Anterior Aspect of the Forearm Cubital Fossa 2012

8/16/2019 Anterior Aspect of the Forearm Cubital Fossa 2012

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Dr. Kaan Yücel http://yeditepeanatomy1.org Anterior aspect of the forearm & Cubital fossa

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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.

NTERIOR SPECT OF FORE RM

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"

# $uperficial layer pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris!

# %ntermediate layer flexor digitorum superficialis!

# &eep layer flexor digitorum profundus, flexor pollicis longus, and pronator 'uadratus!

(enerally, these muscles are associated with" movements of the wrist joint; flexion of the fingers including thethumb; andpronation.

The main arteries of the forearm are the ulnar and radial arteries, which usually arise opposite the nec) 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 bac) 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. %t terminates in the

axillary vein in the deltopectoral triangle. The basilic vein arises from the medial side of the dorsal venous arch on

the bac) 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. %ts terminates, by joining the venae comitantes of the

brachial artery to form the axillary vein.

*erves 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. %t 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. %ts major branch in the forearm is the anterior interosseous nerve.

-i)e the median nerve, the ulnar nerve does not give rise to branches during its passage through the arm. %n

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.nli)e 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!. /owever, its sensory and motor fibers are distributed in the

forearm by two separate branches, the superficial sensory or cutaneous! and deep radial0posterior 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 ma)es the medial border, whereas the brachioradialis ma)es 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.

# &eep! accompanying veins of the arteries

# 1iceps brachii tendon

# Median nerve


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The forearm is the part of the upper lim et!een the elo! !rist "oints.

Pro#imally, most ma"or structures pass et!een the arm and forearm through, or in

relation to, the cuital fossa, !hich is anterior to the elo! "oint. The e#ception is the

ulnar nerve, !hich passes posterior to the medial epicondyle of the humerus.

The one frame!or$ of the forearm consists of t!o parallel ones, the radius and

the ulna !hich are "oined y an interosseous memrane. %lthough the pro#imal oundary

of the forearm per se is de&ned y the "oint plane of the elo!, functionally the forearm

includes the distal humerus. The radius is lateral in position and is small pro#imally, !here

it articulates !ith the humerus, and large distally, !here it forms the !rist "oint !ith the

carpal ones of the hand.

%s in the arm, the forearm is di'ided into anterior and posterior compartments. (n

the forearm, these compartments are separated y:

• % lateral intermuscular septum, !hich passes from the anterior order of the radius

to deep fascia surrounding the lim)

• %n interosseous membrane, !hich lin$s ad"acent orders 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 pro'ide the re*uired length and

su+cient area for attachment pro#imally, so the pro#imal attachments origins- of the

muscles must occur pro#imal to the elo!in the armand pro'ided y the humerus.

The medial epicondyle and supraepicondylar ridge pro'ide attachment for the forearm

e#ors, and the lateral formations pro'ide attachment for the forearm e#tensors. Thus,

rather than lying strictly anteriorly and posteriorly, the proximal parts of the “anterior”

(exor-pronator) compartment of the forearm lie anteromedially, and the “posterior”

(extensor-supinator) compartment lies posterolaterally.

0piraling gradually o'er the length of the forearm, the compartments ecome truly

anterior and posterior in position in the distal forearm and !rist. These fascial

compartments, containing the muscles in functional groups, are demarcated y the

sucutaneous order of the ulna posteriorly in the pro#imal forearm- and then medially

distal forearm- and y the radial artery anteriorly and then laterally. These structures are

palpale the artery y its pulsations- throughout the forearm. ecause neither oundary

is crossed y motor ner'es, they also pro'ide sites for surgical incision.

1. FOREARM


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Muscles in the anterior compartment of the forearm e# the !rist and digits and

pronate the hand. Muscles in the posterior compartment e#tend the !rist and digits and

supinate the hand. Ma"or ner'es and 'essels supply or pass through each compartment.

The e#ors and pronators of the forearm in the anterior compartment are ser'ed mainly

y the median ner'e) the one and a half e#ceptions are inner'ated y the ulnar ner'e.

The e#tensors and supinators of the forearm are in the posterior compartment and are all

ser'ed y the radial ner'e directly or y its deep ranch-.

The fascial compartments of the lims generally end at the "oints) therefore, uids and

infections in compartments are usually contained and cannot readily spread to other

compartments. The anterior compartment is e#ceptional in this regard ecause it

communicates !ith the central compartment of the palm through the carpal tunnel.

2igure 1. 2orearm3 anterior aspecthttp://.britannica.com/!"chec#ed/media/111$$%/uscles'of'the'human'forearm

There are 14 muscles crossing the elo! "oint, some of !hich act on the elo! "oint

e#clusi'ely, !hereas others act at the !rist and &ngers.

The e#or muscles of the forearm are in the anterior e#or3pronator- compartment

of the forearm and are separated from the e#tensor muscles of the forearm y the radius

and ulna and, in the distal t!o thirds of the forearm, y the interosseous memrane that

connects them. The tendons of most e#or muscles are located on the anterior surface of

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the !rist and are held in place y the palmar carpal ligament and the exor retinaculum

(transverse carpal ligament), thic$enings of the anterachial fascia.

Muscles in the anterior e#or- compartment of the forearm occur in three layers:

• 0uper&cial layer pronator teres, exor carpi radialis, palmaris longus, and exor carpi

ulnaris-

• (ntermediate layer exor digitorum supercialis-

• Deep layer exor digitorum profundus, exor pollicis longus, and pronator uadratus-

5enerally, these muscles are associated !ith:

mo'ements of the !rist "oint)

e#ion of the &ngers including the thum) and

pronation.

The &'e super&cial and intermediate muscles cross the elo! "oint) the three deep

muscles do not. 6ith the e#ception of the pronator *uadratus, the more distally placed a

muscle7s distal attachment lies, the more distally and deeply placed is its pro#imal

attachment.

%ll muscles in the anterior compartment of the forearm are inner'ated y the

median ner'e, e#cept for the e#or carpi ulnaris muscle and the medial half of the e#or

digitorum profundus muscle, !hich are inner'ated y the ulnar ner'e.

2unctionally, the brachioradialis is a e#or of the forearm, ut it is located in the

posterior posterolateral- or e#tensor compartment and is thus supplied y the radial

ner'e. Therefore, the rachioradialis is a ma"or e#ception to the rule that 1- the radial

ner'e supplies only e#tensor muscles and 8- that all e#ors lie in the anterior e#or-

compartment.

SUPERFICI L L YER

%ll four muscles in the super&cial layer3exor carpi ulnaris, palmaris longus,

exor carpi radialis, and pronator teres3ha'e a common origin from the medial

epicondyle of the humerus, and, e#cept for the pronator teres, e#tend distally from the

forearm into the hand.

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2igure 8. 0uper&cial layer muscles of the anterior compartment of the forearm

http://.getbodysmart.com/ap/muscularsystem/risthanddigits/menu/image.gif

The exor carpi ulnaris muscle is the most medial of the muscles in the

super&cial layer. ha'ing 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 thehumerus humeral head-.

The ulnar ner'e enters the anterior compartment of the forearm y passing through

the triangular gap et!een the humeral and ulnar heads of e#or carpi ulnaris. The

e#or carpi ulnaris muscle is a po!erful exor and adductor of the wrist and is

inner'ated y the ulnar nerve. The e#or carpi ulnaris simultaneously e#es and

adducts the hand at the !rist if acting alone. (t e#es the !rist !hen it acts !ith the e#or

carpi radialis and adducts it !hen acting !ith the e#tensor carpi ulnaris.

This muscle is e#ceptional among muscles of the anterior compartment, eing fully

inner'ated y the ulnar ner'e. The tendon of the e#or carpi ulnaris is a guide to the

ulnar ner'e and artery, !hich are on its lateral side at the !rist.

To test the exor carpi ulnaris, the person puts the posterior aspect of the

forearm and hand on a at tale and is then as$ed to e# the !rist against resistance

!hile the e#aminer palpates the muscle and its tendon.

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The exor 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. 9nli$e the tendon of the e#or carpi ulnaris, !hich forms the

medial margin of the distal forearm, the tendon of the e#or carpi radialis muscle is

positioned "ust lateral to the midline. (n this position, the tendon can e easily palpated,

ma$ing it an important landmar$ for &nding the pulse in the radial artery, !hich lies

immediately lateral to it. The e#or carpi radialis tendon is a good guide to the radial

artery, !hich lies "ust lateral to it

The e#or carpi radialis is a powerful exor of the wrist and can also abduct

the wrist. (t produces e#ion !hen acting !ith the e#or carpi ulnaris- and aduction of

the !rist !hen acting !ith the e#tensors carpi radialis longus and re'is-. 6hen acting

alone, the e#or carpi radialis produces a comination of e#ion and aduction

simultaneously at the !rist so that the hand mo'es anterolaterally.

To test the exor carpi radialis, the person is as$ed to e# the !rist against

resistance. (f acting normally, its tendon can e easily seen and palpated.

The pronator teres muscle, a fusiform muscle, is the most lateral of the

super&cial forearm e#ors. (ts lateral order forms the medial oundary of the cuital

fossa. The median ner'e often e#its the cuital fossa y passing et!een 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 person7s forearm is e#ed at the elo! and

pronated from the supine position against resistance pro'ided y the e#aminer. (f acting

normally, the muscle is prominent and can e palpated at the medial margin of the

cuital fossa.

The palmaris longus muscle is asent in aout 131;< of the population on one

or oth sides usually the left- in appro#imately 1< of people, ut its actions are not

missed. The palmaris longus lies et!een the e#or carpi ulnaris and the e#or carpi

radialis muscles. (t is a spindle3shaped muscle !ith a long tendon, !hich passes into the

hand and attaches to the exor retinaculum and to a thic$ layer of deep fascia, the

palmar aponeurosis, !hich underlies and is attached to the s$in of the palm and&ngers.

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(n addition to its role as an accessory e#or of the !rist "oint, the palmaris longus muscle

also opposes shearing forces on the s$in of the palm during gripping.

To test the palmaris longus, the !rist is e#ed and the pads of the little &nger

and thum are tightly pinched together. (f present and acting normally, the tendon can e

easily seen and palpated.

INTERMEDI TE L YER

The muscle in the intermediate layer of the anterior compartment of forearm is theexor

digitorum supercialis muscle. This large muscle has t!o heads: humero3ulnar head

and radial head.

The median ner'e and ulnar artery pass deep to the e#or digitorum super&cialis et!een

the t!o heads.

(n the distal forearm, the e#or digitorum super&cialis forms four tendons, !hich pass

through the carpal tunnel of the !rist and into the four &ngers. The tendons for the ring

and middle &ngers are super&cial to the tendons for the inde# and little &ngers.

(n the forearm, carpal tunnel, and pro#imal regions of the four &ngers, the tendons

of the e#or digitorum super&cialis are anterior to the tendons of the e#or digitorum

profundus muscle.

=ear the ase of the pro#imal phalan# of each &nger, the tendon of the e#or digitorum

super&cialis splits into t!o parts to pass dorsally around each side of the tendon of the

e#or digitorum profundus and ultimately attach to the margins of the middle phalan#.

The e#or digitorum super&cialis exes the metacarpophalangeal !oint and

proximal interphalangeal !oint of each nger) it also exes the wrist !oint.

To test the exor digitorum supercialis, one &nger is e#ed at the pro#imal

interphalangeal "oint against resistance and the other three &ngers are held in an

e#tended position to inacti'ate the e#or digitorum profundus.

2igure >. (ntermediate layer muscle of the anterior compartment of the forearm: e#or

digitorum super&cialis

http://.getbodysmart.com/ap/muscularsystem/risthanddigits/fle(ordigitorumsup/tutorial.html

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DEEP L YER

There are three deep muscles in the anterior compartment of the forearm:exor

digitorum profundus, exor pollicis longus, and pronator "uadratus.

The exor digitorum profundus muscle is the only muscle that can e# the

distal interphalangeal "oints of the &ngers. This thic$ muscle ?clothes@ the anterior aspect

of the ulna. The e#or digitorum profundus originates from the anterior and medial

surfaces of the ulna and from the ad!acent half of the anterior surface of the

interosseous membrane. (t gi'es rise to four tendons, !hich pass through the carpal

tunnel into the four medial &ngers. Throughout most of their course, the tendons are deep

to the tendons of the e#or digitorum super&cialis muscle.

Apposite the pro#imal phalan# of each &nger, each tendon of the e#or digitorum

profundus passes through a split formed in the o'erlying tendon of the e#or digitorum

super&cialis muscle and passes distally to insert into the base of the distal phalanx.

(n the palm, the lumrical muscles originate from the sides of the tendons of the e#or

digitorum profundus.

(nner'ation of the medial and lateral hal'es of the e#or digitorum profundus 'aries

as follo!s:

lateral half associated !ith the inde# and middle &ngers- is inner'ated y the anterior

interosseous ner'e ranch of the median ner'e-)

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medial half the part associated !ith the ring and little &ngers- is inner'ated y the

ulnar ner'e.

The e#or digitorum profundus e#es the distal phalanges of the medial four &ngers

after the e#or digitorum super&cialis has e#ed their middle phalanges i.e., it curls the

&ngers and assists !ith e#ion of the hand, ma$ing a &st-. Bach tendon is capale of

e#ing t!o interphalangeal "oints, the metacarpophalangeal "oint. ecause the tendons

cross the !rist, it can e# the !rist "oint as !ell.

To test the exor digitorum profundus, the pro#imal interphalangeal "oint is held in

the e#tended position !hile the person attempts to e# the distal interphalangeal "oint.

The integrity of the median ner'e in the pro#imal forearm can e tested y performing

this test using the inde# &nger, and that of the ulnar ner'e can e assessed y using the

little &nger.

The exor pollicis longus muscle originates from the anterior surface of the

radius and the ad!acent half of the anterior surface of the interosseous

membrane. (t is a po!erful muscle and forms a single large tendon, !hich passes

through the carpal tunnel, lateral to the tendons of the e#or digitorum super&cialis and

e#or digitorum profundus muscles, and into the thumb !here it attaches to the base

of the distal phalanx.

The e#or pollicis longus exes the thumb and is inner'ated y the anterior

interosseous ner'e ranch of the median ner'e-.

To test the exor pollicis longus, the pro#imal phalan# of the thum is held and

the distal phalan# is e#ed against resistance.

The pronator "uadratus, as its name indicates, is *uadrangular and pronates the

forearm. (t originates from a linear ridge on the anterior surface of the lo!er end of the

ulna and passes laterally to insert onto the at anterior surface of the radius. (t lies deep

to, and is crossed y, the tendons of the e#or digitorum profundus and e#or pollicis

longus muscles. The pronator *uadratus clothes the distal fourth of the radius and ulna

and the interosseous memrane et!een them. The pronator *uadratus is the only

muscle that attaches only to the ulna at one end and only to the radius at the other end.

The pronator *uadratus is the prime mover for pronation. The pronator*uadratus muscle pulls the distal end of the radius anteriorly o'er the ulna during

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pronation. The pronator *uadratus initiates pronation) it is assisted y the pronator teres

!hen more speed and po!er are needed. The pronator *uadratus also helps the

interosseous memrane hold the radius and ulna together, particularly !hen up!ard

thrusts are transmitted through the !rist e.g., during a fall on the hand-. The pronator

*uadratus is inner'ated y the anterior interosseous ner'e ranch of the median ner'e-.

2igure . Muscles of the super&cial, intermediate and deep layers of the anterior

compartment of the forearm

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RTERIES

The main arteries of the forearm are the ulnar and radial arteries, !hich usually arise

opposite the nec$ of the radius in the inferior part of the cuital fossa as terminal

ranches of the rachial artery.

2igure ;. rachial artery and its t!o terminal ranches: radial and ulnar arteries

http://teachmeanatomy.net/upper'limb'$/arteries'and'eins'of'the'upper'limb

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RADIAL ARTERY

The radial artery originates from the rachial artery at appro#imately the nec$ of

the radius and passes along the lateral aspect of the forearm. The radial artery is the

smaller of the terminal ranches of the rachial artery.

(n the distal forearm, the radial artery lies immediately lateral to the large tendon of

the e#or carpi radialis muscle and directly anterior to the pronator *uadratus muscle and

the distal end of the radius. (n the distal forearm, the radial artery can e located using

the e#or carpi radialis muscle as a landmar$. The radial pulse can e felt y gentlypalpating the radial artery against the underlying muscle and one. 6hen the

rachioradialis is pulled laterally, the entire length of the artery is 'isile.

ranches of the radial artery originating in the forearm include:

1-radial recurrent artery, !hich contriutes to an anastomotic net!or$ around the

elo! "oint

8-small palmar carpal branch

>-supercial palmar branch enters the hand y passing through, or super&cial to, the

thenar muscles at the ase of the thum, !hich anastomoses !ith the superfcial

palmar arch formed y the ulnar artery.

2igure C. adial artery and its ranches

http://upload.i#imedia.org/i#ipedia/commons/e/e/2ray-$3.png

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ULNAR ARTERY

The ulnar artery is larger than the radial artery and passes do!n the medial side

of the forearm. (t lea'es the cuital fossa y passing deep to the pronator teres muscle,

and then passes through the forearm in the fascial plane et!een the e#or carpi ulnaris

and e#or digitorum profundus muscles. (n distal regions of the forearm, the ulnar ner'e

is immediately medial to the ulnar artery.

The ulnar artery lea'es the forearm, enters the hand y passing lateral to the pisiform

one and super&cial to the e#or retinaculum of the !rist, and arches o'er the palm. (t is

often the ma"or lood supply to the medial three and one3half digits.

Pulsations of the ulnar artery can e palpated on the lateral side of the e#or carpi

ulnaris tendon, !here it lies anterior to the ulnar head.

2igure 4. 9lnar artery and its ranches

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VEINS

EINS

The super&cial 'eins of the forearm lie in the super&cial fascia. Thecephalic vein

arises from the lateral side of the dorsal venous arch on the ac$ of the hand and

!inds around the lateral order of the forearm) it then ascends into the cuital fossa and

up the front of the arm on the lateral side of the iceps. (t terminates in the a#illary 'ein

in the deltopectoral triangle. %s the cephalic 'ein passes up the upper lim, it recei'es

a 'ariale numer of triutaries from the lateral and posterior surfaces of the lim.

The basilic vein arises from the medial side of the dorsal venous arch on the

ac$ of the hand and !inds around the medial order of the forearm) it then ascends into

the cuital fossa and up the front of the arm on the medial side of the iceps. (ts

terminates, y "oining the venae comitantes o the brachial artery to form the

a#illary 'ein. The median cubital vein, a ranch of the cephalic 'ein in the cuital fossa,

runs up!ard and medially and "oins the asilic 'ein. The asilic 'ein also recei'es a

'ariale numer of triutaries from the medial and posterior surfaces of the upper lim.

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1ranches of the ulnar artery that arise in the forearm include"

1) ulnar recurrent artery with anterior and posterior

branches, which contribute to an anastomotic networ) 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.


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2igures E F G. Heins in the anterior compartment of the forearm

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Deep 'eins accompanying arteries are plentiful in the forearm. These accompanying

'eins I. 'enae comitantes- arise from the anastomosing deep 'enous palmar arch in the

hand. 2rom the lateral side of the arch, paired radial 'eins arise and accompany the radial

artery) from the medial side, paired ulnar 'eins arise and accompany the ulnar artery. The

'eins accompanying each artery anastomose freely !ith each other. The radial and ulnar

'eins drain the forearm ut carry relati'ely little lood from the hand.

Deep 'eins of the anterior compartment drain into brachial veins associated !ith the

rachial artery in the cuital fossa.

NERVES

ERVES

=er'es in the anterior compartment of the forearm are the median and ulnar nerves,

and the supercial branch of the radial nerve.

MEDIAN NERVE

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The median nerve is the principal ner'e of the anterior compartment of the

forearm. (t supplies muscular ranches directly to the muscles of the super&cial and

intermediate layers of forearm e#ors e#cept the e#or carpi ulnaris-, and deep muscles

e#cept for the medial Julnar half of the e#or digitorum profundus) ring and little &ngers-

'ia its ranch, the anterior interosseous ner'e.

(t lea'es the cuital fossa y passing et!een the t!o heads of the pronator teres

muscle and passing et!een the humero3ulnar and radial heads of the e#or digitorum

super&cialis muscle. (t lea'es the forearm and enters the palm of the hand y passing

through the carpal tunnel deep to the e#or retinaculum.

The median ner'e has no ranches in the arm other than small t!igs to the rachial

artery. (ts ma"or ranch in the forearm is the anterior interosseous nerve.

1-#rticular branches: These ranches pass to the elo! "oint as the median ner'e

passes it.

8-$uscular branches% The ner'e to the pronator teres usually arises at the elo!. %

road undle of ner'es pierces the super&cial e#or group of muscles and inner'ates the

exor carpi radialis, palmaris longus, and exor digitorum supercialis.

>-#nterior interosseous nerve% The largest ranch of the median ner'e in the forearm

is the anterior interosseous nerve inner'ates the muscles in the deep layer exor

pollicis longus, the lateral half of exor digitorum profundus, and pronator

"uadratus-.

-&almar cutaneous branch of the median nerve% % small palmar ranch passes

super&cially into the hand and inner'ates the s'in over the base and central palm.

This palmar ranch is spared in carpal tunnel syndrome ecause it passes into the hand

super&cial to the e#or retinaculum of the !rist.

ULNAR NERVE

Ii$e the median ner'e, the ulnar nerve does not gi'e rise to ranches during its

passage through the arm. (n the forearm it supplies only one and a half muscles, the

exor carpi ulnaris muscle as it enters the forearm y passing et!een its t!o heads

of pro#imal attachment- and the ulnar (medial) part (ring and little ngers) of the

exor digitorum profundus muscle.

The ulnar ner'e enters the anterior compartment of the forearm y passing

posteriorly around the medial epicondyle of the humerus and et!een the humeral andulnar heads of the e#or carpi ulnaris muscle.

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(n the forearm the ulnar ner'e gi'es rise to:

1-Muscular ranches to the exor carpi ulnaris and to the medial half of the exor

digitorum profundus.

8-T!o small cutaneous ranches) palmar branch passes into the hand to supply s'in on

the medial side of the palm) larger dorsal branch inner'ates s'in on the

posteromedial side of the bac' of the hand and most s'in on the posterior

surfaces of the medial one and one*half digits.

2igure 1L. Median ner'e

http://.pureprecisionchiro.com/p'content/uploads/$411/4$/edian6ere.pg

RADIAL NERVE

9nli$e the medial and ulnar ner'es, the radial nerve ser'es motor and sensory

functions in oth the arm and the forearm ut only sensory functions in the hand-.

o!e'er, its sensory and motor &ers are distriuted in the forearm y t!o separate

96

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ranches, the super&cial sensory or cutaneous- and deep radial/posterior interosseous

ner'e motor-. The radial nerve ifurcates into deep and superfcial branches

anterior to the lateral epicondyle of the humerus, et!een the rachialis and the

rachioradialis, in the lateral order of the cuital fossa.

The deep branch is predominantly motor and passes et!een the t!o heads of the

supinator muscle to access and supply muscles in the posterior compartment of the

forearm.

The supercial branch of the radial nerve is sensory. (t passes do!n the

anterolateral aspect of the forearm deep to the rachioradialis muscle. The ner'e

continues into the hand !here it inner'ates s$in on the posterolateral surface.

2igure 11. 9lnar ner'e F adial ner'ehttp://#arate.butsu.net/anatomy/anterior0ie.html

'olarN anterior

LATERAL AND MEDIAL CUTANEOUS NERVES OF

FOREARM

The lateral cutaneous nerve of the forearm lateral anterachial cutaneous

ner'e- is the continuation of the musculocutaneous nerve after its motor ranches

ha'e all een gi'en oO to the muscles of the anterior compartment of the arm.

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The medial cutaneous nerve of the forearm medial anterachial cutaneous

ner'e- is an independent branch of the medial cord of the brachial plexus. 6ith

the posterior cutaneous nerve o the orearm from the radial nerve, each supplying

the area of s$in indicated y its name, these three ner'es pro'ide all the cutaneous

inner'ation of the forearm. There is no ?anterior cutaneous ner'e of the forearm.@

Memory de'ice: This is similar to the rachial ple#us, !hich has lateral, medial, and

posterior cords ut no anterior cord.-

2igures 18 F 1>. Iateral cutaneous ner'e of forearm

http://.loo#fordiagnosis.com/mesh0info.php7term8usculocutaneous96ere&lang81

http://.#mle.co.#r/search.php7earch8antebrachial&;age81

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http://www.lookfordiagnosis.com/mesh_info.php?term=Musculocutaneous+Nerve&lang=1http://www.kmle.co.kr/search.php?Search=antebrachial&Page=1http://www.lookfordiagnosis.com/mesh_info.php?term=Musculocutaneous+Nerve&lang=1http://www.kmle.co.kr/search.php?Search=antebrachial&Page=1


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%lthough the arteries, 'eins, and ner'es of the forearm ha'e een considered

separately, it is important to place them into their anatomical conte#t. B#cept for the

super&cial 'eins, !hich often course independently in the sucutaneous tissue, these

neuro'ascular structures usually e#ist as components of neuro'ascular undles. These

undles are composed of arteries, 'eins in the lims, usually in the form of

accompanying 'eins-, and ner'es as !ell as lymphatic 'essels, !hich are usually

surrounded y a neuro'ascular sheath of 'arying density.

Radial Ne!e I"#$ie%

The radial ner'e is commonly damaged in the a#illa and in the spiral groo'e.

I"#$ie% &' &(e Media" Ne!e a& &(e El)'*

M'&'

The pronator muscles of the forearm and the long e#or muscles of the !rist and

&ngers, !ith the e#ception of the e#or carpi ulnaris and the medial half of the e#or

digitorum profundus, !ill e paralyed. %s a result, the forearm is $ept in the supine

position) !rist e#ion is !ea$ and is accompanied y adduction. The latter de'iation is

caused y the paralysis of the e#or carpi radialis and the strength of the e#or carpi

ulnaris and the medial half of the e#or digitorum profundus. =o e#ion is possile at the

interphalangeal "oints of the inde# and middle &ngers, although !ea$ e#ion of the

metacarpophalangeal "oints of these &ngers is attemptedy the interossei. 6hen the

patient tries to ma$e &st, the inde# and to a lesser e#tent the middle &ngers tend to

remain straight, !hereas the ring and little &ngers e# . The latter t!o &ngers are,

ho!e'er, !ea$ened y the loss of the e#or digitorum super&cialis. 2le#ion of the

terminal phalan# of the thum is lost ecause of paralysis of the e#or pollicis longus. The

muscles of the thenar eminence are paralyed and !asted so that the eminence is

attened. The thum is laterally rotated and adducted. The hand loo$s attened and

?ape3li$e.@

Se"%'+

0$in 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 &ngers. 0ensory loss also occurs on the s$in of the

distal part of the dorsal surfaces of the lateral three and a half &ngers. The area of total

anesthesia is consideraly less ecause of the o'erlap of ad"acent ner'es.

2:

CLINICAL ANATOMY


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Va%','&' C(a"-e%

The s$in areas in'ol'ed in sensory loss are !armer and drier than normal ecause of the

arteriolar dilatation and asence of s!eating resulting from loss of sympathetic control.

T'(i/ C(a"-e%

(n long3standing cases, changes are found in the hand and &ngers. The s$in is dry and

scaly, the nails crac$ easily, and atrophy of the pulp of the &ngers is present.

P'"a&' S+"d',e

&ronator syndrome, a ner'e entrapment syndrome, is caused y compression of the

median ner'e near the elo!. The ner'e may e compressed et!een the heads of the

pronator teres as a result of trauma, muscular hypertrophy, or &rous ands. (ndi'iduals

!ith this syndrome are &rst seen clinically !ith pain and tenderness in the pro#imalaspect of the anterior forearm and hypesthesia of palmar aspects of the radial three and

half digits and ad"acent palm. 0ymptoms often follo! acti'ities that in'ol'e repeated

pronation.

"&ei' i"&e'%%e'$% "e!e %+"d',e

The anterior interosseous nerve an entirely motor ranch of the median ner'e-

pro'ides motor inner'ation to the e#or pollicis longus 2PI-, e#or digitorum profundus

2DP- to the inde# and sometimes middle &ngers, and to the pronator *uadratus PQ-.

Paralysis of these muscles from a complete ner'e palsy !ill result in a pinch deformity,

though !ea$ness of pronation may e mas$ed y the concurrent action of the pronator

teres PT-. % case report R http://!!!.sma.org.sg/sm"/18/18cr1.pdf

I"#$ie% &' &(e Ul"a Ne!e a& &(e El)'*

M'&'

The e#or carpi ulnaris and the medial half of the e#or digitorum profundus

muscles are paralyed. The paralysis of the e#or carpi ulnaris can e oser'ed y as$ing

the patient to ma$e a tightly clenched &st. =ormally, the synergistic action of the e#or

carpi ulnaris tendon can e oser'ed as it passes to the pisiform one) the tightening of

the tendon !ill e asent if the muscle is paralyed. The profundus tendons to the ring

and little &ngers !ill e functionless, and the terminal phalanges of these &ngers are

therefore not capale of

eing mar$edly e#ed. 2le#ion of the !rist "oint !ill result in aduction, o!ing to paralysisof the e#or carpi ulnaris.

29

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The medial order of the front of the forearm !ill sho! attening, o!ing to the

!asting of the underlying ulnaris and profundus muscles. The small muscles of the hand

!ill e paralyed, e#cept the muscles of the thenar eminence and the &rst t!o

lumricals,!hich are supplied y the median ner'e. The patient is unale to adduct and

aduct the &ngers and conse*uently is unale to grip a piece of paper placed et!een

the &ngers. ememer that the e#tensor digitorum can aduct the &ngers to a small

e#tent, ut only !hen the metacarpophalangeal "oints are hypere#tended.(t is impossile

to adduct the thum ecause the adductor pollicis muscle is paralyed. (f the patient is

as$ed to grip a piece of paper et!een the thum and the

inde# &nger, he or she does so y strongly contracting the e#or pollicis longus and

e#ing the terminal phalan# 2romentSs sign-.

The metacarpophalangeal "oints ecome hypere#tended ecause of the paralysis of

the lumrical and

interosseous muscles, !hich normally e# these "oints. ecause the &rst and second

lumricals are not paralyed they are supplied y the median ner'e-, the hypere#tension

of the metacarpophalangeal "oints is most prominent in the fourth and &fth &ngers. The

interphalangeal "oints are e#ed, o!ing again to the paralysis of the lumrical and

interosseous muscles, !hich normally e#tend these "oints through the e#tensor

e#pansion. The e#ion deformity at the interphalangeal "oints of the fourth and &fth

&ngers is o'ious ecause the &rst and second lumrical muscles of the inde# and middle

&ngers are not paralyed. (n longstanding

cases the hand assumes the characteristic ?cla!@ deformity main en griOe-. 6asting of

the paralyed muscles

results in attening of the hypothenar eminence and loss of the con'e# cur'e to the

medial order of the hand.

B#amination of the dorsum of the hand !ill sho! hollo!ing et!een the metacarpalones caused y !asting of the dorsal interosseous muscles.

Se"%'+

Ioss of s$in sensation !ill e oser'ed o'er the anterior and posterior surfaces of the

medial third of the hand and the medial one and a half &ngers.

Va%','&' C(a"-e%

The s$in areas in'ol'ed in sensory loss are !armer and drier than normal ecause of the

arteriolar dilatation and asence of s!eating resulting from loss of sympathetic control.

22


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C',,$"i/a&i'"% Be&*ee" Media" a"d Ul"a Ne!e%

Accasionally, communications occur et!een the median and the ulnar ner'es in the

forearm. These ranches are usually represented y slender ner'es, ut the

communications are important clinically ecause e'en !ith a complete lesion of the

median ner'e, some muscles may not e paralyed. This may lead to an erroneous

conclusion that the median ner'e has not een damaged.

Mea%$i"- P$l%e Ra&e

The common place for measuring the pulse rate is !here the radial artery lies on the

anterior surface of the distal end of the radius, pro#imal to the !rist, et!een the tendons

of the exor carpi radialis and brachioradialis. ere the artery is co'ered y onlyfascia and s$in. The artery can e compressed against the distal end of the radius, !here

it lies et!een the tendons of the e#or carpi radialis and aductor pollicis longus. 6hen

measuring the radial pulse rate, the pulp of the thum should not e used ecause it has

its o!n pulse, !hich could oscure the patient7s pulse. (f a pulse cannot e felt, try the

other !rist ecause an aerrant radial artery on one side may ma$e the pulse di+cult to

palpate. % radial pulse may also e felt y pressing lightly in the anatomical snuO o#

et!een the e#tensor pollicus longus and re'is muscles.

The cubital fossa is an important area of transition et!een the arm and the

forearm. The cuital fossa is seen super&cially as a depression on the anterior aspect of

the elo!. Deeply, it is a space &lled !ith a 'ariale amount of fat anterior to the most

distal part of the humerus and the elo! "oint.

• 0uperiorly, an imaginary line connecting the medial and lateral epicondyles.

• Medially, the mass of e#or muscles of the forearm arising from the common e#or

attachment on the medial epicondyle) most speci&cally, the pronator teres.

• Iaterally, the mass of e#tensor muscles of the forearm arising from the lateral

epicondyle and supraepicondylar ridge) most speci&cally, the brachioradialis.

%s a summary, the pronator teres ma$es the medial order, !hereas the rachioradialis

ma$es the lateral one.

The oor of the cuital fossa is formed y the rachialis and supinator muscles of the armand forearm, respecti'ely. The roof of the cuital fossa is formed y the continuity of

2

0. CUBITAL FOSSA


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rachial and anterachial deep- fascia reinforced y the icipital aponeurosis,

sucutaneous tissue, and s$in.

The contents of the cuital fossa are the:

• Terminal part of the rachial artery and the commencement of its terminal ranches,

the radial and ulnar arteries. The rachial artery lies et!een the iceps tendon and

the median ner'e.

• Deep- accompanying 'eins of the arteries

• iceps rachii tendon

• Median ner'e

• adial ner'e

0uper&cially, in the sucutaneous tissue o'erlying the fossa are the median cuital 'ein,

lying anterior to the rachial artery, and the medial and lateral anterachial cutaneous

ner'es, related to the asilic and cephalic 'eins.

The supratrochlear lymph node lies in the super&cial fascia o'er the upper part

of the fossa, ao'e the trochlea. (t recei'es aOerent lymph 'essels from the third, fourth,

and &fth &ngers) the medial part of the hand) and the medial side of the forearm. The

eOerent lymph 'essels pass up to the a#illa and enter the lateral a#illary nodes The

supercial lymph vessels from the thum! and lateral ngers and the lateral areas of the

hand and forearm follo" the cephalic vein to the infraclavicular group of nodes. Those

from the medial ngers and the medial areas of the hand and forearm follo" the !asilic

vein to the cu!ital fossa-.

The brachial artery normally ifurcates into the radial and ulnar arteries in the

ape# of the fossa, although this ifurcation may occur much higher in the arm, e'en in

the a#illa. 6hen ta$ing a lood pressure reading from a patient, the clinician places the

stethoscope o'er the brachial artery in the cubital fossa.

The median nerve lies immediately medial to the rachial artery and lea'es the

fossa y passing et!een the ulnar and humeral heads of the pronator teres muscle.

The rachial artery and the median ner'e are co'ered and protected anteriorly in

the distal part of the cuital fossa y the icipital aponeurosis. This at connecti'e tissue

memrane passes et!een the medial side of the tendon of the iceps rachii muscle

and deep fascia of the forearm. The sharp medial margin of the icipital aponeurosis can

often e felt.

23


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The radial nerve lies "ust under the lip of the rachioradialis muscle, !hich forms

the lateral margin of the fossa. (n the cuital fossa the radial nerve gi'es oO the deep

ranch of the radial ner'e and continues as the super&cial radial ner'e. The deep ranch

supplies the e#tensor carpi radialis re'is and the supinator in the cuital fossa and all

the e#tensor muscles in the posterior compartment of the forearm.

The ulnar ner'e does not pass through the cuital fossa. (nstead, it passes posterior to

the medial epicondyle.

The roof of the cuital fossa is formed y super&cial fascia and s$in. The most

important structure !ithin the roof is the median cubital vein, !hich passes diagonally

across the roof and connects the cephalic 'ein on the lateral side of the upper lim !ith

the asilic 'ein on the medial side. The icipital aponeurosis separates the median cuital

'ein from the rachial artery and median ner'e. Ather structures !ithin the roof are

cutaneous ner'es)3the medial cutaneous and lateral cutaneous nerves of the

forearm.

2igure 1. uital fossa

http://.daiddarling.info/images$/cubital0fossa.pg

24

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Tale 1. Muscles of the anterior compartment of the forearm super&cial and intermediatelayers-

25

+upercial (rst) layer

&ronator teres Median ner'e Pronates ande#es forearm atelo!-

9lnar head oronoid process Iateral surface of radiusumeral head Medial

epicondyle andad"acentsupraepicondylarridge

lexor carpiradialis (-)

Medialepicondyle ofhumerus

ase ofmetacarpals ((and (((

2le#es andaducts hand at!rist-

&almarislongus

Medialepicondyle of

humeruscommon e#ororigin-

2le#orretinaculum and

palmaraponeurosis

2le#es hand at!rist- and tenses

palmaraponeurosis

lexor carpiulnaris (-/)umeral head Medial

epicondyle ofhumerus

•Pisiform F

hamate

• ;th metacarpal

9lnar ner'e

2le#es andadducts the !rist

"oint9lnar head • Alecranon

• Posterior

order of ulna

ntermediate (second) layerlexor digitorum supercialis (+)umeroulnarhead

• Medial

epicondyle ofhumerus

• %d"acent

margin ofcoronoidprocess

0hafts of middlephalanges ofmedial four digits

Median ner'e 2le#es pro#imalinterphalangeal

"oints of theinde#, middle,ring, and little&ngers) can alsoe#metacarpophalangeal "oints of the

same &ngers andthe !rist "oint

adial head 0uperior half of

anterior order


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Tale 8. Muscles of the anterior compartment of the forearm deep layer-

26

$uscle&roximal#ttachment

istal#ttachment nnervation $ain #ction

$uscle &roximal#ttachment

istal#ttachment

nnervation $ain #ction

lexor digitorum profundus (&)

Medial part Pro#imal three*uarters ofmedial andanterior surfacesof ulna andinterosseousmemrane

ases of distalphalanges of thand ;th digits

9lnar ner'e 2le#es distalphalanges and; at distalinterphalangeal

"ointsIateral part ases of distal

phalanges of 8ndand >rd digits

%nteriorinterosseousner'e, frommedian ner'e

2le#es distalphalanges 8 and> at distalinterphalangeal

"ointslexor pollicislongus (&)

%nterior surfaceof radius andad"acentinterosseousmemrane

ase of distalphalan# of thum

2le#es phalangesof 1st digitthum-

&ronator"uadratus

Distal *uarter ofanterior surfaceof ulna

Distal *uarter ofanterior surfaceof radius

Pronates forearm)deep &ers indradius and ulnatogether


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Anterior Aspect of the Forearm Cubital Fossa 2012

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