Anatomy Extravaganza of the Upper Extremity 4.0 contact hours or .4 AOTA CEUs Editor: Walter B. Greene, MD Illustrated by: Frank H. Netter, MD EHT Instructors: Nancy Falkenstein, OTR/L, CHT and Susan Weiss OTR/L, CHT Click on SECTIONS (below) to View your Course: Description: This course is in written format. This is a mixed level learning course teaching the clinician an abundance of upper extremity anatomy details. View amazing Netter photographs and learn anatomy biomechanics, physical exam as well as a wide array of various disorders from the shoulder to the hand. The detailed photographs in this book will increase your understanding of fractures, bone anatomy, nerve compressions, the brachial plexus, muscular structures and more. You can print the chapters out and have a wonderful anatomy reference booklet to use in the clinic. This jammed packed anatomy course is priced right making it a fantastic way to earn CEU’s for less. Used with permission from Elsevier/Mosby.

Objectives:

*Review the pertinent basic science of the more common clinical disorders of the shoulder, elbow wrist and hand. *Review rotator cuff pathology and treatment regimes *Introduce shoulder arthritis and intervention techniques *Review nerve entrapment syndromes and brachial plexus injuries *Learn about fractures of the proximal humerus, clavicle and scapula *Review the nerves passing the elbow and the various nerve entrapments *Learn about elbow arthritis, lateral epicondylitis, medial epicondylitis, and fractures about the elbow *Introduce hand anatomy and biomechanics *Review physical examination of the hand *Introduce the student to osteoarthritis of the hand, Kienbocks’s disease, tendonitis, *Dupuytren’s disease, ganglia, nerve entrapments, wounds, tendon injuries and *fractures *Introduce to pediatric conditions and congenital anomalies

Sections: Click on the link(s) to view your course **Netter: Shoulder and Arm **Netter: Elbow and Forearm **Netter: Hand and Wrist

Chapter 14

ANATOMY AND BIOMECHANICSThe shoulder girdle includes three bones

(the scapula, clavicle, and humerus) and threejoints (the glenohumeral, acromioclavicular[AC], and sternoclavicular [SC] joints). Thescapulothoracic articulation is also consideredpart of the shoulder girdle. For every 2° ofglenohumeral motion, approximately 1° ofscapulothoracic motion occurs. The AC andSC joints also participate in this scapulo-humeral rhythm. As a result of this coordinatedmovement, the shoulder has a greater range ofmotion than any other joint in the body.

The scapula is a triangular, flat bone thatis surrounded by muscle (Figures 14-1 and 14-2). Its curved coracoid process projects an-teriorly from the superior border and is thesite of origin for the coracobrachialis andthe short head of the biceps muscle. Theother notable scapular prominence is theacromion, a spinelike process on the poste-rior aspect. The coracoacromial ligamentstabilizes the humeral head in the superior di-rection. The two coracoclavicular ligamentsprevent the clavicle from riding superiorly.The clavicle is an S-shaped tubular bone thatarticulates with the acromion laterally and themanubrium medially.

The proximal end of the humerus includesthe humeral head, the greater and lessertuberosities, and the humeral neck. The headof the humerus is retroverted, or posteriorlyangled, approximately 30° to match the ante-rior position of the scapula as it rests on thethoracic cavity. The pear-shaped glenoidfossa articulates with the humerus in a neutralor slightly retroverted position. The glenoidlabrum is a rim of fibrocartilaginous tissue thatincreases the surface area of the glenoid fossaand the stability of the shoulder (Figure 14-3).

The deltoid is a large, powerful musclewhose primary function is shoulder abduc-

tion. The anterior half of the deltoid elevates(flexes) the shoulder, and the posterior halfprovides extension. Underneath the deltoidare the four rotator cuff muscles: the sub-scapularis, located anteriorly; the supraspina-tus, located superiorly; and the infraspinatusand teres minor muscles, located posteriorly.The deltoid provides most of the power inshoulder motion, whereas the rotator cuffmuscles act as a force couple to fine-tune andenhance the efficiency and stability of shoul-der motion by compressing, depressing, andthus maintaining the humeral head in theglenoid fossa. Other important shouldermuscles include the trapezius, the latissimusdorsi, the serratus anterior, and the pectoralismajor.

The subclavian artery passes under the clav-icle and continues as the axillary artery as it tra-verses the anterior aspect of the shoulderjoint. Anastomoses of branches of the axillaryartery provide important collateral circulationto the upper extremity (Figure 14-4). The mainblood supply to the humeral head is the ante-rior humeral circumflex artery. The nervesabout the shoulder include the brachial plexusand its terminal branches, the sympatheticnerves, the supraclavicular nerves, and cranialnerve XI.

Important posterior landmarks include thequadrangular space and the triangular inter-val (Figure 14-5). The quadrangular space isbordered by the long head of the triceps, thesurgical neck of the humerus, the inferior bor-der of the scapula, and the teres major. Theaxillary nerve and the posterior humeralcircumflex artery fill this space. The triangularinterval houses the radial nerve and thedeep brachial artery. Its borders are the teresmajor superiorly, the long head of the tricepsmedially, and the lateral head of the tricepslaterally.

The purpose of this chapter is to review the pertinent basic science of the morecommon clinical disorders of the shoulder.

284

The Shoulder and Arm

285

Supraspinatus tendon (cut)

Coracohumeral ligament

Greater tubercle andLesser tubercle

of humerus

Transverse humeral ligament

Intertubercular tendon sheath(communicates with synovial cavity)

Subscapularis tendon (cut)

Biceps brachii tendon (long head)

Shoulder joint, anterior view

Acromion Coracoid process Clavicle (cut)

Anatomic neck

Greater tubercle

Lesser tubercle

Surgical neck

Deltoid tuberosity

Intertubercularsulcus

Crest ofgreater tubercle

Crest oflesser tubercle

Deltoid muscle

ScapulaHumerus

Head ofhumerus

Biceps brachii muscle(long head)

Supraspinatus muscle

Subscapularis muscle

Coracobrachialis muscleand

Biceps brachii muscle(short head)

Subscapularismuscle

Pectoralis major muscle

Latissimus dorsi muscle

Teres major muscle

Deltoid muscle

Coracobrachialis muscle

Superior border

Superior angle

Suprascapular notch

Neck

Medial border

Subscapular fossa

Lateral border

Inferior angle

Glenoid

Trapezius muscle

Pectoralis minor muscle

Omohyoid muscle

Serratusanteriormuscle

Tricepsbrachiimuscle

(long head)

Muscle attachments

Origins

Insertions

Brachialis muscle

Clavicle

Trapezoidligament

Conoidligament

Coraco-clavicularligament

Superior transversescapular ligament andsuprascapular notch

Coracoid process

Communications ofsubtendinousbursa of subscapularis

Broken line indicatesposition of subtendinousbursa of subscapularis

Acromioclavicular joint capsule(incorporating acromioclavicular ligament)

Acromion

Coracoacromial ligament

Capsularligaments

Figure 14-1: Anterior View Scapula and Proximal Humerus

Chapter 14

PHYSICAL EXAMINATIONBegin the physical examination with an in-

spection of the patient’s overall posture andalignment of the shoulder. Look for swellingand ecchymosis, which may indicate recenttrauma. Note areas of muscle atrophy sugges-tive of nerve dysfunction. Injury to cranial nerveXI results in atrophy of the trapezius muscle,which is seen superiorly as a reduced neck-to-shoulder contour. Supraspinatus nerve dys-function causes loss of the normal posteriorshoulder contour and prominence of thescapular spine and acromion.

Next, palpate subcutaneous landmarks todetect deformity or tenderness. For example,with an AC separation, the distal end of theclavicle is prominent. Start at the sternoclavic-ular joint, and proceed laterally along the clav-icle to the acromioclavicular joint. Proceed tothe lateral edge of the acromion and thegreater tuberosity of the proximal humerus.Also, palpate the long head of the biceps inthe bicipital groove of the proximal humerusto detect subluxation or tenderness.

Shoulder range of motion is assessed infour planes (Figure 14-6). The zero starting

286

Suprascapular notch

Superior border

Superior angle

Supraspinous fossa

Spine

Neck

Infraspinous fossa

Medial border

Lateral border

Inferior angle

Clavicle (cut)

Coracoid process

Acromion

Acromial angle

Spinoglenoid notchconnecting supraspinousand infraspinous fossae

Greater tubercle

Head of humerus

Anatomic neck

Surgical neck

Deltoid tuberosity

Radial groove

Brachialis muscle

Deltoid muscle

Deltoid muscle

Supraspinatus muscle

Infraspinatus muscle

Teres minor muscle

Triceps brachii muscle(lateral head)

Humerus

Scapula

TrapeziusmuscleSupraspinatus

muscle

Levatorscapulae

muscle

Rhomboidminor

muscle

Rhomboidmajor

muscle

Infraspinatusmuscle

Latissimus dorsimuscle (smallslip of origin)

Teres majormuscle

Teres minormuscle

Tricepsbrachiimuscle(long head)

Muscle attachments

Origins

Insertions

Figure 14-2: Posterior View Scapula and Proximal Humerus

The Shoulder and Arm

287

Figure 14-4: Axillary and Brachial Arteries

Figure 14-3: Shoulder Joint Opened (lateral view)

Coracoacromial ligamentAcromion

Supraspinatus tendon(fused to capsule)

Subdeltoid bursa

Infraspinatus tendon(fused to capsule)

Glenoid cavity (cartilage)

Teres minor tendon(fused to capsule)

Insertion of synovium(enlarged for depiction)

Coracoid process

Coracohumeral ligament

Biceps brachii tendon (long head)

Superior glenohumeral ligament

Subscapularis tendon(fused to capsule)

Middle glenohumeralligament

Inferior glenohumeralligament

Brachial artery

Axillary artery

Clavicular branch

Pectoral branch

Superior thoracicartery

Thoracoacromialartery

Lateral thoracicartery

Subscapular artery

Circumflex scapularartery

Thoracodorsalartery

Acromial branch

Deltoid branch

Anterior circumflex humeral artery

Posterior circumflex humeral artery

Deep artery of arm

Middle collateral artery

Radial collateral artery

Level of lower marginof teres major muscleis landmark for namechange from axillaryto brachial artery

Chapter 14

288

Infraspinatus and

Axillary nerve

Superior lateral cutaneousnerve of arm

Deep artery of arm

Radial nerve

Middle collateral artery

Radial collateral artery

Inferior lateral cutaneousnerve of arm Lateral intermuscularseptum

Lateral epicondyleof humerus

Capsule of shoulder joint

Supraspinatus tendon

Teres minor tendons (cut)

Posterior circumflexhumeral artery

Nerve to anconeusand lateral head oftriceps brachii muscle

Posterior cutaneousnerve of forearm

Long head oftriceps brachii muscle

Lateral head of tricepsbrachii muscle (cut)

Medial head of tricepsbrachii muscle

Medial epicondyleof humerus

Ulnar nerve

Olecranon of ulna

Anconeus muscleDeep layer

Teresmajor

muscle

Superficial layer Acromion

Supraspinatus muscle

Greater tubercle of humerus

Infraspinatus muscle

Teres minor muscle

Deltoid muscle (cut and reflected)

Triceps brachii muscle Long head Lateral head Tendon

Brachioradialis muscle

Extensor carpiradialis longus muscle

Extensor carpiradialis brevis muscle

Teres major muscle

Posterior cutaneousnerve of arm

(from radial nerve)

Medial intermuscular septum

Ulnar nerve

Medial epicondyle of humerus

Olecranon of ulna

Flexor carpi ulnaris muscle

Anconeus muscle

Extensor carpi ulnaris musclePosterior cutaneous

nerve of forearm(from radial nerve)

Extensor digitorum muscle

Superior lateral cutaneous nerve of arm(from axillary nerve)

Axillary nerve and posteriorcircumflex humeral artery

Figure 14-5: Posterior View of Shoulder and Arm

fifteen

Edward D. Wang, MDLawrence C. Hurst, MD

Elbow andForearm

Figure 15-1: Bones of Right Elbow Joint

Chapter 15

ANATOMYThe elbow is a functional link for position-

ing the hand in space, a fulcrum for the fore-arm lever, and a load-carrying joint. As such, itrequires a combination of mobility and stabil-ity. The three articulations of the elbow pro-vide flexion and extension, as well as forearmrotation (Figure 15-1). Control and stability offlexion and extension are provided primarilythrough the ulnohumeral (trochlea and ole-cranon) articulation and secondarily throughthe radiohumeral (capitellum and radial head)articulation. The trochlea is shaped like a

308

Humerus Humerus

Lateral

supracondylar ridge

Radial fossa

Lateral epicondyle

Capitulum

Head

Neck

Tuberosity

Radius Ulna

Tuberosity

Radial notch of ulna

Coronoidprocess

Trochlea

Medial epicondyle

Coronoidfossa

Medialsupracondylar ridge

Lateral epicondyle

Olecranon

fossaOlecranon

Head

Neck

Tuberosity

RadiusUlna

Humerus

Lateral epicondyle

Capitulum

Head

Neck

Radial tuberosity

Humerus

Medial epicondyle

Capitulum

Trochlea

HeadNeck

Radial tuberosity

Radius

UlnaRadial notch

Coronoid process

Trochlear notch

Olecranon

Coronoid processTrochlear notch

Olecranon

Groove forulnar nerve

of ulna

In extension: anterior view In extension: posterior view

In 90˚ flexion: lateral view In 90˚ flexion: medial view

Lateral condyle Medial condyle

spool and fits in the wrench-shaped trochlearnotch. This anatomic configuration, in con-junction with the collateral ligaments, pro-vides a stable hinge joint that can lift heavyobjects. Rotation of the forearm occursthrough the proximal and distal radioulnar ar-ticulations.

Distal to the radial head, the bone tapers toform the radial neck, then flares at the radialtuberosity—the insertion site of the biceps ten-don. Between the radius and the ulna is the interosseous membrane—a thickened, liga-mentous structure that connects the two

Elbow and Forearm

309

bones in a manner that provides stabilitywhile allowing forearm rotation.

Muscles that cross the elbow anteriorly in-clude the elbow flexors and the flexor-pronatorforearm muscles that originate from the medialepicondyle (Figure 15-2). In the forearm, thevolar muscles are arranged in three layers. Thesuperficial group includes the pronator teres,flexor carpi radialis, palmaris longus, and flexorcarpi ulnaris. The middle layer is the flexor dig-itorum superficialis. The deep layer comprisesthe supinator, flexor digitorum profundus,flexor pollicis longus, and pronator quadratus.The flexor-pronator muscle group primarilyprovides wrist flexion and forearm pronation.The biceps is a secondary flexor of the elbowand a strong supinator. Immediately deep tothe biceps lies the brachialis muscle—the majorflexor of the elbow.

Posterior elbow muscles include elbow ex-tensors, wrist and finger extensors, and thesupinator. Posterior forearm muscles are ar-ranged in two layers. The superficial grouporiginates from a common tendon at the lat-eral epicondyle and includes a lateral compo-nent (brachioradialis, extensor carpi radialislongus, and extensor carpi radialis brevis) anda medial subgroup (extensor digitorum, ex-tensor digiti minimi, extensor carpi ulnaris,and anconeus). The deep posterior forearmmuscles are the supinator, abductor pollicislongus, extensor pollicis brevis, and extensorpollicis longus (see Figure 15-2).

The brachial artery, the main artery of thearm and elbow, travels in the anterior com-partment of the arm adjacent to the mediannerve. Proximal to the elbow, it gives off collat-eral arteries that help form a rich plexus of ves-sels around the elbow. At the level of the radialhead, the brachial artery bifurcates into the ra-dial and ulnar arteries. The ulnar artery entersthe forearm posterior to the pronator teres,whereas the radial artery travels between thebrachioradialis and the supinator muscle.

The median nerve enters the forearm be-tween the humeral and ulnar heads of thepronator teres and travels inferior to the flexordigitorum superficialis muscle (Figure 15-3).The anterior interosseous nerve branches in-

nervate the index, and sometimes, the long,finger component of the flexor digitorum pro-fundus, the flexor pollicis longus, and thepronator quadratus. Because of the locationof its fibers in the median nerve, isolatedparalysis of the anterior interosseous nervemay occur with an elbow fracture. The rest ofthe median nerve innervates all the volar fore-arm muscles except the ulnar half of the flexordigitorum profundus (fourth and fifth fingers)and the flexor carpi ulnaris, both of which aresupplied by the ulnar nerve.

The ulnar nerve exits the anterior compart-ment of the arm, passing behind the medialepicondyle into the cubital tunnel at the el-bow, then enters the forearm between thetwo heads of the flexor carpi ulnaris (Figure15-4). It innervates the flexor carpi ulnarismuscle, the ulnar half of the flexor digitorumprofundus muscle, and, ultimately, the intrin-sic muscles of the hand.

In the arm, the radial nerve travels within theposterior compartment, then enters the ante-rior compartment lateral to the humerus. Inthe antecubital fossa, the radial nerve inner-vates the brachioradialis and extensor carpi ra-dialis longus before dividing into superficial(sensory) and deep (mostly motor) branches(Figure 15-5). The superficial radial nerve pro-vides sensation to the radial dorsal wrist andhand. The deep branch innervates the remain-ing extensor muscles of the forearm. It travelsdeep and through the supinator muscle andexits this muscle as the posterior interosseousnerve. Distal to the radial tuberosity, the deepbranch of the radial nerve may lie “on thebone” and, as such, is vulnerable to injury infractures of the proximal radius or in opera-tions at this site.

PHYSICAL EXAMINATIONInspect the elbow for swelling and ecchy-

mosis, and determine the carrying angle (theaxial alignment of the humerus and the ulnawith the elbow extended). The normal carry-ing angle is 10° to 20°, with most studiesobserving slightly greater cubitus valgus infemales. Angular deformities may occur sec-ondary to previous trauma, growth distur-

Chapter 15

310

Ulna Radius

Brachioradialismuscle

Insertions

Origins

Flexor carpi ulnaris muscle

(humeral origin via common

flexor tendon)

Flexor digitorumprofundus muscle

Extensor carpi ulnarismuscle (ulnar origin)

Extensor pollicislongus muscle

Extensor indicismuscle

Extensor carpi radialislongus muscle

Extensor carpi radialisbrevis muscle

Brachioradialis muscle

Brachialis muscle

Biceps brachii muscle

Supinator muscle

Pronator teres muscle

Radius

Pronator quadratus muscle

Brachioradialis muscle

Ulna

Brachialis muscle

Flexor digitorumprofundus muscle

Flexor digitorumsuperficialis muscle

Extensor carpiulnaris muscle

Flexor carpiulnaris muscle

Flexor digitorumprofundus muscle

Pronator teres muscle(ulnar head)

Flexor digitorum superficialismuscle (humeroulnar head)

Pronator teres muscle(humeral head)

Flexor pollicislongus muscle

Flexor carpiradialis muscle

Abductor pollicislongus muscle

Flexor pollicislongus muscle

Flexor digitorum superficialismuscle (radial head)

Extensor carpi radialislongus muscle

Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis (humeroulnar head)

Commonflexortendon

Commonextensor

tendon

Extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris muscles

Flexor carpi ulnarismuscle (ulnar origin)

Pronatorquadratusmuscle

Extensor carpiulnaris muscle

Extensor digitorummuscle (central bands)

Extensor digitiminimi muscle

Extensor digitorummuscle (lateral bands)

Triceps brachii muscle(medial head)

Triceps brachiitendon

Anconeus muscle

Biceps brachiimuscle

Supinator muscle

Abducor pollicislongus muscle

Pronator teresmuscle

Extensor pollicisbrevis muscle

Abductor pollicislongus muscle

Extensor pollicisbrevis muscle

Extensor pollicislongus muscle

Extensor indicismuscle

Anterior view

Posterior view

Note: Attachments of instrinsicmuscles of hand not shown

Figure 15-2: Bony Attachments of Muscles of Forearm

Elbow and Forearm

bances, or genetic syndromes. Ecchymosis,swelling, or both about the elbow indicate amuscle or tendon injury, fracture, or elbowsprain or dislocation.

Palpate subcutaneous landmarks for sites oftenderness, deformity, or effusion that indi-cate the site of occult fracture, tendinosis, lig-ament sprain, or tendon rupture. From lateralto medial, the structures in the antecubitalfossa are the biceps tendon, brachial artery,and median nerve. A palpable defect is key todiagnosing rupture of the distal biceps tendonor disruption of the triceps tendon. Joint effu-sion is best detected in the “soft spot” be-tween the lateral epicondyle, radial head, and

olecranon. Tenderness over the radial head orhumeral condyles may indicate an occult frac-ture that is not visible on radiographs.

The zero starting position for measurementof elbow motion is a straight extremity (Figure15-6). Young children commonly extend theelbow by 10° to 15°, but adults usually cannotextend the elbow past the zero starting posi-tion. The normal range of elbow flexion-extension is 0° to 145°. The plane of forearmrotation is pronation-supination. Pronation lit-erally means “the state of being prone” or, asit relates to the forearm, “the palm beingturned backward.” Likewise, supination liter-ally means “the state of being supine” (ie, the

311

Median nerve

Pronator teres m. (humeral head)

Flexor carpi radialis m.

Palmaris longus m.

Pronator teres m. (ulnar head)

Flexor digitorum superficialis m. (turned up)

Flexor digitorum profundus m.(lateral portion supplied via anterior

interosseous n.; medial portion by ulnar n.)

Anterior interosseous n.

Flexor pollicis longus m.

Pronator quadratus m.

Palmar branch

Then

arm

uscl

es Abductor pollicis brevis

Opponens pollicis

Cutaneous innervation

Anastomotic branch to ulnar n.

Flexorretinaculum

Common Proper

Palmar digital nn.

Articular branch

Flexor pollicis brevis(superficial head;

deep head suppliedby ulnar n.)

1st and 2nd lumbrical mm.

Branches to dorsum ofmiddle and distal phalanges

Figure 15-3: Median Nerve

sixteenThe Hand and WristJohn D. Lubahn, MDD. Patrick Williams, DO

Chapter 16

ANATOMY AND BIOMECHANICSThe carpus, or wrist, is composed of eight

carpal bones that link the forearm to the hand(Figure 16-1). The proximal carpal row(scaphoid, lunate, and triquetrum) articulateswith the distal radius and ulna, as well as thedistal carpal row (trapezium, trapezoid, capi-tate, and hamate). The pisiform, also part ofthe proximal row, is a sesamoid bone in theflexor carpi ulnaris tendon that articulatesonly with the triquetrum. The bones of thehand are the metacarpals and phalanges. The

carpometacarpal (CMC) joint of the thumb issaddle-shaped, a configuration that permitsabduction-adduction, as well as the circum-duction that permits opposition of the thumbto the fingers. The metacarpophalangeal(MP), proximal interphalangeal (PIP), and dis-tal interphalangeal (DIP) joints basically areflexion-extension hinge joints.

The skin on the dorsal surface of the hand isthin and flexible to allow full flexion of the fin-gers, whereas the palmar surface skin isthicker and characterized by creases. The

The human hand, as an extension of the brain, allows us to manipulate and in-teract with our environment and to perform activities as routine as opening adoor or as intimate as caressing a loved one. The hand also functions as part ofthe sensory system, providing tactile sensation for complex hand movementswithout the necessity of constant visual guidance; this function is epitomized

by blind people who read and musicians who entertain. An understanding and careful ex-amination of hand anatomy and function is crucial for the student of medicine.

336

Carpalbones

Lunate

Triquetrum

Pisiform

Capitate

Hamate andHook

BaseShaftsHead

BaseShaftsHead

BaseShaftsHead

BaseShafts

TuberosityHead

Right hand:anterior (palmar)view Sesamoid

bones

Carpalbones

Metacarpal bones

Proximal phalanges

Middle phalanges

Distalphalanges

1

2345

ScaphoidandTubercle

TrapeziumandTubercle

Trapezoid

Figure 16-1: Bones and Joints of Hand

The Hand and Wrist

distal volar crease of the wrist crosses theproximal scaphoid and the pisiform. The distalpalmar crease of the hand corresponds to theMP joint, and the proximal finger crease is atthe base of the proximal phalanx.

The extrinsic muscles of the wrist and handoriginate on the medial and lateral humeralcondyles and the proximal radius and ulna(see Figure 15-2). The extrinsic extensor ten-dons cross the wrist and are surrounded bytendon sheaths in six compartments boundedby the extensor retinacular ligament (Figure16-2). The extrinsic finger and thumb flexortendons and the median nerve enter the handthrough the carpal canal (Figure 16-3). Thetransverse carpal ligament, a thick band ex-tending from the hamate and pisiform to thescaphoid and trapezium, forms the inelasticroof of the carpal canal. A decrease in the sizeof the canal or an increase in the size of itscontents can cause compression of the me-dian nerve (carpal tunnel syndrome).

Intrinsic musculature includes thenar, hy-pothenar, and interosseous muscles (Figure16-4; see also Figures 15-4 and 15-5). Thethenar muscles are the abductor pollicis brevis, the opponens pollicis, and the superfi-cial head of the flexor pollicis brevis. The hy-pothenar muscles are composed of the ab-ductor digiti quinti, the opponens digiti quinti,and the flexor digiti quinti. The dorsal interos-sei, commonly referred to as dorsal intrinsics,abduct the fingers; the palmar interossei (pal-mar intrinsics) adduct the fingers.

The DIP joint of the fingers is flexed by theflexor digitorum profundus (FDP). It has a sep-arate muscle belly for the index finger (whichtherefore flexes independently) but a com-mon muscle belly for the long, ring, and smallfingers (which tend to work as a single unit).The PIP joint of the fingers is primarily flexedby the flexor digitorum superficialis (FDS). Ithas individual muscle bellies for each finger,thus providing the individual finger flexion atthe PIP joint that is necessary for activitiessuch as playing a musical instrument and typ-ing. The FDS separates into two parts beforeits point of insertion, and the FDP passesthrough the split (Figure 16-5). Both finger

flexors are enclosed in a common tendonsheath. The proximity of the FDS and FDP ten-don to the surrounding sheath promotes effi-cient movement, but adhesions from injury orinfection can be problematic in this region.

The interossei, along with the lumbricalmuscles, flex the MP joints and extend the PIPand DIP joints. The lumbrical muscles areunique in that they originate from the profun-dus tendons to insert into the dorsal appara-tus of the antagonistic extensor mechanism(see Figure 16-5). The interossei and the twoulnar lumbricals are innervated by the ulnarnerve, but the two radial lumbricals are inner-vated by the median nerve.

The MP joints of the fingers are extendedby the extensor digitorum longus, extensor in-dicis proprius, and extensor digiti quinti.When the MP joints are flexed, these musclesalso can extend the PIP joints; otherwise, theintrinsic muscles extend the PIP and DIPjoints. The complex arrangement of the ten-dons on the dorsum of the hand provides thenecessary synchrony and balance betweenflexors and extensors during the multiple pre-cise motions of the MP, PIP, and DIP jointsworking in concert. The main insertion of theextrinsic extensor muscle tendon is throughthe central slip at the base of the middle pha-lanx. The intrinsic muscles join with the ex-trinsic extensor through the interdigitatingtransverse and oblique fibers of the dorsal ap-paratus to extend the PIP and DIP joints.

Contracture or spasticity of the intrinsicmuscles creates increased tension on the dor-sal hood. A swan-neck deformity develops,with PIP joint hyperextension and MP andDIP joint flexion (Figure 16-6). Laceration ofthe central extensor tendon proximal to its in-sertion into the middle phalanx allows the lat-eral bands to slip volarly and produces the op-posite flexion, boutonnière (French from“button hole”) PIP joint deformity.

The radial artery lies radial to the flexorcarpi radialis tendon at the wrist (see Figure16-3). After crossing the snuffbox (see Figure16-2), the radial artery passes through the firstintermetacarpal space to the palm as themain contributor to the deep palmar arch,

337

Chapter 16

338

Posterior (dorsal) view

Extensor carpi ulnaris – Compartment 6

Extensor digiti minimi – Compartment 5

Extensor digitorumExtensor indicis

Extensor pollicis longus – Compartment 3

Extensor carpi radialis brevisExtensor carpi radialis longus

Abductor pollicis longusExtensor pollicis brevis

Radial artery inanatomical snuffbox

Dorsal interosseous muscles

Compartment 4

Compartment 2

Compartment 1

Extensor retinaculum

Abductor digitiminimi muscle

Intertendinousconnections

Transverse fibers ofextensor expansions (hoods)

Cross section of most distal portion of forearm

Extensor retinaculumExtensor pollicis longus – Compartment 3

Extensor carpiradialis brevisExtensor carpiradialis longus

Compartment 2

Extensorpollicis brevisAbductorpollicis longus

Compartment 1

Extensor digitorum andextensor indicis

Extensordigiti minimi

Extensorcarpi

ulnaris

Compartment 4

Compartment 5

Compartment 6

Ulna Radius

Plane of cross sectionshown below

6

54 3 2

1

Figure 16-2: Extensor Tendons at the Wrist

The Hand and Wrist

339

Figure 16-3: Flexor Tendons, Arteries, and Nerves at Wrist

Radialartery

Radius Ulna

Abductor digitiminimi muscle

Dorsal view

Palmar view

Tendinous slips tohood of extensordigitorum muscle

Deep transversemetacarpalligament

Palmarinterosseous

muscles

RadiusUlna

Dorsalinterosseousmuscles

Abductorpollicis

brevis muscle

Figure 16-4: Intrinsic Muscles of Hand

Palmaris longus tendon

Median nerve

Radial arteryFlexor carpi radialis

tendonFlexor pollicis longus

tendon in tendonsheath (radial bursa)

Palmar carpal ligament (reflected)(Synovial) tendon sheath

Transverse carpal ligament

Trapezium

1st metacarpal bone

Opponens pollicis muscle

Abductor pollicisbrevis muscle

(reflected)

Flexor pollicis brevismuscle (reflected)

Adductor pollicis muscle

Median duo

Radial trio

Flexor digitorumsuperficialis tendons andflexor digitorum profundustendonsCommon flexor sheath(ulnar bursa)

Ulnar trio

Ulnar arteryUlnar nerveFlexor carpi ulnaristendon

Pisiform

Abductor digiti minimi muscle

Flexor digiti minimi brevis muscle

Opponens digiti minimi muscle

Superficial palmar (arterial) arch

Lumbrical muscles

Twotendonquartets

Palmar view