01 96-601 1 /83/0404-0206$02.00/0 THE JOURNAL OF ORTHOPAED~C AND SPORTS PHYSICAL THERAPY Copyright O 1983 by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association

Clinical Anatomy and Mechanics of the Wrist and Hand CAROLYN T. WADSWORTH, MS, LPT*

Hand rehabilitation is an area with the potential for providing orthopaedic physical therapists a challenging and rewarding practice. However, success in treating the patient with hand dysfunction is closely associated with the therapist's understand- ing of essential anatomic and pathokinesiologic principles and the related ability to adequately evaluate, plan, and perform treatment.

This article, the first of a two-part series, is intended to provide a working knowledge of clinical anatomy, mechanics, and pathology of the wrist and hand. Emphasis is placed on the structure and function of parts which commonly limit motion, and sufficient information is provided to aid the clinician in performing a differential diagnosis and developing treatment rationale. The second part of the series will describe a practical method of evaluation and offer treatment suggestions for specific disorders.

OSTEOLOGY

Twenty-seven bones (excluding sesamoids) contribute to the formation of the wrist and hand skeleton. These bones are commonly classified into units known as phalanges, metacarpus, and carpus according to similarities in structure and function (Fig. 1).

The 14 phalanges resemble miniature long bones, with shafts and expanded ends. The con- cave proximal ends, the bases, display two shal- low depressions which fit the corresponding pul- ley-shaped heads of adjacent phalanges. The heads, with their distinct condyles, form the con- vex partner of the interphalangeal (IP) joints. The close congruency of these "hinge" surfaces contributes greatly to finger joint stability. (The bases of the proximal phalanges 2-5 are modi- fied to articulate with the rounded metacarpal heads and thus possess a biconcave surface.)

Included in the metacarpus are five bones, also with elongated shafts and expanded ends. The bases articulate with the distal row of carpal bones, as well as with one another, in plane joints with minimal movement. The convex distal heads are rounded rather than pulley-shaped

like the phalanges; their configuration produces more mobility at the biaxial metacarpophalan- geal (MP) joints, but less bony stability than at the IP joints. The first metacarpal differs in that its head is pulley-shaped, and its base is sepa- rate from the common joint formed by the others.

The bones of the carpus are arranged in two rows, with four bones to a row. The distal row includes the trapezium, trapezoid, capitate, and hamate, and the proximal row contains the scaphoid, lunate, triquetrum, and pisiform. Dis- tinguishing features of each include the follow- ing:

a) Trapezium-tubercle for attachment of flexor retinaculum; groove for flexor carpi radi- alis tendon; saddle-shaped facet for articulation with first metacarpal.

b) Trapezoid-smallest bone in distal row. c) Capitate-largest and most central of car-

pals; articulates with seven other bones; inter- carpal ligaments directed toward it.

d) Hamate-hook-like hamulus, which offers protection for the ulnar artery and nerve, and attachment of flexor retinaculum.

e) Scaphoid-prominent tubercle for attach- ment of flexor retinaculum; bridges joint between two rows of carpals, receiving most of the force

'Associate in the Physical Therapy Educational Programs, University transmitted through the radius and frequently of Iowa, Iowa City. IA 52242 fractured in falls; proximal pole without its own

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blood supply in one-third of the population thus subject to avascular necrosis following a frac- ture.

f) Lunate-semilunar shape; most frequently dislocated carpal bone, which is of significance due to its proximity to the median nerve.

g) Triquetral-three-sided, with facet for artic- ulation with pisiform.

h) Pisiform-pea-shaped with attachments for flexor and extensor retinacula, pisohamate and pisometacarpal ligaments, and tendons of flexor carpi ulnaris and abductor digiti minimi muscles.

The bones of the hand are so arranged that three separate arches emerge to enhance pre- hensile function. The longitudinal arch spans the

hand lengthwise and two lateral arches run transversely, one at the level of the metacarpal heads, and the other at the carpus. The arch formed by the carpus also provides the floor of a bony tunnel-the carpal tunnel-for support and protection of the finger flexor tendons and median nerve (Fig. 2).

When viewed from the radial side, the anterior projections of the scaphoid and trapezium tuber- cles are prominent. They contribute to formation of the osseous portion of the carpal tunnel and in addition provide a supporting base for the thumb in a plane which allows it to oppose the rest of the hand. Experts in accident insurance attribute 50% of the value of the hand to the

LUNATEJ '-CAP] TATE

Fig. 1 . Hand skeleton.

. -\ -- ULNARARTERY

ULNAR NERVE FLEXOR TENDONS

HAMATE FLEXOR RETINACUL

MEDIAN NERVE PlSlFORM TRAPEZIUM

TRIQUETRUM

LUNATE SCAPHOID

Fig. 2. Carpal tunnel-space between concave carpus and transverse retinacular ligament, enclosing the median nerve and flexor tendons of the fingers.

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208 WADSWORTH JOSPT Vol. 4, No. 4

thumb, its importance lying in its ability to op- pose, and thus, grasp.

An ulnar view reveals the anterior projections of the pisiform and hamulus which form the me- dial boundary of the carpal tunnel. The area between the hamate and pisiform is converted into another fibroosseous tunnel by the pisoha- mate ligament. This tunnel of Guyon contains the ulnar artery and nerve and may be a site of compression injury.

ARTHROLOGY

Carpal Joints

The carpal bones are firmly bound together on the dorsal and palmar surfaces by short inter- carpal ligaments. They are also attached to each other individually by deeper interosseous liga- ments. They articulate with each other iv synovial joints and can be passively moved in relation to each other. The joint capsules and interosseous ligaments divide the synovial cavity into the sep- arate joints described below (Fig. 3).

The radiocarpal joint is the articulation be- tween the convex proximal row of carpal bones and the concave radius and disc. The midcarpal joint lies between the proximal and distal rows of carpals; it may be described as a "compound articulation" in which each row acts as a unit and each has both a convex and concave artic- ulating portion. Together, the radiocarpal and midcarpal joints produce the motions occurring at the biaxial wrist joint: flexion, extension, radial deviation, and ulnar deviation. The common car- pometacarpal joint is an irregular combination of plane articulations between the distal row of carpals and the bases of metacarpals 2-5. It

allows slight gliding, becoming more mobile to- wards the fifth metacarpal, making cupping of the palm possible.

The trapezio-metacarpal joint is a saddle- shaped articulation between the trapezium and first metacarpal which, with its exceptional mo- bility, is often referred to as the "key" joint of the hand. Its wide range includes pure move- ments of flexion, extension, abduction, and ad- duction, and combinations of movements pro- ducing opposition and circumduction. During ab- duction and adduction, the convex metacarpal surface moves on the concave trapezium; in flexion and extension, the concave metacarpal surface moves on the convex trapezium. By def- inition, motions of the thumb (for example, flex- ion) occur in a plane (frontal) perpendicular to the plane (sagittal) of the same movement in the digits. The pisiform-triquetral joint is a small plane joint which has its own separate synovial cavity; it allows only a small amount of gliding. The ulno-menisco-triquetral joint is the articula- tion between the ulna, disc, and triquetrum, and should be termed a "clinical joint" because it has no capsule nor separate synovial cavity; however it becomes functionally important by providing component gliding accompanying su- pination and pronation. Joint play movements may be produced in all of these carpal joints in response to traction, gliding, and rotary forces.

The approximate ranges of motion for the wrist are 70-80" extension, 75-85" flexion, 15-20" radial deviation, and 30-40" ulnar deviation. However, these ranges may be influenced by the position of the finger joints (and vice versa) due to the constant length of the extrinsic finger flexor and extensor muscles. For example, wrist

CARPOMETACARPAL- (COMMON)

TRAPEZIO-METACARPAL (THUMB)

MIDCARPAL PlSlFORM

ULNO-MENISCO- RADIOCARPAL

TRIQUETRAL

Fig. 3. Joints of the carpus.

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flexion is greater with fingers extended. This property has important clinical ramifications such as a) the need for maintaining a constant position of other joints when measuring any one particular joint; b) the need for identifying hand position when measuring strength; c) the need for determining when tenodesis may be desired when planning treatment, such as utilizing wrist extension to enhance grasp in the C6 cord injury or utilizing wrist flexion to enhance finger exten- sion in spastic cerebral palsy. The thumb rotates 90" to oppose the fingers, abducts 65-80" from the plane of the palm, and extends 65-80' away from the palm.

The ligaments attaching the carpals are often not distinct entities, like those of the shoulder, and may be hard to identify. The major ligaments are listed below in relation to the joints they span (Fig. 4).

a) Radiocarpal joint-volar radiocarpal, volar

ulnocarpal, dorsal radiocarpal, radial collateral, and ulnar collateral ligaments.

b) Midcarpal joint-volar and dorsal intercar- pal and interosseous ligaments.

c) Common carpometacarpal joint-volar and dorsal carpometacarpal, and intermetacarpal lig- aments.

d) Trapezio-carpometacarpal joint-lateral, volar, and dorsal oblique ligaments.

Metacarpophalangeal (MP) Joints

The articulations formed by metacarpals 2-5 and respective proximal phalanges are biaxial joints. The joint capsules are reinforced (or re- placed) dorsally by the dorsal hood apparatus and volarly by the volarplates. The distal portion of the volar plates is cartilagenous and firmly fixed to the phalanx, whereas the proximal por- tion is membranous and loosely attached to the

COLLATERAL LIGAMENTS

VOLAR PLATES

!EP TRANSVERSE METACARPAL

LIGAMENTS CARPO-METACARPAL

LIGAMENTS

INTERCARPAL LIGAMENTS PISOMETACARPAL LlGP

FLEXOR CARPI PISOHAMATE L lGAMENl

RADIALIS TENDON

COLLATERAL COLLATERAL LIGAMENT

ULNOCARPAL RADIOCARPAL LIGAMENT

LIGAMENT

Fig. 4. Ligaments of the wrist and hand.

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21 0 WADSW ORTH JOSPT Vol. 4. No. 4

meta~arpa l . '~ Adhesions commonly form be- tween the membranous surfaces which fold upon themselves when immobilized in flexion. On their palmar surface, the plates are grooved to receive and pad the flexor tendons of the finger (Fig. 4).

Laterally, the joints are supported by the col- lateral ligaments which are strong cords running obliquely from the dorsum of the metacarpals to the ventral aspect of the base of the phalanges (Fig. 4). They become taut in flexion, thereby restricting MP joint abduction and adduction in this position. Contractures of these ligaments is a key factor contributing to loss of MP joint flexion. In order to prevent their shortening dur- ing immobilization, the fingers should be splinted with the MP joints in 70-90" flexion.' The meta- carpal heads are connected to one another by superficial and deep transverse metacarpal lig- aments which offer indirect support for the joints.

Movement increases progressivel'y from the second to the fifth MP joint, but is generally approximated to range from 90" flexion to 25" extension, and 20" abduction to 0" adduction.

The articulation of the first metacarpal and phalanx is a hinge joint. Bony stability is inherent in its configuration, and to this is added volar and collateral ligamentous support (Fig. 4). Flex- ion occurs to 50". Traction, gliding, and rotatory joint play movements are also possible in all of the MP joints.

lnterphalangeal (IP) Joints

The articulations between adjacent phalanges are termed hinge joints because the pulley-like surfaces allow motion in only one plane. The volar and collateral ligaments are similar to those of the MP joints, but are not as important to stability (Fig. 4). The collaterals differ in that they are most taut at 25" of flexion. This position, therefore, is ideal for splinting the fingers in order to prevent IP joint contractures (contrac- ture results in loss of IP joint extension). Flexion at the proximal interphalangeal (PIP) joints ap- proximates 1 1 0°, at the distal interphalangeal (DIP) joints 90°, and at the thumb interphalan- geal joint 90". Traction, gliding, and joint play movements are also possible at the IP joints.

MECHANICS

The physical therapist is frequently called upon to treat disorders of the hand stemming from soft tissue pathology. Some of the more

common structures, their interrelationships, and disorders are discussed here.

The subcutaneous tissue of the dorsum of the hand is structurally quite different from the tissue of the palm. The dorsal areolar tissue is thin and elastic to permit stretching as a fist is made. Its loose attachment and preponderance of lym- phatics and veins account for the fact that swell- ing is manifested predominantly on the dorsal surface, although the source of the problem of- ten lies elsewhere in the hand.= In the palm, many strong fibrous fasiculi connect the skin tightly to the adjacent palmar aponeurosis, per- mitting relatively little sliding of the skin and enhancing secure grasp.

The palmar aponeurosis, just deep to the sub- cutaneous tissue, is composed of dense fibrous tissue. It is continuous with the palmaris longus tendon and fascia covering the thenar and hy- pothenar muscles and extends distally into the transverse metacarpal ligaments and flexor ten- don sheaths. It provides protection for the ulnar artery and nerves and digital vessels and nerves, and may transmit a weak flexion force from the palmaris longus into the fingers (Fig. 5). Nodule formation or scarring in this structure produces the clinical entity known as Dupuytren's contrac- ture, which may eventually result in flexion con- tractures of the digits.

The flexor retinaculum (transverse carpal lig- ament), deep to the palmar aponeurosis, spans the area between the pisiform, hamate, scaph- oid, and trapezium. It forms the "roof" of the carpal tunnel which transmits some of the ten- dons, vessels, and nerves of the hand. The ret- inaculum offers attachment for the thenar and hypothenar muscles, helps maintain the trans- verse carpal arch, prevents bowstringing of the extrinsic flexor tendons, and protects the median nerve (Fig. 5). The median nerve is subject to compression in this relatively unyielding space, a condition known as carpal tunnel syndrome.

Muscles acting upon the hand are referred to as extrinsic when their origin lies outside the hand, and intrinsic when originating within the hand. The extrinsic and intrinsic muscles are differentiated in Table 1. A thorough review of muscle origins, insertions, and actions is rec- ommended, but due to comprehensive coverage e l~ewhere,~, " is not included in this text. Se- lected kinesiologic concepts related to hand function and impairment are described in the following paragraphs.

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JOSPTSpring 1983 ANATOMY AND MECHANICS OF THE WRIST AND HAND

FLEXOR DlGlTORUM PROFUNDUS

FLEXOR DlGlTORUM SUBLlMlS

FIBROUS DIGITAL SHEATHS

FLEXOR RETINACULUM

APONEUROSIS ULNAR NERVE

MEDIAN NERVE

Fig. 5. Volar soft tissue relationships in the wrist and hand.

TABLE 1 Muscles which act upon the hand: extrinsic versus intrinsic

Extrinsic muscles Intrinsic muscles

Extensor carpi radialis longus and brevis

Extensor c a r ~ i ulnaris

Flexor carpi radialis Flexor carpi ulnaris Palrnaris longus Extensor pollicis longus

and brevis Abductor pollicis longus Extensor indicis Extensor digiti rninirni Extensor digitorurn

cornrnunis Flexor digitorurn sublirnis Flexor digitorum profundus Flexor pollicis longus

Lurnbricals

Dorsal and palmar interossei

Adductor pollicis Flexor pollicis brevis Abductor pollicis brevis Opponens pollicis

Flexor digiti rninirni Abductor digiti rninirni Opponens digiti rninimi Palrnaris brevis

operation of the hand is notably enhanced by its large number of muscles. The design of the extrinsics, the muscle bellies of which are lo- cated in the forearm but taper into tendons prox- imal to the wrist, allows the action of many mus- cles without inordinate bulkiness. The extrinsic muscle tendons en route to the fingers cross the wrist and serve to enhance its stability by forcing the hand proximally into the concave radial sur- face during cocontraction (Fig. 5). The muscles acting upon the wrist itself also contribute to wrist stability by achieving a balance of flexor and extensor forces through their attachment to corresponding surfaces of the stable metacarpal bases.4

The extrinsic flexor muscle tendons of the fingers pass into the hand deep to the flexor retinaculum. Flexor digitorum sublimis, which

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21 2 WADSWORTH JOSPT Vol. 4. No. 4

primarily flexes the PIP joint, and secondarily assists MP joint flexion, divides into tendons which are capable of relatively independent ac- tion at each finger. The flexor digitorum profun- dus, which solely flexes the DIP joints and assists in flexion of the PIP and MP joints, also supplies tendons for each finger, but unlike sublimis, the tendons cannot operate independently. There- fore, if one wishes to isolate the function of these two muscles in flexion of the PIP joint, the fin- ger(~) to the side(s) of the finger being tested are passively held in extension to pull the profundus distally which "inactivates" it and allows the sublimis to act alone at the PIP joint.3

The flexor tendons are tethered to the fingers by fibrous sheaths between the distal palmar crease and the PIP joint. This area is referred to as "no man's land" because of the difficulty of

primary repair of two severed tendons lying within this rigid fibroosseous space.

The dorsal extensor tendons are retained at the wrist by the extensor retinaculum, but are separated from it as well as the underlying bones by tendon sheaths. Toward the distal ends of the metacarpals, the four tendons of extensor digi- torum communis (EDC) are interconnected by juncturae tendinae, limiting their independent motion (Fig. 6). Extension of the ring finger MP joint is hindered by flexion of the middle and little fingers because the juncturae tendinae pull the ring finger extensor distally, rendering it lax. Conversely, extension of the ring. finger exerts an extensor force upon its neighbors, such that they can be actively extended even if the middle and little extensor tendons are severed proximal to the junc t~ rae .~

PAN

Fig. 6. Dorsal hood apparatus, extensor tendons, and ligaments of fingers.

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As the EDC tendons cross the region of the MP joints, their main connection to the proximal phalanx is through the sagittal bands (dossier), which pass palmarward to attach to the volar plate (Fig. 6). The primary function of the sagittal bands is to transmit the extension force of the EDC, thus extending the MP joint, but they also serve to prevent bowstringing of the extensor tendon d o r ~ a l l y . ~ - ~ , ' ~ When hyperextension of the MP joint is allowed, the force and excursion of the EDC will be transmitted to the proximal phalanx rather than the interphalangeal joints. In this situation, IP joint extension is only possible through the intrinsic^.^, '. " Thus a test to differ- entiate function of the extrinsic and intrinsic ex- tensors would involve maintaining full active ex- tension of the MP joints and then attempting IP joint extension, an action that would only be possible i f the intrinsics were operating.

Between the MP and PIP joints the EDC ten- dons divide into three parts, the central slip which inserts into the base of the middle phalanx, and two lateral bands (Fig. 6). These lateral bands eventually rejoin into a terminal tendon which inserts into the base of the distal phalanx. Rupture of this insertion produces a mallet fin- ger. Fibers from the lumbricals and interossei join the EDC tendons over the proximal phalanx, contributing to the dorsal hood apparatus. The tendons of the intrinsics pass volar to the MP joint axis, thus exerting a flexion force on these joints, whereas both the intrinsic and extrinsic tendons pass dorsal to the PIP and DIP joint axes upon which they exert an extension force. Thus, labeling the dorsal hood as extensor hood is inappropriate because it also serves as a flexor of the MP.

The conjoined lateral bands formed by the

continuation of both extrinsic and intrinsic ten- dons are prevented from dislocating dorsally by the transverse retinacular ligaments which link them to the volar plates of the PIP joints (Fig. 6). Stretching or laxity of these ligaments allows bowstringing of the bands which transmits ex- cessive extension force to the PIP joint from the intrinsics. This abnormal tension-combined with a volar plate rupture or the joint laxity char- acteristic of rheumatoid arthritis-contributes to hyperextension deformity of the PIP joint. Ter- minal phalangeal flexion frequently results from the taut profundus tendon in the presence of weakened DIP joint extension. This deformity is referred to as "swan neck" (Fig. 7h8

The oblique retinacular ligament (Landsmeer's ligament) also contributes to interdependence of interphalangeal joint movement. It is attached between the PIP volar plate, where it is volar to the joint axis, and the terminal tendon, where it is dorsal to the DIP joint axis (Fig. 6). When the PIP joint is extended it exerts a passive extensor force on the DIP joint, and when the PIP joint flexes, it allows the DIP joint to flex. In the normal hand the function of the oblique retinacular lig- ament is essentially nil. However, if it becomes contracted after burns or trauma it produces a tenodesis effect (when the PIP joint is extended, the DIP joint will be brought into fixed extension by this ligament).'

When the PIP joint is flexed, the conjoined lateral bands slip volarly, decreasing the excur- sion required for full DIP joint flexion. If the PIP joint is fully flexed passively, the extensor mech- anism is held distally by the central slip and thus check-reined. The lateral bands become com- pletely lax, thus permitting only weak and limited distal joint extension.235 If, on the other hand,

LATERAL BANDS\

CENTRAL SLIP EXTENSOR DlGlTORUM COMMUNIS

INTEROSSEOUS PROFUNDUS TENDON MUSCLE

TRANSVERSE RETINACULAR

LIGAMENT

LUM'BRICAL MUSCLE

Fig. 7 . Swan neck deformity, demonstrating laxity of the transverse retinacular ligament.

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WADSWORTH JOSPT Vol. 4, No. 4

LATERAL BANDS

\

OBLIQUE RETINACULAR

LIGAMENT T LUMBRICAL

EXTENSOR DlGlTORUM COMMUNIS

'INTEROSSEOL MUSCLE

TRANSVERSE MUSCLE RETINACULAR

LIGAMENT

Fig. 8. Boutonniere deformity, demonstrating rupture of the central slip

the central slip is ruptured from its insertion, the extensor mechanism is pulled proximally render- ing the lateral bands taut. The joint is pulled into flexion by the unopposed flexor digitorum sub- limis, and the lateral bands which now lie volar to the PIP joint axis function as flexors. The force of the intrinsic muscles and EDC are transmitted directly to the distal phalanx, extending it, and producing a "boutonniere deformity" (Fig. 8).8-10 When evaluating the DIP joint in cases of PIP joint contracture, these interrelationships must be considered.

The lumbrical muscles originate from the flexor digitorum profundus tendons and insert into the dorsal apparatus. During contraction, they pull the profundus tendons distally, thus possessing the unique ability to relax their own antagonist.' In instances of lumbrical spasm or contracture, as in rheumatoid arthritis, attempts to flex the fingers via the profundus result in transmission of force through the lumbricals into the extensor apparatus, contributing to exten- sion rather than flexion. This may result in a "lumbrical plus deformity," i.e., MP joint flexion and IP joint extension. The lumbrical muscles serve as a primary organ of feedback in the hand. They are ideally suited to link position and movement of the hand and finger joints due to their location as well as abundance of annulos- pinal (AS) endings.

NEUROLOGY

Motor Innervation

Clinical evaluation of neurological damage is made difficult by the numerous muscles control-

ling the digits, considerable substitution, and the sometimes varying nerve supplies of these mus- cles. Following is a general summary of the major nerves and their corresponding loss of function following injury.

The median nerve in its passage along the forearm supplies the following muscles: pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum sublimis, flexoq pollicis longus, pronator quadratus, and flexor digitorum profun- dus (to index, middle, and sometimes ring fin- gers). It then passes under the flexor retinaculum and enters the palm, splitting into a sensory branch and a motor branch which supplies the following: abductor pollicis brevis, opponens pol- licis, flexor pollicis brevis, and first and second lumbricals. Impairment resulting from median nerve paralysis includes inability to oppose or flex the IP joint of the thumb and inability to flex the first two fingers, resulting in a "benediction attitude." Loss of the above functions severely hinders the ability to perform precision maneu- v e r ~ . ~

The ulnar nerve supplies the following muscles in the forearm: flexor carpi ulnaris and flexor digitorum profundus (to little and sometimes ring fingers). In the hand it innervates the following: flexor digiti minimi, abductor digiti minimi, op- ponens digiti minimi, adductor pollicis, palmaris brevis, third and fourth lumbricals, and the inter- ossei. Paralysis of the ulnar nerve produces loss of thumb adduction (lateral pinch), weakness in power grip,6 and difficulties in finger spreading and coordinated activities such as piano playing. An ulnar claw hand deformity, i.e., "intrinsic minus" with MP joint extension and IP joint flex-

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JOSPT Spring 1983 ANATOMY AND MECHANICS OF THE WRIST AND HAND 21 5

ion, often results. This deformity is more severe in lesions distal to innervation of flexor digitorum profundus.

The motor supply of the radial nerve is con- fined to the forearm where branches are given to the following: extensor carpi radialis longus and brevis, extensor carpi ulnaris, supinator, extensor digitorum communis, abductor pollicis, extensor pollicis longus and brevis, extensor indicis, and extensor digiti minimi. Radial nerve paralysis prevents extension of the wrist and MP joints of the fingers. Since wrist extension pro- vides synergistic and stabilizing functions, this loss can significantly hamper hand function. The ability to extend and abduct the thumb is also lost.

Sensory Innervation

The hand is sometimes referred to as a "sensory organ" because 25% of all the Paci- nian (touch) corpuscles in the body are located therein. The motor system is absolutely depend- ent upon the constant feedback it receives from the sensory receptors. Branches of the three major peripheral nerves carry sensation from the hand in the following manner.

a) Median-lateral portion of palm and thenar surface; volar part of thumb, index, and middle fingers, and lateral half of ring finger, extending over the dorsum of the terminal phalanges; in- nervation is purest at tip of index finger.

b) Ulnar-ulnar side of hand, medial half of ring finger, and little finger (both dorsal and palmar surfaces); innervation is purest at tip of little finger.

c) Radial-dorsum of hand, lateral to fourth metacarpal, and dorsal surfaces of thumb and first 2% digits to DIP joints; innervation is purest at the dorsal web space between thumb and index finger.

Sensory changes produced by cervical root pressure are frequently experienced in the dis- tal-most areas of the dermatomes, thus involving the hand. When evaluating the hand, knowledge of the dermatomal distribution assists in differ- entiating between nerve root and peripheral nerve lesions. Root level representation includes C6 to the thenar area and thumb, C7 to the midpalm and dorsal areas and index, middle, and ring fingers, and C8 to the hypothenar area and little finger (Fig. 9).' Because of the similar patterns of C8 and ulnar nerve sensory distri- bution, additional motor tests may be necessary for making a differential diagnosis.

VOLAR DORSAL

Fig. 9. a) Delineation of the peripheral cutaneous sensation supplied by the radial (R), median (M), and ulnar (U) nerves. b) Delineation of sensation derived from cervical root levels C6, C7, and C8.

ANGIOLOGY

Arterial'

The hand receives its blood from the radial and ulnar arteries. The radial artery courses along the lateral side of the forearm to the wrist, where its pulse is palpable just lateral to the flexor carpi radialis tendon. After giving off the superficial palmar branch it winds laterally around the dorsum of the wrist and enters the palm between the first and second metacarpals where it forms the deep palmar arch by uniting with the deep branch of the ulnar artery. The radial artery gives off a superficial palmar branch proximal to the scaphoid which anastomoses with the corresponding ulnar branch forming the superficial palmar arch. This arch is larger and more significant than the deep arch.

The ulnar artery crosses the wrist medially, where it is superficial to the flexor retinaculum. Just distal to the pisiform it divides into a super-

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21 6 WADSWORTH JOSPT Vol. 4, No. 4

ficial branch, which continues across the palm as the superficial palmar arch, and a deep branch, which anastomoses with the radial artery completing the deep arch.

From the deep palmar arch arise the palmar metacarpal arteries, which join the palmar digital arteries from the superficial arch. They extend into the fingers as digital arteries.

Venous

The hand is drained by a plexus of superficial and deep veins, of which the superficial is most significant.

The superficial system is best developed over the dorsal surface of the hand and becomes increasingly prominent with age. At the level of the wrist, this system converges into the cephalic vein laterally, and the basilic vein medially, which ascend superficially up the forearm.

'

The deep veins of the hand travel in pairs with the arteries (vena comitantes). They ascend from the digits to the palmar arches to the radial and ulnar arteries.

REFERENCES

1. Cailliet R: Hand Pain and Impairment, Ed 2. Philadelphia: FA Davis Co. 1975

2. Harris C, Rutledge GL: The functional anatomy of the extensor mechanism of the finger. J Bone Joint Surg 54A(4):713-726, 1972

3. Hoppenfeld S: Physical Examination of the Spine and Extremi- ties. New York: Appleton-Century-Crofts, 1976

4. Kapandji IA: The Physiology of the Joints. Vol 1. Baltimore: Williams 8 Wilkins Co, 1970

5. Lampe EW: Surgical anatomy of the hand. ClBA Clin Symp, 9, 1957

6. Landsmeer JM: Power grip and precision handling. Ann Rheum Dis 22:164-170. 1962

7. Moore KL: Clinically Oriented Anatomy. Baltimore: Williams 8 Wilkins, 1980

8. Smith RJ: Balance and kinetics of the fingers under normal and pathological conditions. Clin Orthop 104:92-111, 1974

9. Souter WA: The problem of Boutonniere deformity. Clin Orthop 104:116-131, 1974

10. Swezey RL: Dynamic factors in deformity of the rheumatoid hand. Bull Rheum Dis 22. 649-656. 1971 -72

11. Warwick R. Williams PC (eds): Gray's Anatomy. 35th British Ed. Philadelphia: WB Saunders Co, 1973

12. Weeks P. Wray C: Management of Acute Hand Injuries. St. Louis: CV Mosby Co, 1973

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