Imaging skeletal trauma [4 ed.] 9780323278195, 0323278191

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IMAGING SKELETAL TRAUMA

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IMAGING SKELETAL TRAUMA Fourth Edition

Lee F. Rogers, MD Professor Emeritus Feinberg School of Medicine Northwestern University Chicago, Illinois Wake Forest School of Medicine Wake Forest University Winston-Salem, North Carolina

O. Clark West, MD Director Emergency Radiology Section Department of Diagnostic and Interventional Imaging Level 1 Trauma Center Memorial Hermann Hospital Texas Medical Center Professor University of Texas Health Science Center Houston Medical School Houston, Texas

1600 John F. Kennedy Blvd. Ste 1800 Philadelphia, PA 19103-2899 IMAGING SKELETAL TRAUMA, FOURTH EDITION Copyright © 2015 by Saunders, an imprint of Elsevier Inc.

ISBN: 978-1-4377-2779-1

No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Previous editions copyrighted 2002, 1992, 1982 by Churchill Livingstone. Library of Congress Cataloging-in-Publication Data Rogers, Lee F., 1934- , author. Imaging skeletal trauma / Lee F. Rogers, O. Clark West. -- Fourth edition. p. ; cm. Preceded by Radiology of skeletal trauma / [edited by] Lee F. Rogers. 3rd ed. c2002. Includes bibliographical references and index. ISBN 978-1-4377-2779-1 (hardback : alk. paper) I. West, O. Clark, author. II. Radiology of skeletal trauma. Preceded by (work): III. Title. [DNLM: 1. Bone and Bones--injuries. 2. Fractures, Bone--radiography. WE 175] RD101 617.4’71044--dc23 

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Printed in the United States of America Last digit is the print number: 9 8 7 6 5 4 3 2 1

2014037963

To my father, the late Doctor Watson F. Rogers, of Vienna, West Virginia, a true physician; loved by his family, admired by his patients, and respected by his colleagues. Born in St. Albans, Vermont, raised in Vergennes, Vermont, and educated at the University of Vermont, he practiced medicine in Underhill, Vermont, and Vienna and Parkersburg, West Virginia. And the memory of our medical heritage, all physicians, all Vermonters: my grandfather, Doctor Frank Matthew Rogers of St. Albans and Vergennes, Vermont; my great uncle, Doctor Daniel Lee Rogers of Bolton Landing, New York; my great uncle, Doctor Sam Rogers of Proctor, Vermont; my uncle, Doctor Samuel Rogers of Stowe, Vermont; and to all those who may have suffered as we learned. And to my grandchildren, Dean, Garrison, Megan, Westin, John, and Morgan, in the fond hope that whatever they may become and wherever that might be, they too find something as rewarding and meaningful to do with their lives as those of us who have preceded them. And last, to my wife, Donna B., who made this and all other of my works possible. I am most grateful for her forbearance and tolerance of my preoccupations through the four editions of this book. It is hard to imagine having completed these works without her constant love, encouragement, and support. Lee F. Rogers

To my recently deceased uncle, Emory Guth West, MD, FACR, born in Des Moines, Iowa, and educated in Medicine and Radiology at Northwestern University in Chicago. He practiced Radiology in Mountainview, California. In my “tween” years, spending days watching him work in his office and conversing with him about “automotive medicine” – the precursor of modern trauma care – provided the spark for my career. To my father, George Guth West, MBA, JD, born in Des Moines, Iowa, and currently resident of Henderson, Nevada. His support throughout my medical training and his encouragement to pursue a career in an unorthodox field – academic trauma imaging – have been invaluable. To my wife, Victoria Kiechler West, and daughter, Rebecca Kathryn West, for their unwavering love and support in all my professional endeavors. And to all radiologists who think of themselves as Emergency Radiologists or Trauma Radiologists. This book is for you – to provide the knowledge base for excellence in imaging skeletal trauma. O. Clark West

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Preface

I

t has been 12 years since the previous edition of this work. A lot has happened in the interim. Microprocessors have revolutionized imaging; not only the means of medical imaging but how images are viewed and reported; how these reports are recorded, transmitted, and communicated; how images are stored and retrieved; and even how one seeks information regarding the imaging characteristics of disease or searches the literature to learn of or substantiate their findings. Microprocessors have made images, reports, and the clinical, pathologic, and imaging characteristics of disease instantaneously accessible. We have achieved the potential of “real-time radiology.” As a result of microprocessor-driven innovations in information accessibility, the nature of textbooks has changed. Because of the online availability of medical images and accurate and reliable information, the demand for and need of larger general texts has diminished while readers’ requests for shorter, portable single-topic works that might be downloaded on desktop computers, laptops, iPads, and smart phones has risen. Our work has been revised in its fourth edition to accommodate readers’ requests. But we did not start out that way. In planning for the fourth edition of my text I was fortunate to secure the assistance of Professor O. Clark West of the University of Texas Health Science Center at Houston Medical School, an internationally recognized authority in the field of Emergency Radiology, as a partner and fellow author in this endeavor. Dr. West heads the Emergency Radiology Section of the Department of Diagnostic and Interventional Imaging, which services the active Level 1 Trauma Center of Memorial Hermann Hospital in Houston’s sprawling Texas Medical Center and has a particular interest and extensive clinical experience in the application of multidetector CT (MDCT) to trauma imaging. In view of his interest and expertise Dr. West accepted responsibility for authorship of the chapters devoted to the axial skeleton: cervical spine, thoracolumbar spine, and pelvis, and I authored eight chapters devoted to the peripheral skeleton: shoulder, elbow, wrist, hand, hip, knee, ankle, and foot. The previous three editions of Radiology of Skeletal Trauma were two-volume texts of 1400 to 1700 pages. In preparing a manuscript for a fourth edition the publisher asked that we provide a single-volume text of approximately 300 pages. This substantial reduction presented a significant challenge. Dr. West and I hesitantly agreed to undertake the task. We gave it our all, but found the results of the required shortening produced chapters far short of our goal to provide a useful, informative, and instructional resource. The product of our labors was simply unacceptable. However, all was not lost. While working on the revision, I became increasingly aware of the troubling thought that I had written three two-volume editions of a book containing considerable information but had never informed the reader precisely how I used this information in the assessment and interpretation of images of skeletal trauma. To this end we had decided to add what I called a “primer” at the beginning of each chapter containing the basic information needed to make an informed judgment and confident interpretation of images of skeletal trauma. We then stopped working on the revision and turned our attention to writing a primer for each anatomic area. It took three to four years to complete this undertaking. Ultimately, we came to the conclusion that the primers alone had the making of a good short text and abandoned our attempt to make a standard revision of the previous edition. We define a primer as a small exploratory book on a subject – a collection of short informative pieces of writing that cover the basic elements. Our intent is that the information provided in this primer should enable users to confidently and accurately identify as many as 90% to 95% of fractures and dislocations that they encounter. The Primer begins with checklists for each of the following: 1. Radiographic examination listing views required 2. Common injuries in adults 3. Common injuries in children and adolescents. 4. Injuries likely to be missed 5. Avoiding satisfaction of search: Now that you have seen this what else should you be looking for 6. What you do when you see nothing at all: Indications for CT and MRI vii

viii   

  Preface

The checklists are followed by “The Primer,” a brief description with illustrative images for each separate checklist. I personally designed the layout for the Primer in a Word document. Then I typed the manuscript, made the drawings, and downloaded the images into each primer. I used tif images in the primer documents, the same high-quality images that would be sent to the publisher for publication. This was done to show the publisher precisely how I wanted the manuscript laid out. One day I was reading out with a resident, Dr. Ravi Shastri, now a Fellow in Neuroradiology at the University of Michigan. Ravi had seen printouts of a few of the chapters. He asked if he could download one of the primer Word documents on his iPad to show me what it would look like. I was curious. “Why not?” We copied one of the documents on his thumb drive and soon thereafter he showed me the primer document on his iPad. I was amazed. The images were dazzling. The ability to enlarge the images on the iPad was spectacular. Dr. Shastri’s demonstration on the iPad convinced me of the advantages and added value of the digital electronic presentation. I then showed the primers on my iPad to many radiologists—residents, fellows, and experienced practitioners—and all were impressed and found this format potentially useful. Subsequently, I met with Don Scholz and Jacob Hart of Elsevier to show them several primer chapters on an iPad. They were also impressed. Ultimately Elsevier decided that the fourth edition of the text, now named Imaging of Skeletal Trauma would be published and available in both print and electronic forms. We are pleased by Elsevier’s decision to proceed in this fashion and grateful for their support. Each chapter describes what I refer to as a “directed search” in viewing and interpreting radiographs of musculoskeletal trauma. Know specifically what you are looking for and look for it. Know what images to obtain, what injuries are likely and what they look like, what injuries are likely to be missed and why, how to avoid satisfaction of search—where else to look when you find certain injuries, and when to obtain CT and MRI. This work would be of value to physicians in Emergency Medicine and Orthopedics as well as Diagnostic Radiologists. As written it is suitable for self-instruction or self-­evaluation as well as an everyday go-to aid in the throes of reading images of musculoskeletal trauma from emergency rooms and elsewhere during the regular workday or when on call at night or weekends. This work could also form the basis of an introductory instructional course for beginners as well as a refresher course for the more experienced. Dr. West and I could not have completed this work without the assistance of many others. My particular thanks to Michele Dalmenday for her attention to detail and exceptional secretarial support and to Duane Cookman for his assistance in acquiring the numerous images that were required from the files of the Department of Medical Imaging at the University of Arizona Medical Center in Tucson. The vast majority of the images are new; less than 10% were repeated from the third edition. Dr. West’s principle coauthors were Susanna C. Spence for the spine chapters and Suresh K. Cheekatla for the pelvis chapter. His colleagues Naga Ramesh Chinapuvvula and Nicholas M. Beckmann contributed case material and their ideas. The noun “primer” is recognized by many as a small book used to teach children to read such as the McGuffey Readers, so popular in elementary schools in the latter nineteenth and early twentieth centuries. McGuffey’s Readers may have been small but they produced essentially universal literacy among the American populace, no small achievement. Dr. West and I can only hope that we should be so fortunate as to achieve similar results with this primer, the elimination of “illiteracy” among those who interpret images of skeletal trauma and a noticeable improvement and greater confidence in the performance and interpretation of imaging examinations in skeletal trauma. Read, mark, and inwardly digest. Dr. West and I are pleased to be of service. Lee F. Rogers, MD Tucson, Arizona June 8, 2014

Contents CHAPTER 1  Introduction.............................................................................. 001 CHAPTER 2  The Shoulder............................................................................ 005 CHAPTER 3  The Elbow................................................................................ 015 CHAPTER 4  The Wrist.................................................................................. 024 CHAPTER 5  The Hand.................................................................................. 035 CHAPTER 6  The Cervical Spine................................................................... 043 CHAPTER 7  The Thoracolumbar Spine........................................................ 090 CHAPTER 8  The Pelvis................................................................................. 128 With Suresh K. Cheekatla, MD

CHAPTER 9  The Hip..................................................................................... 172 CHAPTER 10  The Knee.................................................................................. 186 CHAPTER 11  The Ankle................................................................................. 199 CHAPTER 12  The Foot................................................................................... 211

ix

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CHAPTER 1

Introduction The primary objective in interpreting radiographs of skeletal trauma is to identify any and all skeletal injuries. However, despite the essentially universal availability and liberal use of radiographs, failure to diagnose fractures is a leading source of oversights in emergency departments and urgent care centers. Failure to recognize fractures on radiographs accounts for a significant percentage of diagnostic errors in these settings. The interpretation of images obtained for the assessment of skeletal trauma is not intuitively obvious. Not surprisingly, experts in image interpretation recognize abnormalities more rapidly and with greater diagnostic accuracy than the novice with less knowledge and experience. An efficient and accurate approach is required and must be learned through study and practice. Learn to do what the experts do. The expert search of images is not random. They know what they are looking for and what it should look like and where to find it. They seek out soft tissue signs that are known to point to underlying bony injury. They know the common sites of injury and look there. Experts are aware of the subtleties, know what they are likely to miss, and are mindful of the need to avoid satisfaction of search. What are the characteristics of an efficient and effective approach to the interpretation of images of skeletal trauma? First, obtain the proper radiographs. Insist upon proper radiographs. Standard views have been established for each anatomic part to ensure accurate assessment of potential injuries. High-quality and properly positioned images in these standard projections must be obtained to lessen the chance of errors and oversights. One view is no view. Fractures and dislocations cannot be excluded on one view alone. A minimum of two views is required to safely exclude fractures of the shaft of long bones. A minimum of three views — AP, lateral, and oblique — is required to safely exclude fractures of the ends of bone and dislocations of joints in the peripheral skeleton. Oblique views are essential. If the examination centered on joints is limited to just the AP and lateral views, 7% to 9% of fractures may be overlooked. Second, be familiar with the sites and appearance of the common fractures and injuries. Look specifically at these sites for evidence of injury. Staring at a radiograph or other form of image in hopes you will note an abnormality is usually unproductive. In trauma the sites of injury are predictable and repetitive. Use what I term a “directed search”; develop a pattern of search to look specifically at the common sites of injury. Third, know where to look for soft tissue signs that point to underlying bony injury. The presence of joint fluid, a visible joint effusion, in the setting of trauma is almost always a sure

sign of intraarticular fracture or ligamentous injury. This is particularly true of the knee and elbow and, to a lesser extent, the ankle and glenohumeral joint. Unfortunately, joint effusions in other joints are difficult to identify on radiographs. Periarticular soft tissue swelling is nonspecific but does direct your attention to the underlying bone, particularly in the ankles, fingers, and toes, but is more difficult to identify in the more proximal joints. Conversely, the absence of soft tissue swelling reduces, but does not rule out, the possibility of underlying injury. Fourth, have knowledge of those subtle injuries that have a tendency to be overlooked or missed. Look deliberately for evidence of such injuries. A passing glance at such sites is insufficient. Most often overlooked fractures are fine, incomplete, or nondisplaced fractures at common sites, such as the femoral neck, carpal scaphoid, distal radius, or lateral malleolus, that would be readily apparent if more pronounced. Or they are fractures at less common sites of injury, blind spots, where the observer simply fails to search and observe, such as the bases of the fourth or fifth metacarpals with or without dislocations of the associated carpohamate joints. Fifth, remain alert to the ever-present danger of satisfaction of search. Certain injuries tend to be associated with a second less-obvious injury. Having identified the first, the observer is satisfied and fails to seek the second. For example, fractures of the metatarsals and metacarpals are often multiple. Once you identify a metacarpal or metatarsal fracture, look closely at the adjacent bones for a similar though often less-obvious fracture. After identifying a fracture of the lateral or medial malleolus, look closely at the opposite malleolus and then the posterior malleolus for additional fractures. In most cases, as above, the additional fracture is to be found on the same radiographic examination as the first. No additional images are required. However, this is not always the case. In certain situations a second, additional examination is required. For instance, in a Maisonneuve fracture, a fracture of the ankle is associated with a fracture of the proximal fibula. The presenting injury of the ankle is commonly either a widening of the syndesmosis or an isolated fracture of the posterior malleolus, whereas the distal fibula and lateral malleolus characteristically remain intact. In this setting, having seen no fracture of the lateral malleolus or distal fibula, additional radiographs of the proximal tibia and fibula are required to disclose the accompanying fracture of the proximal shaft or neck of the fibula, the hallmark of a Maisonneuve fracture. Be aware of these associations and, having identified the first, obtain the appropriate additional radiographs, and look for the oft-associated second injury. 1

2   

  Introduction

The Imaging and Detection of Skeletal Trauma

     

This work consists of an introduction and 11 chapters centered on the primary components of the peripheral skeleton (shoulder, elbow, wrist, hand, hip, knee, ankle, and foot) and axial skeleton (cervical spine, thoracolumbar spine, and pelvis). Each chapter consists of two parts: the first, the Checklists, a series of checklists, and the second, the Primer, a short explanatory text based on the checklists.

serve as an immediately available resource when interpreting images of skeletal trauma. Each chapter contains a set of six separate checklists as ­follows:

1. Radiographic examination 2. Common sites of injury in adults 3. Common sites of injury in children and adolescents 4. Injuries likely to be missed 5. Where else to look when you see something obvious 6. Where to look when you see nothing at all The Checklists for the elbow provide an example.

Checklists Checklists were devised to promote a disciplined approach to the interpretation of images obtained to assess skeletal trauma. The Checklists contain the most important characteristics and considerations employed in the interpretation of imaging in this setting. Why checklists? According to Wikipedia, “a checklist is a type of informational job aid used to reduce failure by compensating for potential limits of human memory and attention. It helps ensure consistency and completeness in carrying out a task.” Checklists were first devised for use in aviation initially to prevent pilot errors and subsequently as a means of addressing critical in-flight emergencies. These checklists have proven highly effective and are now the backbone of air safety. I first heard of aviation checklists from Dr. David Levin, a renowned academician and interventional radiologist, who, prior to radiology, was an F-86 Sabre jet fighter pilot, during the Cold War with our then Russian adversaries. As a pilot he found checklists of great value and subsequently came to realize they would be helpful in medicine as well. Dr. Levin was particularly a champion of the use of checklists as an aid in the performance of interventional procedures. The use of checklists in surgery has recently been publicized in a January 2009 article in the New England Journal of Surgery (1) and in a more recent book The Checklist Manifesto (2) by Dr. Utal Gawande, a Harvard surgeon. These reports attribute to the use of checklists both a significant reduction in surgical errors as well as an improvement in patient outcomes due to a reduction in postoperative complications. In my view, checklists are a listing of summary statements compiled to direct the steps in the performance of a specific task. Checklists can be simple, straightforward, and are readily comprehended. Checklists can be quickly reviewed before, during, or after the performance of a specific task. I believe, as does Dr. Levin, that there is a role for checklists in radiology, in this case, a role in the reduction of errors and oversights in the performance and interpretation of all forms of imaging obtained for the assessment of skeletal trauma. A separate set of checklists is included for each chapter centered on the major joints in the peripheral skeleton and the individual sections of the axial skeleton. Separate checklists are required for each chapter to properly address the unique imaging features of the anatomy and traumatic injuries encountered in that anatomic area. These checklists can

1. Radiographic examination:  a listing of the standard views that should be obtained to analyze the anatomic area in question properly. In the aggregate these views allow the visualization of essentially all fractures and dislocations in the anatomic area examined. For instance, oblique views are required at essentially every peripheral joint in the extremities because a significant percentage of certain fractures are not visible in either the anteroposterior (AP) or lateral projections.

1. Radiographic examination AP External oblique Lateral 2. Common sites of injury in adults: a listing of the common fractures that includes the sites of the majority of injuries encountered in this anatomic area in adults. All such sights should be included in a search for fractures. The routine use of a structured, specific search pattern reduces the chance of diagnostic errors and oversights.

2. Common sites of injury in adults – Look here in adults. Radial head and neck Olecranon Coronoid process of ulna Distal humerus 3. Common sites of injury in children and adolescents: a listing of the common fractures that includes the sites of the majority of injuries encountered in this anatomic area in children and adolescents. All such sights should be included in a search for fractures.

3. Common sites of injury in children and adolescents – Look here in children and adolescents. Supracondylar of the distal humerus Salter-Harris type 4 of lateral condyle Avulsion of the medial epicondyle Olecranon Radial head epiphyseal separation 4. Injuries likely to be missed:  a listing of those injuries in this anatomic area that are frequently missed or overlooked and thus fail to be diagnosed.

4. Injuries likely to be missed Monteggia fracture dislocations Missing radial head dislocation Fine, subtle fractures of the radial head and neck

Introduction 

5. Where else to look when you see something obvious: In order to prevent errors due to satisfaction

of search, a listing of primary injuries encountered in this anatomic region commonly associated with secondary local or remote injuries is presented. The primary injuries are readily diagnosed, but secondary injuries may not be suspected and are easily overlooked. 5. Where else to look when you see something obvious Obvious

Look for

Fx proximal ulna

Dislocation proximal radius (Monteggia) Fx or dislocation of the other

Fx shaft of either radius or ulna Fx radial head and neck

Fx olecranon

6. Where to look when you see nothing at all: a listing of those features and sites that should be more closely examined for evidence of an abnormality. This includes soft tissue findings that identify a joint effusion and sites of injuries that often can be subtle or obscure and overlooked

A

by the unwary. The indications for the use of CT and MRI are presented. In general, if you note a finding on the radiograph but are uncertain if it represents a fracture, computed tomography (CT) will clarify this problem by either disclosing or excluding the possibility of a fracture. On the other hand, if even in the face of a negative radiographic examination the clinical findings are such that the clinician remains seriously concerned about the possibility of a significant injury, then MRI is warranted in search of a radiographically imperceptible fracture or ligamentous injury. 6. Where to look when you see nothing at all Look for joint effusion – the fat pad sign If present intraarticular fracture likely In adults look at Radial head and neck for fine fracture line Make certain you have external oblique view. Check tip of coronoid process for small avulsion. In children check anterior humeral line to Identify subtle supracondylar fracture.

The Primer The Primer is a short, illustrated text highlighting the specific imaging features of the common fractures and dislocations related to the area under consideration. This discussion is augmented with anatomic drawings of the skeletal system as seen on radiographs (Figures 1-1A and B). They show the sites and course of the common fractures in red lines: the most common fractures in thick red lines and the less common in thin red lines. A series of select high-quality clinical radiographs, CT, and MRI images illustrates the principal findings described in the text covering each separate checklist. Fractures of the radial head (Figure 1-2A) and olecranon (Figure 1-2B) are shown. Once armed with this disciplined approach, the ability to interpret images of skeletal trauma is enhanced. One becomes more comfortable and confident in an ability to assess skeletal trauma. The end result is greater accuracy and a substantial reduction in the ever-present fear of overlooking and failing to diagnose significant injuries.

B

FIGURE 1-1  A, B, Anatomic drawings of the skeletal system as seen on radiographs.

A

   3

B FIGURE 1-2  Fractures of the radial head (A) and olecranon (B).

4   

  Introduction

Suggested Readings Checklists 1. Haynes AB, et al. A surgical safety checklist to reduce morbidity and mortality in a global population. New England Journal of Medicine. 2009;360:491–499. 2. Gawande A. The Checklist Manifesto. New York: Metropolitan Books, Henry Holt and Company; 2009. 3. Levin DC. Checklists: From the cockpit to the radiology department. Journal of the American College of Radiology. 2012;9:388–390. Satisfaction of Search 4. Ashman CJ, Yu JS, Wolfman D. Satisfaction of search in osteoradiology. American Journal of Roentgenology. 2000;177:252–253. 5. Berbaum KS, El-Khoury GY, Franken Jr , et al. Missed fractures resulting from satisfaction of search effect. Emergency Radiology. 1994;1:242–249. 6. Fleck MS, Samei E, Mitroff SR. Generalized “satisfaction of search”: Adverse influences on dual-target search accuracy. J Exp Psychol Appl. 2010 Mar;16(1):60–71. http://dx.doi.org/10.1037/a0018629.

Missing Fractures 7. Berlin L. Defending the “Missed” radiographic diagnosis. American Journal of Roentgenology. 2001;176(2):317–322. 8. Hu CH, Kundell HL, Nodine CF, et al. Searching for bone fractures: a comparison with pulmonary nodule search. Acad. Radiol. 1994;1:25–32. 9. Pinto A, Brunese L. Spectrum of diagnostic errors in radiology. World J Radiol. 2010;2:377–383. 10. Robinson PJ, Wilson D, Coral A, et al. Variation between experienced observers in the interpretation of accident and emergency radiographs. Br J Radiol. 1999;72:323–330. 11. Tuddenham WJ. Visual search, image organization, and reader error in roentgen diagnosis: Studies of the psycho-physiology of roentgen image perception. Radiology. 1962;78:694–704. 12. Wood G, Knapp KM, et al. Visual expertise in detecting and diagnosing skeletal fractures. Skeletal Radiol. 2013;42:165–172.

CHAPTER 2

The Shoulder Shoulder Checklists

     

1. Radiographic examination AP external rotation AP internal rotation Axillary view Y-view Grashey (posterior oblique) view

2. Common sites of injury in adults Fractures Midshaft of clavicle Avulsion of the greater tuberosity of the humerus Surgical neck of the humerus Dislocations Acromioclavicular joint dislocation Dislocation of the glenohumeral joint Anterior dislocation Posterior dislocation Luxatio erecti

3. Common sites of injury in children and adolescents Greenstick fracture midshaft of clavicle Acromioclavicular joint dislocation Epiphyseal separation proximal humerus Pathologic fracture of unicameral bone cyst (UBC) of proximal humerus

4. Injuries likely to be missed Posterior dislocation of the shoulder (glenohumeral) joint Injuries in and about the sternoclavicular joint Sternoclavicular dislocations Fractures of the medial clavicle

5. Where to look when you see nothing at all Check again for findings to suggest a posterior dislocation of the glenohumeral joint. Is the joint space widened? Is the humeral head fixed in internal rotation? Look closely at the rim of the glenoid fossa, particularly the anterior rim, on the AP view. Is the ovoid rim intact?

Look for a subtle, nondisplaced fracture of the mid-clavicle. Need clear view of the mid-clavicle, free of the underlying ribs and scapula. AP view with 15° of cephalic angulation may be required to disclose the fracture.

Shoulder – the Primer

     

1. R  adiographic examination AP external rotation AP internal rotation Axillary view Y-view Grashey (posterior oblique) view

The standard radiographic examination of the traumatized shoulder should include at least three of the five standard views listed above. These have been selected because they have proven to disclose the majority of fractures and dislocations. My personal preferences are the four illustrated (Figure 2-1). Two AP views should be obtained, one with the humerus in external rotation and the second with the humerus in internal rotation (Figure 2-1A, B). The Grashey or posterior oblique view (Figure 2-1C) is a tangential view of the glenohumeral joint obtained with 35° posterior rotation of the shoulder. This view is particularly useful in disclosing fractures of the anterior glenoid rim and confirming the presence of a posterior (glenohumeral) shoulder dislocation as identified by an overlap of the humeral head and glenoid in this projection. The axillary view (Figure 2-1D) also depicts the glenohumeral joint and margins of the glenoid to good advantage and therefore is useful in identifying glenoid rim and coracoid fractures as well as dislocations of the glenohumeral joint.

2. C  ommon sites of injury in adults Fractures Midshaft of clavicle Avulsion of the greater tuberosity of the humerus Surgical neck of the humerus Dislocations Acromioclavicular joint dislocation Dislocations of the glenohumeral joint Anterior dislocation Posterior dislocation

5

6   

A

  The Shoulder

B

C

D

FIGURE 2-1  The standard radiographic examination of the traumatized shoulder. Two AP views should be obtained, one with the humerus in external rotation (A) and the second with the humerus in internal rotation (B). C, The Grashey or posterior oblique view is a tangential view of the glenohumeral joint obtained with 35° posterior rotation of the shoulder. D, The axillary view depicts the glenohumeral joint and margins of the glenoid to good advantage.

A

FIGURE 2-2  Diagrams of the shoulder pinpoint the common sites of fracture and dislocation in adults.

Pattern of search. Diagrams of the shoulder (Figure 2-2) pinpoint the common sites of fracture and dislocation in adults. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites.

B FIGURE 2-3  A, Undisplaced clavicle fracture. B, Displaced and comminuted clavicle fracture.

Clavicle fractures. Eighty plus percent of fractures occur

in the midshaft. They may be nondisplaced (Figure 2-3A) or displaced and comminuted, commonly with elevation of the medial fragment (Figure 2-3B). Fractures of the outer third may involve the AC joint and disrupt the coracoclavicular ligament. Fractures of the medial third are uncommon. Acromioclavicular dislocations. In the normal AC joint the

inferior cortex of the outer end of the clavicle aligns with the under-surface of the acromion (Figures 2-4A). The width of the normal AC joint is 4 to 6 mm. The normal distance between the superior tip of the coracoid process and inferior surface of the adjacent clavicle is approximately 1.2 cm. Disruption of the coracoclavicular ligaments results in an increase in this distance. Acromioclavicular dislocations vary from a simple sprain manifest by widening of the AC joint, to disruption of the

joint with slight elevation of the clavicle with intact coracoclavicular ligaments (Figure 2-4B), to complete disruption of the joint with elevation of the outer end of the clavicle and tears of the coracoclavicular ligaments increasing the coraclavicular distance (Figure 2-4C). Acromioclavicular dislocations may require weight-bearing views to disclose the true extent or even the presence or absence of injury. Weight-bearing views are not required if the outer clavicle is elevated and the coracoclavicular distance is increased above 1.2 cm. In any other circumstance with a clinical suspicion of AC joint injury, weight-bearing views should be obtained to determine the full extent of the injury. Rockwood classification of AC joint dislocations (Figure 2-5).  Type I consists of a sprain of the ligaments about the

The Shoulder 

A

B

   7

C

FIGURE 2-4  A, Normal acromioclavicular joint where the inferior cortex of the outer end of the clavicle aligns with the under-surface of the acromion. B, Acromioclavicular dislocation with slight elevation of the clavicle with intact coracoclavicular ligaments. C, Complete disruption of the joint with elevation of the outer end of the clavicle and tears of the coracoclavicular ligaments increasing the coracoclavicular distance.

Type I

Type II

Type III

Type IV

Type V

Type VI

FIGURE 2-5  Rockwood classification of AC joint dislocations.  Type I consists of a sprain of the ligaments about the joint. There is no displacement of the clavicle or widening of the joint. The radiographic findings are normal. Type II is a subluxation of the AC joint. The outer end of the clavicle is slightly elevated in relation to the acromion, and the AC joint may be widened, but the clavicular ligaments remain intact, and the coracoclavicular distance is normal. In Type III the coracoclavicular ligaments are disrupted, and the distance between the clavicle and coracoid is increased, >1.2 cm. The clavicle is elevated. Type IV is a posterior dislocation of the clavicle. The outer end of the clavicle pierces into or through the trapezius muscle. The clavicle may be elevated or, at times, depressed. Posterior displacement can be seen on the axillary or Y views. In Type V the clavicle is markedly elevated and lies subcutaneously. The clavicle is at least partially detached from its muscle attachments. Type VI is an inferior dislocation wherein the outer end of the clavicle comes to rest beneath the coracoid process posterior to the coracobrachialis tendon.

8   

  The Shoulder

joint. There is no displacement of the clavicle or widening of the joint. The radiographic findings are normal. Type II is a subluxation of the AC joint. The outer end of the clavicle is slightly elevated in relation to the acromion, and the AC joint may be widened, but the clavicular ligaments remain intact, and the coracoclavicular distance is normal. In Type III the coracoclavicular ligaments are disrupted, and the distance between the clavicle and coracoid is increased >1.2 cm. The clavicle is elevated. Type IV is a posterior dislocation of the clavicle. The outer end of the clavicle pierces into or through the trapezius muscle. The clavicle may be elevated or, at times, depressed. Posterior displacement can be seen on the axillary or Y views. In Type V the clavicle is markedly elevated and lies subcutaneously. The clavicle is at least partially detached from its muscle attachments. Type VI is an inferior dislocation wherein the outer end of the clavicle comes to rest beneath the coracoid process posterior to the coracobrachialis tendon. Proximal humerus fractures. Avulsions of the greater

tuberosity occur either in isolation or in association with fractures of the surgical neck of the humerus (Figure 2-6A). Fractures of the surgical neck are particularly common in the elderly with or without (Figure 2-6B) associated avulsions of the greater tuberosity. With fractures of the humeral head and/or neck, the humeral head may be displaced inferiorly giving the appearance of an

B

A

FIGURE 2-6  Proximal humerus fractures.  A, Avulsions of the greater tuberosity occur either in isolation or in association with fractures of the surgical neck of the humerus. B, Fractures of the surgical neck are particularly common in the elderly with or without associated avulsions of the greater tuberosity.

A

B

inferior dislocation of the glenohumeral joint (Figure 2-6B). The displacement is due to a large volume hemarthrosis that commonly accompanies these fractures and is not considered to be a true dislocation. It is therefore referred to as a “pseudodislocation.” As the hemarthrosis resorbs, the normal relationship of the humeral head and glenoid is restored. Scapular fractures.  The body of the scapula is rarely injured

in simple falls; most occur in motor vehicle collisions. Fractures can be identified on radiographs of the chest (Figure 2-7A) but are much more clearly depicted by CT, particularly CT of the chest (Figures 2-7B and C), which is nearly always obtained in those who have sustained high impact trauma. The full extent of scapular fractures is best disclosed by CT with 3-D reconstruction (Figures 2-7C and 2-8C). Scapular fractures involving the glenoid, acromion, and coracoid process also occur in association with glenohumeral and/or acromioclavicular dislocations (Figure 2-8). Fractures of the acromion, coracoid process, and superior border of scapula associated with a posterior dislocation of the glenohumeral joint are shown in Case 1 (Figure 2-8A). Note the humeral head is in internal rotation, and the distance between it and the anterior rim of the glenoid is widened indicating a posterior dislocation of the glenohumeral joint (Figure 2-8A). In Case 2 (Figures 2-8B and C) an acromioclavicular dislocation and fracture of the superior border of the scapula and coracoid are shown. Note AC dislocation and associated fracture of acromion. The scapular fracture is barely visible on this AP view of the shoulder (Figure 2-8B). However, this fracture of the superior border of the scapula is nicely shown by CT 3-D reconstruction (Figure 2-8C). Fractures of the glenoid rim are created by an impact of the humeral head against the anterior inferior margin of the glenoid during a transient or complete anterior dislocation of the glenohumeral joint. The fracture fragment is displaced inferior and medial. The fracture is usually better seen on the post-reduction radiographs. Look closely at the anterior rim of the glenoid on the AP projections (Figure 2-9A). Is the ovoid rim density intact? Anterior glenoid rim fractures are best seen on the Grashey projection (Figure 2-9B) or axillary view. Obtain these views if you have not already done so. If questionable, quit fooling around; get a CT. Fracture of the anterior inferior glenoid rim associated with an anterior dislocation of the glenohumeral joint is shown in Figures 2-9C and D. The initial AP view clearly demonstrates the subcoracoid anterior dislocation (Figure 2-9C). Note: underlying the humeral head is a small bony fragment

C

FIGURE 2-7  Scapular fractures.  A, Radiograph of the chest. B, (Axial) C, (3D reformat) CTs of the chest.

The Shoulder 

adjacent to the glenoid at the 7 o’clock position. This is an avulsion fracture of the glenoid rim. There is also a small bony fragment just interior to the medial margin of the coracoid on this view. Note that this small glenoid rim fracture is better seen on the postreduction AP view (Figure 2-9D).

head is displaced anterior, medial, and inferior, coming to rest beneath either the coracoid process (subcoracoid) (Figure 2-10A) or glenoid process (subglenoid) (Figure 2-10B). Subcoracoid is by far the most common. Fractures of the anterior inferior rim of the glenoid are frequent and often best seen on the postreduction views (see Figure 2-9). A characteristic impaction fracture of the humeral head may occur during an anterior dislocation as the humeral head becomes impaled on the anterior inferior margin of the glenoid

Glenohumeral dislocations.  Dislocations are more common

in the shoulder than at other major joints. Anterior dislocations account for 95% of all glenohumeral dislocations. The humeral

A

   9

B

C

FIGURE 2-8  A, B, C, Scapular fractures involving the glenoid, acromion, and coracoid process also occur in association with glenohumeral and/or acromioclavicular dislocations.

A

C

B

D

FIGURE 2-9  A, An anterior glenoid rim fracture on AP projection. B, Anterior glenoid rim fractures are best seen on the Grashey projection or axillary view. C, D, Fracture of the anterior inferior glenoid rim associated with an anterior dislocation of the glenohumeral joint.

A

B

FIGURE 2-10  Glenohumeral dislocations are more common in the shoulder than at other major joints. Anterior dislocations account for 95% of all glenohumeral dislocations. The humeral head is displaced anterior, medial, and inferior, coming to rest beneath either the coracoid process (subcoracoid) (A) or glenoid process (subglenoid) (B).

10   

  The Shoulder

A

B

C

FIGURE 2-11  A, B, C, A characteristic impaction fracture of the humeral head may occur during an anterior dislocation, as the humeral head becomes impaled on the anterior inferior margin of the glenoid.

(Figures 2-11A, B, C). The impaction, commonly referred to as a Hill-Sachs defect, is located in the posterolateral aspect of the humeral head at the margin of joint surface. The defect can lead to recurrent dislocations. The Hill-Sachs defect may interfere with the reduction of an anterior dislocation as it did in the case shown. The defect is best demonstrated by CT (Figures 2-11B, axial, and C, coronal reconstruction) or MRI. Posterior dislocations. While accounting for only 4% of

shoulder dislocations, posterior dislocations can be difficult to recognize and, in fact, are frequently overlooked on the initial examination. See section [4]. Luxatio erecti. Luxatio erecti is a rare, yet devastating,

dislocation of the glenohumeral joint with typical radiographic findings that allow an immediate diagnosis when recognized. Typically the arm is elevated and abducted, the elbow is flexed, and the forearm rests on the top of the head (Figure 2-12A). The humeral head is displaced, medial and inferior to the glenoid. Accompanying injuries of the axillary nerve and artery are frequent; ruptures of the rotator cuff, displacement and tears of the long head of the biceps, and fractures of the humeral head, greater tuberosity (Figure 2-12B), and glenoid are common.

A

B

FIGURE 2-12  Luxatio erecti is a dislocation of the glenohumeral joint with typical radiographic findings that allow an immediate diagnosis when recognized. Typically the arm is elevated and abducted, the elbow is flexed, and the forearm rests on the top of the head (A). The humeral head is displaced, medial and inferior to the glenoid. Accompanying injuries of the axillary nerve and artery are frequent; ruptures of the rotator cuff, displacement and tears of the long head of the biceps, and fractures of the humeral head, greater tuberosity (B), and glenoid are common.

3. Common sites of injury in children and adolescents Greenstick fracture midshaft of clavicle Acromioclavicular joint dislocation Epiphyseal separation proximal humerus Pathologic fracture of unicameral bone cyst (UBC) of ­proximal humerus Pattern of search.  Diagrams of the shoulder (Figure 2-13)

pinpoint the common sites of fracture and dislocation in children and adolescents. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites. By far the most common skeletal injury of the shoulder in children and adolescents is a fracture of the midshaft of clavicle, which is frequently of the greenstick variety (Figure 2-14A). Acromioclavicular dislocations are relatively common in the adolescent (Figure 2-14B). Note widening of the AC joint and slight elevation of the outer end of the

FIGURE 2-13  Diagrams of the shoulder pinpoint the common sites of fracture and dislocation in children and adolescents.

The Shoulder 

clavicle. Salter-Harris types 1 and 2 epiphyseal separations of the proximal humerus occur after the age of 10 (Figure 2-14C). Less common are pathologic fractures occurring in unicameral (simple) bone cysts (UBC), which present as a cystic,

   11

expansile lesion characteristically found in the proximal metadiaphysis of the proximal humerus (Figure 2-15). This is the classic location for UBCs, which often present with a pathologic fracture as the first evidence of disease. The radiographic findings are pathognomonic.

A

B

C

FIGURE 2-14  A, Fracture of the midshaft of clavicle, which is frequently of the greenstick variety. B, Acromioclavicular dislocations are relatively common in the adolescent. C, Salter-Harris type 1 and type 2 epiphyseal separations of the proximal humerus occur after the age of 10.

A

B

FIGURE 2-15  A, B, Pathologic fractures occurring in unicameral (simple) bone cysts (UBC), which present as a cystic, expansile lesion ­characteristically found in the proximal metadiaphysis of the proximal humerus.

12   

  The Shoulder

4. Injuries likely to be missed Posterior dislocation of the shoulder (glenohumeral) joint Injuries in and about the sternoclavicular joint Sternoclavicular dislocations Fractures of the medial clavicle Posterior dislocations of the glenohumeral joint. Posterior

dislocations are, by far, the most frequently overlooked injury in the shoulder, if not in the entire peripheral skeleton. The diagnosis has been reported as missed on the initial radiographic examination in as many as 40% to 60% of cases. So be aware. Missing the diagnosis of a posterior dislocation of the shoulder is a common source of malpractice suits. The radiographic findings can be subtle and are easily overlooked. The glenohumeral joint is virtually always fixed in internal

A

rotation, and the joint space (as measured from the medial margin of the humeral to the anterior rim of the glenoid) is widened (>6 mm) in 60% to 70% of cases (Figures 2-16A and B). There is often a fracture of the lesser tuberosity (Figure 2-16B). There are two other important signs of posterior dislocation; the trough line, a linear vertical or curvilinear line located in the medial aspect of the humeral head, and the humeral head commonly overlap the glenoid on the Grashey or posterior oblique projection. Note trough line (arrow) indicating compression fracture of anterior medial humeral head (Figure 2-17A). Note also internal rotation of humeral head and wide joint space findings typical of posterior dislocation of the glenohumeral joint. Grashey view demonstrates overlap of humeral head and glenoid due to posterior dislocation of the humeral head (Figure 2-17B).

B

FIGURE 2-16  A, B, The glenohumeral joint is virtually always fixed in internal rotation, and the joint space (as measured from the medial margin of the humeral to the anterior rim of the glenoid) is widened (>6 mm) in 60% to 70% of cases.

A

B

FIGURE 2-17  There are two other important signs of posterior dislocation; the trough line, a linear, vertical, or curvilinear line located in the medial aspect of the humeral head, and the humeral head commonly overlap the glenoid on the Grashey or posterior oblique projection. Note trough line (arrow) indicating compression fracture of anterior medial humeral head (A). Note also internal rotation of humeral head and wide joint space findings typical of posterior dislocation of the glenohumeral joint. Grashey view demonstrates overlap of humeral head and glenoid due to posterior dislocation of the humeral head (B).

The Shoulder 

Sternoclavicular joint and medial clavicle.  Dislocations of

the sternoclavicular joint and fractures of the medial clavicle are notoriously difficult to see on radiographs, regardless of their projection. Therefore, when injuries of the medial clavicle or sternoclavicular joint are suspected, CT is advised. CT will safely and with certainty disclose or exclude the presence of significant abnormalities as shown by the following case of a left posterior sternoclavicular dislocation (Figure 2-18). On the AP view the left clavicle is displaced superiorly as compared to the right clavicle. Axial CT clearly identifies a posterior dislocation of left clavicle.

5. Where to look when you see nothing at all Check again for findings to suggest a posterior dislocation of the glenohumeral joint. Is the joint space widened? Is the humeral head fixed in internal rotation? Look closely at the rim of the glenoid fossa, particularly the anterior rim, on the AP view. Is the ovoid rim intact? Look for a subtle, undisplaced fracture of the mid-clavicle. Need clear view of the mid-clavicle, free of the underlying ribs and scapula. AP view with 15° of cephalic angulation may be required to disclose the fracture. If no findings on x-rays, but the clinician remains convinced that an injury has occurred Obtain an MRI. If there are questionable radiographic findings Get a CT to confirm or exclude an abnormality.

The emergency physician calls and says he is really concerned about an injury in Mr. Calderon’s shoulder, but you had not seen anything at all when you viewed the radiographs. What now?

A

   13

First, check again for findings to suggest a posterior dislocation of the glenohumeral joint (see Figures 2-16 and 2-17). Is the joint space widened? Is the humeral head fixed in internal rotation? You may need a Grashey or axillary view to identify the position of the humeral head. If still not certain, get a CT. Second, look closely at the rim of the glenoid, particularly the anterior rim, on the AP projections (Figure 2-9A). Is the ovoid rim density intact? A segment of the anterior inferior rim may be disrupted and displaced medially. This is best seen on the Grashey projection or axillary view (Figure 2-9B). Obtain these views if you have not already done so. If findings noted on the radiographs are questionable, get a CT. In adolescents, look for an obscure proximal humeral epiphyseal separation. Is the physis widened? In children and adolescents, check to make sure you have a clear view of the mid-clavicle free of the underlying ribs and scapula (Figure 2-19A). You may require a view of the clavicle with 15° of cephalic angulation to accomplish this (Figure 2-19B). Look closely for a subtle undisplaced fracture (Figure 2-19C). Note callus formation about fracture on two-week follow-up examination (Figure 2-19D). In general, if there are questionable radiographic findings, they would most likely be resolved by a CT examination. If you see no findings on the radiographs, and the clinician remains convinced that a significant injury has occurred, obtain an MRI (Figures 2-20A, B, and C). The clinical history is a question of shoulder instability. The radiographic examination was unrevealing as exemplified by the AP view (Figure 2-20A). Axial T2W MRI (Figure 2-20B) shows HillSachs lesion. Note defect in the posterolateral aspect of the humeral head just lateral to the posterior joint surface. Coronal T2W MRI (Figure 2-20C) shows fracture of anterior glenoid rim (Bankhart lesion) which remains attached to the glenoid by a strip of periosteum. Findings indicate patient has experienced a transient anterior dislocation of the glenohumeral joint.

B

FIGURE 2-18  Sternoclavicular joint and medial clavicle.  A, B, On the AP view the left clavicle is displaced superiorly as compared to the right clavicle. Axial CT clearly identifies a posterior dislocation of left clavicle.

14   

  The Shoulder

A

B

C

D

FIGURE 2-19  In children and adolescents, check to make sure you have a clear view of the mid-clavicle free of the underlying ribs and scapula (A). You may require a view of the clavicle with 15º of cephalic angulation to accomplish this (B). Look closely for a subtle nondisplaced fracture (C). Note callus formation about fracture on two-week follow-up examination (D).

A

B

C

FIGURE 2-20  The radiographic examination was unrevealing, as exemplified by the AP view (A). Axial T2W MRI (B) shows Hill-Sachs lesion. Coronal T2W MRI (C) shows fracture of anterior glenoid rim (Bankhart lesion), which remains attached to the glenoid by a strip of periosteum. Findings indicate patient has experienced a transient anterior dislocation of the glenohumeral joint.

CHAPTER 3

The Elbow Elbow Checklists

     

1. Radiographic examination AP External oblique Lateral

2. Elbow joint effusions and the fat pad sign Visible posterior fat pad Elevation of the anterior fat pad, the sail sign

3. Common sites of injury in adults Radial head and neck Olecranon Coronoid process of ulna Distal humerus

4. Common sites of injury in children and adolescents Supracondylar of the distal humerus Salter-Harris type 4 of lateral condyle Avulsion of the medial epicondyle Olecranon

5. Injuries likely to be missed Monteggia fracture dislocations Missing radial head dislocation Fine, subtle fractures of the radial head and neck Radial head epiphyseal separation

6. Where else to look when you see something obvious Obvious

Look for

Ex proximal ulna Fx shaft of either radius or ulna Fx radial head and neck

Dislocation proximal radius Fx or dislocation of the other Fx olecranon

7. Where to look when you see nothing at all Look for joint effusion – the fat pad sign. If present intraarticular fracture likely

In adults look at Radial head and neck for fine fracture line Make certain you have external oblique view. Check tip of coronoid process for small avulsion. In children check anterior humeral line to Identify subtle supracondylar fracture.

Elbow – the Primer

     

1. R  adiographic examination AP External oblique Lateral

The three views (Figure 3-1) selected have been proven to disclose the majority of fractures and dislocations. Certain injuries can be inapparent on standard PA (Figure 3-1A) and lateral (Figure 3-1B) projections and may be seen only on the external oblique view (Figure 3-1C). This is particularly true of fractures of the radial head, accounting for over one-half of all fractures (60%) of the elbow in adults. Normal elbow in children. The presence and sequential

appearance of multiple ossification centers in the child’s elbow (Figures 3-2A and B), particularly in the distal humerus, makes for complex and potentially confusing anatomy. The capitellum is the first to appear at 3 to 5 months of age, followed by the medial epicondyle center at 4 to 6 years of age. The trochlear center appears at age 9 to 10 years. Note that the trochlear center never appears before the medial epicondylar center. The last center to appear is the lateral epicondyle at 9.4 to 11.5 years. Note the normal ossification center of the apophysis of the olecranon (Figures 3-2C). This center is multipartite, a normal variant.

2. E  lbow joint effusions and the fat pad sign Visible posterior fat pad Elevation of the anterior fat pad, the sail sign

In the setting of trauma it is very likely that an intraarticular fracture is present if a joint effusion is identified. The presence of a joint effusion is an important clue to an otherwise obscure underlying fracture of the elbow in adults as well as children and adolescents. Elbow joint effusions are detected on the lateral view (Figure 3-3). The anterior and posterior fat pads reside in the joint capsule. On the lateral view of the normal elbow (Figures 3-3A and C) without a joint effusion, the posterior fat pad is not 15

16   

  The Elbow

A

B

C

FIGURE 3-1  Certain injuries can be unapparent on standard posteroanterior (A) and lateral (B) projections and may be seen only on the external oblique view (C).

Lateral epicondyle (9.5 to 11.5 years)

Medial epicondyle (4 to 6 years)

Capitellum (3 to 6 months)

A

Trochlea (9 to 10 years)

B

C

FIGURE 3-2  The presence and sequential appearance of multiple ossification centers in the child’s elbow (A and B), particularly in the distal humerus, makes for complex and potentially confusing anatomy. Normal ossification center of the apophysis of the olecranon (C). This center is multipartite, a normal variant.

apparent, while the anterior fat pad is visible but not elevated. In the presence of a joint effusion (hemarthrosis), the fat pads are displaced, and both the anterior and posterior fat pads become visible (Figures 3-3B and D). This is known as the “fat pad sign.” The posterior fat pad is displaced posteriorly, and the anterior fat pad is elevated, often referred to as the “sail sign.” Note the subtle fracture of the radial head (Figure 3-3D).

3. Common sites of injury in adults Radial head and neck Olecranon Coronoid process of ulna Distal humerus

Pattern of search.  Diagrams of the elbow (Figures 3-4A and

B) pinpoint the common sites of fracture in adults. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites. In adults, fractures of the radial head and neck account for approximately 50% to 60% of elbow fractures. Most radial head fractures are readily identified by obvious disruption of the radial joint surface (Figure 3-5A). The “double cortical line” due to slight depression of a portion of the articular surface is a frequent and characteristic finding in radial head fractures (Figures 3-5B and C). Note the stepoff of the joint surface on the lateral view (Figure 3-5C) in this case.

The Elbow 

Anterior fat pad Posterior fat pad Joint capsule Fibrous layer Synovial layer

Joint capsule Fibrous layer Synovial layer

A

Posteriorly displaced posterior fat pad

   17

Elevated perpendicular anterior fat pad

B

C

D

FIGURE 3-3  Elbow joint effusions. On the lateral view of the normal elbow without a joint effusion (A and C), the posterior fat pad is not apparent, whereas the anterior fat pad is visible but not elevated. In the presence of a joint effusion (hemarthrosis), the fat pads are displaced, and both the anterior and posterior fat pads become visible (B and D). Note the subtle fracture of the radial head in panel D.

A

B

FIGURE 3-4  Diagrams of the elbow (A and B) pinpoint the common sites of fracture in adults. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines.

Fractures of the radial head are often not well seen on the AP view (Figure 3-6A) but are better seen and sometimes only apparent on the external oblique projection (Figure 3-6B). Similarly, fractures of the radial neck (Figures 3-6C and D) are at times more evident on the lateral view.

Fractures of the proximal ulna account for 20% of fractures in adults. Figure 3-7A represents a typical fracture of the olecranon. Avulsions of the coronoid process (Figure 3-7B) are frequent. They occur in isolation or in association with dislocations of the elbow. Intraarticular fractures of the distal humerus occur in MVCs and other high-impact trauma. These may be Y- or T-shaped (Figures 3-8A and B) and are often widely displaced. In this nondisplaced fracture note that the fracture line extends into the trochlear joint surface. Transcondylar, extraarticular fractures occur in the elderly from low-impact falls (Figures 3-8C and D). When nondisplaced they may be obscure. Look closely at this area for subtle fractures in the elderly. Fractures of the capitellum of the humeral joint surface can be perplexing. The lateral view shows a large fragment of bone above the radial head (Figure 3-9A). Closer inspection reveals that there is no articular bone opposing the joint surface of the radial head. The origin of the fragment is difficult to find on the AP projection (Figure 3-9B). Note the absence of the distal articular cortex of the capitellum. Closer inspection will disclose an arc of articular cortex overlying the capitellum at the level of the inferior margin of the olecranon fossa. This is the typical appearance of a displaced fracture of capitellum.

18   

  The Elbow

A

B

C FIGURE 3-5  Fractures of the radial head.

A

B

C

D

FIGURE 3-6  Fractures of the radial head are often not well seen on the anteroposterior view (A) but are better seen and sometimes only apparent on the external oblique projection (B). Similarly, fractures of the radial neck (C and D) are at times more evident on the lateral view.

A

B

FIGURE 3-7  A, Typical fracture of the olecranon. Avulsions of the coronoid process (B) are frequent.

4. Common sites of injury in children and adolescents Supracondylar of the distal humerus Salter-Harris type 4 of lateral condyle Avulsion of the medial epicondyle Olecranon Radial head epiphyseal separation

Pattern of search. Diagrams of the elbow (Figure 3-10) pinpoint the common sites of fracture and dislocation in

children and adolescents. The most common sites of fracture are identified by broad red lines. Your pattern of search should include all sites. In children, supracondylar fractures of the distal humerus account for 60% of elbow fractures, lateral condyle 15%, and avulsions of the medial epicondyle 15%; the remainder consists of fractures of the olecranon and separations of the epiphysis of the proximal radius. Supracondylar fracture. The majority of supracondylar fractures are clearly evident on the radiographs (Figures 3-11A

A

C

B

D

FIGURE 3-8  Intraarticular fractures of the distal humerus that occur in MVCs and other high-impact trauma may be Y- or T-shaped (A and B) and are often widely displaced. In this nondisplaced fracture the fracture line extends into the trochlear joint surface. Transcondylar, extraarticular fractures occur in the elderly from low-impact falls (C and D).

A

B

FIGURE 3-9  Displaced fracture of capitellum. A, Lateral view shows a large fragment of bone above the radial head. B, The origin of the ­fragment is difficult to find on the AP projection.

20   

  The Elbow

and B). However, a small percentage of cases are subtle and easily overlooked by the unwary. In a complete fracture the distal fragment is displaced posteriorly (Figures 3-11A and B). In an incomplete fracture the distal humeral joint surface is rotated posteriorly and more aligned with the humeral shaft.

B A FIGURE 3-10  A and B, Diagrams of the elbow pinpoint the common sites of fracture and dislocation in children and adolescents. The most common sites of fracture are identified by broad red lines.

FIGURE 3-11  A and B, The majority of supracondylar fractures in children are clearly evident on the radiographs.

FIGURE 3-12  In the normal pediatric elbow (A) the distal humeral joint surface at the elbow is flexed anteriorly at approximately 140° with long axis of the humeral shaft. The anterior humeral line is drawn down the anterior cortex of the distal humerus and passes through the middle third of the capitellum (B). In the presence of a bowing or greenstick-type supracondylar fracture, the line passes through the anterior third or anterior to the capitellum, indicating a rotation of the distal humeral joint surface (C).

A

A

The anterior humeral line is a useful adjunct in the diagnosis of subtle supracondylar fractures. In the normal elbow (Figure 3-12A) the distal humeral joint surface at the elbow is flexed anteriorly at approximately 140° with long axis of the humeral shaft. The anterior humeral line is drawn down the anterior cortex of the distal humerus and passes through the middle third of the capitellum (Figure 3-12B). In the presence of a bowing or greenstick supracondylar fracture, the line passes through the anterior third or anterior to the capitellum, indicating a rotation of the distal humeral joint surface (Figure 3-12C). Subtle, supracondylar greenstick fractures of the bowing type without distinct breaks in the humeral cortex can be difficult to recognize. The anterior humeral line is a valuable adjunct in establishing the diagnosis (Figure 3-13). Note the incomplete transverse supracondylar fracture on the AP view (Figure 3-13A). A joint effusion is shown on the lateral view (Figure 3-13B), but there is no apparent supracondylar fracture. Note, however, that the anterior humeral line would pass through the anterior third of the capitellum, indicating the presence of a supracondylar fracture (Figure 3-13B). Compare with normal opposite elbow (Figure 3-13C). Other common injuries. Fractures of the lateral condyle of the humerus are Salter-Harris type 4 epiphyseal separations. The fragment consists of the capitellum and a thinner segment of the lateral metaphysis. This fragment is usually rotated

B

B

C

The Elbow 

distally and posteriorly by the pull of the attached extensor tendons (Figure 3-14A). The medial epicondyle is the most common of these centers affected by elbow trauma consisting of avulsion and distraction of the center by the attached forearm flexor tendons (Figure 3-14B). (Compare with appearance of normal medial epicondylar ossification center in Figure 3-2B.) Always make it a point to determine the presence and position of the medial epicondyle ossification center in every case of trauma to the child’s elbow. Fractures of the radial head in children are usually SalterHarris type 2 epiphyseal separations (Figure 3-14C).

5. Injuries likely to be missed Monteggia fracture-dislocations Missing radial head component Fine, subtle fractures of the radial head and neck

Monteggia fracture-dislocations. Monteggia fracturedislocations are notorious for oversights. There are two components: a displaced fracture of the proximal third of the ulna (Figure 3-15A) associated with a dislocation of the radial

A

   21

head (Figure 3-15B). The ulnar fracture is readily identified, but the radial dislocation is often overlooked. This is likely due to the “satisfaction of search” phenomenon. When a fracture of the proximal third of the ulna is identified, you must make it a point to search specifically for the associated usually anterior dislocation of the radial head. The radiocapitellar line is useful for this purpose (Figure 3-15C). The line bisects the proximal end of the radius and should always extend through the capitellum. If the line fails to pass through the capitellum, the radial head is dislocated. Once you see the obvious injury, look for the often associated second injury. Obscure fractures of the radial head. Fractures of the radial head, the most common fracture of the elbow in adults, are, at times, impossible to see on either the AP or lateral views of the elbow. Their detection frequently requires an external oblique view. Therefore to prevent diagnostic oversights, the external oblique view should be obtained in all cases of elbow trauma. Subtle, nondisplaced fractures of the radial head are often not well seen on the AP view (Figure 3-16A) but are better seen and sometimes only apparent on the external oblique projection (Figure 3-16B). (See also Figure 3-6.)

B

C

FIGURE 3-13  The anterior humeral line is a valuable adjunct in establishing the diagnosis of subtle, supracondylar greenstick fractures of the bowing type without distinct breaks in the humeral cortex, which can be difficult to recognize. A, Incomplete transverse supracondylar fracture is shown on the AP view. B, A joint effusion is shown on the lateral view, but there is no apparent supracondylar fracture. Note, however, that the anterior humeral line would pass through the anterior third of the capitellum indicating the presence of a supracondylar fracture (B). C, Normal opposite elbow.

A

B

C

FIGURE 3-14  A, Fractures of the lateral condyle of the humerus are Salter-Harris type 4 epiphyseal separations. The fragment consists of the capitellum and a thinner segment of the lateral metaphysis. This fragment is usually rotated distally and posteriorly by the pull of the attached extensor tendons. B, Aversion and distraction of medial epicondyle. C, Fractures of the radial head in children are usually Salter-Harris type 2 epiphyseal separations.

22   

  The Elbow

B

C

A

FIGURE 3-15  There are two components to a Monteggia fracture-dislocation: a displaced fracture of the proximal third of the ulna (A) associated with a dislocation of the radial head (B). The ulnar fracture is readily identified, but the radial dislocation is often overlooked. When a fracture of the proximal third of the ulna is identified, make it a point to search specifically for the associated, usually anterior, dislocation of the radial head. The radiocapitellar line is useful for this purpose (C). Normal elbow. The line passes through the capittelum in all views.

6. Where else to look when you see something obvious Obvious

Look for

Fx proximal ulna Fx shaft of either radius or ulna Fx radial head and neck

Dislocation proximal radius Fx or dislocation of the other Fx olecranon

These types of pairings are found throughout the body. Be aware and look out for them. Ask yourself “Now that I have seen this injury, is there an associated second injury that I should be looking for?” Having recognized the obvious component, make sure you look for the often less-obvious, moreobscure second part of these pairings. Monteggia fracture-dislocation, as described in the previous section, is a good example of a paired injury. The obvious injury of these pairings is usually observed, but the associated injury is often more subtle and may be easily overlooked. Or the association may be unknown to the observer and not sought. Or, more likely, having found an injury, the observer may be satisfied and quit searching, a victim of the so-called “satisfaction of search” phenomenon.

7. Where to look when you see nothing at all Look for joint effusion – the fat pad sign. If present, intraarticular fracture likely In adults look at Radial head and neck for fine fracture line Make certain you have external oblique view. Check tip of coronoid process for small avulsion. In children check anterior humeral line to Identify subtle supracondylar fracture.

The emergency physician calls and says she is really concerned about an injury in Miss Jones’s elbow, but you had not seen anything at all when you viewed the radiographs. What now? Ask specifically where she hurts. Look there. Look specifically at the common sites of elbow fractures. Look for a joint effusion as evidenced by the fat pad sign. Do you have all the standard views? You have PACs. Magnify the areas in question. Reverse the image and use the edge enhancement sequences. If all are negative you may have to repeat the examination in 7 to 10 days, but if there is sufficient clinical concern, you should consider CT or MRI depending on the circumstances. If there are radiographic findings present, no matter how

The Elbow 

A

   23

FIGURE 3-16  Subtle, nondisplaced fractures of the radial head are often not well seen on the AP view (A) but are better seen and sometimes only apparent on the external oblique projection (B).

B

*

A

B

FIGURE 3-18  This 40-year-old woman fell on her outstretched hand several weeks earlier and experienced continued pain and limitation of motion. T1 MRI reveals a nondisplaced fracture (arrow) of the radial head.

FIGURE 3-17  This 29-year-old man fell on his outstretched hand, and the initial radiographic examination was normal. T1 MRI demonstrates a contusion (arrow) of the radial head and neck (A and B). Note also the hemarthrosis (asterisk).

subtle, a CT examination with image reconstruction in the coronal and sagittal planes will likely resolve the ambiguities by clearly depicting the abnormality. However, if the radiographs are definitely normal and the referring physician is convinced on the basis of the history and physical examination that a significant abnormality is present, then MRI examination should be performed. MRI can accurately confirm (Figures 3-17 and 3-18) or exclude the clinical diagnosis. This can be done immediately following injury in the face of a negative radiographic examination. This 29-year-old man fell on the outstretched hand, and the initial radiographic examination was normal. The T1 MRI demonstrates a contusion (arrow) of the radial head and neck (Figures 3-17A and B). Note also the hemarthrosis (asterisk). Alternatively MRI can be performed some time later following repeated normal radiographic examinations. This 40-year-old lady fell on the outstretched hand several weeks earlier and experienced continued pain and limitation of motion. The T1 MRI reveals a nondisplaced fracture (arrow) of the radial head (Figure 3-18). MRI may also identify “alternative diagnoses,” either a fracture or contusion of adjacent bones or soft tissue injuries such as tears of the collateral ligaments or injuries of the brachialis, biceps, or triceps tendons.

CHAPTER 4

The Wrist

Wrist Checklists

     

1. Radiographic examination Carpus PA PA with ulnar deviation Pronation oblique Lateral Distal forearm PA Pronation oblique Lateral

2. Common sites of injury in adults Distal radius and ulnar styloid Scaphoid Waist, distal tubercle, proximal pole Triquetrum Dorsal surface Hamate Dorsal and distal surface often in association with fourth and fifth MCC joint fracture-dislocation

3. Common sites of injury in children and adolescents Both bone fractures of distal forearm common Buckle (torus) fractures may be subtle. Distal radial epiphyseal separations, Salter-Harris types 1 and 2 Most common site of epiphyseal separations in entire skeleton Salter-Harris type 1 in younger children Salter-Harris type 2 most common in older children and adolescents Carpal fractures uncommon in young children.

4. Injuries likely to be missed Fine, nondisplaced fracture of scaphoid Waist, proximal pole, distal tubercle Subtle, nondisplaced fracture of distal radius Fracture-dislocation of fourth and fifth MCC joints

24

5. W  here else to look when you see something obvious Obvious

Look for

Fracture ulnar styloid

Subtle fracture distal radius Fracture dorsal surface Dislocation fourth and fifth hamate MCC Displaced fracture scaphoid Fracture capitate and/or ­triquetrum Perilunate dislocation Fracture distal shaft radius Galeazzi fracture dislocation, disrupt distal radial ulnar joint Dislocation distal radioulnar Comminuted fx radial head – joint (Essex-Lopresti fracture)

6. W  here to look when you see nothing at all Note pronator quadratus sign. Clue to underlying subtle distal radial fracture Look closely at scaphoid for fine fracture line. Waist, proximal pole, distal tubercle Check dorsal surface of triquetrum and hamate on lateral view. Observe integrity of fourth and fifth MCC joints. If questionable radiographic findings, get CT. If x-rays negative but clinical concern for significant injury, get MRI.

Wrist - the Primer 1. R  adiographic examination Carpus PA PA with ulnar deviation Pronation oblique Lateral Distal forearm PA Pronation oblique Lateral

     

The Wrist 

B

A

   25

D

C

FIGURE 4-1  Four views that have been proven to disclose the presence of the majority of fractures and dislocations of the wrist. A, PA. B, PA with ulnar deviation. C, Pronation oblique. D, Lateral.

Hamate

Triquetrum

A

B

PA

Oblique

C

Lateral

FIGURE 4-2  Diagrams of the wrist and distal forearm.

These four views (Figures 4-1A, PA, 4-1B, PA with ulnar deviation, 4-1C, pronation oblique, and 4-1D, lateral) are selected because they have been proven to disclose the presence of the majority of fractures and dislocations. Fractures of the waist of the scaphoid are notorious for being inapparent on the PA view (Figure 4-1A); however, the PA view with ulnar deviation (Figure 4-1B) will usually disclose these otherwise obscure fractures. Certain injuries can be inapparent on standard PA and lateral orthogonal projections but become evident on the pronation oblique view (Figure 4-1C). This is particularly true of subtle fracture dislocations of the fourth and fifth MCC joints, fractures of the distal tubercle of the scaphoid, and obscure, nondisplaced fractures of the distal radius.

2. Common sites of injury in adults Distal radius and ulnar styloid Scaphoid Waist, distal tubercle, proximal pole

Triquetrum Dorsal surface Hamate Dorsal and distal surface Commonly in association with dislocations of the fourth and fifth MCC joints Base of the fourth and fifth metacarpals, fractures or MCC fracture-dislocations Pattern of search.  Diagrams of the wrist and distal forearm

(Figure 4-2) pinpoint the common sites of fracture. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites. The fourth and fifth metacarpohamate joints should be examined closely to detect fractures of the base of the metacarpals or fracture dislocations of the MCC joints. The MCC joint spaces should be of normal width, similar to the second and third MCC joints, and the opposing cortical surfaces of the fourth and fifth MCC joints should be parallel.

26   

  The Wrist

B

A

FIGURE 4-3  Pronator quadratus muscle.

A

B

C

FIGURE 4-4  A and B, Pronator fascia plane seen on a lateral radiograph of the wrist as a linear lucent line extending proximally from the volar rim of the distal radial joint surface (small arrow). C, Bulging pronator fascial plane due to subtle, torus-like impacted fracture of the dorsal distal radial metaphysis (large arrow).

Pronator quadratus fascial plane.  The pronator quadratus

Fractures of the distal radius and ulna. Fractures of

muscle extends across the volar surface of the ulna to insert on the volar and ulnar surfaces of the distal radius (Figure 4-3A). The fascial surface of the muscle is outlined by a thin layer of fat that is visible on lateral radiographs of the wrist (Figure 4-3B). Changes in the appearance of the pronator fascia plane are clues to otherwise obscure underlying fractures of the distal radius. Normally this fascial plane is seen on a lateral radiograph of the wrist as a linear lucent line extending proximally from the volar rim of the distal radial joint surface (Figures 4-3B and 4-4A and B, small arrow). In the presence of a fracture of the distal radius, the fascial plane is bowed and displaced outward by hemorrhage and edema within the underlying pronator quadratus muscle. Note bulging pronator fascial plane due to subtle, torus-like impacted fracture of the dorsal distal radial metaphysis (Figure 4-4C).

the distal radius and ulna are 10 times more frequent than fractures of the carpal bones. The majority are either nondisplaced or Colles fractures with dorsal angulation of the distal fragment (Figures 4-4 to 4-6A and B). Colles fractures are ≈10 times more frequent than Smith fractures characterized by volar angulation of the distal fragment (Figures 4-5 and 4-6C and D). Care should be taken to differentiate between the two. Isolated fractures of the distal ulnar shaft, commonly located at the junction of the mid and distal thirds, are due to direct blows and often referred to as “nightstick” fractures (Figure 4-7). Displaced, angulated fractures of the distal radial shaft associated with dislocations of the distal radioulnar joint (DRUJ) are known as Galeazzi fractures (Figures 4-8A and B).

The Wrist 

   27

Volar Undisplaced

Smith Fx

Colles Fx

FIGURE 4-5  Fractures of the distal radius and ulna.

A

B

C

D

FIGURE 4-6  A and B, Colles fractures with dorsal angulation of the distal fragment. C and D, Colles fractures are ≈10 times more frequent than Smith fractures characterized by volar angulation of the distal fragment.

A FIGURE 4-7  Isolated fractures of the distal ulnar shaft, commonly located at the junction of the mid and distal thirds, are due to direct blows and often referred to as “nightstick” fractures.

B

FIGURE 4-8  A and B, Displaced, angulated fractures of the distal radial shaft associated with dislocations of the distal radioulnar joint (DRUJ) are known as Galeazzi fractures.

28   

  The Wrist

B

A

C

FIGURE 4-9  The waist of the scaphoid (A) is involved in 75% to 80% of carpal bone fractures, the distal tubercle and distal pole in 15% (B), and the proximal pole in 5% (C).

A

B

FIGURE 4-11  The principal carpal dislocations involve the lunate and are referred to as lunate and perilunate dislocations.

FIGURE 4-10  A, Fractures of the triquetrum are small avulsions from the dorsal cortex and are only apparent on the lateral view. B, Fractures of the hamate also involve the dorsal surface and are best seen on the lateral and oblique views of the wrist.

Carpal fractures.  The vast majority (≈75%) of carpal bone fractures involve the scaphoid (Figure 4-4) and another 15% to 20% the triquetrum. Therefore, together the scaphoid and triquetrum amount to 90% to 95% of all carpal fractures. Time is well spent on the analysis of these two bones in carpal trauma. The waist of the scaphoid (Figure 4-9A) is involved in 75% to 80%, the distal tubercle and distal pole in 15% (Figure 4-9B), and the proximal pole in 5% (Figure 4-9C). Fractures of the triquetrum are small avulsions from the dorsal cortex and are only apparent on the lateral view (Figure 4-10A). Fractures of the hamate also involve the dorsal surface and are best seen on the lateral (Figure 4-10B) and oblique views of the wrist. When displaced these hamate fractures are associated with dislocations of the fourth and fifth metacarpal-hamate joints as shown (Figure 4-10B). Carpal

dislocations. Carpal dislocations and fracturedislocations are relatively uncommon. The principal dislocations involve the lunate and are referred to as lunate and perilunate dislocations (Figure 4-11). Dislocations of the distal radioulnar joint are less common. Anterior dislocation of the lunate has two characteristic features; first, the lunate is triangular in outline on the PA

view with disruption of the radiolunate, capitolunate, scapholunate, and lunatotriquetral joints (Figure 4-12A). Second, the lunate is anteriorly (volarly) displaced on the lateral view (Figure 4-12B), looking very much like its namesake, a crescent moon. The majority (75% to 80%) of perilunate dislocations of the carpal bones are accompanied by a widely displaced fracture of the waist of the scaphoid. Observe the widely displaced fracture of the waist of the scaphoid with overlap of the distal and proximal poles of the scaphoid (Figure 4-12C). Isolated fractures of the scaphoid are essentially nondisplaced. Wide displacement of a scaphoid fracture indicates the probability of an associated perilunate dislocation or instability of the carpus due to other associated fractures of the waist of the capitate and triquetrum. Note the triangular shape of the lunate on the PA view (Figure 4-12C). Identify the lunate and capitate and their alignment with the radius on the lateral view (Figures 4-11 and 4-12D). Note the capitolunate joint is disrupted, and the capitate lies posterior to the lunate. The lunate is tilted volarly but not completely displaced from its articulation within the distal radius. These findings identify this case as a trans-scaphoid, posterior perilunate dislocation (see also Figure 4-24).

The Wrist 

B

A

C

   29

D

FIGURE 4-12  Anterior dislocation of the lunate has two characteristic features; first, the lunate is triangular in outline on the PA view with disruption of the radiolunate, capitolunate, scapholunate, and lunatotriquetral joints (A). Second, the lunate is anteriorly (volarly) displaced on the lateral view (B), looking very much like its namesake, a crescent moon. C, Widely displaced fracture of waist of scaphoid with overlap of the distal and proximal poles of the scaphoid. D, Identify the lunate and capitate and their alignment with the radius on the lateral view.

A dislocation of the distal radioulnar joint (DRUJ) is shown in association with a Galeazzi fracture-dislocation (see Figure 4-8A and B).

3. Common sites of injury in children and adolescents Both bone fractures of distal forearm common Buckle (torus) fractures may be subtle. Distal radial epiphyseal separation in older child and adolescents Carpal fractures uncommon in children Pattern of search.  PA and lateral diagrams of the wrist and

distal forearm pinpoint the common sites of fracture (Figures 4-13A and B). The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites. Fractures of the distal radius and ulna.  Complete (Figure

4-14) and greenstick fractures of the distal radius and ulna are common and usually readily recognized on radiographs. Normally there is a gentle flaring of the distal metaphysis of both bones that is similar to the bell or distal part of a clarinet (Figure 4-15). Torus or buckle forms of greenstick fracture

can be subtle and are easily overlooked. Any distortion of the gentle flaring of the metaphysis or buckling of the cortex is indicative of a torus fracture (Figure 4-16). This can be seen on the medial and lateral cortex in the PA projection (Figure 4-16A) but is better seen in the posterior cortex on the lateral view (Figure 4-16B). Carpal bone fractures.  Carpal bone fractures are distinctly

uncommon in children prior to the age of 14. When scaphoid fractures occur they are often transverse in the distal pole of the scaphoid (Figure 4-17A) and not in the waist as found in older individuals. Fractures of the distal tubercle are also encountered (Figure 4-17B). Separations of the distal radial epiphysis.  Separations of the

distal radial epiphysis are the most common of all epiphyseal injuries (Figure 4-18). They occur between the ages of 11 and 15 years and are virtually always Salter-Harris type 2 injuries. The injury may be difficult to see on the PA view when the physis is only slightly widened and there is little offset of the epiphysis (Figure 4-18A). However, the injury is usually easily recognized on the lateral view (Figure 4-18B) by posterior displacement of the epiphysis accompanied by a triangularshaped metaphyseal fragment often referred to as the “corner sign.” Distal radial epiphyseal separations in younger children

30   

  The Wrist

Epiphyseal separation Corner sign

Torus fracture

FIGURE 4-13  PA and lateral diagrams of the wrist and distal forearm pinpoint the common sites of fracture in children. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines.

Torus fracture

Complete fracture

Complete fracture

A

B

A

FIGURE 4-14  Complete fractures of the distal radius and ulna are common in children and usually readily recognized on radiographs.

B

FIGURE 4-16  Any distortion of the gentle flaring of the metaphysis or buckling of the cortex is indicative of a torus fracture. A, PA projection. B, Lateral view.

are often Salter-Harris type 1 (Figures 4-18C and D) injuries with posterior displacement of the epiphysis but without a metaphyseal component (Figure 4-18D). Comparison with the normal opposite side (Figure 4-18E) may be necessary to confirm displacement of the injured epiphysis.

4. Injuries likely to be missed Fine, undisplaced fracture of scaphoid Waist, proximal pole, distal tubercle Fracture-dislocation of fourth and fifth MCC joints Scaphoid fractures.  Fractures of the scaphoid are the most

FIGURE 4-15  Normally in fractures of the distal radius and ulna there is a gentle flaring of the distal metaphysis of both bones that is similar to the bell or distal part of a clarinet.

commonly missed fractures of the carpus. Most scaphoid fractures are undisplaced and appear as a fine, narrow lucent line. If only the PA and lateral views are obtained, such fractures are easily overlooked. Fractures of the waist of the scaphoid can be inapparent on the PA view (Figure 4-19A)

A

FIGURE 4-17  A, When scaphoid fractures occur in children, they are often transverse in the distal pole of the scaphoid and not in the waist as found in older individuals. B, Fractures of the distal tubercle are also encountered.

B

A

B

D

C

E

FIGURE 4-18  Separations of the distal radial epiphysis are the most common of all epiphyseal injuries in children. A, The injury may be difficult to see on the PA view when the physis is only slightly widened and there is little offset of the epiphysis. B, The injury is usually easily recognized on the lateral view by posterior displacement of the epiphysis accompanied by a triangular-shaped metaphyseal fragment often referred to as the “corner sign.” C, Distal radial epiphyseal separations in younger children are often Salter-Harris type 1 injuries with posterior displacement of the epiphysis but without a metaphyseal component (D). E, The normal opposite side.

A

B

FIGURE 4-19  Fractures of the waist of the scaphoid can be inapparent on the PA view (A) but become apparent on the PA view with ulnar deviation, the so-called “scaphoid view” (B).

32   

  The Wrist

FIGURE 4-20  Fractures of the distal tubercle of the scaphoid may also be obscure or invisible on the PA view (A) and seen for certain only on the pronation oblique view (B).

B

A

A

B

FIGURE 4-22  Fracture-dislocation of fourth and fifth MCC joints. A, PA view. B, Oblique view.

FIGURE 4-21  PA view of the normal anatomy of the fourth and fifth MCC joints.

of the injury is best seen in the oblique view (Figure 4-22B), which clearly demonstrates a coronal, longitudinal fracture of the hamate and dislocations of the fourth and fifth MCC joints.

5. Where else to look when you see something obvious

but become apparent on the PA view with ulnar deviation, the so-called “scaphoid view” (Figure 4-19B). Fractures of the distal tubercle of the scaphoid may also be obscure or invisible on the PA view (Figure 4-20A) and only seen for certain on the pronation oblique view (Figure 4-20B).

Obvious

Look for

Fx ulnar styloid Fx dorsal surface hamate

Fracture-dislocations of the fourth and fifth MCC joints. Fracture-dislocations of the fourth and fifth MCC

Displaced fx scaphoid

Subtle fx distal radius Dislocation fourth and fifth MCC joints Fx capitate and/or triquetrum Perilunate dislocation Perilunate dislocation with fracture of scaphoid

joints are probably overlooked primarily because the observer fails to look closely at this area for evidence of injury. Fractures of the distal, dorsal surface of the hamate are a harbinger, a sign, of such injuries. Learn the normal anatomy of this part of the hand and wrist on the PA view (Figure 4-21). The fourth and fifth MCC joint spaces should be of normal width (1 to 2 mm) and equal to that of the adjacent MCC joints. The opposing articular surfaces of the metacarpals and hamate should be parallel. The lateral cortex of the base of the fifth MCC should be aligned with the lateral cortex of the hamate. Compare with the appearance found in a fracture-dislocation of fourth and fifth MCC joints (Figures 4-22A and B). Note the fracture of the base of the fourth metacarpal and the loss of the normal fourth and fifth MCC joint spaces due to displacement and overlap of the bases of the metacarpals and the hamate. The true nature

Foreshortened carpus

The obvious injury of these pairings is usually observed, but the associated injury is often more subtle and may be easily overlooked. Or the association may be unknown to the observer and not sought. Or, more likely, having found an injury, the observer may be satisfied and quit searching, a victim of the so-called “satisfaction of search” phenomenon. This list reminds you that once you see the obvious injury look for the often-associated, usually less-obvious, second injury. Case 1. For example, note the obvious fracture of the ulnar styloid (Figure 4-23A). Fractures of the ulnar styloid rarely occur in isolation but are commonly found in association with

The Wrist 

obvious Colles or other fractures of the distal radius. There is no obvious fracture of the distal radius. But before you quit on this case check the status of the pronator quadratus fascia plane for a clue to an underlying fracture of the distal radius (Figure 4-23B). The pronator quadratus fascial plane is displaced and bowed outward, a positive pronator quadratus sign. Now look more closely at the distal radius on the PA view (Figure 4-23A). There you find a check-shaped linear lucency indicative of an incomplete fracture of the radius. If you were not careful, you could have blown right by it. Case 2. Note foreshortening of the carpus due to overlap of distal and proximal carpal rows (Figure 4-24A). Foreshortening of the carpus and crowding of the carpal bones with overlap of the proximal and distal rows may initially be alarming and confusing. This is usually due to a perilunate dislocation, the majority of which are associated with a displaced fracture of the waist of the scaphoid. Observe the widely displaced fracture of the waist of the scaphoid with overlap of the distal and proximal poles of the scaphoid. Wide displacement of a scaphoid fracture indicates the probability of an associated perilunate dislocation or instability of the carpus due to other associated fractures of the waist of the capitate and triquetrum. Note that the capitolunate joint is disrupted and the capitate lies posterior to the lunate (Figure 4-24B), indicating the diagnosis of a transscaphoid, posterior perilunate dislocation.

A

B

FIGURE 4-23  A, Obvious fracture of the ulnar styloid. B, Underlying fracture of distal radius.

A

   33

6. Where to look when you see nothing at all Note pronator quadratus sign. Clue to underlying subtle distal radial fracture Look closely at scaphoid for fine fracture line. Waist, proximal pole, distal tubercle Check dorsal surface of triquetrum and hamate on Lateral view Observe integrity of fourth and fifth MCC joints.

The emergency physician calls and says he is really concerned about an injury in Miss Jones’s wrist, but you had not seen anything at all when you viewed the radiographs. What now? Ask specifically where Miss Jones hurts. Look there on the films. Look again. Do you have all the standard views? Look specifically at the areas as outlined above. You have PACs. Magnify the areas in question. Reverse the image and use the edge enhancement sequences. If all are negative you may have to repeat the examination in 7 to 10 days, but if there is sufficient clinical concern you should consider CT or MRI depending on the circumstances. If there are radiographic findings present, no matter how subtle, a CT examination with image reconstruction in the coronal and sagittal planes will likely resolve the ambiguities by clearly depicting the abnormality. However, if the radiographs are definitely normal and the referring physician is convinced on the basis of the history and physical examination that a significant abnormality is present, an MRI examination should be performed (Figures 4-25 and 4-26). MRI can accurately confirm (Figure 4-25) or exclude the clinical diagnosis or identify an “alternative diagnosis,” either a fracture (Figure 4-26) or contusion of adjacent bones or soft tissue injuries such as tears of the triangular fibrocartilage (TFCC) or radiocarpal or intercarpal ligaments. When MRI is performed for a suspected scaphoid fracture the clinical diagnosis is confirmed in 20%, alternative diagnoses (fractures of other bones or ligamentous injuries) are found in 30%, and significant injuries are excluded in the remaining 50%. Confirmation of the clinical diagnosis of scaphoid injury is achieved in the case shown in Figure 4-25. The PA radiograph of the carpus shows no definite fracture of the scaphoid (Figure 4-25A). However, the TI coronal (Figure 4-25B) and coronal STIR (Figure 4-25C) MRI reveal a contusion of the waist of the scaphoid.

B

FIGURE 4-24  A, Foreshortening of the carpus due to overlap of distal and proximal carpal rows. B, The capitolunate joint is disrupted, and the capitate lies posterior to the lunate, indicating the diagnosis of a trans-scaphoid, posterior perilunate dislocation.

34   

  The Wrist

B

A

C

FIGURE 4-25  A, PA radiograph of the carpus shows no definite fracture of the scaphoid. However, the TI coronal MRI (B) and coronal STIR MRI (C) reveal a contusion of the waist of the scaphoid.

A

B

FIGURE 4-26  T1 weighted coronal MRI (A) and T2 fat sat axial (B) MRI demonstrate a nondisplaced fracture of the distal radius (arrows).

An alternative diagnosis was obtained by MRI in the case shown in Figure 4-26. This young man was strongly suspected clinically of having a scaphoid fracture, but the initial radiographs were negative. Three weeks post-injury an MRI was obtained. T1 weighted coronal (Figure 4-26A) and T-2 fat sat

axial (Figure 4-26B) demonstrate a nondisplaced fracture of the distal radius (arrows). The scaphoid was normal. Fractures of the distal radius are the single most common fracture identified by MRI under these circumstances.

CHAPTER 5

The Hand Hand Checklists 1. Radiographic examination PA Pronation oblique Lateral

2. Common sites of injury in adults Fractures Phalanges (55% of hand injuries) Distal (50+% of fractures of the phalanx) Ungual tuft, base, shaft, baseball finger avulsion Proximal (15% of fractures of the phalanx) Shaft, base, condyles, volar plate avulsion Middle (10+% of fractures of the phalanx) Shaft, base, condyles, volar plate avulsion Metacarpals (36% of hand injuries) Shaft, base, head, neck (boxer’s fracture of fourth and fifth MCs) Thumb Base of metacarpal Intraarticular – Bennett’s, Rolando’s Extraarticular – transverse, oblique Distal phalanx Ungual tuft, base, shaft Dislocations Interphalangeal joints (DIP and PIP) Metacarpophalangeal joints Carpometacarpal joints Fourth and fifth CMC fracture dislocation most common

3. Common sites of injury in children and adolescents 50% involve the proximal phalanx. Majority of fractures of the phalanges and metacarpals



a. involve the epiphysis b. Salter-Harris type 2, most common

5. W  here else to look when you see something obvious

     

Fractures of adjacent metacarpals and phalanges Fractures base of fourth and fifth MCs – dislocation of adjacent MCC joint

6. W  here to look when you see nothing at all Start over again – review the radiographs. Consider CT for questionable radiographic findings MRI if radiographs are unrevealing

Hand – The Primer

     

1. R  adiographic examination PA Pronation oblique Lateral   

The standard radiographic examination of the traumatized hand should include the three standard views: PA (Figure 5-1A), pronation oblique (Figure 5-1B), and lateral (Figure 5-1C). Many fractures are more apparent and better visualized on the oblique projection. Fractures may be missed if the examination is limited to only the PA and lateral projections. For the lateral view (Figure 5-1C) the fingers should be “fanned” to allow clear visualization of each finger without overlap of the digits. When the injury is confined to a single digit, a phalanx, greater detail and a sharper image are obtained by limiting the exposure to the digit in question as shown in Figure 5-2 of left index finger: PA view, (Figure 5-2A), oblique view (Figure 5-2B), and lateral view (Figure 5-2C). This is particularly useful in identifying volar plate avulsions and other fine nondisplaced fractures that can be quite subtle and can be overlooked on radiographs of the entire hand. The same may be said of the thumb as shown in Figure 5-3 of the right thumb: PA view (Figure 5-3A), oblique view (Figure 5-3B), and lateral view (Figure 5-3C).

High percentage best seen on the oblique view.

4. Injuries likely to be missed Fracture-dislocations of the fourth and fifth carpometacarpal (CMC) joints Fractures of the condyles of the phalanges

2. C  ommon sites of injury in adults Fractures Phalanges (55% of hand injuries) Distal (50+% of fractures of the phalanx) Ungual tuft, base, shaft, baseball finger avulsion

35

36   

  The Hand

A

B

C

FIGURE 5-1  Three standard views of the standard radiographic examination of the traumatized hand: A, PA, B, pronation oblique, and C, lateral.

FIGURE 5-2  Left index finger: A, PA view, B, oblique view, and C, lateral view.

Proximal (15% of fractures of the phalanx) Shaft, base, condyles, volar plate avulsion Middle (10+% of fractures of the phalanx) Shaft, base, condyles, volar plate avulsion Metacarpals (36% of hand injuries) Shaft, base, head, neck (boxer’s fracture of fourth and fifth MCs) Thumb Base of metacarpal Intraarticular – Bennett’s, Rolando’s Extraarticular – transverse, oblique Distal phalanx Ungual tuft, base, shaft

A

B

C

Dislocations Interphalangeal joints (DIP and PIP) Metacarpophalangeal joints Carpometacarpal joints Fourth and fifth CMC fracture dislocation most common Pattern of search.  Diagrams of the hand pinpoint the common

sites of fracture and dislocation in adults (Figures 5-4A, PA view, and 5-4B, lateral view). The most common sites are identified by thicker red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites.

The Hand 

A

C

B

FIGURE 5-3  Right thumb: A, PA view, B, oblique view, and C, lateral view.

A

B

FIGURE 5-4  Common sites of fracture and dislocation in adults: A, PA view and B, lateral view.

A

B

C

   37

Fractures of the hand are undoubtedly the most common sites of fracture in the entire skeleton. Fractures of the phalanges account for over 55%, most frequently involving the distal phalanx. Slightly fewer than 40% of fractures involve the metacarpals, most commonly the fifth metacarpal followed by the thumb metacarpal. Soft tissue swelling serves as a clue to fractures of the phalanges. When encountered look closely at the underlying bone and joints for subtle injuries (Figure 5-5A, PA view, note swelling about PIP joint and head of proximal phalanx; Figure 5-5B, lateral view, note avulsion of volar surface of epiphysis of middle phalanx better seen on Figure 5-5C). Fractures of the ungual tuft (Figure 5-6A) are one of the most common fractures in the hand and are best seen when examination is limited to the digit in question. They are easily overlooked on radiographs of the hand either because the distal tips of the fingers are overexposed or in the absence of clinical information directing attention to them. Always look specifically at the ungual tufts for evidence of fracture. Longitudinal fractures may occur (Figure 5-6B). A fine, nondisplaced, intraarticular Y-shaped fracture of the base of the distal phalanx is shown in Figure 5-6C. Small avulsions occur from volar surface of the base of the middle phalanx (Figure 5-7A) and, less commonly, of the distal phalanx. These are due to hyperextension injuries and represent avulsions at the attachment of the volar plate and are therefore referred to as volar plate avulsions. Avulsion fractures also occur from the dorsal surface of the base of the terminal phalanx (Figure 5-7B) often associated with a flexion deformity of the DIP. The fracture is created by pull of the extensor tendon that inserts on the dorsal surface of the base of the terminal phalanx. These usually occur in ballplayers when the ball hits the end of the finger and are therefore known as baseball fingers. The injury is also referred to as a mallet finger because flexion deformities of the DIP suggest the appearance of a hammer. Fractures of the shafts of the phalanges may be transverse or oblique (Figure 5-8A). Fractures of the base of the proximal phalanx are characteristically sharply angulated dorsally (Figure 5-8B). Fractures of the condyle (Figure 5-8C) require open reduction and pin or screw fixation. Pathologic fractures occurring in the phalanges virtually all involve benign enchondromas (Figure 5-8D). Boxer’s fractures occur at the neck of the fourth and fifth MCs (Figure 5-9A). These are the result of a blow struck by the fist. The distal fragment is usually in volar angulation. Oblique fractures occur in the midshaft (Figure 5-9B) and may be obscure when nondisplaced. Transverse fractures are

FIGURE 5-5  Look closely at underlying bone and joints for subtle soft tissue swelling: A, PA view, note swelling about PIP joint and head of proximal phalanx; B, lateral view, note avulsion of volar surface of epiphysis of middle phalanx better seen in (C).

38   

  The Hand

A

C

B

FIGURE 5-6  A, Fractures of the ungual tuft. B, Longitudinal fractures. C, A fine, non-displaced, intraarticular Y-shaped fracture of the base of the distal phalanx.

common (Figures 5-9C and 5-9D). Fractures of the base of the metacarpals, particularly the fourth and fifth metacarpals) are often accompanied by dislocation of the adjacent carpometacarpal joint (Figure 5-9E). Fractures of the thumb. Fractures of the thumb most frequently involve either the terminal phalanx or the base of the thumb. Terminal phalanx fractures are similar to those of the other phalanges. Fractures of the base of the metacarpal (Figure 5-10A) are either intraarticular Bennett’s fracture dislocations (Figure 5-10B), comminuted Rolando’s fractures, or extraarticular transverse (Figure 5-10C) or oblique fractures that spare the carpometacarpal joint. Dislocations of the phalanges.  Dislocations are common in

A

B

FIGURE 5-7  Small avulsions occur from volar surface of the base of the middle phalanx (A) and, less commonly, from the distal phalanx. Avulsion fractures also occur from the dorsal surface of the base of the terminal phalanx (B) often associated with a flexion deformity of the DIP.

FIGURE 5-8  A, Fractures of the shafts of the phalanges may be transverse or oblique. B, Fractures of the base of the proximal phalanx are characteristically sharply angulated dorsally. Fractures of the condyle (C) require open reduction and pin or screw fixation. D, Pathologic fractures occurring in the phalanges virtually all involve benign enchondromas.

A

both the PIP (Figure 5-11A), DIP, and MCP (Figure 5-11B) joints and are frequently accompanied by fractures of the base of the displaced phalanx. Carpometacarpal dislocations are less common but may be subtle, difficult to identify, and easily overlooked, particularly those involving the fourth and fifth MCs (Figures 5-11C and 5-11D). To avoid oversights, be certain to look specifically for evidence of fourth and fifth CMC fracture dislocations in every case. Note fracture of the

B

C

D

The Hand 

A

B

Bennet’s

C

Rolando’s

D

Transverse

Intra-articular

Oblique

E

   39

FIGURE 5-9  Boxer’s fractures occur at the neck of the fourth and fifth MCs (A). Oblique fractures occur in the midshaft (B) and may be obscure when nondisplaced. C, D, Transverse fractures of fourth MC best seen on oblique. Fractures of the base of the metacarpals are often accompanied by dislocation of the adjacent carpometacarpal joint (E).

Epiphyseal separation (Salter-Harris Type 2)

Extra-articular

A

B

A

FIGURE 5-10  Fractures of the thumb: A, Fractures of the base of the metacarpal; B, Intraarticular Bennett’s fracture dislocations; C, Transverse fractures.

C

B

C

D

FIGURE 5-11  Dislocations of the phalanges: A, PIP joint dislocation; B, MCP joint dislocation; carpometacarpal dislocations are less common but can be easily overlooked, particularly those involving the fourth and fifth MCs (C and D).

40   

  The Hand

base of the fourth MC and obliteration of the fifth MCC joint space due to dislocation of the fifth MCC joint (Figure 5-11C). Note malalignment of MCs and small avulsion fracture from the dorsal surface of the distal hamate on the lateral view (Figure 5-11D).

3. Common sites of injury in children and adolescents 50% involve the proximal phalanx. Majority of fractures of the phalanges and metacarpals



a. involve the epiphysis b. Salter-Harris type 2, most common

High percentage best seen on the oblique view. Pattern of search. Diagram of child’s hand (Figure 5-12)

pinpoints the common sites of fracture in children. The most common sites of fracture are identified by thicker red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites.

Fractures of the ungual tuft and shafts of the phalanges and metacarpals are similar to those in adults as illustrated above. Dislocations of the interphalangeal and metacarpophalangeal joints are less common than in adults. Epiphyseal injuries account for approximately 40% of fractures in children. The overwhelming majority are SalterHarris type 2 (Figure 5-13A, proximal phalanx of little finger; Figure 5-13B, proximal phalanx of the thumb; Figure 5-13C, distal phalanx of middle finger), while a small number, particularly in younger children, are type 1. Torus, buckle-type, fractures are common in the metaphysis adjacent to the physis (Figure 5-13D, buckle-type fracture of distal phalanx of thumb). With greater forces at play, these may have resulted in frank Salter-Harris type 2 epiphyseal separations. Volar plate avulsions are quite common in children. The volar plate is attached to the rim of the epiphysis. Avulsions occur in the presence of an open epiphysis as shown in Figure 5-14. Note soft tissue swelling about PIP joint of little finger (Figure 5-14A, PA view). A cropped lateral view of the PIP joint of little finger (Figure 5-14B) reveals an avulsion of the volar rim of the epiphysis of the middle phalanx. The body of the epiphysis remains nondisplaced, and the physis is intact.

4. Injuries likely to be missed Fracture-dislocations of the fourth and fifth carpometacarpal (CMC) joints Fractures of the condyles of the phalanges   

Carpometacarpal fracture-dislocations are easily overlooked because the findings are subtle; they don’t jump out at you. This is further complicated by the fact that you may not make it a point to look specifically at this area on the radiographs. Be aware of the normal anatomy on the PA view (Figure 5-15A). Always look at this area for evidence of injury. Note the even joint space with parallel joint margins of the MC fourth and fifth hamate joints. Further, note the lack of any overlap between the base of the metacarpals and the hamate. Nonparallel joint surfaces or overlap of the base of the metacarpals and hamate are indicative of a fracture-dislocation of these joints (Figure 5-15B). Then look on the oblique and lateral view (Figure 5-15C) for dislocation of the base of the metacarpals and a fracture of the FIGURE 5-12  Common sites of fractures in children.

A

B

C

D

FIGURE 5-13  Salter-Harris type 2 epiphyseal injuries: A, Proximal phalanx of little finger; B, Proximal phalanx of the thumb; C, Distal phalanx of middle finger; D, Buckle-type fracture of distal phalanx of thumb.

The Hand 

A

   41

B

FIGURE 5-14  Volar plate avulsion in the presence of an open epiphysis: A, Soft tissue swelling about PIP joint of little finger, PA view; B, Cropped lateral view of the PIP joint of little finger.

A

B

C

FIGURE 5-15  Carpometacarpal fracture-dislocations: A, PA view; B, Nonparallel joint surfaces or overlap of the base of the metacarpals and hamate indicative of a fracture-dislocation of these joints; C, Lateral view, note avulsion fracture of hamate and dislocation of fourth and fifth metacarpals.

dorsal and distal surface of the hamate, verifying the presence of a fourth and/or fifth CMC fracture-dislocation. You are presented with a PA and lateral view of a digit and asked to “rule out fracture.” PA and lateral views­ (Figures 5-16A and 5-16B) are insufficient for the exclusion of fractures of the phalanges and metacarpals. Oblique views are required for a proper and complete examination of the hand and digits. Obtain an oblique view (Figure 5-16C). Certain injuries may be best seen or even only seen on the oblique projection. This is particularly true of fractures of the condyles of the phalanges as in the case shown. Note loss of small segment of articular surface (arrow) on the PA view (Figure 5-16A). The lateral view (Figure 5-16B) shows no abnormality. The oblique view (Figure 5-16C) reveals a fracture of the condyle of the proximal phalanx of the middle finger (arrow).

Having identified a fracture of a metacarpal or phalanx, be certain to look at adjacent metacarpals and phalanges for additional fractures. Fractures of the second through fifth metacarpals and phalanges, especially the proximal phalanges, are often multiple and involve adjacent bones with similar fractures. Usually two adjacent bones are affected (Figure 5-17A, fractures of the fourth and fifth MCs). Note obvious fracture of the neck and head of the fifth MC. Close evaluation shows similar, lesser fracture of the fourth MC). Less frequently, there are three adjacent fractures (Figure 5-17B). One fracture is frequently readily apparent (a Salter-Harris type 2 epiphyseal injury of the third proximal phalanx), while those involving the adjacent bones on either side (second and fourth proximal phalanges) are less so and may be easily overlooked. So when a fracture of a metacarpal or proximal phalanx is identified, look closely at the adjacent bones for a similar injury.

5. Where else to look when you see something obvious

6. W  here to look when you see nothing at all

Fracture of phalanx or metacarpal Fractures of adjacent phalanges and metacarpals Fractures base of fourth and fifth MCs Dislocation of adjacent MCC joint

Start over again – review the radiographs. Consider CT for questionable radiographic findings MRI if radiographs are unrevealing

  

  

42   

  The Hand

A

B

C

FIGURE 5-16  Carpometacarpal fracture-dislocations: A, B, PA and lateral views; C, Oblique view.

A

B

FIGURE 5-17  A, Fractures of the fourth and fifth MCs. B, Three adjacent fractures.

FIGURE 5-18  T1-weighted coronal image of the thumb metacarpal.

Dr. Newcomer, a family physician, calls to say that she remains concerned about an injury to Mrs. Ortega’s hand, but you hadn’t seen anything at all when you viewed the initial radiographs 10 days ago. What now? First, ask exactly where Mrs. Ortega hurts and what findings are present on the physical examination of her thumb. Dr. Newcomer says Mrs. Ortega hurt her thumb and was tender to palpation over the metacarpophalangeal joint, more so on the lateral (radial) side than medially. Medial pain would suggest the possibility of a gamekeeper’s thumb. Then review her radiographs. The radiographs once again prove to be negative. An MRI was suggested for further evaluation (Figure 5-18). This T1-weighted coronal image of the thumb metacarpal demonstrates that the ulnar collateral ligament is intact. However, the radial collateral ligament is shown to be obviously detached from its insertion on the head of the metacarpal. The MRI clearly depicts an avulsion of the radial collateral ligament of the first MCP joint. In general, if you see no findings on the radiographs and the clinician remains convinced that a significant injury has occurred, obtain an MRI. If there are questionable radiographic findings, they would most likely be clarified and resolved by a CT examination.

CHAPTER 6

The Cervical Spine Cervical Spine Checklists

     

1. Radiographic examination Minimum necessary views Lateral cervical spine to include T1 AP cervical spine AP open-mouth odontoid CT examination: minimum necessary Axial, sagittal, and coronal noncontrast images in bone algorithm Extending through at least the level of T1 Axial and sagittal images in soft tissue algorithm

2. Common sites of injury in adults Craniocervical junction (Skull base – C2) Fractures Occipital condyle Atlas – C1 Posterior arch Jefferson fracture – fractures of ring anterior and posterior Anterior arch Axis – C2 Odontoid (dens) Body Extension of dens fracture Teardrop fracture C2 pars interarticularis fractures – hangman’s fracture Dislocations/subluxation Atlanto-occipital dissociation Atlanto-axial dislocation Lower cervical spine (C3-C7) Fractures Vertebral bodies Compression, distraction, and translation/rotation injuries (SLIC) Simple compression, anterior wedge Teardrop Vertical sagittal split of vertebral body Burst Lateral mass Facets Articular mass Transverse process Spinous process Traumatic disc injuries Dislocations/subluxations Teardrop fracture dislocation

Distraction – ligament disruption Intervertebral disc, joint capsules, and interspinous ligament Anterior and posterior longitudinal ligaments Facets – unilateral or bilateral – rotation, shearing injuries Subluxed Perched Dislocated

3. Special considerations in the elderly Odontoid fractures common Often combined with C1 arch fractures Spinal cord injury in presence of significant degenerative arthritis and disc disease Often with either subtle or even without overt radiographic abnormality (SCIWORA) Hyperextension teardrop Fracture of inferior or superior anterior margins of vertebral body Fracture of osteophyte at superior or inferior anterior margin of vertebral body Fractures in DISH (diffuse idiopathic skeletal hyperostosis)

4. Common sites of injury in children and adolescents Cervical spine injury (CSI) rare in children under 8 years of age Relatively more involve upper cervical spine Craniocervical dissociation C1 fractures Dens fractures uncommon in children Rare – apophyseal separations of synchondrosis between dens and body of C2 Spinal cord injury without radiographic abnormality (SCIWORA) At and beyond 14 years of age injuries similar to those of adults Relatively more involve lower cervical spine, C4-C7 Vertebral body Compression fracture Teardrop fracture dislocation

5. Injuries likely to be missed Subtle fractures on radiography – need CT Nondisplaced odontoid fractures Facet fractures Occipital condyle fractures

43

44   

  The Cervical Spine

6. Where else to look when you see something obvious Avoid “satisfaction of search.” Find an injury at one level: closely evaluate the entire cervical spine above and below. Multilevel discontiguous spine fractures Fractures of C1 and C2 often associated with fractures of the lower cervical spine (C4-C7) Two- or three-level fractures encountered in 20% of spinal fractures CT entire T and L spine after identifying fracture of C-spine Find a compression fracture: look for associated posterior element injury. Find a vertebral body injury: look for bony compromise of spinal canal. Find a facet malalignment on one side: look for contralateral facet malalignment/fracture.

7. Where to look when you see nothing at all Obtain an MRI for those with neurologic signs and symptoms. Spinal cord contusion Herniated nucleus pulposus (HNP) Spinal cord injury without radiographic abnormality (SCIWORA) Check width of spinal canal for spinal stenosis. Spondylosis and degenerative changes in elderly Check for evidence of hyperextension injury. Teardrop fractures at anterior margins of vertebral bodies Anterior widening of disc space Prevertebral soft tissue swelling Review images. Spinolaminar line Interspinous distances Closely evaluate prevertebral soft tissues for swelling. Look for subtle fractures. Facets Transverse processes Spinous processes

A

B

Cervical Spine – The Primer

     

Preamble: Imaging Spinal Trauma Though traditional and long the mainstay of cervical spine evaluation, radiographs of the cervical spine now have a limited role in the initial assessment of cervical spine trauma. Computed tomography (CT) was first introduced in the 1970s but did not prove adequate for the evaluation of the acutely injured spine until the early 2000s with the introduction and perfection of multidetector CT (MDCT), with rapid exposures coupled with the development of immediate and readily accomplished multiplanar image reconstructions. This permitted coronal and sagittal reconstructions of the entire length of the cervical spine in addition to the standard axial images. With these advances it became apparent that MDCT is more accurate and more efficient in the detection and depiction of spinal injuries. The comparative difficulty of detection by radiography is shown by a fracture of the dens that is hard to see, if not impossible to identify, on the lateral cervical spine radiograph (Figure 6-1A) but is clearly shown by the MDCT sagittal reconstruction (Figure 6-1B). The associated fracture of the posterior arch of C1 is seen by both examinations (Figure 6-1A, C). It has been shown that up to 20% or more of cervical fractures disclosed by MDCT are unapparent, overlooked, or simply missed on plain film radiographs of the cervical spine. Thus, the American College of Radiology Appropriateness Criteria: Suspected Cervical Spine Injury states that MDCT, not radiography, is now the primary, preferred, and most appropriate method of imaging suspected cervical spine injury in patients older than 14 years. Guidelines for imaging potential cervical spine injury (CSI).  There has long been professional and public concern

about the overuse of radiography and computed tomography (CT) and the resultant excessive radiation exposure in patients with CSI. Two separate clinical guidelines that allow for triage of patients with suspected CSI have gained general approval: the NEXUS (National Emergency X-Radiography Utilization Study) criteria and the Canadian Cervical Spine Rule (CCR). Though written to address the indications for radiography in cervical spine trauma, they are equally applicable for computed tomography. Both the NEXUS and Canadian Cervical Spine

C

FIGURE 6-1  A, Lateral cervical spine radiograph showing associated fracture of the posterior arch of C1. B, Fracture of the dens shown by MDCT sagittal reconstruction. C, Associated fracture of the posterior arch of C1.

The Cervical Spine 

Rule are recognized as valid by the American College of Radiology Appropriateness Criteria: Suspected Cervical Spine Injury. Use of one of these clinical decision rules is recommended to avoid excessive use of cervical spine imaging. The rules are different for pediatric patients. In patients under age 14, radiography remains the examination of choice and is recommended by the ACR Appropriateness Criteria. This is done for two primary reasons: There is a relatively low incidence of CSI under the age of 14 and a strong desire to limit the radiation exposure dose from CT in younger individuals. However, cervical spine MDCT (multidetector CT) remains as the initial diagnostic modality for all patients age 14 and older because the incidence of CSI approaches that of adults. NEXUS.  The NEXUS criteria allow the physician to forego

imaging entirely when certain criteria are met. The patient does not require imaging if there is   

No midline cervical tenderness No neurologic deficit No distracting injury Normal level of awareness (Glasgow Coma Scale [GCS] = 15) No intoxication Canadian Cervical Spine Rule.  The Canadian Cervical Spine

Rule is for alert and stable patients where cervical spine injury is a concern based on consideration of injury mechanism, patient age, and physical examination findings.   

Prerequisites for this assessment Concern for cervical spine injury Patient alert (GCS = 15) Patient in stable condition High-risk factor that mandates radiography Age ≥65yrs Dangerous mechanism of injury Fall from elevation ≥3 ft/5 stairs Axial load to head (i.e., diving) MVC high speed (>60 mph, 100 km/h), rollover, ejection Motorized recreational vehicle Bicycle crash Paresthesias in extremity Inability to actively rotate neck 45° to the right or left

A

B

   45

Low-risk factors that allows safe assessment of range of motion Simple rear-end MVC, but not to include Rollover Being pushed into oncoming traffic Being hit by bus, large truck, or high-speed vehicle Sitting position in the ED Ambulatory at any time Absence of midline cervical spine tenderness   

Although CT is recommended as the primary means of imaging for the evaluation of cervical spine trauma, radiographic examinations are still ordered and obtained for that purpose. These patients usually have sustained lesser trauma and have no specific signs of cervical spine injury, thus, not qualifying for imaging under the NEXUS or Canadian Cervical Spine Rule guidelines. Such patients may not have sought care until several days after the injury but now do so because of continued and/or increasing pain in the neck and limitation of motion. The NEXUS criteria and Canadian Cervical Spine Rule notwithstanding, the examining physician feels compelled to obtain a radiographic examination of the cervical spine to dispel the patient’s anxiety, meet the “patient’s expectations” of proper care under the circumstances, as well as to demonstrate the physician’s concern for the patient and mollify potential liability concerns. The vast majority of such examinations obtained under these circumstances will show nothing more than straightening of the cervical spine due to muscle spasm without fractures or dislocations. These should be reported as “No evidence of fracture or dislocation” with the added comment, “If pain persists, a repeat examination should be obtained in 7 to 10 days. If pain is severe, consider CT examination to disclose occult fracture.”

1. R  adiographic examination Minimum necessary views Lateral cervical spine to include T1 AP cervical spine AP open-mouth odontoid   

The radiographic examination of the cervical spine should include a minimum of three views: lateral (Figure 6-2A), AP

C

FIGURE 6-2  A, Lateral view, radiographic examination of the cervical spine. Best visualizes fractures and dislocations. B, AP view, radiographic examination of the cervical spine. Rotational injuries and fractures of the lateral masses may be evident. C, AP open mouth of C1/C2 view, examination of the cervical spine. A few fractures of the ring of the atlas (C1) and the dens of the axis (C2) may be better visualized on the AP open-mouth view.

46   

  The Cervical Spine

A

B FIGURE 6-3  A, Lateral radiograph. B, Alignment of spine.

(Figure 6-2B), and AP open mouth of C1/C2 (Figure 6-2C). Fractures and dislocations are best visualized on the lateral projection (Figure 6-2A). Rotational injuries and fractures of the lateral masses may be evident on the AP projection (Fig 6-2B). A few fractures of the ring of the atlas (C1) and the dens of the axis (C2) may be better visualized on the AP open-mouth view (Figure 6-2C).

Dens

C2 body Occipital condyle

C1 anterior arch-dens interval (broken red circle) Width of C2 and C3 (red line in C2-3 disc) Prevertebral soft tissues

  

Pattern of search: Lateral radiograph (Figure 6-3A) Basion-dens interval Atlanto-dens interval Alignment of spine (Figure 6-3B) Anterior spinal line (solid red line) Posterior spinal line (dashed red line) Spinolaminar line (dotted red line) Interspinous distance (red dots)

• Vertebral bodies configuration and alignment • Facet joints configuration, width and alignment • Prevertebral soft tissues

Computed tomography (MDCT).  MDCT has superseded

radiography for the initial assessment of older teenagers and adults because of the accuracy and ease of detecting injuries by MDCT in comparison to radiography. Therefore, when imaging is indicated, cervical spine MDCT is the initial diagnostic modality in all patients age 14 and older. CT examination: Minimum necessary Axial, sagittal, and coronal noncontrast 2 mm or thinner images in bone algorithm Extending through at least the level of T1 Axial and sagittal images in soft tissue algorithm

Pattern of search: AP radiograph (Figure 6-4A, B)

• Alignment of spinous processes (thin red line) • Alignment of vertebral bodies (thick red lines) • Interspinous distance (red dots) • Undulant, smooth contour of the articular pillars (arrows)

  

Open mouthed odontoid (Figure 6-5C)

Lateral view C1/C2 (Figure 6-5D)

Having a well-defined and consistent search pattern for cervical spine evaluation will allow rapid identification of cervical injuries in the trauma patient. The minimum should include follow:

Lateral alignment of C1-2 (short red lines) Atlanto-dental interval (thick red lines)

Clivus-dens interval (1-1.3 cm) Clivus-dens alignment (vertical red line)

Sagittal CT search pattern (Figure 6-6) • Right atlanto-occipital (occipital-C1) and atlanto-axial (C1-C2) joints (Figure 6-6A, B)

  

The Cervical Spine 

A

   47

B FIGURE 6-4  A, B, AP radiograph.

• C1 anterior arch – dens interval • Opisthion (posterior margin of foramen magnum) – C1 posterior arch – C2 spinolaminar junction alignment • Left lateral facet alignment and facet fractures • Left atlanto-occipital (OC-C1) and atlanto-axial (C1-C2) joints

A

C

B

D

FIGURE 6-5  A, Open-mouthed odontoid. B, Lateral view C1/C2. C, Open-mouthed odontoid (see table). D, Lateral view C1/C2 (see table).

• Right lateral facet alignment and facet fractures (Figure 6-6A, B) • Anterior spinal line and vertebral body heights (Figure 6-6C) • Posterior spinal line (Figure 6-6C) • Spinolaminar line (Figure 6-6C) • Interspinous distances and posterior spinous processes (Figure 6-6C) • Midline craniocervical junction alignment (Figure 6-6C) • Basion-dens interval

Axial CT search pattern (Figure 6-7A, B) 1. Vertebral body for fractures and uncovertebral joints 2. Transverse processes and transverse foramina 3. Pedicles 4. Facets (also referred to as articular pillars) 5. Posterior arch with laminae 6. Spinous process Coronal search pattern (Figure 6-8A, B) 1. Occipital condyles 2. Facets and lateral masses (also referred to as articular pillars) 3. Transverse processes Spinous processes (not shown) Soft tissue windows (Figures 6-9 and 6-10) • Prevertebral soft tissues • Paraspinous musculature for edema/ hemorrhage • Tectorial membrane at craniocervical junction • Spinal canal for disc injuries, epidural hematoma, bone fragments   

It is important to view all images in both bone and soft tissue windows. Abnormal findings in the soft tissues point to underlying bone and joint abnormalities. The normal appearance of the soft tissue anatomy at the craniocervical junction is shown in Figure 6-9A. Note the course and position of

48   

  The Cervical Spine

B

A

C

FIGURE 6-6  A, Right atlanto-occipital (occipital-C1) joint. B, Atlanto-axial (C1-C2) joint. C, Anterior spinal line and vertebral body heights, posterior spinal line, spinolaminar line, interspinous distances and posterior spinous processes, midline craniocervical junction alignment.

A

1

2 3

3 4

4

5 6

B FIGURE 6-7  A, B, Axial CT search pattern.

3

3 3

A

1

1

2

2

3

3

3

B FIGURE 6-8  A, B, Coronal search pattern.

2

The Cervical Spine 

A

B

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C

FIGURE 6-9  A, Normal appearance of the soft tissue anatomy at the craniocervical junction. Note the course and position of tectorial membrane extending from the clivus to the posterior surface of the dens. The posterior longitudinal ligament lining the spinal canal is seen on the posterior surface of the vertebral bodies, and the ligamentum flavum lining the posterior surface of the spinal canal is shown on and between the anterior surfaces of the laminae. B, Extradural hematomas pointing to underlying bone or joint abnormalities can be identified. C, The bone window clearly shows subluxation of the atlanto-occipital joint as the cause of the extradural hematoma.

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B

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D

FIGURE 6-10  A, Type II fracture of the dens. B, Mid-sagittal recon soft tissue window image revealed a small hematoma about the fracture. Closer inspection revealed a rounded density at the posterior surface of the C3-4 disc space and a similar density posteriorly consistent with an enfolded, hypertrophied ligamentum flavum. C, MRI of canal is constricted between these two densities. D, Herniated disc compressing the spinal cord.

tectorial membrane extending from the clivus to the posterior surface of the dens. The posterior longitudinal ligament lining the spinal canal is seen on the posterior surface of the vertebral bodies, and the ligamentum flavum lining the posterior surface of the spinal canal is shown on and between the anterior surfaces of the laminae (Figure 6-9A). Extradural hematomas pointing to underlying bone or joint abnormalities may be identified (Figure 6-9B). In this case, the bone window clearly shows subluxation of the atlanto-occipital joint (Figure 6-9C) as the cause of the extradural hematoma. Bulging or herniated discs may be identified indicating the need for further evaluation by MRI (Figure 6-10). This elderly patient sustained a type II fracture of the dens (Figure 6-10A). Mid-sagittal recon soft tissue window image revealed a small hematoma about the fracture. Closer inspection revealed a rounded density at the posterior surface of the C3-4 disc space and a similar density posteriorly consistent with an enfolded, hypertrophied ligamentum flavum (Figure 6-10B). The canal is constricted between these two densities. MRI confirms these findings (Figure 6-10C, D). Note the herniated disc compressing the spinal cord (Figure 6-10D). The spinal cord shows evidence of edema and/or myelomalacia. This proved to be important for preoperative planning. The fracture of the dens

was reduced and pinned with single-screw fixation. An anterior discectomy was performed at C3-4 to relieve the pressure on the spinal cord. C3-4 was fused with placement of bone graft and a metal cage in the disc space. Paraspinous musculature. Paraspinous muscular edema

is a useful sign, when present, to indicate the presence of significant injury to the cervical spine soft tissues. However, edema takes time to develop, and the absence of paraspinous muscular edema does not exclude soft tissue injury. Evaluate the paraspinous soft tissues on a narrow CT window to visualize this finding optimally (Figure 6-11A), confirmed on MRI in this patient (Figure 6-11B). Magnetic resonance (MR) evaluation. Indications for

MR imaging in the cervical spine have expanded in recent years. For a patient with suspected cervical spine trauma, the American College of Radiology (ACR) appropriateness criteria recommend MRI evaluation of the cervical spine in addition to MDCT, especially when ligamentous or neurologic injury is suspected. (ACR 2013 update). The spectrum of spinal cord injury ranges from mild edema manifested by increased T2 signal in a patient without underlying myelomalacia, to severe

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  The Cervical Spine

FIGURE 6-11  A, B, Paraspinous soft tissues on a narrow CT window, confirmed on MRI in this patient.

A

edema, cord hemorrhage, and transection. Extensive cord signal change or compression on MRI, in a patient with only a partial or mild neurologic deficit, indicates a spinal cord at risk for further injury and a patient in whom aggressive management is warranted. Integrity of the intervertebral disc and associated ligamentous structures is best evaluated with MRI. The anterior and posterior longitudinal ligaments, interspinous and supraspinous ligaments are assessed, in addition to the capsular ligaments of the facets. Imaging of the intervertebral disc can be complex, with annular fissures, disk protrusions and extrusions often difficult to date. Clinical history and physical exam findings are important in determining whether a disc protrusion is acute or chronic. A comprehensive review of cervical spine MRI is beyond the scope of this primer.

2. Common sites of injury in adults Craniocervical junction (skull base – C2) Fractures Occipital condyle Atlas – C1 Posterior arch Jefferson fracture – fractures of ring anterior and posterior Anterior arch Axis – C2 Odontoid (dens) Body Extension of dens fracture Teardrop fracture C2 neural arch – hangman’s fracture Dislocations/subluxation Atlanto-occipital dissociation Atlanto-axial dislocation

B

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B

FIGURE 6-12  A, B, Diagrams of craniocervical junction pinpointing the common sites of fractures and dislocations in adults. The most common sites of fracture are identified by red lines. Red arrows demonstrate displacement of the lateral masses of C1 indicative of simultaneous fractures of the anterior and posterior arches of the atlas (C1).

Craniocervical junction injuries Occipital condyle fractures. Occipital condyle fractures indicate disruption of the alar ligament, with or without other ligaments, at the craniocervical junction. The injury may be stable (unilateral ligament involvement) or unstable (bilateral involvement).    Diagnosis: There are three major types (Figures 6-13 and 6-14): Type I: comminution of the occipital condyle without significant displacement Type II: extension of a basilar skull fracture through the occipital condyle Type III: avulsion of the occipital condyle with inferomedial displacement   

Figure 6-15 is another type III fracture of the left occipital condyle shown in the axial (Figure 6-15A), coronal (Figure 6-15B), and sagittal (Figure 6-15C) left lateral reconstruction images.

  

Atlanto-occipital dissociation

Diagrams of the craniocervical junction (Figure 6-12A, 6-12B, Clivus, C1 and C2) pinpoint the common sites of fractures and dislocations in adults. The most common sites of fracture are identified by red lines. Red arrows demonstrate displacement of the lateral masses of C1 indicative of simultaneous fractures of the anterior and posterior arches of the atlas (C1). Your pattern of search should include all sites.

Mechanism. Atlanto-occipital dissociation is most commonly due to anterior dislocation of the head relative to the spine but may also be caused by longitudinal distraction or posterior dislocation. This injury is much more common in young children. Atlanto-occipital dissociation is usually fatal, particularly when widely displaced, but there are some survivors. Survival is three times more likely in children, principally in those with lesser injuries and displacement.

The Cervical Spine 

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C

FIGURE 6-13  A, Type I occipital condyle fracture: comminution of the occipital condyle without significant displacement. B, Type II occipital condyle fractures: extension of a basilar skull fracture through the occipital condyle. C, Type III occipital condyle fractures: avulsion of the occipital condyle with inferomedial displacement.

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B

C FIGURE 6-14  A, Type I occipital condyle fracture: comminution of the occipital condyle without significant displacement. B, Type II occipital condyle fractures: extension of a basilar skull fracture through the occipital condyle. C, Type III occipital condyle fractures: avulsion of the occipital condyle with inferomedial displacement.

Diagnosis. Evaluate the alignment of the occiput relative to C1. The joint surfaces should be parallel. The width of atlantooccipital articulation is generally ≤2 mm (Figure 6-16A, B). Look for supporting findings, like soft tissue swelling at the craniocervical junction (see Figure 6-18) or joint asymmetry (Figure 6-16C, D) compared with the contralateral side. This patient demonstrates atlantal-occipital joint widening (Figure 6-17A), posterior dislocation of the cervical spine (Figure 6-17B), and an increased basion-dens interval (Figure 6-17C). An anterior atlanto-occipital dissociation, with fracture of the right occipital condyle, is demonstrated by anterior displacement of the dens and C1 (Figure 6-18A, B) and an associated extradural hematoma at the foramen magnum (Figure 6-18B). Note also a small avulsion from the tip of the dens (Figure 6-18B). Axial (Figure 6-18C) and right sagittal images (Figure 6-18D, E) reveal a fracture of the right occipital condyle and anterior dislocation of the atlanto-occipital joint.

C1 ring fractures.  C1 ring fractures may involve the anterior

arch, the posterior arch, or both arches (Figure 6-19). Fractures involving both arches are known as Jefferson fractures. Posterior arch

Mechanism. Hyperextension of the head compressing C1 arch between occiput and neural arch of C2. Diagnosis. The most common posterior arch fracture is a bilateral vertical fracture of the neural (posterior) arch (Figures 6-20 and 6-21). However, this fracture must be distinguished from developmental defects, which have rounded, tapered, and corticated margins (Figure 6-21, black arrow). The latter is a congenital failure of fusion of the two limbs of the posterior arch in the midline, a common normal variant, associated with a dens fracture and bilateral fractures of the posterior arch in this patient (Figure 6-21).

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Anterior arch

Atlanto-axial dislocation

Mechanism. Hyperextension of the head upon the neck results in the dens pressing against the anterior arch of C-1 and results in simultaneous fractures of the dens and anterior arch (Figure 6-22A, B). Avulsions of the anterior longitudinal ligament and the longus colli muscle from their insertions create typically minimally displaced, horizontal fractures, often associated with dens fractures. Diagnosis. Segmental fractures of the anterior arch that are displaced anteriorly (Figure 6-22A), so-called “plough” fractures, are due to the shearing forces of hyperextension injuries in the elderly. These are commonly associated with fractures of the dens (Figure 6-22B).

Mechanism. Atlanto-axial dislocation (Figure 6-25A, B) is said to be the most common dislocation at the craniocervical junction but is rarely due to trauma. It is more commonly associated with rheumatoid arthritis, its variants, or Down syndrome. The dislocation may also be transient secondary to ligamentous laxity associated with severe infections of the head and neck. Diagnosis. Flexion views may be necessary to demonstrate the subluxation, which may be reduced in neutral position and extension. Normal distance of the anterior cortex of the dens to the posterior cortex of the anterior arch of the atlas:   

Jefferson fracture

•  2.5 mm in adults •  5 mm in children

Mechanism. Blow to the vertex (axial loading) as in diving into shallow water. Diagnosis. This is a comminuted C1 fracture that involves both the anterior and posterior arches with outward displacement of the fragments (Figure 6-23) and commonly referred to as a Jefferson fracture. Frontal radiograph (Figure 6-23A) and coronal CT images (Figure 6-23B) show lateral subluxation of the lateral margins of C1 on C2 bilaterally. Axial CT image (Figure 6-23C) and 3D reconstruction (Figure 6-23D, different patient) show two fractures in the anterior arch and one in the posterior arch. The reverse may also occur: two fractures in the posterior arch and one in the anterior arch (Figure 6-24A, B, C) or, alternatively, two fractures in each arch.

  

In