The forearm pdf - Upper limb

380

CHAPTER 9

The Upper Limb

Fractures of the Radius and Ulna

A small subcutaneous bursa is present over the olecranon pro

Colles’ fracture because the distal fragment is displaced anteri

is a fracture of the distal end of the radius

Colles’ fracture

process can be produced by the pull of the triceps muscle. Good

the pull of the triceps muscle, which is inserted on the olecranon

the proximal third of the radius is fractured

Galeazzi’s fracture,

the shaft of the ulna is fractured by a force applied from behind.

supination, the normal anatomic relationship of the radius, ulna,

fragment of the radius is pronated and pulled medially by the

can occur from falls on the

Fractures of the head of the radius

outstretched hand. As the force is transmitted along the radius,

the head of the radius is driven sharply against the capitulum,

splitting or splintering the head (Fig. 9.10).

Fractures of the neck of the radius occur in young children

from falls on the outstretched hand (Fig. 9.10).

Fractures of the shafts of the radius and ulna may or may

not occur together (Fig. 9.10). Displacement of the fragments is

usually considerable and depends on the pull of the attached

muscles. The proximal fragment of the radius is supinated by the

supinator and the biceps brachii muscles (Fig. 9.10). The distal

pronator quadratus muscle. The strength of the brachioradialis

and extensor carpi radialis longus and brevis shortens and angu-

lates the forearm. In fractures of the ulna, the ulna angulates

posteriorly. To restore the normal movements of pronation and

and interosseous membrane must be regained.

A fracture of one forearm bone may be associated with a dis-

location of the other bone. In Monteggia’s fracture, for example,

There is a bowing forward of the ulnar shaft and an anterior dis-

location of the radial head with rupture of the anular ligament. In

and the distal end of the ulna is dislocated at the distal radioulnar

joint.

Fractures of the olecranon process can result from a fall on

the flexed elbow or from a direct blow. Depending on the loca-

tion of the fracture line, the bony fragment may be displaced by

process (Fig. 9.10). Avulsion fractures of part of the olecranon

functional return after any of these fractures depends on the

accurate anatomic reduction of the fragment.

resulting from a fall on the outstretched hand. It commonly

occurs in patients older than 50 years. The force drives the dis-

tal fragment posteriorly and superiorly, and the distal articular

surface is inclined posteriorly (Fig. 9.50). This posterior displace-

ment produces a posterior bump, sometimes referred to as the

“dinner-fork deformity” because the forearm and wrist resemble

the shape of that eating utensil. Failure to restore the distal artic-

ular surface to its normal position will severely limit the range of

flexion of the wrist joint.

Smith’s fracture is a fracture of the distal end of the radius

and occurs from a fall on the back of the hand. It is a reversed

orly (Fig. 9.50).

Olecranon Bursitis

cess of the ulna, and repeated trauma often produces chronic

bursitis.

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

FIGURE 9.50

Fractures of the distal end of the radius.

of the medial cutaneous nerve of the forearm (Fig. 9.38).

neous nerve, and from the anterior and posterior branches

nerve of the forearm, a continuation of the musculocuta

the anterior and posterior branches of the lateral cutaneous

to the skin of the forearm is from

sensory nerve supply

The

hand and fingers are shown in Figures 9.51 and 9.52.

The important muscles attached to the bones of the

only two for the thumb.

There are three phalanges for each of the fingers but

surfaces are posterior, lateral, and medial.

concave forward and is triangular in transverse section. Its

and 9.52). The shaft of each metacarpal bone is slightly

knuckles, articulate with the proximal phalanges (Figs. 9.51

distal row of the carpal bones; the heads, which form the

The bases of the metacarpal bones articulate with the

surface is directed laterally and not backward.

rotated medially through a right angle so that its extensor

the others but occupies a more anterior position. It is also

est and most mobile. It does not lie in the same plane as

The first metacarpal bone of the thumb is the short

(Figs. 9.51 and 9.52).

head

There are five metacarpal bones, each of which has a

Smith’s fracture.

Colles’ fracture.

The Metacarpals and Phalanges

base,

a shaft, and a

The Forearm

Skin

A narrow strip of skin down the middle of the

ior

poster

surface of the forearm is supplied by the posterior cutaneous

lateral side of the dorsal venous arch on the back of the

arises from the

cephalic vein

ficial fascia (Fig. 9.39). The

of the forearm lie in the super

superficial veins

The

nerve of the forearm.

Basic Anatomy

381

scaphoid

trapezoid

tubercle of scaphoid

abductor pollicis brevis

flexor pollicis brevis

opponens pollicis

ridge of trapezium

abductor pollicis longus

oblique head of adductor pollicis

first palmar interosseous

flexor carpi radialis

opponens pollicis

second palmar interosseous

abductor and

flexor pollicis brevis

adductor pollicis and

first palmar interosseous

transverse head of

adductor pollicis

flexor pollicis longus

thumb

palmar interossei

flexor digitorum superficialis

index

flexor digitorum profundus

middle

ring

little

third palmar interosseous

abductor and

flexor digiti minimi

fourth palmar interosseous

opponens digiti minimi

pisometacarpal ligament

hook of hamate

flexor digiti minimi

pisohamate ligament

abductor digiti minimi

pisiform

flexor carpi ulnaris

triquetral

hamate

lunate

capitate

FIGURE 9.51

Important muscular attachments to the anterior surfaces of the bones of the hand.

lunate

triquetral

pisiform

capitate

hamate

extensor carpi ulnaris

fourth dorsal interosseous

third dorsal interosseous

second dorsal interosseous

dorsal interossei

extensor expansion

for extensor digitorum

extensor pollicis longus

adductor pollicis

extensor pollicis

brevis

first dorsal interosseous

extensor carpi radialis brevis

extensor carpi radialis longus

trapezium

trapezoid

scaphoid

FIGURE 9.52

Important muscular attachments to the posterior surfaces of the bones of the hand.

382

CHAPTER 9

blood supply.

compartments, each having its own muscles, nerves, and

intermuscular septa, divides the forearm into several

together with the interosseous membrane and fibrous

neous border of the ulna (Fig. 9.53). This fascial sheath,

is attached to the periosteum of the posterior subcuta

The forearm is enclosed in a sheath of deep fascia, which

also drain into the lateral axillary nodes (Fig. 9.40).

nodes. The efferent vessels from the supratrochlear node

axilla, where they drain into the lateral group of axillary

ers bypass the node and accompany the basilic vein to the

whereas oth

supratrochlear lymph node,

drain into the

basilic vein to the cubital fossa. Here, some of the vessels

the medial areas of the hand and the forearm follow the

of nodes (Fig. 9.40). Those from the medial fingers and

arm follow the cephalic vein to the infraclavicular group

lateral fingers and the lateral areas of the hand and fore

from the thumb and

superficial lymph vessels

The

posterior surfaces of the upper limb.

and a variable number of tributaries from the medial and

is described on page 351. It receives the median cubital vein

comitantes of the brachial artery to form the axillary vein,

the biceps (Fig. 9.39). Its termination, by joining the venae

tal fossa and up the front of the arm on the medial side of

medial border of the forearm; it then ascends into the cubi

venous arch on the back of the hand and winds around the

arises from the medial side of the dorsal

basilic vein

The

them by the bicipital aponeurosis.

chial artery and the median nerve, but it is separated from

tal fossa, the median cubital vein crosses in front of the bra

upward and medially and joins the basilic vein. In the cubi

a branch of the cephalic vein in the cubital fossa, runs

vein,

median cubital

terior surfaces of the limb (Fig. 9.39). The

a variable number of tributaries from the lateral and pos

As the cephalic vein passes up the upper limb, it receives

axillary vein in the deltopectoral triangle (see page 419).

arm on the lateral side of the biceps. It terminates in the

then ascends into the cubital fossa and up the front of the

hand and winds around the lateral border of the forearm; it

The Upper Limb

-
-

Fascial Compartments of the Forearm

Injuries to the Bones of the Hand

direct violence, such as the clenched fist striking a hard object.

adults who fall on the outstretched hand in a way that causes

outstretched hand in a young adult makes one suspicious of a

Fracture of the scaphoid bone is common in young adults; unless

treated effectively, the fragments will not unite, and permanent

weakness and pain of the wrist will result, with the subsequent

development of osteoarthritis. The fracture line usually goes

through the narrowest part of the bone, which, because of its

location, is bathed in synovial fluid. The blood vessels to the

scaphoid enter its proximal and distal ends, although the blood

supply is occasionally confined to its distal end. If the latter

occurs, a fracture deprives the proximal fragment of its arte-

rial supply, and this fragment undergoes avascular necrosis.

Deep tenderness in the anatomic snuffbox after a fall on the

fractured scaphoid.

Dislocation of the lunate bone occasionally occurs in young

hyperextension of the wrist joint. Involvement of the median

nerve is common.

Fractures of the metacarpal bones can occur as a result of

The fracture always angulates dorsally. The “boxer’s fracture”

commonly produces an oblique fracture of the neck of the fifth

and sometimes the fourth metacarpal bones. The distal fragment

is commonly displaced proximally, thus shortening the finger

posteriorly.

Bennett’s fracture is a fracture of the base of the metacarpal

of the thumb caused when violence is applied along the long axis

of the thumb or the thumb is forcefully abducted. The fracture is

oblique and enters the carpometacarpal joint of the thumb, caus-

ing joint instability.

Fractures of the phalanges are common and usually follow

direct injury.

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

Compartment Syndrome of the Forearm

diagnosis is made, the deep fascia must be incised surgically

by pressure on the arteries within the compartment). Once the

by edema), and absence of capillary refill in the nail beds (caused

tenderness of the skin over the compartment (a late sign caused

that pass through the compartment (caused by muscle ischemia),

within the compartment), pain on passive stretching of muscles

pain disproportionate to any injury (caused by pressure on nerves

emia of the sensory nerves passing through the compartment),

Soft tissue injury is a common cause, and early diagnosis is

of the ulna (Fig. 9.53). This fascial sheath, together with the inter

The forearm is enclosed in a sheath of deep fascia, which is

attached to the periosteum of the posterior subcutaneous border

osseous membrane and fibrous intermuscular septa, divides the

forearm into several compartments, each having its own mus-

cles, nerves, and blood supply. There is very little room within

each compartment, and any edema can cause secondary vascu-

lar compression of the blood vessels; the veins are first affected,

and later the arteries.

critical. Early signs include altered skin sensation (caused by isch-

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

(continued)

Basic Anatomy

and the flexor tendons of the thumb and fingers (Fig. 9.54).

for the passage of the median nerve

carpal tunnel,

nel, the

cave anterior surface of the hand into an osteofascial tun

stretches across the front of the wrist and converts the con

holds the long flexor tendons in position at the wrist. It

The flexor retinaculum is a thickening of deep fascia that

Flexor Retinaculum

position at the wrist.

fascia that hold the long flexor and extensor tendons in

The flexor and extensor retinacula are strong bands of deep

Flexor and Extensor Retinacula

muscles.

seous membrane provides attachment for neighboring

position—that is, the position of function. The interos

Its fibers are taut when the forearm is in the midprone

to the ulna and from there to the humerus and scapula.

the outstretched hand) is transmitted from the radius

applied to the lower end of the radius (e.g., falling on

ers run obliquely downward and medially so that a force

to their interosseous borders (Figs. 9.49 and 9.53). Its fib

unites the shafts of the radius and the ulna; it is attached

The interosseous membrane is a strong membrane that

Interosseous Membrane

383

-
-

to decompress the affected compartment. A delay of as little as

langeal joints are extended, and the interphalangeal joints

Both the flexor and extensor muscles of the forearm are

4 hours can cause irreversible damage to the muscles.

Volkmann’s Ischemic Contracture

Volkmann’s ischemic contracture is a contracture of the mus-

cles of the forearm that commonly follows fractures of the distal

end of the humerus or fractures of the radius and ulna. In this

syndrome, a localized segment of the brachial artery goes into

spasm, reducing the arterial flow to the flexor and the exten-

sor muscles so that they undergo ischemic necrosis. The flexor

muscles are larger than the extensor muscles, and they are

therefore the ones mainly affected. The muscles are replaced

by fibrous tissue, which contracts, producing the deformity. The

arterial spasm is usually caused by an overtight cast, but in some

cases the fracture itself may be responsible. The deformity can

be explained only by understanding the anatomy of the region.

Three types of deformity exist:

■

The long flexor muscles of the carpus and fingers are more

contracted than the extensor muscles, and the wrist joint is

flexed; the fingers are extended. If the wrist joint is extended

passively, the fingers become flexed.

■

The long extensor muscles to the fingers, which are inserted

into the extensor expansion that is attached to the proximal

phalanx, are greatly contracted; the metacarpophalangeal

joints and the wrist joint are extended, and the interphalan-

geal joints of the fingers are flexed.

■

contracted. The wrist joint is flexed, the metacarpopha-

are flexed.

palmaris longus

ulnar nerve and artery

flexor carpi ulnaris

anterior interosseous

nerve and artery

flexor digitorum profundus

ulna

extensor pollicis longus

extensor carpi ulnaris

extensor digiti minimi

posterior interosseous nerve and artery

abductor pollicis longus

supinator

radius

extensor digitorum

extensor carpi

radialis brevis

extensor carpi

radialis longus

brachioradialis

flexor pollicis

longus

pronator teres

superficial branch of

radial nerve

radial artery

flexor carpi radialis

median nerve

flexor digitorum superficialis

FIGURE 9.53

Cross section of the forearm at the level of insertion of the pronator teres muscle.

384

CHAPTER 9

from one another by fibrous septa that pass from the deep

retinaculum on the tendons. The tunnels are separated

with a synovial sheath, which extends above and below the

passage of the long extensor tendons. Each tunnel is lined

ends of the radius and ulna into six separate tunnels for the

It converts the grooves on the posterior surface of the distal

long extensor tendons in position (Figs. 9.56 and 9.57).

that stretches across the back of the wrist and holds the

The extensor retinaculum is a thickening of deep fascia

Extensor Retinaculum

(Fig. 9.55).

The lower border is attached to the palmar aponeurosis

and is continuous with the deep fascia of the forearm.

to the distal transverse skin crease in front of the wrist

The upper border of the retinaculum corresponds

radialis.

lined tunnel for passage of the tendon of the flexor carpi

consists of superficial and deep parts and forms a synovial-

and the trapezium bones. The attachment to the trapezium

of the hamate and laterally to the tubercle of the scaphoid

It is attached medially to the pisiform bone and the hook

The Upper Limb

surface of the retinaculum to the bones.

bone and the hook of the hamate and laterally to the

The retinaculum is attached medially to the pisiform

distal end of the radius. The upper and lower borders of

the retinaculum are continuous with the deep fascia of the

nerve.

digitorum profundus, which are supplied by the ulnar

flexor carpi ulnaris and the medial part of the flexor

plied by the median nerve and its branches, except the

All the muscles are sup

Nerve supply to the muscles:

Ulnar and radial arteries

Blood supply to the muscles:

digitorum profundus, and the pronator quadratus

consisting of the flexor pollicis longus, the flexor

group

deep

sisting of the flexor digitorum superficialis; and a

con

intermediate group

and the flexor carpi ulnaris; an

tor teres, the flexor carpi radialis, the palmaris longus,

consisting of the prona

superficial group,

Muscles:

of the Forearm

Contents of the Anterior Fascial Compartment

further details, see page 398.

rum superficialis and the flexor carpi radialis muscles. For

between the tendons of the flexor digito

restricted space

the carpal tunnel (Fig. 9.54). The median nerve lies in a

The bones of the hand and the flexor retinaculum form

Carpal Tunnel

naculum are described on page 397.

The contents of the tunnels beneath the extensor reti

forearm and hand, respectively.

■

palmaris longus

flexor retinaculum

palmar cutaneous branch

of ulnar nerve

muscles of

hypothenar eminence

ulnar artery
ulnar nerve

flexor digitorum

superficialis

flexor digitorum

profundus

hook of hamate

flexor synovial sheath

extensor carpi ulnaris

posterior cutaneous branch of

ulnar nerve

basilic vein

extensor digiti minimi

extensor digitorum

extensor indicis

extensor retinaculum

extensor pollicis longus

extensor carpi radialis

longus and brevis

cephalic vein

radial artery

superficial branch

of radial nerve

extensor pollicis brevis

abductor pollicis longus

flexor pollicis longus

ridge of trapezium

flexor carpi radialis

muscles of thenar eminence

palmar cutaneous branch of median nerve

median nerve

hamate

capitate

trape-

zoid

trap

FIGURE 9.54

xor and extensor

Cross section of the hand showing the relation of the tendons, nerves, and arteries to the fle

retinacula.

Basic Anatomy

385

fibrous flexor sheath

deep transverse palmar ligament

palmar aponeurosis

abductor digiti minimi

flexor digiti minimi

deep branch of ulnar nerve and artery

palmaris brevis

hook of hamate

pisiform

palmar cutaneous branchof ulnar nerve

flexor carpi ulnaris

ulnar nerve

ulnar artery

flexor digitorum superficialis

palmaris longus

median nerve

palmar cutaneous branch

of median nerve

flexor carpi radialis

radial artery

tubercle of scaphoid

abductor pollicis longus

extensor pollicis brevis

ridge of trapezium

flexor retinaculum

flexor pollicis brevis

abductor pollicis brevis

adductor pollicis

first dorsal interosseous

palmar digital nerve

palmar digital artery

FIGURE 9.55

Anterior view of the palm of the hand. The palmar aponeurosis has been left in position.

extensor indicis

first dorsal interosseous

extensor pollicis longus

extensor pollicis brevis

abductor pollicis longus

extensor carpi radialis longus

extensor carpi radialis brevis

extensor digitorum

extensor digiti minimi

extensor carpi ulnaris

extensor retinaculum

extensor digiti minimi

extensor digitorum

dorsal extensor expansion

FIGURE 9.56

Dorsal surface of the hand showing the long extensor tendons and their synovial sheaths.

386

CHAPTER 9

The Upper Limb

extensor

digitorum

extensor
expansion

extensor
digitorum

extensor
digiti
minimi

extensor
retinaculum

extensor
pollicis
longus

extensor
carpi
ulnaris
extensor
digitorum

ulna

fourth
dorsal
interosseous

extensor

indicis

digital

vein

first

dorsal

interosseous

radial

artery

extensor

pollicis

longus

abductor

pollicis

longus

extensor

pollicis

brevis

extensor

pollicis

brevis

radius

FIGURE 9.57

Dissection of the dorsal surface of the right hand showing the long extensor tendons and the extensor retinaculum.

Absent Palmaris Longus

The palmaris longus muscle may be absent on one or both

sides of the forearm in about 10% of persons. Others show

variation in form, such as centrally or distally placed muscle

belly in the place of a proximal one. Because the muscle is

relatively weak, its absence produces no disability.

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

Muscles of the Anterior Fascial Compartment of

minal branches of the brachial artery (Figs. 9.42 and 9.60).

The ulnar artery is the larger of the two ter

Ulnar Artery

the Forearm

Arteries of the Anterior Fascial Compartment of

epicondyle of the humerus.

common tendon of origin, which is attached to the medial

9.6. Note that the superficial group of muscles possesses a

Figures 9.58, 9.59, 9.60, and 9.61 and are described in Table

The muscles of the anterior fascial compartment are seen in

the Forearm

Basic Anatomy

bone and is covered only by skin and fascia (site for taking

of the flexor retinaculum, it lies just lateral to the pisiform

the tendons of the flexor digitorum superficialis. In front

and lies between the tendons of the flexor carpi ulnaris and

to most of the flexor muscles. Below, it becomes superficial

In the upper part of its course, the ulnar artery lies deep

artery (Fig. 9.62).

tomosing with the superficial palmar branch of the radial

often anas

superficial palmar arch,

It ends by forming the

retinaculum in company with the ulnar nerve (Fig. 9.62).

the flexor

in front of

of the forearm and enters the palm

the radius. It descends through the anterior compartment

It begins in the cubital fossa at the level of the neck of

387

ulnar pulse).

Muscles of the Anterior Fascial Compartment of the Forearm

T A B L E 9 . 6

Pronator Teres

Muscle

Origin

Insertion

Nerve Supply

Nerve
Roots

Action

Humeral head

Medial epicondyle of

humerus

Lateral aspect of shaft

of radius

Median nerve

C6, 7

Pronation and flexion of

forearm

Ulnar head

Medial border of

coronoid process of

ulna

Flexor carpi

radialis

Medial epicondyle of

humerus

Bases of second and

third metacarpal

bones

Median nerve

C6, 7

Flexes and abducts

hand at wrist joint

Palmaris

longus

Medial epicondyle of

humerus

Flexor retinaculum and

palmar aponeurosis

Median nerve

C7, 8

Flexes hand

Flexor Carpi Ulnaris
Humeral head

Medial epicondyle of

humerus

Pisiform bone, hook of

the hamate, base at

fifth metacarpal bone

Ulnar nerve

C8; T1

Flexes and adducts

hand at wrist joint

Ulnar head

Medial aspect of

olecranon process

and posterior border

of ulna

Flexor Digitorum Superficialis
Humeroulnar

head

Medial epicondyle of

humerus; medial

border of coronoid

process of ulna

Middle phalanx of

medial four fingers

Median nerve

C7, 8; T1

Flexes middle phalanx

of fingers and assists

in flexing proximal

phalanx and hand

Radial head

Oblique line on anterior

surface of shaft of

radius

Flexor pollicis

longus

Anterior surface of shaft

of radius

Distal phalanx of thumb

Anterior interosseous

branch of median

nerve

C8; T1

Flexes distal phalanx of

thumb

Flexor

digitorum

profundus

Anteromedial surface of

shaft of ulna

Distal phalanges of

medial four fingers

Ulnar (medial half)

and median (lateral

half) nerves

C8; T1

Flexes distal phalanx

of fingers; then

assists in flexion of

middle and proximal

phalanges and wrist

Pronator

quadratus

Anterior surface of shaft

of ulna

Anterior surface of shaft

of radius

Anterior interosseous

branch of median

nerve

C8; T1

Pronates forearm

The predominant nerve root supply is indicated by boldface type.

388

CHAPTER 9

and

anterior

divides into the

the upper part of the ulnar artery and after a brief course

which arises from

common interosseous artery,

The

around the wrist joint

Branches that take part in the arterial anastomosis

mosis around the elbow joint (Fig. 9.61)

that take part in the arterial anasto

Recurrent branches

to neighboring muscles

Muscular branches

Branches

The Upper Limb

■

posterior

osseous

inter

(Fig. 9.61). The interosseous arteries are

arteries
distributed to the muscles lying in front of and behind

its lateral side.

course, the superficial branch of the radial nerve lies on

deep muscles of the forearm. In the middle third of its

beneath the brachioradialis muscle and resting on the

9.58, 9.59, and 9.60). It passes downward and laterally,

cubital fossa at the level of the neck of the radius (Figs.

minal branches of the brachial artery. It begins in the

The radial artery is the smaller of the ter

Radial Artery

ies to the radius and ulna bone.

the interosseous membrane; they provide nutrient arter-

musculocutaneous nerve becoming
lateral cutaneous nerve of forearm

brachioradialis

extensor carpi radialis longus

biceps tendon

extensor carpi radialis brevis

supinator

superficial branch of radial nerve

pronator teres

abductor pollicis longus

radial artery

extensor pollicis brevis

pronator quadratus

abductor pollicis longus

radius

flexor retinaculum

median nerve

ulnar nerve and artery

flexor digitorum superficialis

flexor carpi ulnaris

palmaris longus

flexor carpi radialis

bicipital aponeurosis

ulnar artery

pronator teres

medial intermuscular septum

median nerve

brachial artery

brachialis

biceps brachii

FIGURE 9.58

he middle portion of the brachioradialis muscle has been removed to display the

Anterior view of the forearm. T

superficial branch of the radial nerve and the radial artery.

Basic Anatomy

389

palmar
digital arteries
and nerves

flexor pollicis
brevis

abductor pollicis
brevis

abductor digiti
minimi

abductor pollicis
longus

flexor
retinaculum

radial artery

flexor carpi
radialis

brachioradialis

flexor digitorum
superficialis

tendons of
flexor digitorum
superficialis

median nerve

ulnar artery

pisiform bone

ulnar nerve

superficial palmar
arch

fibrous flexor
sheath

FIGURE 9.59

uctures.

Dissection of the front of the left forearm and hand showing the superficial str

(Fig. 9.61). It ends on the anterior surface of the carpus.

flexor pollicis longus and the flexor digitorum profundus

anterior surface of the interosseous membrane, between the

two heads of the pronator teres. It passes downward on the

arises from the median nerve as it emerges from between the

The anterior interosseous nerve

Anterior Interosseous Nerve

lateral part of the palm (Fig. 9.38).

of the forearm and is distributed to the skin over the

This arises in the lower part

Palmar cutaneous branch.

Anterior interosseous nerve

to the elbow joint

Articular branches

the flexor digitorum superficialis (Fig. 9.22)

teres, the flexor carpi radialis, the palmaris longus, and

in the cubital fossa to the pronator

Muscular branches

Branches

the flexor retinaculum (see pages 394

behind

longus (Figs. 9.58, 9.59, and 9.60). It enters the palm by

cialis muscle and lies behind the tendon of the palmaris

from the lateral border of the flexor digitorum superfi

itorum profundus. At the wrist, the median nerve emerges

torum superficialis and rests posteriorly on the flexor dig

(Fig. 9.60). It continues downward behind the flexor digi

by passing between the two heads of the pronator teres

The median nerve leaves the cubital fossa

Median Nerve

the Forearm

Nerves of the Anterior Fascial Compartment of

palmar arch

superficial

quently joins the ulnar artery to form the

wrist (Fig. 9.60), enters the palm of the hand, and fre

which arises just above the

Superficial palmar branch,

tomosis around the elbow joint (Fig. 9.60)

which takes part in the arterial anas

Recurrent branch,

to neighboring muscles

Muscular branches

Branches in the Forearm

of the hand (see page 406).

the lateral aspect of the wrist to reach the posterior surface

The radial artery leaves the forearm by winding around

carpi radialis on its medial side (site for taking the radial

chioradialis on its lateral side and the tendon of flexor

by skin and fascia. Here, the artery has the tendon of bra

on the anterior surface of the radius and is covered only

In the distal part of the forearm, the radial artery lies

pulse).

■

passing

and 395).

■

390

CHAPTER 9

to the elbow joint

Articular branches

(Fig. 9.23)

to the medial half of the flexor digitorum profundus

to the flexor carpi ulnaris and

Muscular branches

Branches

here, it has the ulnar artery lateral to it (see page 394).

the flexor retinaculum and lateral to the pisiform bone;

in front

ulnar nerve enters the palm of the hand by passing

digitorum superficialis muscles (Figs. 9.58 and 9.59). The

between the tendons of the flexor carpi ulnaris and flexor

At the wrist, the ulnar nerve becomes superficial and lies

artery lies on the lateral side of the ulnar nerve (Fig. 9.61).

muscles. In the distal two thirds of the forearm, the ulnar

flexor carpi ulnaris and the flexor digitorum profundus

carpi ulnaris. It then runs down the forearm between the

the forearm by passing between the two heads of the flexor

medial ligament of the elbow joint, and enters the front of

behind the medial epicondyle of the humerus, crosses the

The ulnar nerve (Fig. 9.61) passes from

Ulnar Nerve

joints. It also supplies the joints of the hand.

to the wrist and distal radioulnar

Articular branches

rum profundus

nator quadratus, and the lateral half of the flexor digito

to the flexor pollicis longus, the pro

Muscular branches

Branches

The Upper Limb

■

-
-

■

biceps brachii

brachioradialis

extensor carpi radialis longus

radial recurrent artery

deep branch of radial nerve

extensor carpi radialis brevis

radial artery

supinator

superficial branch of radial nerve

brachioradialis

flexor pollicis longus

median nerve

abductor pollicis longus

radial artery

pronator quadratus

ulnar artery

ulnar nerve

posterior cutaneous branch of ulnar nerve

flexor digitorum profundus

flexor carpi ulnaris

radial head of flexor digitorum superficialis

humeral head of flexor digitorum superficialis

median nerve

ulnar head of pronator teres

flexor carpi radialis

humeral head of pronator teres

brachial artery

medial intermuscular septum

brachialis

ulnar artery

FIGURE 9.60

e been removed to display the flexor digitorum

Anterior view of the forearm. Most of the superficial muscles hav

teres separates the median nerve from the ulnar artery.

superficialis, median nerve, superficial branch of the radial nerve, and radial artery. Note that the ulnar head of the pronator

Basic Anatomy

Brachioradialis and extensor carpi radialis

Muscles:

the posterior fascial compartment.

The lateral fascial compartment may be regarded as part of

the Forearm

Contents of the Lateral Fascial Compartment of

surface of the hand and fingers.

ulnaris and the ulna and is distributed on the posterior

passes medially between the tendon of the flexor carpi

branch that arises in the distal third of the forearm. It

is a large

dorsal posterior cutaneous branch

The

plies the skin over the hypothenar eminence.

arises in the middle of the forearm (Fig. 9.38) and sup

is a small branch that

palmar cutaneous branch

The

391

■

longus

Radial and brachial arteries

Blood supply:

■

brachialis

radial nerve

lateral epicondyle

radial artery

superficial

branch of radial nerve

oblique cord

supinator

deep branch of radial nerve

radial head of flexor

digitorum superficialis

pronator teres

interosseous membrane

flexor pollicis longus

abductor pollicis longus

branch of anterior

interosseous artery

pronator quadratus

anterior interosseous nerve

anterior interosseous artery

flexor digitorum profundus

ulnar artery

ulnar nerve

posterior interosseous artery

common interosseous artery

posterior ulnar recurrent artery

medial epicondyle

anterior ulnar recurrent artery

median nerve

brachial artery

FIGURE 9.61

uctures.

Anterior view of the forearm showing the deep str

392

CHAPTER 9

the neck of the radius, within the supinator muscle

This winds around

Deep branch of the radial nerve.

to the elbow joint

Articular branches

eral part of the brachialis muscle (Fig. 9.25)

sor carpi radialis longus, and a small branch to the lat

to the brachioradialis, to the exten

Muscular branches

Branches

(Figs. 9.60 and 9.61).

epicondyle, it divides into superficial and deep branches

on the lateral side (Fig. 9.60). At the level of the lateral

and the brachioradialis and extensor carpi radialis longus

humerus, lying between the brachialis on the medial side

passes downward in front of the lateral epicondyle of the

passes forward into the cubital fossa (Fig. 9.47). It then

muscular septum in the lower part of the arm and

The radial nerve pierces the lateral inter

Radial Nerve

Nerve of the Lateral Compartment of the Forearm

and brachial arteries.

The arterial supply is derived from branches of the radial

Forearm

Arteries of the Lateral Compartment of the

Table 9.7.

arm are seen in Figures 9.58 and 9.60 and are described in

The muscles of the lateral fascial compartment of the fore

Forearm

Muscles of the Lateral Fascial Compartment of the

Radial nerve

Nerve supply to the muscles:

The Upper Limb

■

-
-

■

(Fig. 9.61), and enters the posterior compartment of the

the tendon of the brachioradialis (Fig. 9.60). It reaches the

forearm, it leaves the artery and passes backward under

the lateral side of the radial artery. In the distal part of the

It runs down under cover of the brachioradialis muscle on

front of the lateral epicondyle of the humerus (Fig. 9.60).

nerve after its main stem has given off its deep branch in

branch of the radial nerve is the direct continuation of the

The superficial

Superficial Branch of the Radial Nerve

Superficial branch of the radial nerve

forearm (Fig. 9.61).

■

posterior surface of the wrist, where it divides into terminal

rior surface over the proximal phalanges of the lateral three

the posterior surface of the hand (Fig. 9.38) and the poste

branches that supply the skin on the lateral two thirds of

fibrous flexor sheaths

flexor digitorum superficialis

flexor digitorum profundus

palmar digital arteries and nerves

opponens digiti minimi

superficial palmar arch

flexor digiti minimi

abductor digiti minimi

hook of hamate

pisiform

flexor carpi ulnaris

flexor retinaculum

ulnar nerve and artery

flexor digitorum superficialis

flexor digitorum profundus

median nerve

flexor pollicis longus

flexor carpi radialis

tubercle of scaphoid

radial artery

abductor pollicis longus

ridge of trapezium

abductor pollicis brevis

flexor pollicis brevis

opponens pollicis

adductor pollicis

first dorsal interosseous

first lumbrical

FIGURE 9.62

xor retinaculum

Anterior view of the palm of the hand. The palmar aponeurosis and the greater part of the fle

tendons of the flexor digitorum superficialis have been removed to show the underlying tendons of the flexor digitorum

have been removed to display the superficial palmar arch, the median nerve, and the long flexor tendons. Segments of the

profundus.

Basic Anatomy

in Figures 9.64 and 9.65 and are described in Table 9.8.

The muscles of the posterior fascial compartment are seen

the Forearm

Muscles of the Posterior Fascial Compartment of

nerve

Deep branch of the radial

Nerve supply to the muscles:

Posterior and anterior interosseous arteries

Blood supply:

and extensor indicis.

longus, extensor pollicis brevis, extensor pollicis longus,

includes the supinator, abductor pollicis

deep group

attached to the lateral epicondyle of the humerus. The

muscles possess a common tendon of origin, which is

minimi, extensor carpi ulnaris, and anconeus. These

carpi radialis brevis, extensor digitorum, extensor digiti

includes the extensor

superficial group

The

Muscles:

of the Forearm

Contents of the Posterior Fascial Compartment

the dorsum of the hand is variable.

and a half fingers. The area of skin supplied by the nerve on

393

■

Stenosing Synovitis of the Abductor Pollicis

Longus and Extensor Pollicis Brevis Tendons

As a result of repeated friction between these tendons and the

styloid process of the radius, they sometimes become edema-

tous and swell. Later, fibrosis of the synovial sheath produces

a condition known as stenosing tenosynovitis in which move-

ment of the tendons becomes restricted. Advanced cases

require surgical incision along the constricting sheath.

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

Arteries of the Posterior Fascial Compartment of

around the wrist joint.

and bones. They end by taking part in the anastomosis

membrane, respectively, and supply the adjoining muscles

on the anterior and posterior surfaces of the interosseous

ulnar artery (Figs. 9.61 and 9.65). They pass downward

from the common interosseous artery, a branch of the

arise

posterior interosseous arteries

anterior

The

the Forearm

and

is bounded medially by the tendon of the extensor pollicis lon

triangular skin depression on the lateral side of the wrist that

tendon, which can then rupture. Rheumatoid arthritis can also

third of the radius. Roughening of the dorsal tubercle of the

Rupture of the Extensor Pollicis Longus Tendon

Rupture of this tendon can occur after fracture of the distal

radius by the fracture line can cause excessive friction on the

cause rupture of this tendon.

“Anatomic Snuffbox”

The anatomic snuffbox is a term commonly used to describe a

gus and laterally by the tendons of the abductor pollicis longus

and extensor pollicis brevis (Fig. 9.64). Its clinical importance

lies in the fact that the scaphoid bone is most easily palpated

here and that the pulsations of the radial artery can be felt

here (Fig. 9.100).

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

Tennis Elbow

Tennis elbow is caused by a partial tearing or degeneration of

the origin of the superficial extensor muscles from the lateral

epicondyle of the humerus. It is characterized by pain and ten-

derness over the lateral epicondyle of the humerus, with pain

radiating down the lateral side of the forearm; it is common in

tennis players, violinists, and housewives.

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

Muscles of the Lateral Fascial Compartment of the Forearm

T A B L E 9 . 7

Muscle

Origin

Insertion

Nerve Supply

Nerve Roots

Action

Brachioradialis

Lateral supracon-

dylar ridge of

humerus

Base of styloid pro-

cess of radius

Radial nerve

C5, 6, 7

Flexes forearm

at elbow joint;

rotates forearm

to the midprone

position

Extensor carpi

radialis longus

Lateral supracon-

dylar ridge of

humerus

Posterior surface

of base of sec-

ond metacarpal

bone

Radial nerve

C6, 7

Extends and

abducts hand at

wrist joint

The predominant nerve root supply is indicated by boldface type.

394

CHAPTER 9

Palmar cutaneous branch of the median nerve

aponeurosis

insertion into the flexor retinaculum and the palmar

(if present), passing to its

Palmaris longus tendon

Palmar cutaneous branch of the ulnar nerve

lies lateral to the ulnar nerve.

Ulnar artery

lies lateral to the pisiform bone.

Ulnar nerve

inaculum but is included for the sake of completeness.)

bone. (This tendon does not actually cross the flexor ret

ending on the pisiform

Flexor carpi ulnaris tendon,

naculum from medial to lateral (Fig. 9.54):

The following structures pass superficial to the flexor reti

Wrist

structures as possible.

time, examine your own wrist and identify as many of the

identify the structures from medial to lateral. At the same

In a transverse section through the wrist (Fig. 9.54),

for injury.

joint. From a clinical standpoint, the wrist is a common site

the tendons, arteries, and nerves in the region of the wrist

a student have a sound knowledge of the arrangement of

Before learning the anatomy of the hand, it is essential that

The Region of the Wrist

to the wrist and carpal joints

Articular branches

pollicis longus, and the extensor indicis

pollicis longus, the extensor pollicis brevis, the extensor

digiti minimi, the extensor carpi ulnaris, the abductor

and the supinator, the extensor digitorum, the extensor

to the extensor carpi radialis brevis

Muscular branches

Branches

face of the wrist joint.

muscles (Fig. 9.65). It eventually reaches the posterior sur

in the interval between the superficial and deep groups of

posterior compartment of the forearm. The nerve descends

of the radius in the substance of the muscle to reach the

supinator and winds around the lateral aspect of the neck

the humerus in the cubital fossa (Fig. 9.61). It pierces the

from the radial nerve in front of the lateral epicondyle of

The deep branch arises

Deep Branch of the Radial Nerve

Forearm

Nerve of the Posterior Fascial Compartment of the

The Upper Limb

■

Structures on the Anterior Aspect of the

■

FIGURE 9.63

Insertions of long flexor and extensor tendons in the fingers. Insertions of the lumbrical and interossei muscles

pophalangeal joints and extending the interphalangeal joints.

are also shown. The uppermost figure illustrates the action of the lumbrical and interossei muscles in flexing the metacar-

extensor digitorum

interossei and lumbrical muscles

axis of rotation

flexor digitorum profundus

flexor digitorum superficialis

vincula brevia

vincula longa

dorsal extensor expansion

lumbrical

extensor
digitorum

interosseous

third metacarpal

extensor digitorum

third metacarpal

interosseous

flexor digitorum profundus

flexor digitorum superficialis

lumbrical