Joints of the upper limb pdf - Upper limb

406

CHAPTER 9

supplies the medial third of the dorsum of the hand

tendon, descends over the extensor retinaculum, and

winds around the ulna deep to the flexor carpi ulnaris

posterior cutaneous branch of the ulnar nerve

The

finger.

the ulnar nerve, also supplies the lateral side of the ring

variation. Frequently, a dorsal digital nerve, a branch of

hand and fingers supplied by the radial nerve is subject to

side of the ring finger. The area of skin on the back of the

the thumb, the index and middle fingers, and the lateral

It divides into several dorsal digital nerves that supply

lateral two thirds of the dorsum of the hand (Fig. 9.38).

descends over the extensor retinaculum, and supplies the

around the radius deep to the brachioradialis tendon,

winds

superficial branch of the radial nerve

The

The Upper Limb

(Fig. 9.38). It divides into several dorsal digital nerves

cal muscle on the lateral side (Fig. 9.63).

side and farther distally receives the tendon of the lumbri

insertion of the corresponding interosseous muscle on each

The dorsal extensor expansion receives the tendon of

(Fig. 9.63).

verge to be inserted into the base of the distal phalanx

which con

two lateral parts,

the middle phalanx, and

which is inserted into the base of

central part,

parts: a

phalangeal joint, the extensor expansion splits into three

(Figs. 9.56 and 9.57). Near the proximal inter

expansion

extensor

tendon joins the fascial expansion called the

On the posterior surface of each finger, the extensor

digiti minimi (Fig. 9.55).

joined on its medial side by the two tendons of the extensor

of the extensor indicis, and the tendon to the little finger is

to the index finger is joined on its medial side by the tendon

proximal to the heads of the metacarpal bones. The tendon

connect the tendons to the little, ring, and middle fingers,

of the dorsum of the hand. Strong oblique fibrous bands

which occupies the whole width

subfascial space,

roof of a

embedded in the deep fascia, and together they form the

sum of the hand (Figs. 9.56 and 9.57). The tendons are

under the extensor retinaculum and fan out over the dor

The four tendons of the extensor digitorum emerge from

Insertion of the Long Extensor Tendons

seous spaces.

cates with the deep veins of the palm through the interos

arch, which receives digital veins and freely communi

part of the blood from the whole hand drains into the

medial side, into the basilic vein (Fig. 9.100). The greater

on the lateral side into the cephalic vein and, on the

proximal to the metacarpophalangeal joints and drains

The dorsal venous arch lies in the subcutaneous tissue

Dorsal Venous Arch (or Network)

supply from palmar digital nerves.

remainder of the dorsum of each finger receives its nerve

nerves do not extend far beyond the proximal phalanx. The

The dorsal digital branches of the radial and ulnar

the little fingers.

that supply the medial side of the ring and the sides of

-
-

Mallet Finger

flexed when the extensor tendon is taut. The last 20° of active

Avulsion of the insertion of one of the extensor tendons into

the distal phalanges can occur if the distal phalanx is forcibly

extension is lost, resulting in a condition known as mallet
finger

extension of the distal interphalangeal joint. This injury can

to its insertion into the base of the middle phalanx results in

(Fig. 9.71).

Boutonnière Deformity

Avulsion of the central slip of the extensor tendon proximal

a characteristic deformity (Fig. 9.71C). The deformity results

from flexing of the proximal interphalangeal joint and hyper-

result from direct end-on trauma to the finger, direct trauma

over the back of the proximal interphalangeal joint, or lacera-

tion of the dorsum of the finger.

C L I N I C A L N O T E S

The Radial Artery on the Dorsum

ligament of the joint (Fig. 9.65). On reaching the dorsum

longus and extensor pollicis brevis, and lies on the lateral

wrist joint, beneath the tendons of the abductor pollicis

The radial artery winds around the lateral margin of the

of the Hand

of the hand, the artery descends beneath the

n of

tendo

the extensor pollicis longus to reach the

al between

interv

the

two heads of the first dorsal interosseous

re,

muscle; he

the margins of the olecranon fossa of the humerus and

, it is attached above to

Posteriorly

head of the radius.

ulna and to the anular ligament, which surrounds the

and below to the margin of the coronoid process of the

sae and to the front of the medial and lateral epicondyles

along the upper margins of the coronoid and radial fos

, it is attached above to the humerus

Capsule: Anteriorly

Synovial hinge joint

Type:

surfaces are covered with hyaline cartilage.

ulna and the head of the radius (Fig. 9.72). The articular

capitulum of the humerus and the trochlear notch of the

This occurs between the trochlea and

Articulation:

and the shoulder joint are fully described on pages 362

The sternoclavicular joint, the acromioclavicular joint,

(Fig. 9.65).

Dorsal digital arteries pass to the thumb and index finger

take part in the anastomosis around the wrist joint.

Branches of the radial artery on the dorsum of the

(see page 403).

the artery turns forward to enter the palm of the hand

hand

Joints of the Upper Limb

and 364.

Elbow Joint

■

Basic Anatomy

407

extensor expansion

extensor digitorum

lumbrical

interosseous

FIGURE 9.71

indicate the direction of the pull of the muscles and the deformity.

Boutonnière deformity. The insertion of the extensor expansion into the base of the middle phalanx is ruptured. The arrows

expansion into the base of the distal phalanx ruptured; sometimes, a flake of bone on the base of the phalanx is pulled off.

Mallet or baseball finger. The insertion of the extensor

which converge to be inserted into the base of the distal phalanx.

geal joint splits into three parts: a central part, which is inserted into the base of the middle phalanx, and two lateral parts,

Posterior view of normal dorsal extensor expansion. The extensor expansion near the proximal interphalan-

lateral

epicondyle

capsule

olecranon
process

lateral collateral

ligament

neck of radius

annular ligament

capsule

annular ligament

biceps

oblique cord

coronoid

process

medial

collateral

ligament

ulnar nerve

medial epicondyle

capitulum

annular

ligament

head of

radius

quadrate

ligament

fat in coronoid fossa

trochlea

olecranon

process

synovial

membrane

capsule

fat in

olecranon

fossa

capsule

synovial

membrane

capsule

trochlea

coronoid

process

ecranon

ocess

lateral collateral

ligament

neck of radius

annular ligament

capsule

annular ligament

biceps

oblique cord

coronoid

process

col

liga

media

quadrate

ligament

fat in coronoid fossa

trochlea

olecranon

process

synovi

memb

capsule

fat

ole

fos

capsule

synovial

membrane

caps

trochlea

coronoid

FIGURE 9.72

Right elbow joint.

Sagittal section.

Anterior view of the interior of the joint.

Medial view.

Lateral view.

408

CHAPTER 9

The triceps muscle, a small bursa

Posteriorly:

median nerve, and the brachial artery

The brachialis, the tendon of the biceps, the

Anteriorly:

Important Relations

angle disappears when the elbow joint is fully flexed.

and is about 170° in the male and 167° in the female. The

carrying angle

angle, which opens laterally, is called the

forearm lies at an angle to the long axis of the arm. This

It should be noted that the long axis of the extended

triceps and anconeus muscles.

and pronator teres muscles. Extension is performed by the

performed by the brachialis, biceps brachii, brachioradialis,

the anterior ligament and the brachialis muscle. Flexion is

is checked by the tension of

Extension

coming into contact.

is limited by the anterior surfaces of the forearm and arm

Flexion

The elbow joint is capable of flexion and extension.

Movements

locutaneous, and radial nerves

Branches from the median, ulnar, muscu

Nerve supply:

membrane of the proximal radioulnar joint.

ranon fossae; it is continuous below with the synovial

fatty pads in the floors of the coronoid, radial, and olec

This lines the capsule and covers

Synovial membrane:

ulnar attachments of the two preceding bands.

non; and the transverse band, which passes between the

condyle of the humerus to the medial side of the olecra

the posterior band, which passes from the medial epi

humerus to the medial margin of the coronoid process;

band, which passes from the medial epicondyle of the

consists principally of three strong bands: the anterior

is also triangular and

medial ligament

lar ligament. The

humerus and by its base to the upper margin of the anu

and is attached by its apex to the lateral epicondyle of the

(Fig. 9.72) is triangular

lateral ligament

The

Ligaments:

process of the ulna and to the anular ligament.

below to the upper margin and sides of the olecranon

The Upper Limb

■

-
-

■

intervening

of the elbow joint. Below it is attached to the inferior

This is continuous above with that

Synovial membrane:

elbow joint. It is not attached to the radius.

(Fig. 9.73). It is continuous above with the capsule of the

ulna and forms a collar around the head of the radius

rior and posterior margins of the radial notch on the

is attached to the ante

anular ligament

The

Ligament:

ous with that of the elbow joint.

The capsule encloses the joint and is continu

Capsule:

Synovial pivot joint

Type:

on the ulna (Figs. 9.72 and 9.73)

the radius and the anular ligament and the radial notch

Between the circumference of the head of

Articulation:

supinator.

The common extensor tendon and the

Laterally:

joint.

epicondyle and crosses the medial ligament of the

ulnar nerve passes behind the medial

The

Medially:

■

Proximal Radioulnar Joint

■

Stability of Elbow Joint

tomic position, is directed medially and posteriorly and faces in

the physician should see that the medial epicondyle, in the ana

condyle is also common in childhood because then the medial

because the parts of the bones that stabilize the joint are incom

Posterior dislocation usually follows falling on the outstretched

Elbow dislocations are common, and most are posterior.

lar surface of the olecranon and the pulley-shaped trochlea of

The elbow joint is stable because of the wrench-shaped articu-

the humerus; it also has strong medial and lateral ligaments.

When examining the elbow joint, the physician must remember

the normal relations of the bony points. In extension, the medial

and lateral epicondyles and the top of the olecranon process are

in a straight line; in flexion, the bony points form the boundaries

of an equilateral triangle.

Dislocations of the Elbow Joint

hand. Posterior dislocations of the joint are common in children

pletely developed. Avulsion of the epiphysis of the medial epi-

ligament is much stronger than the bond of union between the

epiphysis and the diaphysis.

Arthrocentesis of the Elbow Joint

The anterior and posterior walls of the capsule are weak, and

when the joint is distended with fluid, the posterior aspect of the

joint becomes swollen. Aspiration of joint fluid can easily be per-

formed through the back of the joint on either side of the olecra-

non process.

Damage to the Ulnar Nerve with Elbow Joint Injuries

The close relationship of the ulnar nerve to the medial side of

the joint often results in its becoming damaged in dislocations

of the joint or in fracture dislocations in this region. The nerve

lesion can occur at the time of injury or weeks, months, or years

later. The nerve can be involved in scar tissue formation or can

become stretched owing to lateral deviation of the forearm in a

badly reduced supracondylar fracture of the humerus. During

movements of the elbow joint, the continued friction between

the medial epicondyle and the stretched ulnar nerve eventually

results in ulnar palsy.

Radiology of the Elbow Region after Injury

In examining lateral radiographs of the elbow region, it is impor-

tant to remember that the lower end of the humerus is normally

angulated forward 45° on the shaft; when examining a patient,

the same direction as the head of the humerus.

C L I N I C A L N O T E S

Basic Anatomy

to the anatomic position and the palm faces anteriorly.

supination is a reversal of this process so that the hand returns

riorly and the thumb lies on the medial side. The movement of

medially in such a manner that the palm comes to face poste

The movement of pronation results in the hand rotating

supination and pronation.

movement of the hand during the repetitive movements of

ment such as a screwdriver because it prevents side-to-side

movement of the ulna is important when using an instru

with the upper limb and is not displaced medially. This

of the ulna moves laterally so that the hand remains in line

the head of the ulna (Fig. 9.75). In addition, the distal end

notch of the radius moving around the circumference of

of the radius with the hand moves bodily forward, the ulnar

rotates within the anular ligament, whereas the distal end

In the movement of pronation, the head of the radius

the apex of the triangular articular disc below.

through the head of the radius above and the attachment of

the proximal and distal radioulnar joints. The axis passes

arm involve a rotary movement around a vertical axis at

The movements of pronation and supination of the fore

Movements

branch of the radial nerve

Anterior interosseous nerve and the deep

Nerve supply:

the edge of one articular surface to that of the other.

This lines the capsule passing from

Synovial membrane:

from the wrist and strongly unites the radius to the ulna.

9.73 and 9.74). It shuts off the distal radioulnar joint

to the lower border of the ulnar notch of the radius (Figs.

the base of the styloid process of the ulna and by its base

cartilage. It is attached by its apex to the lateral side of

This is triangular and composed of fibro

Articular disc:

strengthen the capsule.

ligaments

posterior

anterior

Weak

Ligaments:

superiorly.

The capsule encloses the joint but is deficient

Capsule:

Synovial pivot joint

Type:

the ulnar notch on the radius (Fig. 9.73)

Between the rounded head of the ulna and

Articulation:

sor tendon

Supinator muscle and the common exten

Posteriorly:

Supinator muscle and the radial nerve

Anteriorly:

Important Relations

Pronation and supination of the forearm (see below)

Movements

locutaneous, and radial nerves

Branches of the median, ulnar, muscu

Nerve supply:

lower margin of the radial notch of the ulna.

margin of the articular surface of the radius and the

409

■

Distal Radioulnar Joint

■

and

■

radial notch of ulna

lateral collateral ligament

annular ligament

olecranon process of ulna

coronoid process of ulna

interosseous membrane

ulna

synovial membrane

triangular
cartilaginous
ligament

styloid process

medial ligament

pisiform

triquetral

joint cavity

interosseous metacarpal

ligaments

interosseous intercarpal ligaments

trapezoid

trapezium

scaphoid

lateral ligament

styloid process

lunate

palmar ligament

collateral ligaments

radius

FIGURE 9.73

Ligaments of the proximal and distal radioulnar joints, wrist joint, carpal joints, and joints of the fingers.

410

CHAPTER 9

The tendon of extensor digiti minimi

Posteriorly:

The tendons of flexor digitorum profundus

Anteriorly:

Important Relations

of supination in right-handed people.

screw and corkscrews are driven inward by the movement

threads and the spiral of corkscrews are made so that the

Because supination is the more powerful movement, screw

movements because of the strength of the biceps muscle.

supinator. Supination is the more powerful of the two

is performed by the biceps brachii and the

Supination

pronator quadratus.

is performed by the pronator teres and the

Pronation

The Upper Limb

■

proximal phalanx

of ring finger

metacarpal

of little finger

fourth dorsal

interosseous

medial ligament

of wrist joint

styloid process of ulna

head of ulna

triquetral

dorsal extensor expansion

extensor digitorum (cut)

extensor indicis (cut)

third metacarpal

extensor pollicis
longus (cut)

first dorsal
interosseous

trapezoid
capitate
hamate
lateral ligament of
wrist joint
styloid process of radius

scaphoid
lunate

shaft of
radius

shaft of ulna

interosseous
membrane

triangular cartilaginous
ligament of wrist joint

FIGURE 9.74

Dissection of the dorsal surface of the left hand and distal end of the forearm. Note the carpal bones and the

intercarpal joints; note also the wrist (radiocarpal) joint.

supination
of forearm

pronation of
forearm

medial
epicondyle
of humerus

coronoid
process
of ulna

styloid
process
of radius

head of
radius

styloid
process
of ulna

supination
of forearm

pronation of
forearm

sty
pro
of r

head of
radius

styloid
process
of ulna

FIGURE 9.75

Movements of supination (

ulna when the forearm is fully pronated.

Relative positions of the radius and the

) of the forearm that take place at the proximal and distal

A) and pronation

radioulnar joints. C.

Radioulnar Joint Disease

infection of the elbow joint invariably involves the proxi

The proximal radioulnar joint communicates with the elbow

joint, whereas the distal radioulnar joint does not communi-

cate with the wrist joint. In practical terms, this means that

mal radioulnar joint. The strength of the proximal radioulnar

joint depends on the integrity of the strong anular ligament.

Rupture of this ligament occurs in cases of anterior disloca-

tion of the head of the radius on the capitulum of the humerus.

In young children, in whom the head of the radius is still small

and undeveloped, a sudden jerk on the arm can pull the radial

head down through the anular ligament.

C L I N I C A L N O T E S

Basic Anatomy

Synovial membrane:

interosseous ligaments.

posterior,

anterior,

The bones are united by strong

Ligaments:

The capsule surrounds each joint.

Capsule:

Synovial plane joints

Type:

bones (Figs. 9.73 and 9.74)

joint, between the proximal and distal rows of carpal

the distal row of the carpus; and finally, the midcarpal

imal row of the carpus; between the individual bones of

Between the individual bones of the prox

Articulation:

Intercarpal Joints

The radial artery

Laterally:

nerve

The posterior cutaneous branch of the ulnar

Medially:

abductor pollicis longus

brevis, the extensor pollicis longus and brevis, and the

extensor indicis, the extensor carpi radialis longus and

the extensor digiti minimi, the extensor digitorum, the

The tendons of the extensor carpi ulnaris,

Posteriorly:

median and ulnar nerves

flexor carpi radialis, the flexor carpi ulnaris, and the

fundus and superficialis, the flexor pollicis longus, the

The tendons of the flexor digitorum pro

Anteriorly:

Important Relations

ulnaris.

is performed by the flexor and extensor carpi

Adduction

pollicis longus and brevis.

are assisted by the abductor pollicis longus and extensor

the extensor carpi radialis longus and brevis. These muscles

is performed by the flexor carpi radialis and

Abduction

and the extensor pollicis longus.

digitorum, the extensor indicis, the extensor digiti minimi,

carpi ulnaris. These muscles are assisted by the extensor

longus, the extensor carpi radialis brevis, and the extensor

is performed by the extensor carpi radialis

Extension

digitorum profundus, and the flexor pollicis longus.

are assisted by the flexor digitorum superficialis, the flexor

flexor carpi ulnaris, and the palmaris longus. These muscles

is performed by the flexor carpi radialis, the

Flexion

of pronation and supination of the forearm.

The lack of rotation is compensated for by the movements

possible because the articular surfaces are ellipsoid shaped.

abduction, adduction, and circumduction. Rotation is

The following movements are possible: flexion, extension,

Movements

branch of the radial nerve

Anterior interosseous nerve and the deep

Nerve supply:

pal joints.

radioulnar joint or with the joint cavities of the intercar

joint cavity does not communicate with that of the distal

attached to the margins of the articular surfaces. The

This lines the capsule and is

Synovial membrane:

scaphoid bone (Figs. 9.73 and 9.74).

attached to the styloid process of the radius and to the

lateral ligament

tral bone (Figs. 9.73 and 9.74). The

to the styloid process of the ulna and to the trique

is attached

medial ligament

strengthen the capsule. The

posterior ligaments

Ligaments: Anterior

to the proximal row of carpal bones.

above to the distal ends of the radius and ulna and below

The capsule encloses the joint and is attached

Capsule:

Synovial ellipsoid joint

Type:

surface.

surface, which is adapted to the distal ellipsoid convex

proximal articular surface forms an ellipsoid concave

and triquetral bones below (Figs. 9.73 and 9.74). The

and the articular disc above and the scaphoid, lunate,

Between the distal end of the radius

Articulation:

Wrist Joint (Radiocarpal Joint)

411

■

and

■

not

■

Joints of the Hand and Fingers

■

and

■

joint cavity of the midcarpal joint extends not only

attached to the margins of the articular surfaces. The

This lines the capsule and is

C L I N I C A L N O T E S

Wrist Joint Injuries

tured about 1 in. (2.5 cm) proximal to the wrist joint (Colles’

distal radial epiphysis; in the teenager the clavicle might

for example, there may be a posterior displacement of the

area affected seems to be related to age. In a young child,

ferent parts of the upper limb give way under the strain. The

and finally, to the sternum. If the forces are excessive, dif

scapula to the coracoclavicular ligament and the clavicle;

ulna to the humerus; thence, through the glenoid fossa of the

across the interosseous membrane to the ulna, and from the

the scaphoid to the distal end of the radius, from the radius

In falls on the outstretched hand, forces are transmitted from

tured scaphoid or dislocation of the lunate bone, which are

joint pain, and limitation of movement. These symptoms and

ligament of the wrist joint, producing synovial effusion,

A fall on the outstretched hand can strain the anterior

joint. The joint is stabilized by the strong medial and lateral

which separates the wrist joint from the distal radioulnar

bones by the strong triangular fibrocartilaginous ligament,

bones. The head of the ulna is separated from the carpal

distal end of the radius and the proximal row of carpal

The wrist joint is essentially a synovial joint between the

ligaments.

Because the styloid process of the radius is longer than

that of the ulna, abduction of the wrist joint is less extensive

than adduction. In flexion–extension movements, the hand

can be flexed about 80° but extended to only about 45°. The

range of flexion is increased by movement at the midcarpal

joint.

signs must not be confused with those produced by a frac-

similar.

Falls on the Outstretched Hand

fracture; in the young adult the scaphoid is commonly frac-

tured; and in the elderly the distal end of the radius is frac-

fracture) (Fig. 9.50).

C L I N I C A L N O T E S

412

CHAPTER 9

and brevis. The movements of abduction and adduction

is performed by the extensor pollicis longus

extension

is performed by the flexor pollicis longus and brevis and

flexion

of the metacarpophalangeal joint of the thumb,

finger is performed by the palmar interossei. In the case

Movement toward the midline of the third

Adduction:

third finger is performed by the dorsal interossei.

Movement away from the midline of the

Abduction:

extensor digiti minimi

Extensor digitorum, extensor indicis, and

Extension:

the flexor digitorum superficialis and profundus

The lumbricals and the interossei, assisted by

Flexion:

The following movements are possible:

Movements

attached to the margins of the articular surfaces.

This lines the capsule and is

Synovial membrane:

when the joint is in extension.

ligaments are taut when the joint is in flexion and lax

acarpal bone to the base of the phalanx. The collateral

passes downward and forward from the head of the met

bands present on each side of the joints (Fig. 9.73). Each

are cord-like

collateral ligaments

bones together. The

which hold the heads of the metacarpal

pal ligaments,

deep transverse metacar

fifth joints are united by the

The palmar ligaments of the second, third, fourth, and

phalanx but less so to the metacarpal bone (Fig. 9.73).

tain some fibrocartilage. They are firmly attached to the

are strong and con

palmar ligaments

The

Ligaments:

The capsule surrounds the joint.

Capsule:

Synovial condyloid joints

Type:

and the bases of the proximal phalanges (Fig. 9.73)

Between the heads of the metacarpal bones

Articulation:

Metacarpophalangeal Joints

by the opponens pollicis.

The thumb is rotated medially

Rotation (opposition):

Adductor pollicis

Adduction:

Abductor pollicis longus and brevis

Abduction:

Extensor pollicis longus and brevis

Extension:

Flexor pollicis brevis and opponens pollicis

Flexion:

The following movements are possible:

Movements

separate joint cavity.

This lines the capsule and forms a

Synovial membrane:

The capsule surrounds the joint.

Capsule:

Synovial saddle-shaped joint

Type:

shaped base of the first metacarpal bone (Fig. 9.73).

Between the trapezium and the saddle-

Articulation:

Carpometacarpal Joint of the Thumb

(Figs. 9.73 and 9.74).

A small amount of gliding movement is possible

interosseous ligaments. They have a common joint cavity.

synovial plane joints possessing anterior, posterior, and

The carpometacarpal and intermetacarpal joints are

Carpometacarpal and Intermetacarpal Joints

A small amount of gliding movement is possible.

Movements

ulnar nerve

branch of the radial nerve, and deep branch of the

Anterior interosseous nerve, deep

Nerve supply:

and downward between the bones of the distal row.

between the individual bones forming the proximal row

between the two rows of carpal bones but also upward

The Upper Limb

■

in the anatomic position.

The following movements are described with the hand

index finger are in contact.

with that of the index finger, and the pulp of the thumb and

such a manner that the plane of the thumbnail lies parallel

the others. The metacarpal bone of the thumb is rotated in

partially flexed, the index finger being flexed as much as

(more so than in the position of rest), and the fingers are

semiprone position, the wrist joint is partially extended

thumb and index finger (Fig. 9.76). The forearm is in the

the hand when it is about to grasp an object between the

is the posture adopted by

position of function

The

nail lies at a right angle to the plane of the other fingernails.

flexed as much as the others; and the plane of the thumb

fingers are partially flexed, although the index finger is not

joint is slightly extended; the second, third, fourth, and fifth

9.76). The forearm is in the semiprone position; the wrist

when the fingers are at rest and the hand is relaxed (Fig.

is the posture adopted by the hand

position of rest

The

the movements of the fingers.

fixator action on the wrist joint, ensuring a stable base for

the flexors and extensors of the carpus can exert a balanced

ing to their best mechanical advantage; at the same time,

long flexor and extensor tendons of the fingers are work

ous membrane is lax. With the wrist partially extended, the

taut; in other positions of the forearm bones, the interosse

midprone position, when the interosseous membrane is

esting to note that the forearm bones are most stable in the

position and the wrist joint is partially extended. It is inter

watch repairing, the forearm is placed in the semiprone

such as those used in the holding of small instruments in

For the hand to be able to perform delicate movements,

Position of the Hand

or her own hand.

is strongly advised to closely observe the movements in his

movements of the hand described in this section, the reader

To comprehend fully the important positioning and

as important as all the remaining fingers combined.

of the first metacarpal bone makes the thumb functionally

between the thumb and index finger. The extreme mobility

action of the thumb, which enables one to grasp objects

Much of the importance of the hand depends on the pincer

upper limb is the important prehensile organ—the hand.

the trunk at the shoulder joint. At the distal end of the

The upper limb is a multijointed lever freely movable on

(Fig. 9.73).

structure similar to that of the metacarpophalangeal joints

Interphalangeal joints are synovial hinge joints that have a

Interphalangeal Joints

are performed at the carpometacarpal joint.

The Hand as a Functional Unit

Basic Anatomy

pal bone; a small amount of movement takes place at the

place mainly between the trapezium and the 1st metacar

other nails (Figs. 9.76 and 9.78A). The movement takes

thumbnail being kept at right angles to the plane of the

oposterior plane away from the palm, the plane of the

is the movement of the thumb in an anter

Abduction

are the extensor pollicis longus and brevis.

phalangeal joints. The muscles producing the movement

metacarpal bone, at the metacarpophalangeal and inter

movement takes place between the trapezium and the 1st

plane of the other fingernails (Figs. 9.76 and 9.77A). The

maintain the plane of the thumbnail at right angles to the

coronal plane away from the palm in such a manner as to

is the movement of the thumb in a lateral or

Extension

the flexor pollicis longus and brevis and the opponens pollicis.

phalangeal joints. The muscles producing the movement are

1st metacarpal bone, at the metacarpophalangeal and inter

The movement takes place between the trapezium and the

right angles to the plane of the other fingernails (Fig. 9.76).

such a manner as to maintain the plane of the thumbnail at

is the movement of the thumb across the palm in

Flexion

Movements of the Thumb

413

position of rest

position of function

flexion of thumb

abduction of thumb

extension of thumb

adduction of thumb

opposition of thumb

FIGURE 9.76

Various positions of the hand and movements of the thumb.

414

CHAPTER 9

anteroposterior plane. The movement takes place at the

is the movement forward of the finger in an

Flexion

Little Fingers

Movements of the Index, Middle, Ring, and

ducing the movement is the opponens pollicis.

the plane of the nail of the opposed finger. The muscle pro

zium. The plane of the thumbnail comes to lie parallel with

metacarpal bone and the attached phalanges on the trape

ment is accomplished by the medial rotation of the 1st

any of the other fingers (Figs. 9.76 and 9.77C). The move

comes into contact with the anterior surface of the tip of

palm in such a manner that the anterior surface of the tip

is the movement of the thumb across the

Opposition

pollicis.

The muscle producing the movement is the adductor

place between the trapezium and the 1st metacarpal bone.

fingernails (Figs. 9.76 and 9.78B). The movement takes

nail being kept at right angles to the plane of the other

oposterior plane toward the palm, the plane of the thumb

is the movement of the thumb in an anter

Adduction

movement are the abductor pollicis longus and brevis.

metacarpophalangeal joint. The muscles producing the

The Upper Limb

-
-

interphalangeal and metacarpophalangeal joints. The distal

placed in a partially opposed position and is also slightly

a deep concavity. To achieve this, the thumb is abducted and

In the cupped position, the palm of the hand is formed into

the metacarpal head, and the collateral ligaments are slack.

base of the phalanx is in contact with the rounded part of

the extended position of the metacarpophalangeal joint, the

by the collateral ligaments, which are taut in this position. In

the metacarpal bone. The two bones are held in close contact

in contact with the flattened anterior surface of the head of

the articular surface of the base of the proximal phalanx lies

in the extended position. In the flexed position of the finger,

Abduction and adduction of the fingers are possible only

producing the movement are the palmar interossei.

takes place at the metacarpophalangeal joint. The muscles

midline of the middle finger (Fig. 9.77B). The movement

is the movement of the fingers toward the

Adduction

tor digiti minimi abducts the little finger.

ducing the movement are the dorsal interossei; the abduc

place at the metacarpophalangeal joint. The muscles pro

middle finger (Figs. 9.69 and 9.77A). The movement takes

the middle finger) away from the imaginary midline of the

is the movement of the fingers (including

Abduction

digiti minimi for the little finger).

by the extensor indicis for the index finger and the extensor

proximal phalanx by the extensor digitorum (in addition,

middle phalanx by the lumbricals and interossei, and the

phalanx is extended by the lumbricals and interossei, the

interphalangeal and metacarpophalangeal joints. The distal

an anteroposterior plane. The movements take place at the

is the movement backward of the finger in

Extension

the proximal phalanx by the lumbricals and the interossei.

middle phalanx by the flexor digitorum superficialis, and

phalanx is flexed by the flexor digitorum profundus, the

-
-

Cupping the Hand

FIGURE 9.77

Left hand with the fingers abducted and the

thumb extended (A), with the fingers adducted and the

thumb adducted (B), and with the thumb in the position of

opposition (C).

FIGURE 9.78

Left hand with the thumb about to move the

and with the thumb about to move the pencil in the direc

pencil away from the palm to demonstrate abduction (A)

tion of the palm to demonstrate adduction (B).

Basic Anatomy

very difficult.)

(Try to make a “strong fist” with the wrist joint flexed—it is

carpi ulnaris muscles must occur to extend the wrist joint.

the extensor carpi radialis longus and brevis and the extensor

ment to be carried out efficiently, a synergic contraction of

long flexor muscles of the fingers and thumb. For this move

fingers and thumb. It is performed by the contraction of the

pophalangeal joints and the interphalangeal joints of the

Making a fist is accomplished by flexing the metacar

joints to increase the general concavity of the cupped hand.

the fingers are also rotated slightly at the metacarpophalangeal

The index, middle, ring, and little fingers are partially flexed;

which improves the gripping ability of the palm.

the hypothenar eminence medially; it also puckers the skin,

palmaris brevis muscle contracts and pulls the skin over

effect of drawing the hypothenar eminence forward. The

slightly rotated at the carpometacarpal joints. This has the

The 4th and 5th metacarpal bones are flexed and

forward.

flexed. This has the effect of drawing the thenar eminence

415

Making a Fist

Diseases of the Hand and Preservation of Function

ing the thumb) is normally flexed into the palm, it points to the

From the clinical standpoint, the hand is one of the most impor-

tant organs of the body. Without a normally functioning hand, the

patient’s livelihood is often in jeopardy. To students who doubt

this statement, I would suggest that they place their right (or

left) hand in a pocket for 24 hours. They will be astonished at the

number of times they would like to use it if they could.

From the purely mechanical point of view, the hand can be

regarded as a pincer-like mechanism between the thumb and

fingers, situated at the end of a multijointed lever. The most

important part of the hand is the thumb, and it is the physician’s

responsibility to preserve the thumb, or as much of it as possible,

so that the pincer-like mechanism can be maintained. The pin-

cer-like action of the thumb largely depends on its unique ability

to be drawn across the palm and opposed to the other fingers.

This movement alone, although important, is insufficient for the

mechanism to work effectively. The opposing skin surfaces must

have tactile sensation—and this explains why median nerve

palsy is so much more disabling than ulnar nerve palsy.

If the hand requires immobilization for the treatment of dis-

ease of any part of the upper limb, it should be immobilized (if

possible) in the position of function. This means that if loss of

movement occurs at the wrist joint, or at the joints of the hand or

fingers, the patient will at least have a hand that is in a position of

mechanical advantage, and one that can serve a useful purpose.

Physicians should also remember that when a finger (exclud-

tubercle of the scaphoid; individual fingers requiring immobili-

zation in flexion, on a splint or within a cast, should therefore

always be placed in this position.

Always refer to the patient’s fingers by name: thumb, index,

middle, ring, and little finger. Numbering the fingers is confusing

(is the thumb a finger?) and has led to such disastrous results as

amputating the wrong finger.

C L I N I C A L N O T E S

Development of the Upper Limb

may occur. A defective limb may possess a rudimen

that migrate within each limb. As a consequence of these two

terior groups, and the nerve trunks entering the base of each

whereas the mesenchyme of the postaxial border becomes asso

associated and innervated with the lower five cervical nerves,

The mesenchyme situated along the preaxial border becomes

opposite the bases of the limb buds start to grow into the limbs.

limb buds elongate, the anterior rami of the spinal nerves situated

As the

and upper two thoracic segments. The flattened limb buds have

before the leg buds and lie at the level of the lower six cervical

two pairs of flattened paddles (Fig. 9.79). The arm buds develop

This causes the overlying ectoderm to bulge from the trunk as

result of a localized proliferation of somatopleuric mesenchyme.

The limb buds appear during the sixth week of development as the

a cephalic preaxial border and a caudal postaxial border.

ciated with the 8th cervical and 1st thoracic nerves.

Later, the mesenchymal masses divide into anterior and pos-

limb also divide into anterior and posterior divisions. The mes-

enchyme within the limbs differentiates into individual muscles

factors, the anterior rami of the spinal nerves become arranged

in complicated plexuses that are found near the base of each

limb so that the brachial plexus is formed.

Amelia
Absence of one or more limbs (amelia) or partial absence (ectro-
melia)

tary hand at the extremity of the limb or a well-developed hand

E M B R Y O L O G I C N O T E S

(continued)