Carpal Tunnel Syndrome - Guide to the Diagnosis of Work-Related Musculoskeletal Disorders Vol 1

Work-related musculoskeletal injuries are one of the most common occupational health problems for which physicians are consulted. There is solid scientific evidence that these injuries may be occupational in origin.

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GUIDE TO THE DIAGNOSIS OF WORK-RELATED MUSCULOSKELETAL DISORDERS

This guide was designed to help physicians interpret the results of a medical examination. By combining the standard clinical assessment procedure with guidelines concerning the identification of etiological factors, it helps physicians identify the cause of injury.

AUTHORS Louis Patry holds a degree in medicine from Laval University and a diploma in ergonomics from the Conservatoire National des Arts et Metiers de Paris (CNAM). He is a specialist in occupational medicine, an associate member of the Royal College of Physicians and Surgeons of Canada, a professor in McGill University’s Department of Epidemiology and Biostatistics and Occupational Health, and consulting physician to the Direction de la santé publique (Public Health Department), first in Québec City and currently at the MontréalCentre board.

Michel Rossignol holds degrees in biochemistry and medicine from the University of Sherbrooke, in epidemiology and community health from McGill University, and in occupational medicine from John Hopkins University. He is a professor in McGill University’s Department of Epidemiology and Biostatistics and Occupational Health, co-director of the Centre for Clinical Epidemiology of the Jewish General Hospital of Montréal, and physician-epidemiologist at the Montréal-Centre board of the Direction de la santé publique (Public Health Department).

Marie-Jeanne Costa holds a nursing degree from the Institut d’études paramédicales de Liège and a degree in ergonomics from the École Pratique des Hautes Études de Paris. She is an ergonomics consultant and has collaborated on several studies of CTDs. She is particularly interested in the development of participatory ergonomics, specifically in the problem-resolution and diagnostic processes.

Martine Baillargeon holds a degree in medicine from the Université de Montréal. She is a plastic surgeon and associate member of the Royal College of Physicians and Surgeons of Canada. After years of practising surgery she is now consulting physician, mainly in the field of musculoskeletal injuries affecting the upper limb, at the Montréal-Centre board of the Direction de la santé publique (Public Health Board).

Carpal Tunnel Syndrome Louis PATRY, Occupational Medecine Physician, Ergonomist Michel ROSSIGNOL, Occupational Medecine Physician, Epidemiologist Marie-Jeanne COSTA, Nurse, Ergonomist Martine BAILLARGEON, Plastic Surgeon

GUIDE TO THE DIAGNOSIS OF WORK-RELATED MUSCULOSKELETAL DISORDERS

Carpal Tunnel Syndrome Louis PATRY, Occupational Medecine Physician, Ergonomist Michel ROSSIGNOL, Occupational Medecine Physician, Epidemiologist Marie-Jeanne COSTA, Nurse, Ergonomist Martine BAILLARGEON, Plastic Surgeon

Canadian Cataloguing in Publication Data Main entry under title: Guide to the diagnosis of work-related musculoskeletal injuries Translation of: Guide pour le diagnostic des lésions musculo-squelettiques attribuables au travail répétitif. Includes bibliographical references. Contents: 1. Carpal tunnel syndrome – 2. De Quervain’s tenosynovitis – 3. Shoulder tendinitis. Co-published by: Institut de recherche en santé et en sécurité du travail du Québec. ISBN 2-921146-70-3 (v. 1) – ISBN 2-921146-71-1 (v. 2) – ISBN 2-921146-72-X (v. 3) 1. Musculoskeletal system – Wounds and injuries – Diagnosis. 2. Overuse injuries – Diagnosis. 3. Carpal tunnel syndrome – Diagnosis. 4. Tenosynovitis – Diagnosis. 5. Tendinitis – Diagnosis. 6. Occupational diseases – Diagnosis. I. Patry, Louis. II. IRSST (Quebec). III. Workplace Safety & Insurance Board. RC925.7.G8413 1998 616.7’075 C98-940950-3

Translation:

Les Services Organon, Steven Sacks

Graphic design:

Gérard Beaudry

Illustrations:

Marjolaine Rondeau, Medical Illustration Department of the Laval University Hospital Centre (CHUL) Max Stiebel, Instructional Communications Centre (ICC), McGill University

Rear-cover photographs: Gil Jacques Legal deposit – Bibliothèque nationale du Québec, 1998 Legal deposit – National Library of Canada, 1998 ISBN 2-921146-70-3 Éditions MultiMondes (Original edition: ISBN 2-921146-37-1) © Éditions MultiMondes, 1998 Éditions MultiMondes 930, rue Pouliot Sainte-Foy (Québec) Canada G1V 3N9 Tel.: (418) 651-3885 Fax: (418) 651-6822

Institut de recherche en santé et en sécurité du travail 505, boul. de Maisonneuve Ouest Montréal (Québec) Canada H3A 3C2 Tel.: (514) 288-1551 Fax: (514) 288-7636

Régie régionale de la santé et des services sociaux – Montréal-Centre Direction de la santé publique 1301, rue Sherbrooke Est Montréal (Québec) Canada H2L 1M3 Tel.: (514) 528-2400 Fax: (514) 528-2459

PREFACE

The diagnosis of cumulative trauma disorders (CTDs) presents many unique problems, especially for physicians. The absence of precise criteria upon which to establish a clinical diagnosis of CTD or decide whether a musculoskeletal injury is related to occupational factors was noted by several members of the advisory committee supporting an international expert group mandated by the IRSST to review the literature on CTDs*. To remedy this situation, in 1992 the IRSST asked a group of researchers to develop diagnostic guides for carpal tunnel syndrome, De Quervain’s tenosynovitis, and tendinitis of the shoulder. The project team was initially composed of Louis Patry, occupational medecine physician and ergonomist, and Michel Rossignol, occupational medecine physician and epidemiologist, but quickly grew and increased the scope of its expertise through the addition of Marie-Jeanne Costa, a nurse with ergonomics training, and Martine Baillargeon, a plastic surgeon. All four team members participated in the drafting of the guides. These guides were designed to help physicians arrive at a clinical diagnosis and identify the most probable etiological agents. It should be noted that these guides were not designed for administrative or legal purposes and that their reliability has not been evaluated by the researchers. The publication of these guides designed specifically for physicians is one more advance in the IRSST’s efforts to shed light on the phenomenon of cumulative trauma disorders and provide specialists with appropriate tools with which to prevent these injuries and reduce related risk factors.

Jean Yves Savoie Director General Institut de recherche en santé et en sécurité du travail du Québec

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* Hagberg, M., Silverstein, B., Wells, R., Smith, M.J., Hendrick, H.W., Carayon, P., Pérusse, M. (1995), Work related musculoskeletal disorders (WMSDs): a reference book for prevention, scientific editors: Kuorinka, I., Forcier, L., publishers Taylor and Francis, London, 421 pages.

INTRODUCTION

This guide is the first of a series of practical summaries of current medical knowledge on musculoskeletal injuries with well-documented occupational etiology, namely: – carpal tunnel syndrome (CTS) – De Quervain’s tenosynovitis – tendinitis of the shoulder When occupational in origin, these injuries are often referred to as “CTDs”, a term applicable to “problems and diseases of the musculoskeletal system that include, among their causes, some factor related to work” (Hagberg et al., 1995). Whatever term is used to designate them—occupational overuse syndrome (OOS), repetitive strain injuries (RSI) or cumulative trauma disorders (CTDs) in English, troubles musculo-squelettiques (TMS), lésions musculo-squelettiques (LMS), lésions musculo-tendineuses (LMS), lésions musculo-tendineuses liées aux tâches répétitives, or pathologies d’hyper-sollicitation in French—their defining characteristic is the presence of an injury caused by biomechanical strain due to tension, pressure, or friction which is excessively forceful, repetitive, or prolonged. This guide is designed for physicians who are called upon in the course of their practice to diagnose musculoskeletal injuries and establish the extent to which these injuries are caused by their patient’s work. Its goal is to help physicians arrive at clinical and etiological diagnoses. To this end, the guide first reviews the anatomical, physiopathological, and etiological knowledge upon which diagnosis depends. This is followed by guidelines for the evaluation of symptoms, the conduct of the clinical examination, and the control of potential risk factors related to the development of the injury. Musculoskeletal injuries may have many causes. For carpal tunnel syndrome (CTS), De Quervain’s tenosynovitis, and tendinitis of the shoulder, these include not only occupational, sports-related, recreational, and household activities, but also specific health problems and conditions. This guide was prepared in response to requests from physicians, increasingly preoccupied by CTDs, for information and support on this subject. Although the approach taken emphasizes the documentation of potential occupational risk factors—a subject little discussed in formal medical training—it does not neglect the evaluation of other potential causes of carpal tunnel syndrome. This guide is meant to be used in a clinical setting. To help physicians collect the information they need to diagnosis the injury and establish its causes, it therefore includes a series of questions, presented in readily identifiable text boxes, for them to ask their patients. These questions were derived from psycho-physical scales used by ergonomists to subjectively evaluate workload (Sinclair, 1992) and medical questionnaires developed for the diagnosis of CTS and the evaluation of functional capacity (Katz et al., 1994; Levine et al., 1993; Rossignol et al., 1995).

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Should however a physician remain unable to come to a definitive conclusion about the work-relatedness of an injury after consulting this guide, she or he should continue to seek information which will enable her or him to better evaluate the occupational musculoskeletal load to which her or his patient is subjected. Finally, it should be noted that this guide does not address the issues of multiple injuries and the psychosocial aspects of musculoskeletal injuries, important as they may be for the global evaluation of the patient.

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TABLE OF CONTENTS

Chapter 1 – General Considerations Terminology................................................................................................................... 1 Epidemiology................................................................................................................. 1 Anatomical Review........................................................................................................ 1 Pathophysiology ............................................................................................................ 3 Chapter 2 – Etiology Pathologies that Modify the Shape of the Carpal Tunnel or Increase the Volume of its Contents........................................................................ 5 Systemic Pathologies and Specific Conditions ........................................................... 5 Work-Relatedness of Musculoskeletal Strain................................................................ 5 Compression of the Median Nerve in the Carpal Tunnel .................................... 5 Compression of the Thenar Branch of the Median Nerve................................... 7 Chapter 3 – Differential Diagnosis Disorders of the Central Nervous System .................................................................... 9 Disorders of the Peripheral Nervous System............................................................... 9 Chapter 4 – Clinical Considerations Symptoms..................................................................................................................... 11 Location of Symptoms (Where?).......................................................................... 12 Onset of Symptoms (When?) ............................................................................... 12 Characteristics of Onset (How?)........................................................................... 13 Impact on Activities of Daily Living........................................................................... 14 Chapter 5 – Recording of Information on Exposure Factors Occupational History .................................................................................................. 15 Previous Work....................................................................................................... 15 Current Work......................................................................................................... 16 Current Work and Organisational Factors ........................................................... 16 Sports-related, Recreational, and Household Activities............................................. 18 Chapter 6 – Clinical Examination Observation and Palpation ......................................................................................... 19 Provocative Tests......................................................................................................... 20 Evaluation of Sensitivity .............................................................................................. 21

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Strength Testing ........................................................................................................... 22 Electrophysiologic Tests.............................................................................................. 23 Chapter 7 – Summary of the Evaluation ..................................................................... 25 Chapter 8 – Guidelines for Therapeutic and Preventive Interventions Therapeutic Guidelines ............................................................................................... 27 Prevention Guidelines................................................................................................. 28 Conclusion........................................................................................................................ 29 Bibliography .................................................................................................................... 31

List of Figures Figure 1.1

Anatomy of the Carpal Tunnel ..................................................................... 2

Figure 1.2

Sensory Nerve Field....................................................................................... 2

Figure 1.3

Distal Branches of the Median Nerve (Sensory and Motor) ....................... 2

Figure 2.1

Compression of the Thenar Branch.............................................................. 7

Figure 3.1

Sites of Compression of the Median Nerve.................................................. 9

Figure 4.1

Hand and Upper Limb Diagram ................................................................. 12

Figure 6.1

Bony Limits of the Carpal Tunnel............................................................... 19

Figure 6.2

Phalen’s Test................................................................................................. 20

Figure 6.3

Tinel’s Test ................................................................................................... 20

Figure 6.4

Two-point Discrimination Test.................................................................... 21

Figure 6.5

Semmes-Weinstein Test ............................................................................... 21

Figure 6.6

Abductor Pollicis Brevis............................................................................... 22

Figure 6.7

Opponens Pollicis........................................................................................ 22

Figure 8.1

Therapeutic Intervention Flow-chart .......................................................... 27

List of Tables Table 6.1

Clinical Provocation Tests............................................................................ 20

Table 6.2

Tests of Sensory Function ........................................................................... 21

Table 6.3

Electrophysiologic Tests .............................................................................. 23

Table 8.1

Preventive Approach ................................................................................... 28

List of Boxes x

Box 1.1

The Three Stages in the Evolution of the Progressive Form of Carpal Tunnel Syndrome .......................................................................... 3

Box 2.1

High-risk Activities, Movements, and Actions.............................................. 6

Box 4.1

Symptoms Reported by the Patient ............................................................ 11

Box 4.2

Presentation and Clinical Severity of Symptoms........................................ 13

Box 4.3

Questions about Activities of Daily Living ................................................. 14

Box 5.1

Questions about Previous Work ................................................................. 15

Box 5.2

General Questions about Occupational Activities and Associated Symptoms........................................................................... 16

Box 5.3

Questions about Activities that Cause Pain in the Hands or Wrist........... 17

Box 5.4

Questions about Organizational Factors at Work ...................................... 18

Box 5.5

Questions about Sports-related, Recreational, and Household Activities Involving the Hands or Wrist ...................................................... 18

Box 6.1

Appearance of the Arms, and State of the Wrist and Hand Tissues......... 19

Box 7.1

Clinical Aspects ............................................................................................ 25

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1

General Considerations

TERMINOLOGY The signs and symptoms of sensory and motor disorders of the hand in the median nerve field were first reported by Paget in 1854 in a patient having suffered a fracture of the wrist. The following terms were initially used to describe the observed problems: tardive paralysis of the median nerve, partial atrophy of the thenar eminence, and median neuritis. However, it was not until the work of Brain et al. in 1947 and of Phalen et al. in 1950 that the term carpal tunnel syndrome (CTS) was applied to these disorders. EPIDEMIOLOGY In Québec, the surgery rate in the general population for carpal tunnel syndrome is approximately 0.5 per 1 000 men and 1.1 per 1 000 women. The highest rate—2.2 per 1 000—is observed among women aged 50 to 59 years. These rates are comparable to those reported by Vessey et al. (1990) for England (0.5-1.3) and Liss et al. (1992) for Ontario (0.5-3.5). The mean age of onset is 51 years in the general population, but only 37.4 years among individuals requesting workers’ compensation (Franklin et al., 1991). In 56.8% of cases, concomitant diseases or conditions are present (Stevens et al., 1992); the most common are hormonal disorders (6.1%), diabetes (6.1%), pregnancy (4.6%) and thyroid disorders (1.4%). Franklin et al. (1991) reported a CTS incidence rate of 1.74 per 1 000 compensated workers in the state of Washington. The risk factors most commonly observed were repetitive wrist and forearm move-

ments, holding the wrist at an angle (Armstrong et al., 1979), performing forceful movements (Silverstein et al., 1987), and exposure to segmental vibration and cold. Rossignol et al.’s study (1990) of the occupational variation of the incidence of CTS on the island of Montreal reported that almost half of the cases (45%) of CTS occurring among manual workers are work-related. In seven occupational categories, this proportion ranged from 63% to 91%. ANATOMICAL REVIEW Anatomy of the Carpal Tunnel The carpal tunnel (Figure 1.1) is bounded posteriorly and medially by the carpal bones and anteriorly by the transverse carpal ligament. The median nerve and nine flexor tendons (four flexor digitorum superficialis, four flexor digitorum profundus tendons, and the flexor pollicis longus tendon) run through the tunnel. The pressure inside the tunnel varies as a function of the position of the wrist: it is 2.5 mm Hg when the wrist is in the neutral position, but rises to 30 mm Hg when it is completely flexed and 32 mm Hg when it is completely extended (Gelberman et al., 1981).

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Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

Figure 1.1

Figure 1.2

Anatomy of the Carpal Tunnel

Sensory Nerve Field

Median nerve Tendon of the flexor carpi radialis

Transverse carpal ligament of the wrist Ulnar nerve Tendons of the flexor digitorum muscles

Sensory Innervation The median nerve usually arises principally from the C6, C7, C8, and T1 nerve roots. Its sensory fibres innervate the palmar aspect of the thumb, index finger, middle finger and radial half of the ring finger, and the dorsal aspect of the tip of these fingers (Figure 1.2). The pad of the index and middle fingers constitutes its selective sensory nerve field. The palmar cutaneous branch of the median nerve innervates part of the palm and the thenar eminence of the hand; its innervation field is indicated by the shaded area in Figure 1.2. As it separates from the main body of the nerve 5-7 cm proximal to the anterior annular ligament of the wrist, it is not compressed in cases of carpal tunnel syndrome, and sensory function in the palm is usually preserved in cases of CTS (Tubiana, 1990; Dawson et al., 1990).

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The autonomic nerve fibres of the median nerve control perspiration (Spinner, 1989) and innervate the superficial palmar arch and the digital vessels of the thumb, index finger, middle finger, and the radial half of the ring finger.

Motor Innervation The motor branches of the median nerve innervate three muscles in the thenar eminence (the abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis) and the lumbricals of the index and middle finger (Figure 1.3). Because variant innervation patterns are common, the most reliable indicator of motor disorders of the median nerve is weakness of the abductor pollicis brevis (Dawson et al., 1990). Figure 1.3

Distal Branches of the Median Nerve (Sensory and Motor)

Lumbricals

Thenar muscles

Transverse carpal ligament of the wrist

PATHOPHYSIOLOGY Carpal tunnel syndrome is the symptomatic presentation of median nerve entrapment at the wrist. This syndrome may result from transient ischemic episodes linked to microvascular disorders, or from median nerve compression as a result of a reduction in tunnel volume or an increase in the volume of tunnel contents (Moore, 1992). In cases of CTS, the intra-tunnel pressure increases to 32 mm Hg with the wrist in the neutral position, 94 mm Hg with it flexed, and 110 mm Hg with it extended (Gelberman et al., 1981). It should be noted in this context that pressures exceeding 30 mm Hg have been reported to reduce epineural blood flow and elicit certain early signs and symptoms of nerve

compression in human volunteers and laboratory animals (Gelberman, 1988). The signs and symptoms of carpal tunnel syndrome appear suddenly or progressively in the median nerve’s innervation field in the hand; less frequently, proximally referred wrist pain may be the first symptom (Moore, 1992; Szabo and Madison, 1992). The acute form is relatively rare, with the sudden appearance of intense symptoms usually resulting from trauma or intense and unusual exertion involving the wrist (Marras, 1992; Szabo and Madison, 1992). Most commonly, median nerve disorder is progressive (Moore, 1992).

Box 1.1

The Three Stages in the Evolution of the Progressive Form of Carpal Tunnel Syndrome – In stage 1, transient epineural ischemic episodes cause intermittent pain and paresthesia in the median nerve’s field in the hand. These symptoms typically occur at night or following specific activities such as driving a car or holding a book or newspaper, and indicate the presence of nerve transmission disorders. Symptoms disappear once circulation is reestablished or decompression accomplished through movements such as shaking the wrist (Flick test). – In stage 2, there is constant paresthesia and tingling, corresponding to disturbed intraneural and epineural microcirculation concomitant with intrafascicular edema. Electrodiagnostic tests usually reveal abnormal sensory conduction (Novak et al., 1992; Dawson et al., 1990). – In stage 3, sensory and motor function are permanently damaged, and there is atrophy of the thenar eminence. Electrodiagnostic tests are abnormal, and demyelinisation and axonal degeneration secondary to prolonged endoneural edema may be present. Source: Szabo et Madison, 1992

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CARPAL TUNNEL SYNDROME

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Etiology

The clinical signs and symptoms related to median nerve disorders of the wrist or hand have been attributed to a variety of factors and conditions. This chapter will focus on etiological factors that directly affect the median nerve in the carpal tunnel. Compression of the median nerve at the wrist may be caused by: – pathologies that modify the shape of the carpal tunnel or increase the volume of its contents – systemic pathologies or conditions that increase intra-tunnel pressure – work-related musculoskeletal strain PATHOLOGIES THAT MODIFY THE SHAPE OF THE CARPAL TUNNEL OR INCREASE THE VOLUME OF ITS CONTENTS The volume of the carpal tunnel may be reduced by abnormalities or fractures of the wrist bones, thickening of the anterior ligament, necrosis of the semilunar bone, and hand traumas or contusions. Tumours (lipomas, hemangiomas, lipofibromas, liposarcomas), synovial cysts, and tenosynovitis (rheumatoid, infectious or tubercular, or secondary to amyloidosis or gout) may increase the volume of structures within the tunnel.

pressure of extravascular fluid within the carpal tunnel and cause compression of the median nerve. WORK-RELATEDNESS OF MUSCULOSKELETAL STRAIN Compression of the median nerve at the wrist may result from repetitive wrist movements or the prolonged maintenance of awkward wrist positions. Compression occurs at the level of the median nerve within the carpal tunnel or of the thenar branch in the hand. Compression of the Median Nerve in the Carpal Tunnel Aside from accidents, compression of the median nerve in the carpal tunnel appears to be linked to biomechanical stress resulting from tension, pressure or friction of sufficient frequency, force and duration. Increased musculoskeletal load in the upper limbs—e.g. from prolonged maintenance of the cervico-scapular region in a fixed posture or prolonged flexion or abduction of the arms—may disrupt distal circulation and contribute to the development of CTS. The movements and postures most commonly associated with the development of CTS are listed in Box 1.2.

SYSTEMIC PATHOLOGIES AND SPECIFIC CONDITIONS Specific systemic pathologies (e.g. hypothyroidism) and conditions (e.g. pregnancy) may increase the

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Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

Box 2.1

High-risk Activities, Movements, and Actions Repetitive movements of the wrist or hand

Activities with the wrist extended or flexed

Repeated or continuous radial or ulnar deviation

Repeated movements involving one or more fingers

Grasping and handling movements

Repeated grasping of objects in a finger pinch

Repeated grasping of objects involving one or more fingers

Grasping with a full grip

Scissors movements

Application of pressure with the hand

Use of vibrating or percussion tools

Risk cofactors

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Awkward flexion or abduction of the arm Wearing gloves Exposure to cold Source: Rossignol et al., 1996; Hagberg, 1992; Silverstein, 1987

Compression of the Thenar Branch of the Median Nerve The thenar branch of the median nerve is essentially a motor branch. Repeated or prolonged application of force with the palm of the hand may result in atrophy of the thenar eminence with no paresthesia. It is quite rare for the thenar branch to be the only one affected: thenar atrophy is more commonly related to motor disturbances of the median nerve in the carpal tunnel.

Figure 2.1

Compression of the Thenar Branch

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CARPAL TUNNEL SYNDROME

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Differential Diagnosis

Pathologies affecting the central or peripheral nervous systems can cause paresthesia in the hand and fingers.

Figure 3.1

Sites of Compression of the Median Nerve

DISORDERS OF THE CENTRAL NERVOUS SYSTEM Transient cerebral ischemia and multiple sclerosis can cause paresthesia in the arm and hand. DISORDERS OF THE PERIPHERAL NERVOUS SYSTEM Paresthesia in the fingers may also be secondary to cervical radiculopathy (affecting C6 and C7), thoracic outlet syndrome, Raynaud’s syndrome, or compression of the median nerve, for example by the pronator teres in the forearm area. The simultaneous presence of a proximal disorder of the median nerve and compression at the wrist is termed “double crush syndrome” (Dupuis, 1986).

Struthers’ ligament Flexor digitorum superficialis (anterior interosseous nerve)

Pronator teres

Carpal tunnel

Paresthesia affecting the arm may be due to systemic disease such as diabetes mellitus, alcoholism, or smoking, or be the result of medication, contraceptive pills, or exposure to toxic substances such as lead, solvents, pesticides and plastics.

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4

Clinical Considerations

SYMPTOMS Sensory symptoms (paresthesia) affecting the first three fingers of the hand are the primary symptoms of compression of the median nerve at the wrist and usually precede motor symptoms. Pain radiating to the other fingers or the forearm may also be present. Documentation of the medical history of a patient consulting for hand or wrist complaints should include such key questions as:

– Where do you feel the pain? – When did the pain begin? – What did the pain first feel like, and what does it feel like now? Furthermore, in order to better estimate the magnitude of the complaints, their impact on the patient’s activities of daily living should be determined.

Box 4.1

Symptoms Reported by the Patient – Nocturnal paresthesia in the hand (numbness and tingling that usually disappear upon shaking the hand [Flick sign]) – Paresthesia during activities involving the hand or wrist – Pain in the hand, wrist, or forearm – Weakness of the hand and a loss of dexterity

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Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

Location of Symptoms (Where?) Hand and arm diagrams are very useful tools which help patients localise their symptoms and guide diagnosis. In addition, they allow the physician to accurately delimit the zones of paresthesia (Szabo and Madison, 1992; Katz and Stirrat, 1990).

Figure 4.1

Hand and Upper Limb Diagram

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Onset of Symptoms (When?) It is important to establish the time elapsed between the onset of symptoms and the medical consultation. As mentioned in the chapter on pathophysiology, CTS usually appears progressively: acute CTS is rare. Paresthesia may be intermittent initially (Stage 1), but later become constant (Stage 2). Physicians should remember to ask their patients the reason for the current consultation.

Characteristics of Onset (How?) During the taking of the medical history, patients should be asked to describe in detail the circumstances surrounding the appearance of symptoms. In most cases, the initial signs of CTS are nocturnal numbness which wakes the patient and intermittent paresthesia in the wrist or hand caused by

physical activity of variable intensity. An extrinsic cause (biomechanical strain) is strongly suggested by symptoms which intensify during specific tasks or activities and disappear when the patient is away from work (Porter et al., 1992). A staging scale for CTS symptoms is presented in Box 4.2

Box 4.2

Presentation and Clinical Severity of Symptoms Types of Symptoms Nocturnal symptoms

Symptoms related to physical activity involving the wrist and hand

Severity 0

Symptoms none

1

slight

some nights; symptoms relieved by wrist movements

2

moderate

every night; symptoms relieved by wrist movements

3

severe

every night; symptoms unrelieved by wrist movements

0

no pain during physical activity

1

slight

symptoms appear only after intense and repetitive activities

2

moderate

symptoms appear only after light or non-repetitive activities

3

severe

symptoms constant

Source: Adapted from Mahoney et al., 1992

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CARPAL TUNNEL SYNDROME

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

IMPACT ON ACTIVITIES OF DAILY LIVING Patients suffering from CTS may not only suffer pain but experience difficulty performing fine movements, picking up small objects, and accomplishing various daily tasks. These problems are primarily

indicative of sensory disorders; motor disorders, in contrast, lead to difficulty in opposing the thumb and fingers and performing finger-pinch movements. Box 4.3 presents a series of questions which help patients pinpoint the extent of their disability.

Box 4.3

Questions about Activities of Daily Living Which is your dominant hand?

Right ❐ Never

Do you have difficulty performing pinch activities such as: – writing with a pencil or pen – buttoning your shirt – holding a full cup – turning a key in a lock gripping movements such as: – unscrewing the cover of a jar – brushing your hair or using a hair-dryer – holding a newspaper in your hand to read – holding a telephone receiver – carrying a bag of groceries with handles

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Sometimes

Left ❐ Often

Always

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Recording of Information on Exposure Factors

Force, repetition, exposure to cold, and segmental vibration have all been shown to be work-related risk factors for carpal tunnel syndrome. Exposure to more than one of these factors synergistically increases the risk of developing carpal tunnel syndrome (Rossignol et al., 1996; Silverstein et al., 1987). Symptoms usually appear in the dominant hand or the hand suffering the most musculoskeletal load (Dupuis, 1986). Bilateral CTS is also possible, but in that case the symptoms are rarely of the same intensity in both hands (Silverstein et al., 1987).

OCCUPATIONAL HISTORY Previous Work The patient’s occupational history reveals the extent to which she or he has been subjected to wrist or hand stress in previous work as a result of exposure to repetitive movements, the application of pressure or force, exposure to cold, or the use of vibrating tools (Box 5.1). The presence of more than one factor in the occupational history increases the probability of a link between the CTS and work (Rossignol et al., 1995).

In order to establish a diagnosis of work-related carpal tunnel syndrome, it is necessary to identify the occupational, sports-related, recreational, or household activities which could have contributed to the development of the syndrome.

Box 5.1

Questions about Previous Work Work performed

Starting date and duration in months or years

Hours per day

Risk factors or cofactors*

15 * See Box 2.1

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

Current Work Patients should be asked to describe their current job in sufficient detail for physicians to understand clearly the nature of the work and the conditions under which it is performed. As it is generally difficult for physicians to visit the workplace, this guide provides a series questions designed to help them:

– characterise the general nature of the patient’s work (Box 5.2) – determine which, if any, biomechanical requirements associated with the patient’s work favour the development of CTS (Boxes 5.3 and 5.5) – evaluate the contribution of organisational factors to the development of CTS (Box 5.4)

Box 5.2

General Questions about Occupational Activities and Associated Symptoms – Is your current job full- or part-time? – Which hand do you use the most to perform your work? – Was an accident or an abrupt, sudden or unusual movement responsible for your pain? – Did your pain appear gradually? • If so, how long did it take to appear and what form did it take? – What actions and movements aggravate your symptoms?

There are a multitude of work-related activities that cause musculoskeletal strain. A list of common activities which may present a risk for the development of carpal tunnel syndrome are presented in Box 5.3. If a patient’s activities do not appear on this list, it may be useful to ask her or him to describe the activities or movements she or he finds

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difficult and evaluate their biomechanical characteristics (duration, frequency, force). Current Work and Organisational Factors Certain factors related to the nature and organisation of a patient’s work may favour the development of musculoskeletal disorders (Box 5.4).

Box 5.3

Questions about Activities that Cause Pain in the Hands or Wrist Activity

Hours per day

Frequency of movements low medium high

Force exerted low medium high

– Movements involving flexion, extension, or rotation of the wrist – Repeated finger-tapping movements – Applying pressure with the fingers or the palm of the hand – Manipulating small objects – Pulling or pushing objects – Use of vibrating or percussion tools (drills, drill presses, sanders, etc.) – Use of hand tools (screwdrivers, (knives, etc.) Other (describe)

Comments

Cofactors with increase musculoskeletalload

Never

Occasionnally

Regularly

– Wearing gloves at work – Exposure to cold – Arm abduction, or flexion exceeding 60 degres

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CARPAL TUNNEL SYNDROME

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

Box 5.4

Questions about Organisational Factors at Work During your work:

Never

Occasionnally

Regularly

– Do you feed a machine at a constant rhythm? – Do you feel time or production pressures? – Does your work need uninterrupted attention? – Do you find your work monotonous? – Can you vary your work rhythm? – Do you always work at the same workstation? Comments

SPORTS-RELATED, RECREATIONAL, AND HOUSEHOLD ACTIVITIES Sports-related, recreational, and household activities may contribute to the development of carpal tunnel syndrome. It is therefore important to establish

the intensity with which these activities are practised and whether the onset of pain in the hand or wrist has caused the patient to reduce their practise.

Box 5.5

Questions about Sports-related, Recreational, and Household Activities Involving the Hands or Wrist Activity 18

* See Box 2.1

Hours per week

Risk factors or cofactors*

Clinical Examination

6

The clinical examination should not be limited to the wrist and hand but must also extend to the entire arm and the neck. The stages of the examination include: – – – – –

Figure 6.1 Bony Limits of the Carpal Tunnel

Observation and palpation Provocative tests Evaluation of sensitivity Strength testing Electrophysiologic tests

OBSERVATION AND PALPATION As the internal structure of the carpal tunnel is not directly palpable, it is necessary to determine its boundaries through palpation. This palpation also identifies painful or sensitive points, tumour masses, and deformations. Figure 6.1 illustrates the bony limits of the carpal tunnel.

Hook of the hamate Pisiform

Tubercule of the trapezium Tubercule of the navicular

Box 6.1

Appearance of the Arms – Deviation, deformation, or antalgic postures or positions – Comparison of the two arms

State of the Wrist and Hand Tissues – Tissue trophicity: chronic neurological disorders may cause modifications of the cutaneous and subcutaneous tissues of the hand and inhibit perspiration – Tissue integrity: swelling, ulceration or calluses may indicate exposure to occupational mechanical load – Lateral atrophy of the thenar eminence

19

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

PROVOCATIVE TESTS Phalen’s and Tinel’s tests are provocative tests that elicit symptoms and are easy to perform (Table 6.1, Figures 6.2 and 6.3). Table 6.1 Clinical Provocation Tests Test (principle)

Execution

Positive result

Interpretation (result)*

Appearance of symptoms in less than 60 seconds

Sensitivity: 0.73-0.77 Specificity: 0.36-0.80

Phalen’s test: increased pressure in the carpal tunnel

Forced flexion of wrists

Tinel’s test: percussion of median nerve

Percussion of median Sensation of electric nerve on the palmar shock in the region aspect of the wrist of the nerve

Sensitivity: 0.45-0.63 Specificity: 0.47

Source: Rossignol et al, 1995

20

Figure 6.2

Figure 6.3

Phalen’s Test

Tinel’s Test

EVALUATION OF SENSITIVITY There are two types of tests for the assessment of the hand: – Innervation-density tests such as the static twopoint discrimination test; these may remain normal even in the presence of moderate neurological dysfunction. The presence of residual sensitivity such as pain perception may be de-

termined by evaluating the response to a pin prick (Table 6.2, Figure 6.4). – Sensory threshold tests, such as SemmesWeinstein monofilament test or those measuring vibration sensitivity. These are the most sensitive tests for the detection of early and slight neurological dysfunction (Figure 6.5).

Table 6.2 Tests of Sensory Function Test (principle)

Execution

Positive result

Interpretation (result)*

Static two-point discrimination test

Stimulation of slow nerve fibres

Two-point discrimination Sensitivity: 0.24 threshold exceeding Specificity: 1 6 mm (normal: 2-6 mm) Advanced neurological dysfunction

Semmes-Weinstein monofilament test

Tactile stimulation of the palmar aspect of the fingers by monofilaments of fixed diameter

Values above 2.83 in fingers innervated by the median nerve

Sensitivity: 0.79-0.81 Specificity: unknown Dysfunction of the median nerve

Source: Rossignol et al., 1995

Figure 6.4

Figure 6.5

Two-Point Discrimination Test

Semmes-Weinstein Test

21

CARPAL TUNNEL SYNDROME

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

STRENGTH TESTING

Compression disorders of the median nerve in the carpal tunnel may cause weakness in: – thumb abduction – thumb opposition – pinch movements

22

Various manoeuvres against resistance allow elicitation of motor deficits in the thenar muscles (Kendall et al., 1988). The test for the flexor polli-

cis brevis is not illustrated, as its action is difficult to isolate when the other muscles are not affected.

Figure 6.6

Figure 6.7

Abductor Pollicis Brevis

Opponens Pollicis

ELECTROPHYSIOLOGIC TESTS Both sensory and motor disorders can be identified with electrophysiologic tests. Positive and negative results should always be interpreted in the light of

the patient’s history and the results of the physical examination as well as other diagnostic results.

Table 6.3 Electrophysiologic Tests Tests (principle) Median nerve conduction studies

Electromyography (EMG) Axonal transmission of nerve impulses to the thenar muscles

Execution

Positive result

Interpretation (result)*

Recording of the sensory action potential

Prolongation of the latency: • sensory: >3.5 msec or asymmetry >0.5 msec compared to the other hand

Sensory nerve conduction Sensitivity: 0.70-0.90 Specificity: unknown

Recording of the motor action potential

• motor: >4.5 msec or asymmetry >1.0 msec compared to the other hand

Motor nerve conduction Sensitivity: 0.65-0.75 Specificity: unknown

Insertion of electrodes into the muscles

Fibrillation, increased insertion impulse waves

Sensitivity: 0.11-0.37 Specificity: unknown Avanced compression of the median nerve

Source: Rossignol et al., 1995; Szabo et al. 1992

23

CARPAL TUNNEL SYNDROME

7

Summary of the Evaluation

Box 7.1

Clinical Aspects YES ❏

Are symptoms located in the innervation field of the median nerve? EXTENT OF PROBLEMS

None

NO ❏

Slight

Moderate

Yes

No

– Pathological conditions of the carpal tunnel (p. 5)

❏

❏

– Other pathological conditions (p. 5)

❏

❏

❏

❏

Slight

Moderate

Severe

Symptoms reported – Frequency and intensity of symptoms (p. 11-12-13) – Disruption of activities of daily living (p. 14) Physical examination – Abnormal results on provocative tests (p. 20) – Diminished sensory function (p. 21) – Diminished strength (p. 22) – Abnormal results on electrodiagnostic tests (p. 23) Relevant medical history and conditions

Differential diagnosis – Central or peripheral neuropathy (p. 9) Exposure factors

None

Severe

– During previous jobs (p. 15) – During current job (p. 16-17-18) – In sports-related recreational, or household activities (p. 18) RELATION TO WORK

25

Guidelines for Therapeutic and Preventive Interventions

8

This section presents some fundamental therapeutic and preventive principles, without describing specific interventions in detail. These principles should prove useful in developing an approach to the management of CTS cases.

THERAPEUTIC GUIDELINES This approach is derived from the recommendations of the American Academy of Neurology (1993) (Figure 8.1) and is applicable to every symptom which interferes with the activities of daily living. Severe disturbances correspond to the presence of continuous paresthesia. This approach is however inappropriate when symptoms are caused by underlying systemic factors.

Figure 8.1

Therapeutic Intervention Flow-chart Carpal Tunnel Syndrome

Slight problems

Reduction of musculoskeletal load Modification of activities Resting splint Improvement

Severe problems

Moderate problems

Surgical decompression

No improvement Consider infiltration

Improvement

No improvement Continue treatment for 3-6 months

27 Improvement

No improvement, or deterioration

APPLICATION OF RISK-FACTOR-SPECIFIC CORRECTIVE AND PREVENTIVE MEASURES

Guide To The Diagnosis Of Work-Related Musculoskeletal Disorders

The cornerstone of the therapeutic approach to slight or moderate problems is the imposition of rest on the structures subjected to musculoskeletal strain. Splint immobilisation should only be resorted to for short periods—preferably at night—and should not be used to allow symptomatic patients to return to work. The therapeutic approach should also include measures designed to eliminate the causal factors identified.

PREVENTION GUIDELINES Table 8.1 lists general guidelines for preventive measures which take into account the diagnosis and extent of musculoskeletal strain. The preventive approach should include measures designed to correct working conditions and physical activities that favour the development of CTS. The application of these measures is essential to prevent deterioration or recurrence of the injury, or aggravation of the symptoms upon return to work.

Table 8.1

Preventive Approach Diagnosis

Evidence of carpal tunnel syndrome

No evidence of carpal tunnel syndrome

28

Musculoskeletal strain Significant

Not significant

+

–

+

– Modification of activities – Reduction of musculoskeletal load – Corrective ergonomic interventions

– Treatment of causal factors – Modification of activities

–

– Reduction of musculoskeletal load – Corrective ergonomic interventions

– Information on risk factors

CONCLUSION

This guide was designed to help physicians, who in recent years have been faced with an increase in the number of consultations for musculoskeletal problems of possible occupational etiology. The core elements of current knowledge on the subject have been reviewed and an approach that facilitates the documentation of the injury’s clinical aspects and its dependence on occupational musculoskeletal load presented. Furthermore, a therapeutic approach that integrates preventive elements designed to reduce the impact of risk factors has been outlined. The hand is a precious tool. The reduction of musculoskeletal injuries associated with repetitive work depends on the commitment of physicians: their clinical and etiological diagnoses trigger a series of actions that affect not only the patient but also the factors responsible for the injury.

29

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