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ANTERIOR ASPECT OF THE
FORERARM
&
CUBITAL FOSSA
26. 12. 2012
Kaan Yücel
M.D., Ph.D.
http://yeditepeanatomy1.org
A TOTAL OF 14 FIGURES IN THE TEXT
Dr. Kaan Yücel
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Anterior aspect of the forearm & Cubital fossa
The forearm is the part of the upper limb between the elbow wrist joints. Proximally, most major structures pass
between the arm and forearm through, or in relation to, the cubital fossa, which is anterior to the elbow joint. The
exception is the ulnar nerve, which passes posterior to the medial epicondyle of the humerus.
ANTERIOR ASPECT OF FOREARM
Muscles in the anterior compartment of the forearm flex the wrist and digits and pronate the hand. Muscles in
the posterior compartment extend the wrist and digits and supinate the hand. Major nerves and vessels supply or
pass through each compartment.
The flexors and pronators of the forearm in the anterior compartment are served mainly by the median nerve;
the one and a half exceptions are innervated by the ulnar nerve. The extensors and supinators of the forearm are in
the posterior compartment and are all served by the radial nerve (directly or by its deep branch).
Muscles in the anterior (flexor) compartment of the forearm occur in three layers:
• Superficial layer (pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris)
• Intermediate layer (flexor digitorum superficialis)
• Deep layer (flexor digitorum profundus, flexor pollicis longus, and pronator quadratus)
Generally, these muscles are associated with: movements of the wrist joint; flexion of the fingers including the
thumb; andpronation.
The main arteries of the forearm are the ulnar and radial arteries, which usually arise opposite the neck of the
radius in the inferior part of the cubital fossa as terminal branches of the brachial artery.
The superficial veins of the forearm lie in the superficial fascia. The cephalic vein arises from the lateral side
of the dorsal venous arch on the back of the hand and winds around the lateral border of the forearm; it then ascends
into the cubital fossa and up the front of the arm on the lateral side of the biceps. It terminates in the axillary vein in
the deltopectoral triangle. The basilic vein arises from the medial side of the dorsal venous arch on the back of the
hand and winds around the medial border of the forearm; it then ascends into the cubital fossa and up the front of
the arm on the medial side of the biceps. Its terminates, by joining the venae comitantes of the brachial artery to
form the axillary vein.
Nerves in the anterior compartment of the forearm are the median and ulnar nerves, and the superficial branch
of the radial nerve.
The median nerve is the principal nerve of the anterior compartment of the forearm. It supplies muscular
branches directly to the muscles of the superficial and intermediate layers of forearm flexors (except the flexor carpi
ulnaris), and deep muscles (except for the medial [ulnar] half of the flexor digitorum profundus; ring and little
fingers) via its branch, the anterior interosseous nerve. The median nerve has no branches in the arm other than
small twigs to the brachial artery. Its major branch in the forearm is the anterior interosseous nerve.
Like the median nerve, the ulnar nerve does not give rise to branches during its passage through the arm. In
the forearm it supplies only one and a half muscles, the flexor carpi ulnaris muscle (as it enters the forearm by
passing between its two heads of proximal attachment) and the ulnar (medial) part (ring and little fingers) of the
flexor digitorum profundus muscle.
Unlike the medial and ulnar nerves, the radial nerve serves motor and sensory functions in both the arm and
the forearm (but only sensory functions in the hand). However, its sensory and motor fibers are distributed in the
forearm by two separate branches, the superficial (sensory or cutaneous) and deep radial/posterior interosseous
nerve (motor).
The lateral cutaneous nerve of the forearm (lateral antebrachial cutaneous nerve) is the continuation of the
musculocutaneous nerve after its motor branches have all been given off to the muscles of the anterior compartment
of the arm.
CUBITAL FOSSA
The pronator teres makes the medial border, whereas the brachioradialis makes the lateral border of the cubital
fossa.
The contents of the cubital fossa are the:
• Terminal part of the brachial artery and the commencement of its terminal branches, the radial and ulnar
arteries. The brachial artery lies between the biceps tendon and the median nerve.
• (Deep) accompanying veins of the arteries
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• Biceps brachii tendon
• Median nerve
• Radial nerve
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Anterior aspect of the forearm & Cubital fossa
1. FOREARM
The forearm is the part of the upper limb between the elbow wrist joints. Proximally, most major
structures pass between the arm and forearm through, or in relation to, the cubital fossa, which is anterior to
the elbow joint. The exception is the ulnar nerve, which passes posterior to the medial epicondyle of the
humerus.
The bone framework of the forearm consists of two parallel bones, the radius and the ulna which are
joined by an interosseous membrane. Although the proximal boundary of the forearm per se is defined by the
joint plane of the elbow, functionally the forearm includes the distal humerus. The radius is lateral in position
and is small proximally, where it articulates with the humerus, and large distally, where it forms the wrist joint
with the carpal bones of the hand.
As in the arm, the forearm is divided into anterior and posterior compartments. In the forearm, these
compartments are separated by:
 A lateral intermuscular septum, which passes from the anterior border of the radius to deep fascia
surrounding the limb;
 An interosseous membrane, which links adjacent borders of the radius and ulna along most of their length;
 the attachment of deep fascia along the posterior border of the ulna.
The forearm proper is not, in fact, long enough to provide the required length and sufficient area for
attachment proximally, so the proximal attachments (origins) of the muscles must occur proximal to the
elbow—in the arm—and provided by the humerus. The medial epicondyle and supraepicondylar ridge provide
attachment for the forearm flexors, and the lateral formations provide attachment for the forearm extensors.
Thus, rather than lying strictly anteriorly and posteriorly, the proximal parts of the “anterior” (flexor-pronator)
compartment of the forearm lie anteromedially, and the “posterior” (extensor-supinator) compartment lies
posterolaterally.
Spiraling gradually over the length of the forearm, the compartments become truly anterior and posterior in
position in the distal forearm and wrist. These fascial compartments, containing the muscles in functional
groups, are demarcated by the subcutaneous border of the ulna posteriorly (in the proximal forearm) and then
medially (distal forearm) and by the radial artery anteriorly and then laterally. These structures are palpable
(the artery by its pulsations) throughout the forearm. Because neither boundary is crossed by motor nerves,
they also provide sites for surgical incision.
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Muscles in the anterior compartment of the forearm flex the wrist and digits and pronate the hand. Muscles
in the posterior compartment extend the wrist and digits and supinate the hand. Major nerves and vessels
supply or pass through each compartment.
The flexors and pronators of the forearm in the anterior compartment are served mainly by the median
nerve; the one and a half exceptions are innervated by the ulnar nerve. The extensors and supinators of the
forearm are in the posterior compartment and are all served by the radial nerve (directly or by its deep branch).
The fascial compartments of the limbs generally end at the joints; therefore, fluids and infections in
compartments are usually contained and cannot readily spread to other compartments. The anterior
compartment is exceptional in this regard because it communicates with the central compartment of the palm
through the carpal tunnel.
Figure 1. Forearm- anterior aspect
http://www.britannica.com/EBchecked/media/111229/Muscles-of-the-human-forearm
2. MUSCLES
There are 17 muscles crossing the elbow joint, some of which act on the elbow joint exclusively,
whereas others act at the wrist and fingers.
The flexor muscles of the forearm are in the anterior (flexor-pronator) compartment of the forearm and
are separated from the extensor muscles of the forearm by the radius and ulna and, in the distal two thirds of
the forearm, by the interosseous membrane that connects them. The tendons of most flexor muscles are
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located on the anterior surface of the wrist and are held in place by the palmar carpal ligament and the flexor
retinaculum (transverse carpal ligament), thickenings of the antebrachial fascia.
Muscles in the anterior (flexor) compartment of the forearm occur in three layers:
 Superficial layer (pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris)
 Intermediate layer (flexor digitorum superficialis)
 Deep layer (flexor digitorum profundus, flexor pollicis longus, and pronator quadratus)
Generally, these muscles are associated with:
 movements of the wrist joint;
 flexion of the fingers including the thumb; and
 pronation.
The five superficial and intermediate muscles cross the elbow joint; the three deep muscles do not. With
the exception of the pronator quadratus, the more distally placed a muscle's distal attachment lies, the more
distally and deeply placed is its proximal attachment.
All muscles in the anterior compartment of the forearm are innervated by the median nerve, except for
the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle, which are
innervated by the ulnar nerve.
Functionally, the brachioradialis is a flexor of the forearm, but it is located in the posterior
(posterolateral) or extensor compartment and is thus supplied by the radial nerve. Therefore, the
brachioradialis is a major exception to the rule that (1) the radial nerve supplies only extensor muscles and (2)
that all flexors lie in the anterior (flexor) compartment.
SUPERFICIAL LAYER
All four muscles in the superficial layer-flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and
pronator teres-have a common origin from the medial epicondyle of the humerus, and, except for the
pronator teres, extend distally from the forearm into the hand.
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Figure 2. Superficial layer muscles of the anterior compartment of the forearm
http://www.getbodysmart.com/ap/muscularsystem/wristhanddigits/menu/image.gif
The flexor carpi ulnaris muscle is the most medial of the muscles in the superficial layer. having a long
linear origin from the olecranon and posterior border of the ulna (ulnar head), in addition to an origin from the
medial epicondyle of the humerus (humeral head).
The ulnar nerve enters the anterior compartment of the forearm by passing through the triangular gap
between the humeral and ulnar heads of flexor carpi ulnaris. The flexor carpi ulnaris muscle is a powerful
flexor and adductor of the wrist and is innervated by the ulnar nerve. The flexor carpi ulnaris simultaneously
flexes and adducts the hand at the wrist if acting alone. It flexes the wrist when it acts with the flexor carpi
radialis and adducts it when acting with the extensor carpi ulnaris.
This muscle is exceptional among muscles of the anterior compartment, being fully innervated by the
ulnar nerve. The tendon of the flexor carpi ulnaris is a guide to the ulnar nerve and artery, which are on its
lateral side at the wrist.
To test the flexor carpi ulnaris, the person puts the posterior aspect of the forearm and hand on a flat
table and is then asked to flex the wrist against resistance while the examiner palpates the muscle and its
tendon.
The flexor carpi radialis muscle is a long fusiform muscle located medial to the pronator teres and
lateral to palmaris longus and has a large and prominent tendon in the distal half of the forearm. Unlike the
tendon of the flexor carpi ulnaris, which forms the medial margin of the distal forearm, the tendon of the flexor
carpi radialis muscle is positioned just lateral to the midline. In this position, the tendon can be easily palpated,
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making it an important landmark for finding the pulse in the radial artery, which lies immediately lateral to it.
The flexor carpi radialis tendon is a good guide to the radial artery, which lies just lateral to it
The flexor carpi radialis is a powerful flexor of the wrist and can also abduct the wrist. It produces
flexion (when acting with the flexor carpi ulnaris) and abduction of the wrist (when acting with the extensors
carpi radialis longus and brevis). When acting alone, the flexor carpi radialis produces a combination of flexion
and abduction simultaneously at the wrist so that the hand moves anterolaterally.
To test the flexor carpi radialis, the person is asked to flex the wrist against resistance. If acting
normally, its tendon can be easily seen and palpated.
The pronator teres muscle, a fusiform muscle, is the most lateral of the superficial forearm flexors. Its
lateral border forms the medial boundary of the cubital fossa. The median nerve often exits the cubital fossa by
passing between the humeral and ulnar heads of this muscle. The pronator teres rotates the radius over the
ulna during pronation.
To test the pronator teres, the person's forearm is flexed at the elbow and pronated from the supine
position against resistance provided by the examiner. If acting normally, the muscle is prominent and can be
palpated at the medial margin of the cubital fossa.
The palmaris longus muscle is absent in about 14-15% of the population on one or both sides (usually
the left) in approximately 14% of people, but its actions are not missed. The palmaris longus lies between the
flexor carpi ulnaris and the flexor carpi radialis muscles. It is a spindle-shaped muscle with a long tendon, which
passes into the hand and attaches to the flexor retinaculum and to a thick layer of deep fascia, the palmar
aponeurosis, which underlies and is attached to the skin of the palm and fingers.
In addition to its role as an accessory flexor of the wrist joint, the palmaris longus muscle also opposes shearing
forces on the skin of the palm during gripping.
To test the palmaris longus, the wrist is flexed and the pads of the little finger and thumb are tightly
pinched together. If present and acting normally, the tendon can be easily seen and palpated.
INTERMEDIATE LAYER
The muscle in the intermediate layer of the anterior compartment of forearm is the flexor digitorum
superficialis muscle. This large muscle has two heads: humero-ulnar head and radial head.
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The median nerve and ulnar artery pass deep to the flexor digitorum superficialis between the two heads.
In the distal forearm, the flexor digitorum superficialis forms four tendons, which pass through the carpal
tunnel of the wrist and into the four fingers. The tendons for the ring and middle fingers are superficial to the
tendons for the index and little fingers.
In the forearm, carpal tunnel, and proximal regions of the four fingers, the tendons of the flexor
digitorum superficialis are anterior to the tendons of the flexor digitorum profundus muscle.
Near the base of the proximal phalanx of each finger, the tendon of the flexor digitorum superficialis splits into
two parts to pass dorsally around each side of the tendon of the flexor digitorum profundus and ultimately
attach to the margins of the middle phalanx.
The flexor digitorum superficialis flexes the metacarpophalangeal joint and proximal interphalangeal
joint of each finger; it also flexes the wrist joint.
To test the flexor digitorum superficialis, one finger is flexed at the proximal interphalangeal joint
against resistance and the other three fingers are held in an extended position to inactivate the flexor
digitorum profundus.
Figure 3. Intermediate layer muscle of the anterior compartment of the forearm: flexor digitorum superficialis
http://www.getbodysmart.com/ap/muscularsystem/wristhanddigits/flexordigitorumsup/tutorial.html
DEEP LAYER
There are three deep muscles in the anterior compartment of the forearm: flexor digitorum profundus, flexor
pollicis longus, and pronator quadratus.
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The flexor digitorum profundus muscle is the only muscle that can flex the distal interphalangeal joints
of the fingers. This thick muscle “clothes” the anterior aspect of the ulna. The flexor digitorum profundus
originates from the anterior and medial surfaces of the ulna and from the adjacent half of the anterior surface
of the interosseous membrane. It gives rise to four tendons, which pass through the carpal tunnel into the four
medial fingers. Throughout most of their course, the tendons are deep to the tendons of the flexor digitorum
superficialis muscle.
Opposite the proximal phalanx of each finger, each tendon of the flexor digitorum profundus passes through a
split formed in the overlying tendon of the flexor digitorum superficialis muscle and passes distally to insert into
the base of the distal phalanx.
In the palm, the lumbrical muscles originate from the sides of the tendons of the flexor digitorum profundus.
Innervation of the medial and lateral halves of the flexor digitorum profundus varies as follows:
 lateral half (associated with the index and middle fingers) is innervated by the anterior interosseous nerve
(branch of the median nerve);
 medial half (the part associated with the ring and little fingers) is innervated by the ulnar nerve.
The flexor digitorum profundus flexes the distal phalanges of the medial four fingers after the flexor
digitorum superficialis has flexed their middle phalanges (i.e., it curls the fingers and assists with flexion of the
hand, making a fist). Each tendon is capable of flexing two interphalangeal joints, the metacarpophalangeal
joint. Because the tendons cross the wrist, it can flex the wrist joint as well.
To test the flexor digitorum profundus, the proximal interphalangeal joint is held in the extended position
while the person attempts to flex the distal interphalangeal joint. The integrity of the median nerve in the
proximal forearm can be tested by performing this test using the index finger, and that of the ulnar nerve can
be assessed by using the little finger.
The flexor pollicis longus muscle originates from the anterior surface of the radius and the adjacent
half of the anterior surface of the interosseous membrane. It is a powerful muscle and forms a single large
tendon, which passes through the carpal tunnel, lateral to the tendons of the flexor digitorum superficialis and
flexor digitorum profundus muscles, and into the thumb where it attaches to the base of the distal phalanx.
The flexor pollicis longus flexes the thumb and is innervated by the anterior interosseous nerve (branch of the
median nerve).
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To test the flexor pollicis longus, the proximal phalanx of the thumb is held and the distal phalanx is
flexed against resistance.
The pronator quadratus, as its name indicates, is quadrangular and pronates the forearm. It originates
from a linear ridge on the anterior surface of the lower end of the ulna and passes laterally to insert onto the
flat anterior surface of the radius. It lies deep to, and is crossed by, the tendons of the flexor digitorum
profundus and flexor pollicis longus muscles. The pronator quadratus clothes the distal fourth of the radius and
ulna and the interosseous membrane between them. The pronator quadratus is the only muscle that attaches
only to the ulna at one end and only to the radius at the other end.
The pronator quadratus is the prime mover for pronation. The pronator quadratus muscle pulls the
distal end of the radius anteriorly over the ulna during pronation. The pronator quadratus initiates pronation; it
is assisted by the pronator teres when more speed and power are needed. The pronator quadratus also helps
the interosseous membrane hold the radius and ulna together, particularly when upward thrusts are
transmitted through the wrist (e.g., during a fall on the hand). The pronator quadratus is innervated by the
anterior interosseous nerve (branch of the median nerve).
Figure 4. Muscles of the superficial, intermediate and deep layers of the anterior compartment of the forearm
http://classconnection.s3.amazonaws.com/694/flashcards/597694/jpg/flexor_pronator_muscles1311293599431.jpg
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ARTERIES
The main arteries of the forearm are the ulnar and radial arteries, which usually arise opposite the neck of the
radius in the inferior part of the cubital fossa as terminal branches of the brachial artery.
Figure 5. Brachial artery and its two terminal branches: radial and ulnar arteries
http://teachmeanatomy.net/upper-limb-2/arteries-and-veins-of-the-upper-limb
RADIAL ARTERY
The radial artery originates from the brachial artery at approximately the neck of the radius and passes
along the lateral aspect of the forearm. The radial artery is the smaller of the terminal branches of the brachial
artery.
In the distal forearm, the radial artery lies immediately lateral to the large tendon of the flexor carpi
radialis muscle and directly anterior to the pronator quadratus muscle and the distal end of the radius. In the
distal forearm, the radial artery can be located using the flexor carpi radialis muscle as a landmark. The radial
pulse can be felt by gently palpating the radial artery against the underlying muscle and bone. When the
brachioradialis is pulled laterally, the entire length of the artery is visible.
Branches of the radial artery originating in the forearm include:
1) radial recurrent artery, which contributes to an anastomotic network around the elbow joint
2) small palmar carpal branch
3) superficial palmar branch enters the hand by passing through, or superficial to, the thenar muscles at the
base of the thumb, which anastomoses with the superficial palmar arch formed by the ulnar artery.
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Figure 6. Radial artery and its branches
http://upload.wikimedia.org/wikipedia/commons/e/e7/Gray528.png
ULNAR ARTERY
The ulnar artery is larger than the radial artery and passes down the medial side of the forearm. It
leaves the cubital fossa by passing deep to the pronator teres muscle, and then passes through the forearm in
the fascial plane between the flexor carpi ulnaris and flexor digitorum profundus muscles. In distal regions of
the forearm, the ulnar nerve is immediately medial to the ulnar artery.
The ulnar artery leaves the forearm, enters the hand by passing lateral to the pisiform bone and superficial to
the flexor retinaculum of the wrist, and arches over the palm. It is often the major blood supply to the medial
three and one-half digits.
Pulsations of the ulnar artery can be palpated on the lateral side of the flexor carpi ulnaris tendon,
where it lies anterior to the ulnar head.
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Figure 7. Ulnar artery and its branches
Branches of the ulnar artery that arise in the forearm include:
1) ulnar recurrent artery with anterior and posterior
branches, which contribute to an anastomotic network of
vessels around the elbow joint (The anterior and posterior
ulnar recurrent arteries anastomose with the inferior and
superior ulnar collateral arteries, respectively, thereby
participating in the periarticular arterial anastomoses of the
elbow)
2) numerous muscular arteries, which supply surrounding
muscles
3) common interosseous artery, which divides into anterior
and posterior interosseous arteries
4) two small carpal arteries (dorsal carpal branch and
palmar carpal branch)
Perforating the interosseous membrane in the distal forearm,
the anterior interosseous artery terminates by joining the
posterior interosseous artery.
VEINS
The superficial veins of the forearm lie in the superficial fascia. The cephalic vein arises from the lateral
side of the dorsal venous arch on the back of the hand and winds around the lateral border of the forearm; it
then ascends into the cubital fossa and up the front of the arm on the lateral side of the biceps. It terminates in
the axillary vein in the deltopectoral triangle. As the cephalic vein passes up the upper limb, it receives a
variable number of tributaries from the lateral and posterior surfaces of the limb.
The basilic vein arises from the medial side of the dorsal venous arch on the back of the hand and
winds around the medial border of the forearm; it then ascends into the cubital fossa and up the front of the
arm on the medial side of the biceps. Its terminates, by joining the venae comitantes of the brachial artery to
form the axillary vein. The median cubital vein, a branch of the cephalic vein in the cubital fossa, runs upward
and medially and joins the basilic vein. The basilic vein also receives a variable number of tributaries from the
medial and posterior surfaces of the upper limb.
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Figures 8 & 9. Veins in the anterior compartment of the forearm
http://www.hxbenefit.com/wp-content/uploads/2011/07/Basilic-Vein.gif
http://radiographics.rsna.org/content/vol28/issue1/images/large/e28f2.jpeg
Deep veins accompanying arteries are plentiful in the forearm. These accompanying veins (L. venae
comitantes) arise from the anastomosing deep venous palmar arch in the hand. From the lateral side of the
arch, paired radial veins arise and accompany the radial artery; from the medial side, paired ulnar veins arise
and accompany the ulnar artery. The veins accompanying each artery anastomose freely with each other. The
radial and ulnar veins drain the forearm but carry relatively little blood from the hand.
Deep veins of the anterior compartment drain into brachial veins associated with the brachial artery in the
cubital fossa.
NERVES
Nerves in the anterior compartment of the forearm are the median and ulnar nerves, and the superficial
branch of the radial nerve.
MEDIAN NERVE
The median nerve is the principal nerve of the anterior compartment of the forearm. It supplies
muscular branches directly to the muscles of the superficial and intermediate layers of forearm flexors (except
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the flexor carpi ulnaris), and deep muscles (except for the medial [ulnar] half of the flexor digitorum profundus;
ring and little fingers) via its branch, the anterior interosseous nerve.
It leaves the cubital fossa by passing between the two heads of the pronator teres muscle and passing
between the humero-ulnar and radial heads of the flexor digitorum superficialis muscle. It leaves the forearm
and enters the palm of the hand by passing through the carpal tunnel deep to the flexor retinaculum.
The median nerve has no branches in the arm other than small twigs to the brachial artery. Its major
branch in the forearm is the anterior interosseous nerve.
1) Articular branches: These branches pass to the elbow joint as the median nerve passes it.
2) Muscular branches: The nerve to the pronator teres usually arises at the elbow. A broad bundle of nerves
pierces the superficial flexor group of muscles and innervates the flexor carpi radialis, palmaris longus, and
flexor digitorum superficialis.
3) Anterior interosseous nerve: The largest branch of the median nerve in the forearm is the anterior
interosseous nerve innervates the muscles in the deep layer (flexor pollicis longus, the lateral half of flexor
digitorum profundus, and pronator quadratus).
4) Palmar cutaneous branch of the median nerve: A small palmar branch passes superficially into the hand and
innervates the skin over the base and central palm. This palmar branch is spared in carpal tunnel syndrome
because it passes into the hand superficial to the flexor retinaculum of the wrist.
ULNAR NERVE
Like the median nerve, the ulnar nerve does not give rise to branches during its passage through the
arm. In the forearm it supplies only one and a half muscles, the flexor carpi ulnaris muscle (as it enters the
forearm by passing between its two heads of proximal attachment) and the ulnar (medial) part (ring and little
fingers) of the flexor digitorum profundus muscle.
The ulnar nerve enters the anterior compartment of the forearm by passing posteriorly around the
medial epicondyle of the humerus and between the humeral and ulnar heads of the flexor carpi ulnaris muscle.
In the forearm the ulnar nerve gives rise to:
1) Muscular branches to the flexor carpi ulnaris and to the medial half of the flexor digitorum profundus.
2) Two small cutaneous branches; palmar branch passes into the hand to supply skin on the medial side of the
palm; larger dorsal branch innervates skin on the posteromedial side of the back of the hand and most skin
on the posterior surfaces of the medial one and one-half digits.
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Figure 10. Median nerve
http://www.pureprecisionchiro.com/wp-content/uploads/2011/02/MedianNerve.jpg
RADIAL NERVE
Unlike the medial and ulnar nerves, the radial nerve serves motor and sensory functions in both the arm
and the forearm (but only sensory functions in the hand). However, its sensory and motor fibers are distributed
in the forearm by two separate branches, the superficial (sensory or cutaneous) and deep radial/posterior
interosseous nerve (motor). The radial nerve bifurcates into deep and superficial branches anterior to the
lateral epicondyle of the humerus, between the brachialis and the brachioradialis, in the lateral border of the
cubital fossa.
The deep branch is predominantly motor and passes between the two heads of the supinator muscle to
access and supply muscles in the posterior compartment of the forearm.
The superficial branch of the radial nerve is sensory. It passes down the anterolateral aspect of the
forearm deep to the brachioradialis muscle. The nerve continues into the hand where it innervates skin on the
posterolateral surface.
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Anterior aspect of the forearm & Cubital fossa
Figure 11. Ulnar nerve & Radial nerve
http://karate.butsu.net/anatomy/anterior_view.html
volar= anterior
LATERAL AND MEDIAL CUTANEOUS NERVES OF
FOREARM
The lateral cutaneous nerve of the forearm (lateral antebrachial cutaneous nerve) is the continuation of
the musculocutaneous nerve after its motor branches have all been given off to the muscles of the anterior
compartment of the arm.
The medial cutaneous nerve of the forearm (medial antebrachial cutaneous nerve) is an independent
branch of the medial cord of the brachial plexus. With the posterior cutaneous nerve of the forearm from the
radial nerve, each supplying the area of skin indicated by its name, these three nerves provide all the
cutaneous innervation of the forearm. There is no “anterior cutaneous nerve of the forearm.” (Memory device:
This is similar to the brachial plexus, which has lateral, medial, and posterior cords but no anterior cord.)
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Anterior aspect of the forearm & Cubital fossa
Figures 12 & 13. Lateral cutaneous nerve of forearm
http://www.lookfordiagnosis.com/mesh_info.php?term=Musculocutaneous+Nerve&lang=1
http://www.kmle.co.kr/search.php?Search=antebrachial&Page=1
Although the arteries, veins, and nerves of the forearm have been considered separately, it is important
to place them into their anatomical context. Except for the superficial veins, which often course independently
in the subcutaneous tissue, these neurovascular structures usually exist as components of neurovascular
bundles. These bundles are composed of arteries, veins (in the limbs, usually in the form of accompanying
veins), and nerves as well as lymphatic vessels, which are usually surrounded by a neurovascular sheath of
varying density.
CLINICAL ANATOMY
Radial Nerve Injuries
The radial nerve is commonly damaged in the axilla and in the spiral groove.
Injuries to the Median Nerve at the Elbow
Motor
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The pronator muscles of the forearm and the long flexor muscles of the wrist and fingers, with the
exception of the flexor carpi ulnaris and the medial half of the flexor digitorum profundus, will be paralyzed. As
a result, the forearm is kept in the supine position; wrist flexion is weak and is accompanied by adduction. The
latter deviation is caused by the paralysis of the flexor carpi radialis and the strength of the flexor carpi ulnaris
and the medial half of the flexor digitorum profundus. No flexion is possible at the interphalangeal joints of the
index and middle fingers, although weak flexion of the metacarpophalangeal joints of these fingers is
attemptedby the interossei. When the patient tries to make fist, the index and to a lesser extent the middle
fingers tend to remain straight, whereas the ring and little fingers flex . The latter two fingers are, however,
weakened by the loss of the flexor digitorum superficialis. Flexion of the terminal phalanx of the thumb is lost
because of paralysis of the flexor pollicis longus. The muscles of the thenar eminence are paralyzed and wasted
so that the eminence is flattened. The thumb is laterally rotated and adducted. The hand looks flattened and
“ape-like.”
Sensory
Skin sensation is lost on the lateral half or less of the palm of the hand and the palmar aspect of the lateral
three and a half fingers. Sensory loss also occurs on the skin of the distal part of the dorsal surfaces of the
lateral three and a half fingers. The area of total anesthesia is considerably less because of the overlap of
adjacent nerves.
Vasomotor Changes
The skin areas involved in sensory loss are warmer and drier than normal because of the arteriolar dilatation
and absence of sweating resulting from loss of sympathetic control.
Trophic Changes
In long-standing cases, changes are found in the hand and fingers. The skin is dry and scaly, the nails crack
easily, and atrophy of the pulp of the fingers is present.
Pronator Syndrome
Pronator syndrome, a nerve entrapment syndrome, is caused by compression of the median nerve near the
elbow. The nerve may be compressed between the heads of the pronator teres as a result of trauma, muscular
hypertrophy, or fibrous bands. Individuals with this syndrome are first seen clinically with pain and tenderness
in the proximal aspect of the anterior forearm and hypesthesia of palmar aspects of the radial three and half
digits and adjacent palm. Symptoms often follow activities that involve repeated pronation.
Anterior interosseous nerve syndrome
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Anterior aspect of the forearm & Cubital fossa
The anterior interosseous nerve ( an entirely motor branch of the median nerve) provides motor innervation to
the flexor pollicis longus (FPL), flexor digitorum profundus (FDP) to the index and sometimes middle fingers,
and to the pronator quadratus (PQ). Paralysis of these muscles from a complete nerve palsy will result in a
pinch deformity, though weakness of pronation may be masked by the concurrent action of the pronator teres
(PT). A case report @ http://www.sma.org.sg/smj/4412/4412cr1.pdf
Injuries to the Ulnar Nerve at the Elbow
Motor
The flexor carpi ulnaris and the medial half of the flexor digitorum profundus muscles are paralyzed. The
paralysis of the flexor carpi ulnaris can be observed by asking the patient to make a tightly clenched fist.
Normally, the synergistic action of the flexor carpi ulnaris tendon can be observed as it passes to the pisiform
bone; the tightening of the tendon will be absent if the muscle is paralyzed. The profundus tendons to the ring
and little fingers will be functionless, and the terminal phalanges of these fingers are therefore not capable of
being markedly flexed. Flexion of the wrist joint will result in abduction, owing to paralysis of the flexor carpi
ulnaris.
The medial border of the front of the forearm will show flattening, owing to the wasting of the
underlying ulnaris and profundus muscles. The small muscles of the hand will be paralyzed, except the muscles
of the thenar eminence and the first two lumbricals,which are supplied by the median nerve. The patient is
unable to adduct and abduct the fingers and consequently is unable to grip a piece of paper placed between
the fingers. Remember that the extensor digitorum can abduct the fingers to a small extent, but only when the
metacarpophalangeal joints are hyperextended.It is impossible to adduct the thumb because the adductor
pollicis muscle is paralyzed. If the patient is asked to grip a piece of paper between the thumb and the
index finger, he or she does so by strongly contracting the flexor pollicis longus and flexing the terminal phalanx
(Froment’s sign).
The metacarpophalangeal joints become hyperextended because of the paralysis of the lumbrical and
interosseous muscles, which normally flex these joints. Because the first and second lumbricals are not
paralyzed (they are supplied by the median nerve), the hyperextension of the metacarpophalangeal joints is
most prominent in the fourth and fifth fingers. The interphalangeal joints are flexed, owing again to the
paralysis of the lumbrical and interosseous muscles, which normally extend these joints through the extensor
expansion. The flexion deformity at the interphalangeal joints of the fourth and fifth fingers is obvious because
the first and second lumbrical muscles of the index and middle fingers are not paralyzed. In longstanding
cases the hand assumes the characteristic “claw” deformity (main en griffe). Wasting of the paralyzed muscles
results in flattening of the hypothenar eminence and loss of the convex curve to the medial border of the hand.
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Anterior aspect of the forearm & Cubital fossa
Examination of the dorsum of the hand will show hollowing between the metacarpal bones caused by wasting
of the dorsal interosseous muscles.
Sensory
Loss of skin sensation will be observed over the anterior and posterior surfaces of the medial third of the hand
and the medial one and a half fingers.
Vasomotor Changes
The skin areas involved in sensory loss are warmer and drier than normal because of the arteriolar dilatation
and absence of sweating resulting from loss of sympathetic control.
Communications Between Median and Ulnar Nerves
Occasionally, communications occur between the median and the ulnar nerves in the forearm. These
branches are usually represented by slender nerves, but the communications are important clinically because
even with a complete lesion of the median nerve, some muscles may not be paralyzed. This may lead to an
erroneous conclusion that the median nerve has not been damaged.
Measuring Pulse Rate
The common place for measuring the pulse rate is where the radial artery lies on the anterior surface of the
distal end of the radius, proximal to the wrist, between the tendons of the flexor carpi radialis and
brachioradialis. Here the artery is covered by only fascia and skin. The artery can be compressed against the
distal end of the radius, where it lies between the tendons of the flexor carpi radialis and abductor pollicis
longus. When measuring the radial pulse rate, the pulp of the thumb should not be used because it has its own
pulse, which could obscure the patient's pulse. If a pulse cannot be felt, try the other wrist because an aberrant
radial artery on one side may make the pulse difficult to palpate. A radial pulse may also be felt by pressing
lightly in the anatomical snuff box between the extensor pollicus longus and brevis muscles.
3. CUBITAL FOSSA
The cubital fossa is an important area of transition between the arm and the forearm. The cubital fossa
is seen superficially as a depression on the anterior aspect of the elbow. Deeply, it is a space filled with a
variable amount of fat anterior to the most distal part of the humerus and the elbow joint.
 Superiorly, an imaginary line connecting the medial and lateral epicondyles.
 Medially, the mass of flexor muscles of the forearm arising from the common flexor attachment on the
medial epicondyle; most specifically, the pronator teres.
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Anterior aspect of the forearm & Cubital fossa
 Laterally, the mass of extensor muscles of the forearm arising from the lateral epicondyle and
supraepicondylar ridge; most specifically, the brachioradialis.
As a summary, the pronator teres makes the medial border, whereas the brachioradialis makes the lateral one.
The floor of the cubital fossa is formed by the brachialis and supinator muscles of the arm and forearm,
respectively. The roof of the cubital fossa is formed by the continuity of brachial and antebrachial (deep) fascia
reinforced by the bicipital aponeurosis, subcutaneous tissue, and skin.
The contents of the cubital fossa are the:
 Terminal part of the brachial artery and the commencement of its terminal branches, the radial and ulnar
arteries. The brachial artery lies between the biceps tendon and the median nerve.
 (Deep) accompanying veins of the arteries
 Biceps brachii tendon
 Median nerve
 Radial nerve
Superficially, in the subcutaneous tissue overlying the fossa are the median cubital vein, lying anterior to the
brachial artery, and the medial and lateral antebrachial cutaneous nerves, related to the basilic and cephalic
veins.
The supratrochlear lymph node lies in the superficial fascia over the upper part of the fossa, above the
trochlea. It receives afferent lymph vessels from the third, fourth, and fifth fingers; the medial part of the hand;
and the medial side of the forearm. The efferent lymph vessels pass up to the axilla and enter the lateral axillary
nodes (The superficial lymph vessels from the thumb and lateral fingers and the lateral areas of the hand and
forearm follow the cephalic vein to the infraclavicular group of nodes. Those from the medial fingers and the
medial areas of the hand and forearm follow the basilic vein to the cubital fossa).
The brachial artery normally bifurcates into the radial and ulnar arteries in the apex of the fossa,
although this bifurcation may occur much higher in the arm, even in the axilla. When taking a blood pressure
reading from a patient, the clinician places the stethoscope over the brachial artery in the cubital fossa.
The median nerve lies immediately medial to the brachial artery and leaves the fossa by passing
between the ulnar and humeral heads of the pronator teres muscle.
The brachial artery and the median nerve are covered and protected anteriorly in the distal part of the
cubital fossa by the bicipital aponeurosis. This flat connective tissue membrane passes between the medial side
of the tendon of the biceps brachii muscle and deep fascia of the forearm. The sharp medial margin of the
bicipital aponeurosis can often be felt.
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Anterior aspect of the forearm & Cubital fossa
The radial nerve lies just under the lip of the brachioradialis muscle, which forms the lateral margin of
the fossa. In the cubital fossa the radial nerve gives off the deep branch of the radial nerve and continues as the
superficial radial nerve. The deep branch supplies the extensor carpi radialis brevis and the supinator in the
cubital fossa and all the extensor muscles in the posterior compartment of the forearm.
The ulnar nerve does not pass through the cubital fossa. Instead, it passes posterior to the medial epicondyle.
The roof of the cubital fossa is formed by superficial fascia and skin. The most important structure within
the roof is the median cubital vein, which passes diagonally across the roof and connects the cephalic vein on
the lateral side of the upper limb with the basilic vein on the medial side. The bicipital aponeurosis separates
the median cubital vein from the brachial artery and median nerve. Other structures within the roof are
cutaneous nerves;-the medial cutaneous and lateral cutaneous nerves of the forearm.
Figure 14. Cubital fossa
http://www.daviddarling.info/images2/cubital_fossa.jpg
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Anterior aspect of the forearm & Cubital fossa
Table 1. Muscles of the anterior compartment of the forearm (superficial and intermediate layers)
Muscle
Proximal Attachment
Distal Attachment
Innervation
Main Action
Median nerve
Pronates and flexes
forearm (at elbow)
Superficial (first) layer
Pronator teres
Ulnar head
Humeral head
Flexor carpi radialis
(FCR)
Palmaris longus
Flexor carpi ulnaris
(FCU)
Humeral head
Ulnar head
Coronoid process
Medial epicondyle
and adjacent
supraepicondylar
ridge
Medial epicondyle of
humerus
Lateral surface of
radius
Base of metacarpals II
and III
Flexes and abducts
hand (at wrist)
Medial epicondyle of
humerus (common
flexor origin)
Flexor retinaculum
and palmar
aponeurosis
Flexes hand (at wrist)
and tenses palmar
aponeurosis
Medial epicondyle of
humerus
 Olecranon
 Posterior border of
ulna
 Pisiform & hamate
 5th metacarpal
Ulnar nerve
Flexes and adducts
the wrist joint
Intermediate (second) layer
Flexor digitorum superficialis (FDS)
Humeroulnar head
 Medial epicondyle
of humerus
 Adjacent margin of
coronoid process
Radial head
Superior half of
anterior border
Shafts of middle
phalanges of medial
four digits
Median nerve
Flexes proximal
interphalangeal joints
of the index, middle,
ring, and little fingers;
can also flex
metacarpophalangeal
joints of the same
fingers and the wrist
joint
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Anterior aspect of the forearm & Cubital fossa
Table 2. Muscles of the anterior compartment of the forearm (deep layer)
Muscle
Proximal Attachment
Flexor digitorum profundus (FDP)
Medial part
Proximal three
quarters of medial
and anterior surfaces
of ulna and
interosseous
Lateral part
membrane
Distal Attachment
Innervation
Main Action
Bases of distal
phalanges of 4th and
5th digits
Ulnar nerve
Bases of distal
phalanges of 2nd and
3rd digits
Anterior interosseous
nerve, from median
nerve
Flexor pollicis longus
(FPL)
Base of distal phalanx
of thumb
Flexes distal
phalanges 4 and 5 at
distal interphalangeal
joints
Flexes distal
phalanges 2 and 3 at
distal interphalangeal
joints
Flexes phalanges of
1st digit (thumb)
Pronator quadratus
Anterior surface of
radius and adjacent
interosseous
membrane
Distal quarter of
anterior surface of
ulna
Distal quarter of
anterior surface of
radius
Pronates forearm;
deep fibers bind
radius and ulna
together
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