifting endurance in healthy men. Am J Occup Ther 55:184-190, 2001. Tuckwell NL, Straker L, Barrett TE: Test-retest reliability on nine tasks of the Physical Work Performance Evaluation. Work 19:243-253, 2002. van Dieen JH, Hoozemans MJ, Toussaint HM: Stoop or squat: a review of biomechanical studies on lifting technique. Clin Biomech 14:696, 1999. Verbunt JA, Westerterp KR, van der Heijden GJ, Seelen HA, Vlaeyen JW, Knottnerus JA: Physical activity in daily life in patients with chronic low back pain. Arch Phys Med Rehabil 82:726-730, 2001. Vlaeyen JW, Linton SJ: Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art. Pain 85:317-332, 2000. Watson PJ: Non-physiological determinants of physical performance in musculoskeletal pain. In M Max, ed: Pain 1999—an updated review, ed 1. Refresher course syllabus. Seattle, 1999, IASP Press, pp. 153-158. Wittink H, Michel TH, Kulich R, et al: Aerobic fitness testing in patients with chronic low back pain: which test is best? Spine 25:1704-1710, 2000. Wittink H, Rogers W, Gascon C, Sukiennik A, Cynn D, Carr DB: Relative contribution of mental health and exercise-related pain increment to treadmill test intolerance in patients with chronic low back pain. Spine 26:2368-2374, 2001. Wittink H, Rogers W, Sukiennik A, Carr DB: Physical functioning: self-report and performance measures are related but distinct. Spine 28(20):2407-2413, 2003. Wittink HM: Physical fitness, function and physical therapy in patients with pain: clinical measures of aerobic fitness and performance in patients with chronic low back pain In M Max, ed: Pain 1999—an updated review, ed 1. Refresher course syllabus. Seattle, 1999, IASP Press, pp. 137-145.
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The Physician’s Role in Disability Evaluation Robert H. Haralson III
Throughout history most social systems have been forced to deal with the problems of a population containing individuals who have been injured, who are suffering from chronic disease, or who simply through aging have a reduced ability to perform the daily activities required for survival both at work and at home. In nonindustrialized societies, the physical disabilities associated with aging are often perceived as being accompanied by increased wisdom and experience. Older members of these societies thus become the teachers and decision makers for the communities. Those individuals with minor restrictions in ability are given tasks around the home in the preparation of tools or food and the care of children. Because of a lack of medical and health resources, the severely disabled inevitably succumb to infection or malnutrition and, occasionally in certain societies, some form of ritual suicide. In modern industrialized nations, on the other hand, those individuals who are disabled have access to a wide variety of health care facilities and social resources that attempt to reintegrate them into the community. To avoid abuse of these benefits, mechanisms have been developed to assess degrees of disability and assign responsibility for its cause. Rapid growth in the cost of these benefits has led to an increasing emphasis on the effects of chronic illness and injury on life-style and work capacity. Extensive legislation has established rules for the provision of benefits to those unfortunate enough to have reduced capacity as a result of chronic illness or injury. Such legislation includes workers’ compensation,30 Social Security,35 and the Americans with Disabilities Act. Furthermore, multiple private and industrial programs and insurance policies have been established to assist individuals who are ill, injured, or otherwise disabled. In almost every determination of disability or ability, legislation or private contract requires the input of at least one and often several licensed health care practitioners. The basic assumption is that the individual who is most competent and best trained to determine the ability of other members of society to perform specific duties is the medical physician. This decision has been based not on any well thought out or scientifically investigated competence but instead has fallen on the physician by default. Unfortunately, the skills necessary to perform this social function are not as a rule taught in medical school and until recently have
not even been the subject of significant research. To some extent, therefore, physicians asked to perform this task must do so based on personal opinion, great variability in experience, and usually poorly thought out legislation or social contracts.
ETHICS ASSOCIATED WITH DISABILITY EVALUATION Physicians required to determine a degree of impairment and the ability or inability of an individual to perform specific tasks must deal with a number of ethical dilemmas not commonly considered in clinical practice. In comparison with disability evaluation, basic clinical practice is relatively simple. Most physicians perceive their ethical duties as to care for and to relieve patient symptoms or illnesses by whatever means they can, without any consideration of the social position of their patients or the pressures exerted from outside authorities. The welfare of the patient is inherent in the Hippocratic Oath. The contract for services is between the doctor and the patient. When a physician is required to change roles and issue opinions on legal matters, one of two things happens. If their opinions will impact their own patients’ ability to obtain compensation or to work in particular occupations, physicians naturally are biased in favor of each patient’s position in the matter. Failure to take a patient’s position could seriously jeopardize the patient-doctor relationship and adversely impact the ability to manage the patient’s health care needs. On the other hand, an inability to justify a particular position that the patient may hold strongly can seriously jeopardize the physician’s credibility within a workers’ compensation or other health care delivery system. Studies by Brand and Lehmann8 demonstrate that many treating orthopedists are willing to exaggerate a situation to benefit the patient’s position in third-party actions. If physicians are functioning as independent medical examiners, their ethics are subject to pressure from the referring source. Inevitably an independent medical examiner receives a referral because of disagreement between the insurance carrier or agency and the patient or treating physician. Regardless of the honesty
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of the independent medical examiner, insurance carriers tend to refer insured persons to physicians with track records who are likely to support their positions. Further difficulty arises in that patients tend to distrust independent medical examiners and may attempt to justify their perceived positions through embellishment and other forms of exaggerated behavior. Although the criteria of Waddell and associates37 can be used to identify certain of these factors, the assessing physician may lose sympathy for such an individual regardless of an underlying disability that may be camouflaged by this behavior. Physicians must be careful to remember that some patients who exaggerate can also have real pathology. In our system, patients are paid to be sick, and the sicker they are, the more they are paid. Patients who learn to act sick cannot get well.18 In that situation, it is a natural human response to advocate for one’s position. Hadler17,19 seriously questioned the ethics of any physician who performs disability evaluations, arguing that the notion of impairment rating is fatally flawed and should be discarded completely. He believes that diminished work capacity as a result of musculoskeletal disorders, the most common cause of disputed disability, is overwhelmed by psychologic and sociopolitical confounders and cannot be determined in the medical setting. The marked variation in medical opinion as to the nature and extent of disability given similar clinical findings tends to support this view. Further support comes from the work of Waddell et al,36 Bigos et al,5,6 and Deyo and Diehl,14 which demonstrates that the greatest predictors of disability from low back pain are psychosocial rather than pathophysiologic. Other studies demonstrated that by far most factors predicting return to work are psychosocial rather than physical. Treating physicians, most of whom have not had specific training in impairment evaluations, are least prepared to render objective ones. Data show that surgeons who perform large numbers of cardiovascular operations and total joint replacements achieve better outcomes; data suggest also that physicians who perform large numbers of independent medical evaluations are more accurate and consistent. Training and practice improve outcomes in impairment evaluations just as they do in surgical procedures. Just as patient treatment relies on scientific rather than anecdotal data, so-called evidenced-based medicine applied to impairment or return-to-work determinations results in opinions that are fairer to the employee, employer, and insurer.
MEDICAL OPINIONS REQUIRED DURING DISABILITY EVALUATION The physician faced with a demand for a disability evaluation must reach a number of conclusions and provide opinions on the topics explained on the next few pages. Not all disability schemes require that the physician address each issue. Furthermore, specific requirements or definitions inherent in the administrative procedure of a specific disability system might not be included in this outline.
Date of permanent and stationary status Either a treating or an assessing physician must determine the point of maximum medical improvement or permanent and stationary
status, the point at which administrative rules concerning disability begin to take effect. It is virtually impossible for an accurate permanent disability evaluation to be made before declaration of the point of maximum medical benefit. Within some jurisdictions with a time limit, however, it is occasionally necessary to render an opinion before maximum medical improvement is reached. In those situations, commonly involving an arthritic joint that will ultimately lead to total replacement, the physician should state the disability at that time but indicate that improvement or worsening is possible. In some cases the physician may include an estimate of future impairment. Although there is no universal rule, it is reasonable to assume that the time of maximum medical benefit or permanent and stationary status is the point at which the patient has shown no significant change for a number of weeks and it is unlikely that future medical treatment will improve the medical status or level of disability. The American Medical Association (AMA) guides2 define maximum medical improvement as the time from which the patient is unlikely to experience significant improvement within 1 year.
Residual subjective complaints Once it is determined that the patient has reached permanent and stationary status, most agencies request a statement regarding the ongoing symptoms. The discussion of subjective complaints includes a list of the specific body parts or functions that are affected and the manner in which they compromise the patient’s functional ability in both work and recreation. This can often be obtained by simply asking the patient to list all symptoms and discuss how they affect all activities. It is useful to note how patients perceive not only their disabilities but also what they consider to be their abilities for specific functions.
Residual objective findings Inevitably, the physician is asked to list the abnormalities found on physical examination as well as any and all abnormal laboratory and imaging findings. In certain disability evaluation systems such as Social Security, a simple listing of the objective findings is all that is necessary.10 Other systems, such as the AMA guides,2 require not only lists of objective findings but also severity classifications of loss of range of motion (ROM), sensation, strength, or coordination. Another decision often required in this setting is a statement as to whether the subjective complaints are consistent with and confirmed by the objective findings. Signs of nonorganic clinical patterns, such as those developed by Waddell et al37 for low back pain, may be requested by name or by insinuation.
Diagnosis Although many disability evaluation systems require a diagnosis, it shows little correlation with the amount of impairment and, for that matter, disability. Many workers function quite well with significant impairments, including amputations of upper and lower extremities, whereas others are totally disabled by less
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significant impairments. Disability is more closely tied to psychosocial issues than to diagnosis. With regard to the spine, physicians should remember that in the absence of obvious radiculopathy, examination of a patient with acute neck or back pain rarely identifies the pain generator or yields a specific diagnosis. A diagnosis of back sprain implies tearing of ligaments, a condition that probably rarely exists. Examiners are encouraged to use more generic terms such as back pain or lumbago. Making a specific diagnosis in an extremity is usually much easier than in the spine, but even here “pain only” syndromes can be a problem. The examiner should follow the International Classification of Diseases coding rules and diagnose only to the point at which the specificity is certain.24
Return-to-work determinations Determining when a patient should return to work is now one of the most controversial requirements of treating and evaluating physicians. It has been commonplace for physicians to take workers off work for extended periods of time for conditions that should not prevent some kind of work activity. Mounting evidence shows that the longer a patient is off work for whatever reason, the less likely that he or she will ever return. Several studies demonstrated significant increases in morbidity and mortality in people who are no longer working.16 Very few conditions would in and of themselves prevent a worker from being at work. One is coma; another is lower extremity injures in which the use of ambulatory aids is precluded by concomitant upper extremity injuries. It has been stated that if an employee can commute and be at work, there is no reason for absence.34 Data indicate that in the long run it is less expensive for the employer to have an employee at work doing nothing than for the employee to stay at home where deconditioning continues; if the employee can actually do meaningful work or even attend rehabilitation, the rewards are even greater. With proper accommodations, early return to work should be the norm, but many companies still do not have programs to allow it. This is especially true of the most common condition to cause loss of work, acute back pain.15 Return-to-work decisions are based on three concepts: capacity, risk, and tolerance. Capacity is what a patient can do at a particular time. Very few people function at full capacity, which can be increased by conditioning and training. It is therefore current ability that is being assessed, a difficult task because it requires the cooperation of the patient. The standard method is functional capacity evaluation, implying that one can assess the job requirements, perform a functional capacity evaluation, and match the two. It has not been shown, however, that functional capacity evaluations are valid for assessing abilities with regard to low back pain, for example. Functional capacity evaluations are more useful in limited situations: jobs involving only simple motions by the extremities where testing simulates the requirements and infrequent near maximal lifting where isometric strength approximates. Although many rating physicians still use functional capacity evaluations in any situation because they are helpful to corroborate clinical impressions, results must be interpreted in the context of their lack of proven scientific validity. Risk of reinjury or worsening of a condition greatly concerns physicians and employers. Physicians are reluctant to send
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employees back to work early for fear that the requirements might cause the condition to recur or delay the recovery; employers fear that it will lead to another claim. Data show that the chances of significant recurrent injury after an episode of acute low back pain are in the range of 1.7 times the incidence in workers with no previous back pain. The incidence of back injury claims in the normal population is 3 per 100 workers, so that of recurrent claims in workers with previous back injuries is 5.1 per 100, an increase of 2 per 100. The cost of these additional claims is miniscule compared with that of leaving all 100 workers off work for extended periods of time.36 Data on return to work after myocardial infarction are similar.22 The main determinant of an employee’s decision to return to work is tolerance of mild discomfort and inconvenience. Are the rewards greater for returning to work than for being absent? Some employees fear returning to work; many know of an acquaintance who is chronically disabled by back pain. Many employees need convincing that by benefiting their health and well-being, return to work is in their best interest, as proven by numerous studies.23 Although the pursuit of pain relief decreases function and increases pain, the pursuit of increased function decreases pain. One difficulty in this setting is to differentiate the capabilities of a normal healthy person of similar age, sex, education, and body build. These can often be inferred by National Institute for Occupational Safety and Health or other standards.31 It then becomes necessary to determine how a particular individual being evaluated differs from normal and how this variance affects the ability to do specific work. Nowhere in medical or even in specialty training does this determination approach a science, but two references give some reasonable guidelines for return to work: the Official Disability Guidelines13 is categorized by diagnosis and The Medical Disability Advisor32 is categorized by diagnosis and procedure. A study by Buchbinder et al9 showed that merely educating patients about how returning to work was in their best interest significantly reduced their time off.
Work and activity ability In addition to determining if and when an employee may return to work, physicians are often asked to prescribe activity limitations. The Occupational Safety and Health Administration guidelines are very restrictive and do not reflect the science. Bigos,4 the lead author of the AHCPR (Agency for Health Care Policy and Research) clinical practice guidelines for low back problems in adults, indicated that government personnel changed the physicians’ recommendations regarding weight restrictions. Mounting evidence indicates that the restrictions physicians habitually place on workers are overstated.11 With respect to acute low back pain, Malmivaara et al27 wrote the “Activity Paradigm,” the principle of which is to return to activity as normal as possible as soon as possible. Although some other conditions obviously require temporary limitations of activities, workers should be reintroduced to the work force as early as possible and to normal activity if at all possible. This is beneficial for their physical rehabilitation as well as for their psyches. There is little evidence, for instance, that patients need restrictions after recovering from episodes of acute back pain. Although the most common restriction is lifting, little evidence has shown
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that lifting in and of itself causes back pain. Most back injuries, in fact, are associated with light loads. Studies do not show that lifting follows the dose-response curve in which the more one lifts, the more it hurts. When proper lifting techniques are used and the load lifted does not correlate with injury, twisting during lifting is more likely to aggravate back pain.
Causation Although causation is more a legal doctrine than a medical one, examining physicians are often asked to render their opinions. In medical school we are taught to take a history from the patient and to rely on it when forming opinions. When a patient indicates that a pain started at a certain time and in association with a certain activity, it is not the examiner’s duty to investigate whether he or she is telling the truth. Physicians are asked to judge if the injury described by the patient could have reasonably caused the condition. In many extremity injuries, objective findings on physical examination and imaging studies make the etiology obvious, but if the claimant complains of back pain or one of the other painonly conditions like carpal tunnel syndrome or lateral epicondylitis, deciding causation is more difficult. Back pain is ubiquitous: About 80% of humans experience it at some time during their lives. Degenerative disk disease is present in essentially every human after age 50. Thirty percent of magnetic resonance images in patients with no back pain are read as positive for ruptured disk.7 Identical twin studies have shown no difference in the amount of degenerative disk disease in hard-working and sedentary twins, suggesting that it is mostly hereditary.3 It is therefore difficult to attribute much of the back pain we see to industrial injuries, but in today’s legal climate if a worker states his or her back pain started on the job, it is assumed to be compensable unless proved otherwise. Although we do have scientific information on injury response, it is difficult to attribute back pain to a particular injury when the onset of pain was more than 24 to 48 hours afterward. In addition, there is mounting scientific evidence that carpal tunnel syndrome is rarely entirely secondary to work tasks.12
Apportionment Physicians are often asked to render an opinion as to how much impairment is due to a particular injury and how much was preexisting, because the legal and insurance industries assume they are trained to do so. Unless an impairment evaluation has occurred before the injury in question, however, this is a very difficult task. In fact, it is mostly guesswork on the part of the examining physician, one that may not be appropriate. Sometimes the physician should decline to offer an opinion and state that it is medically impossible to apportion. This is true especially in a claimant with a work-related back injury, preexisting degenerative disk disease, and previous episodes of back pain not associated with work or in one who has had multiple work-related back injuries. In the absence of any objective changes in anatomic structures that are caused by the injury in question, the only difference is the amount of pain the claimant is experiencing, which cannot be quantified or qualified. In the absence of a formal
impairment rating before the injury in question, accurate apportionment is very difficult, if not impossible. If the physician can reconstruct an impairment scenario that existed before the present condition, however, apportionment may be possible. If a worker previously had a lumbar radiculopathy treated with surgery that relieved pain, for instance, then he or she would be rated as a lumbar category III and at a 10% impairment. If radiculopathy recurred in the same spinal area, whether or not the condition required surgery, the worker would now be rated by the ROM method. Subtracting the 10% category III rating from the ROM rating would allow the rater to apportion the remainder to the new injury.2 Though the two methods of rating are not totally compatible, this is one way of estimating apportionment.
Ongoing and future medical care requirements At times physicians are asked to estimate future medical costs, a very difficult task because costs include not only physician fees but also hospital charges, which can be variable and are usually significantly higher. In addition, predictions about future medical care are inexact because of the variation in the type of treatments suggested by different physicians. The care of back pain is a prime example. The incidence of back surgery in different parts of the country varies significantly, and the inference is that some physicians are more likely than others to opt for surgical treatment. Like return to work after a back injury, future medical care of back pain, moreover, is steeped with psychosocial issues. Predicting the rate at which damaged joints will lead to total replacement is inexact also, because psychosocial issues may influence the treatment chosen. Despite the difficulties, physicians must make estimates in some cases and should reflect the inaccuracy of such endeavors in their reports.
PRINCIPLES OF IMPAIRMENT DETERMINATION The workers’ compensation system is administered by each state, each of which requires use of its own method of evaluating permanent impairment. The standard text for determining permanent impairment is the AMA Guides to the Evaluation of Permanent Impairment,2 which is required or recommended by some 40 states. Some states name a specified edition, whereas others require the use of the “most current” version: Texas, for instance, recently switched from the third to the fourth edition, and in 2004 California began using the fifth edition. Some states have a hybrid system; for instance, West Virginia uses the fifth edition but will not allow use of the ROM system to evaluate spinal disorders. A few states have developed their own unique systems, and at least one state allows the physician to use any method he or she wishes. The AMA guides are just that, not an authority engraved in stone. Some conditions such as shoulder disorders are not covered well. A patient with a rotator cuff tear that was successfully repaired with a full ROM probably has some residual impairment but would be classified as not impaired according to the
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ROM method. It is therefore permissible to depart from the AMA guides if the reasons are set out in the report. Another example is cervical category IV, where a patient with an arthrodesis of one level for radiculopathy is assigned at least 25% impairment when in fact this standard treatment for disk pathology in the cervical spine seldom results in much disability. The question of who should perform the evaluation is controversial. Some believe that it should be the treating physician who should know the most about the examinee. Data suggest, however, that an independent physician who has never treated the patient is more objective.20 Physicians are taught in medical school to advocate for their patients, a precondition for good doctor-patient relationships. This requirement places the treating physician in a difficult position, especially if the outcome of treatment has been less than satisfactory. Although activity is very complicated and often not intuitive, few physicians have had any formal training in impairment evaluation. Such an evaluation does, however, require the skill of a physician who is performing a complete and accurate history and physical examination and interpreting objective and subjective findings. Physicians must learn to objectify subjective findings.21 Patients in the workers’ compensation setting tend to exaggerate their symptoms, a natural human response to a system in which the payment level corresponds to that of an illness. The examining physician must be adept at sorting out contradictory findings so that the impairment evaluation is fair to all parties. Over-interpretation of subjective findings may lead to an inordinately high rating, but care must be taken not to underrate only because a few nonphysiologic signs are present. Some claimants who have learned to exaggerate as part of illness behavior may have real pathology. It is incumbent on all evaluating physicians to become adept in impairment evaluations; several training alternatives are available. The American Academy of Disability Evaluating Physicians1 holds several courses on impairment evaluations per year throughout the country, as does the American Board of Independent Medical Examiners; both organizations offer a certifying examination. Several specialty societies have begun to include impairment evaluation on their curricula, and a number of states require continuing medical education in evaluations to be able to perform them. These states either provide the continuing medical education themselves or arrange with one of several organizations to teach the subject.
USING THE AMA GUIDES FOR RATING IMPAIRMENT Because the use of the AMA guides is required or suggested in most states and may serve as a template in jurisdictions that do not require its use, and because the musculoskeletal system is the most commonly used section, it is appropriate in this text to have a brief discussion of some of its principles. Physicians must understand the difference between impairment and disability. Impairment is defined as loss of function of a body part. Disability includes impairment, motivation, education, socioeconomic status, and several other parameters that are difficult to measure. The AMA guides rate impairment, not disability. Although some jurisdictions use a mathematical formula that includes the impairment
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rating to determine disability and monetary award, the AMA guides suggest that this is inappropriate. The AMA guides attempt to provide a method of rating impairments that allows multiple physicians to arrive at similar ratings. Response to treatment and several of the Waddell signs are examples. Physicians performing impairment ratings using the AMA guides must thoroughly understand the entire text, especially Chapters 1 and 2. It is insufficient merely to turn to a picture of an anatomic part and read an impairment rating from the adjacent chart or table. There may be several appropriate ways to rate a patient, and the rater must decide which one is most accurate for the particular case.
Differences between the fourth and fifth editions There are several differences between the fourth and fifth editions of the AMA guides. The biggest difference in the spine section is that in the fourth edition, the impairment was calculated for the injury, not for the result of treatment. This meant that findings that occurred any time during the patient’s course were enough to place a patient in a category and the results of treatment made no difference. In the fifth edition, treatment is considered, and to be significant, findings must be present at the time of the examination. In addition, in the fourth edition there was no way in the diagnosis-related estimate (DRE) method to consider arthrodesis, but in the fifth edition it is included in the definition of loss of structural integrity. Finally, the ratings in the DRE method include a 3% range: The physician is allowed to increase the rating up to 3% if there are ongoing objective signs of continuing problems. The rating should not be increased only because of a pain complaint. The differences between the fourth and fifth editions with respect to the upper and lower extremities are minimal. A very helpful addition to the lower extremity section is the matrix on page 526 that assists in the decision as to when to combine the different methods of evaluating the lower extremity.
Pain Chapter 1 of the AMA guides states that “physicians recognize the local and distant pain that normally accompanies many disorders. Impairment ratings in the AMA guides already have accounted for commonly associated pain, including that which may be experienced in areas distant to the specific site of pathology.”2 Because a 3% range is already included in the spine DRE ratings, Robinson et al33 argued that it is never appropriate to “double dip” and add ratings for pain to ratings in the spine chapter. On the other hand, if an examinee has pain defined as “ratable” according to the AMA guides, then one can use the pain chapter (Chapter 18) to award up to an additional 3% impairment.
Spine impairments In both editions, the DRE is the method required to rate all patients who have sustained an injury to the spine, except for a
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few conditions in the fifth edition for which the ROM method is used. In most cases, disk pathology is assumed to be secondary to an injury. For cases of recurrent radiculopathy in the same spinal area, fractures at multiple levels in the area, or multilevel loss of structural integrity (multilevel spinal arthrodesis), the ROM method is used. This practice has led to inordinately high ratings for patients who have undergone one-level diskectomy and fusion for disk pathology in the cervical spine. Recurrent injuries not involving radiculopathy should not be rated by the ROM method. If it is followed, the AMA guides require the use of an inclinometer rather than a goniometer for measuring the motion. The rating physician should be aware that the ROM method requires the inclusion of all three of its components: ROM (Table 15-7) and any neurologic component from Tables 15-17 or 15-18 if appropriate. These ratings are combined using the Combined Values Tables at the back of the book. Controversy exists about the accuracy of spinal ROM measurements and the relationship of loss of ROM to impairment and/or disability, but at this time the ROM method is still used in certain default conditions.25,26,28-29 Spinal injuries that involve injuries to the spinal cord or cauda equina are rated using Table 15-6, which combines seven tables from the neurologic chapter. Values from each table are combined with each other and then that value is combined with a rating from DRE categories II through V. The rating from the DRE method awards impairment for the local condition (fracture or radiculopathy), whereas Table 15-6 does so for the cord damage.
be combined with other methods of assessing impairment in the upper extremity. Normally only one method is used, but if more than one accurate method is available to assess impairment, it may be appropriate to use them all and award the highest value. Occasionally, methods are appropriately combined when the impairment is not adequately estimated by one. An example would be a distal elbow fracture that injured the ulnar nerve. The elbow injury would appropriately be rated by ROM measurements, but these would not include residual impairment from the ulnar nerve injury, which would require the use of the peripheral nerve ratings. Total upper extremity rating would then be calculated by combining the two. Values for fingers should be converted to the hand, the hand to the upper extremity, and the upper extremity to the body as a whole using Tables 16-1 to 16-3. Carpal tunnel syndrome rating uses the neurologic method. Sensory and motor deficits are determined and graded using Tables 16-10 and 16-11, although the two-point discrimination method or the Semms-Weinstein monofilaments may help the evaluator grade the sensory component. Grading motor loss usually does not require formal strength testing but may be helpful in verifying the validity of the examination. Evaluating physicians are strongly encouraged to use the charts on pages 436 and 437. These charts guide the user through the complicated upper extremity process and give specific instructions about adding versus combining values.
Lower extremity impairments Upper extremity impairments The function of most of the upper extremity is to move the hand in a position to perform a task. As a result, ROM measurements are of paramount importance; a reasonable way to assess impairment; and the mainstay of rating the shoulder, elbow, and wrist. The hand itself is rated by combining values for amputation, sensory deficits (based on the two-point discrimination method), and loss of motion. Because there is usually no motor loss in hand injuries below the wrist, strength measurements are seldom necessary. Nerve injuries are rated by estimating the magnitude of sensory and motor deficits using the appropriate tables and then multiplying that figure by the maximum loss for each named nerve, branch of the cervical plexus, or nerve root. Vascular deficits are rated using a specific table. A number of “other” conditions such as synovial hypertrophy, joint malalignment, and joint instability are rated by estimating the magnitude of the particular problem using Tables 16-9 through 16-24 and multiplying by the maximum value for each particular joint from Table 16-18. Recurrent dislocation of the shoulder has its own table in which rating is based on frequency. If there is no other method to assess impairment of the upper extremity accurately, one may use loss of strength. Tables in the AMA guides estimate normal grip strength by occupation and age as well as by normal pinch strength. By subtracting the patient’s strength from the “normal” strength and dividing by the “normal” strength, one calculates the loss of strength index. Table 16-34 then estimates impairment. This method should not
Unlike the upper extremity, the function of the lower extremity is to provide a stable platform for standing or ambulation. Though important, ROM is therefore less so than in the upper extremity, so several other assessment methods are available. Table 17-2 is a guide to when these methods should or should not be combined. Strength loss, muscle atrophy, and gait derangement are usually used when there is no other good way to rate the patient. Limb length discrepancy, on the other hand, may be combined with several other methods. In some situations, loss of ROM is the best way to assess impairment even in the lower extremity. Impairments for loss of motion in each direction are added in each joint. For instance, impairment in the hip would be calculated by adding impairments for all six motions. The impairment for complete ankylosis of a joint is calculated by assessing impairment for ankylosis in optimum position and then adding impairments for malposition, if present. In the hip, for instance, this would mean a possible addition of five more estimates (there are no tables for ankylosis in extension). The sum total of all impairments in a badly deformed hip may be more than 100%, in which case the whole person impairment is the 40% assigned to the lower extremity because the extremity impairment cannot be more than 100% of a part. A rating method unique to the lower extremity is that for narrowing of a joint secondary to arthritis: To calculate impairment, narrowing on x-ray examination is compared with standard measurements for normal joint space. The AMA guides contains a large section of diagnosis-based estimates, including total joints, malaligned fractures, and ligamentous instabilities. Total joints are rated based on a point
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system that reflects the function of each. Total ankles have not been addressed. Meniscal pathology is rated depending on the treatment. Partial excision is rated less than total. Because it was not common at the time the fifth edition was published, meniscal transplant is not mentioned but is now receiving more attention. Most patients have some narrowing of the joint, and in these situations combining values for the narrowing and for partial meniscectomy seems appropriate. Peripheral nerve injuries are rated similarly to those in the upper extremity, with Tables 16-10 and 16-11 being used to grade the deficits. Skin loss in the lower extremity can cause significant impairment in certain locations such as the ischial tuberosity and the bottom of the foot, and there are methods for rating for those conditions. As in the upper extremity, vascular lesions are rated by a separate table.
ADMINISTRATIVE CONSIDERATIONS The final decision about whether an individual is eligible for benefits under a disability system is in all cases either legal or administrative. Physicians performing disability evaluation must recognize that they are simply providing information and opinions upon which administrative or legal decisions can be made; it is not unusual for medical perception of the amount of impairment to translate financially into either considerably more or less disability. Each piece of legislation concerning disability and every administrative policy or contract includes very complex methods of translating a physician’s medical report into specific numbers used to distribute benefits. The Social Security system and many disability policies, for example, are all-or-none decisions: An individual is declared either disabled or capable of returning to work.
Rating physical impairment of the musculoskeletal system is an entrenched part of the workers’ compensation system in the United States as well as in many other third-party conflicts. Assessing impairment and disability is an inexact science at best. Because many findings require interpretation and the evaluator must differentiate between those that are objective, subjective, or subjective but able to be “objectified,” assessment requires the knowledge, expertise, and skill of a physician. Because impairment evaluation is rarely taught in medical school or residency, it is unfortunately incumbent on the evaluator to undergo the necessary training. It is unfair to all stakeholders not to provide a fair and accurate rating. The AMA guides attempt to provide a method whereby several physicians can come to similar conclusions using the same facts. Unfortunately, this is frequently not the case, because many impairment ratings are done by physicians who do not bother to understand the entire volume and the multiple ways in which a patient can be evaluated. Obviously, these physicians see a picture of the anatomic part to be rated and never stray from that page. Physicians are also at cross-purposes with attorneys. The evaluating physician must remember that the impairment rating is only one part of an administrative process resulting in a
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decision whether to award a monetary settlement to the claimant. The adjudicatory process involves either an administrative law judge or a jury. In addition, many times the evaluating physician is required to give a deposition or even testify in court. Because close adherence to the AMA guides increases the likelihood that the rating will be given weight, it is important to use the prepared report charts, especially in the upper extremity. The administrative system believes that physicians have all the answers when it comes to impairment, apportionment, and causation, and obviously this is not true. In doubtful cases, the physician should not attempt to make estimates or statements that are not justifiable. Apportioning in a patient who never had an impairment rating before an injury may be impossible, and again this may be more of an administrative decision than a medical one. The independent physician should remain neutral and advocate neither for the patient nor for the insurance company or attorney. Fair and accurate impairment ratings are as much an obligation to physicians as treatment itself, and we as independent physicians must be as diligent in performing them as we are in caring for patients.
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Index A Abduction, hip, 291–292, 292f Ability(ies) defined, 398t evaluation of, 395–416 Accessory handles, 258, 259f Accommodation of work populations, process for, 195, 195f Acetaminophen, for arthritis of knee, 304 Achilles tendon overuse injuries, diagnosis and treatment of, 370–371 Acromioclavicular joint articulation of, 155 fracture-dislocations of, 189–190 Active range of motion (AROM), neck injuries in workers and, 55, 57–58, 58f Activities of daily living (ADLs) joint forces during, hip and knee, 281–284, 283f in wrist and hand evaluation, 233 Activity ability, in disability evaluation, 411–412 Acute herniated disk, 75–77, 76f, 77t, 78f treatment of, 77, 78f Adaptation, workplace, 87–93. See also Workplace adaptation Adduction, hip, 291–292, 292f Adhesive capsulitis, 190–191 ADLs. See Activities of daily living (ADLs) Adson’s test, 65 Adson’s maneuver, 65, 172 Aerobic capacity testing, FPE validity in, 404–405 AFOs. See Ankle foot orthoses (AFOs) Age as factor in internal joint forces for hip and knee, 277–279, 278f as factor in MSDs, 269 Age Discrimination Employment Act (1967), 400 Agency for Health Care Policy and Research (AHCPR), 56, 411 AMA. See American Medical Association (AMA) American Academy of Disability Evaluating Physicians, 413 American Academy of Orthopaedic Surgeons, 228 American College of Occupational and Environmental Medicine, Occupational Medicine Practice Guidelines of, 299, 301 American Heart Association, 401 American Medical Association (AMA), 115, 410 Guides to the Evaluation of Permanent Impairment of, 412–415
American National Standards Institute (ANSI), 216 American Physical Therapy Association, 400 American Psychological Association, 400 American Society for the Surgery of the Hand, 228, 230 American Society of Hand Clinicians, 230 Americans with Disabilities Act, 400, 409 Amputation, foot, partial, in diabetics, 392 Analgesia/analgesics, opioid, for hip pain, 301 Analytic epidemiology, 5–9, 6f–8f, 8t case-control study, 7, 7f cohort study, 6–7, 6f cross-sectional study, 7–8, 8f, 8t randomized trials, 8–9, 8f Anatomic variation as factor in internal joint forces for hip and knee, 279 Anatomic/biomechanical abnormalities, sports-related foot and ankle injuries due to, 334–335, 335f Anesthesia/anesthetics local injection, in elbow evaluation, 180 in shoulder instability examination, 187–188 Ankle, 329–393. See also Foot and ankle disorders; Foot and ankle injuries arthrodesis of, indications for, 385 arthrology of, 342–343 arthrosis of after fracture, workplace adaptation of workers with, 390 diagnosis and treatment of, 369–370 biomechanical demands of, in workplace, 384 biomechanics of, 343–345, 346f calcaneocavus of, abnormal ROM of, after foot and ankle injuries, 385 chronic pain of, diagnosis and treatment of, 368–370 equinus of, after foot and ankle injuries, 384–385 fractures of, workplace-related, occult fractures, 355–356, 356f impingement lesion of, anterolateral, workplace-related, 355 instability of after sprain, 354, 354f chronic, 367 lateral, impingement syndrome of, diagnosis and treatment of, 369 loose bodies in, diagnosis and treatment of, 369 medial, burning pain around, case study, 386 overuse injuries of, diagnosis and treatment of, 370–372
Ankle—Cont’d plantar flexion and dorsiflexion of, limited ROM with, after foot and ankle injuries, 385 ROM of, 345–347, 346f sprains of diagnosis and treatment of, 367–368 workplace adaptation of workers with, 389 workplace-related, 353–355, 354f, 355f ankle instability after, 354, 354f grading of, 353 impingement lesion, 355 osteochondral lesions of talus, 355, 355t persistently painful, 353–354 tear of peroneus longus or brevis tendon, 354–355, 355f treatment of, 353 tendon injuries around, diagnosis and treatment of, 370–372 workplace-related injuries of, 352–356 fractures, 352–353, 352f sprains, 353–355, 354f, 355f. See also Ankle, sprains of Ankle foot orthoses (AFOs), 383, 386, 391, 392f Ankle joint, 342 movement transfer of, 345 rotational axis of, 345 Ankle joint complex motion, 345–347, 346f restraints of, 347 rotational axis and movement transfer of ankle joint, 345 ANSI. See American National Standards Institute (ANSI) Antalgic gait pattern, 290 Anterior atlantodens interval, 82 Anterior drawer test, 295–296, 296f Anterior instability, of shoulder, evaluation of, 171, 171f Anterior talofibular ligament (ATFL), function of, 367 Anthropometric considerations, in workplace adaptation for shoulder disorders, 204–206, 205f, 206f Antidepressant(s), for low back pain, 131 Antifatigue mats contaminants effects on, 319–320 for jobs requiring prolonged standing, 319–320 Anti-inflammatory drugs, nonsteroidal (NSAIDs) for hip arthritis, 299 for low back pain, 129 Apley test, 295, 295f Apple Computers QuickTime, 201 Apportionment, in disability evaluation, 412
Index
418
Arch(es), foot, 343, 344f Arm rests, in workplace adaptation for shoulder disorders, 207 AROM. See Active range of motion (AROM) Arthritis of hip, treatment of, 299, 301f of knee, treatment of, 304–305, 305f, 306f of lower extremity, 270 rheumatoid. See Rheumatoid arthritis Arthrodesis(es), indications for, 385 Arthrology, of foot and ankle, 342–343 Arthroscopy in hip evaluation, 297 in knee evaluation, 297 Arthrosis, ankle after fracture, workplace adaptation of workers with, 390 diagnosis and treatment of, 369–370 Articulation(s), elbow, 163–164, 163f ASO brace, 353 Assessment, defined, 398t ATFL. See Anterior talofibular ligament (ATFL) “Athlete’s foot,” 381 Atrophy deltoid, 168, 168f of fat pad, diagnosis and treatment of, 374–375 shoulder-related, 168–169, 168f Avascular necrosis, of hip, treatment of, 301, 302f Axial compression test, 64
B Babinski’s sign, 60, 64f Back, lower, 95–144 Back pain problems related to described, 97 disability due to, 103–104, 104f epidemiologic studies of, 97–99, 98f implications of, 104–105 incidence of, 99–100, 99f occupational and other relevant exposures, 97–98 prevalence of, 99–100, 99f risk factors for, 100–102 structural pathology and, 100–101 tissue injury and, 100–101 work-related, reporting of, 102–103 Baltimore Therapeutic Equipment Primus FPE, 402 Baltimore Therapeutic Equipment Work Simulator, 403 Bankart procedure, for shoulder instability, 188 Barium swallow, in neck injury evaluation in workers, 69 “Belly press,” 170 Bennett Hand-Tool Dexterity Test, 234 Best Evidence Synthesis on Traumatic Mild Injury, 26 Biomechanic(s) of cervical and thoracic spine, 41–54. See also Cervical spine; Thoracic spine of elbow, 162–166 of neck, 41–42, 41f–44f of shoulder, 155–162
Biopsychosocial model, of work-related MSDs, 13–14, 14f Black nail, 381 Blister(s) of foot, 381 of toe, safety footwear and, case study, 388, 388f Body link sizes, as fractions of total stature, 197, 197t Body masses, for males and females ages 18 and over, 197, 198t Body segment distance, from proximal joint center of gravity, 197, 197t Body segment weights, as percentage of total body mass, 197, 197t Body supports, in workplace adaptation for shoulder disorders, 207 Bone(s) cuneiform, 341–342, 341f of foot, 341–342, 341f tarsal, of midfoot fractures, workplace-related, 360 Bone and Joint Decade (2000–2010) initiative, 97 Bone scans, in neck injury evaluation in workers, 69 Bouchard’s nodes, 245 Brace(s), ASO, 353 Brachial plexus, 59 Brachioradialis reflex, inverted, 62 Bristow procedure, for shoulder instability, 188 Bureau of Labor Statistics, 309, 351 Bursitis lower extremity, 269–270 trochanteric, treatment of, 301
C CAI. See Chronic ankle instability (CAI) Calcaneofibular ligament (CFL), function of, 367 Calcaneous, 341, 341f abnormal ROM of, after foot and ankle injuries, 385 fractures of diagnosis and treatment of, 372–373 workplace-related, 356–359, 357f, 358f Callus(es), of foot, 380–381 CAM walker boot, 358 Canon, W., 13 Capacity, defined, 398t, 402 Capsulitis, adhesive, 190–191 Carpal ganglia, 246, 246f Carpal joint, force through, 223–224, 223f Carpal tunnel syndrome (CTS), 211–218, 238–239 described, 238 diagnosis of, 238–239 treatment of, 239 Carpal Tunnel Syndrome Questionnaire, 228 Carpet installation clinical responses to, biomechanical basis for, case study, 311–314, 312f–314f “stretcher adapter” in, 318–319
Carpet installers injury/disease prevention plan for, 315–319, 316f–318f lower extremity trauma in, case study, 311–314, 312f–314f NIOSH ALert for, 318, 319 Carrying load low back pain associated with, work adaptations for, 138–139, 140f, 141f in workplace, 384 Cartesian coordinate system, 254, 254f Case-control study, in analytic | epidemiology, 7, 7f Causalgia, 375 Causation, in disability evaluation, 412 CBT. See Cognitive behavioral therapy (CBT) Cervical degenerative disk disease, 77–79, 80f, 81f spondylitic myelopathy, 78–79, 80f, 81f spondylosis, 77–78 Cervical spine biomechanics of, 41–54 disorders of. See also specific disorders, e.g., Neck sprain acute herniated disk, 75–77, 76f, 77t, 78f cervical degenerative disk disease, 77–79, 80f, 81f hyperextension injuries, 82–83 neck sprain, 75 rheumatoid arthritis, 79, 81–82, 82f spondylosis, 77–78 treatment of, 73–86 algorithm for, 83–86, 84f, 85t whiplash injury, 82–83 lower, biomechanics of, 46, 49f–53f, 53t, 54, 54t upper, occiput/C2, biomechanics of, 42, 44f–48f, 44t, 45t CFL. See Calcaneofibular ligament (CFL) Charcot deformity, 375 Charcot neuroarthropathy, in diabetics, 391–392, 392f Chopart’s joint, 342, 377 Chronic ankle instability (CAI), sports-related foot and ankle injuries due to, 335 Chronic regional pain syndrome, workplacerelated, 365 “Claims processor” job, for identifying and controlling shoulder and neck stressors, sample documentation and analysis of, 88t Clavicle, fracture-dislocations of, 189 Clinical Guidelines for the Management of Acute Low Back Pain, 14 Clonus, 60 Cochrane review of multidisciplinary biopsychosocial rehabilitation, 129 Cognitive behavioral therapy (CBT), for NSLBP, 127f, 128 Cohort study, in analytic epidemiology, 6–7, 6f Common peroneal nerve, entrapment of, 376 Complex regional pain syndrome (CRPS), 247
Index
Computed tomography (CT) in elbow evaluation, 179, 180f in hip evaluation, 296 in low back pain evaluation, 119f, 120 in neck injury evaluation, 67–68, 67f, 68f in shoulder evaluation, 175 Concurrent validity, defined, 403t Confidence limits, in statistical analysis, 9–10 Confounding, 5–6 defined, 5 Constraint(s) of elbow, 164–165 of glenohumeral joint, 158–161, 160f Construct validity, defined, 403t Contaminant(s), impact on antifatigue properties of floor mats, 319–320 Content validity, defined, 403t Copenhagen Neck Functional Disability Scale, 66 Corns, 380 Corticosteroids, for low back pain, 131 Cox proportionate hazards model, 9 Crawford Small Parts Test, 234 Criterion validity, defined, 403t Cross-sectional study, in analytic epidemiology, 7–8, 8f, 8t Crouching, in workplace, 384 CRPS. See Complex regional pain syndrome (CRPS) Crush injury, of foot, workplace-related, 365 CT. See Computed tomography (CT) CTS. See Carpal tunnel syndrome (CTS) Cuboid, 341f, 342 Cumulative Load Theory, of musculoskeletal injury causality, 135 Cuneiform bones, 341–342, 341f Cutting tools, 252–253, 253f, 254t Cyst(s) mucous, of wrist and hand, 246–247 retinacular, 246
D DASH (disabilities of the arm, shoulder, and hand) test, 228 de Quervain disease, 237, 237f, 245, 245f Deep peroneal nerve, entrapment of, 376 Degenerative joint disease, of shoulder, 191 Deltoid atrophy, 168, 168f Dermatome testing, in neck injury evaluation in workers, 59, 59f Descriptive epidemiology, 4–5 Dexterity, in wrist and hand evaluation, 233–234, 233f, 234f Diabetes mellitus, foot problems in workers with, 391–392, 391f, 392f Diagnostic blocks about elbow, in elbow evaluation, 180 Dictionary of Occupational Titles (DOT), of U.S. Department of Labor, 399, 400t Differential Fatigue Theory, of musculoskeletal injury causality, 135 Digital flexor tendon sheath, 237, 238f Disability(ies) back pain–related, 103–104, 104f
defined, 397 evaluation of. See Disability evaluation low back pain–related, 136 Disability evaluation ethics associated with, 409–410 impairment determination in AMA guides in differences between fourth and fifth editions, 413 lower extremity impairments, 414–415 pain, 413 spine impairments, 413–414 upper extremity impairments, 414 principles of, 412–415 rating of, AMA guides in, 413–415 medical opinions required during, 410–412 apportionment, 412 causation, 412 date of permanent and stationary status, 410 diagnosis, 410–411 ongoing and future medical care requirements, 412 residual objective findings, 410 residual subjective complaints, 410 return-to-work determinations, 411 work and activity ability, 411–412 for neck injuries in workers, 55, 55t physician’s role in, 409–416 administrative considerations, 415 Disease stage, as factor in internal joint forces for hip and knee, 279, 279f DISI. See Dorsal intercalated segmental instability (DISI) Disk(s), herniated, acute, 75–77, 76f, 77t, 78f Disk degeneration hereditary influences on, 101 occupational influences on, 101–102 Diskcriminator, 231 Diskography, in low back pain evaluation, 122 Dislocation(s) foot, workplace-related, 362–364, 362f–364f of MTP joint, treatment of, 378 shoulder-related, 189–190 subtalar joint, diagnosis and treatment of, 372 Distal interphalangeal joint, osteoarthritis of, 246 Distal radius fracture, 242–243, 243f Distraction test, 64 Dorsal intercalated segmental instability (DISI), 224 “Dose-response” relationship, described, 87 DOT. See Dictionary of Occupational Titles (DOT) DOT Residual Functional Capacity battery, 403–404 Down syndrome, 4 DRE method. See Diagnosis-related estimate (DRE) method “Dropping sign,” 170 duToit capsulorrhaphy procedure, for shoulder instability, 188 Dynamic forces, 260–262, 260f–262f
Dynamic work, low back pain associated with, work adaptations for, 138–143, 139f–142f carrying, 138–139, 140f, 141f lifting and lowering, 139–143, 141f, 142f pushing and pulling, 138, 139f Dynamometric devices, isokinetic and isoinertia, in low back pain evaluation, 122
E Economic issues, in low back pain, 114–115 Edema of lower leg, after foot and ankle injuries, 386–387, 387f in wrist and hand evaluation, 228–229, 229f Elbow articulations of, 163–164, 163f biomechanics of, 162–166 anatomic considerations in, 162–164, 163f, 164t constraints, 164–165 developments in, 165 future directions in, 165 kinematics, 164 kinetics, 165 disorders of, 149–154. See also Elbow disorders evaluation of, 176–180 CT in, 179, 180f diagnostic blocks in, 180 diagnostic testing in, 178–180, 179f, 180f EMG in, 179–180 local anesthetic block in, 180 MRI in, 179 nerve conduction studies in, 179–180 patient history in, 176–177 physical examination in, 176f, 177–178, 177f radiography in, 178–179, 179f technetium bone scanning in, 180 muscles of, 164, 164t stiffness of, 176 tennis, 149 resistant, 152 Elbow disorders, 149–154 classification of, 149 entrapment neuropathies, 152, 177 epidemiology of, 149–150, 150t individual factors for, 151 in newspaper workers, 150, 150t occupational risk groups for, 149–150, 150t pathomechanisms of, 151–152 prevention of, 152 risk factors for, 150–151 social factors for, 151 tendinopathy, 177 work-related factors for, 150–151 Electrodiagnostic studies, in neck injury evaluation in workers, 69–71, 72t Electromyography (EMG) in elbow evaluation, 179–180 in low back pain evaluation, 122 in neck injury evaluation, 70 in shoulder evaluation, 176 surface, in analysis of job task demands, 202–203 “Elevated arm stress test,” 65
419
Index
420
Embase, 25 EMG. See Electromyography (EMG) Entrapment neuropathies about elbow, 177 common peroneal nerve, 376 deep peroneal nerve, 376 elbow and shoulder disorders and, 152 of foot and ankle, 375–377 jogger’s foot, 377 Morton’s neuroma, 377 posterior tibial nerve and branches, 376–377 saphenous nerve, 377 superficial peroneal nerve, 376 sural nerve, 377 Valleix phenomenon, 375–376 Epidemiologic concepts analytic epidemiology, 5–9, 6f–8f, 8t. See also Analytic epidemiology descriptive epidemiology, 4–5 measures of disorder frequency in, 3–4 in MSDs, 3–11 statistical issues, 9–11, 10f, 11t Epidemiology analytic, 5–9, 6f–8f, 8t. See also Analytic epidemiology defined, 97 descriptive, 4–5 Equipment described, 89 work-related, in analysis of job task demands, 202 Ergonomics for NSLBP, 128–129 in shoulder disorder prevention, 162 Ergos Work Simulator, 402 Estimates, in statistical analysis, 9–10 Ethics, disability evaluation-related, 409–410 European Guidelines 2005, 128, 129 Evaluation, defined, 398t Event-based observations, time-based observations vs., in analysis of job task demands, 203 Evidence-based medicine (EBM) techniques, in neck injury evaluation in workers, 56 Exercise, for NSLBP, 127f, 128 Exercise laboratories, of Veterans Affairs Health Care System, 401 Exostosis, subungual, 381 Experimental study designs, clinical trials, 8–9, 8f Exposure-response relationship, 195–200, 195f, 196f, 197t, 198t, 199f, 200f, 200t biomechanics of, 196–197, 196f, 197t, 198t described, 195–196, 195f limitations in, 197 worker capacity and, 198–200, 199t, 200f, 200t, 201f Extensor lag, defined, 294, 294f External forces, acting on foot, 347 Extremity(ies), lower, 265–416. See also Ankle; Foot; Hip; Knee; Lower extremity
F Face validity, defined, 403t
Fasciitis, plantar diagnosis and treatment of, 374 workplace adaptation of workers with, 390 Fat pad atrophy of, diagnosis and treatment of, 374–375 inflammation of, diagnosis and treatment of, 375 Fatigue MSDs due to, prevention of, 197–198 muscular, as factor in elbow and shoulder disorders, 152 work-related conditions affecting, 195–200. See also Exposure-response relationship FCEs. See Functional capacity evaluations (FCEs) Federal Rules of Evidence, 56 Federal Uniform Guidelines of Employee Selection Procedure (1978), 400 Finger(s) joint injuries of, 242 trigger, 237–238, 238f Finger escape sign, 62 Finkelstein test, 245 Fissure(s), toenail-related, 382 Flexibility, lack of, sports-related foot and ankle injuries due to, 335 Flexor hallucis longus tendon overuse problems, diagnosis and treatment of, 371 Floor-to-waist lifting, in workplace, 384 Foot, 329–393. See also Foot and ankle disorders; Foot and ankle injuries amputation of, partial, in diabetics, 392 anatomy of, 341–342, 341f arches of, 343, 344f arthology of, 342–343 “athlete’s,” 381 biomechanic(s) of, 343–345, 346f biomechanical demands of, in workplace, 384 bones of, 341–342, 341f external forces acting on, 347 fractures of, 356–362, 357f–359f, 361 workplace-related, 356–362 calcaneus fractures, 356–359, 357f, 358f metatarsal fractures, 360–360f midfoot fractures, tarsal bones of, 360 phalangeal fractures, 361–362 sesamoid fractures, 360–361, 361f talus fractures, 359–360, 359f ground reaction forces and pressure distribution on, 344f, 348 internal forces acting on, 344f, 347–348 jogger’s, 377 osteology of, 341–342, 341f plantar surface of, neuropathic ulcerations on, in diabetics, 391, 391f shoe selection considerations for, 348–349, 348f workplace-related injuries of, 356–365 CRPS, 365 crush injuries, 365 dislocations, 362–364, 362f–364f fractures, 356–362, 357f–359f, 361f. See also Foot, fractures of MTP joint injuries, 363–364, 364f
Foot—Cont’d nerve injuries, 364 sprains, 362–364, 362f–364f TMT joint injuries, 362–363, 362f, 363f Foot and ankle disorders, 329–393. See also Foot and ankle injuries blisters, 381 calluses, 380–381 corns, 380 diagnosis and treatment of, 367–382 ankle pain, chronic, 368–370 ankle sprains, 367–368 forefoot problems, 379–380 fractures, 372–374 midfoot injuries, 377–379 nerve injuries, 375–377 subtalar joint injuries, 372 tendon injuries around ankle, 370–372 epidemiology of, 331–339 military-related injuries, 332–333, 333f sports-related injuries, 333–337, 334t, 335f, 336f. See also Sports, foot and ankle injuries related to studies of, methodology of, 331 work-related injuries, 331–332 fungal infections, 381 skin conditions, 380–381 toenail-related, 381–382 warts, 381 workplace adaptation of workers with, 383–393 ankle arthrosis after fracture, 390 ankle sprain, 389 for common conditions, 389–393, 391f, 392f diabetics, 391–392, 391f, 392f foot orthoses, 389 footwear, 383–384, 383t, 387–388, 387f, 388f forefoot pain–related, 391 heel pain, 390 midfoot arthrosis and pain, 390–391 tibialis posterior tendon insufficiency, 390, 391f venous and lymphatic disorders, 392–393 workplace-related, 351–366. See also Ankle, workplace-related injuries of; Foot, workplace-related injuries of approach to patient with, 351–352 epidemiology of, 351 prevalence of, 351 return to work after, 365 types of, 352–365 Foot and ankle injuries. See also Foot and ankle disorders deficits after, 384–387, 385f, 387f abnormal ROM, 384–385, 385F edema of lower leg, 386–387, 387f foot and ankle pain, 386 neurologic deficit, 385–386 Foot and ankle movement, measurement of, 343–345. See also Ankle joint complex motion clinical and functional assessment in, 343 three-dimensional assessment in, 343–345 Foot and ankle pain, after foot and ankle injuries, 386
Index
Foot arch supports, 349 Foot orthoses (FOs), at workplace, 389 Footwear. See Shoe(s) Force(s) external, acting on foot, 347 internal, acting on foot, 344f, 347–348 measurement of, in analysis of job task demands, 202 prediction of, in analysis of job task demands, 203–204 Forearm rests, in workplace adaptation for shoulder disorders, 207 Forefoot painful, conditions of, workplace adaptation of workers with, 391 problems related to, 379–380 FOs. See Foot orthoses (FOs) FPE. See Functional performance evaluation (FPE) Fracture(s) about ankle, workplace-related, 352–353, 352f ankle arthrosis after, workplace adaptation of workers with, 390 calcaneal diagnosis and treatment of, 372–373 workplace-related, 356–359, 357f, 358f distal radius, 242–243, 243f foot and ankle, diagnosis and treatment of, 372–373 heel spur, diagnosis and treatment of, 374 hip, treatment of, 299, 300f Massoneuve, 353 metatarsal diagnosis and treatment of, 378–379 workplace-related, 360–360f occult, of ankle, workplace-related, 355–356, 356f phalangeal, workplace-related, 361–362 scaphoid, 243–244, 243f sesamoid, workplace-related, 360–361, 361f shoulder-related, 189–190 stress, of foot and ankle, diagnosis and treatment of, 373–374 talar diagnosis and treatment of, 372 workplace-related, 359–360, 359f tarsal navicular, stress, 374 tibial pilon, 352 wrist and hand, 242–244, 243f distal radius, 242–243, 243f metacarpals, 244 phalanges, 244 scaphoid, 243–244, 243f Frozen shoulder, 190–191 FSU. See Functional spinal unit (FSU) Functional assessment, of wrist and hand, 232–234 Functional Assessment Screening Test, 404 Functional capacity evaluations (FCEs), 397–398. See also Functional performance evaluation (FPE) Functional performance evaluation (FPE), 397–407 of aerobic capacity, reliability of, 402 characteristics of, 400–406, 403t
Functional performance evaluation (FPE)—Cont’d professional practice standards for, 400–406, 403t practicality, 405–406 reliability, 401–402 safety, 401 utility, 406 validity, 402–405, 403t. See also Validity, of FPE purposes of, 398–400, 400t self-reported functioning, 399–400 test components of, 399 validity of, legal constraints challenging, 400 of work-related activities, reliability of, 401–402 work-related performance tests, 399 Functional performance testing, 397–407. See also Functional performance evaluation (FPE) Functional Range of Motion Assembly Test, 402 Functional spinal unit (FSU), 107–110, 108f, 109f, 109t anterior portion of, 107, 108f, 109t ligaments in, 109–110 posterior portion of, 107–109, 109f Fungal infections of foot, 381 of toenails, 382 F-wave response tests, 71, 72t
G Gamekeeper’s thumb, 242, 242f Ganglion(a) retinacular, volar, 246 wrist and hand, 246–247, 246f carpal ganglia, 246, 246f mucous cysts, 246–247 retinacular cysts, 246 ulnar tunnel, 239 Gender, as factor in internal joint forces for hip and knee, 277–279, 278f Gibson Approach to FPE, 404 Glenohumeral joint, biomechanics of, 158–162, 159f, 160f, 161t, 162f animal models, 162 constraints, 158–161, 160f disability prevention through ergonomics, 162 kinematics, 158, 159f kinetics, 161 mechanical properties of articular cartilage and ligaments, 161–162, 161t, 162f Glenohumeral ligaments, 160–161, 160f Goniometer(s), in low back pain evaluation, 122 Grip and release test, 62 Guides to the Evaluation of Permanent Impairment, of AMA, 412–415
H Hallux limitus, 385, 385f Hallux rigidus, 379 Hallux seseamoid stress fractures, 373–374 Hallux valgus, 379 Hammer toes, 379–380 Hand, 209–263. See also Wrist and hand
Hand tools biomechanical aspects of, 249–265 manual screwdrivers, 249–251, 249f, 251f Phillips head screws, 251f, 252, 252t pliers and cutting tools, 252–253, 253f, 254t power tools, 249, 253–262. See also Power hand tools recommendations, 263 screwdriver blades and screw heads, 251–252, 251f, 252f, 252t slotted screws, 251–252, 252f, 252t Torx head screws, 251f, 252, 252t manual, 249 Hand-arm vibration syndrome, 213, 239–240 Handle force model, dynamics of, 261–262, 261f Hawkins impingement test, 171 Hazard, defined, 9 Heel pain diagnosis and treatment of, 374–375 workplace adaptation of workers with, 390 Heel pain syndrome, diagnosis and treatment of, 374 Heel spur(s), diagnosis and treatment of, 374 Heel spur fracture, diagnosis and treatment of, 374 Hematoma(s), subungual, 381 Heredity, as factor in lower extremity osteoarthritis, 270 Herniated disk, acute, 75–77, 76f, 77t, 78f treatment of, 77, 78f Herniation(s), soft disk, types of, 75, 76f Hindfoot, stress fracture of, 373 Hip, 267–327 abduction of, 291–292, 292f adduction of, 291–292, 292f arthritis of, treatment of, 299, 301f avascular necrosis of, treatment of, 301, 302f biomechanics of, 273–287 kinematics, 273–274, 274t kinetics, 274–277, 275f reducing internal joint load, 277–285, 278f–285f. See also Internal joint forces, on hip and knee clinical evaluation of, 289–297 CT in, 296 imaging in, 296 MRI in, 296, 301 patient history in, 289, 289t physical examination in, 289–292, 290f–292f radiography in, 296, 299, 300f fractures of, treatment of, 299, 300f kinematics of, 273–274, 274t kinetics of, 274–277, 275f osteoarthritis of, 270–271 treatment of, 299, 301f osteonecrosis of, treatment of, 301, 302f pain of severe, treatment of, 299, 301 treatment of, 301 range of motion of, 290–291, 291f rotation of, 290–291, 291f sprains and strains of, treatment of, 301 trochanteric bursitis of, treatment of, 301 work-related problems of, treatment of, 299–301, 300f–302f
421
Index
422
Hip extension, 291, 292f Hippocratic Oath, 409 Hoffman’s sign, 60, 64f Holding work, low back pain associated with, work adaptations for, 137, 138f Homer syndrome, 82 “Horn blower’s” sign, 170, 170f Humerus, proximal, fracture-dislocations of, 190 Hyperextension injuries, 82–83 treatment of, 83 Hypothenar hammer syndrome, 213
I Imaging in hip evaluation, 296 in knee evaluation, 296–297 Impairment evaluation, for neck injuries in workers, 55 Impingement lesion, anterolateral, of ankle, workplace-related, 355 Impingement syndrome, 185–187 of lateral ankle, diagnosis and treatment of, 369 Incidence, defined, 25 Incidence rate, defined, 4 Industrial back “injury” incident reports and claims filing, 102–103 Industrial Commission of Ohio, 311 Inflammation, of fat pad, diagnosis and treatment of, 375 Information processing, in wrist and hand evaluation, 232–233 Ingrown toenails, 381 In-line power drivers, 256f, 257–258 Instability anterior, of shoulder, 171, 171f shoulder, 185–189. See also Shoulder(s), instability of Internal joint forces on foot, 344f, 347–348 on hip and knee, 277–285, 278f–285f during ADLs, 281–284, 283f squatting, 281–283, 283f stair climbing, 283–284 walking, 283–284 factors affecting, 277–279, 278f, 279f reduction of, 280–281, 280f–282f lever arm reduction in, 280, 280f, 281f synergic movement and muscular coactivation in, 280–281, 282f task variables in, 284–285, 285f in vivo direct measurement of, hip and knee, 277 International Classification of Diseases, 149, 411 International Standards Organization (ISO), 216 Interphalangeal joint, proximal, osteoarthritis of, 245–246 Interview(s) patient, in neck injury evaluation in workers, 56 worker and supervisor, 202 Ischemia, local, 152 Isernhagen Work Systems FCE, 404 Isernhagen Work Systems FPE, 402
ISO. See International Standards Organization (ISO) Israeli Defense Forces Medical Corps, 332
J Job documentation, 200 Job rotation, 137 Job stresses, physical, in analysis of job task demands, 202–204, 203f. See also Physical job stresses, in analysis of job task demands Job task demands analysis of, 200–204, 202t physical job stresses in, 202–204, 203f. See also Physical job stresses, in analysis of job task demands interviews, 202 job documentation, 200 measurements of work station and equipment, 202 observations, 200–201 video recordings, 201–202 Jogger’s foot, 377 Joint(s) foot and ankle, 342–343. See also specific joint wrist and hand, constraint and stability of, 219 Joint forces, wrist and hand, 221–223, 223f Joint loads, estimation of, 198, 200
K Kienböck disease, 223 Kinematics elbow, 164 glenohumeral, 158, 159f hip, 273–274, 274t knee, 273, 273t spine, 110, 110f, 111f Kinetics elbow, 165 glenohumeral, 161 hip and knee, 274–277, 275f spine, 110–112, 111f, 112f Knee, 267–327 analytical joint models of, 275–277, 275f, 276f biomechanics of, 273–287 kinematics, 273, 273t kinetics, 274–277, 275f reducing internal joint load, 277–285, 278f–285f. See also Internal joint forces, on hip and knee clinical evaluation of, 289–297 arthroscopy in, 297 MRI in, 297 patient history in, 289, 289t physical examination in, 292–296, 292f–296f radiography in, 296 jobs requiring use of, injury/disease prevention plan for, 315–319, 316f–318f joint forces on, in vivo direct measurement of, 277 kinematics of, 273, 273t kinetics of, 274–277, 275f osteoarthritis of, 271
Knee—Cont’d treatment of, 304–305, 305f, 306f pain of anterior, treatment of, 306 nonspecific, treatment of, 306 sprains of, treatment of, 303–304, 303f, 304f tendinitis of, treatment of, 305–306 varus/valgus deformity of, 292, 292f work-related problems of, treatment of, 301–306, 303f–306f Knee injuries acute, workplace-related, chronic pain, discomfort, and work restrictions due to, case study, 320–325, 321t, 324t ligamentous, treatment of, 303–304, 303f, 304f meniscal, treatment of, 301–303, 303f Knee joint stability, testing of, 295–296, 295f, 296f Kneeling, in workplace, 384
L Laboratory studies, in neck injury evaluation in workers, 71 Lachman test, 295–296, 296f Lateral cord of brachial plexus, 59 Lateral elbow syndrome, 149 Lateral humeral epicondylalgia, 149 Leg(s), lower, edema of, after foot and ankle injuries, 386–387, 387f Legend of variable notation, 255t Lesion(s). See specific types, e.g., Osteochondral lesions Lhermitte’s sign, 60, 81 Liberty Mutual Insurance Company, 136 Liberty Mutual Insurance Company database, 100 Lidocaine injection tests, in shoulder evaluation, 175, 176f Lifting, floor-to-waist, in workplace, 384 Lifting and lowering, low back pain associated with, work adaptations for, 139–143, 141f, 142f Ligament(s) glenohumeral, 160–161, 160f spine, 109–110 wrist and hand, constraint of, 219 Lisfranc’s joint, 342 injuries of, diagnosis and treatment of, 378 Local anesthetic injection, in elbow evaluation, 180 Local ischemia, 152 Loge of Guyon, 239 Long-tract signs, in neck injury evaluation in workers, 60, 62, 64f, 65f Low back, 95–144 Low back pain causes of, 135–136 theories of, 135–136 vs. exacerbation, 98–99 chronic, treatment of manipulation in, 129 multimodal programs in, 129, 130t control of, 135–136 costs related to, 136 differential diagnosis of, 122–123
Index
Low back pain—Cont’d disabilities due to, 136 duration of, treatment goals related to, 126 epidemiology of, 97–106 evaluation of blue flags in, 115 CT in, 119f, 120 diskography in, 122 EMG in, 122 initial, 113–124 laboratory studies in, 122 mechanical testing in, 122 MRI in, 120–121, 120f, 121f myelography in, 117f, 120 patient history in, 113–115, 113t physical examination in, 115–118, 116f–118f patient on side, 118 patient prone, 118 patient sitting, 116, 116f patient standing, 115–116 patient supine, 116–118, 117f, 118f radiography in, 119–120 radionuclide bone scan in, 121 red flags in, 113–115, 113t specialized examinations in, 117f–121f, 119–122 ultrasonography in, 121–122 yellow flags in, 114–115 nature of, 135 nonspecific, 125 potentially serious conditions related to, red flags for, 113–115, 113t prevalence of, 136 problems related to, extent of, 136 psychosocial and economic issues associated with, 114 specific, 125 treatment of, 125–134 antidepressants in, 131 complications of, 132 corticosteroids in, 131 models for, 125 muscle relaxants in, 129, 131 NSAIDs in, 129 occupational health guidelines in, 125 opioids in, 131 patient expectations in, 125–126 surgical, 131–132 workplace adaptation for, 135–144 dynamic work, 138–143, 139f–142f. See also Dynamic work, low back pain associated with, work adaptations for holding work, 137, 138f seated work, 137 static work, 136–137 Lower back, 95–144. See also under Low back pain Lower extremity, 265–416. See also Ankle; Foot; Hip; Knee epidemiology of, 269–272, 269t, 270t definitions associated with, 269 occupational illness, 269 occupational injuries, 269
Lower extremity disorders age-related, 269 rating of, AMA guides in, 414–415 workplace-related, 309–327 adaptations recommended for, 315–325, 316f–318f, 321t, 324t in carpet installers, 311–314, 312f–314f injury/disease prevention plan for, 315–319, 316f–318f industry-specific data, 309 knee injury, chronic pain, discomfort, and work restrictions due to, case study, 320–325, 321t, 324t prevalence of, 309 vascular problems, 314–315 Lowering, low back pain associated with, work adaptations for, 139–143, 141f, 142f Lunotriquetral interval injury, 241 Lymphatic disorders, foot and ankle–related, workplace adaptation of workers with, 392–393
M Magnetic resonance imaging (MRI) in elbow evaluation, 179 in hip evaluation, 296, 301 in knee evaluation, 297 in low back pain evaluation, 120–121, 120f, 121f in neck injury evaluation, 68, 68f–70f in shoulder evaluation, 174–175, 175f Maine-Seattle back pain disability questionnaire, 9 Manipulation, for chronic low back pain, 129 Manual hand tools, 249–253, 249f, 251f–253f, 252t, 254t Manual screwdrivers, 249–251, 249f, 251f handle diameter of, 250–251, 251f handle length of, 249–250, 249f Massoneuve fractures, 353 Mat(s), antifatigue contaminants effects on, 319–320 for jobs requiring prolonged standing, 319–320 Maximum voluntary contraction (MVC), 150 McGill Pain Profile, 227 McGill Pain Questionnaire, 232 McGregor line, 82 McMurray test, 294, 294f Mechanical assists, in workplace adaptation for shoulder disorders, 206–207 Mechanical testing, in low back pain evaluation, 122 Medial cord of brachial plexus, 59 Medical history, as factor in internal joint forces for hip and knee, 279, 279f Medical Outcomes Study, 66 MEDLINE, 25 Meniscal injuries, treatment of, 301–303, 303f Metabolic equivalent intensity levels, 399 Metacarpal(s), fractures of, 244 Metatarsal(s), 341f, 342
423
Metatarsal fractures diagnosis and treatment of, 378–379 stress fractures, 373 workplace-related, 360–360f Metatarsalgia, 380 Metatarsophalangeal (MTP) joint, 342–343 Metatarsophalangeal (MTP) joint injuries sprains and dislocations, treatment of, 378 workplace-related, 363–364, 364f Michigan Hand Questionnaire, 228 Midfoot, arthrosis and pain of, workplace adaptation of workers with, 390–391 Midfoot injuries, 377–379 Midtarsal sprains, 377–378 Military shoes, at workplace, 388 Military-related foot and ankle injuries, 332–333, 333f Minnesota Manual Dexterity Test, 234, 234f Moberg Pick Up test, 233 Moment(s), reduction of, 280–281, 280f–282f Monofilament(s), Semms-Weinstein, 231, 414 Morton’s neuroma, 377 MOS 36-Item Short Form Health Survey (SF-36), 66 Motion, wrist and hand, 219–220 Motor strength examination, in neck injury evaluation in workers, 59–60, 60f–62f, 60t MRI. See Magnetic resonance imaging (MRI) MSDs. See Musculoskeletal disorders (MSDs) MTP joint injuries. See Metatarsophalangeal (MTP) joint injuries Mucous cysts, of wrist and hand, 246–247 Multivariate Interaction Theory, of musculoskeletal injury causality, 136 Muscle(s) elbow, 164, 164t mechanical failure of, 152 nerve and main root supply of, 71, 72t shoulder, 157–158, 157t wrist and hand, 221–223, 223f Muscle grading, 170, 170t Muscle performance testing, in wrist and hand evaluation, 229–230, 230f Muscle relaxants, for low back pain, 129, 131 Muscular fatigue, as factor in elbow and shoulder disorders, 152 Musculoskeletal disorders (MSDs) age as factor in, 269 epidemiologic concepts in, 3–11. See also Epidemiologic concepts frequency of, measures of, 3–4 of hand and wrist, 211–218, 211f, 212f, 214t, 215t. See also Wrist and hand disorders localized fatigue and, prevention of, 197–198 of lower extremity, workplace-related, 309–314, 310f, 312f–314f of neck, in workers, evaluation of, 55–72. See also Neck, evaluation of occupational, defined, 269 psychologic and psychosocial factors associated with, 14–15 psychosocial aspects of, 13–18. See also Psychosocial factors, MSDs and psychosocial interventions for, 16–17, 17f
Index
424
Musculoskeletal disorders (MSDs)—Cont’d risk factors for, work-related conditions affecting, 195–200. See also Exposureresponse relationship in workers, neck pain associated with, 25–40. See also Neck pain, in workers, epidemiology of Musculoskeletal pain, prevalence of, 397 MVC. See Maximum voluntary contraction (MVC) %MVC. See Percentages of maximum voluntary contraction (%MVC) Myelography in low back pain evaluation, 117f, 120 in neck injury evaluation, 68–69, 71f Myelopathy, spondylosis with, 78–79, 80f, 81f Myeloradiculopathy, 78
N National Academy of Sciences, 213 National Center for Health Statistics, statures and body masses for males and females ages 18 and over, 197, 198t National Institute for Occupational Safety and Health (NIOSH), 139 National Institute for Occupational Safety and Health (NIOSH) Report on Musculoskeletal Disorders (MSDs) and Workplace Factors, 397 Navicular, 341, 341f Neck, 23–93 anatomy of, 73–75, 74f, 75f biomechanics of, 41–42, 41f–44f disorders of, workplace adaptation to, 87–93. See also Workplace adaptation, to MSDs, neck-related disorders evaluation of, 55–72 AROM in, 57–58, 58f barium swallow in, 69 bone scans in, 69 CT in, 67–68, 67f, 68f disability examination in, 55, 55t electrodiagnostic studies in, 69–71, 72t EMG in, 70 evidence-based medicine in, 56 imaging studies of spine in, 66–69, 66f–71f impact-related, 65–66, 66t impairment evaluation in, 55 laboratory screening in, 71 MRI in, 68, 68f–70f myelography in, 68–69, 71f nerve conduction studies in, 71, 72t neurologic examination in, 59–65, 59f–65f, 60t, 63t long-tract signs, 60, 62, 64f, 65f motor strength examination, 59–60, 60f–62f, 60t reflex examination, 60, 62, 63f–65f, 63t sensory examination and dermatome testing, 59, 59f specialized physical tests, 64–65, 65f palpation in, 59 patient history in, 56–57, 57t patient interview in, 56
Neck—Cont’d physical examination in, 57–59, 58f PROM in, 58 radiography in, 66–67, 66f, 67f red flags in, 57, 57t ROM in, 57–59, 58f Spurling’s test in, 59 SSEPs in, 71 standard examination in, 55 MSDs of, in workers, evaluation of, 55–72. See also Neck, evaluation of Neck Disability Index, 66 Neck pain anatomy related to, 73–75, 74f, 75f causes of, 73, 73t defined, 25 factors associated with, 27, 28t, 29 in workers epidemiology of, review of, 25–40 article selection in, 26 critical review of literature in, 26 data synthesis in, 26 literature search in, 25–26 methods in, 25–26 purpose of, 25 relevance of, 35 results of, 26–35, 27f, 28t, 30t–34t selection and critical appraisal of articles in, 26–27, 27f incidence of, 29, 30t–31t prevalence of, 27, 28t risk factors for, 29, 30t–31t specific occupational groups, 29, 32t–34t, 35 factors associated with, 29, 32t–34t incidence of, 29, 35, 36t–37t prevalence of, 29, 32t–34t risk factors for, 35, 36t–37t Neck Pain and Disability Scale, 66 Neck sprain, 74f, 75, 75f prognosis for patients with, 75 treatment of, 75 Neck stressors, identification and control of, sample documentation and analysis of “claims processor” job in, 88t Neck-related pain syndromes, causes of, 73, 73t Neer “impingement sign,” 171, 171f Neer procedure, for shoulder instability, 188 Nerve(s). See specific nerve, e.g., Saphenous nerve Nerve conduction studies in elbow evaluation, 179–180 in neck injury evaluation, 71, 72t in shoulder evaluation, 176 Nerve entrapments, lower extremity, 270 Nerve injuries degrees of, 375 of foot and ankle, 375–377 classification of, 375 entrapment neuropathies, 375–377 workplace-related, 364 Neural network technique analysis of motion patterns, in low back pain evaluation, 122 Neuroarthropathy, Charcot, in diabetics, 391–392, 392f
Neurologic deficits, after foot and ankle injuries, 385–386 Neurologic examination, in neck injury evaluation in workers, 59–65, 59f–65f, 60t, 63t. See also Neck, evaluation of, neurologic examination in Neuroma(s), Morton’s, 377 Neuropathic ulcerations, on plantar surface of foot in diabetics, 391, 391f New Zealand Guidelines, 14 Newspaper workers, elbow problems in, 150, 150t Newton’s Third Law, 196, 196f NHANES I study, 270, 271 Nine Hole Peg Test, 233, 233f, 234 NIOSH. See National Institute for Occupational Safety and Health (NIOSH) NIOSH Alert, for carpet installers, 318, 319 Nonspecific low back pain (NSLBP), 125 acute prognosis of, 126 self-care for, 126 treatment of, evidence for, 126 natural history of, 126 recurrence of, 126 subacute, treatment of blue flags in, 127 interventions in, 127–129, 127f yellow flags in, 127 treatment of, 127–128, 127f CBT in, 127f, 128 combination therapy in, 128 ergonomic intervention in, 128–129 exercise in, 127f, 128 Nordic Health Questionnaire, 203 Northwick Park Neck Pain Questionnaire, 66 NSAIDs. See Anti-inflammatory drugs, nonsteroidal (NSAIDs) NSLBP. See Nonspecific low back pain (NSLBP)
O Observation(s), of workers performances, 200–201 Occlusion of superficial palmar branch of ulnar artery, 213 Occult fractures, of ankle, workplace-related, 355–356, 356f Occupational illness. See also specific illness defined, 269 Occupational injuries, defined, 269 Occupational Medicine Practice Guidelines, of American College of Occupational and Environmental Medicine, 299, 301 Occupational MSDs, defined, 269 Occupational Safety and Health Administration (OSHA), 3, 4, 211, 411 O’Connor Finger Dexterity Test, 233–234 O’Connor Tweezer Dexterity Test, 233, 234 Official Disability Guidelines, 411 O*NET, of U.S. Department of Labor, 234 Opioid(s) for hip pain, 301 for low back pain, 131 Oppenheim’s sign, 60
Index
Orthosis(es) ankle foot, 383, 386, 391, 392f cervical (Philadelphia collar), 82 foot, at workplace, 389 sports-related foot and ankle injuries due to, 336–337, 336f supramalleolar, UCBL, 390, 391f OSHA. See Occupational Safety and Health Administration (OSHA) Osteoarthritis hip, 270–271 imaging of, 296 treatment of, 299, 301f knee, 271 treatment of, 304–305, 305f, 306f lower extremity, 270–271, 270t heredity as factor in, 270 prevalence of, 270, 270t wrist and hand, 213, 244–246, 244f, 245f Osteochondral lesions, of talus diagnosis and treatment of, 368 workplace-related, 355, 355t Osteonecrosis, of hip, treatment of, 301, 302f Oswestry, 9 Overexertion theory, of musculoskeletal injury causality, 135 Overuse injuries, ankle-related, diagnosis and treatment of, 370–372
P Pain anterior knee, treatment of, 306 back. See Back pain foot and ankle, after foot and ankle injuries, 386 heel diagnosis and treatment of, 374–375 workplace adaptation of workers with, 390 low back. See Low back pain musculoskeletal, prevalence of, 397 neck, in workers, epidemiology of, 25–40. See also Neck pain, in workers, epidemiology of “patellofemoral,” treatment of, 306 rating of, AMA guides in, 413 wrist and hand, 232 “Painful arc,” 171 Passive range of motion (PROM), in neck injury evaluation in workers, 58 “Patellofemoral pain,” treatment of, 306 Patient Specific Functional Scale, 66 Patient-rated Wrist Evaluation Questionnaire, 228 Pectoralis reflex, 62, 65f Percentages of maximum voluntary contraction (%MVC), 198 Performance, defined, 398t Performance areas, defined, 398t Peroneal nerve common, entrapment of, 376 deep, entrapment of, 376 superficial, entrapment of, 376 Peroneal tendon injuries, diagnosis and treatment of, 371 Peroneus brevis tendon, tear of, workplacerelated, 354–355, 355f
Peroneus longus tendon, tear of, workplacerelated, 354–355, 355f Phalangeal fractures, workplace-related, 361–362 Phalanges, 341f, 342 fractures of, 244 Phalen’s test, 239 Phillips head screws, 251f, 252, 252t Physical capacity evaluation, in wrist and hand evaluation, 234 Physical job stresses, in analysis of job task demands, 202–204, 203f event-based vs. time-based observations, 203 measurement of posture and force, 202 prediction of posture and forces in, 203–204 psychophysical responses, 203, 203f surface EMG, 202–203 Physical Work Performance Evaluation, 402 Physician(s), role in disability evaluation, 409–416 Pistol-grip power drivers, 255–257, 256f, 257f, 257t Plain radiographs. See Radiography Plantar fascia rupture, diagnosis and treatment of, 374 Plantar fasciitis diagnosis and treatment of, 374 workplace adaptation of workers with, 390 Playing surfaces, sports-related foot and ankle injuries due to, 337 Plier(s), 252–253, 253f, 254t “Popeye” muscle, 172 Posterior atlantodens interval, 82 Posterior cord of brachial plexus, 59 Posterior talofibular ligament, function of, 367 Posterior tibial nerve, entrapment of, 376–377 Posttraumatic injury, wrist and hand, 224, 224f Posture measurement of, in analysis of job task demands, 202 prediction of, in analysis of job task demands, 203–204 Power hand tools, 249, 253–262 accessory handles and torque reaction arms, 258, 259f dynamic forces with, 260–262, 260f–262f handle force model, dynamics of, 261–262, 261f in-line power drivers, 256f, 257–258 pistol-grip power drivers, 255–257, 256f, 257f, 257t right-angle power drivers, 254f, 257, 258f static forces with, 254–258, 254f, 255t, 256f–258f, 257t tool counterbalancers, 259–260 tool torque buildup model, 260f, 2602–261 Practicality, of FPE, 405–406 Predictive validity, defined, 403t Prevalence, defined, 25 Prevalence rate, defined, 4 “Preventing Knee Injuries and Disorders in Carpet Layers,” 318 Prognostic study, in analytic epidemiology, 6–7, 6f PROM. See Passive range of motion (PROM) Pronator reflex, 64 Proximal humerus, fracture-dislocations of, 190
Proximal interphalangeal joint, osteoarthritis of, 245–246 Psychologic factors, musculoskeletal disorders and, 14–15 Psychophysical responses, in analysis of job task demands, 203, 203f Psychosocial factors in low back pain, 114–115 MSDs and, 14–15 relationship between, 15–16 work-related, 13–18 biopsychosocial model, 13–14, 14f described, 15–16 evidence for, 17–18, 17f Psychosocial interventions, for MSDs, 16–17, 17f Pulling, low back pain associated with, work adaptations for, 138, 139f Purdue Pegboard Test, 233, 234, 234f Pushing and pulling, low back pain associated with, work adaptations for, 138, 139f Putti-Platt procedure, for shoulder instability, 188
Q Q-angle, 279 Quebec Back Pain Disability Scale, 9 Quebec Task Force classification, 122 Quebec Task Force on Whiplash-Associated Disorders, 26 QuickTime, 201
R Radial tunnel syndrome, 152 Radiograph(s), in neck injury evaluation in workers, 66–67, 66f, 67f Radiography in elbow evaluation, 178–179, 179f in hip evaluation, 296, 299, 300f in knee evaluation, 296 in low back pain evaluation, 119–120 in shoulder evaluation, 172–174, 173f, 174f Radiohumeral joint, articulation of, 164 Radionuclide bone scan, in low back pain evaluation, 121 Radioulnar joint, articulation of, 164 Ranawat measurement, 82 Randomized control trials, in analytic epidemiology, 8–9, 8f Range of motion (ROM) abnormal, after foot and ankle injuries, 384–385, 385F ankle plantar flexion and dorsiflexion, 385 calcaneocavus, 385 equinus of ankle, 384–385 hallux limitus, 385, 385f ankle, 345–347, 346f hip, 290–291, 291f knee, 294, 294f in neck injury evaluation in workers, 55, 57–59, 58f wrist and hand, 228 Rate(s), defined, 3–4
425
Index
426
Ratio(s), defined, 3–4 Redlund-Johnell measurement, 82, 82f Reflex examination, in neck injury evaluation in workers, 60, 62, 63f–65f, 63t Reflex sympathetic dystrophy, 375 Relative risk, 9 Reliability, of FPE, 401–402 “Relocation” test, 171, 171f Repetition strain injury, 149 Repetitive hand transfer task, work elements, locations, and loads for, 198, 200t Repetitive motion disorders, 211, 212f Resistant tennis elbow, 152 Retinacular cysts, wrist and hand, 246 Retinacular ganglia, volar, 246 Return-to-work determinations, in disability evaluation, 411 Rheumatic diseases, lower extremity, 270 Rheumatism, lower extremity, 270 Rheumatoid arthritis, 79, 81–82, 82f hip, imaging of, 296 treatment of, 82 Right-angle power drivers, 254f, 257, 258f Risk factors, defined, 25 Rocker-sole footwear, 385, 385f Roland-Morris disability questionnaire, 9, 129 ROM. See Range of motion (ROM) Rotation, hip, 290–291, 291f Rotator cuff, evaluation of, 168f, 170 Rotator cuff disease anatomy and function in, 181–182 classification of injury in, 182 clinical presentation of, 182–185 differential diagnosis of, 182–183 evaluation of, 182–185 patient history in, 182 physical examination in, 182 treatment of, 181–185 goals in, 183 methods of, 183 nonoperative, 183 operative, 183–184 postoperative care, 184–185
S Safety, of FPE, 401 Safety shoes, at workplace, 387–388, 387f, 388f Saphenous nerve, entrapment of, 377 Scaphoid fracture, 243–244, 243f Scaphoid trapezium and trapezoid (STT) joint, 219 Scapholunate interval injury, 240–241, 240f Scapulohumeral reflex, 62 Screening, defined, 398t Screw(s) Phillips head, 251f, 252, 252t slotted, 251–252, 252f, 252t Torx head, 251f, 252, 252t Screw heads, 251–252, 251f, 252f, 252t Seated work, low back pain associated with, work adaptations for, 137 Self-care, for acute NSLBP, 126 Semms-Weinstein monofilament(s), 414 Semms-Weinstein monofilament testing, 231
Sensation, in wrist and hand evaluation, 230–232, 231f, 232f Sensory examination, in neck injury evaluation in workers, 59, 59f Sesamoid(s), problems related to, 380 Sesamoid fractures, workplace-related, 360–361, 361f Shoe(s) function of, 348, 348f military, at workplace, 388 modifications for, for workers with foot and ankle disorders, 383–384, 383t safety, at workplace, 387–388, 387f, 388f selection of, considerations in, 348–349 steel-shank, 385 at workplace, 387–388, 387f, 388f for female workers, 388 military shoes, 388 safety shoes, 387–388, 387f, 388f Shoe inserts, 349 Shoe inserts/insoles, for jobs requiring prolonged walking, 320 Shoe wear and orthoses, sports-related foot and ankle injuries due to, 336–337, 336f Shoulder(s) articulations of, 155–157, 156f, 157f biomechanics of, 155–162 anatomic considerations, 155–158, 156f, 157f, 157t bones of, 155, 156f degenerative joint disease of, 191 disorders of, 149–154. See also Shoulder disorders evaluation of, 167–176 CT in, 175 diagnostic testing in, 172–176, 173f–176f EMG in, 176 lidocaine injection tests in, 175, 176f MRI in, 174–175, 175f nerve conduction studies in, 176 patient history in, 167 physical examination in, 167–172, 168f–172f, 168t, 170t radiography in, 172–174, 173f, 174f technetium bone scanning in, 176 fractures and dislocations about, 189–190 frozen, 190–191 instability of, 185–189 described, 185 evaluation of, 171, 171f anesthesia in, 187–188 impingement syndrome, 185–187 treatment of, surgical procedures, 188–189 joint capsule of, 160 muscles of, 157–158, 157t Shoulder disorders, 149–154. See also specific types, e.g., Rotator cuff disease classification of, 149 entrapment and, 152 epidemiology of, 149–150 individual factors for, 151 muscular fatigue and, 152 occupational risk groups for, 149–150 pathomechanisms of, 151–152 prevention of, 152
Shoulder disorders—Cont’d ergonomics in, 162 risk factors for, 150–151 social factors for, 151 treatment of, 181–193. See also specific disorders, e.g., Rotator cuff disease, treatment of rotator cuff disease, 181–185 shoulder instability, 185–189. See also Shoulder(s), instability of workplace adaptation for, 195–208 anthropometric considerations, 204–206, 205f, 206f arm rests, 207 body supports, 207 evaluation of, 207 exposure-response relationship, 195–200. See also Exposure-response relationship forearm rests, 207 job task demands, analysis of, 200–204, 202t. See also Job task demands mechanical assists, 206–207 placement of work objects, 197t, 198t, 202t, 204 tool weight control, 206 worker fitness and weight, 207 work-related factors for, 150–151 Shoulder joint, static stabilizers of, 158–160, 160f Shoulder stressors, identification and control of, sample documentation and analysis of “claims processor” job in, 88t Sinus tarsi syndrome, diagnosis and treatment of, 369 Skier’s thumb, 242, 242f Skin disorders, foot-related, 380–381 SLBP. See Specific low back pain (SLBP) Slotted screws, 251–252, 252f, 252t Soccer toe, 381 Social Security, 409 Soft disk herniations, types of, 75, 76f Somatosensory evoked potentials (SSEPs), in neck injury evaluation in workers, 71 Spatial motion, 158, 159f Specific low back pain (SLBP), 125 Speed’s test, 172, 182 Spine cervical. See Cervical spine clinical biomechanics of, 107–112 FSU, 107–110, 108f, 109f, 109t. See also Functional spinal unit (FSU) kinematics, 110, 110f, 111f kinetics, 110–112, 111f, 112f disorders of back pain related to, 100–101 rating of, AMA guides in, 413–414 imaging studies of, in neck injury evaluation in workers, 66–69, 66f–71f MSDs of, 22–144 thoracic, biomechanics of, 41–54 Spondylosis, 77–78 with myelopathy, 78–79, 80f, 81f treatment of, 79 treatment of, 78
Index
Sports, foot and ankle injuries related to causes of, 333–337, 334t, 335f, 336f anatomic/biomechanical abnormalities, 334–335, 335f lack of flexibility, 335 lack of stability, 335 lack of strength, 335 playing surfaces, 337 shoe wear and orthoses, 336–337, 336f epidemiology of, 333, 334t prevalence of, 333, 334t prevention of, 337 Sprain(s) ankle diagnosis and treatment of, 367–368 workplace adaptation of workers with, 389 foot, workplace-related, 362–364, 362f–364f hip, treatment of, 301 knee, treatment of, 303–304, 303f, 304f midtarsal, 377–378 of MTP joint, treatment of, 378 neck. See Neck sprain wrist and hand, 240–242, 240f–242f Spur(s), heel, diagnosis and treatment of, 374 Spurling’s sign, 64, 65f Spurling’s test, in neck injury evaluation in workers, 59 Squatting, during ADLs, joint forces and, 281–283, 283f SSEPs. See Somatosensory evoked potentials (SSEPs) Stability, lack of, sports-related foot and ankle injuries due to, 335 Stability testing, of elbow, 178 Stair climbing, during ADLs, joint forces and, 283–284 Standard error (SE), 9 Standing, prolonged antifatigue mats for jobs requiring, 319–320 physiology/biomechanics of, 315 Static forces, with power hand tools, 254–258, 254f, 255t, 256f–258f, 257t Static work, 136–137 Statistical analysis, 9–11, 10f, 11t estimates and confidence limits in, 9–10 methods of, 9, 10f statistical hypothesis testing in, 10 statistical power and sample size in, 10–11, 11t Statistical hypothesis testing, 10 Statistical power and sample size, 10–11, 11t Stature(s), for males and females ages 18 and over, 197, 198t Steel-shank footwear, 385 Stener lesion, 242 Sternoclavicular joint articulation of, 155 fracture-dislocations of, 189 Stiffness, elbow-related, 176 “Straight leg raise,” 290 Strain(s), hip, treatment of, 301 Strength lack of, sports-related foot and ankle injuries due to, 335 wrist and hand, 220
Stress fractures, of foot and ankle, diagnosis and treatment of, 373–374 Stressor(s) job-related, physical, in analysis of job task demands, 202–204, 203f. See also Physical job stresses, in analysis of job task demands neck and shoulder, identification and control of, sample documentation and analysis of “claims processor” job in, 88t “Stretcher adapter,” in carpet installation, 318–319 Subtalar joint, 342 Subtalar joint dislocations, diagnosis and treatment of, 372 Subtalar joint injuries, diagnosis and treatment of, 372 Subungual exostosis, 381 Subungual hematomas, 381 Superficial peroneal nerve, entrapment of, 376 Supervisor(s), interviews with, 202 Supramalleolar orthosis, UCBL, 390, 391f Sural nerve, entrapment of, 377 Survival curve, 9, 10f
T Talocalcaneal joint, 342 Talus, 341, 341f fractures of diagnosis and treatment of, 372 workplace-related, 359–360, 359f osteochondral lesions of diagnosis and treatment of, 368 workplace-related, 355, 355t TARGA-16–based video-digitization system, 316 Tarsal bones, of midfoot fractures, workplacerelated, 360 Tarsal navicular stress fracture, 374 Tarsometatarsal (TMT) joint, 342 Tarsometatarsal (TMT) joint injuries diagnosis and treatment of, 378 workplace-related, 362–363, 362f, 363f Technetium bone scanning in elbow evaluation, 180 in shoulder evaluation, 176 Tendinitis, 237–238, 237f, 238f ankle-related, diagnosis and treatment of, 370–372 knee-related, treatment of, 305–306 lower extremity–related, 269 Tendinopathy, 238, 370 about elbow, 177 Tendon excursion, wrist and hand, 220–221, 222f Tennis elbow, 149 resistant, 152 “Tennis toe,” 381 Testing, defined, 398t TFCC. See Triangular fibrocartilage complex (TFCC) The Medical Disability Advisor, 411 Thomas test, 290, 291f Thoracic outlet syndrome, tests for, 65 Thoracic spine, biomechanics of, 41–54 Thumb(s) gamekeeper’s, 242, 242f skier’s, 242, 242f
Thumb basilar joint, osteoarthritis of, 245–245f Tibial pilon fractures, workplace–related, 352 Tibialis posterior tendon insufficiency, workplace adaptation of workers with, 390, 391f Tibialis posterior tendon overuse problems, diagnosis and treatment of, 371–372 Time-based observations, event-based observations vs., in analysis of job task demands, 203 Tinea pedis, 381 Tinel’s sign, 364, 375 Tinel’s test, 239 TMT joint injuries. See Tarsometatarsal (TMT) joint injuries Toe(s) hammer, 379–380 soccer, 381 “tennis,” 381 Toe blisters, safety footwear and, case study, 388, 388f Toe fractures, workplace-related, 361–362 Toenail(s) fungal infections of, 382 ingrown, 381 problems related to, 381–382 Tool counterbalancers, 259–260 Tool torque buildup model, 260–261, 260f Tool weight control, in workplace adaptation for shoulder disorders, 206 Torque reaction arms, 258, 259f Torx head screws, 251f, 252, 252t Total contact cast, 391, 391f Total hip replacement, indications for, 299, 301 Touch-Test Sensory Evaluators, 231, 231f Touch-Test Two-Point Diskcriminator, 231, 231f Training, described, 89 Transversal tarsal joint, 342 Trendelenburg sign, 375 Trendelenburg test, 290, 290f Triangular fibrocartilage complex (TFCC), 240f, 241, 241f Trigger finger, 237–238, 238f Trochanteric bursitis, treatment of, 301 2000–2010 Bone and Joint Decade Task Force on Neck Pain and Its Associated Disorders, 25, 26
U UCBL. See University of California Biomechanical Laboratory (UCBL) UCBL supramalleolar orthosis, 390, 391f Ulceration(s), neuropathic, on plantar surface of foot in diabetics, 391, 391f Ulnar artery, superficial palmar branch of, occlusion of, 213 Ulnar tunnel syndrome, 239 Ulnohumeral joint, articulation of, 163–164, 163f Ultrasonography, in low back pain evaluation, 121–122 University of California Biomechanical Laboratory (UCBL) supramalleolar orthosis, 390, 391f
427
Index
428
University of Michigan Three-Dimensional Static Strength Prediction Program, 204 Unna’s paste boot bandage, 386, 387f Upper Body Musculoskeletal Assessment, 228 Upper extremities, 145–263. See also Shoulder(s); specific sites, e.g., Hand(s) impairments of, rating of, AMA guides in, 414 U.S. Bureau of Labor Statistics, 3, 4 U.S. Department of Labor DOT of, 399, 400t O*NET of, 234 U.S. Dictionary of Occupational Titles, Worker Qualification Profiles of, 234 U.S. Marine Corps, 332 U.S. National Health survey, 88 U.S. Social Security Disability Insurance System, 103 U.S. Supreme Court, 56 Utility, of FPE, 406
V Validity defined, 403t of FPE, 402–405, 403t in aerobic capacity testing, 404–405 legal constraints challenging, 400 sincerity of effort in, 402–403 in work-related activities evaluation, 403–404 types of, 403t Valleix phenomenon, 375–376 Valpar Corporation Work Samples (VCWS), 234 Valsalva maneuver, 64 Variance, 10 Varus stability, of elbow, 178 Vascular problems, of lower extremity, workplace-related, 314–315 VCWS. See Valpar Corporation Work Samples (VCWS) Venous disorders, foot and ankle–related, workplace adaptation of workers with, 392–393 Verrucae vulgares, 381 Veterans Affairs Health Care System, exercise laboratories of, 401 Vibration white finger disease, 213, 239-240 Video recordings, job-related, 201–202 Video-digitization system, TARGA-16–based, 316 Visual Analog Scale, 227, 232 Volar retinacular ganglia, 246
W Walking during ADLs, joint forces and, 283–284 prolonged, jobs requiring, shoe inserts/insoles for, 320 in workplace, 384 Wart(s), of foot, 381 Weight, as factor in internal joint forces for hip and knee, 277–279, 278f Weinstein Enhanced Sensory Test (WEST), 231 Whiplash injury, 82–83 Wilcoxon method, 9 Women, at workplace, footwear for, 388 Work ability, in disability evaluation, 411–412
Work activities, biomechanical demands on foot and ankle during, 384 Work equipment, measurements of, as job task, 202 Work methods, 88 Work objects, placement of, 197t, 198t, 202t, 204 Work populations, accommodation for, process of, 195, 195f “Work sampling,” 201 Work standards, 88 Work stations designing of, placement of work objects, 197t, 198t, 202t, 204 measurements of, as job task, 202 suppliers for, websites of, 144 Worker(s) accommodation for, process of, 195, 195f activities of, observations of, 200–201 interviews with, 202 MSDs in. See also under specific disorders and Musculoskeletal disorders (MSDs) neck pain in, epidemiology of, review of, 25–40. See also Neck pain, in workers, epidemiology of Worker capacity, 198–200, 199t, 200f, 200t, 201f Worker fitness and weight, in workplace adaptation for shoulder disorders, 207 Worker Qualification Profiles, of U.S. Dictionary of Occupational Titles, 234 Workers’ Compensation Board, 135 Workload, as factor in elbow and shoulder disorders, 151–152 Workplace activities in, biomechanical demands on foot and ankle during, 384 footwear at, 387–388, 387f, 388f. See also Shoe(s) lower extremity disorders in, 309–327. See also Lower extremity disorders, workplace-related Workplace adaptation. See also Work stations for foot and ankle disorders, 383–393. See also Foot and ankle disorders, workplace adaptation of workers with for low back pain, 135–144. See also Low back pain, workplace adaptation for to MSDs, neck-related disorders, 87–93 evaluation of, 87, 88t, 89–90, 89t, 90f–92f, 92 specification of, 87–89 for shoulder disorders, 195–208. See also Shoulder disorders, workplace adaptation for Workplace injuries, foot and ankle, 351–366. See also Foot and ankle disorders, workplace-related Workplace layout, 88 Work-related activities evaluation of, FPE validity in, 403–404 FPE of, reliability of, 401–402 Work-related performance tests, 399 World Health Organization, 97 Wrist. See also Wrist and hand carpal joint of, force through, 223–224, 223f ganglia of, 246, 246f osteoarthritis of, 244–245, 244f
Wrist and hand, 209–263 biomechanics of, 219–225 force through wrist carpal joint, 223–224, 223f motion, 219–220 muscle and joint forces, 221–223, 223f posttraumatic injury, 224, 224f skeletal and ligamentous anatomy/joint constraint, 219, 220f, 221f strength, 220 tendon excursion, 220–221, 222f clinical evaluation of, 228–232 edema, 228–229, 229f muscle performance testing, 229–230, 230f pain, 232 range of motion, 228 sensation, 230–232, 231f, 232f evaluation of, 227–235. See also specific types, e.g., Wrist and hand, clinical evaluation of clinical assessment, 228–232 functional assessment, 232–234 multidimensional assessment, 227–228 functional evaluation of, 232–234 ADLs, 233 dexterity, 233–234, 233f, 234f information processing, 232–233 physical capacity evaluation, 234 Wrist and hand disorders. See also specific disorders, e.g., de Quervain disease costs of, 213 disability burden associated with, 212–213 early history of, 211 epidemiology of, 211–218, 211f, 212f, 214t, 215t frequency of, 211–213, 212f incidence of, 211–213, 212f hand-arm vibration syndrome, 213 hypothenar hammer syndrome, 213 individual factors in, 212f, 213–214 occlusion of superficial palmar branch of ulnar artery, 213 osteoarthritis of, 213 treatment of, 237–248 CRPS, 247 CTS, 238–239 de Quervain disease, 237, 237f fingers, 242 fractures, 242–244, 243f gamekeeper’s thumb, 242, 242f ganglia, 246–247, 246f hand-arm vibration syndrome, 239–240 lunotriquetral interval injury, 241 osteoarthritis, 244–246, 244f, 245f scapholunate interval injury, 240–241, 240f sprains, 240–242, 240f–242f tendinitis, 237–238, 237f, 238f tendinopathies, 238 TFCC, 240f, 241, 241f trigger finger, 237–238, 238f ulnar tunnel syndrome, 239 types of, 213 vibration white finger disease, 213 work-related factors in, 212f, 214–216, 214t, 215t
Y Yergason’s test, 172
