Little Ortho Book : the Bare Bones of Orthopedics. 9781617110863, 1617110868

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Ortho Book

Chen

The Little

The Bare Bones of Orthopedics

Dr. Antonia F. Chen takes complicated orthopedic terms and conditions and explains them in ways that are understandable to all. By focusing on common orthopedic diagnoses and relevant anatomy, The Little Ortho Book: The Bare Bones of Orthopedics answers the questions that arise from orthopedic conditions in user-friendly language that is understandable to everyone.

What Is Inside: • Descriptions of joint biomechanics and bone and muscle composition • Commonly performed exams are explained with a description of the condition being tested • Sports injuries, fractures, arthritis, and orthopedic conditions in children • Description of medications that are commonly prescribed in orthopedics • Commonly performed orthopedic surgeries, including indications for surgery and descriptions of the procedures performed—all described in simplistic detail

The Bare Bones of Orthopedics

Portable and handy and supplemented with images and diagrams, this conversational-style book packs a big punch!

The Little Ortho Book

The Little Ortho Book: The Bare Bones of Orthopedics is a pocket-sized, easy-to-understand introduction into the field of orthopedics. Written with the nonphysician in mind, The Little Ortho Book provides the basics of orthopedics for residents, medical students, front office staff, and industry sales force.

The Little

Ortho Book The Bare Bones of Orthopedics

The Little Ortho Book: The Bare Bones of Orthopedics is an easy-to-read resource for a wide variety of audiences who work in the orthopedic industry or with orthopedic patients, but aren’t orthopedic surgeons.

Antonia F. Chen MEDICAL/Orthopedics

S L A C K I N C O R P O R AT E D

Antonia F. Chen, MD, MBA University of Pittsburgh Department of Orthopaedic Surgery Pittsburgh, Pennsylvania

www.Healio.com/books ISBN: 978-1-61711-086-3 Copyright © 2014 by SLACK Incorporated Illustrations by Jeff Moore. Dr. Antonia F. Chen has received grants from the Scoliosis Research Society, Orthopaedic Research and Education Foundation, and the Pittsburgh Foundation. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without written permission from the publisher, except for brief quotations embodied in critical articles and reviews. The procedures and practices described in this book should be implemented in a manner consistent with the professional standards set for the circumstances that apply in each specific situation. Every effort has been made to confirm the accuracy of the information presented and to correctly relate generally accepted practices. The authors, editor, and publisher cannot accept responsibility for errors or exclusions or for the outcome of the material presented herein. There is no expressed or implied warranty of this book or information imparted by it. Care has been taken to ensure that drug selection and dosages are in accordance with currently accepted/recommended practice. Due to continuing research, changes in government policy and regulations, and various effects of drug reactions and interactions, it is recommended that the reader carefully review all materials and literature provided for each drug, especially those that are new or not frequently used. Any review or mention of specific companies or products is not intended as an endorsement by the author or publisher. SLACK Incorporated uses a review process to evaluate submitted material. Prior to publication, educators or clinicians provide important feedback on the content that we publish. We welcome feedback on this work. Published by:

SLACK Incorporated 6900 Grove Road Thorofare, NJ 08086 USA Telephone: 856-848-1000 Fax: 856-848-6091 www.Healio.com/books

Contact SLACK Incorporated for more information about other books in this field or about the availability of our books from distributors outside the United States. Library of Congress Cataloging-in-Publication Data Chen, Antonia, author. The little ortho book : the bare bones of orthopedics / Antonia F. Chen. p. ; cm. Includes bibliographical references and index. ISBN 978-1-61711-086-3 (alk. paper) I. Title. [DNLM: 1. Orthopedics--Handbooks. 2. Bone and Bones--Handbooks. 3. Orthopedic Procedures--Handbooks. WE 39] RD731 616.7--dc23 2013022705 For permission to reprint material in another publication, contact SLACK Incorporated. Authorization to photocopy items for internal, personal, or academic use is granted by SLACK Incorporated provided that the appropriate fee is paid directly to Copyright Clearance Center. Prior to photocopying items, please contact the Copyright Clearance Center at 222 Rosewood Drive, Danvers, MA 01923 USA; phone: 978-750-8400; Web site: www.copyright.com; email: [email protected]

DEDICATION This book is first and foremost dedicated to the person I look up to the most: my mother, Dr. Jean F. Lian, who raised me and always believed in me. Her love, strength, and courage made me the woman and doctor that I am today. This book is also dedicated to my sister, Victoria F. Chen, who constantly has my back, listens to all my craziness, and always cheers me on. I love and admire her for her thoughtfulness and generosity throughout all the years and distance. Importantly, this book is dedicated to my husband, Dr. MingDe Lin, who is incredibly patient, keeps me grounded, supports me in all my sleepless endeavors, and who shows me unconditional love. Finally, this book would not be possible without the support of my friends and other orthopedic residents. Thank you to my 2 most important mentors in orthopedics—Dr. Brian A. Klatt and Dr. Alfred J. Tria Jr. You have both inspired me to become an arthroplasty surgeon and taught me and encouraged me along the way.

CONTENTS Dedication................................................................ v Acknowledgments ................................................... ix About the Author.................................................... xi Preface ...................................................................xiii Chapter 1 Bones, Bones, Bones ............................1 Chapter 2 Help! I Pulled a Muscle! ....................13 Chapter 3 Joint Commission ..............................25 Chapter 4 Back to the Basics ...............................35 Chapter 5 Skin and Bones ...................................43 Chapter 6 Dry Bones............................................57 Chapter 7 Bad to the Bone ..................................65 Chapter 8 Little Bones..........................................77 Chapter 9 Bones and Groans ..............................91 Chapter 10 Bone to Pick ........................................99 Bibliography .......................................................... 115

ACKNOWLEDGMENTS This book was only made possible with the help and influence of many individuals. First of all, I would like to thank the following individuals at SLACK Incorporated—Carrie Kotlar, John Bond, Jennifer Cahill, April Billick, and Michelle Gatt—whose support and guidance made this book possible. Personally, I would like to thank Dr. Bor-Kuan Chen for being my father and for stimulating my intellectual scientific curiosity. I would also like to thank Dr. Wenmin Chuu for his constant support and care for our family. Professionally, I would like to thank Dr. Freddie H. Fu for being my role model, my chairman, and a great educator. I would also like to thank Dr. Alfred J. Tria Jr and Dr. Brian A. Klatt who both inspired me to pursue a career in orthopedics. My sincere thanks to Dr. Javad Parvizi, Dr. Lawrence S. Crossett, and Dr. Adolph “Chick” Yates for being outstanding arthroplasty surgeons who have patiently taught and guided me. Thank you to Dr. Nalini Rao for encouraging my interest in periprosthetic infections. Additionally, I would like to thank Dr. Rocky S. Tuan for great research ideas and encouraging me to pursue research. Many people in the Department of Orthopaedics at the University of Pittsburgh have greatly influenced my education during my residency and I thank them from the bottom of my heart. These individuals include Dr. Vincent F. X. Deeney, Dr. William F. Donaldson, Dr. Andrew R. Evans, Dr. Mark A. Goodman, Dr. Gary S. Gruen,

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Dr. Christopher D. Harner, Dr. James D. Kang, Dr. Joon Y. Lee, Dr. Richard L. McGough III, Dr. Stephen A. Mendelson, Dr. Volker Musahl, Dr. Peter A. Siska, Dr. Ivan S. Tarkin, Dr. W. Timothy Ward, Dr. Kurt R. Weiss, Dr. Dane K. Wukich, and Dr. Vonda J. Wright. To all of my attendings, fellow residents, medical students, and college students with whom I have worked—thank you for your dedication to the field, for teaching me, and for being current and future colleagues. For my friends and family—thank you for your unwavering support and for listening to me. If it weren’t for you, I would go insane!

ABOUT THE AUTHOR Antonia F. Chen, MD, MBA, received her bachelor’s of science from Yale University. She then received her medical degree from UMDNJRobert Wood Johnson, where she graduated with Distinction in Research and was inducted into the Alpha Omega Alpha Medical Honor Society. Antonia also received her master of business administration from Rutgers Business School, and graduated as a member of the Beta Gamma Sigma Honor Society. She is currently an orthopedic resident at the University of Pittsburgh. In addition to clinical duties, her research interests are in arthroplasty and she has delivered many podium presentations and posters on the national stage. Antonia has also received numerous awards during residency, including the Jacquelin Perry, MD, Resident Research Award for clinical research; the Jeannette Wilkins Award for basic science research; and the Gold Foundation Humanism and Excellence in Teaching Award. She has served as a resident liaison for the membership committee in the American Association of Hip and Knee Surgeons. Antonia hopes to pursue a rewarding career as an academic arthroplasty surgeon.

PREFACE Orthopedics is a complex field, but when you’re armed with the right terminology and basic concepts, the field can be … dare I say it, fun? This book was created as an orthopedic reference tool for any individual who is curious about orthopedics, who sustained an orthopedic injury, or who may be undergoing orthopedic surgery. It’s written in an informative, fun, and engaging manner to give an introduction to the field of orthopedics. Sit back and enjoy learning about one of the best fields in medicine!

Chapter 1

Bones, Bones, Bones There are 206 bones in the adult human body. That’s a lot of bones! But there are even more bones when you’re born; infants can have anywhere from 270 to 300 bones. As we mature, our bones join together to form the adult skeleton. The skeleton is a vital part of the human body because it gives structure to our bodies and protects vital organs. Bones that come together at a joint are said to articulate with each other, which allows the body to move. Bones provide a site for ligaments to attach, which keeps bones connected together, and for tendon attachments, which connect muscles to bones. The next chapter will discuss muscles in greater depth. In the adult skeleton, there are 28 bones in the skull and 24 ribs. More than half of the bones in the body are

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in the hands and feet, where one hand has 27 bones and one foot has 26 bones for a total of 106 bones in the hands and feet. The largest bone in your body is your femur, or thigh bone, and the smallest bone is the stapes in your ear. In orthopedics, the focus is on the bones in the spine (33 vertebrae), extremities (arms and legs), and pelvis. Each of these sections will be discussed in depth below.

SPINE The spine is composed of specific bones called vertebrae that stack up on each other to form a supportive column for the skull, serves to maintain one’s height, and provides a place for ribs to attach. There are 7 vertebrae in the upper spine (cervical spine), 12 vertebrae in the middle spine (thoracic spine), normally 5 vertebrae in the lower spine (lumbar spine), 5 fused vertebrae in the bottom of the spine (sacrum), and 4 fused vertebrae at the tip of the spine (coccyx, or tail bone) (Figure 1-1). Approximately 10% of people are born with an extra lumbar vertebra, which does not cause any problems.

Cervical The vertebrae in each segment of the spine are similar but have distinct differences. The first cervical vertebra (C1) is also known as the atlas, which holds up the base of the skull. It is responsible for 50% of the flexion and extension of the neck, which allows you to nod your head “yes.” The front part of the vertebrae is called the anterior arch, and the back part of the vertebrae is called the posterior arch. The second cervical vertebra (C2), or the axis, is unique because it has an additional bony piece in the front, or anterior, portion of the vertebrae. This bony prominence is called the dens. This allows for sideto-side motion of the head and for you to shake your

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Figure 1-1. Bones in the spine.

head “no.” This bone can be broken during trauma, and depending on the level of the break, patients can be treated with a collar, a halo, or may require surgery. After the C2 vertebra, the C3 through C7 vertebrae are similar. From the top view, the spinous process is on the back, or posterior, part of the vertebrae. The spinous process of C7 is the most prominent and can often be felt at the back of the neck. For each vertebra, there is a roof protecting the spinal cord called the lamina, which is connected to the body of the vertebrae through the pedicles. Within each vertebra, there is the foramen transversarium, which protects the vertebral artery as it travels through. Each of the vertebrae are connected to the other through the joints, or the articulating facets. The vertebra above has an inferior (lower) articulating facet that connects to the vertebra below, which has a superior (higher) articulating

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facet. The spinal nerves travel above the level of the vertebra (eg, the C5 nerve root travels above the C5 vertebra). The cervical spine is unusual because there are 8 cervical nerves but only 7 cervical vertebrae, so the C8 nerve root travels below the C7 vertebra.

Thoracic The thoracic spine vertebrae are similar to the lower cervical vertebrae except that they are larger in size and there is no foramen transversarium. The thoracic vertebrae also consist of spinous processes, with lamina covering the vertebral foramen where the spinal cord is housed. Pedicles connect the lamina with the vertebral body, and screws are placed in there during surgery. The ribs connect, or articulate, with the transverse process of the thoracic vertebrae, so there are facets present on the bone to accommodate for this. The spinal nerves travel below the level of the vertebra (eg, the T1 nerve root travels below the T1 vertebra).

Lumbar The lumbar spine vertebrae are larger versions of the thoracic vertebrae, without places for the ribs to connect. The lumbar vertebrae allow for bending forward and back from the waist and provide the natural curve of the back toward the front of the body (lordosis). Lower back pain is often attributed to disease in the lumbar spine.

UPPER EXTREMITY Hand and Wrist Your hand consists of the wrist and 5 fingers. The fingers can either be named numerically (thumb is 1st and pinkie is 5th) or by name, including the thumb, index,

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Figure 1-2. Hand and wrist.

long/middle, ring, and small fingers. The 27 bones in the hand (Figure 1-2) are divided into 3 sections: the fingers, the metacarpals, and the carpal bones. For your fingers, every knuckle in your fingers is a joint where 2 bones connect. All fingers have 3 knuckles, except for the thumb, which only has 2. The joint that is closest to your fingernail, or the distal interphalangeal joint, connects the distal (furthest) phalanx to the middle phalanx. The next knuckle, or the proximal interphalangeal joint, connects the middle phalanx to the proximal phalanx. The closest knuckle (metacarpal phalangeal joint) connects the proximal phalanx to the metacarpals.

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Figure 1-3. Forearm and elbow.

The metacarpals are the bones that connect the fingers to the wrist. The wrist consists of carpal bones that lie in 2 rows. The first row consists of the following bones, starting from the bone closest to the arm and closest to the thumb: scaphoid, lunate, triquetral, and pisiform. The second row above that consists of the trapezium, trapezoid, capitate, and hamate. These bones are coated in cartilage, which allows for the multidirectional movement of the wrist.

Forearm and Elbow The forearm is the area between the wrist and elbow, and it consists of 2 bones—the radius (on the thumb side) and the ulna (on the pinkie side) (Figure 1-3).The 2 bones are connected by a ligament, called the interosseous membrane, which allows the forearm to rotate (pronate and supinate). The radius is wide at the wrist and the ulna is wide at the elbow. The elbow consists of the wide portion of the ulna, called the olecranon, and the narrow part of the radius, called the radial head. These bones meet up with the humerus to form the elbow, which bends and extends the arm.

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Figure 1-4. Humerus and shoulder (anterior and lateral views).

Humerus and Shoulder The upper part of the arm consists of the humerus, which is the bone between the shoulder and elbow (Figure 1-4). The top of the humerus, or the humeral head, forms half of the shoulder joint, with the other half consisting of the glenoid, which is the cup-like structure that is part of the scapula (shoulder blade). The shoulder joint is held together by the soft tissue structures of the capsule and labrum. The other bones around the shoulder include the clavicle (front), which is connected to the acromion (side), and the scapula (back).

LOWER EXTREMITY Foot The foot is important as it bears the weight of the entire body. The 1st toe of the foot supports 50% of our body weight! The bones of the foot can be divided into

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Figure 1-5. Foot.

the following sections (Figure 1-5): forefoot, midfoot, and hindfoot. The forefoot consists of the bones in the 5 toes, which is similar to the bones in the fingers. Each wrinkle in your toes is made by 2 bones coming together at a joint. For the 2nd to 5th toes, the farthest bone in your toes is the distal phalanx. The next bone is the middle phalanx, and the closest bone in your toes is the proximal phalanx. For the 1st toe, or great toe, it only consists of 2 bones—a distal and a proximal phalanx. All 5 toes have a metatarsal bone, which connects

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the forefoot to the midfoot. The midfoot consists of the cuboid, navicular, and 3 cuneiform (medial, intermediate, and lateral) bones. These bones compose the arch of the foot, which serves as the shock absorber to the foot. The hindfoot consists of the calcaneus, or the heel bone, and the talus. The talus rests on top of the calcaneus, which contributes to ankle motion.

Lower Leg and Ankle The lower leg, or the area between the ankle and the knee, consists of the tibia (larger bone) and fibula (smaller bone toward the outside). The tibia is commonly referred to as the shin bone. The 2 bones are connected by a ligament, called the interosseous membrane. This is analogous to the radius and ulna of the forearm, as these 2 bones rotate around each other to provide movement to the lower extremity. The ankle joint consists of the articulation between the tibia/fibula and the talus, and the plafond is the area where the tibia meets the talus (Figure 1-6). These bones are held together by multiple ligaments that can be sprained, and the most common bone to break in an ankle fracture in this region is the fibula.

Femur, Knee, and Hip The femur is the largest and strongest bone in the body. Both femoral condyles (medial condyle is toward the inside, and the lateral condyle is toward the outside) that are at the end of the femur join with the tibial plateau to form the knee (see Figure 1-6). The top of the femur, or the femoral head, articulates with the acetabulum to make the hip. The femur is a key bone that aids with hip movement, as many muscles responsible for hip motion are attached to the femur.

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Figure 1-6. Lower extremity (hip, femur, knee, tibia/fibula, ankle).

PELVIS The pelvis consists of 3 bones when we are young: the ilium, the pubis, and the ischium (Figure 1-7). As we age, the bones fuse together to make the acetabulum, where the femoral head sits. The ilium is the large wing of the pelvis, the pubis is the front and top of the pelvis, and the

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Figure 1-7. Pelvis.

ischium is the bone that makes up the front and bottom part of the pelvis. The pelvis is the key bone to facilitate moving transfers, as weight is transferred between the lower extremities and the axial spine.

Chapter 2

Help! I Pulled a Muscle! If you thought there were a lot of bones in the body, there are even more muscles—approximately 640 muscles in the human body. Muscles are attached to bones with tendons, and muscles are able to contract, which is important for moving the body around. There are muscles throughout the body, but the most important muscles in orthopedics are those that move the spine, upper extremities, and lower extremities (Figures 2-1 through 2-4).

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Figure 2-1. Superficial anterior (front) muscles of the body. (Adapted from Leonard P. Quick and Easy Terminology. 2nd ed. Philadelphia, PA: WB Saunders; 1995.)

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Figure 2-2. Superficial posterior (back) muscles of the body. (Adapted from Leonard P. Quick and Easy Terminology. 2nd ed. Philadelphia, PA: WB Saunders; 1995.)

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Figure 2-3. Deep anterior (front) muscles of the body. (Adapted from Leonard P. Quick and Easy Terminology. 2nd ed. Philadelphia, PA: WB Saunders; 1995.)

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Figure 2-4. Deep posterior (back) muscles of the body. (Adapted from Leonard P. Quick and Easy Terminology. 2nd ed. Philadelphia, PA: WB Saunders; 1995.)

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SPINE The spine is commonly divided into 3 sections—the cervical spine (neck), the thoracic spine (trunk), and the lumbar spine (lower back). The thoracic and lumbar spine share similar muscle groups and are combined into one section.

Neck Neck motion is based off of many muscles. In the front of the neck, the platysma muscle is the first layer of muscle that moves the lower jaw and draws the lower lip downward. The sternocleidomastoid muscles are underneath, and they turn the head from side to side. Other muscles that are responsible for rotation of the neck include the obliquus capitis inferior, obliquus capitis superior, rectus capitis lateralis, longissimus capitis, splenius capitis, and semispinalis capitis. To bend the neck forward (flexion), the front (anterior) fibers of the sternocleidomastoid muscles are responsible for some motion, along with the longus capitis and the rectus capitis anterior. To bend the neck back (extension), there are more muscles involved. The back (posterior) fibers of the sternocleidomastoid muscles are responsible for limited extension, while these other muscles contribute to neck extension: semispinalis capitis, splenius capitis, rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis superior, longissimus capitis, and the upper fibers of the trapezius muscle.

Trunk and Lower Back Bending back, or extension, involves one main muscle, called the erector spinae, or sacrospinal muscle group. This muscle is composed of 3 smaller groups, including the iliocostalis, longissimus, and spinalis muscles.

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Bending forward, or flexion, involves only the lumbar spine and not the thoracic spine. The front muscles of the abdomen, including the rectus abdominis, and the external and internal oblique muscles, contribute to spine flexion without directly attaching to the spine. Other trunk muscles, including the trapezius and latissimus dorsi, can contribute to spine flexion. The main contributor to lateral bending and rotation of the spine and rotation is the quadratus lumborum muscle. Other muscles that also contribute to this movement include the multifidus, iliocostalis lumborum, iliocostalis thoracis, rotatores, intertransversarii, psoas major, and obliques.

UPPER EXTREMITY The important motions of the upper extremity include motion around the shoulder joint, elbow flexion (bending) and extension (straightening), wrist flexion and extension, and hand motion.

Shoulder The shoulder is a joint that requires multidirectional motion. There are 4 muscles that surround the shoulder joint, called the rotator cuff muscles, which are responsible for shoulder movement. These muscles include the supraspinatus (top part of the shoulder), infraspinatus (back of the shoulder), teres minor (below the infraspinatus), and the subscapularis (front of the shoulder). The motions around the shoulder can be divided into the following movements: flexion (forward), extension (backward), adduction (across the body), abduction (away from the body), internal rotation (toward the belly), and external rotation (behind the back). Shoulder flexion mostly involves muscles outside of the shoulder joint. These muscles include the deltoid,

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pectoralis major, coracobrachialis, and the short head of the biceps brachii. Similarly, shoulder extension involves muscles outside of the shoulder, including the latissimus dorsi, posterior deltoid, pectoralis major, teres major, and the long head of the triceps brachii. Shoulder adduction involves similar muscles as shoulder extension, without the deltoid and with the addition of the coracobrachialis muscle. Shoulder abduction involves the deltoid initially, then the supraspinatus. Internal rotation of the shoulder involves the subscapularis, latissimus dorsi, pectoralis major, and the anterior fibers of the deltoid. External rotation of the shoulder involves the teres minor, infraspinatus, and posterior fibers of the deltoid.

Elbow In order to move the elbow, muscles must cross from the upper arm to the forearm to exert a force across the elbow. For elbow flexion, the brachialis, biceps brachii, and brachioradialis muscles are responsible. Elbow extension is performed by the triceps brachii and the anconeus muscles.

Forearm The forearm can rotate into pronation, or internal rotation of the forearm so that the palm is down, or supination, or external rotation of the forearm so that the palm is up. The pronator quadratus, pronator teres, flexor carpi radialis, and anconeus are responsible for pronation, while the supinator and biceps brachii are responsible for supination.

Wrist The motion around the wrist can be divided into 4 main groups, including flexion, extension, and sideto-side motion (adduction, or movement toward the

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ulna, and abduction, or movement toward the radius). Wrist flexion muscles mostly begin with the word flexor and include the flexor carpi radialis, flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus, palmaris longus, and abductor pollicis longus. Similarly, wrist extensors start with extensor and include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum, extensor pollicis longus, extensor indicis, and extensor digiti minimi. Wrist adduction, or ulnar deviation (moving the hand toward the ulna), mostly involves 2 muscles: the flexor carpi ulnaris and extensor carpi ulnaris. Wrist abduction, or radial deviation (moving the hand toward the radius), involves the extensor carpi radialis longus, extensor carpi radialis brevis, flexor carpi radialis, abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus.

Hand The muscles responsible for movement of the hand are mostly forearm muscles that cross over the wrist joint and insert into the hand. For finger flexion, the flexor digitorum profundus inserts into the further finger bone (distal phalanx) and the flexor digitorum superficialis inserts into the next closest bone (middle phalanx). Other muscles responsible for finger flexion include the flexor digiti minimi, abductor digiti minimi, flexor pollicis brevis and longus, interossei, and lumbricals. For finger extension, the extensor digitorum, extensor pollicis longus and brevis, extensor indicis, and extensor digiti minimi all contribute to both wrist and finger extension. For finger movement, the fingers can either move toward each other (adduction) or away from each other (abduction). For finger adduction, the palmar interossei are the muscles that are responsible, with contribution from the adductor pollicis. For finger abduction, the

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dorsal interossei muscles are responsible, along with the abductor digiti minimi and abductor pollicis brevis and longus.

LOWER EXTREMITY The important motions in the lower extremity include hip motion, knee flexion and extension, and ankle flexion and extension. The lower extremities are important for walking and mobility.

Hip The hip joint is created with an acetabulum (socket) and femoral head (ball), which allows for multidirectional movement. The planes of motion are similar to the shoulder, with flexion, extension, adduction, abduction, internal rotation, and external rotation. Hip flexion allows one to bring the leg up, as if walking up stairs. The muscles responsible for this motion include the iliopsoas, tensor fascia lata, rectus femoris, sartorius, adductor brevis and longus, and pectineus. Hip extension allows one to bring the leg back, as when walking backward. Muscles that are responsible for this action include the gluteus maximus and the hamstring muscles (semitendinosus, semimembranosus, and biceps femoris). Hip adduction, or movement of the leg across the body, involves the adductor muscles (brevis, longus, and magnus), pectineus, and gracilis. Hip abduction, or movement of the leg away from the body, involves the gluteus medius, gluteus minimus, tensor fascia lata, and sartorius. Internal rotation of the hip, or turning the thigh inward, involves the gluteus medius, gluteus minimus, and tensor fascia lata. External rotation of the hip, or turning the thigh outward as if crossing one’s legs into

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a figure 4, involves the short external rotator muscles (gemellus inferior and superior, obturator internus and externus, and quadratus femoris), piriformis, gluteus maximus, and sartorius.

Knee The most important motions around the knee include flexion, or bending of the knee back toward the buttock, and extension, or stretching the knee out so that the leg is straight. Knee extension is performed by the quadriceps, which is named because it includes 4 muscles. These 4 muscles include the vastus lateralis (outside muscle), vastus intermedialis (middle muscle), vastus medialis (middle muscle), and rectus femoris. The main muscle group responsible for knee flexion is composed of the hamstring muscles, which consist of the biceps femoris, semitendinosus, and semimembranosus. Other muscles, including the gracilis, sartorius, popliteus, and gastrocnemius, also contribute to knee flexion.

Ankle The ankle mostly moves in 2 planes. Plantarflexion is extension of the ankle and the foot goes toward the ground. The muscles responsible for this motion include the gastrocnemius, soleus, plantaris, tibialis posterior, flexor hallucis longus, and flexor digitorum longus. Dorsiflexion is flexion of the ankle and the foot goes up toward the body. The muscles responsible for dorsiflexion include the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus tertius.

Foot Similar to the wrist and hand, muscles that span the ankle are also responsible for motion in the foot. The 2 most important motions of the foot include inversion, or turning the foot inward, and eversion, or turning

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the foot outward. Inversion, also known as supination, involves the tibialis anterior and posterior. Eversion, also known as pronation, involves the peroneus brevis, peroneus longus, and peroneus tertius. There are also 4 major planes of motion for the toes. Toe flexion, or curling of the toes, is mostly controlled by “flexor” muscles, including flexor hallucis brevis and longus, flexor digitorum brevis and longus, and flexor digiti minimi brevis. Other muscles that flex the toes include the quadratus plantae, adductor hallucis, abductor hallucis, abductor digiti minimi, and interossei. Toe extension, or straightening of the toes, is controlled by the extensor hallucis longus, extensor digitorum, extensor digitorum brevis, and lumbricals. Toe abduction, or moving the toes away from each other, is performed by the abductor hallucis, abductor digiti minimi, and dorsal interossei. Toe adduction, or moving the toes toward each other, is performed by the adductor hallucis and plantar interossei, which is similar to the hand.

Chapter 3

Joint Commission Wherever a bone comes in contact with another bone, there is a joint that allows for movement. The term arthrosis is an equivalent name for a joint. Because the number of bones in the body varies from birth to adulthood, it’s difficult to say exactly how many joints there are in the body, but estimates range from the 200s to 300s.

TYPES OF JOINTS Joints are defined by the connective tissue that holds them together and the amount of motion they permit. There are 3 main types of joints in the body: fibrous, cartilaginous, and synovial joints.

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Fibrous joints consist of 2 bones connected by dense connective tissue. These joints make up immovable joints, called synarthroses. These joints are different than synovial joints, as they have no joint cavity. Examples of fibrous joints include the sutures in the human skull and the syndesmoses found between the radius and ulna, as well as the tibia and fibula. Cartilaginous joints consist of bones that are connected by cartilage, including fibrocartilage and/or hyaline cartilage. These joints have more motion than fibrous joints and are called amphiarthroses. There are 2 types of cartilaginous joints: synchondroses (primary cartilaginous joints) and symphyses (secondary cartilaginous joints). Synchondroses consist of hyaline cartilage and often appear in the growth plates (ossification centers) of long bones. In adults, an example of a synchondrosis is the joint between the 1st rib and the sternum (sternocostal joint). Symphyses often consist of hyaline cartilage around the ends of bones and fibrocartilage between the bones. Examples of symphyses in the human body include intervertebral discs, the pubic symphysis (the front part of the pelvis), and the manubriosternal joint (between the manubrium and sternum). Synovial joints are the most common joints in the body. These joints consist of 2 bones covered at the ends with articular (hyaline) cartilage that are held together by a joint capsule and ligaments. The joint capsule consists of a fibrous outer membrane and an inner synovial membrane. This synovial membrane lines the joint cavity, and the cells of the synovial membrane (synoviocytes) produce synovial fluid, which acts as lubricant when the joint moves (Figure 3-1). These joints are able to freely move and are called diarthroses. These joints are unique because they have little friction or low coefficients of friction (0.01 to 0.04). The fluid film created by the synovial fluid creates a boundary between the bones, which is attributable to the molecule lubricin.

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Figure 3-1. Synovial joint.

There are many types of synovial joints throughout the body that are separated by their mechanical composition. Hinge joints, like the hinges on a door, allow a joint to “open” and “close,” or flex (bring the bones closer to one another) and extend (bring the bones further away from each other). Examples of hinge joints include the elbow (humeroulnar joint) and the knee. Ball-and-socket joints allow for motion in many different planes and can be found in the hip (where the femoral head is the ball and the acetabulum is the socket) and the shoulder (where the humeral head is the ball and the glenoid is the socket). Pivot joints allow the bones to twist around each other, or rotate around an axis. Examples include the atlanto-axial joint, or the joint between cervical vertebrae 1 and 2, and the radioulnar joint, or the joint between the proximal radius and ulna. Ellipsoid joints are also known as condyloid, condylar, or bicondylar joints. These joints are similar to the ball-and-socket joint, in that

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they allow motion in many planes, but are more limited in motion than ball-and-socket joints. Examples include the wrist (the joint between the radius and carpal bones), knuckles (metacarpophalangeal joint), and the atlantooccipital joint (the joint between the skull and the 1st cervical vertebrae). Saddle joints look like the saddle on a horse and allow back and forth movement, as well as up and down movement, but do not permit rotation. An example of a saddle joint is the carpometacarpal joint, or the joint between the carpal bones of the hand and the longer metacarpal bone of the hand. Finally, gliding joints allow bones to slide past one another in the same plane. Examples include the midcarpal joints in the hand and the midtarsal joints in the foot.

BIOMECHANICS OF JOINTS The purpose of joints is that they allow motion between 2 bones. This motion often occurs as a result of the body operating as a system of levers.

Levers Levers are like seesaws on the playground; there is a fixed point in the ground called the fulcrum and a rigid bar that moves depending on the force placed on one end (effort) that causes motion at the opposite end to move a load (Figure 3-2). The purpose of a lever is that it multiplies the effort of an applied force from the muscle and increases the velocity (or speed) of movement. Depending on the location of the fulcrum, effort, and load, different advantages are conferred across joints. These are divided into 3 classes of levers. Class 1 levers place the fulcrum between the load and the effort. This results in a balanced system, where a directly applied force (effort) results in the movement of load. An everyday example of a first-class lever is

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Figure 3-2. Levers.

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scissors, where the effort applied by the hand using the handles passes through the fulcrum of the scissors and directly translates to a load where an item can be cut. In the human body, an example of a first-class lever is elbow extension. The triceps contracts (effort), the elbow is the fulcrum, and the load is the forearm that moves away from the upper arm. If the fulcrum is moved closer to the effort, then there will be increased speed and range of motion around the joint. If the fulcrum is moved closer to the load, then there will be increased strength. This lever provides balance to joints. Class 2 levers place the load between the fulcrum and the effort. This results in a system where the applied force (effort) results in a movement of the load in the same direction. An everyday example of a second-class lever is a nutcracker, where the effort applied at the handle is transmitted to the fulcrum at the opposite end of the nutcracker, which results in breaking of the nut in the middle. A wheelbarrow is another example, where lifting the handles (effort) around the wheel (fulcrum) results in the lifting of the load in the middle. In the human body, plantarflexion, or downward motion of the foot, is based off of a class 2 lever. When the gastrocnemius and soleus muscles contract, the force travels through the fulcrum (ball of the foot) and results in the foot coming off the ground. This lever provides strength to joints. Class 3 levers place the effort between the fulcrum and the load. This provides a lever where the force arm (effort) provides motion to the load in the same direction. In the human body, elbow flexion is an example of a third-class lever. When the biceps contracts, the force through the fulcrum (elbow) results in lifting the load at the hand. This lever provides speed and range of motion to joints.

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JOINT REACTIVE FORCES While levers cause joints to move, there are multiple forces that can act across a joint that cause it to move. These forces, called joint reactive forces, are the forces generated by equal and opposite forces between 2 adjacent bones in a joint. The knee and the hip are 2 common joints where the biomechanics of joints are described. For the hip joint, which includes the acetabulum (socket) and femoral head (ball), the joint reactive force (R) is dependent on the muscles surrounding the hip joint, the offset of the femur (A = the distance from the center of the femoral head to the edge of the femur, or the greater trochanter), and the distance from the femoral head to the center of the pelvis (the pubis), or B (Figure 3-3). The implication of this free body diagram is that if A, or the offset, is smaller, there are higher joint reactive forces. If B is smaller, then the joint reactive forces are smaller. With higher joint reactive forces, there is more pressure across the joint, and with lower joint reactive forces, there is less pressure across the joint. The knee joint is special because the patella, or knee cap, is present. The patella increases the mechanical advantage of the muscles around the knee so that greater force can be generated. The patellofemoral joint reaction force is generated by the sum of the force from the quadriceps tendon (above the knee) and the patellar tendon (below the knee) (Figure 3-4). In knee flexion, there is increased compressive force at the knee, and in knee extension, the quadriceps muscle is predominantly working so there is greater tension across the knee.

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Figure 3-3. Hip forces. A = distance from the center of the femoral head to the greater trochanter (offset), B = distance from the femoral head to the center of the pelvis, M = abductor force, My = y vector of abductor force, R = joint reactive force, Ry = y vector of joint reactive force, W = body weight.

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Figure 3-4A. Knee forces. The patellofemoral joint reaction force (P) is the sum of quadriceps tendon force vector (FQ) and the patellar tendon force vector (FT).

Figure 3-4B. Knee forces. As the knee flexes, the compressive force (FC) across the patellofemoral joint increases as the quadriceps (FQ) and patellar (FP) tendon alignment changes.

Chapter 4

Back to the Basics As was mentioned in Chapter 1, bones give structure to the body. However, bones are more than just the framework on which the body hangs. Unlike the steel beams of a building, bones are living organs that are responsible for many other important functions in the human body, including producing cells in our blood and regulating our calcium metabolism. Muscles are important because they make bones move.

WHAT ARE BONES MADE OF? Bone is a substance made of a mix of hard and soft materials, which makes it a composite material that can absorb impact and not break. The hard material is

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a mineral called hydroxyapatite, which is composed of calcium and phosphate. This inorganic material comprises 70% of calcified bone and gives structure to the bone. When minerals fail to deposit in bone, medical conditions associated with low vitamin D levels, such as rickets and osteomalacia, will occur and result in weakened bone. The soft material is called collagen, which is composed of 3 intertwined protein chains that are bound together into larger fibers. Type I collagen is present in bone, compared to Type II collagen found in cartilage. The organic material (collagen and protein) makes up 25% of calcified bone and forms the osteoid of the bone, which serves as the matrix in which bone cells can grow. Abnormalities in collagen scaffold formation can be caused by a genetic condition (osteogenesis imperfecta) or lack of vitamin C (scurvy). There are 3 main types of cells that are responsible for maintaining bone. Osteoblasts are the bone-building cells of the body, which are derived from stem cells. They produce bone matrix and cause mineralization of bone. Osteocytes are mature osteoblasts that are incorporated into osteoid and become part of calcified bone. Osteocytes make up 90% of all cells in bone, and they communicate with one another to initiate changes in bone. Osteoclasts are the bone-destroying cells of the body, which are derived from the cell line of white blood cells (monocytes/macrophages). Osteoclasts resorb bone when bone is remodeling, or if the body needs more minerals (calcium and phosphorus) to function. These cells are constantly working together because bone is constantly changing. Like snakes that shed their skin, the tissue in our skeleton is replaced many times throughout life with osteoclasts breaking down bone and osteoblasts building it up. Bones are composed of 2 main types of bone (Figure 4-1). There’s a harder, outer layer that gives support and

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Figure 4-1. Cross section of diaphyseal bone (eg, showing cortical versus cancellous bone).

structure, which is called cortical or compact bone. The inner, softer layer is called cancellous bone, which is also known as spongy bone or trabecular bone. Cancellous bone contains bone marrow, which is where red and white blood cells are made. The bones of the body have different compositions of cancellous and cortical bone, depending on the function of the bone. Longer bones that provide structural support, such as the femur, have more cortical bone, while shorter bones, such as the bones of the wrist and ankle, have more cancellous bone. As we age, the amount of cortical bone decreases, since bone breakdown exceeds bone formation. This loss of bone mass is known as osteopenia (mild bone loss) and osteoporosis (severe bone loss). To maintain bone strength, weight-bearing exercises should be performed, and one should take enough calcium and vitamin D on a daily basis. Factors that lead to greater bone loss include immobilization, smoking, and lack of exercise. The quality of one’s bone should be routinely monitored by a

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dual-energy x-ray absorptiometry (DEXA) scan, which is covered in Chapter 6.

WHAT DO BONES DO? Besides providing structure to the human body and protecting vital organs, bones can store minerals and produce blood cells. The skeleton is responsible for storing the minerals calcium and phosphorus, which are essential for the entire body’s function, specifically nerves and muscles. These minerals are regulated by specific hormones, such as parathyroid hormone and calcitonin, and involve multiple organs, including the kidneys, intestine, and liver. When the body’s supply of these minerals is low, osteoclasts are called upon to break down bone and release these minerals. However, if too much calcium or phosphorus is removed from bone, it can weaken the bone and lead to fractures in the bone. These disturbances in calcium and phosphorus metabolism can be due to medical conditions, such as hyperparathyroidism and renal osteodystrophy. The change in mineral metabolism may also be a result of genetic conditions, such as rickets or Albright hereditary osteodystrophy. Bone also contains bone marrow, which is responsible for producing red and white blood cells. Red blood cells make up our blood, and the bone marrow in our body produces approximately 500 billion red blood cells per day! White blood cells, or lymphocytes, are components of our immune system, which is important for fighting infections. Bones that have a rich supply of bone marrow, such as the iliac wing, are often the site where bone marrow transplants are taken, as well as bone graft in orthopedics.

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WHAT HAPPENS WHEN A BONE BREAKS? Since bone is a living tissue, when a bone breaks, it repairs itself. The repair process begins with osteoblasts that rapidly produce osteoid to fill in the void. The bone that is formed is mechanically weak and is composed of disorganized collagen fibers called woven bone, which describes the orientation of the collagen. Over time, the woven bone is replaced by stronger lamellar bone, which has parallel alignment of collagen into sheets. The remodeling and bone healing process takes an average of 6 weeks to 3 months.

WHAT IS MUSCLE MADE OF? Muscle is composed of filaments of actin (thin) and myosin (thick) that slide toward one another to contract a muscle (Figure 4-2). These actin and myosin filaments are bundled together to form a unit called a sarcomere. Multiple sarcomeres are bound together in a myofibril, or muscle fiber, and are covered with endomysium. These muscle fibers are then bundled together to form a fascicle covered with perimysium. These fascicles are finally grouped together within a muscle and are covered by epimysium. This bundle-within-a-bundle system is the muscle that we grossly see in surgery.

WHAT ARE THE DIFFERENT TYPES OF MUSCLES? There are 3 different types of muscles. Cardiac muscle is only in the heart. Smooth muscle lines the walls of most of the internal organs, such as the stomach, bladder,

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Figure 4-2. Cross section of muscle (eg, start with actin/myosin, sarcomere, and myofibril).

esophagus, intestines, and blood vessels. This muscle is not under voluntary control. Skeletal muscle is the type of muscle most commonly involved in orthopedics. You have control over skeletal muscle, unlike smooth muscle, and it is anchored to bone by tendons. Muscles are responsible for maintaining one’s posture, moving one’s body, and performing most activities of daily living. There are 2 types of skeletal muscle: slow and fast twitch. Slow-twitch muscle, or Type I skeletal muscle, is red in color because it has a large number of small blood vessels (capillaries) and contains high levels of myoglobin, which is a protein that binds iron and oxygen in muscle. This muscle is rich in energy-producing organelles (mitochondria) and it has a higher oxygen-carrying capacity. Because of this, slow-twitch muscles can sustain

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activity for longer periods of time. This is the type of muscle responsible for running marathons. Fast-twitch muscle, or Type II skeletal muscle, is the muscle responsible for sprinting. These muscles contract very powerfully and quickly, but this activity cannot be sustained for long periods of time. These muscles are white in color because there is less myoglobin and mitochondria. This muscle produces fast bursts of activity through anaerobic metabolism, where oxygen is not required. Fast-twitch muscles fatigue easily, to the point where muscle contraction can become painful.

Chapter 5

Skin and Bones Now that we have information about the bones, muscles, joints, and biology of the human body, it’s time to perform a physical exam to determine what can go wrong with the body.

PHYSICAL EXAM— MOTOR, SENSORY, AND VASCULAR When examining a patient, there are 3 important areas to test: motor function (how the muscles work), sensation (what the patient feels), and vascular status (the blood supply). Each part is necessary for limb function. By testing all 3 areas, doctors can determine what

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is wrong with a limb and have a better understanding on how to approach the problem.

Upper Extremity Motor In the upper extremity, there are many muscles. However, the most commonly tested muscles in the upper arm are the biceps (flex the elbow like Popeye the Sailorman) and triceps (extend the elbow). In the lower arm, larger muscle groups may be tested, such as the wrist flexors (bend wrist forward), wrist extensors (bend wrist back), supinators (show the palms), and pronators (cover the palms). Doctors may want to test specific nerves around the wrist by testing the posterior interosseous nerve (a branch of the radial nerve, by extending the fingers off of a flat surface), the anterior interosseous nerve (a branch of the median nerve, by bending the tip of the thumb), and the ulnar nerve (by spreading or crossing the fingers to activate the hand intrinsics).

Sensory Sensation in the upper extremity is often tested by the peripheral nerves, or the nerves outside of the spinal cord. The top of the shoulder is innervated, or supplied, by the supraclavicular nerve, and the side of the shoulder is innervated by the axillary nerve. For the palm side of the forearm, the area toward the thumb is innervated by the musculocutaneous nerve (specifically the lateral antebrachial cutaneous nerve), and the area toward the pinkie finger is innervated by the medial antebrachial cutaneous nerve. The back of the forearm and hand are mostly innervated by the radial nerve. For the front of the hand, the thumb, index, and middle fingers are mostly innervated by the median nerve, and the ring and pinkie fingers are mostly innervated by the ulnar nerve (Figure 5-1).

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A

B Figure 5-1. (A) Peripheral nerve. (B) Dermatome sensory distribution. (Reprinted with permission from Rihn JA, Harris EB. Musculoskeletal Examination of the Spine: Making the Complex Simple. Thorofare, NJ: SLACK Incorporated; 2011.)

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Vascular The blood supply to the upper extremity can be tested by palpation, or by touching, in 4 main areas. The axillary artery can be felt under the armpit, the brachial artery can be felt right below the elbow crease, the radial artery can be felt on the thumb side of the wrist, and the ulnar artery can be felt on the pinkie side of the wrist.

Lower Extremity Motor In the lower extremity, the most commonly tested muscles in the upper leg are the quadriceps (extend the knee) and hamstrings (flex the knee). The main muscle responsible for bringing the leg to the trunk, or hip flexion, is the iliopsoas. The tibialis anterior is the main muscle responsible for bringing the foot up (dorsiflexion), and the gastrocnemius-soleus complex is the muscle group most responsible for bringing the foot down (plantarflexion). The extensor hallucis longus is responsible for bringing the great toe up, and the flexor hallucis longus is responsible for bringing the great toe down.

Sensory The peripheral nerves responsible for sensation in the lower extremity include the posterior femoral cutaneous nerve for the back of the thigh, the anterior femoral cutaneous nerve for the front of the thigh, and the lateral femoral cutaneous nerve for the outside of the thigh. The middle of the thigh is innervated by the ilioinguinal and obturator nerves. The middle part of the shin is innervated by the saphenous nerve, the lateral shin is innervated by the common peroneal nerve, and the calf is mostly innervated by the sural nerve. The outside of the ankle, top of the foot, and the tops of the toes are mostly innervated by the superficial peroneal nerve, except for

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the side of the 5th toe (which is innervated by the sural nerve) and the webspace between the 1st and 2nd toe (which is innervated by the deep peroneal nerve). The flat part of the foot, or the plantar surface, is innervated by the tibial nerve (see Figure 5-1).

Vascular Similar to the upper extremity, the blood supply to the lower extremity can be palpated in 4 main areas. The first area is the groin, where the femoral artery is found. The second area is behind the knee, where the popliteal artery lies. The third area is the inside part of the ankle, where the posterior tibial artery is found. The fourth area is on top of the foot, where the dorsalis pedis artery is found.

Spine The physical exam of the spine builds on the exams of the upper and lower extremities. The motor and vascular exams of the upper extremities apply to the neck exam, and the motor and vascular exams of the lower extremities apply to the lumbar spine exam. The difference lies in the sensory exam. In the extremities, peripheral nerves are tested on exam. For the spine, dermatomes are tested. A dermatome is an area of skin that is innervated by a single spinal nerve. A diagram of dermatomes, found in Figure 5-1, demonstrates that each area of the body has a certain nerve responsible for feeling in that area. Thus, if a patient has decreased feeling in the dermatome distribution, it may be attributed to a problem in the spine. For example, a patient with numbness from the top of the shoulder down to the thumb may have C6 radiculopathy. A patient with numbness from the middle of the thigh, down the middle of the knee, and into the front of the shin may have a problem with L4.

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PHYSICAL EXAM—SPECIFIC AREAS Many of the body’s problems can be diagnosed by touching the patient and determining what hurts by performing certain maneuvers. There are many different tests that can be conducted, but this section highlights some specialized physical exam tests in specific areas of the musculoskeletal system, including the shoulder, hand/wrist, hip, knee, and foot/ankle.

Shoulder The main physical exam findings for the shoulder include testing for rotator cuff tears, impingement, biceps subluxation, and labral tears. The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) are the most commonly injured muscles in the shoulder. To test for damage to the most commonly injured muscle, the supraspinatus, 2 tests can be performed. The first is the empty can test, where a patient pretends to hold a can, forward flexes the shoulder to 90 degrees, abducts the arms 45 degrees, and internally rotates the arms as if emptying the can. If a patient feels pain or exhibits unilateral weakness when resisting a downward force, there is a high likelihood that the patient has supraspinatus pathology. The drop arm test is positive when the shoulders are abducted and a patient does not have the muscle capacity to slowly lower his or her arms. External rotation of the shoulder with the elbows bent to 90 degrees mainly tests the infraspinatus and somewhat tests the teres minor, while internal rotation of the shoulder with the elbows bent to 90 degrees tests the subscapularis. The subscapularis can also be tested by the lift-off test, where the arm is placed behind the back and the patient is asked to lift the arm up, and the belly press test, where the arm is placed on the patient’s belly and the patient is asked to push against

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the belly. Pain with either of these maneuvers is indicative of subscapularis pathology. Rotator cuff impingement can be tested using Neer’s test (where the scapula is stabilized, the arm is internally rotated, and the arm is flexed forward) or by Hawkins’ test (where the shoulder and elbow are flexed to 90 degrees and the shoulder is internally rotated). Pain with either of these maneuvers is indicative of rotator cuff impingement on the acromion. Biceps tendinitis or subluxation can be elicited with 2 special maneuvers. Speed’s test is performed where a patient resists downward motion when the shoulder is forward flexed 90 degrees, the elbow is extended, and the arm is supinated. Yergason’s test is performed when the arm is placed by the patient’s side, the elbow is flexed 90 degrees, and the patient supinates his or her forearm while resisting external rotation of the shoulder. Simultaneous palpation of the biceps groove at the top of the shoulder should produce pain or a “pop” if the biceps tendon is subluxing. Tearing of the labrum, or the soft tissue that keeps the ball and socket of the shoulder in place, most commonly occurs in the superior labrum from anterior to posterior; this type of tear is referred to as a SLAP tear. The O’Brien test is the most well-known test, where the shoulder is forward flexed 90 degrees and adducted 15 degrees, and the forearm is fully pronated or supinated. Pain that occurs with a downward force for either maneuver may indicate a labral tear. The Clancy test also evaluates for SLAP lesions with the same arm positioning as the O’Brien test (forward flexed and adducted shoulder). However, a posterior force is applied and the presence of pain is associated with labral tears.

Hand/Wrist For the hand and wrist, the most common disease is carpal tunnel syndrome. Phalen’s test is used to test for

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carpal tunnel syndrome, where the wrists are flexed to 90 degrees and the back of the hands are touched against one another. This position is held for up to 1 minute, and the presence of pain and/or numbness indicates carpal tunnel syndrome, as this maneuver compresses the carpal tunnel. Tinel’s sign is elicited when there is numbness or tingling when the median nerve inside the carpal tunnel is tapped either with the examiner’s fingers or a reflex hammer. If a patient presents with wrist pain on the thumb side of the hand, the patient may have de Quervain’s disease. This is tested using Finkelstein’s test, where the thumb is placed within a closed fist, and the wrist is moved toward the pinkie finger side of the hand (ulnar deviation). If pain occurs on the thumb side of the wrist, this is indicative that the 1st compartment of the hand may have pathology. To test for ulnar nerve function, the muscle adductor pollicis may be tested. A patient can be asked to pinch a piece of paper between his or her thumb and index finger. A patient without problems can hold onto the piece of paper. A patient with problems will only be able to hold onto the paper if he or she bends his or her thumb at the furthest joint (the interphalangeal joint). This is Froment’s sign. Scaphoid fractures are often diagnosed when there is tenderness in the anatomical snuffbox of the hand, or the area on the back of the hand where people use to sniff powered tobacco or snuff. The triangular area is created at the intersection of the extensor pollicis longus and the extensor pollicis brevis/abductor pollicis longus. The blood supply to the hand can be tested with Allen’s test. The radial and ulnar arteries are the 2 main vessels that supply blood to the hand. Initially, pressure is applied to both the radial (thumb side) and ulnar (pinkie finger side) arteries at the wrist with the patient’s fist clenched. The hand should be whitened at this point.

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Slowly, pressure is released off the radial artery while pressure is still maintained over the ulnar artery. Pink flow should return to the entire hand (especially the pinkie finger) if the radial artery has no problem. The test can be repeated to assess ulnar artery function when pressure is released from the ulnar artery and pressure is maintained on the radial artery. Pink flow should return to the entire hand (especially the thumb) if the ulnar artery has no problem.

Hip The exam of the hip is focused on the pathology around the hip. Patients who present with groin pain often have hip pathology, while patients who have buttock pain around the hip have back pathology. To test for hip pathology, one can log-roll the leg, or externally and internally rotate the leg with it flat on the examining table. If no pain is elicited in the groin, then it is unlikely that a hip problem is present. The specialized tests for the hip examine the musculature that surrounds the hip. The main motions of the hip that are tested include hip abduction and hip flexion. To test the hip abductors, a patient can be placed on his or her side and the leg being tested should be elevated off the bed. Strength of the hip abductors can be tested by placing a downward force on the leg while in the air. Another way to test hip abductor strength is by performing a Trendelenburg test. A patient is asked to stand on the affected leg, and if the gluteus medius muscle is weak, then the body will fall to the opposite side. The pelvis is uneven and drops to the unaffected side to reduce the load on the affected side by decreasing the lever arm. To test for a contracture of the hip flexors, the Thomas test can be performed. A patient is placed supine on the table. One leg is flexed so that the patient is holding his or her leg against his or her chest. If the opposite leg is lying flat on the table, then the hip flexors are not tight.

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However, if the hip flexors are tight, the pelvis will tilt up and the patient’s knee will slightly flex. Finally, the Ober test is performed to elicit a tensor fascia contracture. For this test, a patient is placed on his or her side with the unaffected leg on the table. The affected knee is flexed, the leg is abducted, and the hip is extended. The affected leg is then lowered into adduction, and if adductor range of motion is limited, then there is a tensor fascia contracture.

Knee There are many exams for the knee to test for common injuries. The anterior cruciate ligament (ACL) can be tested by performing an anterior drawer test, where the knee is bent to 90 degrees and an anterior force is placed on the tibia, or Lachman’s test, where the knee is bent to 10 to 25 degrees and an anterior force is placed on the tibia. If the ACL is disrupted, the tibia will translate anteriorly in comparison to the femur, and the Lachman’s test is a more sensitive test than the anterior drawer. A pivot shift test can also be performed to test the ACL. The patient is placed flat on a table (supine) and the hip is flexed 30 degrees. The tibia is internally rotated and the knee is flexed to 30 degrees while an inward (valgus) force is applied to the knee. There is likely a problem with the front (anterior) structures of the knee if the tibia reduces with the knee flexed. The posterior cruciate ligament (PCL) can be tested by performing a posterior drawer test, where the knee is bent to 90 degrees and a posterior force is placed on the tibia, or posterior sag test, where the knee is bent to 90 degrees and the knee is examined to see if the tibia sags posteriorly in relation to the femur. The side ligaments of the knee can be tested by putting various stresses to either side of the knee. When a valgus stress, or a stress from the outside of the leg, is placed on the knee, the medial collateral ligament (MCL)

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on the inside of the knee is being tested. When a varus stress, or a stress from the inside of the leg, is placed on the knee, the lateral collateral ligament (LCL) on the outside of the knee is being tested. There are multiple tests used to examine the meniscus, or the fibrocartilage shock absorber of the knee between the femur and the tibia. The simplest maneuver is to have the patient squat down on the affected leg to see if it elicits pain. More specialized tests include the Apley compression test, Apley distraction test, and McMurray test. For both Apley tests, the patient is placed on his or her stomach (prone). The affected knee is bent to 90 degrees and either pain is elicited when a downward force is placed on the tibia (Apley compression test) or pain is relieved when the tibia is pulled away from the femur (Apley distraction test). The McMurray test can be used to test for medial or lateral meniscal pathology. The patient is placed supine and the examiner places one hand above the knee and the other hand under the foot of the affected leg. To test for problems with the medial meniscus, the knee is flexed, a valgus stress is placed on the knee, and the leg is externally rotated while the leg is being extended. The lateral meniscus is tested using the opposite maneuver, where the knee is flexed, a varus stress is placed on the knee, and the leg is internally rotated when the leg is being extended. Finally, orthopedic patients are more likely to develop clots in their legs, or deep vein thrombosis (DVT), after surgical procedures due to immobility or intramedullary reaming. The first method to test for a DVT is by looking for a positive Homan’s sign. The patient’s leg is extended and the calf is stretched by dorsiflexing the foot, or bringing the foot up. If the patient feels pain, there is decreased pulses, or if there is increased swelling or paleness, this may indicate that the patient may have a DVT. Further testing using a Doppler ultrasound to make the final diagnosis may be helpful.

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Foot/Ankle There are also many specialized tests for the foot/ ankle. To diagnose most foot/ankle problems, touching or palpating for the area of tenderness is most likely to elicit the problem. To look for ligamentous laxity in the anterior ankle (anterior talofibular, deltoid, and anterior tibiofibular ligaments), an anterior drawer test can be performed. This test is similar to the test performed in the knee, but instead of moving the tibia in front of the femur, the foot is brought forward in relation to the tibia. This is done by stabilizing the tibia with one hand and pulling the calcaneus forward with the other hand. To test for injuries to the structures in the back of the lower leg, there are 2 main tests. The Achilles tendon can be tested using Thompson’s test. For this test, the patient is placed prone on a table with the knee extended and the feet hanging off the end of the table. In a patient with an intact Achilles tendon, the foot plantarflexes (goes downward) when the calf is squeezed. If the Achilles tendon is ruptured, then the foot does not move when the calf is squeezed. To further test if there is an Achilles tendon problem versus a problem with the gastrocnemius, the Silfverskiöld test can be performed. The patient dorsiflexes his or her foot with the knee extended and the knee flexed. If the patient has the same amount of dorsiflexion when the knee is extended or flexed, then the patient has Achilles tendon tightness. If the patient has better dorsiflexion when his or her knee is flexed, then the patient has gastrocnemius tightness. This occurs because the gastrocnemius muscles cross the back of the knee joint. By flexing the knee, the gastrocnemius muscles are relaxed and the ankle can move more easily if the tight muscles aren’t pulling on the foot.

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Finally, the squeeze compression test is performed to test if there is a syndesmosis injury in the leg, or the fibrous tissue that connects the tibia and fibula. The tibia and fibula are squeezed toward one another at the distal leg. The presence of pain increases suspicion for a syndesmosis injury, which may require additional fixation if the patient is undergoing surgical management.

GAIT Our gait, or how we walk, can be used to determine problems with our body. The gait cycle consists of 2 main phases: stance and swing. The stance phase, which consists of 60% of the cycle, is when one foot is on the ground, while the other foot is in swing phase, which consists of 40% of the cycle. Stance phase can be further broken down into the following activities: heel-strike, opposite toe-off, opposite heel-strike, and toe-off. In the beginning and end of the stance phase, both feet are on the ground, which is also called double-limb support. For the swing phase, there is foot clearance, tibia vertical, and heel-strike (Figure 5-2). During running, there are phases when neither foot is touching the ground. There are some common gait patterns that can be seen when there is a problem. An antalgic gait is a painful gait, where the stance phase of the affected limb is shorter than the other healthy limb. A Trendelenburg gait is when a patient lurches to the affected side when walking, because the hip abductors on the affected side cannot compensate for the weight of the pelvis dropping toward the opposite leg during the stance phase. This occurs in patients with weakened hip abductor muscles, such as polio and after hip surgery where the abductor muscles are dissected.

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Figure 5-2. Gait cycle. (Reprinted with permission from Hurwitz SR, Parekh SG. Musculoskeletal Examination of the Foot and Ankle: Making the Complex Simple. Thorofare, NJ: SLACK Incorporated; 2012.)

Chapter 6

Dry Bones There are many ways to see bones, joints, and soft tissue in orthopedics. Each imaging technique has a specific use for seeing something different. Often times, multiple different visualization methods are necessary to fully evaluate a condition, including fractures, spine conditions, and cancer.

X-RAYS X-rays are the most common and quickest imaging technique to take pictures of bones. An x-ray machine works by generating x-rays from an x-ray tube. X-rays then pass through the patient and are absorbed by dense material, like bone. The difference in absorption

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Figure 6-1. X-ray of the hip in a patient with a hip fracture.

is measured on a detector that is behind the patient and an image is formed. Bone and metal are white on x-ray. Soft tissue, on the other hand, does not absorb the x-ray as much and appears black on film. X-rays are very good at visualizing bone and conditions that affect bone, including fractures (Figure 6-1),

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arthritis, and bone tumors. X-rays can also look at metal, including orthopedic implants, bullets, and shrapnel. Further imaging is often needed to evaluate other conditions, but an x-ray can be used to rule out many conditions.

COMPUTED TOMOGRAPHY SCANS For a 3-dimensional view of the bones, a computed tomography (CT) scan can be used. Bone appears white on CT scan, while fat, water, and soft tissue appear in different shades of gray. Air appears black on CT scan. CT scans use x-rays to generate images, which exposes the patient to radiation, specifically ionizing radiation. If a patient has a fracture and has already gotten x-rays, CT scans are often done to get a much better look at fractures to determine if surgery needs to be done and how to perform surgery to best line up the bones. CT scans are especially useful for looking at fractures that occur around joints, or articular fractures, around the ankle, knee, hip, shoulder, elbow, and wrist. CT scans are also very useful for evaluating the small bones of the hand and foot and the large bones of the pelvis (especially acetabular fractures). For more life-like imaging of bone, 3-dimensional rendering can be done by digitally “removing” the soft tissue (Figure 6-2). Metal artifact correction can be done to “subtract” metal implants in the body so that surrounding bone and soft tissue can be more easily seen. Finally, if magnetic resonance imaging (MRI) cannot be performed (see next), a CT scan with contrast can be performed (eg, a CT myelogram to look at the spinal cord).

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Figure 6-2. CT scan of the shoulder with 3-dimensional rendering.

MAGNETIC RESONANCE IMAGING MRI can be used to see everything else surrounding the bones in the body, or to see soft tissue in the body. The benefit of using MRI is that no ionizing radiation is used, which makes it safe to use on pregnant women. The downside of MRI is that patients with pacemakers and patients with metal in their bodies can’t get MRIs. This is only true for patients with implants that have iron in it, including patients with shrapnel and brain aneurysm clips. On the other hand, if patients have an existing orthopedic implant, they should be able to get

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Figure 6-3. MRI of knee looking at a meniscus tear.

an MRI because those implants are made of titanium, cobalt-chromium, or stainless steel. Contrast dye is used in MRIs to look at blood vessels or to look at joints. For patients with bad kidneys, they may need to be pretreated with fluid and medication before getting a contrast MRI scan. For soft tissue, MRIs can be used to diagnose tendon and ligament tears, lumps and bumps within the soft tissue, meniscal injuries (Figure 6-3), and fluid in soft tissues and joints. For bone, an MRI can reveal a fracture that can’t be seen on x-ray, collapse of bone, bone bruising, and infection inside bone. MRIs are also used to evaluate specific orthopedic conditions, such as herniated discs in the spine and trapped nerves.

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ULTRASOUND Ultrasound (US) is great for looking at babies within the womb and at blood vessels, but has limited use in orthopedic imaging. However, US can be used to evaluate conditions that are close to the skin surface, such as ligament and tendon pathologies. US can also be used for injecting and removing fluid from collections of fluid (eg, from joints). US has also been used to diagnose developmental dysplasia of the hip in children and rotator cuff tears. In developmental dysplasia of the hip, US allows for direct imaging of the cartilage in the hip that cannot be seen on x-ray. US also allows for studying the hip while it is moving. For rotator cuff tears, US can be used to diagnose a tear, as well as monitoring surgical repairs.

ARTHROGRAM An arthrogram is a more detailed image of a joint, which is produced when dye is injected into a joint to provide contrast to the surrounding soft tissues. Images of the labrum can be seen in the shoulder and hip. An arthrogram is also a good imaging technique for looking at cysts and the joint capsule.

BONE SCAN A bone scan is a study where areas of high bone growth and death (turnover) are visualized. Small doses of a radioactive marker are injected into the body and collect in bone that has high turnover. Bone scans can be performed in multiple phases, which means images are taken at different points of time. Orthopedic conditions

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that are diagnosed by bone scan include bone tumors (especially cancer spread from other areas of the body), bone infection (osteomyelitis), fractures, and loosening of orthopedic implants. A word of caution: bone scans are sensitive, meaning they pick up many things on the image, but they are not very specific, meaning they may not be the best way to diagnose a condition. Bone scans are best at ruling out suspected problems. Another variation of the bone scan is the white blood cell (WBC) scan. This scan is also known as an indium or inflammatory scan. This scan looks for areas of infection or inflammation. To perform this scan, WBCs are removed from the patient’s blood and tagged with a substance that can be detected by a camera. The WBCs are returned into a patient 2 to 3 hours later, and the patient is scanned 6 to 24 hours later to find areas of concern.

POSITRON EMISSION TOMOGRAPHY SCAN The positron emission tomography (PET) scan is a type of imaging that measures the activity of cells by detecting a tagged molecule that is injected into the blood stream. Areas that have more activity light up brighter on PET scan. In orthopedics, PET can be used to identify tumor and determine muscle activity, especially from deeper muscles. PET can be combined with other imaging modalities (eg, MRI or CT scan) for better localization of metabolic activity. However, there is substantially more radiation when PET/CT scans are combined, in comparison to PET or CT scans alone.

Chapter 7

Bad to the Bone There are multiple diseases that affect the adult musculoskeletal system, but they can be generally categorized into traumatic, degenerative (arthritis), inflammatory, infectious, and cancerous. Musculoskeletal diseases in children will be covered in Chapter 8.

TRAUMA Trauma sustained by the body can result in breaks, sprains, and tears. The 2 most common areas of trauma in orthopedics are sustained when bones are broken, or fractured, or from sports injuries.

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Fractures Any bone in the body can be broken. Fractures can be treated conservatively, which means that no surgery is performed. Patients can be put into slings for the upper extremity (for clavicle or proximal humerus fractures) or braces, splints, or casts for the upper and lower extremities. These apparatuses hold the fracture in place as it’s healing. Some fractures, especially some fractures of the pelvis, may need no treatment. Other fractures require surgery. The fractures that often require operative treatment are fractures where the skin is cut (or open fractures), fractures where the bone is widely separated (displaced), and fractures that involve the joint, or articular, surface. Fractures that occur at the articular surface include the distal radius, the olecranon, the distal humerus, the dome of the acetabulum (socket of the hip), the head of the femur (ball of the hip), the distal femur, the tibial plateau, and the tibial plafond. Chapter 10 covers the different types of surgery in more depth. Once a fracture has occurred, the doctor may limit the weightbearing of the patient’s extremity (Table 7-1). Weightbearing as tolerated or full weightbearing means that the patient can place as much weight on the affected extremity as possible. This is commonly the weightbearing status after fixing a hip fracture. Partial weightbearing can have a percentage specified, and the patient can place a percentage of his or her weight on the affected extremity. Touch-down weightbearing or toe-touch weightbearing is true for the lower extremities, which means the toes may touch the ground when ambulating, but no more weight can be placed on the extremity. This results in a hopping motion when patients walk. Finally, patients are most commonly made nonweightbearing, or no weight is allowed on the affected extremity, after fixing a fracture. This lack of weightbearing is the time bone is allowed to heal.

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Table 7-1 Commonly Used Terms for Weightbearing Status Term Nonweightbearing Touch-down weightbearing Toe-touch weightbearing Partial weightbearing Full weightbearing Weightbearing as tolerated

Abbreviation NWB TDWB TTWB PWB FWB WBAT

Sports Injuries There are many sports injuries that athletes can sustain. The most common injuries in athletes affect the shoulder and knee. In the shoulder, athletes, such as pitchers, can sustain injuries that result from overuse. Patients can tear the tissue within the shoulder, or glenohumeral joint, such as a labral tear. The most common labral tear is the superior labrum from anterior to posterior (SLAP) tear that is often associated with anterior dislocations of the shoulder. Patients can also tear the muscles that help to stabilize the shoulder, specifically the rotator cuff muscles. Finally, the biceps tendon can be torn within the shoulder (origin) or at the elbow (insertion) (Figure 7-1). For the knee, sports injuries often occur by damaging the ligaments or cartilage. The anterior cruciate ligament (ACL) is the most commonly ruptured ligament; it is located in the middle of the knee and prevents the knee from sliding forward. It consists of 2 parts: the anteromedial (AM) and posterolateral (PL) bundles. Female athletes more commonly injure the ACL, along with basketball and soccer players. The posterior cruciate ligament (PCL) is located behind the ACL and

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Figure 7-1. Shoulder. The single arrow denotes a SLAP tear, and the three small arrows denote a rotator cuff tear.

can be ruptured during knee hyperextension. The PCL prevents the knee from sliding backward. The medial collateral ligament (MCL) is in the inside part of the knee, and the lateral collateral meniscus (LCL) is on the outside of the knee. Both can be torn individually, but they are more commonly torn in addition to the ACL or PCL (Figure 7-2).

INFLAMMATION Inflammation is a common culprit for many conditions in orthopedics. Any condition ending with “-itis” is often due to inflammation, including tendinitis (inflammation

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Figure 7-2. Knee labeled with ACL (AM and PL bundles), PCL, MCL, and LCL. (Reprinted with permission from Ranawat A, Kelly BT. Musculoskeletal Examination of the Hip and Knee: Making the Complex Simple. Thorofare, NJ: SLACK Incorporated; 2011.)

of tendon), bursitis (inflammation of bursa), synovitis (inflammation of the synovium), and myositis (inflammation of muscle). The many ligaments and tendons of the foot and ankle can become inflamed, and these are often diagnosed as foot or ankle sprains. Arthritis is one of the most common diseases treated in orthopedics and is covered in the next section.

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One of the most common inflammatory conditions in the foot is plantar fasciitis. This is a condition where the fascia, or tough fibrous band, on the bottom of the foot that creates the arch of the foot becomes inflamed. These patients have pain and stiffness at the bottom of their feet that is worse in the morning when taking the first step of the day. Patients are first treated conservatively with stretching and physical therapy. If these treatment options fail, then surgery to release the plantar fascia may be considered. In the hand, 2 common diseases that can result from inflammation are carpal tunnel and trigger finger. If the cause for carpal tunnel is a condition like rheumatoid arthritis, there can be inflammation in the carpal tunnel that compresses the median nerve. Treatment involves releasing the transverse carpal ligament, and sometimes the synovium overlying the median nerve is removed. For trigger finger, the tendon sheath over the tendon that bends a finger forward (flexor tendon) can get inflamed and cause the finger to get stuck, or to “trigger.” To treat trigger finger, an injection of cortisone can be given to reduce the inflammation. If injections do not help, then surgery to cut or remove part of the tendon sheath may be performed.

ARTHRITIS Arthritis is inflammation of the joints. Patients can present with pain around the joint, swelling, stiffness, warmth surrounding the joint, decreased mobility, and redness of the skin around the joint. There are 4 main types of arthritis that are commonly treated in orthopedics: osteoarthritis (OA), inflammatory arthritis, seronegative spondyloarthropathies, and crystal arthropathies.

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Figure 7-3. Osteoarthritis of the knee. (Reprinted with permission from Ranawat A, Kelly BT. Musculoskeletal Examination of the Hip and Knee: Making the Complex Simple. Thorofare, NJ: SLACK Incorporated; 2011.)

OA is the most common arthritis, and it is known as the “wear-and-tear” arthritis. It commonly affects older patients, and OA is characterized by a progressive loss of cartilage in joints. It is often found in the larger joints, including the knees (Figure 7-3), hips, and shoulders. It can also be found in the spine and is known as spinal stenosis. There are multiple causes of OA, which may result from infection, trauma, loss of blood supply to the bone (avascular necrosis), and hereditary, metabolic, developmental, and neurologic disorders. Treatment depends on the cause of OA, but conservative treatment with anti-inflammatory medications and injections is often tried first. Muscle strengthening with physical therapy and ambulating with an assistive walking device (eg, cane, walker, crutches) may help with activities of daily living. Once all conservative options are exhausted, surgery may be performed to replace the joint surface with metal parts.

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The most common inflammatory arthritis treated by orthopedic surgeons is rheumatoid arthritis (RA). RA is thought to be an autoimmune disease that activates antibodies (rheumatoid factor [RF]) that destroy cartilage. Multiple joints can be affected in RA, but the most commonly affected joints include the wrist and the closer (proximal) joints of the hand and feet. RA is treated by disease-modifying drugs, such as tumor necrosis factor and anti-interleukin-1 receptor antagonists, as antiinflammatory medications are not strong enough. Seronegative spondyloarthropathies is a collection of inflammatory diseases that affect the skeleton but these patients have negative RF. Ankylosing spondylitis is an inflammatory disease that mostly affects the spine and the joints that connect the spine to the pelvis (sacroiliac joints). These patients can also have inflammation where tendons and ligaments attach to bone (enthesitis) and inflammation of the uvea in the eye (uveitis). Psoriatic arthritis occurs with psoriasis, or the medical condition with skin lesions, detachment of the nail from the nail bed (onycholysis), and nail pitting. Psoriatic arthritis often involves the farthest (distal) joints of the hands, in comparison to RA. Other seronegative spondyloarthropathies that are associated with other medical conditions include reactive arthritis, which is triggered by a urinary or gastrointestinal infection, and enteropathic arthritis, which accompanies inflammatory bowel disease. Finally, crystal arthropathies are diseases that deposit microcrystals into the synovium of joints and cause synovitis. The 2 common crystal diseases include gout and pseudogout. Gout is a disease where monosodium urate crystals, or negatively birefringent needle-shaped crystals, are deposited into joints. Gout most commonly presents in the 1st toe and knee. This disease

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most commonly occurs in men and postmenopausal women, especially after eating meat and drinking alcohol. Pseudogout is a disease where calcium pyrophosphate dehydrate crystals are deposited into joints, which are positively birefringent rhomboid-shaped crystals. The knee is the most commonly affected joint.

INFECTION Infection in orthopedics can occur in the bone, the soft tissue, or in the joint. Osteomyelitis is an infection in the bone that is diagnosed by magnetic resonance imaging and is often treated by antibiotics. A collection of pus in the soft tissue is an abscess and may need to be treated by surgery to remove the pus. Finally, joint infections can be in native joints or in prosthetic joints. The most commonly infected joint is the knee, followed by the hip. Joint infections can occur in one of 3 ways: 1) direct colonization of the joint by either an injection or through surgery, 2) contact with an infected site, or 3) by spreading through the blood or lymph system. Common agents responsible for infections in native joints include Borrelia (Lyme disease) and Neisseria gonorrhoeae. Staphylococcus aureus and Staphylococcus epidermidis are the bacteria that are most commonly responsible for periprosthetic joint infections. Patients are more likely to get infected if they have a predisposing medical condition (eg, diabetes), have an immune-compromising disease (eg, cancer), or are on immunosuppressants (eg, chemotherapy agents, steroids). Patients who are older are also more likely to become infected.

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CANCER Cancer can affect any tissue in the body. Cancer can be divided into 2 main categories: benign, or cancer that doesn’t spread, and malignant, or cancer that spreads (metastasizes). Orthopedic oncology can be further divided into cancers that affect the bone, cartilage, fibrous tissue, immune system/bone marrow, or are of unknown origin. All cancers that end in “-sarcoma” are malignant. The most common cancer that affects bone are cancers that come from other parts of the body. Breast, lung, thyroid, kidney, and prostate cancers often metastasize to bone, and imaging of the bones may be the first way the primary cancer is diagnosed. Common benign bone tumors include osteoid osteoma, osteoblastoma, and osteoma. Common malignant bone tumors include osteosarcoma, which can be classic, parosteal, or periosteal. There is only one main malignant cartilage tumor, which is chondrosarcoma. However, there are multiple benign cartilaginous tumors, including osteochondroma, enchondroma, chondroblastoma, chondromyxoid fibroma, and periosteal chondroma. Fibrous tissue can also cause both benign and malignant cancers. Benign fibrous tissue cancers include nonossifying fibroma, desmoplastic fibroma, fibrous dysplasia, and ossifying fibroma. Malignant fibrous tissue cancers include fibrosarcoma and malignant fibrous histiocytoma. The 2 most common cancers that arise from cells of the immune system or bone marrow are Ewing’s sarcoma and multiple myeloma, respectively. These are both considered malignant tumors. Benign tumors that arise from the immune system include eosinophilic granuloma and Hand-Schüller-Christian and LettererSiwe diseases.

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Finally, common malignant orthopedic tumors that do not fit a specific origin include chordoma and adamantinoma. Common benign orthopedic tumors include giant cell tumor and cysts, including aneurysmal and unicameral bone cysts.

Chapter 8

Little Bones Similar to adults, multiple diseases affect the musculoskeletal system in children. Degeneration is not common in children, although genetic and inflammatory conditions are more common. Younger patients may also present with different symptoms than adults. Each section that follows goes into greater detail about different disease entities commonly associated with children.

TRAUMA Broken bones, or fractures, in children are the most common orthopedic reason for going to an emergency room. Fractures account for 15% of all injuries in children. Boys are more likely to suffer a broken bone,

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and older children are more likely to break their bones. Fractures in children differ from fractures in adults in that children heal faster (due to a thicker covering on the bone, or a thicker periosteum) and their bones are still growing. This is beneficial because more fractures can be treated with conservative management, such as casting and splinting. However, if the fracture affects the growth plate, this may stunt the amount of growth that can occur in a particular bone or the bone can grow abnormally.

Fracture Types Since the periosteum of bone is thicker in children, bones are more likely to bend rather than break during an injury. These incomplete fractures present as either greenstick or buckle fractures. Greenstick fractures often involve the diaphyseal region, or midportion, of long bones, where there is a force on one side of the bone that causes partial fracture on one side and a bend in the bone on the other side (Figure 8-1). The other incomplete fracture type is commonly called a buckle fracture, but it is also known as a torus, or the base of a pillar. These occur in the metaphyseal region, or almost at the end of the bone, where the bone is compressed and the cortex of the bone is acutely angulated (Figure 8-2).

Fracture Classification The most common fracture classification in children is the Salter-Harris classification. The types range from I to V, with I being the least severe and V being the most severe. For type I, the fracture occurs through the growth plate. Type II fractures pass through the growth plate but then exit through the metaphysis, or away from the end of the bone. Type III fractures pass through the growth plate and exit through the epiphysis, or through the bone that makes up the joint. Type IV fractures are a combination of type II and III fractures, where the fracture goes

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Figure 8-1. Greenstick fracture (radial shaft).

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Figure 8-2. Distal radius buckle fracture.

through the growth plate and exits out the metaphysis and epiphysis. Finally, type V fractures are a crush injury to the growth plate that can completely stop growth. It is often difficult to see type I and V fractures on x-rays. Type II fractures are the most common.

Common Fractures There are some fracture patterns that are common to children. Distal radius fractures, on the other hand, are common to both children and adults. The mechanism of injury is often a fall on an outstretched hand. These

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Figure 8-3. Posterior sail sign in supracondylar humerus fractures.

fractures may need to be manipulated back in place, but in children, these fractures can often be treated in a cast. Long arm casting is the traditional first method of treatment, although the length of the cast is dependent on the nature of the fracture. In the upper extremity, supercondylar humerus fractures are also very common. The mechanism is often a fall onto a hyperextended or straightened elbow. The x-ray of these patients may show no bony disruption, but there may be the presence of a darkening shadow from the appearance of a posterior fat pad, otherwise known as a posterior sail sign (Figure 8-3). This sign appears when there is posterior cortical humeral disruption, and these patients should be treated in a long arm cast. If

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there is significant displacement of this fracture, surgical treatment with closed reduction and percutaneous pinning should be performed. If the fracture cannot be reduced in a closed manner, an incision may be required to manually reduce the fracture fragments that can be subsequently pinned. In the lower extremity, tibia and fibula fractures can occur with falling and twisting injuries. These fractures may require reduction if the bones are angulated more than 15 degrees, and these fractures are often treated in a long leg cast or splint. If a spiral fracture of the tibia occurs in a child less than 2 years old, the fracture is called a toddler’s fracture.

Child Abuse When a child presents with a fracture, there must be a high index of suspicion for child abuse. This is especially true if the patient has concomitant bruising, if the fractures are in various stages of healing, if there are bilateral extremity fractures, and if there are complex skull fractures. Abuse most commonly occurs in children under 1 year old, premature infants, first-born children, stepchildren, and children with disabilities. The most common locations of fractures that are suspicious for abuse include the tibia, femur, and humerus. Fractures that commonly occur in nonaccidental trauma are found at the corners of the distal femur and proximal tibia. Appropriately, these fractures are called corner fractures, and these fractures are fragmentation of bone where the loose pieces are visualized by x-ray (Figure 8-4). Femur fractures that occur in patients under 1 year old are suspicious, as are transverse tibia fractures. If these fractures are found, patients should undergo a full skeletal survey by x-ray to find if there are other fractures present.

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Figure 8-4. Corner fractures.

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CONGENITAL AND HEREDITARY DISORDERS There are many textbooks dedicated to congenital diseases in children that present with orthopedic conditions. This section will highlight the most common conditions found in children. In the spine, pediatric patients may have a condition called scoliosis, or when there is an abnormal curvature to the spine. Scoliosis may be congenital, or present at birth, with vertebral anomalies in conditions such as VATER syndrome (vertebral, anal, trachea, esophagus, and renal syndrome). Scoliosis can also occur as a result of neuromuscular conditions, such as cerebral palsy, spina bifida, or spinal atrophy. The scoliosis curves in these patients are more likely to start at an earlier age and progress faster, which makes bracing less effective. Scoliosis most commonly occurs without a known cause and is called idiopathic scoliosis. This type of scoliosis is categorized by the age of the patient at the time of presentation and includes infantile (