Minimally Invasive Plate Osteosynthesis (MIPO)

AO Manual of Fracture Management Minimally Invasive Plate Osteosynthesis (MIPO)

G On Tong, Suthorn Bavonratanavech

The book is divided into two sections; the first section deals with general principles while the second section deals with the anatomical regions that current MIPO techniques are applicable to.

Martin Allgöwer Professor, Dr hc mult Honorary Chairmain and Founding Menber of AO

The book is written in a simple and easy-to-understand style with many case examples included to provide the reader with a broad spectrum of the type of problems that may be encountered in everyday practice. The book is well illustrated and animations and video clips are included to enhance the learning experience. This book is highly recommended for those surgeons who are interested in learning more about the current practice of MIPO.

www.aofoundation.org

MIPO_Cover_Final.indd 1

Rest of World ISBN 10 3-13-143391-4 ISBN 13 978-3-13-143391-6

The Americas ISBN 10 1-58890-544-6 ISBN 13 978-1-58890-544-4

Tong, Bavonratanavech

The book concerning concepts and cases presented by AO East Asia is another far reaching proof of the new brotherhood of trauma surgeons spreading successfully the AO community advocating early total care of the accident victims described in very detail.

Minimally Invasive Plate Osteosynthesis (MIPO)

This is the first book on the subject of minimally invasive plate osteosynthesis (MIPO) that has been published. It includes current recommendations on this subject as taught in the AO MIPO Courses organized by AO East Asia. It should serve as a useful guide for those trauma surgeons who lack the experience but wish to learn more about this subject before starting to do the actual surgical procedures. Even for those with some experience in this field, the book contains many useful and practical tips that can be added to one’s armamentarium.

AO Manual of Fracture Management

Minimally Invasive Plate Osteosynthesis (MIPO) Concepts and Cases presented by AO East Asia

AO Teaching Videos on DVD-ROM included

9/5/06 1:43:08 PM

G On Tong

Suthorn Bavonratanavech

AO Manual of Fracture Management

Minimally Invasive Plate Osteosynthesis (MIPO)

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G On Tong

Suthorn Bavonratanavech

AO Manual of Fracture Management

Minimally Invasive Plate Osteosynthesis (MIPO)

440 Illustrations 400 Photos AO Teaching Videos and Animations on DVD-ROM

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Illustrations: tadpole gmbh, 8048 Zürich Layout and typesetting: AO Publishing, CH-8600 Dübendorf

Library of Congress Cataloging-in-Publication Data is available from the publisher.

Hazards Great care has been taken to maintain the accuracy of the information contained in this publication. However, the publisher, and/or the distributor, and/or the editors, and/or the authors cannot be held responsible for errors or any consequences arising from the use of the information contained in this publication. Contributions published under the name of individual authors are statements and opinions solely of said authors and not of the publisher, and/or the distributor, and/or the AO Group. The products, procedures, and therapies described in this work are hazardous and are therefore only to be applied by certified and trained medical professionals in environments specially designed for such procedures. No suggested test or procedure should be carried out unless, in the user‘s professional judgment, its risk is justified. Whoever applies products, procedures, and therapies shown or described in this work will do this at their own risk. Because of rapid advances in the medical sciences, AO recommends that independent verification of diagnosis, therapies, drugs, dosages, and operation methods should be made before any action is taken. Although all advertising material which may be inserted into the work is expected to conform to ethical (medical) standards, inclusion in this publication does not constitute a guarantee or endorsement by the publisher regarding quality or value of such product or of the claims made of it by its manufacturer. Legal restrictions This work was produced by AO Publishing, Davos, Switzerland. All rights reserved by AO Publishing. This publication, including all parts thereof, is legally protected by copyright. Any use, exploitation or commercialization outside the narrow limits set forth by copyright legislation and the restrictions on use laid out below, without the publisher‘s consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, scanning or duplication of any kind, translation, preparation of microfilms, electronic data processing, and storage such as making this publication available on Intranet or Internet. Some of the products, names, instruments, treatments, logos, designs, etc. referred to in this publication are also protected by patents and trademarks or by other intellectual property protection laws (eg, ”AO”, ”ASIF”, ”AO/ASIF”, ”TRIANGLE/GLOBE Logo” are registered trademarks) even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name, instrument, etc. without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain. Restrictions on use: The rightful owner of an authorized copy of this work may use it for educational and research purposes only. Single images or illustrations may be copied for research or educational purposes only. The images or illustrations may not be altered in any way and need to carry the following statement of origin ”Copyright by AO Publishing, Switzerland.”

Check hazards and legal restrictions on www.aofoundation.org/legal Copyright © 2007 by AO Publishing, Switzerland, Clavadelerstrasse, CH-7270 Davos Platz Distribution by Georg Thieme Verlag, Rüdigerstrasse 14, D-70469 Stuttgart, Germany and Thieme New York, 333 Seventh Avenue, US-New York, NY 10001 Acknowledgments: Picture in Fig 1-2b courtesy of Wilson JW (2002) Blood supply to developing, mature, and healing bone. Sumner-Smith G (ed), Bone in Clinical Orthopedics. Stuttgart New York: Georg Thieme Verlag, 86. Picture in Fig 2-3 courtesy of Rand JA et al (1981) A comparison of the effect of open intramedullary nailing and compression-plate fixation on fracture site blood flow and fracture union. J Bone Joint Surg; 63A:427–442. Picture Fig 2-4 courtesy of Rahn BA (2002) Bone healing: histological and physiological concepts. Sumner-Smith G (ed), Bone in Clinical Orthopedics. Stuttgart New York: Georg Thieme Verlag, 307. ISBN 10 3-13-143391-4 (GTV) ISBN 13 978-3-13-143391-6 (GTV)

ISBN 10 1-58890-544-6 (TNY) ISBN 13 978-1-58890-544-4 (TNY)

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Table of contents Foreword Preface

vii x

Contributors

xii

Acknowledgments

xiv

Principles

1

2

359

3

Mechanobiology

9

—Kok-Sun KHONG, Ramakrishna KOTLANKA, Dhanjoo N GHISTA 3

Glossary

History and evolution of MIPO

—G On TONG

Instruments

23

—Suthorn BAVONRATANAVECH 4

Implants

33

—Frankie KL LEUNG 5

Intraoperative imagin g

47

—Kok-Sun KHONG, Fareed KAGDA 6

Computer assisted surgery in MIPO

57

—Merng Koon WONG 7

Reduction techniques

67

—Frankie KL LEUNG, Shew-Ping CHOW 8

Decision making and preoperative planning

79

—Tadashi TANAKA 9

Postoperative management

93

—Tadashi TANAKA, Toru SATO 10

Complications and solutions

101

—Theerachai APIVATTHAKAKUL

v

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Cases

11

Humerus, proximal

121

16

Tibia and fibula, proximal

255

—Merng Koon WONG, Suthorn BAVONRATANAVECH, Frankie KL LEUNG

—Merng Koon WONG, Suthorn BAVONRATANAVECH, Frankie KL LEUNG

11.1 Humerus, proximal: extraarticular unifocal fracture,

16.1 Tibia and fi bula, proximal: complete articular fracture,

nonimpacted, metaphyseal—11-A3

131

11.2 Humerus, proximal: extraarticular unifocal fracture,

articular simple, metaphyseal simple—41-C1

nonimpacted, metaphyseal—11-A3 with diaphyseal

12

pure split—41-B1

involvement

137

Humerus, shaf t

145

12.1 Humerus, shaft: wedge fracture, bending wedge—12-B2 157

metaphyseal, multifragmentary—41-A3 with

17

diaphyseal involvement

275

Tibia and fibula, shaft

281

12.2 Humerus, shaft: complex fracture, irregular—12-C3

163

—Theerachai APIVATTHAKAKUL, Kok-Sun KHONG

12.3 Humerus, shaft: complex fracture, spiral—12-C1

169

17.1 Tibia and fi bula, shaft: wedge fracture,

12-B3

173

17.2 Tibia and fi bula, shaft: wedge fracture,

Femur, proximal

181

12.4 Humerus, shaft: wedge fracture, fragmented wedge—

fragmented wedge–42-B3

—Suthorn BAVONRATANAVECH, Theerachai APIVATTHAKAKUL

18

13.1 Femur, proximal: extraarticular fracture,

203

Femur, shaft

209

Femur, distal

317

articular simple, metaphyseal, multifragmentary—

19

43-C2

321

Clavicle

327

—Vajara PHIPHOBMONGKOL 339

19.2 Clavicle, shaft: simple transverse fracture—OTA 15-A3 347

14.1 Femur, shaft: wedge fracture, fragmented wedge—

15

305

19.1 Clavicle, shaft: spiral wedge fracture—OTA 15-B1

—Suthorn BAVONRATANAVECH, Theerachai APIVATTHAKAKUL

14.2 Femur, shaft: wedge fracture, spiral wedge—32-B1

Tibia and fibula, distal

simple—43-A1

199

pertrochanteric, multifragmentary—31-A2

32-B3

299

18.2 Tibia and fi bula, distal: complete articular fracture,

13.3 Femur, proximal: extraarticular fracture,

14

fragmented wedge–42-B3

18.1 Tibia and fi bula, distal: extraarticular fracture, 193

13.2 Femur, proximal: extraarticular neck fracture, subcapital with slight displacement—31-B1,

295

—Young-Soo BYUN, Chang-Wug OH

intertrochanteric—31-A3 and complex spiral diaphyseal fracture—32-C1

269

16.3 Tibia and fibula, proximal: extraarticular fracture,

—Theerachai APIVATTHAKAKUL

13

265

16.2 Tibia and fi bula, proximal: partial articular fracture,

221 225

231

19.3 Clavicle, shaft: simple oblique fracture—OTA 15-A2 with marked displacement

353

19.4 Clavicle, shaft: simple transverse fracture—OTA 15-A3 357

—Suthorn BAVONRATANAVECH, Frankie KL LEUNG 15.1 Femur, distal: partial articular fracture of the medial condyle—33-B2 and spiral wedge shaft fracture—32-B1 243 15.2 Femur, distal: extraarticular fracture, simple—33-A1 and simple spiral shaft fracture—32-A1 15.3 Femur, distal: extraarticular fracture, simple 33-A1

247 251

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Foreword Martin Allgöwer

It is a real privilege to be asked for a short greeting in your excellent and extremely competent “AO Manual of Fracture Management—Minimally Invasive Plate Osteosynthesis (MIPO)” published by G On Tong and Suthorn Bavonratanavech. The book concerning concepts and cases presented by AO East Asia is another far reaching proof of the new brotherhood of trauma surgeons spreading successfully the AO community advocating early total care of the accident victims described in very detail. The authors are giving every evidence of their seasoned mastership in the surgery of trauma—congratulations!

Martin Allgöwer Professor, Dr hc mult Honorary Chairmain and Founding Member of AO Basel, June 2006

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Foreword Reto H Babst

The aim to add minimal further trauma to the traumatized patient is a long standing tradition in orthopedic trauma surgery. Minimal access surgery or minimal invasive surgery (MIS) was fi rst introduced with external fi xation in fracture fi xation in the 19th century, with development of arthroscopic surgery and endomedullary nailing in the 20th century. The cosmetically appealing small incisions were not the striking factors that prompted the rapid progression of these minimal invasive techniques but the biological advantages, such as undisturbed fracture healing, less soft-tissue compromise and fewer infectious complications associated with faster recovery. The step from the observation of the similarities of the fracture healing pattern when using an extramedullary splint applied by indirect reduction technique, as seen when using an endomedullary nail, to the development of the submuscular plating technique was attempted during the late 1990s. New plate designs like the LISS and the LCP some years ago supported the rapid progression of this new approach to fracture treatment by minimally invasive plate osteosynthesis (MIPO) all over the world. Since there is no evident biological marker to defi ne surgical invasiveness, minimally invasive osteosynthesis should be geared to some basic principles and defi nitions. Minimally invasive osteosynthesis (MIO) includes all forms of fracture fi xation that: use small soft-tissue windows to allow insertion of implants or instruments cause minimal additional trauma to the soft tissue and fracture fragments

use indirect (traction table, external fi xator, distractors, manual traction) or direct reduction techniques (K-wires, reduction screws, percutaneous reduction forceps, joysticks) can apply the biomechanical concepts of relative stability or, exceptionally, absolute stability. By this defi nition, MIO includes all types of percutaneous fracture fi xation such as external fi xation, closed intramedullary nailing, percutaneous K-wire or screw fi xation as well as MIPO. Thanks to the AO East Asian Section we have this book in hand which has undertaken the challenge to combine their accumulated practical knowledge of the application of MIPO techniques with the well-known principles of fracture treatment by the AO philosophy. The different chapters cover step by step the different prerequisites to apply MIPO techniques successfully. They not only describe the principles of critical case analysis, preoperative planning, mechanobiology and radiation hazards but also stress the importance of the different direct and indirect reduction techniques and the necessary instruments to provide MIPO with minimal additional softtissue damage. The limited view of the fracture site makes this technique more demanding than ORIF, with the potential for resultant malunion. In addition, direct percutaneous fracture reduction has the hazard of neurovascular damage. Prevention of complications and possible solutions are also included in this book as is computer assisted navigation as a potential tool to overcome some of MIPO’s shortcomings.

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The practical application of MIPO techniques in the different skeletal regions, even though they reflect personal preferences, give invaluable step-by-step information to the experienced surgeon. MIPO techniques represent a fascinating new armamentarium in fracture fi xation, which is made easier with the LCP technology and the different available MIS instruments, which were developed to cause less additional damage to the soft tissue and the bone. The biological advantage of MIPO, however, is only assured when we adhere to the basic principle of fracture care. MIPO should not serve as an excuse for a badly performed osteosynthesis! With this in mind MIPO will continue to develop its potential to reduce bone and soft-tissue healing problems and to speed rehabilitation.

Reto H Babst, MD Professor and Chairman Department of Surgery Chief of Trauma Surgery Kantonsspital Luzern Switzerland Luzern, June 2006

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Preface The fi rst AO minimally invasive plate osteosynthesis (MIPO) Course in East Asia was held in Singapore on April 14–17, 2004. Although minimally invasive osteosynthesis (MIO) courses had been previously conducted elsewhere in the world, the Singapore course was the fi rst official AO Course dedicated to MIPO and the most comprehensive to date. It was also the fi rst to include cadaveric workshops.

Regional Combined AO Courses. It is worthwhile noting that a significant part of these courses was drawn from contributions by the AO East Asia MIPO Study Group, which was set up with the specific aims of doing research and improving the educational content and teaching methods of MIPO techniques. Likewise, the work of this group constitutes the basis of a significant part of this book.

The Singapore MIPO Course was also remarkable for two other reasons. Firstly, a significant number of the faculty members were from East Asia and unlike most other AO Courses, these regional faculty members made presentations that were in many ways original and based on their own work and experience. They showed many novel ways of performing MIPO and also introduced some innovative instruments that were fabricated locally to facilitate the surgical procedures. This made a strong impression, not only among the course participants, but also among the distinguished international faculty members. This marked the start of a strong collaborative effort between the international and regional experts in the field of MIO which culminated in the invitation of Dr Theerachai Apivatthakakul, who is one of the members of the AO East Asia MIPO Study Group, to join the MIO Expert Group of the AO Technical Commission (AOTK). The second remarkable feature was that the course was extremely well received despite the fact that MIPO was a relatively new method of fracture treatment. In fact, the course proved to be so successful that the course format was adopted to serve as a template for future AO MIPO Courses. The demand for MIPO Courses was so great that before long, there was a clamor for the course to be repeated elsewhere in the East Asian region. Thus, the Hong Kong AO Course was held in 2005 and most recently, in 2006, the course was conducted in Chiang Mai, Thailand, as part of the

It became obvious that there was a tremendous interest in the application of MIPO principles and techniques by orthopedic surgeons subspecializing in musculoskeletal trauma. The trend toward biological methods of fracture fi xation was gathering momentum and MIO was a logical step toward realizing this aim. It would not be realistic for everyone interested in learning the intricacies of MIPO techniques to attend a MIPO Course before embarking on this type of surgery. Furthermore, there has so far not been any manual type of book written on the subject. Hence the object of this book is to fulfi ll such a need. This book is an attempt to introduce the reader to the basic principles and concepts of MIPO and illustrate, by way of clinical case examples, the way these concepts are put into practice. It is by no means a defi nitive work. MIPO is a relatively recent phenomenon and is evolving at a rapid rate, which is why it is so exciting. New approaches are being described and new implants and instruments are being introduced to make the procedures easier and more reproducible. However, the important thing is to understand the principles and to apply them correctly. While it is good to have the latest instruments and implants, these are by no means absolutely essential. Conventional implants can be adapted for MIPO surgery and the results can be just as gratifying as shown in many of the cases illustrated in this book.

x

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It is hoped that this book will provide the reader with the starting point for treating fractures using MIPO techniques. It is also hoped that the book will provide a stimulus for the surgeon to develop an interest in this subject and as the experience increases, to be able to critically evaluate the current methods that are being used and make contributions for their improvement. Much remains to be done in the field of MIPO and many discoveries and innovations are waiting to be made. It is hoped that this book can provide the catalyst for this to occur.

G On Tong Singapore, July 2006

Suthorn Bavonratanavech Bangkok, July 2006

xi

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Contributors Editors and authors

Authors

G On TONG, FAMS, MBBS, MMED, MCH, FRCS

Theerachai APIVATTHAKAKUL, MD

Orthopaedic Associates

Trauma Division, Department of Orthopaedics

Mount Elizabeth Hospital

Faculty of Medicine, Chiang Mai University

16-03/04, Mount Elizabeth Medical Centre

TH-Chiang Mai 50200

3 Mount Elizabeth SG-Singapore 228510

Young-Soo BYUN, MD PhD Chief, Department of Orthopedic Surgery

Suthorn BAVONRATANAVECH, BSC, MD

Taegu Fatima Hospital

Thai Board of Orthopedic Surgery

576-31 Sinam-Dong Dong-Gu

Orthopaedic Center

KR-Taegu 701-600

Bumrungrad Hospital 33 Sukhumvit 3 (Soi Nana Nua)

Shew-Ping CHOW, MBBS, LMCC, FRCS, FACS, MS, FHKAM

Sukhumvit Road Klongtoey

Professor

TH-Wattana, Bangkok 10110

Department of Orthopaedics and Traumatology University of Hong Kong Medical Centre 5/F, Professorial Block, Queen Mary Hospital HK-Pok Fu Lam Dhanjoo N GHISTA, PhD Professor Chief, Bioengineering Division Nanyang Technological University 50 Nanyang Avenue SG-Singapore 639798 Fareed KAGDA, MBBS, FRCS, FRCSEd (Orth) Consultant, Division of Orthopaedic Trauma Department of Orthopaedic Surgery National University Hospital 5 Lower Kent Ridge Road SG-Singapore 119074

xii

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Authors

(cont)

Kok-Sun KHONG, MBBS, Mmed (Surg), FRCSG, FAMS

Toru SATO, MD

KS Khong Orthopaedic Practice

Chief of Orthopedic Surgery

16-03/04 Mt Elizabeth Medical Centre

National Hospital Organization Okayama Medical Center

3 Mt Elizabeth

Tamasu 1711-1, Okayama City

SG-Singapore 228510

JP-Okayama

Ramakrishna KOTLANKA, B Eng, PhD

Tadashi TANAKA, MD, DMSc

Research Scholar

Vice-director

Nanyang Technological University

Kimitsu Chuo Hospital

50 Nanyang Avenue

1010 Sakurai, Kisarazu

SG-Singapore 639798

JP-Chiba 292-8535

Frankie KL LEUNG, MD, MBBS, FRCS, FHKCOS, FHKAM

Merng Koon WONG, MD, MBBS, FRCS, FAMS

Consultant Orthopaedic Surgeon

Director of Orthopaedic Trauma

Department of Orthopaedics and Traumatology

Director of AO Centre Singapore

University of Hong Kong Medical Centre

Department of Orthopaedic Surgery

5/F, Professorial Block, Queen Mary Hospital

Singapore General Hospital

HK-Pok Fu Lam

Outram Road SG-Singapore 169608

Chang-Wug OH, MD Department of Orthopedic Surgery Kyungpook National University Hospital 50 Samdok 2ga, Chung-Gu KR-Taegu 700-721 Vajara PHIPHOBMONGKOL, MD, Group Captain Chief of Medical Education Department Department of Orthopaedic Surgery Bhumibol Adulyadej Hospital Royal Thai Airforce 171 Phaholyothin Road, Klongtanon, Saimai TH-Bangkok 10220

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Acknowledgments This book is the result of a collaborative effort by many people who have put in many hours of hard work. The Editors, in particular, wish to express their deep appreciation and gratitude to the following: David Helfet, Chairman of the AO Documentation and Publishing Foundation, whom we approached and broached the idea of producing this book and who agreed to support the project without the slightest hesitation. Professor Martin Allgöwer for writing the foreword of this book.

Roger Kistler, who was responsible for preparing the overall layout of this book. The Editors made multiple changes to the text and layout in order to improve the language and content of the chapters. Roger obligingly incorporated the changes and made the necessary adjustments to come out with the fi nal version of this book. The team of illustrators working for AO Publishing who have made the wonderful and clear illustrations and animations and who have shown great patience and tolerance to the many requests for changes that have been asked of them. The AO Video Team in Davos who edited our videos to ensure that they are of a high quality.

Reto Babst for writing the foreword of this book. Urs Rüetschi, Head of AO Publishing, who helped and guided us through every stage of the production of this book.

Members of the AO East Asia MIPO Study Group whose work and ideas has been the inspiration for this book. All the authors who have contributed to this book.

Andy Weymann, Head of AO Education Concepts, who provided invaluable advice whenever the Editors were faced with seemingly insoluble problems. Renate Huter, Project Coordinator from AO Publishing, who was assigned to do this project. Renate has demonstrated great professionalism in her work and shown infi nite patience in her dealings with us. Always approachable, she was prepared to travel great distances so that she could meet up with us to discuss the project. Her enthusiasm and attention to detail was the main driving force behind the successful completion of this book.

Members of AO East Asia whose unstinting support had made this book possible. The many AO surgeons and colleagues who have provided many valuable ideas and suggestions that have helped to make this book a reality. Our wives, Chew Ching and Sinaporn, whose support and encouragement have given us the strength to see this book through to its conclusion.

G On Tong, Suthorn Bavonratanavech

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Principles

1

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2

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Author

1

G On TONG

History and evolution of MIPO

In the fi rst edition of “Technique of Internal Fixation of Fractures” published in 1965, the founding fathers of the AO laid down the following theoretical and practical principles of rigid internal fi xation: Anatomical reduction Rigid fi xation of fragments Preservation of vascularization of the bone fragments In their elaboration of these principles, the authors stated that direct healing of bone had become a clinical and radiological concept. It was also called “fracture union without visible callus formation”. They believed that any excess callus should be considered detrimental, regarded as a kind of “keloid” of the bone, and indicated movement at the fracture site. Any radiologically visible callus formation during fracture healing after internal fi xation was regarded as a warning that should initiate appropriate action. Union without radiologically visible callus, on the other hand, appeared to be the most desirable form of healing. The healing of a fracture without callus could be regarded as radiological evidence of continuous rigid fi xation.

The principles most attractive to surgeons were those of anatomical reduction and stable internal fi xation, possible explanations being that these were the more visible and tangible of the principles as the results could be seen on x-rays. Furthermore, practical exercises at AO Courses were conducted using plastic bones stripped of soft tissues, thus giving the false impression that the soft tissues could be ignored. To be fair, in those cases of fractures treated by anatomical reduction and stable fi xation with successful outcomes, and there were many, the results were impressive—patients were regaining painfree mobility and function of their injured limbs shortly after surgery. “Fracture disease” soon became a thing of the past. However, despite the inclusion of preservation of blood supply

These views were further supported by the experimental demonstration of direct bone healing by Willenegger and Schenk. The trend, therefore, was for all fractures to be anatomically reduced and rigidly fi xed, with direct bone healing without visible callus formation as the desired end result (Fig 1-1). Subsequent editions of the “Manual of Internal Fixation” restated the treatment principles as: Anatomical reduction Stable internal fi xation Preservation of blood supply Early pain-free mobilization of muscles and joints adjacent to the fracture

a Fig 1-1a–b

b X-rays of a diaphyseal fracture fi xed with lag screws and

compression plate showing signs of direct bone healing.

3

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as one of the original treatment principles, and the emphasis on careful handling of soft tissue during surgery, these two elements of fracture management did not receive as much attention from the orthopedic community. During this time, research and development were directed at improving the rigidity of internal fi xation. The concepts of interfragmental compression with lag screws and compression plates, fi rst with the articulating tension device and then with dynamic compression plates (DCP), were introduced. However, it soon became apparent that rigid internal fi xation of fractures did not always produce the desired end result. Instances of sepsis, sequestrum formation, delayed or nonunion, and refractures were observed.

a

Research into these failures led to the discovery of the phenomenon of temporary porosis in the area of the footprint of the plate on bone. The cause of this was considerable damage to the periosteal circulation resulting at the interface between the implant and the bone (Fig 1-2).

Studies using special undercut plates showed that the grooves in the plates reduced vascular damage and mitigated bone porosis. This led to the development of a special undercut plate, the limited contact dynamic compression plate (LC-DCP) (Chapter 4 Implants: Fig 4-6).

b

Fig 1-2a–b a

Phenomenon of temporary porosis.

b

Photomicroangiograph of a transverse section of femur from a mature dog, 6 weeks after placement of a plate. The cortex at the 12 o’clock position, which was directly under the plate is devoid of arterioles, whereas the remainder of the cortex is vascular and viable.

4

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1

History and evolution of MIPO

Thus, the fi rst moves away from mechanical stability of internal fi xation toward biological internal fi xation were made.

Similarly, the strain in fractures with a larger gap width was also reduced.

Further evidence that absolute rigidity was not always necessary for fracture union came from the observation that fractures with flexible fi xation also heal, albeit with callus formation. Such examples of flexible fi xation or splinting came from intramedullary nails, external fi xators, internal fi xators, bridging, and wave plates. In fact, indirect healing often led to early and reliable solid bone union.

It became apparent that anatomical reduction and rigid internal fi xation were not absolutely necessary to achieve union in multifragmentary diaphyseal fractures. Fracture reduction in multifragmentary diaphyseal fractures became simpler and consisted mainly of regaining length, rotation, and axial alignment.

The development of indirect methods of fracture reduction for diaphyseal fractures using the principle of ligamentotaxis led to the avoidance of further damage to the blood supply of the fracture fragments, which accompanied direct manipulation of the fracture ends. Furthermore, it was shown that internal fi xation based only on reducing the mobility of the fracture fragments, without contact between the bone fragments, could result in solid healing. Thus, multifragmentary fractures fi xed with bridging plates demonstrated high union rates without the need for bone grafting (Fig 1-3). The explanation for this was based on the concept of interfragmentary strain. The concept of interfragmentary strain states that fractures with a single, narrow gap are very intolerant of even minute amounts of displacement due to deformation of repair tissues, while multifragmentary fractures can tolerate a greater degree of instability as the overall displacement is shared between many fracture gaps.

a Fig 1-3a–b

b X-rays of a multifragmentary diaphyseal fracture fi xed

with a bridging plate showing union with callus formation.

5

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Thus the stage was set for the progression to more biological methods of fracture fi xation, namely minimally invasive osteosynthesis (MIO). MIO is not a new concept in orthopedic surgery. Closed intramedullary nailing, and percutaneous fi xation of fractures using screws and K-wires had been performed with satisfactory results. The application of plates using minimally invasive surgical techniques, however, was not carried out until the advent of the internal fi xator system which had as its main objective the elimination of the ill effects of plate– bone contact.

The introduction of the PC-Fix was the fi rst step in the realization of the biological advantages of locking head screws (LHS), which preserve both the periosteal and endosteal blood supply. Furthermore, these screws, being self-drilling and selftapping, offered the advantage of simple handling. Following in the footsteps of the PC-Fix was the less invasive stabilization system (LISS), which is described in Chapter 4. It was designed for application in the metaphyseal and epiphyseal areas of, fi rst, the distal femur (Fig 1-4), and then, the proximal tibia. The LISS could be considered the first plate that was specifically designed and instrumented for application using a minimally invasive submuscular approach.

The LISS has a special insertion handle which facilitates the introduction of the implant submuscularly and, at the same time, acts as a drill guide for accurate insertion of the screws through separate small stab wounds. The LHS, which are used with this system, also offer angular stability to the construct. The locking compression plate (LCP) was the third in the series of internal fi xators to be introduced and has the unique feature that it can be used either as a standard dynamic compression plate or as an internal fi xator due to the ingenious design of a special combination plate hole (Chapter 4 Implants: Fig 4-3).

a Fig 1-4a–b example.

b Less invasive stabilization system (LISS) and a case

The LCP can be used for diaphyseal fractures and when applied in the internal fi xator mode, offers the advantage of maintenance of primary reduction of the fracture while avoiding any secondary loss of reduction under load (Fig 1-5).

6

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1

History and evolution of MIPO

This feature makes the LCP suitable for minimally invasive application as it eliminates the need for accurate contouring of the plate to the bone. Another advantage is that, with the use of self-drilling, self-tapping LHS, the need for drilling, measuring, and tapping is no longer necessary. Experimental studies have also confi rmed the advantage of minimally invasive plate osteosynthesis (MIPO) in the femur in preserving the integrity of the perforating arteries as well as the nutrient arteries. Further developments in the field of MIPO included the introduction of new types of LCP designed for use in specific

anatomical regions such as the proximal and distal humerus, distal femur, proximal and distal tibia (Chapter 4 Implants: Fig 4-4). At the same time, instruments that facilitate the surgical procedure are being introduced. Multicenter trials are being conducted to test the efficacy of these new methods, and research is ongoing. Although MIPO is a relatively new concept in fracture treatment, it is slowly gaining acceptance because the underlying principles are sound. Improved instruments and implants are being developed and, with ongoing research and clinical trials, it has the potential of becoming one of the mainstays of fracture management in the years to come.

Suggested reading Farouk O, Krettek C, Miclau T, et al (1997) Minimally invasive plate osteosynthesis and vascularity: preliminary results of a cadaver injection study. Injury; 28(1):A7–A12. Mast J, Jakob R, Ganz R (1989) Planning and Reduction Technique in Fracture Surgery. 1st ed. Berlin Heidelberg New York: Springer-Verlag. Müller ME, Allgöwer M, Schneider R, et al (1979) Manual of Internal Fixation. Berlin Heidelberg New York: Springer-Verlag. Müller ME, Allgöwer M, Schneider R, et al (1991) Manual of Internal Fixation. 3rd ed. Berlin Heidelberg New York: Springer-Verlag. Müller ME, Allgöwer M, Willenegger H (1965) Technique of

a

b

Internal Fixation of Fractures. Berlin Heidelberg New York: SpringerVerlag.

Fig 1-5a–b

X-rays of a distal tibial fracture fi xed by the MIPO

method with a metaphyseal LCP.

Rüedi TP, Murphy WM (2001) AO Principles of Fracture Management. Stuttgart New York: Georg Thieme Verlag.

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2

Mechanobiology

1

Introduction

9

2

Mechanobiology of fracture repair

9

2.1

Mechanical influence on the fracture repair phases

9

2.1.1

Phase of inflammation and tissue response

2.1.2

Phase of intramembranous and endochondral ossification

2.1.3

Phase of fracture consolidation

2.1.4

Phase of bone remodeling

2.2

Biomechanics of fracture callus

10

2.3

Stability in fracture healing

12

2.3.1

Absolute stability

2.3.2

Relative stability

3

The application of gap strain theory

3.1

Fracture gap strain

13

3.2

Osteosynthesis with plate fixation

14

4

Mechanobiology in fracture fixation

67

4.1

Important aspects of the plate

14

4.2

Important aspects of screws

15

4.2.1

Screw design

4.2.2

Number of screws in a plate

4.2.3

Influence of screw placement relative to the fracture site

13

4.3

Bone–plate interface

17

4.4

Helical plating

18

4.5

Choosing relative stability in MIPO

19

5

Biomechanical considerations in preoperative planning

19

6

Common errors

20

7

Summary

20

8

Suggested reading

21

8

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Authors

2 1

Kok-Sun KHONG, Ramakrishna KOTLANKA, Dhanjoo N GHISTA

Mechanobiology Introduction

Current thinking in fracture fi xation is moving toward a symbiotic link between biology and mechanics, rather than regarding them as separate entities in the healing process of fractured bones. The purpose of this chapter is to instruct the trauma surgeon in approaching fracture fi xation in a way that maximizes healing potential such that both biology and mechanics become force-multipliers of each other. This new process is the application of “mechanobiology” and should become more important as less invasive surgical techniques become standard in the armamentarium of the surgeon. Mechanobiology is the embodiment of Julius Wolff’s Law, which states: “The form of a bone being given, the bone elements place or displace themselves in the direction of the functional pressure and increase or decrease their mass to reflect the amount of pressure.” The surgeon needs to understand how to influence the process of bone healing in any given fracture. It is clearly understood that careful soft-tissue handling is very important in preserving blood supply to injured bone. In addition, the outcome of reliable and predictable fracture healing can be influenced by mechanical devices sharing load in unstable fracture patterns. Hence it is important that osteosynthesis is directed at producing a mechanically friendly environment for optimal fracture healing.

2

Mechanobiology of fracture repair

2.1

Mechanical influence on the fracture repair phases

2.1.1

Phase of inflammation and tissue response

As with all tissue-repair mechanisms, the inflammatory phase is mandatory, so that chemotactic factors and cytokines will induce host defense cells as well as highly vascularized repair granulation tissue to form around the damaged and necrotic bone ends. With high local tissue oxygen, fibrogenic tissue will proliferate to provide an initial scaffold between the fracture ends. This phase lasts from the fi rst 24–48 hours of injury into the fi rst week. Granulation tissue can tolerate 100% strain and mechanics do not seem to play a major role during this phase, but surgery should not devascularize this repair tissue. Here lies the main reason for minimally invasive procedures. Medullary blood supply to the diaphysis is important for bone healing, and intramedullary nailing disrupts this source. Periosteal blood flow alone cannot reach the endosteum and endosteal callus may be inhibited. Plate fi xation preserves the medullary and metaphyseal vessels as well as periosteal vessels on the opposite side of the “footprint” caused by the plate. The internal fi xator aims to preserve blood flow under the plate by reduced contact with the bone. 2.1.2

Phase of intramembranous and endochondral ossification

Under conditions of low oxygen as the inflammatory phase passes, hyaline and fibrocartilage differentiation will occur. This process begins within 48 hours after injury and may peak at 9–14 days, depending on the tissue condition. It also follows the peak fracture blood flow at 2 weeks. Osteogenic factors then cause further differentiation of chondroid tissue into bone, much in the way as an ossification center forms during normal growth. Intramembranous ossification occurs as hard 9

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fracture callus further from the fracture site, while endochondral ossification occurs as soft callus around the fracture ends. Mechanical stability allows metaplasia of cartilage to bone. If excessive motion is applied to the bone ends there will be increased vascularity and fibrogenic tissue will persist, resulting in nonunion. Goodship and Kenwright, however, demonstrated that bony enhancement with interfragmentary motion in the order of 500 μm and artificial micromovement during the fi rst month of treatment resulted in significantly shorter healing time. Flexible fi xation promotes micromotion, which produces exuberant callus clearly visible on x-rays, while rigid fi xation diminishes this. Herein lies the relevance of mechanobiology to osteosynthesis. 2.1.3

Phase of fracture consolidation

When tissue strain is below 2%, all calcified cartilage will become bone provided there are adequate osteogenic factors. This process is easily monitored by x-rays, in which the fracture gap or lucency will slowly disappear with more mineralization. There is also a reduction in osteopenia (porosity) concomitant with the reduction of hypervascularity at 12 weeks. Consolidation begins as early as 6 weeks and may last up to 6 months. Strain of between 5% and 20% will result in limited ossification and persistence of fibrous tissue, leading to fibrous nonunion. Mechanically speaking, an implant should hold the fracture at least until the consolidation phase is complete. 2.1.4

Phase of bone remodeling

Further maturation of bone includes the realignment of the 3-D helical bone structure with lines of stress applied to the bone according to Wolff’s Law. This fi nal process of fracture healing begins at about 3 months and may take up to a year to complete. Cancellous bone consolidates and remodels only to the trabecular phase, which takes about half the time of cortical bone that must remodel into a complex Haversian structure through a

slower process. Implants can be safely removed once the remodeling process is evident on x-rays showing corticomedullary differentiation (recanalization) at the site of fracture. 2.2

Biomechanics of fracture callus

Fracture callus of mineralized cartilage forms between bone ends and is called gap callus; along the medullary cavity (medullary callus) and on the outer cortex (periosteal callus) (Fig 2-1). The importance of callus is to provide initial stiffness at the fracture ends so that osteogenesis can occur. The stiffness generated must resist bending and torsional forces. This stiffness is minimal in the early phase and fracture immobilization or internal fi xation is thus employed. If absolute stability is provided by implants, there is no stimulation for the callus process, and direct healing takes place, ie, gap callus healing. In this case, the consolidation process is essentially bypassed by going straight into the remodeling phase. In indirect fracture healing, the weakest callus is gap callus generated between well-reduced fracture ends. As shown in Fig 2-1a–b, medullary callus provides some resistance to bending forces, but it is periosteal or extracortical callus that is most effective in providing the bending and torsional resistance (Fig 2-1c–d). Mechanically speaking, a collar of fracture callus is good, and indicates succesfull indirect healing and should not be regarded as a failure of osteosynthesis.

With intramedullary devices, one is able to see large extracortical callus, while medullary callus is minimal owing to the presence of the nail (Fig 2-2a, Fig 2-3a). With plate osteosynthesis, there is abundant medullary callus. Periosteal callus also forms on the side opposite to the plate, especially on the compression side of the bone (Fig 2-2b, Fig 2-3b).

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2

Mechanobiology

a

b

a

Callus in endosteum

b Fig 2-2a–b a

Callus formation with implants.

The presence of the nail inhibits callus formation in the endosteum.

b c

Periosteal callus is formed on the side opposite to the plate.

Callus in periosteum

a d

Fig 2-1a–d

Callus in both periosteum and endosteum

Callus formation in fractured bones provides bending

rigidity. Abundant callus formation increases bending rigidity.

b Fig 2-3a–b

Canine tibial fracture; callus formation in relation to

implants. a

Note the minimal presence of medullary callus in nailed bone showing abundant periosteal callus at 42, 90, and 120 days (left to right).

b

More medullary callus has formed in fractures which were plated at 42 and 90 days, and which has remodelled after 120 days (left to right).

11

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2.3

Stability in fracture healing

2.3.1

Absolute stability

Absolute stability means absence of motion at fracture site, resulting in nonappearance of fracture callus, especially when the fracture ends are highly compressed without gap. Should there be failure or delay in union, cyclical fatigue of the implant may occur from functional loading of the limb. Fatigue failure may occur at points of weakness within the device such as a screw hole. It is imperative that during the healing process the period of high stress in an implant is kept short, especially in slow healing cortical bone. In cancellous bone, healing occurs at twice the rate of cortical bone so that the implant does not fail from fatigue but may fail from loosening because of differential stiffness between implant and bone, especially in osteoporotic bone.

2.3.2

Relative stability

Relative stability encourages the formation of fracture callus. It is a partnership between an artificial implant and callus. The increasing stiffness and strength of fracture callus unloads stress from the implant, thereby protecting it from failure. In the clinical setting, this is most desirable in diaphyseal fractures. In the application of Wolff’s Law to fracture mechanobiology it may even be more beneficial to have flexible plating, so as to stimulate extracortical callus (Fig 2-4, Fig 2-5). Plates have been thought of as “stress-protecting,” but may also function as “stress-sharing” implants.

Future implants may have built-in variable stiffness.

a

b Fig 2-4a–b a

Plate rigidity and healing type.

Fracture fi xation with a less rigid plate; a fracture gap is still

a

b

c

visible after 7 weeks. The fragment ends have resorbed, and b

periosteal callus has formed.

Fig 2-5a–c

Using a more rigid plate; the fracture has remodelled and less

with solid callus where gap strain is small. No bone grafting was

periosteal callus is present.

performed in this case.

Principle of leaving large fracture gaps which rapidly fill

12

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2

Mechanobiology

Absolute and relative stability can be combined in a single bone, as in an intraarticular fracture with metaphyseal and diaphyseal extension. The articular joint block is rigidly fi xed with lag screws and no gap strain, while the metaphyseal and shaft parts are less rigidly fi xed with fewer screws in a long plate (Fig 2-6).

3

3.1

butterfly bone fragment. However, it may not make a significant difference to the overall fi xation stability. The stress in the plate, screws, and bone is dependent on the fracture gap. Stress in the plate and screws at the fracture site will be higher when the fracture gap is big than when the fracture gap is small. Great care should thus be taken to minimize fatigue and wear of plates and screws in MIPO.

The application of gap strain theory

Fracture gap strain

The surfaces of fractured bone fragments are irregular and exact apposition between bone fragments as well as stability may be difficult to achieve. Interfragmentary strain theory— also called “gap strain theory” by Perren—explains different types of tissue formation based on the strain at the fracture gap. If the fracture gap is very small, then for an applied load at the fracture site, the strain (elongation/gap width) is large. Thus granulation tissue—which can accommodate 100% strain—is formed at a small fracture gap. For similar loading, a larger fracture gap permits cartilage formation, as the strain is smaller. This may be a reason for fracture ends to resorb naturally, thereby forming a larger initial gap. Fibrogenic tissue contributes to a reduction in strain at the fracture site. This further diminishes interfragmentary strain and will allow cartilage and eventual bone formation. Interfragmentary strain theory implies that a larger gap may be more conducive to bone formation than a smaller gap.

While end-to-end bony apposition is advocated, side-to-side gaps need not be closed, allowing micromotion to establish callus between the butterfly and the main shaft fragments (Fig 2-5). Interfragmentary compression of these fragments increases gap strain unfavorably and may also devitalize the

a Fig 2-6a–c

b

c

Combination of absolute stability at the joint block

and relative stability at the diaphysis in a complex fracture configuration.

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3.2

Osteosynthesis with plate fixation

Irrespective of the type of fracture fi xation, the main purpose of using a fracture implant is as follows: Transfer the loads (tension, bending, and torsion) from one end of a broken bone to another. Provide initial stable fi xation with a compressive strain of the order of not more than 2% at the fractured site to promote bone healing. Allow as much of the surrounding bone to be stressed under normal loading during the healing process, so as to prevent “disuse” osteoporosis of the bone. The factors governing the success of fracture healing are: The degree of contact between the bone fragments Alignment of the bone fragments Controlled micromovement at the fracture site Good blood supply at the fracture site Other parameters such as age, health, and nutritional status of the patient Nonoccurrence of implant failure

Problems with plate fi xation include: Loosening of screws Local effects on vascularity of the cortex beneath the plate Implant failure from quality issues Too much or too little hardware

4

4.1

Mechanobiology in fracture fixation

Important aspects of the plate

The major factors affecting the bone–plate fi xation are (Fig 2-7): Geometry and material of plate Placement of plate relative to loading forces Bone–screw interface Induction of compressive stress between bone fragments Quality of bone Surface area of bone–plate interface Type, number, direction, and location of screws Based on these factors, a surgeon can decide whether to achieve rigid fi xation or flexible fi xation.

6

Fig 2-7

1

7

2 4 Factors affecting the bone–plate fi xation:

3

5

1

Geometry and material of plate

5

Quality of bone

2

Placement of plate relative to loading forces

6

Surface area of bone–plate interface

3

Bone–screw interface

7

Type, number, direction, and location of screws

4

Induction of compressive stress between bone fragments

14

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2

Mechanobiology

Although the nature of in vivo loading is complex, it can be broadly categorized as axial (compression and tension), bending, and torsion. Bending alone is considered in most studies on fracture fi xation, because bending will induce both tension and compression stress in the bone, and tend to open the fracture gap, leading to instability of the fracture fi xation. Bending moment is caused by eccentric forces on long curved bones and by antagonistic muscle action during movement at the joints. The role of the plate is to absorb the tensile forces at the fracture while compressive forces are generated at the surface opposite to the surface under tension. Significant torsional forces are added to bending forces, especially in the femur and humerus.

screw is designed to lock into the plate and this internal fi xator acts as a single construct. Bending or contouring the plate causes divergence or convergence of adjacent screws, which then improve the bone-holding power by resisting screw pullout.

A weak portion of the plate, eg, an unfi lled screw hole, should not be placed exactly over the fracture gap so as to avoid “stressriser” plate failure.

With more screws, the fi xation is more rigid and there is less tendency of failure due to screw pull-out.

4.2

Important aspects of screws

4.2.1

Screw design

The bone screw is a critical implant–bone interface and its design has been studied extensively. Standard screws are essentially of two types—the cortex screw and the cancellous bone screw—to accommodate the type of bone and the required holding power. The theory of thread shape factor (TSF) has been outlined by Chapman and depends on the variables shown in Fig 2-8 . It is assumed that these data are constant when analyzing plate function, but it is clear that screw integrity varies with many factors such as bone quality, screw design, insertion technique, and even thermal necrosis and resorption of bone associated with drilling. The use of sharp drill bits and fluid irrigation reduce thermal effects on drill holes. With fewer screws used in MIPO, every screw should be placed with greater attention to technique. A new third type of screw is the locking head screw (LHS) (Fig 2-12b) in which the TSF does not determine bone-holding power because the

4.2.2

Number of screws in a plate

In plate fi xation using the tension band technique, the screw farthest from the fracture site is loaded more than the screws near the fracture site during bending. Keeping the length of the plate constant, with the increase in number of screws there is a decrease in the magnitude of load on each screw (Fig 2-9).

However, more screws weaken the bone. Hence we need to strike a balance with the appropriate number of screws. Stoffel found that there is no significant improvement in fracture fi xation with a 12-hole locking compression plate (LCP) beyond three screws on either side of a fracture against bending, and four screws per fragment against torsion.

Length

Pitch

Core diameter Thread diameter

Fig 2-8

Different variables defining the screw design.

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4.2.3

Influence of screw placement relative to the fracture site

The screws enable the plate to conform to the bone surface. Minimizing the distance between the nearest screws on either side of the bone fragments (also called working length) increases stiffness at the fracture (ie, reducing gap motion) (Fig | Anim 2-10a). The plate stress within this short working length is also higher. When the innermost screws are further away from the fracture site, the working length of the plate is greater, allowing bone deformation and gap opening (Fig | Anim 2-10b), but there is better stress distribution in the plate. The farthest screws determine the effective usage of plate length and contribute to fracture gap stability (Fig 2-10c–d).

a

b

c Fig 2-9a–c

More screws in one plate decrease the magnitude of

force (red arrows) in each screw and therefore reduce the risk of pull-out. Working length Animation

c

a

Effective usage of plate length Working length

b

d

Fig | Anim 2-10a–d

Effective usage of plate length

Influence of screw placement relative to the

fracture site. a

Minimizing the distance between the nearest screws on either side of the bone fragments (also called working length)

c–d The farthest screws determine the effective usage of plate length and contribute to fracture gap stability.

increases stiffness at the fracture (ie, reducing gap motion). b

Therefore, the stress within the longer working plate length is lower.

16

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2

Mechanobiology

Long plates not only help in overall fracture stability, but also reduce internal plate stress with less likelihood of fatigue failure (Fig | Anim 2-11). Analysis of the influence of the distance between the screws and the location of the nearest screws from the fracture site on the forces in the screws and the fracture gap have confi rmed this. It is also important to balance the spacing between the screws with respect to overall plate length on either side of the fracture. Differential stiffness may lead to one-sided fi xation failure, especially in the softer metaphyseal bone.

For plates extending from diaphysis to epiphysis, fewer screws are required in the former and more screws needed in the latter to achieve stiffness-balanced fi xation. 4.3

Bone–plate interface

High frictional compressive forces will develop between conventional plates and the bone due to tightening of screws (Fig 2-12a). This frictional force prevents the sliding motion

Animation

a

b

Fig | Anim 2-11a–b

Stress variation on a long plate due to the distance between screws.

b

a Fig 2-12a–b a

Typical force distribution of a plate osteosynthesis without

b

Typical force distribution of a locking internal fixator (LIF)

angular stability: The screw tightening moment leads to surface

osteosynthesis with angular stability: This configuration is

pressure between the plate and bone. The friction thus created

statically secure with only monocortical fixation since the so-

in the plate–bone contact zone stabilizes the bone fragment in

called locking head screw (LHS) is anchored in a mechanically

relation to the load carrier. This system only becomes statically

stable manner in the load carrier, perpendicular to the plate

secure after bicortical screw fixation.

body. Such systems act more like fixators than plates.

17

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between plate and bone during loading and helps to reduce shear forces on screws at the bone–plate interface. However, compressive forces will damage the blood supply in the bone underneath the plate. The bone underneath the plate may become weakened due to temporary porosity resulting from internal remodeling. The factors affecting the amount of friction are the surface roughness of the plate and compressive force applied during tightening of the screws.

bending, the helical plate protects the fracture by not allowing the callus to be under tension, while away from the fracture site the helical plate allows the bone to bear both tensile and compressive stress generated due to bending (Fig 2-14b). Thus, the bone away from fracture is not shielded from stress due to the helical shape of the plate. Under axial loading, the fracture gap closure is quite uniform, unlike that with the conventional straight plate (Fig 2-14c).

The LCP (Fig 2-12b) avoids damage to the periosteum as the plate stands off from bone. Force transfer is purely through screws and not by contact between plate and bone. The periosteum can be preserved and cortex thinning is reduced. However, shear forces at the bone–screw and screw–plate interfaces are high. With titanium versions, interdigitation may occur between screw head and the hole. Removal of the implant may then be very difficult or even impossible.

However, in all loading conditions the helical plate is highly stressed at the screw holes near the fracture site. The screws nearest to the fracture site are concomitantly high loaded compared with the other screws in compression and torsion, while in the case of bending, stress is distributed more toward

4.4

Helical plating

The concept of a helical plate was fi rst introduced by Fernandez. In this idea one has the freedom of selecting any entry point for minimally invasive surgery (MIS). In addition to the biomechanical properties discussed in detail below, this plate offers distinct clinical advantage; for instance helical contouring takes into account the anatomy of the humerus with respect to the radial nerve (Fig 2-13). We have studied the efficacy of a 180º helical plate by using fi nite element method (FEM) analysis on long bones subjected to torsional, bending, and axial loads (Fig 2-14). In the FEM analysis, the helical plate was more effective in bearing the tensile force (diagonal to the bone axis) generated during torsional loading thus providing good stability at the fracture site. During torsion, the bone is weakest in tension and a helical plate protects the bone in the same direction (Fig 2-14a). In

a Fig 2-13a–b

b The helical contouring of this plate takes into account

the anatomy of the humerus with respect to the radial nerve.

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2

Mechanobiology

the farther screws. Hence, in general helical plates will provide good fracture stability in torsion and reasonable stability in bending, while reducing stress shielding of the bone.

a

4.5

Choosing relative stability in MIPO

Relative stability is more appropriate for MIPO, especially in the comminuted diaphysis. Relative stability is all about providing sufficient stability at the fracture site to the extent that postoperative mobilization of the extremity is possible and flexible enough to allow some micromotion at fracture site, so as to promote rapid and reliable bone healing by formation of callus. In other words, the surgeon does not need to rely on the plate for a prolonged period, with the added advantage that the effects of cortical necrosis and stress shielding are reduced. Another advantage of relative stability is that accurate apposition of the fragments is not necessary and external callus is expected to bridge the fracture gap given the correct mechanobiological situation. Blood supply to the bone is also less disturbed by avoiding exposure of fracture site.

b

5

c Low stress High stress

Fig 2-14a–c

During torsion, the bone is weakest in tension and a helical plate protects the bone in the same direction.

b

In bending, the helical plate allows the bone to bear both tensile and compressive stress.

c

When there is indication for osteosynthesis of a fracture, the fi rst decision to make is whether absolute or relative stability is desired. This is critical especially when dealing with complex and segmental fractures involving the joint, metaphysis, and diaphysis.

Efficacy of a helical plate with regard to torsional (a)

bending (b), and axial (c) loads. a

Biomechanical considerations in preoperative planning

Under axial loading, the fracture gap closure is quite uniform, unlike that of the conventional straight plate.

Absolute stability is best indicated in articular fractures and can be achieved by interfragmentary compression using the appropriate lag screw technique. Added stability can be achieved by buttress plating to prevent shear forces during joint motion or loading. Simple shaft fractures may also be treated by absolute stability, but require direct reduction, as in the forearm.

19

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Relative stability is best applied to multifragmentary fractures, especially in the metaphysis and diaphysis. For relative stability, it is important to select the appropriate plate in terms of shape and strength. It is important that the shape conforms to the anatomical surface so that implant and bone can act as a single construct. Strength is critical to prevent premature implant failure, as in these situations the shared support expected from bone may be inadequate in the early period of healing. In general broad plates 4.5 (with 4.5 mm screws) are used in the femur, narrow plates 4.5 in the humerus and tibia, and plates with 3.5 mm screws in the radius and ulna or fibula. The implant should be placed so as to provide balanced stability on both sides of the fracture gap. If one fragment is more rigidly fi xed to the plate, it will have a higher stiffness than the other fragment, thus causing higher motion amplitude to occur in the fracture gap. If the other fragment is not as rigidly “captured” by the implant, then stress at the screw– bone interface will result in loosening of the unlocked screws. This is an important concept in locked screw–plate systems, which should not have all locked screws in the epi-/metaphysis while having none in the diaphysis.

6

Common errors

MIS has often been equated with an arbitrarily small number of screws as well as the length of the incisions. The reality is that the exposure is just sufficient to insert the plate and target the desired screw holes. The fracture itself should not be exposed, but reduced by indirect methods, with the option of a “mini-open” incision to directly manipulate the displaced fracture fragment where indirect means fail.

Common errors: Filling in as many screws as possible, causing excessive stiffness. Using too short a plate; the plate should span from one metaphysis to the other. Using extremely long plates on curved bones; either the proximal or distal screws may miss engaging the bone. Not centering the plate with respect to the fracture site, ie, having one limb longer than the other. Leaving a single unfi lled screw hole opposite a small bone defect. Using LHS on one side of the fracture and standard screws on the other side in an LCP.

7

Summary

Every surgeon should know the biology of fracture healing so as to anticipate the outcome of planned treatment. The timing and method of intervention are crucial if one respects the important role of soft tissue in bone healing. Damage to tissues in the injury zone will be the major factor for the occurrence of complications such as bone devitalization, infection, delayed union, and nonunion. Mechanobiology will play a key role in fracture surgery as MIS approaches are developed. With MIPO techniques, fracture apposition may be limited to achieving axial and rotational alignment and maintenance of bone length. With fracture comminution or bone loss, the choice of implant will be of utmost importance if secondary surgery such as bone grafting and replating are to be avoided. A good surgeon can actually dial-in the amount of stability required so as to manipulate a desired fracture healing pattern. In future, preoperative planning will likely be performed using parametric mechanical data instead of images.

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2

Mechanobiology

Angular stable implants may become standard as angular stability provides a way to control and limit excessive interfragmentary motion. However, stress will increase within the implant and failure can still occur. As with all trauma surgery, proper knowledge and training, preoperative planning, technically well-executed surgery, comprehensive rehabilitation, and timely follow-up will result in a predictably good outcome even in the most difficult of fractures.

Perren SM (1979) Physical and biological aspects of fracture healing with special reference to internal fi xation. Clin Orthop Relat Res; Jan–Feb(138):175–196. Rand JA, An KN, Chao EY, et al (1981) A comparison of the effect of open intramedullary nailing and compression-plate fi xation on fracture site blood flow and fracture union. J Bone Joint Surg [Am]; 63(3):427–442. Stoffel K, Dieter U, Stachowiak G, et al (2003) Biomechanical testing of the LCP—how can stability in locked internal fi xators be controlled? Injury; 34 Suppl 2:11–19.

8

Suggested reading

Albright JA, Johnson TR, Saha S (1978) Principles of internal fi xation. Ghista DN, Roof R (eds), Orthopaedic Mechanics: Procedures and Devices. London: Academic Press, 123–229. Chapman JR, Harrington RM, Lee KM, et al (1996) Factors affecting the pullout strength of cancellous bone screws. J Biomech Eng; 118:391–398. Day SM, Ostrum RF, Chao YS, et al (2000) Bone injury, regeneration and repair. Buckwalter JA, Einhorn TA, Simon SR (eds) Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, 2nd ed. Illinois: American Academy of Orthopaedic Surgeons. Fernandez Dell’Oca AA (2002) The principle of helical implants: Unusual ideas worth considering. Injury; 33 Suppl 1:SA1–27. Review. Goodship AE, Kenwright J (1985) The influence of induced micromovement upon the healing of experimental tibial fractures. J Bone Joint Surg [Br.]; 67(4): 650–655. John AH, Edward JC, Wilson CH (1992) Biomechanics of fractures. Browner BD, Jupiter JB, Levine AM, Trafton PG (eds), Skeletal Trauma: Fractures, Dislocations, Ligamentous Injuries. Philadephia: Saunders, 95–125. Johnson KD, Tencer AF (1994) Biomechanics in Orthopaedic Trauma. Bone Fracture and Fixation. London: Martin Dunitz. Laurence M, Freeman MA, Swanson SA (1969) Engineering considerations in the internal fi xation of fractures of the tibial shaft. J Bone Joint Surg [Br]; 51(4):754–768.

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3

Instruments

1

Introduction

23

2

Instruments to aid fracture reduction

23

2.1

Reduction handles

23

2.2

External fixators

25

2.3

Large distractor

25

2.4

Collinear reduction clamps

25

2.5

Periarticular reduction forceps

25

3

Instruments to aid plate insertion and fixation 26

3.1

Tunneler

26

3.2

Soft tissue retractor

26

3.3

Plate holder

26

3.4

Plate pusher

28

3.5

Sleeves to aid percutaneous screw fixation

28

3.6

Tension device

30

4

Instruments for plate removal

31

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Author

3 1

Suthorn BAVONRATANAVECH

Instruments Creation of a submuscular, extraperiosteal tunnel for the plate Introduction of the plate Fixation of the two ends of the plate through the original incisions Checking the quality of reduction, length, axial alignment, and rotation Completion of the fi xation with screws introduced through stab incisions making adjustments to the fracture reduction if necessary Final check on fracture reduction and implant position Wound closure

Introduction

Minimally invasive plate osteosynthesis (MIPO), in contrast to conventional open reduction and internal fi xation using plates, is performed without exposure of the fracture site, the aim being to preserve biology with minimal disruption of softtissue attachments and vascular supply. In order to accomplish this, the fractures are reduced by indirect means and the implants introduced from a site remote from the fractures. To facilitate this minimally invasive method of fracture reduction and fi xation, special instruments are required. Instrument systems are still evolving but those introduced so far can be grouped according to the functions that they perform as follows: Instruments to aid fracture reduction Instruments to aid plate insertion and fi xation Instruments for plate removal Some of these instruments are commercially available, others were fabricated according to the needs of the surgeon. As MIPO evolves, instruments will be refi ned to make the procedure easier and more reproducible in the hands of most surgeons. In order to have a better understanding of the functions and applications of the various instruments, it is necessary to be familiar with the basic steps of a MIPO procedure, which is usually performed in the following sequence: Indirect fracture reduction Temporary fi xation to hold the reduction if necessary Skin incisions remote from the fracture site, corresponding to the ends of the plate, one on each side of the fracture

2

2.1

Instruments to aid fracture reduction

Reduction handles

These can be used for minimally invasive fracture reduction. As they can be used with self-drilling threaded rods or guide wires, application is easy. They can be connected with clamps and rods to function as external fi xators for temporary intraoperative fracture stabilization. Available in two different sizes for use with large and small fragment implants, they come with toothed or rounded tips. The toothed tip provides rotational stability and can be used with considerable force during fracture manipulation and reduction. The rounded tip is used with the threaded guide wire when a lower force is required during fracture reduction. When using these reduction handles, it is important to ensure that their locations would not interfere with subsequent plate application (Fig 3-1).

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a

b

Fig 3-1a–d a

Screw the self-tapping threaded rod through the drill sleeve.

b

Attach the reduction handle to the threaded rod and push close to the bone. Then tighten the adjusting screw. The second reduction handle is applied in the same way.

c c

Apply combination clamps and rod but without tightening the nuts. Reduce the fracture under fluoroscopic guidance.

d d

After completing reduction, tighten the nuts of the combination clamps to hold the fracture reduction temporarily.

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3

2.2

Instruments

External fixators

tubes are locked in position with a middle tube and two tubeto-tube clamps that have been preassembled (Fig 3-2).

The tubular external fi xator system, together with Schanz screws, can be used in the same manner as the reduction handles for indirect fracture reduction and temporary fracture fi xation. In order to reduce radiation exposure of the surgeon’s hands during the maneuvers to achieve fracture reduction, manipulation of the Schanz screws can be done through two long tubes connected to the Schanz screws by clamps. Once satisfactory fracture reduction is obtained, the ends of both

2.3

Large distractor

The function of the large distractor is essentially the same as that of the external fi xator, except that the distractor can be used to distract or compress the fracture zone by means of tightening a nut (Fig 3-3). 2.4

Collinear reduction clamps

These allow minimally invasive fracture reduction through a collinear closing mechanism with modular arms for the reduction of long-bone, pelvic, and articular fractures. Different positions of the arms are possible and they permit a continuous application of force. There are three types of modular arm: the pelvic arm, percutaneous arm, and Hohmann-style arm. These arms are cannulated to allow the insertion of K-wires (Fig 3-4). 2.5

Periarticular reduction forceps

These come with spherical tips and are useful for direct or percutaneous application to hold large articular fracture fragments (Chapter 7 Reduction technique: Fig 7-1).

a Fig 3-2a–b

b Modular external fi xator used for indirect fracture

reduction. a

Two pins are inserted in each main fragment outside the zone of injury. They are fi xed to a tube by universal clamps, and function as two handles for indirect reduction.

b

After reduction the two tubes are united by a third tube and two

Fig 3-3

tube-to-tube clamps.

stabilization.

Large distractor used for temporary intraoperative fracture

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3

3.1

Instruments to aid plate insertion and fixation

Tunneler

The tunneler is used to prepare a pathway for the introduction of the plate in a submuscular extraperiosteal plane. It consists of a handle and a blade. The handle has a vertical and a horizontal arm, the latter serving as a directional guide during the blade’s introduction. The blade is 30 cm long and marked with 5 cm graduations which serve as a guide to the length of the plate to be used. There is a hole at the tip of the blade which allows a suture to be tied to one end of the selected plate so that as the tunneler is withdrawn, it pulls the plate along with it into the tunnel created (Fig 3-5). When using the tunneler, it is important to avoid introducing it repeatedly or pushing it back and forth too many times as this will strip the periosteum and damage the soft tissue.

a

3.2

Soft-tissue retractor

The soft-tissue retractor functions as a tunneling instrument to prepare the pathway for plate insertion. It has an extendible blade which can be rotated through 180° allowing any blade angle to be selected (Fig 3-6). 3.3 b

Fig 3-4a–b

Collinear reduction clamps.

a

Reduction of the femoral shaft using the Hohmann-style arm.

b

Reduction of the femoral condyle using the percutaneous arm.

Plate holder

The plate selected for the fracture fi xation can itself be used to create the submuscular tunnel by attaching a plate holder to one end of the plate. The plate holder is also used to hold the plate for percutaneous insertion and allows optimal guidance and monitoring of the plate under the soft-tissue mantle (Fig 3-7a). It can be used with the broad and narrow limited contact dynamic compression plate (LC-DCP) and locking compresion plate (LCP).

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3

Instruments

Fig 3-6

The soft-tissue retractor with an asym-

metric extendible blade facilitates percutaneous

a

plate insertion.

a

b

c

b

Fig 3-5a–c

Fig 3-7a–b

This tunneler has a blade length of 30 cm and a hole at the tip to

a

allow insertion of a suture to pull the plate into position as it is withdrawn.

The plate holder allows optimal guidance and monitoring of the plate under the soft-tissue mantle.

b

An LCP can be introduced using a special handle with a threaded end which is screwed into the plate hole.

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In the case of the LCP a special handle with a threaded end, (Fig 3-7b) or the threaded drill guide, can also be fi xed to one end of the plate to act as a handle for plate introduction. 3.4

Plate pusher

The function of the pusher is to temporarily push the plate against the bony cortex. It has a tip similar to a cortex screw complete with a head that can fit into the plate hole and so can be used to temporarily fi x the plate to the bone after the plate has been properly positioned. It has a detachable handle (Fig 3-8). If such an instrument is not available, a standard cortex screw introduced through one cortex at one end of the plate will serve the same function.

a

b

3.5

Sleeves to aid percutaneous screw fixation

Screws can be inserted into either end of the plate through the original incisions made to insert the plate. To insert screws into the central portion of the plate, the position of the screw holes can be located by placing a plate of similar length over the skin to match the position of the inserted plate and marking the position of the screw holes on the skin. Stab incisions are then made and the underlying muscles are split with a hemostat until the plate hole is reached. In the case of an LCP, a threaded drill guide is screwed onto the threaded half of the combination hole if a locking head screw (LHS) is to be used. If a standard screw (cortex screw, cancellous bone screw) is to be inserted, a long sleeve is required to protect the soft tissue. The long 5.0/3.5 mm sleeve with a trocar from the external fi xator set can be used for this purpose. In the case of conventional plates, a special sleeve with a balltipped trocar that fits into the dynamic compression hole can be used (Fig 3-9a). The end of this special sleeve has two teeth that prevent it from slipping out of position once it sits in the plate hole. When the ball-tipped trocar, together with the special sleeve, sits correctly in the plate hole, the trocar is replaced by a drill sleeve. The hole is drilled and the drill sleeve is removed (Fig 3-9b). If desired, the depth is measured using the special, long depth gauge from the external fi xator set. A tap sleeve is inserted next. Tapping is then carried out. The tap sleeve is removed and the screw inserted through the special sleeve (Fig 3-9c).

Fig 3-8a–b a

The pusher, which has a tip similar to a cortex screw, can be used to fi x the plate onto the bone.

b

The detachable handle from the pusher can be used to fi x a Schanz screw which can then be used as a manipulator or reduction tool.

A soft-tissue spreader is also available for the minimally invasive, noninjurious insertion and removal of screws. This is a modular forceps system that consists of a handle operable with a single hand, mountable soft-tissue retractors with different blade lengths, and adapted trocars. The soft-tissue retractors

28

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3

Fig 3-9a–c

a

b

Instruments

The special sleeve for percutaneous insertion of standard screws in conventional plates—the steps in its application:

Step 1: After a stab incision is made, the outer sleeve

fi t into the plate hole. Once the plate hole is identi-

with the trocar is passed through the muscle layer.

fied, the outer sleeve fi ts into the plate hole with its

The trocar has a ball tip that has been designed to

teeth at the tip. The trocar is then removed.

Step 2–3: The drill sleeve is inserted next through

c

Step 4: After drilling and tapping, the screw is in-

the outer sleeve and removed after drilling. The tap

serted through the sleeve with a screwdriver and

sleeve is then inserted through the outer sleeve and

screwed into the plate hole.

removed after tapping. It is necessary to have a long tap in order to pass through the sleeve.

29

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together with the trocar are inserted through a small incision made over the selected plate hole. Once the trocar locates the plate hole, the retractors are spread open and the trocar removed to expose the plate hole.

3.6

Tension device

The tension device can be used either as a lengthener or a compressor depending on the direction of its hook in relation to the end of the plate (Fig 3-10). Another method to gain length is to use a spreader between the end of the plate and a screw inserted a short distance away, the so-called “push–pull” technique (Fig 3-11).

Animation

a Fig | Anim 3-10a–c a

b

c

Use of the tension device with a condylar plate.

Introduction of the condylar plate 95º, insertion of screw proximally, and temporary monocortical screw fi xation distally to push the plate to the bone.

b

Use of the tension device to distract the fracture and to allow fracture reduction proximally. The monocortically fi xed distal screw must be removed before distraction can take place.

c

Use of the tension device for interfragmentary compression once the fracture has been reduced.

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3

Instruments

a

b

Fig 3-11a–b a

Push–pull technique.

The bone spreader, placed between the end of a plate and an

b

Thereafter, and using the same independent screw, axial com-

independent screw, can be used to distract the fracture. Care

pression can be obtained by pulling the plate end toward the

should be taken to minimize soft-tissue stripping when applying

screw with a small Verbrugge forceps.

the bone holding forceps.

4

Instruments for plate removal

Plate removal is not performed routinely but, when indicated, can be removed by minimally invasive means. A MIPO chisel is available for callus removal (Fig 3-12).

conical extraction screw with a left-handed thread is available that can be inserted into the screw head using a T-handle with quick coupling and loosening the LHS by turning the conical extraction screw in an anticlockwise direction.

To remove an LCP that has been fi xed with LHS, it is necessary to fi rst unlock all the screws before removing them defi nitively in a second step; otherwise the plate may rotate while the last screw is being removed, resulting in damage to the surrounding soft tissue. A screwdriver is used to remove the screws. However, this is not always possible if the recess of the LHS is damaged or the screw is stuck in the plate. Under such circumstances, a

Fig 3-12

Chisel for callus and plate removal.

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4

Implants

1

Introduction

33

2

Internal fixators

33

3

Conventional plates and standard screws

37

4

Bridging plates

38

5

Implants for MIPO

38

6

Guidelines for use of implants for MIPO

38

6.1

Locking compression plates—LCP

38

6.2

Conventional plates—DCP and LC-DCP

41

6.3

Fixed angle implants

41

6.4

Indications for insertion of locking head screws in an LCP

6.5

41

Indications for insertion of standard screws in an LCP

42

7

Choice of implants for different bone segments 42

7.1

Diaphyseal fractures

42

7.2

Metaphyseal fractures

43

7.3

Articular fractures with extension into the

8

metaphysis/diaphysis

44

Suggested reading

45

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Author

4 1

Frankie KL LEUNG

Implants Introduction

2

Minimally invasive plate osteosynthesis (MIPO) is a modern concept of fracture fi xation, the aim of which is to preserve biology at the fracture site so as to maximize the healing potential of the injured bone and soft tissue, and facilitate rapid pain-free recovery of function. This can best be achieved by carrying out the procedure without exposure of the fracture and by introducing the plate in a submuscular, extraperiosteal position with minimal disturbance to the vascularity of the bony fragments.

a

Internal fixators

The introduction of the internal fi xator has made MIPO a more practical proposition and widened its scope and range of applications. The internal fi xator is in essence a subcutaneously or submuscularly positioned external fi xator. The unique design feature of the internal fi xator is the locking head screw (LHS)—the screw head has a double conical thread for secure fi xation into a corresponding conical thread in the plate hole. This feature imparts a degree of angular stability to the construct, as the locked screw head can no longer toggle in the plate hole. Also, because the screw head is locked in the plate hole, it does not press the plate against the underlying bone as the screw is tightened, unlike standard screws such as cortex or cancellous bone screws (Fig 4-1).

b

Fig 4-1a–b a

No angular stability with standard screws. As there is no stable connection between the screw head and the screw hole, individual screws can toggle within their screw holes, resulting in loosening and failure of fi xation.

b

Angular stability with locking head screws (LHS). The conical and threaded hole in the internal fi xator provides angular stability due to rigid connection with the threaded head of the LHS.

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The internal fi xator thus possesses features that make it suitable for MIPO. These include: LHS which prevent the plate from being pressed against the underlying bone, thus sparing the periosteal blood supply. Since the bone is not pulled against the plate by the LHS as the screws are tightened, there is no loss of primary reduction if the fracture has already been reduced.

Consequently, accurate contouring of the plate is not necessary, a defi nite advantage in MIPO as the bone is not exposed for templating. Angular stability of the construct also prevents secondary loss of reduction of the fracture when placed under load. As the LHS are either self-drilling and self-tapping or only self-tapping, screw application is made easier in the MIPO setting as drilling and/or tapping is no longer required as is the case with the application of standard screws. The fi rst internal fi xator specifically designed for use in MIPO was the less invasive stabilization system (LISS) for the distal femur (Fig 4-2). As the advantages of the LISS became apparent, demand for a more versatile system increased, and this led to the development of the locking compression plate (LCP) with a specially designed combination hole, one half of which is designed as a dynamic compression unit that allows the use of standard screws for interfragmentary or axial compression, while the other half is threaded to allow the application of LHS. Thus the LCP can function as a compression plate or as an internal fi xator when only LHS are used (Fig | Anim 4-3).

a Fig 4-2a–b

b Femoral fracture stabilized with a LISS for the distal

femur, 6 weeks postoperatively; AP (a) and lateral (b) views.

In theory, no contouring of the LCP is necessary when used as an internal fi xator, but in practice, some degree of contouring is usually needed, especially in the epi-metaphyseal segments of the bone. Otherwise the plate may stand proud and become prominent subcutaneously or cause irritation of the adjacent soft tissue. To overcome this problem, specially designed metaphyseal plates were introduced. The special features of this plate are that the juxta-articular end of the plate is thinned out to facilitate contouring and the two distal holes in this thinned area of the plate are angled at 11˚ toward the center of

34

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4

Implants

the plate to allow optimal application of the LHS in the epiphyseal area in order to avoid penetration of the articular surface. A further refi nement of this is the development of anatomically preshaped LCP for use in specific epi-metaphyseal parts of the skeleton. The metaphyseal end of such a plate allows the insertion of a cluster of LHS in a divergent or convergent manner to improve their pull-out strength. Further, no contouring of the plate is usually needed. An added advan-

tage of these anatomical preshaped LCP is that they can be used as an aid for indirect fracture reduction when used with standard screws. These can draw the bone toward the plate and thus effect an adaptation of the bony fragments to the shape of the plate. Examples of anatomically preshaped LCP are the locking proximal humerus plate (LPHP), LCP distal humerus, LCP distal radius, LCP distal femur, LCP proximal lateral tibia, and LCP distal tibia (Fig 4-4).

Animation

a

b

Fig | Anim 4-3a–c

c

LCP combination hole consists of two parts:

One half of the hole has the design of the dynamic compression unit for standard screws. The other half is conical and threaded to accept the matching thread of the locking head screw (LHS) in order to provide angular stability.

35

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a

b

c

e Fig 4-4a–e a

d

Examples of anatomically preshaped plates include:

LCP distal femur.

b

LCP proximal lateral tibia.

c

LCP distal tibia.

d

Locking proximal humeral plate (LPHP).

e

LCP distal radius.

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4

3

Implants

Conventional plates and standard screws

Although locking compression plates are eminently suited for MIPO, it is also possible to perform MIPO with conventional plates using standard screws. Conventional plates such as the dynamic compression plate (DCP) (Fig 4-5) and limited contact dynamic compression plate (LC-DCP) (Fig 4-6) can be used, and also fi xed angle implants such as condylar plates 95° or dynamic condylar screws (DCS) (Fig 4-7). When using these conventional implants for MIPO, special precautions must be taken to ensure their successful application.

Fig 4-6

The LC-DCP with its structured undersurface for limited

contact between plate and bone and an even distribution of the holes throughout the plate.

a 1

b

c

Fig 4-5a–e

d

Dynamic compression principle.

e

e

The horizontal movement of the head, as it im-

a

The holes of the plate are shaped like an inclined and transverse cylinder.

pacts against the angled side of the hole, results in

b

Like a ball, the screw head slides down the inclined cylinder.

movement of the plate and the fracture fragment

c–d Since the screw head is fi xed to the bone via the screw hole, it can only move vertically, in relation to the bone.

already attached to the plate by the first screw (1). This leads to compression of the fracture.

37

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5

Implants for MIPO

Broadly speaking, MIPO can be performed with the following types of implants: Locking plates, eg, LCP and LISS Conventional plates, eg, straight plates, such as DCP and LC-DCP, and fi xed angle implants, such as condylar plates 95º or DCS

6

a

b

Fig 4-7a–b a b

4

MIPO in proximal femur using a condylar plate 95°. MIPO in distal femur using a DCS.

Bridging plates

Irrespective of whether a locking compression or a conventional plate is used in MIPO, the plate is generally applied in the bridging mode, especially when used for complex fractures. This requires relatively long plates, and stress concentration within the plate should be avoided by placing the screws one or two screw holes away from the fracture zone and spacing out the rest of the screws within the plate. This mode of fracture fi xation provides relative stability and imparts upon the construct a certain degree of flexibility. This promotes fracture healing by callus formation, which in effect is faster and more reliable than primary bone healing. This is particularly important when dealing with multifragmentary fractures.

Guidelines for use of implants for MIPO

The following are some general guidelines when using these implants for MIPO: 6.1

Locking compression plates—LCP

Whenever possible, the fracture is fi rst reduced by indirect methods. If necessary, the reduction is then maintained using distractors or external fi xators. If a well-contoured or anatomically preshaped plate is used, the implant can be used as a reduction aid when used with standard screws (as described earlier). If the compression function of the LCP is to be used, for example in simple transverse fractures, accurate contouring of the plate is fi rst performed; axial compression can then be carried out using standard screws in the dynamic compression unit of the combination holes (Fig 4-5). It is important to note that the LCP combination holes are arranged asymmetrically on the plate. This asymmetry allows axial dynamic compression to be exerted unidirectionally. After axial compression is exerted by the standard screws, additional LHS can then be inserted (Fig 4-8).

38

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4

Implants

If it is desired to apply interfragmentary compression in simple oblique or spiral fractures, this should fi rst be accomplished using standard screws as lag screws before the application of LHS. To insert standard screws, the universal drill guide is used. The screw holes are predrilled, either neutrally or eccentrically, depending on the intended function of the screw. The depth of the screw hole is then measured and tapped, and the appropriate standard screw inserted. If contouring of the plate is necessary, it should be performed using the appropriate bending instruments. Bending should be done between the combination holes and not through the holes as this may cause deformation of the holes and result in difficulty in the subsequent insertion of LHS. One way of preventing this deformation is to insert a threaded drill sleeve or an LHS into the threaded part of the combination hole before carrying out the bending. If desired, an LCP spacer may be screwed into the plate prior to its insertion. The spacer ensures a gap of 2 mm between the plate and underlying cortex, thus minimizing plate–bone contact and preserving periosteal circulation. This spacer can be removed after insertion of the LHS.

a

Skin incisions are made, corresponding in position to the ends of the plate. A tunneler may be used to create a submuscular extraperiosteal tunnel for the plate. The plate is then passed into the tunnel. This can be done in one of several ways. If a tunneler is used, one end of the plate is tied with a suture to the end of the tunneler (Fig 4-9). As the tunneler is withdrawn, the plate is pulled into position. Another way is to fi x one end of the plate with a plate holder or a threaded LCP drill guide which is then used to guide the plate into position along the track created by the tunneler. Once the plate is in place, screw insertion can follow. If the fi rst inserted screw is an LHS, before locking, the other end of the plate should be temporarily stabilized with either a K-wire, a standard screw, a threaded LCP drill guide, or another LHS that is not locked. This is to prevent the plate from rotating (“helicopter effect”) (Fig 4-10) and causing damage to the surrounding soft tissue as the fi rst LHS is tightened and locked. The quality of fracture reduction is checked; if satisfactory, the rest of the LHS are inserted.

b

Fig 4-8a–b

Locking head screws (LHS).

a

Self-tapping.

Fig 4-9

b

Self-drilling, self-tapping.

The plate is attached to the tunneler and pulled back into position.

The tunneler is used to prepare the pathway for the plate.

39

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a

b

Fig 4-10a–b a

Tightening of the first LHS without stabilization of the other end of the plate will cause the “helicopter effect”.

b

Temporary plate stabilization of the opposite end of the plate prevents the plate rotating as the first screw is tightened and locked.

To insert a self-tapping LHS (Fig 4-8a) percutaneously, a threaded LCP drill guide is fi rst introduced through a stab incision in the skin, and then screwed into the threaded portion of the selected combination hole. The drill guide ensures that drilling is done in the correct direction so that the screw is correctly locked to achieve maximal angular stability. The screw hole is then drilled and measured (either by taking the reading from the calibrated drill bit or by using a depth gauge), and the appropriate LHS inserted, fi rst using a power tool with the screwdriver shaft and then performing the fi nal tightening by hand with the torquelimiting screwdriver until clicking occurs. Predrilling and depth measurement are not necessary if a self-drilling, self-tapping LHS is used monocortically (Fig 4-8b). This, however, is only possible in good-quality bone with a thick cortex. Monocortical screw fi xation is also indicated in periprosthetic fractures.

When using an anatomically preshaped LCP, a specially designed guiding block is available which fits into the epiphyseal end of the plate to provide easy and accurate mounting of the threaded LCP drill guide. This ensures that drilling takes place in the correct direction. After predrilling and following removal of the threaded LCP drill guide, the appropriate LHS can be inserted without removing the guiding block, to ensure that the screws are inserted in the correct direction. If necessary, a certain amount of indirect reduction of the fracture can be achieved by using a screw holding sleeve to cover the head of the LHS. When the screw is tightened, the underlying bone will be pulled toward the plate. Three well-spaced screws on each side of the fracture should provide adequate stability for fracture healing by callus. If both standard screws and LHS are used in the same construct, the standard screws should be inserted fi rst.

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4

6.2

Implants

Conventional plates—DCP and LC-DCP

Indirect fracture reduction is fi rst carried out using manual traction or with the help of a distractor or external fi xator. If necessary, the distractor or external fi xator can be used to maintain the reduction achieved. The plate itself can be used as an indirect reduction tool. In this situation the plate has to be contoured accurately to the shape of the bone. Standard screws can be used to aid fracture reduction since they pull the bone toward the plate as they are tightened (Fig 4-5). The appropriate skin incisions are made. A submuscular, extraperiosteal tunnel is created and the plate is inserted as described earlier (except that the threaded LCP drill guide cannot be used to hold the plate as in conventional plates there is no combination hole and therefore no thread). The ends of the plate are fi xed with standard screws after drilling, depth measurement, and tapping, using the appropriate sleeves for soft-tissue protection. The proximal end of the plate should preferably be fi xed fi rst, as it is easier to control the position of the distal fracture fragment by manipulation and traction. The reduction is checked after temporary monocortical screw fi xation of the distal fragment. The rest of the screws are then inserted percutaneously. Usually three screws on each side of the fracture would provide adequate stability. The screws should be well spaced and inserted obliquely to obtain a better hold in the bone. When inserting a screw into a deep-seated plate hole, it is useful to tie an absorbable suture to the screw head before screw insertion and leave the free end of the suture outside the wound. The reason for doing this is that sometimes the screw may get dislodged from the tip of the screwdriver during the process of screw insertion. If this happens, the loose screw can be retrieved with the attached suture. After the screw is fully tightened, the end of the suture outside the wound can be cut short.

Standard screws can be inserted as lag screws to enhance the stability of the fi xation. During plate contouring, the plate can be converted to a wave plate with a curved central portion directed away from the bone. This will help preserve the periosteal blood supply in the fracture zone and promote faster fracture healing with callus formation. Another advantage of the wave plate is that it helps to reduce the risk of mechanical failure of the plate as the stress is distributed over a proportionately longer section of the plate. 6.3

Fixed angle implants

Fixed angle implants such as the condylar plate 95º or the DCS can also be used in MIPO for fractures of the proximal and distal femur. Since the sagittal alignment of the condylar plate has to be determined during the insertion of the seating chisel, it is technically easier to use the DCS, as the sagittal alignment can be adjusted by rotating the condylar screw. It is also more modular in application and easier to insert via a small incision. 6.4

Indications for insertion of locking head screws in an LCP

Osteoporotic fractures Periprosthetic fractures, which are also an indication for monocortical application of self-drilling and self-tapping screws Metaphyseal and periarticular fractures

41

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6.5

Indications for insertion of standard screws in an LCP

When interfragmentary or axial dynamic compression has to be achieved. To assist fracture reduction when a standard screw is used to pull the bone fragment toward the plate. To avoid penetration of the articular surface in periarticular fractures, which may be unavoidable when fi xed angle LHS are used. In such cases, standard screws may be inserted through the dynamic compression unit of the combination hole, parallel to the articular surface.

a

7

Choice of implants for different bone segments

Once the concepts of LHS and standard screws, LCP, and conventional plates (DCP or LC-DCP) are understood, it becomes easier to decide which implant is suited for fractures in the various bone segments. 7.1

Diaphyseal fractures

Either an LCP or a conventional plate can be used. LCP with LHS is more suitable for fractures in osteoporotic bones. In femoral shaft fractures, the normal anterior bowing of the femur must be taken into consideration and the straight plate contoured accordingly (Fig 4-11). Where the end of the plate extends into the metaphyseal area, either proximally or distally, the plate has to be contoured to match the surface of the bone (Fig 4-12).

b

c

d Fig 4-11a–d a–c Sagittal curve of the femur must be considered when using a straight plate. Due to the normal anterior bowing of the femur,

Fig 4-12

When the plate has to extend to proximal or distal

metaphysis, precontouring of the plate should be done.

there is a risk of an eccentric plate position at either end. d

A special sagittally bent LCP, 16 holes is available and can be used to maintain the anterior bowing of the femur.

42

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4

7.2

Implants

Metaphyseal fractures

The metaphyseal LCP is suitable. As the plate is straight, contouring is needed. These plates have a thinner section at one end and a thicker portion at the other end. The thinner section of such plates is designed for easier contouring and will be less prone to cause soft-tissue irritation. The thicker section is designed for application in the diaphysis (Fig 4-13). If there is a risk that the distal LHS may penetrate the joint surface because of their fi xed angle, the bend of the plate may be decreased or altered or the plate may be shifted slightly away from the articular surface to avoid the problem. Alternatively, standard screws can be inserted into the dynamic compression part of the combination hole parallel to the articular surface. Where available, specially designed anatomically preshaped LCP can be used. As these plates are anatomically precontoured, no intraoperative contouring is necessary. The contour of the plate will also serve as a template for realignment of the fracture. In the case of the distal femur LISS, the surgeon must be aware that some patients have excessive anterior bowing in the sagittal plane or varus bowing in the coronal plane. It is important to predict such malalignment between the plate and the bone as this can lead either to erroneous application of the implant with eccentric anchorage of the screw in the bone, or to loss of reduction of the fracture. In the proximal and distal femur, conventional fi xed angle implants such as the condylar plate 95° or the DCS may also be used.

a Fig 4-13a–b

b Straight metaphyseal plate.

The thinner section of the metaphyseal plate is designed for easier contouring and will be less prone to cause soft-tissue irritation. The thicker section is designed for application in the diaphysis. The two sections of the plate are used with LHS with different diameters.

43

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7.3

Articular fractures with extension into the metaphysis/diaphysis

The principles of treatment of intraarticular fractures are anatomical reduction and stable fi xation with lag screws. Reduction can be achieved by arthrotomy or with the aid of an arthroscope or image intensifier. The articular block can then be fi xed to the metaphysis using minimally invasive techniques (Fig 4-14). Any of the implants described above for metaphyseal fractures can be used.

a Fig 4-14a–b

b Articular fractures.

The articular fragments are fi xed with interfragmentary lag screws while the metaphyseal fracture is stabilized with an LCP proximal tibia applied in a buttress mode.

44

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4

8

Implants

Suggested reading

Frigg R (2003) Development of the locking compression plate. Injury; 34 Suppl 2:6–10. Krettek C, Schandelmaier P, Miclau T, et al (1997) Minimally invasive percutaneous plate osteosynthesis (MIPPO) using the DCS in proximal and distal femoral fractures. Injury; 28 Suppl 1:20–30. Sommer C, Gautier E, Muller M, et al (2003) First clinical results of the locking compression plate (LCP). Injury; 34 Suppl 2:43–54. Tepic S, Perren SM (1995) The biomechanics of the PC-Fix internal fi xator. Injury; 26 Suppl 2:5–10. Wenda K, Runkel M, Degreif J, et al (1997) Minimally invasive plate fi xation in femoral shaft fractures. Injury; 28 Suppl 1:13–19.

45

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5

Intraoperative imaging

1

The role of imaging in MIPO

47

2

Hazards of radiation exposure

48

3

Safety measures

49

3.1

Protective equipment

49

3.2

Protective procedures

50

4

Portable fluoroscopy machine or C-arm

51

4.1

The machine

51

4.2

Imaging modes

52

4.3

Memory modules

52

4.4

Printer

53

4.5

3-D models

53

5

Requirements and set-up in the OR

53

5.1

Positioning

53

5.2

Obtaining maximum image

53

5.3

Obtaining imaging in the correct orientation

53

5.4

Specific positioning for MIPO procedures

54

6

Conclusion

54

7

Suggested reading

55

46

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Authors

5 1

Kok-Sun KHONG, Fareed KAGDA

Intraoperative imaging The role of imaging in MIPO

In minimally invasive plate osteosynthesis (MIPO), x-ray imaging is not only an essential requirement for preoperative diagnosis and planning but an integral part of the surgical procedure itself. With limited windows through the skin and no direct visualization of the fragments intraoperatively, image intensifiers become a key surgical tool in MIPO. However, as with any surgical equipment, the risks, benefits, and limitations must be thoroughly appreciated. Though modern plain x-rays have minimal radiation effects on the patient, frequent, prolonged, and repetitive use of intraoperative image intensifiers have greatly increased the amount of radiation exposure to the surgeon and team in the

a

Fig 5-1a–b

operating room (OR) including the anesthetist, the surgical assistants, nurses, and attendants (Fig 5-1). It is thus essential for a surgeon who practices MIPO to understand the type of x-ray generated in his or her institution, whether conventional or digital, the type of magnification exercised on the x-rays, and the size and type of image intensifier used in the OR. This will allow maximum benefit with a minimum of danger to everyone involved. ALARA—“as low as reasonably achievable”—is the principle of radiation exposure put forth by the National Committee on Radiation Protection in 1954. In practice this means keeping occupational and nonoccupational absorbed dose equivalents well below maximum allowed levels through proper safety procedures and avoiding unnecessary exposures.

b

Scatter radiation is produced by x-rays being deflected by patient anatomy, particularly bone. The amount and proportion of

“nonimage forming” radiation (bad) versus “image forming” radiation (good), is related primarily to the volume of anatomy being radiographed, (ie, more volume = more scatter radiation).

47

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2

Hazards of radiation exposure

It is the task of every responsible surgeon to be aware of the risks of ionizing radiation to himself as well as the operating team. Once exposed to radiation, any changes caused to the body are largely irreversible. Normal and abnormal variations in the host may result in undue susceptibility of cells and organs to certain forms of radiation. The only effective method of minimizing exposure is awareness and physical protection.

a

b

Some facts about radiation risks

Fig 5-2a–b

X-rays cause ionization (removal of electrons) of atoms that make up organic molecules. Ionized atoms will not bond properly on a molecular level causing disruption to the molecule and thus disrupting cellular function. This ionization effect from x-rays can be direct or indirect: Direct effects occur when molecules within the cell are disrupted due to ionization of their constituent atoms by direct energy transfer from the x-ray. This can disrupt any molecule in the cell involved in any cell process, including deoxyribonucleic acid (DNA). Indirect effects of x-rays to biological organisms are via the ionization of water, forming free radicals, which in turn react with, damage, and oxidize molecules and DNA. As human tissues contain approximately 80% water, radiolysis of water and its indirect effect on cellular molecules account for 95% of the effects of x-rays on the organism.

radiation exposure.

If the DNA molecule is affected, the resulting damage may be permanent or reversible by DNA repair processes. DNA damage from ionization is usually either a change in the nitrogenous base pair (changing the genetic code) or cross linking of strand (interference with translation of the code)

Different forms of chromosome damage following

(Fig 5-2). This may result in: Genetic repercussions Instant cell death (large doses cause DNA breakdown) Reproductive death (cells unable to divide) Interphase death (cell death without attempt at division) Mitotic death (cell death after one or more divisions) Mitotic delay (delay in cell division) The Law of Bergonie and Tribondeau states that “the radiosensitivity of cells is directly proportional to their reproductive ability activity and inversely proportional to their degree of differentiation”. Muscle and bone are relatively radioresistant, but skin, reproductive cells, and hematopoetic cells are radiosensitive. The biological damage to living organism from radiation exposure is known as somatic effects. Early effects are due to highdose radiation and not typical of diagnostic imaging radiation. Chronic effects appear months or years after exposure and can be seen with multiple low-dose radiation exposure over years

48

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5

Intraoperative imaging

such as in diagnostic radiology. The main categories of these chronic somatic effects are: Cancer induction (eg, skin cancers, leukemias) Damage to the fetus Cataractogenesis Thyroid disease Shortening of life span Stochastic events (nonthreshold effects) are effects in which the probability of occurrence is related to the cumulative dose but not to the severity of effects (Fig 5-3). These include genetic damage and carcinogenesis. Carcinogenesis includes skin cancers especially on hands of medical radiation workers, leukemia, and thyroid carcinomas. Since the introduction of safety measures, there has been no reported increase in rates of cancer in this subgroup.

3

3.1

Safety measures

Protective equipment

Gowns with 0.5 mm lead equivalent can cover about 80% of active marrow and can reduce the effective dose by a factor of 16. Thyroid shields protect the neck area and can reduce the radiation exposure to the gland by a factor of 13; without them radiation exposure is 70 times more. Lead glasses decrease exposure of the eyes (which may lead to cataracts)—0.15 mm lead equivalent goggles attenuate 70% of beam energies (Fig 5-4). Lead screens provide additional protection for OR personnel who do not wear lead protection. The thick lead gloves common in radiology suites are cumbersome and are not used in the OR.

Nonstochastic events (threshold limited effects) are effects that will not occur below a certain dose and whose severity depends on the dose. Examples are cataractogenesis and reproductive cell damage.

Lead goggles

Risk of DNA damage (cancer, birth defect)

Thyroid shield

Gown

No effects measured Radiation dose

Fig 5-3

Risk of DNA damage increases in relation to the cumulative

Fig 5-4

Protective equipment.

dose, but not to the severity of effects (stochastic events).

49

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3.2

Protective procedures

Simple measures such as moving as little as 0.5 m away from the part being radiographed (a step or two back) will reduce the amount of radiation exposure dramatically, and at 3 m there will be negligible radiation scatter to the person, by the principle of “inverse square law” (inversely proportional to the square of the distance from the source). The surgeon and assistant should face the image intensifier source during exposure as side-facing by the surgeon may allow increased radiation exposure. The exposure to anesthetist has been recorded as negligible, but the amount of exposure to the surgical assistant has been recorded to be greatest. The parts of the body at greatest risk are the hands of the surgeon or the assistant. All efforts must be made to keep hands away from the field of exposure. Application

Effective dose

The International Commission on Radiation Protection (ICRP) recommends a limit of effective dose of 20 mSv (millisievert) per year, averaged over 5 years (100 mSv in 5 years), with the further provision that the effective dose should not exceed 50 mSv in any single year. Table 5-1 shows the dose limits for individual anatomical areas. Most studies have shown that dose limits are not exceeded during orthopedic procedures. For practical purposes, the best methods for reducing potential exposure to radiation are the following: Reduce exposure time with modern efficient machine. Increase distance between limb and surgeon. X-ray source position (“face the beam”). Reduce air gaps (receiver close to limb). Use digital magnification (keep receiver close to limb). Collimation (narrow the window) of the beam (Fig 5-5).

Dose limit Occupational

Public

20 mSv per year,

1 mSv in a year

averaged over defined periods of 5 years Annual equivalent

Occupational

Public

150 mSv

15 mSv

the skin

500 mSv

50 mSv

the hands and

500 mSv

dose in: the lens of the eye

feet

Tab 5-1

Recommended dose limits of radiation exposure

in mSv (millisievert).

Fig 5-5

Collimation of the beam reduces potential exposure to

radiation.

50

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5

Intraoperative imaging

Use the maximum voltage possible. Ensure image memory is activated and used. Use radiation shields and other equipment. Monitor the amount of radiation used per exposure and consciously reduce the exposure time (Fig 5-6). Never use the C-arm with the receiver below or as a “hand table”; scatter from metal surfaces or instruments will reach the eyes and thyroid region.

4

The OR fluoroscope (or C-arm) is a portable machine that has revolutionized orthopedic surgery. The surgical team can be certain to a large extent of the accuracy of fracture reduction and placement of implants. Each machine may have different functions and modes. It is essential to familiarize oneself with the machine available in one’s practice. 4.1

NAME PATIENT ID PROCEDURE ACCESSION

Generator mode Fluoro HLF/Snapshot Film Totals

Field of view Normal Mag 1 Mag 2 Mode Continuous Pulsed

DATE PHYSICIAN

Time 312.0 0.0 0.0 312.0

Cumulative dose s s s s

100.0 0.0 0.0 119.0 797.6

% % % rad/cm 2 mrad

Time

Cumulative dose

187.1 s 125.0 s 0.0 s

55.1 % 44.9 % 0.0 %

Time

Cumulative dose

312.0 s 0.0 s

100.0 % 0.0%

DOSE SUMMARY

Fig 5-6

Monitoring the amount and exposure time of radiation.

Portable fluoroscopy machine or C-arm

The machine

The C-arm itself mounts a radiation source with a collimator screen (x-ray tube unit) which allows gamma rays to be beamed to the photosensitive receiver array (image intensifier) (Fig 5-7). The received image that has traversed the body will differ in intensity and the image captured is processed electronically to produce an enhanced picture on a digital screen. The radiation power (kilovolt, kV) and exposure (milliampere, mA) are usually automatically set to produce an optimal image and varies with the mass through which the beam passes. In obese patients more radiation will be emitted, usually without the knowledge of the operating team. They must thus be aware of this function. The receiver diameter is usually 9 in, 12 in, and rarely 18 in with a larger image area with the latter, which is preferred in orthopedic surgery. The direct beam width is constrained not to exceed this diameter, but the scatter is increased with the larger receiver size, due to wider beam width. A common and dangerous mistake is to position the receiver upside-down or as a “hand table” as this allows beam scatter to reflect off metallic instruments toward the eyes and neck of the surgeon. Obese patients or large limbs also produce more scatter radiation, so the team should stand further away in such situations.

51

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4.2

Imaging modes

Several modes of imaging may be available on the machine: continuous fluoroscopy (which would emit the most amount of radiation, up to five times that of pulsed fluoroscopy) can be used for dynamically evaluating joint motion; single pulse mode fluoroscopy, which is commonly used; and pulsed screening mode, which gives up to 30 pulses per minute. By allowing only single pulses in pulsed screening mode, a substantial reduction in the amount of radiation exposure occurs.

The image can also be magnified for better resolution especially for the articular surface, but at the cost of a higher dose of radiation. 4.3

Memory modules

Modern machines are able to store large numbers of highresolution images (4–99). This allows the user to recall the appropriate ones, or to print out for documentation. The dose summary can also be recorded and printed (Fig 5-6).

Image intensifier

X-ray tube unit

Fig 5-7

C-arm with radiation source (x-ray tube unit) and receiver array (image intensifier).

The received image is processed electronically to a digital screen.

52

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5

4.4

Intraoperative imaging

Printer

A high-resolution thermal printer allows hard copies of the selected images to be kept, or the image can be stored on some form of digital media and printed onto fi lm either digitally or in a dark room. However, the soft x-ray resolution produced by the C-arm is still not adequate or permanent enough for a stand-alone document. A routine postoperative plain (hard) x-ray is still recommended. 4.5

3-D models

Some companies are now producing C-arm machines that can automatically acquire multiplanar images, just like a computed tomography (CT) scan, and reformat them into 3-D images. These can be linked to computer navigation devices and reduces intraoperative exposure.

Obtain only the necessary minimum number of images. Rely on stored images without the need to reexpose. Minimize use of magnification. Collimate the image whenever possible. 5.1

The machine body is usually placed opposite the surgical team. This means in most cases that the source is below and the receiver is above in a standard AP projection. In the lateral projection the source is usually at the surgeon’s side. It is of critical importance that the surgical team is aware of the increase in scattered radiation in this lateral projection. One way to avoid this is to use the “over-the-top” C-arm position with the receiver/intensifier on the surgeon’s side. Another way is to stand further away—3 m being a safe distance—or behind a lead screen during lateral exposures. 5.2

5

Requirements and set-up in the OR

It is easy to overuse intraoperative fluoroscopy as the surgeon strives to perform a difficult operation. In order that radiation exposure should be minimized, these points should be followed: Always perform preoperative planning before the operation. Inform your assistants and staff what you have planned. Inform the radiographer where you want the C-arm positioned. Perform a trial screening in the projections you need after positioning the patient and ensure the radiographer remembers these positions, or marks the floor positions for the wheels. Adjust the patient’s position in case you need special projections.

Positioning

Obtaining maximum image

By placing the receiver of the C-arm as close as possible to the limb or bone, a smaller image of the bone is obtained but of a much larger area, allowing a better overall assessment of the alignment (Fig 5-8). 5.3

Obtaining imaging in the correct orientation

Obtaining a view on the image intensifier correctly aligned to the surgeon’s position relative to the limb will greatly simplify surgery. Image intensifier images can be fl ipped horizontally (mirror image), vertically, and rotated. This will allow the image of the bone to be viewed in the same orientation as the surgeon is viewing the limb. Reduction maneuvers, implant insertion, and screw placement are greatly facilitated. It may be necessary to reorientate the image when the C-arm is switched to the lateral position. In addition it is also beneficial that, as far as possible, the beam of the x-ray should travel 53

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perpendicular to the limb or bone. Oblique views should be avoided if possible. However, this may not be possible for the proximal humerus and proximal femur, and if this is understood allowances can be made. 5.4

Specific positioning for MIPO procedures

Each chapter for the different surgical techniques will show recommended positions for the C-arm.

6

Radiation in the operating environment is unavoidable today during many orthopedic procedures, including MIPO. It is possible that there may be increased incidence of radiation overexposure among orthopedic surgeons, mainly due to lack of awareness of the danger of cumulative radiation. Protection is simple, and it is easy to adhere to the adage “as low as reasonably achievable” (ALARA).

b Fig 5-8a–b

Conclusion

a

Placing the receiver closed to the limb results in an image of a large area of bone (a), as opposed to a large but

unclear image when the limb is placed near to the radiation source (b).

54

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5

7

Intraoperative imaging

Suggested reading

Smith GL, Wakeman R, Briggs TW (1996) Radiation exposure of orthopaedic trainees: Quantifying the risk. J R Coll Surg Edinb; 41(2):132–134.

Dewey P, Incoll I (1998) Evaluation of thyroid shields for reduction

Tasbas BA, Yagmurlu MF, Bayrakci K, et al (2003) Which one is

of radiation exposure to orthopaedic surgeons. Aust N Z J Surg;

at risk in intraoperative fluoroscopy? Assistant surgeon or orthopaedic

68(9):635–636.

surgeon? Arch Orthop Trauma Surg; 123(5):242–244. Epub 2003

Giachino AA, Cheng M (1980) Irradiation of the surgeon during

May 10.

pinning of femoral fractures. J Bone Joint Surg [Br]; 62–B(2):227–229.

Theocharopoulos N, Perisinakis K, Damilakis J, et al (2003)

Goldstone KE, Wright IH, Cohen B (1993) Radiation exposure to

Occupational exposure from common fluoroscopic projections used in

the hands of orthopaedic surgeons during procedures under

orthopaedic surgery. J Bone Joint Surg [Am]; 85(9):1698–1703.

fluoroscopic x-ray control. Br J Radiol; 66(790):899–901. ICRP Publication 60 (1991) 1990 Recommendations of the International Commision on Radiological Protection, 60. Annals of the ICRP; 21:72–79. Jones DG, Stoddart J (1998) Radiation use in the orthopaedic theatre: A prospective audit. Aust N Z J Surg; 68(11):782–784. Keenan WN, Woodward AF, Price D, et al (1996) Manipulation under anaesthetic of children’s fractures: Use of image intensifier reduces radiation exposure to patients and theatre personnel. J Pediatr Orthop; 16(2):183–186. Lo NN, Goh PS, Khong KS (1996) Radiation dosage from use of the image intensifier in orthopaedic surgery. Singapore Med J; 37(1):69–71. McGowan C, Heaton B, Stephenson RN (1996) Occupational xray exposure of anaesthetists. Br J Anaesth; 76(6):868–869. Muller LP, Suffner J, Wenda K, et al (1998) Radiation exposure to the hands and the thyroid of the surgeon during intramedullary nailing. Injury; 29(6):461–468. O’Rourke PJ, Crerand S, Harrington P, et al (1996) Risks of radiation exposure to orthopaedic surgeons. J R Coll Surg Edinb; 41(1):40–43. Sanders R, Koval KJ, DiPasquale T, et al (1993) Exposure of the orthopaedic surgeon to radiation. J Bone Joint Surg [Am]; 75(3):326–330. Smith GL, Briggs TW, Lavy CB, et al (1992) Ionising radiation: Are orthopaedic surgeons at risk? Ann R Coll Surg Engl; 74(5):326–328.

55

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6

Computer assisted surgery in MIPO

1

Introduction

57

2

Computer guided surgery technology

57

3

Evolution of navigation

58

4

Navigation of straight objects

58

5

Nails

59

6

Plates

59

7

Reduction

59

8

Accuracy

60

9

Applications

60

10

Equipment and set-up

60

11

Sample case—sacroiliac screw fixation navigation

62

Future

65

12.1

Basic connectivity

65

12.2

Fragment segmentation

65

12.3

Integration with implants and instrumentation

65

13

Suggested reading

65

12

56

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Author

6 1

Merng Koon WONG

Computer assisted surgery in MIPO Introduction

The essence of minimally invasive surgery (MIS) is to limit surgical trauma to the fracture site. This essentially translates to minimal disturbance of the blood supply in the area of trauma whatever the origin of the blood supply, be it endosteal, periosteal, or muscular. This preservation of blood supply will allow reparative processes to proceed with minimal disruption. Minimal skin incision and soft-tissue dissection help to lower the risk of infection and reduce the intensity of postoperative pain, and have the added advantage of promoting faster functional recovery. These requirements of fracture management necessarily limit surgical exposure; critically to the fracture site and less so to the rest of the main proximal and distal fragments. Thus open visualization of reduction and fi xation of a multifragmentary fracture is a luxury that should be avoided in order to preserve biology, which is paramount to fracture healing via callus. Realistically, respect of this “no touch” technique at the fracture site creates great technical difficulties in reconstruction of length as well as alignment both in terms of translation and rotation. Excessive radiation for visualization is inevitable. Moreover, the C-arm projects a 2-D image at any one time with consequent need for orthogonal views which still do not approximate the visual let alone tactile feedback of open fracture visualization and manipulation. There are two main exceptions to the preeminence of biology over mechanics in fracture repair. Intraarticular fractures absolutely require anatomical and stable fi xation to avoid joint surface incongruence and future posttraumatic arthrosis. Strain-intolerant simple transverse or short oblique fractures predictably result in impaired union if absolute stability is not engineered during surgery.

2

Computer guided surgery technology

The past two decades have witnessed rapid advances in imaging technology. Today it is not difficult to achieve 3-D reconstructions of complex fractures from CT, MRI, or even PET scan data. It is a pity, but perhaps not surprising, despite such amazing preoperative diagnostic imaging, we do not see any provision of that information in a real-time interactive intraoperative manner. Computer guided surgery could improve intraoperative visualization of fracture reduction and fi xation through its ability to provide real-time simultaneous presentation of multiple views of fracture anatomy thus decreasing the use of radiation (Fig 6-1). In addition, multiple views of important limb alignment end points allow restoration of length and alignment to the injured limb.

Fig 6-1

Parallel visualization of multiple fluoroscopic views of

relevant anatomy. Virtual representation of tools and implants.

57

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3

Evolution of navigation

Early efforts took care of correcting some intrinsic inaccuracies in the system of image acquisition. Computerized scanning methods such as CT and MRI have algorithms built in to correct for ray scatter and thus image distortion. However, there is intrinsic difficulty in registration or matching of intraoperative data to allow projection of preoperative CT and MRI data. There is additional difficulty checking for intraoperative changes in relationship of fracture fragments as very few operating rooms have built-in CT or MRI.

C-arm imaging techniques are well suited to monitor intraoperative changes in fracture fragment relationships. However, there is still significant image distortion due to the central projection of x-rays and spheric intensifier tubes (pin cushion distortion), electromagnetic influences (magnetic field of earth) and mechanical flexing of the heavy C-arm at different inclinations (Fig 6-2).

4

Navigation of straight objects

The obvious next step in the evolution was the tracking of straight nonbending instruments such as pointers and drills (Fig 6-3).

a

c

b

c

d

a

e

b Fig 6-2a–b

Fig 6-3a–e

a

a–d Set of navigation tools. Sharp pointer (a), ortho pointer (b), drill

Gravity may change the position of the x-ray tube toward the intensifier tube.

b

guide handle with different sleeves and matching drills (c),

Undistorted image (left), pin cushion distortion (middle), S-distortion (right) intensifi er tube.

Image Guided Surgery (IGS) toolset (d). e

Navigation of a drill bit with a rigid nonbending drill guide.

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6

5

Computer assisted surgery in MIPO

Nails

There are many benefits of navigated intramedullary nail insertion. Finding and drilling the entry point becomes reliable due to parallel visualization of multiplanar views of the proximal tibia or femur. Multiple fracture fragment tracking allows for threading the distal fragment with the nail during the navigated reduction. Special planning steps in the workflow enable the surgeon to control length, axis, and rotation of long-bone fractures. C-arm images of the distal interlocking holes can be used for planning and targeting the interlocking screws, taking care of the perceptible bending and torsion of the nail after negotiating the intramedullary canal (Fig 6-4). Navigation of a slightly curved but rigid nail is the logical next step.

Fig 6-4

Navigation screen of a femoral reduction. The two upper

6

Plates

Precontoured plates can also be navigated. The trajectory of the locking head screws (LHS) in the less invasive stabilization system (LISS) could have virtual representation to allow easy targeting. Intraoperatively contoured plates can be registered and tracked subsequently. Yet later deformation of the plate must be tracked to be properly represented.

7

Reduction

Tracking of fracture fragments requires a reference array in each fragment. The available array fi xtures therefore limit the fragment size to be tracked (Fig 6-5). In a further development automatic segmentation could visualize individual fragments in 3-D.

a

b

views show AP and lateral fluoroscopic images of the fracture region

Fig 6-5a–b

together with the current position and orientation of the bone frag-

fi xation tools for the reference arrays. Minimally invasive reference

ments. The two lower views give a 3-D representation of important

arrays (MIRA) are attached to the bone either with a 5 mm Schanz

parameters such as axis alignment, antetorsion and leg length.

screw (1-pin MIRA, a) or two 3 mm K-wires (2-pin MIRA, b).

The traceable fragment size depends on the size of the

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8

Accuracy

The accuracy of most commercial navigation systems is better than 2 mm after calibration. However, inaccuracies can be introduced by inadequate handling of the navigation equipment. Any relative movement of the tracking arrays against their bony support during surgery increases inaccuracy, directly depending on the extent of movement. The surgeon must check the status and accuracy of his bone tracking during operation and he must make provisions to avoid such movement.

9

Applications

10

Equipment and set-up

The basic equipment for navigation consists of reference arrays, tools, a camera, a computer, a screen, and an image intensifier. Reference arrays are placed on the C-arm of the image intensifier, on tools, and on the patient’s bone. The camera analyzes the reference positions optically, while the computer integrates localization data and image data of the C-arm. The screen displays the integrated information and serves as an interface to operate and control the system. The optical analysis of the reference array position and the system handling by the surgeon requires some care when planning the OR set-up for navigated procedures.

The time required for set-up and additional resources need to be considered when navigating (Fig 6-6). Of course the added value of the new method must compensate for those additional demands. Especially in complicated anatomical situations with difficult approaches through small incisions, navigation can be a great help, eg, in the targeting of sacroiliac screws or targeted biopsies of deep bone structures. Intraoperative x-rays can be cut down considerably during the insertion of intramedullary nails, compensating the time needed for the set-up by shortening the time needed for C-arm handling. In the same time length, axis and rotation changes in long-bone fractures are accessible online to the surgeon, avoiding malrotation and limb shortening after intramedullary nailing.

Fig 6-6

Additional set-up time and resources are required for

computer assisted navigation.

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6

Computer assisted surgery in MIPO

In most cases the caudolateral position of the system and caudal position of the camera offer the best reference visibility to the camera, while the surgeon has access to the touch screen for system handling. To register images acquired with the C-arm, the fluororegistration kit is mounted on the image intensifier. For accurate use, the kit must be set flush and centered on the image intensifier. The kit can be sterilized. It is recommended to place it sterile over the draping to avoid compromising the visibility by the drape. If the surgeon wishes to handle the system himself, the touch screen can be covered with a sterile draping. The camera handle can be draped similar to the illumination handles. The reflective markers are sterile and disposable. Resterilization damages their reflective surface and so leads to inaccuracy. The markers are tightly screwed on the threaded sockets of the arrays prior to the procedure. For accuracy reasons, no blood, liquid, stain or taint is tolerable, as they spoil the circular light reflex and so might lead to invisibility of a reference array or, worse, inaccurate navigation data.

iliac crest for unstable traumatic pathologies when draping the patient should also be borne in mind. A Y-shaped reference array is fi xed to a stable structure of the pelvis to track the bony pelvis during navigation. The reference position should be chosen carefully to avoid collisions with the C-arm and to enable camera visibility during the procedure. A 5–6 mm Schanz screw or two 3–5 mm K-wires are introduced axially into the iliac crest to serve as base for a one-pin or a two-pin fi xation of the minimally invasive reference array (MIRA). The MIRA is then fi xed on the pins. When using one pin, great care should be given to a stable and fi rm bone contact of the MIRA on the bone surface. Any movement of the bone relative to the spheres will lead to inaccuracy of the navigation. In case a reference fi xation has become unstable, always check for stability and control accuracy by touching the landmarks with the pointer. If a reference array loosens, its original position is usually hard to fi nd. To continue navigating, acquire new images after refi xing the reference.

For sacroiliac screw fi xation the patient is positioned supine. Other positions are possible, as long as visibility of the fluoroscopic anatomy and the reference arrays are adequate. To facilitate access to the incision point, the procedure side can be elevated. When placing the patient on the table, allowance should be made for space requirements of the C-arm for inlet and outlet images of the pelvis especially in the longitudinal axis of the patient. The reference attachment site on the ipsilateral iliac crest for stable degenerative pathologies or on the contralateral 61

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11

Sample case—sacroiliac screw fixation navigation

Case description

A 44-year-old male was transferred from another hospital 3 days after a fall from the fourth storey of a building, during which he sustained the following injuries (Fig 6-7): Vertically unstable fracture of the left hemipelvis with a Morel–Lavallé lesion Burst fracture of L2 vertebra with neurological deficit Fracture dislocation of left elbow The initial treatment consisted of stabilization of his prerenal failure, early disseminated intravascular coagulopathy and severe anemia. Skeletal traction was applied to the left leg.

management. Open compression screws would face a very high risk of infection due to a degloved buttock. An ilioinguinal approach would also subject the patient to both a high infection risk with the suprapubic catheter in place as well as prolonged open surgery with its antecedent systemic load in terms of bleeding and anesthesia. Preoperative preparation

The patient was positioned supine on an extended radiolucent operating table. The C-arm was positioned to allow pelvic inlet, outlet, and shoot-through lateral sacral views without hitting the post of the operating table. (The C-arm should also be trackable via the infrared cameras of the navigation system in all these views.) Indirect reduction

Indication

The critical general and local condition (Morel–Lavallé lesion) of the patient required a minimally invasive fi xation of the pelvic fracture as the fi rst building block in his surgical

a

b

Restoration of limb length was maintained by skeletal traction through the left lower limb. Reduction of rotation was maintained by taping the knees together.

c

Fig 6-7a–c a

Vertically unstable fracture of left hemipelvis with a high fl oating bladder drained via a suprapubic catheter.

b

Pelvic fracture associated with Morel–Lavallé degloving lesion.

c

Segmental fracture of left sacrum involving the neural foramina.

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6

Computer assisted surgery in MIPO

Surgical approach

The patient was cleaned and draped. The reference base was affi xed onto the left anterior superior iliac spine. X-rays of the pelvic inlet, outlet, and shoot-through lateral sacral views were acquired and transferred to the navigation computer (Fig 6-8). The trajectory of the drill would be tracked and represented by colored lines superimposed over the stored key fluoroscopic views. The percutaneous insertion point for the drill as well as the direction of drilling was guided by the navigation system. The surgeon had access to real-time trajectory information in

Fig 6-8

Patient is positioned supine and key views of the anatomy

are acquired. The reference base is affi xed onto the left anterior

four key fluoroscopic views making this procedure much quicker and more reliable. Before the advent of computed assisted navigation, the drill was advanced while alternating between the inlet and outlet pelvic view. Since the pelvis is oriented at 45º in the sagittal plane this makes the appreciation and consequently the drill targeting extremely difficult (Fig 6-9). The drill tracks into the vertebral bodies of S1 and S2 were replaced with K-wires for the 7.3 mm cannulated cancellous bone screws. The fi nal positions of the K-wires were

Fig 6-9

Clockwise from the top left: The pelvis PA, shoot-through

lateral sacral view, the outlet pelvic view, and the inlet pelvic view.

superior iliac spine.

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double-checked with the C-arm to ensure the accuracy of the navigation computer. Importantly, there should not be hardware in the spinal canal. These K-wires were replaced with the cannulated cancellous bone screws (Fig 6-10).

9 months postoperatively, x-rays showed healing of the pelvic/ sacral fractures and the patient was ambulatory with a cane.

Postoperative x-rays were taken to confi rm the C-arm images (Fig 6-11). 1 week later L2 decompression corpectomy and fusion were performed.

a

b

a

b

Fig 6-10a–b The view through lateral sacrum and inlet pelvic x-rays to check that no hardware was in the spinal canal.

Fig 6-11a–b

Immediate postoperative x-rays.

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6

12

Computer assisted surgery in MIPO

Future

Despite intensive developmental efforts there remain shortcomings in three main aspects.

13

Suggested reading

DiGioia AM 3rd, Jaramaz B, Colgan BD (1998) Computer assisted orthopaedic surgery. Image guided and robotic assistive technologies. Clin Orthop Relat Res; Sept (354):8–16.

12.1

Basic connectivity

Grutzner PA, Suhm N (2004) Computer aided long-bone fracture treatment. Injury; 35 Suppl 1:S-A57–64.

Wired components increase logistic demand for space and connection management. This obviously increases set-up time.

Nolte LP, Beutler T (2004) Basic principles of CAOS. Injury; 35 Suppl 1:S-A6–16. Nolte LP, Slomczykowski MA, Berlemann U, et al (2000) A new approach to computer-aided spine surgery: fluoroscopy-based surgical

Wireless components suffer from slower refresh rates and thus lower real-time accuracy.

navigation. Eur Spine J; 9 Suppl 1:S78–88. Schmucki D, Gebhard F, Grutzner PA, et al (2004) Computer aided reduction and imaging. Injury; 35 Suppl 1:S-A96–104.

In terms of ergonomics, wireless low profi le with an adequate refresh rate is a prerequisite for widespread application of this technology. 12.2

Fragment segmentation

The ability to extract bony outlines from imaging data is the fi rst step in tracking individual fragments during intraoperative manipulation and reduction. From there it is but a small step to morph a virtual representation of bone to enhance visual representation of fragments during surgery. 12.3

Integration with implants and instrumentation

There are strong efforts by the AO Technical Commission (AOTK) to integrate implants into navigation as well as to design implants and instrumentation to align with the concepts of biological and minimally invasive surgery. Obviously integration of all three aspects will see fruition in the future.

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7

Reduction techniques

1

Introduction

67

2

Goals of reduction

67

2.1

Articular fractures

67

2.2

Diaphyseal fractures

67

3

Methods of reduction

67

3.1

Indirect reduction

68

3.2

Direct reduction

68

4

Reduction techniques

68

Articular fractures

68

4.1

4.2

4.1.1

Indirect reduction

4.1.2

Direct reduction

Diaphyseal fractures 4.2.1

Indirect reduction

4.2.2

Direct reduction

72

5

Summary

77

6

Suggested reading

77

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Authors

7 1

Frankie KL LEUNG, Shew-Ping CHOW

Reduction techniques Introduction

There has, over the years, been a change in the concept of fracture fi xation and the emphasis today is on the preservation of the biology of bone and soft tissue. The preserved blood supply leads to a more rapid fracture union and lessens the chance of complications such as delayed union, implant failure, and infection. Similarly, in fracture reduction it is essential that reduction techniques applied do not cause further damage to the blood supply and soft-tissue attachments in the fracture zone. It is clearly vital to understand the goals of the reduction and how this can be accomplished with a maximum preservation of biology.

2

Goals of reduction

It is well accepted that fracture reduction is a crucial factor in achieving bony union and preserving form and function. The degree of accuracy of reduction can, however, range from axial realignment to anatomical reduction of each fracture fragment. The surgeon has to select the appropriate technique and the degree of accuracy of reduction based on the fracture pattern and the segment of bone involved. The key is to use the method of reduction causing least damage to the soft tissue and blood supply at the fracture area. 2.1

Articular fractures

In intraarticular fractures, anatomical reduction and stable fracture fi xation must be achieved in order to allow good healing of the articular cartilage. Precise reduction is of crucial importance to avoid local overload and exposure of subchondral bone and thus reduce the incidence of posttraumatic arthrosis. After achieving stable fi xation with interfragmen-

tary compression, early range-of-motion exercises can be started. In some cases, continuous passive motion therapy can promote healing and the formation of hyaline cartilage rather than fibrocartilage. 2.2

Diaphyseal fractures

In multifragmentary diaphyseal fractures, it is only essential to achieve functional reduction, which consists of restoration of length, mechanical axis, and rotational alignment of the main fracture segments that carry the joint surfaces. It is unnecessary to achieve precise reduction of each fracture fragment. Such action may in fact jeopardize the blood supply to the bone. The two main fracture fragments are stabilized without disturbing the multifragmentary zone and its vascularity, the aim being to promote indirect bone healing within 4–6 weeks. In contrast, simple diaphyseal fractures, such as transverse, oblique, or spiral fractures, should preferably be treated by anatomical reduction and compression fi xation to obtain absolute stability so that implant failure from high stress concentration may be avoided.

3

Methods of reduction

In MIPO, the aim is to achieve fracture reduction and fi xation without exposure of the fracture site. Thus, whenever possible, indirect reduction should be the method of choice. However, this may not always be possible as the quality of reduction achieved may not be acceptable. Under such circumstances, it may become necessary to resort to direct reduction methods to obtain the desired accuracy of reduction. Even in such instances, small incisions with minimal soft-tissue dissection should be the rule. 67

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3.1

Indirect reduction

For indirect reduction, the fracture site is not exposed and remains covered by the surrounding soft tissue. Hence there is maximal preservation of the biology surrounding the bone fragments. Reduction is accomplished using instruments or implants introduced away from the fracture zone. To achieve reduction, traction is usually applied in the long axis of the limb. This only works when the fragments are still connected to some soft tissue. However, since there is no direct visualization of the fracture site, the reduction may not be anatomical. In most cases, there will be gaps between the fracture fragments and healing across the fracture gaps will be achieved by callus formation. The main indications for indirect reduction are multifragmentary diaphyseal fractures, although some minimally displaced simple articular fractures are also amenable. An image intensifier is essential to check the quality of the reduction, while arthroscopy can be helpful in articular fractures. 3.2

Direct reduction

In direct reduction, the fracture site is exposed and the fracture fragments directly manipulated. All maneuvers are seen and controlled under direct vision. This type of reduction technique is easier than indirect reduction and the reduction more precise. However, application of reduction tools often damages the soft tissue surrounding the bone, thus affecting the vascularity of the bone fragments. There are several indications for direct reduction. Simple diaphyseal fractures are often treated by anatomical reduction and rigid internal fi xation. It is technically straightforward and the result is easy to assess. The aim of treatment is absolute stability that will result in direct bone healing. Even then, the

surgical exposure used should just be adequate for the direct reduction to be carried out with minimal stripping of the periosteum and the rest of the fracture fi xation can then be performed in a similar fashion to percutaneous plate fi xation if possible. For articular fractures, the success of surgery will rely on restoration of a congruent articular surface. A small direct incision over a specific articular fragment to achieve reduction may be necessary. A preoperative CT scan is necessary to plan the appropriate approach and reduce the exposure required for reduction of the articular fracture.

4

4.1

Reduction techniques

Articular fractures

Various reduction techniques can be applied depending on the pathoanatomy of the articular fracture. The aim is to obtain anatomical reduction followed by stable fi xation. 4.1.1

Indirect reduction

Closed indirect reduction may be achieved by manual traction. This forms the basis of ligamentotaxis. However, this is only successful if the bony fragments still retain their soft-tissue attachments such as the joint capsule or ligaments. The quality of reduction in these indirect methods can be monitored by an image intensifier or arthroscopy. Once the reduction of the articular surface is deemed satisfactory, fi xation of the intraarticular component of the fracture should be performed, preferably by percutaneous fi xation methods.

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7

4.1.2

Reduction techniques

Direct reduction

In order to obtain anatomical reduction and a congruent joint surface, it is often necessary to perform direct reduction. This direct reduction can be achieved either by open methods or through remote access. Whatever the approach, it is necessary to minimize the adverse effects of direct reduction when exposing the fracture area but, at the same time, ensuring that the quality of reduction is not compromised.

In intercondylar fractures of the distal femur, direct reduction through a parapatellar arthrotomy is usually required to obtain an anatomical reduction of the joint surface. Flexion of the knee with a support will help to align the fracture, while Schanz screws inserted as manipulators into both condyles also help to reduce the articular fractures. A distractor may be applied to help reduce the metaphyseal fracture (Fig | Anim 7-3).

In multifragmentary articular fractures of the tibial plateau in which the fragments are of considerable size, direct reduction through an arthrotomy or under fluoroscopic or arthroscopic guidance is usually required. In split depression fractures, reconstruction of the depressed fragment is best achieved using an open technique by separation of the split fragment and restoring the depressed articular fracture. In a simple wedge fracture extending from the articular surface to the metaphysis, the exact reduction of the spike of the articular fragment to the corresponding defect in the metaphysis will lead to the anatomical reduction of the articular surface without the need to expose the joint. This reduction can be performed either through a small incision over the spike or percutaneously using a manipulator, the reduction being maintained by K-wires or a large pelvic reduction clamp (Fig 7-1). An example of the application of direct reduction through remote access in articular fractures is in pure depression fractures of the tibial plateau. Such fractures should be elevated and reduced directly via a window created in the metaphyseal cortex followed by bone grafting to provide support for the elevated articular fragments. The whole procedure is carried out under fluoroscopic guidance (Fig 7-2).

Fig 7-1

A large pelvic reduction clamp can be used, especially in

fractures around the knee and ankle.

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Fig 7-2a–e

Fluoroscopic guidance of direct reduction through remote access in a depressed

fracture of the tibial plateau. a

CT scans show a depressed articular fragment at the lateral tibial plateau. Additionally there is a split fracture of the medial tibial condyle.

b–c C-arm AP and lateral view show the impactor following the enlarged tract to elevate the depressed articular fragment. d–e The reduction is maintained first by K-wires which are then replaced by cancellous

a

b

bone screws.

c

d

e

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7

Reduction techniques

Animation

a

b Fig | Anim 7-3a–c a–b The pull of the gastrocnemius muscle can be neutralized by knee flexion thus providing realignment of the articular fragment. c

Direct reduction of femoral condyles with Schanz screws on T-handles supplemented by indirect reduction with trac-

c

tion using the distractor.

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4.2

Diaphyseal fractures

4.2.1

Indirect reduction

Indirect reduction is a demanding technique. Considerable difficulty may be encountered during the process as the fracture fragments are neither visualized nor directly manipulated. The surgeon must have a clear understanding of what constitutes normal anatomy for correct restoration of axis, rotation, and length of the limb, and also of the various methods used for checking the adequacy of the reduction obtained. Fluoroscopic guidance is indispensable to carry out indirect reduction.

For most diaphyseal fractures, manual traction is effective. This is best carried out under fluoroscopic guidance and for this a radiolucent operating table is most helpful. Traction can also be applied with the help of an external fi xator or large distractor. Irrespective of the chosen method of applying traction, once satisfactory reduction has been obtained, it is advantageous to lock the position of the fracture fragments with the aid of an external fi xator or a large distractor. This will facilitate the subsequent fi xation of the fracture with the selected implants.

Traction

The application of traction is an important step in achieving reduction by indirect means. Traction helps to restore length and can be used to correct rotational malalignment and, to a certain degree, axial malalignment. For traction to be successful, the fracture fragments must retain their soft-tissue attachments as it makes use of the principle of ligamentotaxis. The fracture must also be relatively recent as soft-tissue contractures will prevent effective reduction. There are several ways in which traction can be applied: A traction table may be used for diaphyseal fractures of the lower limb, especially when the surgeon is operating alone. In this way, an adequate degree of traction can be maintained even when there is a lack of surgical assistance (Fig 7-4). One of the disadvantages of using a traction table is the difficulty of obtaining fi ne adjustment of the reduction which could otherwise be achieved manually if the patient was lying freely. There is also difficulty in assessing the quality of the reduction, as comparison with the intact side is not feasible.

Fig 7-4

A traction table should be used only if closed reduction is

possible and if traction will maintain the reduction, especially when the surgeon is operating alone.

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7

Reduction techniques

Supporting pads

Muscle forces acting on the fracture fragments often determine the pattern of displacement of a fracture. Traction alone can restore the normal length of the bone but may exaggerate the axial malalignment instead of correcting it. A supporting pad can be used to correct a recurvatum deformity (Fig 7-5). It is most often used in periarticular fractures such as those affecting the distal femur. External fixators and distractors

External fi xators and large distractors are most useful tools for reducing and maintaining the reduction of multifragmentary fractures of the diaphysis. Not only can they be used for applying longitudinal traction, but they also allow manipulation to correct axial and rotational malalignments. Following preparation of the injured limb under aseptic technique, Schanz screws are inserted into the main fracture fragments away from the fracture zone so that they will not interfere with the subsequent surgical procedure. Manipulation of the fracture under fluoroscopic guidance is performed and once satisfac-

tory reduction is obtained, the reduction is maintained by tightening the clamps on the fi xator or distractor. Manipulators

A Schanz screw can be inserted percutaneously into a large bony fragment and used as a manipulator to facilitate fracture reduction. Large threaded pins with holders are also available for the same purpose. Once appropriate reduction is achieved, the Schanz screws or manipulators can be connected by external fi xator tubes and clamps to hold the reduction in place. Push–pull technique

This technique is used to adjust length after preliminary fi xation of the fracture. A tension device applied to the end of the plate can be used to distract the fracture site to gain length (Fig | Anim 7-6). The plate is fi rst fi xed temporarily with a screw distally to ensure that the plate is positioned correctly before attachment of the tension device. The screw is removed before distraction is carried out. If desired, the tension device can be used to apply compression once the fracture has been reduced. Reduction by implants

Fig 7-5 formity.

A supporting pad can be used to correct a recurvatum de-

Fixed angled devices and anatomically shaped implants can be used as aids for fracture reduction. First, the articular block is fi xed to the plate. Standard cortex screws may be applied to pull the articular block to the plate. Once the reduction is achieved under fluoroscopic guidance, fi xation of the articular block is completed using additional standard or locking head screws (LHS), depending on the type of implant used. Next, the metaphyseal and diaphyseal components of the fracture are reduced to the articular block and the plate. If necessary, a cortex screw can again be used as an aid to pull the bone toward the plate (reduction screw). With certain types of plate

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Animation

a

b

c

Fig | Anim 7-6a–c a

Introduction of the condylar plate 95º, insertion of the screw proximally, and temporary monocortical screw fi xation distally to pull the bone to the plate.

b

Use of the tension device to distract the fracture to gain length in order to allow fracture reduction. The tempo-

c

If desired, the tension device can then be used to apply compression after reversing the direction of its hook.

rary fi xation screw at the distal end of the plate must fi rst be removed to allow the distraction to take place.

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7

Reduction techniques

such as the LISS, it is possible to use a special pull-reduction instrument which is placed through an insertion guide and plate hole to pull or push bone fragments in relation to the plate. Minor degrees of varus-valgus or translational malalign-

ment can be corrected using this device. When proper alignment of the articular and diaphyseal components of the fracture has been confi rmed, fi xation to the diaphyseal bone can be completed (Fig | Anim 7-7).

Animation

a

b

c

d

4 5 2 Fig | Anim 7-7a–f 3

a

1 6

b–e After incision, the metaphyseal fragment is fi xed temporarily to the plate

Anatomically shaped implants provide guidance for reduction. first, and position is confirmed under image intensifier before definitive fi xation with a cortex screw (reduction screw).

f e

f

The fi xation to the diaphyseal bone should then be completed in sequence (1–6), according to the preoperative plan.

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An LCP can also be used as a reduction tool. However, the plate must fi rst be contoured according to the anatomy of the bone, and then reduction and fi xation is carried out as described above. When using an LCP that has not been accurately precontoured, it is essential that an acceptable reduction is obtained before the application of LHS. A poorly reduced fracture will be fi xed in a poor position with LHS as these will not allow any collapse of the fracture after fi xation (Fig | Anim 7-8).

4.2.2

Direct reduction

Occasionally, the quality of indirect fracture reduction in diaphyseal fractures may be inadequate. It may then be necessary to perform direct reduction through small incisions in order to achieve the accuracy of reduction necessary to restore form and function after fracture fi xation and union. Simple fractures requiring anatomical reduction and stable fi xation for direct bone healing, displaced long oblique or spiral fractures, and widely separated large wedge fragments are examples of fractures which may benefit from direct reduction if indirect methods prove unsuccessful. Even with direct open reductions, it is important to bear in mind the importance of preservation of biology so that soft-tissue dissection and stripping is kept to the minimum. The instruments used should therefore be consistent with this principle and only cause minimal soft-tissue disruption. During open surgery, pointed reduction forceps should be used instead of reduction clamps which compress the periosteum. In transverse and short oblique fractures, a small Hohmann retractor inserted between the fracture ends as a lever is quite helpful for reduction. A large pelvic reduction clamp is useful in fractures around the knee and ankle. Collinear reduction forceps, with different arms for the diaphyseal and periarticular segments, are available and facilitate fracture reduction with minimal exposure of the fracture site.

Animation

a

b

Fig | Anim 7-8a–b a

The bone is gradually pulled toward the plate when standard cortex screws are inserted.

b

Angular stability of the LHS ensures maintenance of the initial reduction (= no loss of secondary reduction). Exact contouring is not necessary as the fracture is not reduced to the plate (= no loss of primary reduction). This is an advantage when the plate is used in conjunction with LHS in MIPO surgery.

Cerclage wires

Cerclage wiring can be helpful in reducing a large wedge fragment or an oblique or spiral fracture which is severely displaced and may cause delay in bone healing. This technique has the advantage of minimal denuding of the bone fragment. Insertion of the wirepasser should be done carefully with minimal stripping of the soft tissue around the fracture. Such wires may be temporary and removed immediately after the preliminary fi xation, or they may be left in place when an internal fi xator type of plate is used to fi x the fracture and there is a gap between the bone and the implant (Fig 7-9).

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7

Reduction techniques

b

a Fig 7-9a–c

c

Cerclage wiring can be helpful in reducing a large wedge fragment that is

severely displaced and may cause delay in bone healing. In fracture fi xation with an internal fi xator, such wires can be left in place if there is a gap between the bone and the implant.

5

Summary

In general, the modern trauma surgeon should be familiar with the different reduction techniques, ranging from direct and open manipulation to indirect and closed means. The choice of reduction technique should be made at the time of preoperative planning. If a closed and indirect reduction is not adequate, then one can choose to use an open and direct method of reduction. Even with direct methods, there exists a variety of reduction aids and tools which minimize intraoperative trauma to the soft tissue surrounding the fracture. The key is to leave a small foot print, or the least possible damage, at the fracture zone.

6

Suggested reading

Kregor PJ, Stannard J, Zlowodzki M, et al (2001) Distal femoral fracture fi xation utilizing the Less Invasive Stabilization System (L.I.S.S.): the technique and early results. Injury; 32 Suppl 3:32–47. Krettek C, Miclau T, Grun O, et al (1998) Intraoperative control of axes, rotation and length in femoral and tibial fractures. Technical note. Injury; 29 Suppl 3:29–39. Mast J, Jakob R, Ganz R (1989) Planning and Reduction Technique in Fracture Surgery. 1st ed. Berlin Heidelberg New York: Springer-Verlag. Müller ME, Allgöwer M, Schneider R, et al (1991) Manual of Internal Fixation. 3rd ed. Berlin Heidelberg New York: Springer-Verlag. Rüedi TP, Murphy WM (2001) AO Principles of Fracture Management. Stuttgart New York: Georg Thieme Verlag.

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8

Decision making and preoperative planning

1

Introduction

79

2

Planning in MIPO

79

3

Patient evaluation

79

12

Examples of cases with preoperative planning and the results 85

12.1

Tibia and fibula, proximal: complete articular fracture, articular multifragmentary—41-C3

12.2

4

Fracture evaluation

79

5

Graphic preoperative plan

80

5.1

Direct overlay

80

5.2

Overlay using the normal side

80

5.3

Use of physiological axes for articular fractures 80

6

Implants

81

6.1

Type of plate

81

6.2

Plate function

81

6.3

Plate length

81

6.4

Number of screws

81

6.5

Type of screw

82

6.6

Order of screw insertion

82

6.7

Plate position

82

6.8

Plate contouring

82

7

Reduction techniques

83

8

Timing of surgery

83

9

Control of axes, rotation, and length during MIPO

83

10

Preparing the OR

83

11

Alternative surgical tactic

84

85

Tibia and fibula, distal: complete articular fracture, articular simple, metaphyseal, multifragmentary—43-C2

12.3

13

87

Tibia and fibula, distal: complete articular fracture, articular multifragmentary—43-C3

89

Suggested reading

91

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Author

8 1

Tadashi TANAKA

Decision making and preoperative planning Introduction

Preoperative planning has always been an important component of the overall strategy of operative fracture care in the AO philosophy. Preoperative planning allows the surgeon to perform the operation in his mind before the actual surgical procedure. It gives him an opportunity to prepare the equipment that might be required, and enables him to plan the steps of the operation, including the location of the incisions, reduction technique, choice of implants, and techniques of application. With preoperative planning the surgeon is better prepared for surgery, thus ensuring a higher chance of success and avoiding possible complications. Another advantage is that the surgeon can provide the patient with a detailed explanation of the operation so that he can obtain informed consent and ensure a good patient–surgeon relationship.

2

Planning in MIPO

In MIPO, preoperative planning plays an even more significant role. Since the fracture sites are not exposed or visualized, the surgeon must plan each step of the surgical procedure to ensure that the operation proceeds smoothly, precious time is not wasted, and that unnecessary exposure to irradiation is avoided.

3

Patient evaluation

Proper assessment of the patient and the injury is necessary for correct decision making. This includes a detailed history, a careful physical examination, relevant laboratory tests, x-rays, and other ancillary imaging studies if indicated. Patient factors that need to be considered in the decisionmaking process include: Age Occupation General medical status and comorbidities Posttrauma status including hemodynamic stability Bone quality Preinjury functional status Patient compliance Future expectations This evaluation helps to decide whether the patient is a suitable candidate for surgery and is fit for anesthesia.

4

Fracture evaluation

For proper assessment of the fracture, good quality x-rays are required. Traction fi lms are useful in some instances. Other imaging studies that may be helpful include CT scans, 3-D reconstructions, MRI and vascular studies.

The following guidelines may be helpful in the decisionmaking process and preparation of a preoperative plan for MIPO.

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The fracture factors that should be taken into consideration include: Duration after injury Closed or open fracture Location—articular, metaphyseal, or diaphyseal Simple, wedge, or complex Condition of the skin and soft tissues Neurovascular injuries Associated fractures Associated injuries Good indications for MIPO include complex or multifragmentary fractures of the diaphysis and metaphysis and intraarticular fractures with extension into the diaphysis. Relative indications include simple diaphyseal fractures and certain open fractures.

Relevant implant templates of the correct scale A goniometer Colored felt-tipped pens and pencils The following planning techniques are commonly used: Direct overlay Overlay using the normal side Use of the physiological axes for articular fractures 5.1

This technique is usually used for diaphyseal fractures. Each fragment is traced onto a separate tracing paper. The bone is then rebuilt by gathering the fragments in a straight line, implying the central axis of the bone, followed by application of the appropriate implant template to draw the implant in an optimal position. 5.2

5

Graphic preoperative plan

One of the requirements of a good preoperative plan is to prepare a graphic representation of the fracture fragments, manipulating the fragments on paper to achieve a reduction, selecting the appropriate implants and superimposing them on the reduced fracture using templates, and reviewing the plan to see whether the desired end result is achieved. To prepare a graphic preoperative plan, the following are essential: X-rays of good quality, including views of the normal side if possible Additional imaging such as CT scans (especially for intraarticular fractures) Tracing paper (or transparencies)

Direct overlay

Overlay using the normal side

First, a tracing of the bone on the intact side is made and turned over. Then the fracture fragments are drawn separately and reassembled onto the drawing of the intact side. A template of the planned implant is superimposed to decide its correct location (Fig 8-2, Fig 8-3, Fig 8-4). 5.3

Use of physiological axes for articular fractures

Using a template or the x-rays of the opposite side, an outline of a physiological axis is drawn. Next the articular fragments are drawn in, respecting the physiological axis. Additional metaphyseal or diaphyseal fragments are also reassembled around the axis. Preoperative planning for articular fractures differs somewhat from diaphyseal fractures.

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8

Decision making and preoperative planning

For articular fractures, anatomical reduction of each fragment and stable fi xation with lag screws are vital to achieve a congruent joint surface. In this respect, CT scans are very useful to decide the direction of the lag screws, facilitating their insertion in the actual operation (Fig 8-8, Fig 8-12).

As MIPO is most often used for multifragmentary or complex diaphyseal fractures, the plate is commonly applied as a splint in the bridging mode.

In the case of multifragmentary diaphyseal fractures, the aim of surgery is to restore the correct length, alignment, and rotation of the bone rather than the anatomical reduction of the fracture fragments. Nevertheless, drawing in the anatomically reduced fragments in the preoperative plan helps selecting the appropriate plate and screws.

The selection of the appropriate length of the plate is a very important step in the preoperative plan. The length depends on the fracture pattern and the function that the plate is intended to serve.

6

Implants

The following factors should be considered in selecting the appropriate type of implant to be used in the MIPO procedure. 6.1

Type of plate

The types of plate used in MIPO include: Conventional plates (DCP or LC-DCP) or locking compression plates (LCP) Fixed angle implants Special anatomically preshaped plates 6.2

Plate function

The plate may function as a: Internal fi xator Bridging plate Compression plate Buttress plate Neutralization plate A combination of the above

6.3

Plate length

Two values have been used to determine the length of the plate to be used (Chapter 14 Femur, shaft: Fig 14-7): Plate span ratio The plate span ratio is the quotient of the plate length and overall fracture length. Empirically, the plate span ratio should be more than 2–3 in multifragmentary fractures and more than 8–10 in simple fractures. Plate-screw density The plate-screw density is the quotient formed by the number of screws inserted and the number of plate holes. Empirically, values below 0.5–0.4 have been recommended. This means that fewer than half of the plate holes should be occupied by screws. In general, the longest possible plates should be used since the longer the plate, the more stable and effective it is as a splint. There is no advantage in using shorter plates in MIPO since plates of all lengths are inserted through the same sized incisions. 6.4

Number of screws

The number and location of screws will depend on the biomechanical concept chosen and is described in detail in Chapter 2 (Mechanobiology). Basically two screws in each main fragment are the minimal number required to maintain 81

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the bone–implant construct from a purely mechanical point of view. However, loosening of one screw will cause overloading of the other screw, resulting in failure of the whole construct. It is generally recommended to use three screws in each main fragment in order to secure the fi xation. The number may, of course, be decreased for anatomical reasons (epi-/metaphyseal regions), and increased because of poor bone quality (osteoporosis). 6.5

Type of screw

Standard screws (cortex screws or cancellous bone screws) are used with conventional plates. With the LCP, four different types of screw can be used: Standard cortex screw Standard cancellous bone screw Self-tapping locking head screw Self-drilling and self-tapping locking head screw Standard screws are recommended in the following situations: When a screw needs to be inserted at an angle to avoid joint penetration. To apply compression, either as a lag screw for interfragmentary compression, or for eccentric screw insertion in the dynamic compression half of the combination hole of the LCP to achieve axial compression. As a reduction aid to draw the fracture fragments to the plate. For preliminary stabilization of the plate on the bone before the application of locking head screws (LHS). Self-tapping LHS are used for bicortical insertion when angular stability is required, especially in osteoporotic bones.

Self-drilling, self-tapping LHS are mainly used monocortically in the diaphyseal segment of bone in cases with excellent bone quality. They are also used when fi xing periprosthetic fractures. 6.6

Order of screw insertion

The order of screw insertion depends on the intended function of the plate and should be decided preferably during preoperative planning. Usually, the screw at the proximal end of the plate is inserted fi rst. The fracture is then reduced if it has not already been done and the screw at the distal end of the plate is next inserted. The quality of the fracture reduction is checked and, if satisfactory, the remaining screws are inserted according to the preoperative plan. If both standard screw and LHS are used in the same LCP, it is recommended to insert fi rst the standard screws. If the plate has been fi xed initially to the bone with LHS, and subsequent insertion of standard screws is needed, the LHS must be loosened before the standard screws are inserted. 6.7

Plate position

Since the implants are inserted without exposure of the bone or soft tissue, it is important to select a position for the plate that will avoid injuring any vital structure such as a major vessel or nerve during its insertion. 6.8

Plate contouring

Depending on the implant selected and the location and pattern of the fracture, it is often necessary to contour the plate. This is especially required when using conventional plates, in order to avoid malreduction of the fracture. Since the fracture site is not exposed in MIPO, plate contouring using templates

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8

Decision making and preoperative planning

is not possible. The contouring therefore needs to be done preoperatively, usually with the aid of plastic bone models or x-rays. The contoured plate is then sterilized for the operation. Fine adjustments of the plate contour may be done intraoperatively if necessary. An alternative would be to use special anatomically preshaped plates if available.

7

Reduction techniques

Indirect fracture reduction is used in MIPO. The method of indirect reduction should be planned so that the necessary equipment and manpower are available at the time of surgery. Once fracture reduction is achieved, the method of maintaining the reduction, such as with the use of the large distractor or external fi xator, should also be prepared.

9

In MIPO of multifragmentary diaphyseal fractures, the fracture is not exposed and anatomical reduction of the fracture fragments is not required. It is therefore difficult to judge whether the fracture is adequately reduced to the correct axes, rotation, and length of the limb during surgery, especially as the opposite limb is often covered with drapes and hence not available for comparison. Several methods, both clinical and radiographic, are available to check limb alignment and length (Chapter 10 Complications and solutions). These often have to be verified before the start of the operation. The surgeon should be familiar with these methods and prepare ahead so that during surgery obtaining satisfactory reduction can be checked.

10 8

Timing of surgery

If the condition of the soft tissue permits, MIPO should be carried out as soon as feasible. Otherwise, it would be better to delay the surgery until the soft-tissue condition is favorable. In the meantime, temporary immobilization with splinting, external fi xation, or traction may be required. The delay, however, should not be too long, as fracture reduction and correction of limb alignment and length become increasingly more difficult with time, and the surgery would become more invasive, technically difficult, and time-consuming.

Control of axes, rotation, and length during MIPO

Preparing the OR

To ensure that the operation proceeds according to plan, the OR must be adequately prepared. Planning for the OR should include: The correct operating table—traction or radiolucent Type of anesthesia Patient position Use of tourniquet Image intensifier Availability of the correct instruments and implants A good surgical team

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11

Alternative surgical tactic

Despite adequate preparations, there are occasions when surgery does not proceed according to plan and technical difficulties are encountered. When such a situation arises, the surgeon must be prepared to abandon the original plan and proceed with another method of treatment such as open reduction or switch to another type of fi xation device. A well-performed conventional open fracture fi xation is much better than a poorly executed MIPO with its attendant complications.

84

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8

12

12.1

Decision making and preoperative planning

Examples of cases with preoperative planning and the results

Tibia and fibula, proximal: complete articular fracture, articular multifragmentary—41-C3; 36-year-old male

Technique of the preoperative planning

a

b

Fig 8-1a–b

Fig 8-2

1. The intact side is traced and turned over (Fig 8-2). 2. Each fracture fragment is traced out (Fig 8-3) and superimposed on to the tracing of the intact side. 3. A template of the planned implant is superimposed and the location as well as the order of insertion of the screws is noted (Fig 8-4).

Preoperative x-rays (AP and lateral).

Drawings of the intact side (AP and lateral).

Fig 8-3

Drawings of the fragments from the injured side (AP and

lateral).

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12.1

Tibia and fibula, proximal: complete articular fracture, articular multifragmentary—41-C3; 36-year-old male

Surgical steps (Fig 8-4)

1

1

2, 5

Lag screw fi xation of articular fragments using 3.5 mm cortex screws.

4

2

A 9-hole lateral tibial buttress plate is used. The proximal part of the plate is fi xed with a 6.5 mm partially threaded cancellous bone screw. The most distal screw is then inserted.

4

Lag screw fi xation in the anteroposterior direction.

5

6

Other holes in the proximal part are filled with 6.5 mm partially threaded cancellous bone screws.

3

Fig 8-4

3

6

Two more screws are inserted in the distal holes.

Drawings of planned reduction and fi xation (AP and lateral).

a Fig 8-5a–b

b Postoperative x-rays (AP and lateral).

a

b

Fig 8-6a–b Follow-up x-rays; 13 months after MIPO (AP and lateral).

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8

12.2

Decision making and preoperative planning

Tibia and fibula, distal: complete articular fracture, articular simple, metaphyseal, multifragmentary—43-C2; 39-year-old female

a

b

Fig 8-7a–c

c

Preoperative x-rays (AP, lateral, and CT).

Surgical steps (Fig 8-8) 6

1

Lag screw fi xation of fibular fracture.

2

Fixation of distal fibula with an 8-hole one-third tubular plate used as neutralization plate.

8

3

After reduction of joint surface, lag screw is inserted from anterior to posterior. The direction is easily estimated by CT scan.

2

1

4

Contour a 9-hole LCP (bending and twisting). Check the location of the plate so as to secure an adequate length of the

9

most distal screw. Do not insert screw at this stage (an LHS is

5

to be used).

4, 7

3

5

Lag screw fi xation for the distal fracture to reduce the distal fragment against the plate (reduction screw).

From this stage on, the LHS are inserted: Fig 8-8 and CT).

Drawings of planned reduction and fi xation (AP, lateral,

6

Screw fi xation for the most proximal hole.

7

Screw fi xation for the most distal hole.

8

Two other screws are inserted in the proximal part.

9

One more screw is inserted in the distal part.

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12.2

Tibia and fibula, distal: complete articular fracture, articular simple, metaphyseal, multifragmentary—43-C2; 39-year-old female

a

b

c

Fig 8-9a–c a

Skin incision.

b–c

Postoperative x-rays (AP, lateral).

a Fig 8-10a–b

b Follow-up x-rays; 16 months after MIPO (AP and lateral).

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8

12.3

Decision making and preoperative planning

Tibia and fibula, distal: complete articular fracture, articular multifragmentary—43-C3; 56-year-old male

c

a

b

Fig 8-11a–d

d

Preoperative x-rays (AP, lateral, and CT scans).

Surgical steps (Fig 8-12) 1

Bridge plating for the fibular fracture.

2

First, the articular fragments are anatomically reduced and then temporarily fi xed with K-wires. Lag screw fi xation is then carried out using a 3.5 mm cortex screw in an anterior-

1

posterior direction. CT scan easily guides the direction.

5

3

Another lag screw is inserted proximally.

4

The articular block is connected with the diaphysis in

3

anatomical alignment. After the level of the plate is checked, one of the distal screws is inserted.

4

5 2

Fig 8-12

Check the alignment of the bone and the plate, then insert the screws in the proximal fragment. All other screws are inserted.

Drawings of planned reduction and fi xation (AP, lateral,

and CT scan).

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12.3

Tibia and fibula, distal: complete articular fracture, articular multifragmentary—43-C3; 56-year-old male

a

b

c

Fig 8-13a–c a

Intraoperative picture. MIPO is feasible even in the presence of an unhealed wound, which is a contraindication for conventional plating.

b–c Postoperative x-rays (AP, lateral).

a Fig 8-14a–b

b Follow-up x-rays; 9 months after MIPO (AP and lateral).

90

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8

Decision making and preoperative planning

91

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9

Postoperative management

1

Introduction

93

2

Analgesics

93

3

Antibiotic prophylaxis

93

4

Thromboembolism

94

4.1

Risk factors

94

4.2

Prophylaxis

94

4.3

Diagnosis

94

4.4

Treatment of deep vein thrombosis (DVT)

95

5

Wound care and drains

95

5.1

Wounds

95

5.2

Drains

95

6

Positioning and support of the affected limb

95

7

Mobilization and weight bearing

97

8

Postoperative x-ray examination

97

9

Discharge and follow-up observation

97

10

Implant removal

98

11

Suggested reading

99

92

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Authors

9 1

Tadashi TANAKA, Toru SATO

Postoperative management Introduction

In MIPO, the degree of analgesia required is usually less and of shorter duration because of the smaller wounds and lesser degrees of soft-tissue dissection.

In order to ensure a successful outcome in the operative treatment of fractures, a well-managed postoperative program is indispensable, as is a good preoperative plan and a carefully executed operation. Postoperative management should in principle aim at the prevention of fracture disease. Early mobilization helps to prevent joint contracture and disuse atrophy of the muscles. To realize this aim, the stability imparted to the fracture following the MIPO procedure must be adequate, otherwise the purpose of the fracture fi xation will be lost. The following factors must be taken into consideration for successful postoperative management.

2

Analgesics

Adequate analgesia reduces postoperative pain and increases patient comfort. This would encourage the patient to cooperate effectively in the postoperative rehabilitation program. In general, analgesics should be started well before pain becomes unbearable. Commonly used methods of analgesia include: Local anesthetic infi ltration around the surgical wounds Epidural analgesia Suppositories Intravenous/intramuscular injections Patient controlled analgesia (PCA) pump Oral analgesic agents

Analgesics should be started well before pain becomes unbearable.

3

Antibiotic prophylaxis

By its nature, MIPO limits soft-tissue exposure and dissection. This in turn reduces the risks of wound infection. Nevertheless, it is generally accepted that prophylactic antibiotics should be administered in implant surgery. The following points should be considered when using prophylactic antibiotics: It has been shown that Staphylococcus aureus is the most common infective agent in implant-associated bone infection. The prophylactic antibiotic used should therefore be sensitive against Staphylococcus aureus, taking into consideration the resistance pattern of the organisms in the hospital. First or second generation cephalosporins are generally suitable. The choice of antibiotic should also take into consideration its potential adverse effects on the patient as well as the patient’s history of drug allergy. The antibiotic should be administered intravenously within 1 hour of the start of the operation in order to obtain adequate inhibitory antibiotic levels in the surgical site. The usual practice is to administer the antibiotic at the time of induction of anesthesia. If a tourniquet is used, at least 10 minutes should be allowed between antibiotic administration and tourniquet inflation.

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The antibiotic may be administered as a single preoperative dose or over the course of 24 hours. There is no advantage in prolonging the prophylaxis beyond 1 day. The use of prophylactic antibiotics does not preclude the occurrence of wound infection. The surgeon must be aware of the symptoms and signs as well as the laboratory markers of wound infection and institute the appropriate treatment as soon as possible. Antibiotics should be administered as close as possible to the time of skin incision.

4

Thromboembolism

Venous thromboembolism constitutes an important cause of postoperative morbidity and mortality in orthopedic traumatology. It is therefore incumbent on the part of the surgeon to be familiar with the risk factors, preventive measures, diagnostic tests, and treatment strategies for this potentially fatal complication. 4.1

Pregnancy Estrogen use Fractures of the pelvis, proximal femur, and around the knee Multiple trauma 4.2

Prophylaxis

Thromboembolic prophylaxis, combined with efficient surgery and early mobilization, has been shown to have a lower risk of fatal pulmonary embolism. Thromboembolic prophylaxis should begin prior to or just after surgical intervention and should be continued for at least 10 days or, in the case of high-risk patients, for as long as 5 weeks. The common methods of prophylaxis include: Pharmacological agents, eg, warfarin, low-molecular-weight heparin, low-dose unfractionated heparin, fondaparinux, and acetylsalicylic acid. Mechanical devices, eg, external pneumatic compression boots and graduated compression stockings. Combined use of mechanical devices and pharmacological anticoagulant agents.

Risk factors

Important risk factors include: Advanced age History of previous venous thromboembolism Strong family history of thromboembolism History of cancer, myocardial infarction, congestive heart failure, chronic obstructive pulmonary disease, cerebrovascular accident (CVA) or paralysis Prolonged bed rest or delayed mobilization Obesity

Thromboembolic prophylaxis in the posttrauma patient can be difficult and a balance has to be made between the risks and benefits of the various methods. 4.3

Diagnosis

Constant vigilance is necessary for early diagnosis and treatment of deep vein thrombosis (DVT). Clinical signs such as calf swelling and tenderness or a positive Homans’ sign are neither specific nor reliable.

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9

Postoperative management

The following diagnostic tests are more accurate: Ascending venography Duplex ultrasonography Magnetic resonance venography

5.2

Drains are usually not required after MIPO of diaphyseal fractures. Drainage may be necessary when a joint is opened in articular fractures. When used, drains should preferably not be retained for longer than 48 hours unless there is copious drainage.

Of the three, magnetic resonance venography is the most reliable for detecting pelvic thromboses, which carry the highest risk of pulmonary embolism. 4.4

Treatment of deep vein thrombosis (DVT)

Once a diagnosis of DVT is made, a decision must be made whether treatment should be started or close surveillance continued. In general, clots proximal to the popliteal vessels should be treated because of the higher risk of embolization, whereas serial surveillance of calf DVT is reasonable as it does not usually propagate or embolize. Treatment of established thrombi includes the use of heparin, warfarin and inferior vena cava fi lters.

5

5.1

Drains

6

Positioning and support of the affected limb

Elevation helps to reduce swelling which can impede postoperative rehabilitation (Fig 9-1). Avoid pressure where nerves are vulnerable, eg, ulnar nerve at the medial humeral epicondyle and peroneal nerve over the fibular head. Judicious use of splints can prevent malpositions, eg, splinting the forearm and hand in the “intrinsic-plus” position helps to prevent fi nger contractures, and applying a U-slab to the foot can help prevent equinus deformity.

Wound care and drains

Wounds

In contrast to conventional osteosynthesis, the surgical wounds in MIPO are small. Nevertheless, they need proper attention. Wounds should be kept clean and dry. Soaked dressings need to be changed. If nonabsorbable suture materials are used, stitches should be removed after 12–14 days.

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a

b

Fig 9-1a–c

To reduce swelling, the affected limb is lifted above the

level of the heart.

c

a

Upper extremity.

b

Distal/midshaft femur.

c

Lower leg.

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9

7

Postoperative management

Physical therapy should start as soon as feasible following MIPO. Joints should be mobilized by active or active-assisted movements. Continuous passive motion may be helpful initially in restoring joint motion, especially after fi xation of articular fractures. In lower limb fractures, depending on the bone quality, stability of the fi xation and fitness of the patient, nonweight bearing or partial weight bearing (10–15 kg) walking exercises should be started early. Hydrotherapy is a useful way of providing relatively weightless and pain-free mobilization. Weight bearing up to 10–15 kg is started immediately after surgery.

8

was applied. Direct bone healing without callus is to be expected after interfragmental compression while indirect healing with callus formation is the norm after splinting using the bridging plate principle, which is usually the case after MIPO.

Mobilization and weight bearing

Postoperative x-ray examination

X-rays should be taken at the conclusion of the MIPO procedure or early in the postoperative period to document the quality of fracture reduction and fi xation. Thereafter, x-rays are repeated at 4–6 week intervals to monitor the progress of fracture union and to detect any evidence of implant loosening or breakage so that the appropriate remedial measures can be undertaken as soon as possible. It is important to remember that the follow-up radiographic fi ndings are closely related to the type of stabilization that

The radiographic findings are closely related to the chosen type of stabilization. If there are abnormal findings, one must change the postoperative care accordingly.

9

Discharge and follow-up observation

The patient is ready for discharge from hospital when the following conditions are fulfi lled: Postoperative x-rays are satisfactory. There is no symptom or sign of infection. The patient understands the purpose of his rehabilitation program and is able to comply. The patient is aware of what has been done and the possible complications that may arise. Post-discharge care providers are briefed on the aftercare program. Arrangements are made for further follow-up. Following discharge from hospital, the patient should be reviewed regularly to monitor the state of fracture healing, the progress made in rehabilitation, and any complication that might occur. Corrective action is taken as and when necessary. As the fracture heals, weight bearing is accordingly increased and the patient is encouraged to gradually resume work and his normal activities.

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10

Implant removal

For most patients, treatment is regarded as being completed when the implants are removed. Implant removal should only be undertaken after fracture healing is completed, usually after 1–2 years. Not all implants need removal. The disadvantages of implant removal include risks of anesthesia, infection, neurovascular injury, refracture, and additional cost. The incidence of refracture after removal of implants is considered lower after MIPO as compared to conventional compression plating, but no conclusive evidence has been obtained. Implant removal may be considered under the following circumstances: Young patient When the implant is in the lower limb When the implant is causing inhibition of limb function or irritation of the adjacent structures In the presence of infection. If stable, the implant may be left in place until fracture union occurs before it is removed.

To remove an implant in a case following MIPO, the screws are fi rst removed through the original skin incisions and the plate is then detached from the bone using an elevator inserted between them. If the plate cannot be removed by this method, a skin incision is made along the entire length of the plate (open method). Prior to the surgery, the patient should be informed that it is not always possible to remove all the implants. If there are broken screws, one should confi rm whether the patient wishes to have them removed. In general, broken screw residuals left in the bone need not be removed unless they protrude from the bone surface causing discomfort to the patient. It should also be noted that there are instruments for removal of damaged screws, consisting of special drill bits and conical extraction screws. The possibility of refracture following implant removal must always be borne in mind. The onset of pain following strenuous activities may indicate that refracture has occurred. To avoid this, the patient should be advised to avoid contact sports or heavy physical labor for 2–4 months after implant removal.

When implant removal is planned, it is necessary to inform the patient of the potential complications of its removal.

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9

11

Postoperative management

Suggested reading

Gatell JM, Garcia S, Lozano L, et al (1987) Perioperative cefamandole prophylaxis against infections. J Bone Joint Surg [Am]; 69(8):1189–1193. Geerts WH, Pineo GF, Heit JA, Bergqvist D, et al (2004) Prevention of venous thromboembolism. the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest; 126:338S–400S. Kaiser AB (1986) Antimicrobial prophylaxis in surgery. N Engl J Med; 315(18):1129–1138. Review. Siddiqui AU, Buchman TG, Hotchkiss RS (2000) Pulmonary embolism as a consequence of applying sequential compression device on legs in a patient asymptomatic of deep vein thrombosis. Anesthesiology; 92(3):880–882. Warwick D, Harrison J, Glew D, et al (1998) Comparison of the use of a foot pump with the use of low-molecular-weight heparin for the prevention of deep-vein thrombosis after total hip replacement. A prospective, randomized trial. J Bone Joint Surg [Am]; 80:1158–1166. Wells PS, Lensing AW, Hirsh J (1994) Graduated compression stocking in the prevention of postoperative venous thromboembolism. A meta-analysis. Arch Intern Med; 154:67–72.

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Complications and solutions

1

Introduction

101

2

Malalignment—prevention and correction

101

Malrotation

101

2.1

2.2

2.3

2.1.1

Femur

2.1.2

Tibia

Varus–valgus malalignment 2.2.1

Femur

2.2.2

Tibia

AP angulation: sagittal plane malalignment 2.3.1

Femur

2.3.2

Tibia

105

107

3

Limb length discrepancy

109

3.1

Prevention of shortening

110

4

Neurovascular injuries

110

4.1

Humerus

110

4.2

Femur

111

4.3

Tibia

111

5

Early postoperative complication

112

5.1

Infection

112

6

Late postoperative complications

114

6.1

Implant failure

114

6.2

Delayed union

114

7

Suggested reading

118

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Author

10 1

Theerachai APIVATTHAKAKUL

Complications and solutions Introduction

As in conventional plating, minimally invasive plate osteosynthesis (MIPO) is associated with complications. However, the complications encountered are somewhat different from those of conventional plating. Because in MIPO, the fracture sites are not exposed during reduction and plate application, malrotation, axial malalignment, and limb length discrepancy become more common, while infection, delayed and nonunion, and hence implant failure, are less frequent by virtue of the preservation of biology at the fracture site that is inherent in the MIPO technique. In order to reduce the occurrence of malrotation, axial malalignment, and limb length discrepancy, the following strategies are helpful: Always be mindful of the possibility of these complications occurring. Be familiar with the various methods of detecting their occurrence. Be familiar with the common pitfalls and the best ways of prevention.

In general, the complications in MIPO may be divided into three phases: Intraoperative complications: rotational and axial malalignment, limb length discrepancy, and neurovascular injuries Early postoperative complication: acute infection Late postoperative complications: implant failure, delayed union, and nonunion

2

2.1

Malrotation

This complication commonly occurs in MIPO, but is often overlooked as it is not always obvious in plain x-rays. Gross malrotation can be recognized clinically, but lesser degrees are more difficult to detect. Hence it is important to be familiar with the various methods of evaluating rotational deformities and the steps necessary to prevent their occurrence. 2.1.1

Even with the best efforts complications do sometimes occur. When that happens, it is essential that they are discovered and corrected early, preferably intraoperatively, or, if that is not possible, within 2 weeks, and certainly before fracture union takes place. Correction becomes much more difficult and complicated once malunion has occurred and especially if adaptive changes in the anatomy have taken place.

Malalignment—prevention and correction

Femur

In the femur, malrotation occurs most commonly with proximal femoral and subtrochanteric fractures. The deforming forces of the iliopsoas, gluteus medius, and short external rotators pull the proximal fragment into flexion, abduction, and external rotation, respectively. Performing fracture reduction and fi xation without concern for these deforming forces will lead to malreduction, including malrotation (see Fig 10-5).

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There are several intraoperative methods of assessing whether a proximal femoral fracture is fi xed in the correct rotational alignment. These methods may be clinical or radiological: Hip rotation test (Fig 10-1) The lesser trochanter shape sign (Fig 10-2) The cortical step sign (Fig 10-3) The diameter difference sign (Fig 10-4) The hip rotation test is a clinical method that compares hip rotation with that of the contralateral unaffected side. This technique is easily performed and it is radiation-independent. However, the clinical judgment may be wrong, and it is also dependent on the position of the pelvis, which may change during the course of the operative procedure.

The hip rotation test cannot be used if the patient is on a traction table. In such cases, radiological methods of assessing rotation will have to be used. These include the lesser trochanter shape sign, cortical step sign, and diameter difference sign. For multifragmentary fractures of the proximal femur with an intact lesser trochanter, the lesser trochanter shape sign is most useful. When the lesser trochanter is fractured, the rotation should be assessed by clinical means. In simple transverse or oblique fractures, the correct rotation may be judged by the thickness of the cortices of the proximal and distal fragments (cortical step sign). The cortical step sign and the sign of diameter difference cannot be used in multifragmentary fractures as the area of comminution makes comparison of the cortical step and diameter impossible. In the midshaft and distal femur, the deforming forces are less, and malrotation is therefore less common. However, the rotation after fi xation still has to be checked intraoperatively, both clinically and radiographically.

Fig 10-1

The rotation of the femur can be checked by the hip rota-

tion test. Measure with the patient lying on his back, with hip and knee both flexed at 90º.

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10

Complications and solutions

Fig 10-3

Cortical step sign.

In the presence of a considerable rotational deformity, this can be diagnosed by the a

b

Fig 10-2a–d

c

d

difference in the thickness of the cortices.

The lesser trochanter shape sign: an intraoperative radiological assessment of

rotation in which the shape of the lesser trochanter is compared with that of the contralateral side. a

Before positioning the patient, the shape of the lesser trochanter of the intact opposite side (patella facing anteriorly) is stored in the image intensifier.

b

Before fi xing the second main fracture fragment, the patella is oriented anteriorly and the proximal fragment is rotated until the shape of the lesser trochanter on the ipsilateral side matches the shape of the contralateral lesser trochanter.

c

In cases of external malrotation the lesser trochanter is smaller and partially hidden behind the proximal femoral shaft.

d

In cases of internal malrotation the lesser trochanter appears enlarged. Fig 10-4

Diameter difference sign.

This sign is positive at levels where the bone cross-section is oval rather than round. With malrotation, the diameters of proximal and distal main fragments appear to be of different sizes.

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Case: femoral malrotation

a

b

c

d

e

Fig 10-5a–f a

A 40-year-old male fell from a height and sustained a multifragmentary subtrochanteric fracture of the right femur.

b

The fracture was stabilized with a 95º condylar blade plate by the MIPO technique using a traction table.

c

Postoperatively, the right lower extremity demonstrated internal malrotation deformity.

d

X-rays after revision of the distal screws and external rotation of the distal fragment.

f

e

Clinical result after revision of malrotation.

f

X-rays after 6 months show solid fracture union.

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10

Complications and solutions

Prevention of femoral malrotation

Bear in mind that this complication can occur and it is preventable. It is advisable to use a radiolucent operating table rather than a traction table. Although the traction table can maintain the length of the limb, the rotation cannot be assessed clinically during the operation. If the traction table is used, the lesser trochanter shape sign has to be used for comparison with the uninjured limb. If the radiolucent operating table is used, the rotation is checked after preliminary fi xation of both proximal and distal fragments by flexing the hip and knee to 90° (hip rotation test). Drape both lower limbs free if possible, to compare the rotation and to measure the length. Early revision or correction of any malrotational deformity is essential. It is much easier than correcting a malunited fracture as it is less time consuming and the patient can have early return to function. 2.1.2

Tibia

Malrotation of the tibia is easier to assess because there is less soft-tissue cover and the anteromedial surface of the tibia is easily palpated. Tibial rotation can be determined both clinically and radiographically by comparison with the uninjured limb. Clinical assessment of tibial rotation is performed by flexing the hip and knee to 90° while keeping the ankle dorsiflexed. The rotation of the tibia is then compared with the uninjured side by noting the position of the feet, as well as the range and symmetry of foot rotation. Rotational malalignment of the tibia occurs most commonly after MIPO of distal tibial fractures due to the peculiar anatomy of that part of the bone. The distal tibia is flared medially and the smooth anteromedial surface to which the plate is

applied twists posteriorly to end at the medial malleolus. This flare and twist must be taken into consideration when the plate is contoured, or it will result in malrotation and axial malalignment. Prevention of tibial malrotation

Precise plate contouring is necessary for MIPO of proximal and distal tibial fractures when using the DCP. The precontoured plate has to be placed in the correct position. Check the rotation of the tibia clinically by flexion of the hip and the knee to 90° while keeping the ankle dorsiflexed. 2.2

Varus–valgus malalignment

Frontal plane malalignment occurs more commonly in metaphyseal fractures. This is because the metaphyseal cortex is not straight as in the diaphysis. The plate thus needs to be precontoured or a precontoured anatomical plate may be used. For example, when the 95° condylar plate is used for fi xation of proximal or distal femoral fractures, and the blade is inserted in the correct position, indirect reduction of the shaft to the plate will usually provide correct frontal plane alignment. This concept can also be applied to the proximal and distal tibia using anatomically precontoured plates, such as the lateral tibial head buttress plate or the proximal lateral tibial LISS plate. An intraoperative technique for checking frontal plane malalignment of the lower extremity is the cable technique. In this technique, a cautery cable is spanned between the center of the femoral head and the center of the tibial plafond. The position of the cautery cable relative to the center of the knee joint under image intensification indicates the axial deviation in the frontal plane. This is a reliable method but it is radiationdependent (Fig 10-6). 105

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Animation

1

3

2

Fig 10-7

Cautery cord spans from anterior

superior iliac spine (ASIS) to the first web space.

Fig 10-6

Cautery cable technique using image intensifier for check-

2

In a similar way the center of the ankle joint is marked. An

ing alignment in the frontal plane: The knee is fully extended and the

assistant now spans the cautery cable between these two sur-

patella must face anteriorly.

face markings.

1

With the image intensifier beam strictly vertical, the center of the

3

When the knee joint is viewed with the image intensifier, the

femoral head is centered on the screen. A pen then marks the

cable should run centrally. Any deviation of the projected

center of the femoral head on the patient’s skin.

cautery cable from the center of the joint indicates the axial deviation in the frontal plane.

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10

Complications and solutions

A variation of the cable technique spans the cautery cable from the anterior superior iliac spine (ASIS) to the fi rst web space of the ipsilateral foot. If the frontal plane alignment is correct, the cable should pass through the center of the knee joint (Fig 10-7). This technique is easier but less precise and many errors can occur depending on the foot rotation, ankle position, and position of the hip in abduction or adduction. 2.2.1

Femur

When applying MIPO to fi x a proximal femoral fracture with a 95° condylar plate, varus malalignment can occur during plate insertion. The chiseled canal is fi rst prepared using standard AO techniques. The 95° condylar plate is then slipped into a submuscular tunnel alongside the lateral cortex of the femur with the blade pointing laterally. The blade is then turned medially for insertion into the prepared canal. However, the direction of the blade and canal frequently do not meet. The blade has a tendency to go in the wrong direction and create a false passage, resulting in the proximal fragment being fi xed in the varus position. The reason for this is that the lateral thigh muscles tend to push the blade plate into a varus position. This complication can be avoided by inserting a joystick into the proximal fragment to bring it into proper alignment to the blade during blade insertion (Chapter 13 Femur, proximal: Fig | Anim 13-11). Also, the guide pin used initially to guide the direction of the seating chisel should be left in place to guide the direction of blade insertion. Another useful tip is to use a short blade of 50–60 mm length which makes it easier to turn into the prepared canal. 2.2.2

then moved distally to take an AP view of the ankle joint. If the K-wire beneath the ankle joint is also parallel to the ankle joint line, there is no varus or valgus malalignment of the tibia (Chapter 17 Tibia and fibula, shaft: Fig 17-11). The unilateral external fi xator with the two Schanz screws constructed in parallel can also be applied using the same principle (Chapter 17 Tibia and fibula, shaft: Fig 17-12).

2.3

AP angulation: sagittal plane malalignment

2.3.1 Femur Femur, proximal

AP angulation at the proximal femur tends to occur with the 95° condylar plate which needs 3-D plate insertion. On the other hand, the dynamic condylar screw (DCS) needs only two dimensions, and any AP angulation is easily corrected by turning the plate–screw construct into the correct position to align with the femoral shaft. In proximal femoral fractures with the lesser trochanter attached to the proximal fragment, the proximal fragment has a tendency to go into flexion, abduction, and external rotation. Control of the proximal fragment into the normal AP and lateral position, as seen on the image intensifier, is necessary. A joystick is inserted into the proximal fragment and manipulated to counter the muscle pull. During chiseling of the blade canal and the subsequent insertion of the 95° condylar plate, the proximal fragment has to be kept in this position, or malalignment may occur.

Tibia

Varus or valgus malalignment of the tibia can be evaluated by using a tibial alignment grid which has multiple parallel K-wires 3–5 cm apart mounted between two plastic plates. The grid is placed beneath the tibia extending from the knee to the ankle. An AP view of the knee is taken with the image intensifier, with a K-wire parallel to the knee joint. The C-arm is

Femur, shaft

AP angulation at the diaphysis is directly controlled by lateral fluoroscopic guidance. To facilitate this, the operation should be performed with the patient in supine position on a radiolucent operating table, with a support under the thigh and the uninjured limb placed on a leg holder. 107

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Because the femur has an anterior bow, fi xation of a simple fracture with a long straight plate positioned on the center of the lateral cortex tends to produce some AP angulation at the fracture site. It is advisable to fi x the ends of the plate in the center of the lateral cortex, while the holes which are close to the fracture should be fi xed more posteriorly in order to reduce the fracture gap and avoid AP angulation of the fracture (Fig 10-8).

a

In multifragmentary fractures, the angulation at the fracture site is usually compensated by the multiple fragments and AP angulation at the fracture site is usually not a problem (Fig 10-9). Another technique to prevent AP angulation and to accommodate the anterior bow of the femoral shaft is to slightly bend a long plate into a convex shape to match the curve of the bone. This contoured plate is then positioned on the anterolateral cortex of the femur and fi xed with screws directed from an anterolateral to a posteromedial direction at about 30º–40º from the horizontal. One problem associated with correction of AP angulation is shortening of the bone due to overlapping of the fracture ends. In simple fractures, when the plate is fi xed temporarily with one screw in each fragment, the angulation can only be corrected if the fractured bone is of the correct length or slightly distracted. If there is overlapping of the fracture ends, it may not be possible to reduce the fracture back to the correct position.

b

Femur, distal c Fig 10-8a–c

Restoring the anterior bowing of the femur—an un-

favorable plate position can result in sagittal plane angulation. a

Fixing the proximal end of the plate too close to the posterior

The most common sagittal plane malalignment occurring after fi xation of fractures in the distal femur is posterior angulation. The distal fragment is usually displaced posteriorly by the pull of the gastrocnemius muscle. Flexion of knee up to 60º with a posterior support is necessary to relax the pull of

margin of the lateral cortex will result in anterior displacement of the distal end of the plate away from the bone. b

Fixing the whole length of the plate in the center of the lateral cortex will result in posterior angulation and loss of the anterior bowing.

c

It is advisable to fi x the ends of the plate in the center of the lateral cortex, and the holes which are close to the fracture should be fi xed more posteriorly to reduce the fracture gap and

Fig 10-9

avoid sagittal plane angulation.

chances of angulation at the fracture site.

Multiple fragments in comminuted fractures reduce the

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10

Complications and solutions

gastrocnemius. To manipulate the distal fragment into the correct position, a joystick is inserted into the anterior aspect of the distal femur, preferably in the extraarticular portion, and then rotated distally to realign the distal fragment to the proximal fragment (Chapter 7 Reduction techniques: Fig | Anim 7-3). The posterior cortex of the short distal fragment and the posterior cortex of the proximal fragment must be aligned. The lateral view is checked with the image intensifier. 2.3.2

The limb length can be assessed with or without the use of an image intensifier. The simple technique of using a cautery cable to measure the length of the femur from the ASIS to the upper pole of the patella, and measuring the length of the tibia from the tibial tubercle to the tip of the medial malleolus can be used. However, significant swelling in the thigh or knee may lead to measurement error. The length can also be assessed with the image intensifier using the meterstick technique (Fig 10-10).

Tibia

The tibial shaft is the straight part of the bone. Angulation can be detected clinically by palpation of the anterior tibial crest or the posteromedial crest. It is not difficult to reduce a multifragmentary tibial fracture, and align the plate in the center of the tibia in both the proximal and distal main fragments, which means the AP angulation is correct. The alignment is then confi rmed with a lateral x-ray. In the distal tibia, angulation can occur if the plate is not correctly precontoured.

3

Limb length discrepancy

Limb length discrepancy (LLD) occurs more often in the femur than the tibia. As the femur is covered by bulky muscles, its length is more difficult to evaluate than the tibia. The most common form of LLD is shortening, while distraction of the fracture is rarely seen. Multifragmentary fractures and long spiral fractures are sometimes difficult to evaluate for the correct length using the image intensifier. In such cases, the length may be measured clinically. Preoperative measurement of the length of the uninjured limb should be done as a reference. Alternatively, the contralateral uninjured limb is prepared and draped free during surgery so that it is available for comparison with the injured limb.

Fig 10-10

The limb length can be assessed with the image intensi-

fi er using the meterstick technique.

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Shortening may be caused by: Muscle contraction, especially if surgery is delayed. This shortening can be prevented by preoperative skeletal traction. Soft-tissue swelling and hematoma formation, which may produce a hydraulic effect that can resist the traction force. Sagittal plane angulation, which is frequently seen in simple fractures. After preliminary fi xation of the plate with one screw in each main fragment, the fracture is checked in an AP x-ray. The fracture may appear as if the bone ends are in contact with each other, thus giving the false impression that limb length is correct when in fact there is limb shortening due to AP angulation at the fracture site which will show up only on a lateral x-ray. Furthermore, correction of this AP angulation with restoration of correct limb length will be difficult as there is no space for manipulation unless the fracture is fi rst distracted to correct length before the AP angulation can be corrected. 3.1

Prevention of shortening

Check the length after fi xation by clinical or radiological means. Preoperative assessment of the length of the uninjured limb should be carried out for reference. Traction, which can be obtained in several ways. Manual traction is simple but maintaining the length during the fi xation procedure is difficult. A distractor or push–pull device (Chapter 3 Instruments) is helpful to maintain the length but needs more working space.

4

Neurovascular injuries

Neurovascular injuries, though uncommon, can result in significant morbidity. These complications are best prevented by understanding the anatomy, careful dissection, and gently protecting the neurovascular structures during surgery. 4.1

Humerus

Neurovascular injuries occur most commonly in MIPO of humeral fractures. During MIPO of humeral shaft fractures by the anterior approach, the radial nerve is at risk at three locations. In the proximal and distal incisions, the radial nerve is at risk if Hohmann retractors are used for muscle retraction. The radial nerve can be injured at the proximal incision by the tip of the medial Hohmann retractor. At the distal incision, the radial nerve can be injured by the lateral Hohmann retractor which may compress the nerve. In order to avoid this, Army Navy retractors should be used instead of Hohmann retractors (Fig 10-11). The radial nerve is also at risk as it runs along the posterior aspect of the middle third of the humerus during drilling or screw insertion in the anterior to posterior direction. Whenever possible, no screw should be inserted in this zone. If absolutely indicated screws should be inserted monocortically (Fig 10-12). The musculocutaneous nerve which lies between the biceps and the brachialis muscles needs to be identified and protected before preparing the tunnel for the plate. Another MIPO method to fi x humeral fractures consists of the use of a helical plate. This implant is introduced from the proximal humerus via a deltoid splitting approach and its helical configuration will then guide it with a twist to lie on the anterior aspect of the humeral shaft. There is a risk of injury to the axillary nerve with this approach (Chapter 11 Humerus, proximal: Fig 11-5). To avoid this, the deltoid muscle should not

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10

Complications and solutions

be split more than 5 cm distal to the acromion process, and the plate should be slipped close to the bone deep to the axillary nerve.

4.2

Femur

MIPO of the femur is safe and can be done on the lateral surface of the femur from the greater trochanter to the lateral femoral condyle. There is no structure at risk during MIPO of the femur. 4.3

Tibia

MIPO of the tibia on the medial side carries a risk of saphenous nerve injury at the proximal part and saphenous vein injury at the distal part (Fig 10-13). However, these complications do not result in any significant morbidity. MIPO on the lateral side of the tibia is safe in the proximal third and midshaft. In the distal third, the anterior tibial artery along with the deep peroneal nerve can be injured by the plate and the screws (Chapter 17 Tibia and fibula, shaft: 2.1 Structures at risk). These structures have to be identified before tunneling or plating. Fig 10-11

The radial nerve is vulnerable in the proximal and distal

incisions used for MIPO of the humeral shaft. To avoid injury to the radial nerve in these locations, retraction should be carried out with Army Navy retractors instead of Hohmann retractors.

Fig 10-12

Anteroposterior screw insertion in the midshaft of the

Fig 10-13

MIPO of the tibia on the medial side carries a risk of

humerus should be avoided if possible to prevent injury to the radial

saphenous nerve injury at the proximal part and saphenous vein

nerve at this level. If absolutely necessary, monocortical screws

injury at the distal part.

should be used.

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5

5.1

Early postoperative complication

Infection

The goal of the MIPO technique is to preserve the vascularity of the fractured bone and the surrounding tissue in order to promote fracture healing and reduce the rate of infection. The infection rate is low compared with conventional techniques. Even when MIPO is used for the defi nitive treatment of Gustilo type III open fractures or closed fractures with severe softtissue injuries, the infection rate remains low provided proper precautions are taken. Initial wound debridement followed by external fi xation should be carried out. Only when the softtissue condition is good enough and there is no sign of infection, the MIPO technique can be utilized as defi nitive treatment. The management of these difficult fractures requires much experience as well as careful preoperative planning from the fi rst step of external fi xation to the defi nitive fracture fi xation. For example, in cases of open fractures of the femur in which the plan is for defi nitive fi xation using the MIPO technique, after initial wound debridement, the fractures are reduced and the reduction maintained with an external fi xator. This should be placed on the anterior aspect of the femur so that when conditions are ready for MIPO to be carried out, the plate can be slipped along the lateral aspect of the femur without any interference from the external fi xator (Fig 10-14).

plating (eg, femur) is usually more difficult to diagnose, as the clinical symptoms of pain and fever may appear late. Laboratory fi ndings (raised erythrocyte sedimentation rate, C-reactive protein, and leukocyte count) often lead to the diagnosis. If there is any doubt about the presence of infection, early wound exploration is indicated. General principles of treatment of acute infection include early detection, drainage with debridement, antibiotics, and determination of implant stability. Infection after MIPO is usually not as bad as after conventional plating, as the infection is usually localized to the area of the plate. The soft tissue and periosteum outside the area of the plate are well preserved and the bone has a better chance to heal. The MIPO wound needs to be extended to allow drainage as well as adequate debridement of the necrotic bone and soft tissue around the area of the plate. The wound can be treated by open or closed wound treatment. The stability of the fi xation is assessed. The fi xation device can be left in place if it provides stability. Fracture healing can take place despite the presence of a low-grade infection. Implants are removed after solid bridging callus is seen. If the implant becomes loose, it must be removed and the fracture then stabilized with an external fi xator.

Infection following the MIPO technique is not common. However, when it occurs, early detection and treatment are essential. Subcutaneous and submuscular plating produce different clinical symptoms and signs when infection occurs. In the case of subcutaneous plating (eg, medial tibia), subcutaneous swelling, inflammation, and fever allow acute infection to be detected early. However, infection after submuscular 112

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10

Complications and solutions

Case: infection

a

b

c

d

Fig 10-14a–h a

A 36-year-old male involved in a motorcycle accident with a

c

Postoperative x-rays.

Gustilo type III open fracture of the left tibia. X-rays show the

d

10 days after surgery, the soft-tissue condition has improved. The fracture was then stabilized by the MIPO technique.

42-B wedge fracture. b

Debridement of the open fracture was done. The fracture was initially stabilized with an external fi xator.

e

Postoperative x-rays after MIPO using a 14-hole narrow DCP.

f

Purulent discharge was seen at the proximal

f

incision. g

Drainage and debridement was done and the wound was left open.

h

X-rays 5 months after surgery: The fracture has

e

g

h

healed with callus bridging the posterior cortex.

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6

6.1

Late postoperative complications

Implant failure

There are two types of implant failure: screw breakage and plate breakage. Most cases of implant failure following conventional plating techniques are due to plate breakage (Fig 10-15); screw breakage is rather uncommon. In contrast, with the MIPO technique, plate breakage is less common than screw breakage (Fig 10-16). The plate is fi xed to each main fragment by three to four screws which provide adequate stability for indirect bone healing to occur. Long plates, bridging a comminution with fi xation on either end of the bone, will undergo considerable deformation forces. As bending stress is distributed over a long segment of the plate, the stress per unit area is low, which reduces the risk of plate breakage. The three or four screws in each main fragment also absorb the load but the diameter of the screws is small, resulting in more frequent screw breakage from high stress. The healing of fractures treated with biological plating and indirect reduction technique is faster than with conventional plating, so implant failure is uncommon. However, if a large bone gap remains after MIPO, there is a higher risk of implant failure. In such cases, early cancellous bone grafting 6–12 weeks after surgery is advisable, especially if no callus formation is seen on the follow-up x-rays. In general, primary bone grafting is rarely needed in closed fractures treated with the MIPO technique. It is advisable only in cases of open fractures that have significant bone loss.

In multifragmentary fractures, it is preferable to use a longer plate that has a plate span ratio of more than 2–3 that of the fracture length (the quotient of the plate length and overall fracture length), while in simple fractures, the plate span ratio should be more than 8–10. Prevention of implant failure

Understand the concept of a bridging plate, MIPO technique, strain theory, and the biomechanics of plate and screw fi xation with this technique. Use as long a plate as possible and fi x both ends with adequate number of screws with at least three or four screws in each main fracture fragment. In severe soft-tissue injuries, open fractures, or fractures with large bone gaps, it is advisable to perform early bone grafting, usually 6 weeks after surgery if no sign of bridging callus is seen. 6.2

Delayed union

In the MIPO technique, it is generally accepted that the need for primary bone grafting for multifragmentary fractures is unnecessary. Biological plating or bridge plating is superior as regards bone healing than conventional plating. However, delayed union can occur even with the MIPO technique (Fig 10-17). The cause of delayed union may be the severity of the initial soft-tissue and bone injury (patient factor) which is uncontrollable. Another cause may be technical errors (surgeon factor) which can be avoided.

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10

Complications and solutions

Case: broken plate

a

b

c

Fig 10-15a–e a

A 30-year-old male met with a motorcycle accident. X-rays show a multifragmentary subtrochanteric fracture.

b

The fracture was stabilized with a 95° condylar plate. The lateral x-rays show a large fracture gap with gross displacement of the fracture fragments (white arrow).

c

The patient was lost to follow-up and came back only after 4 months with a broken plate and screw, and a nonunion at the area of the large gap. However, the distal part of the multifragmentary area

d

shows bridging callus.

e d

The x-rays show the fracture after revision of the plate and screws and autogenous bone grafting.

e

X-rays after 1 year show solid union of the fracture.

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Case: screw failure

Fig 10-16a–f a

b

c

d

a

A 35-year-old male with polytrauma, including head and chest injuries and a multifragmentary femoral shaft fracture.

b

The femoral fracture was stabilized with a broad DCP with improper application of the MIPO technique. The x-rays show the fracture fi xed with a 12-hole broad DCP with only two screws in each fragment.

c

2 weeks postoperatively, the screws failed.

d

X-rays after implant removal and revision using a 16-hole plate fi xed with three screws in each fragment.

e

f

e

X-rays 2 months postoperatively.

f

Fracture healing 6 months postoperatively.

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10

Complications and solutions

Case: delayed union

a

b

c

d

Fig 10-17a–e a

A 42-year-old male sustained a motorcycle accident with a multifragmentary subtrochanteric fracture.

b

The fracture was stabilized with a 95° condylar blade plate by the MIPO technique.

c

Postoperative x-rays show a large fracture gap and angulation.

d

Postoperative x-rays after 6 weeks show large fracture gap with small amount of callus formation.

e

e

X-rays 6 months after bone grafting show solid union of the fracture and two broken screws in the distal fi xation.

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Delayed union caused by technical errors by a surgeon may be: Malalignment of the fracture in the sagittal or frontal planes resulting in large residual bone defects that cannot heal by callus formation. Technical errors from the tunneling step. The correct positioning of the tunneler creates the tunnel over the periosteum and preserves the vascularity surrounding the fracture. An incorrect plane of dissection which strips the periosteum, as in the conventional technique, will destroy the bone vascularity and hence disturb the healing process. Repeated tunneling also damages the periosteal blood supply. The vascularity can be destroyed iatrogenically by excessive manipulation to achieve the unnecessary anatomical reduction of the multifragmentary zone, cerclage wiring, or lag screw fi xation. Markedly displaced fracture fragments or scattered bone pieces into the muscle may result in large gaps.

7

Suggested reading

Apivatthakakul T, Arpornchayanon O, Bavonratanavech S (2005) Minimally invasive plate osteosynthesis (MIPO) of the humeral shaft fracture. Is it possible? A cadaveric study and preliminary report. Injury; 36(4):530–538. Gautier E, Sommer C (2003) Guidelines for the clinical application of the LCP. Injury; 34(2):B63–B76. Kinast C, Bolhofner BR, Mast JW, et al (1989) Subtrochanteric fractures of the femur. Results of treatment with the 95 degree condylar blade-plate. Clin Orthop Relat Res; 238:122–130. Krettek C, Miclau T, Grun O, et al (1998) Intraoperative control of axes, rotation and length in femoral and tibial fractures Technical note. Injury; 29(3):C29–C39. Ochsner PE, Müller U (2000) Acute infection. Ruedi T, Murphy W, (eds) AO Principles of Fracture Management. Stuttgart New York: Georg Thieme Verlag, 733–751.

Prevention of delayed union

Employ indirect methods of fracture reduction. Avoid malalignment in the frontal and sagittal planes. Avoid large residual bone gaps at the fracture site. Prepare the submuscular tunnel for the plate in the correct plane over the periosteum. Avoid repeated tunneling. Avoid excessive direct manipulation of the fracture zone. If indirect reduction is unsuccessful, careful limited open reduction should be considered.

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Cases

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11

Humerus, proximal

1

Introduction

121

Cases

1.1

Classification

121

11.1

1.2

Indications and contraindications for MIPO

121

2

Surgical anatomy

122

3

Preoperative assessment

124

4

Preoperative planning

125

5

OR set-up

126

5.1

Anesthesia

126

5.2

Patient positioning and image intensifier

126

5.3

Implants and instruments

126

6

Operative procedure

127

6.1

Surgical approach

127

6.2

Fracture reduction

127

6.3

Plate insertion and fixation

128

7

Postoperative care

129

8

Pitfalls

129

9

Pearls

129

10

Suggested reading

130

Humerus, proximal: extraarticular unifocal fracture, nonimpacted, metaphyseal—11-A3

11.2

131

Humerus, proximal: extraarticular unifocal fracture, nonimpacted, metaphyseal—11-A3 with diaphyseal involvement

137

Teaching video on DVD-ROM 11

Humerus, proximal—anterolateral approach

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Authors

11

1

Merng Koon WONG, Suthorn BAVONRATANAVECH

Humerus, proximal

Introduction

Up to 80% of fractures of the proximal humerus can be treated conservatively. This is fortunate as the surgical management of these fractures can be difficult. The difficulties encountered include: Fracture reduction Exposure Fracture stabilization Increased risk of avascular necrosis Osteoporosis Prolonged rehabilitation with likelihood of pain and stiffness in the shoulder MIPO using indirect reduction and modern day implants such as locking compression plates (LCP) may help to address some of these concerns. However, not all proximal humeral fractures can be managed by these minimally invasive techniques, but when applicable, they can lead to improved outcomes. 1.1

Classification

a

1.2

c

Fig 11-1a–c a b c

11-A extraarticular unifocal fracture. 11-A1 tuberosity 11-A2 impacted metaphyseal 11-A3 nonimpacted metaphyseal

a

b

c

Fig 11-2a–c a

The Müller AO Classification is used for classification of proximal humeral fractures (Fig 11-1, Fig 11-2, Fig 11-3). The proximal humerus is designated by the number 11. Type A fractures are extraarticular unifocal, Type B are extraarticular bifocal and Type C fractures are articular fractures.

b

b c

11-B extraarticular bifocal fracture. 11-B1 with metaphyseal impaction 11-B2 without metaphyseal impaction 11-B3 with glenohumeral dislocation

Indications and contraindications for MIPO

One has to be selective when applying MIPO techniques for fractures of the proximal humerus.

a

b

c

Fig 11-3a–c

Displaced surgical neck fractures (11-A3), especially those with extensions into the shaft, surgical neck fractures with avulsion of the greater tuberosity (11-B1 and 11-B2), and

a b c

11-C articular fracture. 11-C1 with slight displacement 11-C2 impacted with marked displacement 11-C3 dislocated 121

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1

Introduction

(cont)

valgus impacted fractures (11-C1 and some 11-C2) are good indications because the connections to the rotator cuff and also the soft tissue and periosteal attachments between the fracture fragments usually remain intact in these fractures. This allows indirect fracture reduction using the principle of ligamentotaxis and at the same time ensuring the preservation of blood supply and biology.

2

Less suitable are those fractures with severe lateral displacement of the head fragment (some 11-C2) and severely displaced fracture dislocations (11-C3), unless they can—in younger patients—be satisfactorily reduced by closed methods and primary prosthetic replacement is not really suitable. Severe osteoporosis is a relative contraindication, as in these cases even angular stable implants may not provide the required stability to ensure fracture union.

Surgical anatomy

The axillary nerve runs along the deep surface of the deltoid muscle about 6 cm from the acromion and is at risk in a transdeltoid lateral approach used as an entry portal for the introduction of the plate in a craniocaudal direction. In order to avoid injury to the axillary nerve, the deltoid split should not extend for more than 5 cm beyond the lateral edge of the acromion. An additional precaution would be to place a “safetysuture” at this level to prevent propagation of the deltoid split. Further, during insertion of the implant through this approach, the plate should be kept close to the bone to avoid trapping the axillary nerve between the plate and the bone. The radial nerve lies close to the lateral aspect of the distal humerus. A long plate applied laterally would risk injuring the radial nerve at the distal part of the humeral shaft where it pierces the lateral intermuscular septum distal to the deltoid insertion. Also, the nerve is at risk of compression by the tip of a Hohmann retractor applied to the lateral aspect of the humeral shaft to expose the distal humerus when a long plate is applied for osteosynthesis. Because of this, it is safer to use Army Navy retractors for this purpose rather than Hohmann retractors.

The tendon of the long head of the biceps lies in the groove between the greater and lesser tuberosities of the humerus and serves as an important landmark. It may also be trapped between the bony fragments in displaced proximal humeral fractures and prevent closed fracture reduction. Running alongside the tendon of the long head of the biceps in the intertubercular groove is the lateral ascending branch of the anterior humeral circumflex artery carrying the main blood supply to the upper part of the humeral head. Damage to this artery can lead to avascular necrosis of that part of the humeral head (Fig 11-4). Fractures of the anatomical neck of the humerus should be distinguished from surgical neck fractures. In anatomical neck fractures the blood supply to the main head fragment is frequently disrupted, thus increasing the likelihood of avascular necrosis. In contrast, surgical neck fractures do not carry this risk as the blood supply usually remains intact.

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11

2

Humerus, proximal

Surgical anatomy

(cont)

The deltoid insertion into the lateral aspect of the proximal shaft of the humerus forms an obstacle to the passage of a long plate applied laterally. To pass the deltoid insertion, twisting of the plate 90º into a helical shape allows it to pass from the lateral aspect of the proximal humerus (subdeltoid space) onto the anterior aspect of the distal half of the humerus (subbrachialis space) (Fig 11-5).

Displaced fractures of the proximal humerus are difficult to reduce, because of the deforming forces exerted by the muscle attachments to the humeral tuberosities and shaft (Fig 11-6).

a Fig 11-4 The anterior circumflex artery with its branches. The greater and lesser tuberosities, with their respective rotator cuff insertions counteract each other in rotary function.

b

Fig 11-5a–b

A helical plate avoids both the deltoid insertion and radial nerve in the distal arm by its anterior twist.

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2

Surgical anatomy

(cont)

Supraspinatus

Subscapularis

Pectoralis major

a

b

Fig 11-6a–b Fractures of proximal humerus with displacement are difficult to reduce because of the deforming forces exerted by muscle attachments.

3

Preoperative assessment

Preoperative assessment includes a carefully performed clinical and radiological examination. Clinically, it is important to assess the neurovascular status of the upper limb with special attention paid to the integrity of the brachial plexus and axillary nerve. Also to be noted is the degree of swelling in the shoulder, whether the shoulder is dislocated and any other associated injury that may be present.

Radiological assessment should include the “trauma-series” x-rays of AP, axillary and lateral transscapular views. A CT scan in combination with 3-D reconstruction is very useful in providing additional information on the extent of articular injury and fragment displacement.

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11

4

Humerus, proximal

Preoperative planning

Once a decision has been made that the case is suitable for MIPO, a good preoperative plan helps facilitate the subsequent execution of the surgical procedure. The plan should include a

graphic representation of the fracture fragments, the reduction technique, the surgical approach, the most appropriate implant, and the steps required in its application (Fig 11-7).

a

d

b

c

e

Fig 11-7a–e a b c d e

Preoperative planning for a proximal humeral fracture with extension to the shaft. The metaphyseal plate is contoured according to the shape of the humeral head. A locking proximal humerus plate (LPHP) can be used as a template. The plate is placed lateral to the biceps tendon. The upper level of the plate has to lie about 1 cm below the greater tuberosity. Trapping of the axillary nerve has to be avoided. A cortex screw may be applied fi rst to fi x the proximal segment of the plate to the humeral head fragment before the addition of two LHS. The radial nerve must not lie under the plate. Manual traction aligns the fracture fragments. This should be done with the arm by the side of the chest in neutral rotation. Screw fi xation of the distal fragment; either cortex screws or LHS may be used, depending on their intended function and the bone quality.

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5

OR set-up

5.1

Anesthesia

A trial manipulation may be carried out to test the feasibility of closed reduction.

General or regional anesthesia may be used, depending on the patient’s condition. Even with general anesthesia, a supplementary brachial block may be administered for postoperative pain control. 5.2

The arm is draped to allow free mobility of the shoulder and elbow. Flexion of the elbow to 90˚ with the arm in neutral or slight internal rotation may help to restore axial realignment of the fracture.

Patient positioning and image intensifier 5.3

A beach-chair position with the patient’s head supported on a head rest is preferred. A supine position on a radiolucent operating table with a pad under the scapula is also possible, though not optimal (Fig 11-8). The image intensifier is brought in from the cranial direction and the C-arm positioned to take AP and axillary views of the shoulder. Pilot screening before sterile draping should be carried out to check that satisfactory images can be obtained.

An LCP is the preferred implant for fi xation of proximal humeral fractures, especially in the presence of osteoporosis, which is not uncommon in patients with these injuries. Although not foolproof, locking plates have at least reduced the rate of implant loosening and failure that are not infrequently encountered when conventional plates are used. The locking proximal humerus plate (LPHP) and the PHILOS are specifically designed for the proximal humerus.

c

b

a

Implants and instruments

Fig 11-8a–c a b

Beach-chair position and position of image intensifier. The arm is draped to allow free movements of the shoulder and elbow.

c

AP and lateral views of the proximal humerus taken with the image intensifier.

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11

5

Humerus, proximal

OR set-up

(cont)

These facilitate minimally invasive indirect reduction and fi xation of these fractures. Some contouring may be necessary however, especially when a long plate is used for fractures with distal extensions down the humeral shaft.

6

Operative procedure

The main steps in the application of the LPHP using the MIPO technique are outlined below. 6.1

Another implant that is sometimes used is the LCP L-plate. With this plate, it is easier to avoid the deltoid insertion, but the plate must be of adequate length.

Surgical approach

A transdeltoid lateral approach is used for the proximal introduction of the plate, care being taken not to split the deltoid fibers beyond 5 cm distal to the lateral edge of the acromion in order to avoid injuring the axillary nerve (Fig 11-9).

6.2

Fracture reduction

Reduction of the humeral head fractures is then performed. This is necessary as the locking head screws (LHS) used in the proximal segment of the LPHP cannot exert compression and so are not suitable for indirect reduction. Reduction is performed under fluoroscopic guidance by manipulation and with the help of elevators, bone hooks, and 3 mm Steinmann pins as joysticks. Valgus impacted fractures should be disimpacted and the head fragment reduced to its anatomical position. Once satisfactory reduction has been obtained, the reduction is temporarily held with K-wires. The K-wires should not be placed in positions that may jeopardize the axillary nerve or interfere with the subsequent placement of the LPHP (Fig | Anim 11-10).

Fig 11-9

Anterolateral incisions for MIPO technique.

If the greater or lesser tuberosities are avulsed, these should be reduced and fi xed. The recommended way to fi x these fractures is by the use of nonabsorbable sutures, as the holding power of sutures is stronger than that of screws, especially in osteoporotic bone. Furthermore, sutures will not interfere with the subsequent placement of LHS in the proximal segment of the LPHP. The sutures are placed close to the bony insertions of the subscapularis, supraspinatus, infraspinatus, or teres minor tendons—depending on which tuberosity is avulsed—and then passed through the appropriate suture 127

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6

Operative procedure

(cont)

plate is used, it should fi rst be precontoured into a helical shape to allow it to fit onto the lateral surface of the humerus proximally and its anterior surface distally.

Animation

The proximal segment of the plate should be centered over the greater tuberosity at least 5 mm distal to its proximal edge and 10 mm lateral to the posterior lip of the intertubercular groove.

Fig | Anim 11-10

Fracture reduction with joystick and temporary fi xation with K-wires.

holes in the proximal segment of the LPHP. The sutures are tightly knotted only after defi nitive fi xation of the LPHP. Even if the tuberosities are not fractured, it is prudent to apply these anchoring sutures as the stability and holding power of the LPHP are improved by the application of these sutures since they tend to counteract the muscle tension. 6.3

Plate insertion and fixation

The next step is to create a tunnel for the plate using a tunneling instrument. In cases where the fracture extends distally down the shaft, a long implant has to be used, and the submuscular tunnel must be created from the lateral subdeltoid space to the anterior subbrachialis space. Some resistance may be encountered at the transition between these two spaces due to the mixture of strong fibres from the anterior deltoid and lateral brachialis; so some force may be required. The tunneling instrument is then replaced by the LPHP with the guiding block mounted on its proximal segment. If a long

The proximal segment of the LPHP is then temporarily fi xed to the humeral head fragment with one or two K-wires introduced through threaded LCP drill guides mounted through the guiding block. The position of these K-wires is checked with the image intensifier. If necessary at this point, the shaft fragment is reduced onto the head fragment and plate under fluoroscopic guidance. A short incision is then made over the distal end of the plate using Henry’s approach by splitting the brachialis at its center. Having ensured that the plate is centered over the anterior cortex of the distal humeral shaft, it is temporarily fi xed to the bone with a K-wire introduced through a threaded drill guide. The position of the LPHP and the quality of fracture reduction achieved is checked with the image intensifier. If satisfactory, the proximal K-wires are replaced by LHS after predrilling, removal of the threaded LCP drill guide, and length measurement. At least four screws should be inserted proximally into the head fragment. Distal fi xation is then carried out. Standard cortex screws can be applied through the dynamic compression part of the combination hole in the distal segment of the LPHP for indirect reduction or to generate interfragmentary compression. If used, cortex screws should be applied before the LHS. At least three screws should be used bicortically to fi x the distal segment of the plate to the humerus.

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11

7

Humerus, proximal

Postoperative care

Postoperatively, an arm sling is applied. If the quality and stability of the fi xation achieved is satisfactory, early passive motion is started from the fi rst postoperative day. This 8

Pitfalls –

progresses to protected active and active assisted exercises as fracture union occurs.

9

Pearls +

Pitfall 1

Pearl 1

The axillary nerve is vulnerable at several stages of the operation: During the transdeltoid lateral approach, the deltoid split should not extend more than 5 cm distal to the lateral edge of the acromion. During plate insertion, the plate should be kept close to the humerus to avoid trapping the axillary nerve between the plate and the bone. During insertion of K-wires to temporarily fi x the reduced humeral head fragment, the K-wires should, if possible, avoid the zone 6 cm distal to the acromion and should be placed at a slightly anterolateral angle with the arm in internal rotation.

The LPHP should be correctly positioned. Placing the plate too high may cause subacromial impingement. Placing it too low may limit the number of LHS that can be inserted into the humeral head fragment. Placing it too anteriorly may damage the lateral ascending branch of the anterior circumflex humeral artery, which is the main blood supply to the proximal part of the humeral head.

Pitfall 2

Pearl 2

The radial nerve is vulnerable in several parts along its course if a long plate is used: As it runs along the spiral groove posterior to the midshaft of the humerus, it may be injured by the drill bit or tips of screws placed in an anteroposterior direction. It is therefore best not to insert screws through the plate in an anteroposterior direction in the middle third of the humerus. As it pierces the lateral intermuscular septum, a long plate applied on to the lateral aspect of the humerus may trap the radial nerve here. Along the lateral aspect of the distal humerus, the tip of a Hohmann retractor applied here to expose the distal end of the plate may compress the radial nerve against the lateral humeral cortex.

Twisting the plate into a helical shape during contouring may damage the threads of the locking screw holes. This can be prevented by inserting spacers or threaded drill sleeves into the threaded portions of the combination holes at the zone of plate deformation.

Pearl 3

In osteoporotic bone, the LHS placed into the humeral head fragment should not be too long so that the tips are not too close to the articular surface as there is a risk of screw tip penetration due to settling at the fracture site.

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10

Suggested reading

Fernandez Dell’Oca AA (2002) The principle of helical implants. Unusual ideas worth considering. Case studies. Injury; 33 Suppl 1:SA29–40. Resch H, Hubner C, Schwaiger R (2001) Minimally invasive reduction and osteosynthesis of articular fractures of the humeral head. Injury; 32 Suppl 1:25–32. Rüedi TP, Murphy WM (2001) AO Principles of Fracture Management. Stuttgart New York: Georg Thieme Verlag.

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Authors

11.1 1

Merng Koon WONG, Suthorn BAVONRATANAVECH

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3 Case description

A 58-year-old male motorcyclist with past history of gouty arthrititis was involved in a road traffic accident. He sustained multiple injuries requiring intensive care for 2 days, followed by respiratory treatment for 1 week due to severe bilateral hemopneumothorax. The initial orthopedic management was conservative, by immobilization, because of chest injury. Operative treatment is indicated due to fracture displacement and to allow early mobilization of the shoulder.

Fig 11.1-1a–d a–b c a

c

b

d

Multifragmentary fracture in the metaphyseal region of the proximal right humerus. Bilateral hemopneumothorax, bilateral chest-tube drainage, resorbing subcutaneous emphysema. Markedly displaced distal left clavicular fracture.

d

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11

2

Humerus, proximal

Indication for MIPO

3

In 11-A3 fracture with metaphyseal comminution, MIPO is ideal to preserve blood supply in fracture zone. In addition, it was possible

Patient positioning

The patient is placed in the beach-chair position to optimize reduction and fi xation.

to reduce the head fragment to the humeral shaft by gentle manipulation.

4

Surgical approach

a

b

Fig 11.1-2a–d a

c

d

Longitudinal incision from anterolateral tip of acromion. b Incision is limited to 5 cm to avoid injuring the axillary nerve. c Deltoid muscle is split using blunt dissection. d Subacromial dissection to free the rotator cuff for mobilization. In 11-A2, 11-B2, and 11-C2 fractures, supraspinatus and subscapularis tendons are dissected and marked by strong sutures for fi nal anchorage to an LPHP. Rotator cuff anchorage is to correct anteversion or retroversion and to reduce displaced tuberosities.

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11.1

5

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3

Reduction Fig 11.1-3a–f a

Direct reduction using joysticks and traction preserves blood supply at fracture site. Once reduction is achieved, K-wires are driven axially to medial distal shaft area. b LPHP is contoured into a helical shape to avoid deltoid insertion. c Plate is slipped into a submuscular, extraperiosteal tunnel, along the shaft using helical contouring to avoid deltoid insertion. d LPHP can be fi xed preliminarily by a K-wire through a threaded drill guide to allow adjustment. e Dissection through a small incision to localize plate end distally. f Note visualization of plate centered on anterior aspect of humeral shaft.

a

c

d

e

f

b

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11

6

Humerus, proximal

Fixation

a

b

Fig 11.1-4a–f a–b c–d

c

e

e–f

d

LPHP fi xation proximally and distally. Image intensifier is used to check screw length especially in humeral head, the reduction of fracture, and location of distal plate end. Locking head screws (LHS) must not be placed eccentrically. Plate insertion using small proximal and distal incisions.

f

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11.1

6

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3

Fixation

(cont)

Fig 11.1-5

a

b

Deltoid split is repaired with absorbable suture material.

Fig 11.1-6a–b

Postoperative x-rays. Note: the distal screw could not be inserted as it would not have engaged the bone.

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11

7

Humerus, proximal

Rehabilitation

Following the fi rst month of physiotherapy, patient had to be transferred to internal medicine due to gouty arthritis. Range of motion 3 months postoperatively: abduction and flexion 90°, extension 20°, external rotation 30° and full internal rotation. Patient underwent shoulder manipulation under anesthesia, leading to 140° abduction and flexion, 40º extension and 60° external rotation.

a

a Fig 11.1-7a–b

b

Postoperative x-rays after 12 weeks, fracture healed in proper alignment.

b

c Fig 11.1-8a–c Range of motion 6 months postoperatively, compared to the uninjured shoulder, show good results.

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Author

11.2 1

Frankie KL LEUNG

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3 with diaphyseal involvement

Case description

A 44-year-old male injured his left upper arm in a motor vehicle accident and sustained a closed fracture of proximal humerus with extension to the diaphysis.

F ig 11. 2-1a – c

a

2

b

Preoperative x-rays show a multifragmentary fracture of proximal humerus involving greater tuberosity and surgical neck, and extending to humeral shaft with a medial wedge fragment. A cast was applied initially.

c

Indication for MIPO

Operative treatment was indicated in this case as the fracture was

in screw placement but use of locking head screws (LHS) will greatly

unstable making conservative treatment difficult and prolonged

improve stability.

with a strong likelihood of residual shoulder stiffness. Use of an intramedullary nail was contraindicated since comminution in proximal metaphysis prevents successful proximal locking. Conventional compression plating was not suitable either as it involves extensive surgical dissection. Insertion of a locking com-

3

Patient positioning

pression plate (LCP) as a bridging internal fi xator is the treatment of choice. The small proximal humeral fragment poses great diffi culty

The patient is placed in a beach-chair position.

137

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11

4

Humerus, proximal

Surgical approach

a

c

d

Fig 11.2-2a–d a b

Small anterolateral incision is made 1 cm below acromion. Deltoid muscle is split, exposing greater tuberosity. b–d The thinned proximal part of the metaphyseal plate facilitates contouring. To avoid the radial nerve which lies along the lateral aspect of the distal third of the humerus, it may be necessary to twist the plate into a helical shape so that its distal part lies over the anterolateral aspect of the humeral shaft.

Fig 11.2-3

Plate is inserted through the proximal incision. To avoid the deltoid insertion, a more anterior tunnel is made. Care must be taken to keep the plate close to the bone; otherwise the axillary nerve proximally or the radial nerve distally may be trapped between the plate and the bone. (Alternatively, after making the proximal incision and before plate insertion, the distal incision can be made along the anterolateral aspect of the arm; the biceps retracted medially and the brachialis splits along its midline to expose the anterior surface of the distal humeral shaft; submuscular tunneling from both incisions can then be done using the plate itself or with the aid of a tunneler.)

138

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11.2

4

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3 with diaphyseal involvement

Surgical approach

(cont)

Fig 11.2-4

A 5 cm distal incision is made after confi rmation of correct plate placement by use of an image intensifier.

5

Reduction

Fig 11.2-5 LCP drill sleeves are fi xed to plate and fi ne adjustment is performed to optimize plate position.

a

b

Fig 11.2-6a–b

Fracture is reduced by traction and manipulation to ensure correct length and alignment. K-wires are inserted for temporary fracture fi xation using drill sleeves. 139

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11

6

Humerus, proximal

Fixation

a

b

Fig 11.2-7a–b

Proximal fi xation is performed using four 3.5 mm LHS, distal fi xation using three 5 mm LHS.

7

Fig 11.2-8

Postoperative x-ray. A precise reduction of diaphyseal fragments has not been achieved.

Rehabilitation

Assisted active shoulder physiotherapy starts on fi rst postoperative day. Load bearing allowed after 4 weeks.

Fig 11.2-9

Surgical wound healing.

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11.2

7

Humerus, proximal: extraarticular unifocal fracture, nonimpacted metaphyseal—11-A3 with diaphyseal involvement

Rehabilitation

a

(cont)

b

Fig 11.2-10a–b

Follow-up after 3 months, satisfactory callus formation, no loosening of fi xation.

a Fig 11.2-11

3 months after surgery: minimal pain with satisfactory range of motion.

b

Fig 11.2-12a–b

Excellent range of motion 18 months after surgery—implants had been removed.

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11

7

Humerus, proximal

Pitfalls –

8

Pearls +

Pitfall 1

Pearl 1

Axillary nerve may be injured in the proximal deltoid splitting incision.

An anterolateral incision is used to avoid damage to axillary nerve.

Pitfall 2

Pearl 2

Radial nerve can be damaged during distal dissection.

Using the distal part of Henry’s approach, that is retracting the biceps medially and splitting the brachialis along its midline to expose the anterior cortex of the humeral shaft, can avoid injury to the radial nerve. Army Navy retractors should be used for retracting the two halves of the brachialis instead of Hohmann retractors.

Pitfall 3

Pearl 3

Deltoid insertion in proximal humerus hinders plate positioning.

To avoid damaging the deltoid insertion, a more anterior tunnel is preferred. Torsional contouring of implant into a helical shape is useful for plate positioning on lateral aspect of proximal humerus and on anterior aspect of distal humerus.

142

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143

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12

Humerus, shaft

1

Introduction

145

Cases

1.1

Classification

146

12.1

1.2

Indications and contraindications for MIPO

146

2

Surgical anatomy

146

2.1

Bone

146

2.2

Muscles

146

2.3

Nerves

147

2.4

The safe zone of the humerus

147

3

Preoperative assessment

149

4

Preoperative planning

149

5

OR set-up

150

5.1

Anesthesia

150

5.2

Patient positioning and image intensifier

150

5.3

Implants and instruments

150

6

Operative procedure

151

6.1

Surgical approach

151

6.2

Preparation and passage of the tunneling

Humerus, shaft: wedge fracture, bending wedge—12-B2

12.2

157

Humerus, shaft: complex fracture, irregular—12-C3

163

12.3

Humerus, shaft: complex fracture, spiral—12-C1 169

12.4

Humerus, shaft: wedge fracture, fragmented wedge—12-B3

173

Teaching video on DVD-ROM

instrument

152

6.3

Passage of the implant

152

6.4

Reduction and fixation

153

7

Postoperative care

154

8

Pitfalls

154

9

Pearls

154

10

Suggested reading

156

12

Humerus, shaft—anterior approach

144

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Author

12

1

Theerachai APIVATTHAKAKUL

Humerus, shaft

Introduction

Fractures of the shaft of the humerus account for 1% of all fractures. Most of these fractures can be treated conservatively by functional bracing with satisfactory outcomes. The humerus is not a weight-bearing bone and shortening is better tolerated while malalignment can be compensated by the shoulder and elbow joints. If the alignment is not acceptable, operative treatment with internal fi xation should be considered. There are several methods of fi xation available, namely, plate fi xation, intramedullary nailing, and external fi xation. The choice of method is based on the condition of the soft tissues, fracture location and configuration, bone quality, canal diameter, facilities and resources available, and the skills and experience of the surgical team. While external fi xation is reserved mainly for open fractures or closed injuries with severe softtissue compromise, plating and intramedullary nailing can both be used for most humeral shaft fractures. Locked intramedullary nailing can be done through relatively small incisions and so incurs less soft-tissue trauma. Plate fi xation, on the other hand, is technically demanding, requiring extensive exposure and soft-tissue dissection, but it can provide stable fi xation. In order to make use of the advantages of plate fi xation while avoiding the disadvantages of open plating such as excessive soft-tissue stripping and devascularization, the plate may be introduced using MIPO techniques. The problem with MIPO for humeral shaft fractures is the presence of the major nerves and the brachial vessels which, if injured, can lead to serious consequences. Anatomical studies have shown that there is a “safe zone” in the humerus that is not crossed by any major nerve or vessel and thus is suitable for MIPO techniques. This safe zone is the anterior surface of the humeral shaft deep to the brachialis muscle.

a

b

c

Fig 12-1a–c

12-A simple fracture. 12-A1 spiral b 12-A2 oblique (≥ 30º) c 12-A3 transverse (< 30º) a

a

b

c

Fig 12-2a–c

12-B wedge fracture. 12-B1 spiral wedge b 12-B2 bending wedge c 12-B3 fragmented wedge a

a

b

c

Fig 12-3a–c

12-C complex fracture. a 12-C1 spiral b 12-C2 segmental c 12-C3 irregular

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1

Introduction

1.1

Classification

(cont)

In the Müller AO Classification, the shaft of the humerus is identified by the number 12. The A, B, C classification distinguishes between simple (A), wedge (B), and complex (C) fractures (Fig 12-1, Fig 12-2, Fig 12-3). 1.2

Indications and contraindications for MIPO

MIPO can be performed for most closed humeral shaft fractures. The plate is usually applied according to the principle of bridge plating and the radial nerve is not usually identified.

An absolute contraindication for MIPO in humeral shaft fractures is the presence of radial nerve palsy, since the radial nerve is not exposed or identified during the MIPO procedure. MIPO should also not be used in the following situations: Severe tissue loss without coverage of exposed bone Osteomyelitis Delayed surgery with shortening Delayed reconstructions (eg, requiring bone grafting)

Good indications for MIPO are: Comminuted fractures Fractures extending to the proximal or distal shaft Segmental fractures Small medullary canals (< 8 mm) Deformed shaft (malunions) Open growth plates

2 2.1

Surgical anatomy Bone

The humeral shaft extends from the inferior border of the pectoralis major insertion proximally to the supracondylar ridge distally. This region encompasses the middle 3/5 of the entire humerus. Cross-sectional shape varies from round proximally to triangular distally (Fig 12-4). The anterior aspect of the humerus possesses an anterior ridge with anterolateral and anteromedial surfaces. The posterior aspect of the humerus presents a broad, flat surface extending from the posterior aspect of the neck of the humerus to the olecranon fossa distally. The deltoid tubercle forms a lateral prominence just

proximal to the midshaft. Knowledge of the bony anatomy of the humerus is essential when contouring the plate to fit the bony surface. 2.2

Muscles

The arm has two major muscle compartments, flexor and extensor, which are separated by the medial and lateral intermuscular septi. The flexor or anterior compartment contains three muscles: the coracobrachialis, the biceps brachii, and the brachialis. All are supplied by the musculocutaneous nerve except the lateral part of the brachialis which is supplied by

146

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12

2

Humerus, shaft

Surgical anatomy

(cont)

the radial nerve. The extensor, or posterior, compartment has only one muscle, the triceps brachii, which is supplied by the radial nerve. 2.3

Nerves

The radial nerve is a continuation of the posterior cord of the brachial plexus. It runs along the posterior wall of the axilla, and then passes through the triangular space formed by the long head of the triceps, shaft of the humerus, and the teres major muscle. The nerve crosses from medial to lateral by lying in the spiral groove close to the bone on the posterior aspect of the midshaft of the humerus. After crossing the posterior surface of the humerus, the radial nerve pierces the lateral intermuscular septum to enter the anterior compartment where it lies between the brachialis and brachioradialis. In this area the radial nerve is separated from the bone by the brachialis muscle. The median nerve lies in the anterior compartment and runs alongside the brachial artery on the anteromedial aspect of the arm. In the upper arm, the ulnar nerve lies posterior to the brachial artery in the anterior compartment. After running down 2/3 of the arm, it pierces the medial intermuscular septum to enter the posterior compartment and then continues distally to the posterior aspect of the medial epicondyle. The musculocutaneous nerve is a branch of the lateral cord. The nerve enters the coracobrachialis about 5–8 cm distal to the coracoid process on its medial side. After piercing the coracobrachialis, it runs on the anterior surface of the brachialis and branches to supply the biceps and medial part of the brachialis muscle. The nerve continues distally to supply sensation to the lateral forearm (lateral cutaneous nerve of the forearm).

2.4

The safe zone of the humerus

To identify the safe zone of the humerus, it is necessary to understand the cross-sectional anatomy of the proximal, middle, and distal humerus (Fig 12-4). In the proximal humerus, the axillary vessels and three nerves (radial nerve, median nerve, and ulnar nerve) run along its medial side. The branches of the axillary nerve and posterior humeral circumflex vessels are posterior and continue laterally. The only safe zone that has no neurovascular structures in the proximal humeral shaft is its anterior aspect (Fig 12-4a). The profunda brachii vessels and the radial nerve run close to the posterior aspect of the midshaft of the humerus in the spiral groove. The brachial artery and vein along with the median and ulnar nerves are on the medial side of the humerus. The musculocutaneous nerve lies on the anterior surface of the brachialis muscle. The safe zone of the midshaft of the humerus is its anterior surface deep to the brachialis muscle (Fig 12-4b). In the distal arm, the radial nerve moves laterally and, after piercing the lateral intermuscular septum, lies between the brachialis and the brachioradialis muscles lateral to the humerus. The brachial vessels, median nerve and ulnar nerve are on its medial side. The musculocutaneous nerve lies anterior to the brachialis muscle. The safe zones of the distal shaft of the humerus include its posterior surface as well as its anterior surface deep to the brachialis muscle (Fig 12-4c). From these three cross-sectional studies, it is evident that the safe zone for the percutaneous insertion of a straight plate for the humeral shaft is on its anterior surface deep to the brachialis muscle (Fig 12-5).

147

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2

Surgical anatomy

(cont)

1

Musculocutaneous nerve

2

Radial nerve

1 2

a

1 2

b

1 2 c

Fig 12-4a–c

Cross-sectional anatomy of humeral shaft.

Fig 12-5 Approaches to the anterior aspects of the proximal and distal humeral shaft.

148

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12

3

Humerus, shaft

Preoperative assessment

A complete neurovascular assessment is necessary. The vascular status of the extremity should be evaluated by palpation of the distal pulses and assessment of the capillary refi ll. All peripheral nerves should be assessed, especially the radial nerve which has a high risk of injury due to its close proximity to the humerus.

4

Radiographic evaluation must include anteroposterior and lateral projections of the entire humerus, as well as views of the shoulder and elbow joints. This approach confi rms the diagnosis of the fracture and prevents missing associated injuries in the adjacent joints.

Preoperative planning

MIPO of the humerus is technically more demanding than conventional plating. Indirect reduction, tunneling, and percutaneous fi xation techniques require accurate preoperative planning to choose the appropriate type of implant, its length,

a Fig 12-6a–e

b

c

the number and position of the screws, and their order of insertion. Preoperative planning by x-ray overlaying and stepby-step planning of the surgical procedure is necessary (Fig 12-6).

d

e

Example of a preoperative plan, with step-by-step execution of the procedure. 149

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5

OR set-up

5.1

Anesthesia

Surgery is usually performed under general anesthesia. 5.2

Patient positioning and image intensifier

The patient lies in a supine position with the arm abducted 90° and the forearm in full supination. The arm is rested on a radiolucent side-table (Fig 12-7). An image intensifier is essential and is positioned on the same side of the operating table as the arm to be operated on. 5.3

Implants and instruments

Implants for MIPO of the humerus

The narrow dynamic compression plate (DCP) 4.5 can be used for MIPO of humeral shaft fractures. The plate is minimally precontoured at the proximal part in order to fit the anterior ridge. The plate should be long enough to bridge the fracture segment while permitting at least three to four screws each in the main proximal and distal fracture fragments. The locking compression plate (LCP) with locking head screws (LHS) functions as an internal fi xator. There is little or no contact with the bone surface and so minimal additional damage to the blood supply is caused. Exact precontouring to fit the bone surface is not required. At least three screws in each fragment are required to achieve stable fi xation.

Plate length

The length of the plate remains a controversial issue. With the MIPO technique, plate length can be increased with minimal additional soft-tissue dissection. The plate can be divided into three segments: a proximal segment, a middle segment over the fracture site between the two innermost screws, and a distal segment. The proximal and distal segments of the plate should allow at least three to four screws to be applied on each main fracture fragment; the most proximal screw should be about 3 cm distal to the bicipital groove and the most distal screw about 1–2 cm proximal to the olecranon fossa. Number of screws and order of screw placement

From the biomechanical point of view, for fractures of the humerus, three or four screws on either side of the fracture should be used, as rotational forces predominate in the humerus. In simple fractures with a small fracture gap, at least one or two plate holes on each side of the fracture should be left without screws in order to allow some degree of micromotion that will act as a stimulus for callus formation. In multifragmentary fractures, the two innermost screws should be applied as close as possible to the fracture site while the remaining screws should be spread over each of the proximal and distal main fracture fragments.

Fig 12-7

The patient in supine position with the arm abducted 90° and the forearm in full supination.

150

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12

6 6.1

Humerus, shaft

Operative procedure Surgical approach

brachialis is identified. The biceps is retracted medially to expose the musculocutaneous nerve lying on the anterior surface of the brachialis (Fig 12-8c). The brachialis is then split longitudinally along its midline to reach the periosteum of the anterior cortex of the distal humerus (Fig 12-8d). The musculocutaneous nerve is retracted together with the medial half of the split brachialis, while the lateral half serves as a cushion to protect the radial nerve, which at this point, has pierced the lateral intermuscular septum and is lying between the brachioradialis and brachialis muscles.

The interval between the lateral border of the proximal part of the biceps and the medial border of the deltoid is palpated. A 3 cm proximal incision is made approximately 6 cm distal to the anterior part of the acromion process and the dissection is carried down to the humerus (Fig 12-8a). Distally, a 3 cm incision is made along the lateral border of the biceps approximately 5 cm proximal to the flexion crease of the elbow (Fig 12-8b). The interval between the biceps brachii and the

a

b

Fig 12-8a–d

c

d

Step-by-step approaches to the proximal and distal humeral shaft.

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6 6.2

Operative procedure

(cont)

Preparation and passage of the tunneling instrument

A subbrachialis, extraperiosteal tunnel is created by passing a tunneling instrument deep to the brachialis from the distal to the proximal incision (Fig 12-9a). Some difficulty may be encountered during passage of the tunneling instrument at the proximal part of the tunnel due to the intimate blending of the fibres of the brachialis and deltoid muscles along the lateral aspect of the tunnel at this point. Incision of these muscle fibres at the tip of the tunneling instrument will allow

a Fig 12-9a–c

b

its passage through to the proximal incision. To avoid injury to the radial nerve at the lateral aspect of the distal humerus, the tunneling instrument should be passed along the anterior, or slightly anteromedial aspect of the humerus. 6.3

Passage of the implant

After preparation of the anterior subbrachialis tunnel, the selected narrow DCP or LCP is tied with a suture to a hole at the tip of the tunneling instrument. The tunneling instrument is then withdrawn, pulling with it the plate along the track

c

Plate insertion in MIPO technique.

152

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12

6

Humerus, shaft

Operative procedure

(cont)

that it has created (Fig 12-9b–c). This method ensures that the plate is guided into the correct tunnel and avoids injury to the radial nerve. 6.4

Reduction and fixation

The plate is then fi xed to the proximal humerus with one screw (Fig 12-10a). Reduction of the fracture is usually achieved by manipulation. Traction is used to restore the length and rotation. After positioning the plate over the center of the

a

anterior surface of the distal humerus, one screw is inserted distally (Fig 12-10b). Varus and valgus angulation is checked with the image intensifier. When the alignment is correct, one more screw is inserted into each fragment. The alignment is reassessed with the image intensifier and, if satisfactory, the fi xation is completed with at least three screws in each fragment (Fig 12-11). When using a DCP or an LC-DCP, it is preferable to fi x the screws in a divergent direction to catch more area of the cortex. The divergent screw direction also requires smaller and fewer incisions.

b Fig 12-11

Fig 12-10a–b

Temporary plate fi xation, proximally and distally.

After correct alignment, fi xation is completed with at least three screws in each fragment.

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7

Postoperative care

After removal of the suction drain, the patient is encouraged to perform passive exercises of the shoulder and the elbow as tolerated during the fi rst postoperative week. Active mobilization is carried out from the second week. AP and lateral x-rays of the humerus are taken at 6 weeks, 3 months, and 6 months to assess healing and to look for secondary loss of alignment.

8

Pitfalls –

9

Pearls +

Pitfall 1

Pearl 1

The radial nerve is vulnerable during fracture reduction, tunneling, and plate insertion. Radial nerve function has to be evaluated before and after surgery. MIPO technique is not recommended in fractures with radial nerve palsy. Postoperative radial nerve palsy is an indication for radial nerve exploration.

To protect the radial nerve, the forearm must be kept in full supination during the surgery. This is because when the forearm is supinated, the radial nerve moves more laterally away from the distal humerus and so is less likely to be injured.

Pitfall 2

Pearl 2

In the distal incision, Hohmann retractors should not be used to retract the two halves of the brachialis after it is split along its midline as the radial nerve can be caught and compressed by the tip of the retractor during the retraction.

When exposing the distal shaft of the humerus in preparation for tunneling and plate insertion, the brachialis is split along its midline. The two halves of the brachialis are then separated using Army Navy retractors. The lateral half of the muscle protects the radial nerve while the medial half protects the musculocutaneous nerve (see Fig 12-9).

154

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12

8

Humerus, shaft

Pitfalls –

(cont)

9

Pearls +

(cont)

Pitfall 3

Pearl 3

The musculocutaneous nerve can be injured during the brachialis muscle splitting, tunneling, or plate insertion. This can be prevented by identifying the nerve before splitting the brachialis muscle. However, the sensory impairment resulting from injury of the musculocutaneous nerve is minimal and, in most cases, reversible.

To avoid injury to the radial nerve in the spiral groove, it is best not to insert screws in an anteroposterior direction in the midshaft of the humerus. If the midshaft area needs fi xation, screws should be applied monocortically whenever possible.

Pearl 4

It is easier to control the direction of the tunneler if one begins tunneling from the distal shaft under the brachialis muscle. To avoid going in the wrong direction, the tip of the tunneler must be in contact with the bone all the way to the proximal incision.

Pearl 5

Comminuted fractures are easier to reduce than transverse fractures. Segmental fractures are the most difficult as the surgeon needs to reduce two fractures. In order to reduce the middle segment, it may be necessary to overdistract the humerus to create the space to allow the middle segment to move back into position.

Pearl 6

Proximal and distal screw insertion should be in the center of the bone to prevent malalignment.

155

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10

Suggested reading

Apivatthakakul T, Arpornchayanon O, Bavonratanavech S (2005) Minimally invasive plate osteosynthesis (MIPO) of the humeral shaft fracture. Is it possible? A cadaveric study and preliminary report. Injury; 36(4):530–538. Fernandez Dell’Oca AA (2002). The principle of helical implants: unusual ideas worth considering. Injury; 33 Suppl 1:SA1–27. Gautier E, Sommer C (2003) Guidelines for the clinical application of the LCP. Injury; 34 Suppl 2:SB63–76. Hoppenfeld S, DeBoer P (1984). Surgical Exposures in Orthopaedics: the Anatomic Approach. Philadelphia: JB Lippincott:47–75. Krettek C, Schandelmaier P, Miclau T, et al (1997) Minimally invasive percutaneous plate osteosynthesis (MIPPO) using the DCS in proximal and distal femoral fractures. Injury; 28 Suppl 1:A20–30. Mast J, Jakob R, Ganz R (1989) Planning and Reduction Techniques in Fracture Surgery. Berlin Heidelberg New York: Springer-Verlag.

156

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Author

12.1 1

Theerachai APIVATTHAKAKUL

Humerus, shaft: wedge fracture, bending wedge—12-B2

Case description

a

2

b

Indication for MIPO

Conventional plating is not suitable for comminuted fracture of the humeral shaft because it requires extensive soft-tissue dissection

Fig 12.1-1a–b A 23-year-old male had a motorcycle accident and sustained a fracture of the shaft of his left humerus (12-B2) as well as a fracture of the proximal left femur. 2 years previously, the patient sustained bilateral femoral fractures which had been fi xed with retrograde femoral nails. This time, the fracture of the left femur has occurred at the level of the one of the proximal locking screws. The retrograde femoral nail was also broken at this level.

3

Patient positioning

Patient in supine position, with arm abducted 40°–60° on a radiolucent operating table.

and bone grafting. MIPO preserves the soft tissue and blood supply with rapid callus formation.

157

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12

4

Humerus, shaft

Surgical approach

b

a

Fig 12.1-2a–d a

Proximal incision between lateral border of biceps muscle and medial border of deltoid muscle. Distal incision between lateral border of biceps muscle and brachialis muscle. b Deep dissection at distal incision between biceps muscle and brachialis muscle. The musculocutaneous nerve has to be identified deep to the biceps muscle. c Biceps muscle and musculocutaneous nerve are retracted medially. The brachialis muscle is split longitudinally, along its midline to expose the anterior surface of humerus. Lateral half of brachialis muscle and radial nerve are retracted laterally. d Deep dissection at proximal incision between lateral border of biceps muscle and medial border of deltoid muscle down to the bone.

c

d

158

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12.1

4

Humerus, shaft: wedge fracture, bending wedge—12-B2

Surgical approach

(cont)

a

b

c

d

Fig 12.1-3a–d a

Tunneler is slipped through distal incision and passed proximally beneath brachialis muscle to create subbrachialis tunnel. b Tunneler is advanced until its distal end appears at the proximal incision. c Plate end is attached to tunneler by means of a suture. d Tunneler pulled back along with plate into subbrachialis tunnel.

159

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12

5

Humerus, shaft

Reduction and fixation

a

b

d

c

e

f

Fig 12.1-4a–f a

Plate is aligned in the center of distal humerus.

b–c Plate is fi xed to distal fragment with two screws. d

Indirect reduction by manual traction to restore length and rotation of humerus. Proximal fragment is fi xed with one screw.

e–f Image intensifier is used to check fracture reduction. If

reduction is satisfactory, fi xation is completed with three screws in each main fracture fragment.

160

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12.1

5

Humerus, shaft: wedge fracture, bending wedge—12-B2

Reduction and fixation

(cont)

a

b

Fig 12.1-5a–b a b

a

Two small incisions used in this MIPO technique. The radial nerve function is intact.

b

Fig 12.1-6a–b

Postoperative x-rays show fi xation of main fragments. 161

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12

6

a

Humerus, shaft

Rehabilitation

b

Fig 12.1-7a–b

X-rays at 6 months, the fracture has completely healed.

Fig 12.1-8

Functional result at 6 months.

162

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Author

12.2 1

Theerachai APIVATTHAKAKUL

Humerus, shaft: complex fracture, irregular—12-C3

Case description

a

2

b

Fig 12.2-1a–b A 41-year-old male, victim of motorcycle accident, with multifragmentary fractures of the left humeral shaft with proximal extension.

Indication for MIPO

The disadvantages of conventional plate fi xation for multifragmentary humeral shaft fractures include extensive soft-tissue dissection and the frequent need for bone grafting. MIPO avoids these. Proximal extension of the fractures makes it difficult for intramedullary nailing.

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12

3

Humerus, shaft

Patient positioning and plate contouring

Fig 12.2-2a–b a

a

4

a

b

Beach-chair position with arm lying free by the side. The image intensifier is positioned cranially. b The selected metaphyseal LCP is precontoured, using a plastic bone model or a locking proximal humeral plate (LPHP) as a template, to fit the anterolateral surface of the proximal humerus as well as the shaft.

Surgical approach

b

c

Fig 12.2-3a–d a

Skin markings for proximal and distal incisions. Distal incision between biceps and brachialis muscles. c Biceps muscle retracted medially. Brachialis muscle split longitudinally along its midline—the medial half retracted medially with musculocutaneous nerve and the lateral half retracted laterally with radial nerve. (Note the use of Army Navy retractors for retraction.) d Proximal deltoid splitting approach. b

d

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12.2

4

Humerus, shaft: complex fracture, irregular—12-C3

Surgical approach

(cont)

a

b

c

c

d

Fig 12.2-4a–f

Tunneling and plate insertion. Subdeltoid tunnel created with the plate. b Subbrachialis tunnel created with tunneler introduced through distal incision and passed proximally. c Tunneler passed through to