1

FOREARM

By Prof. Saeed Abuel MakaremDr. Sanaa Al-Sharawy

By the end of the lecture the By the end of the lecture the student should be able to:student should be able to:

Enumerate the different muscles of the Enumerate the different muscles of the front (flexors) and back (extensors) of front (flexors) and back (extensors) of the forearm.the forearm.

Describe in brief the attachment of Describe in brief the attachment of these group these group of muscles:of muscles:

Superficial and deep flexors; Superficial and deep flexors; Superficial and deep extensors.Superficial and deep extensors. Describe the action and nerve supply of Describe the action and nerve supply of

each of these muscle.each of these muscle.

OBJECTIVES

The forearm extends from extends from elbowelbow to to wristwrist..

It posses two bones It posses two bones radius laterally & Ulna radius laterally & Ulna medially.medially.

The two bones are The two bones are connected together connected together by the interosseous by the interosseous membrane. membrane.

This membrane This membrane allows movement of allows movement of Pronation and and Supination while while the two bones are the two bones are connected together.connected together.

Also it gives origin for Also it gives origin for the deep muscles.the deep muscles.

Fascial Compartments of the Forearm

The forearm is enclosed in a sheath of deep fascia, which is attached to the post. subcutaneous border of the ulna . This fascial sheath, together with the interosseous membrane, radius & ulna and a fibrous intermuscular septum divides the forearm into several compartments.Each compartments have its own muscles, nerves, and blood supply.

I-Superficial: 4I-Superficial: 4 Pronator teresPronator teres Flexor carpi Flexor carpi

radialisradialis Palmaris longusPalmaris longus Flexor carpi ulnarisFlexor carpi ulnaris

II-Intermediate: 1II-Intermediate: 1 Flexor digitorum Flexor digitorum

superficialissuperficialis

These muscles: are (8)•They act on the wrist & elbow joints and the fingers.•They form fleshy masses in the proximal forearm and become tendinous in the distal part of the forearm.•They are arranged in three groups:

III- Deep: 3III- Deep: 3 Flexor digitorum Flexor digitorum

profundus. profundus. UU Flexor pollicis longus. Flexor pollicis longus.

RR Pronator quadratus. Pronator quadratus. R R

& U& U

Anterior compartment -FLEXOR GROUP

Superficial FlexorsSuperficial Flexors They arise - more or They arise - more or

less- from the less- from the common flexor origin common flexor origin (front of (front of medial medial epicondyleepicondyle).).

All are supplied by All are supplied by the the medianmedian nerve nerve exceptexcept one,one, flexor flexor carpi ulnaris,carpi ulnaris, FCU FCU (ulnar n.).(ulnar n.).

All cross the wrist All cross the wrist joint joint except oneexcept one, , pronator teres,pronator teres, (PT). (PT).

Pronator Pronator teres teres Insertion:Insertion: middle of lat. middle of lat. surface of surface of radiusradius

ActionAction:: pronation & pronation & flexion of flexion of forearm .forearm .

Flexor Carpi Flexor Carpi Radialis Radialis

InsertionInsertion:: Base Base of 2of 2ndnd metacarpal metacarpal bonebone

ActionAction: Flexion & : Flexion & abduction of the abduction of the wrist.wrist.

Palmaris Palmaris LongusLongusInsertionInsertion:: into the into the

flexor flexor retinaculum & retinaculum & palmer palmer aponeurosis.aponeurosis.

ActionAction:: Flexes hand Flexes hand & tightens the & tightens the palmer palmer aponeurosisaponeurosis

May Be Absent

Flexor Carpi Flexor Carpi UlnarisUlnaris

InsertionInsertion:: Pisiform, Pisiform, hook of hook of

hamate hamate 55thth

metacarpal metacarpal bonebone

ActionAction:: Flexion and Flexion and

adduction of adduction of the hand the hand (wrist)(wrist)

Flexor Flexor Digitorum Digitorum SuperficialisSuperficialis• Origin:Origin:• Common Common

flexor origin, flexor origin, • Coronoid Coronoid

process of process of ulna;ulna;

• Anterior oblique line of radius

• InsertionInsertion::• base of base of

middle middle phalanges of phalanges of the medial 4 the medial 4 fingers.fingers.

• ActionAction:: • Flexes Flexes

middle and middle and proximal proximal phalanges of phalanges of medial 4 medial 4 fingersfingers

• Flexes the Flexes the hand (wrist).hand (wrist).

Deep FlexorsDeep Flexors One above radiusOne above radius: :

Flexor pollicis Flexor pollicis longuslongus

One above ulnaOne above ulna: : Flexor Digitorum Flexor Digitorum profundusprofundus

One above the twoOne above the two

bones:bones:

Pronator Quadratus.Pronator Quadratus.

Flexor Digitorum Flexor Digitorum ProfundusProfundus

InsertionInsertion: bases : bases of the distal of the distal phalanges of the phalanges of the medial four digitsmedial four digits

ActionAction: Flexes : Flexes distal phalanges distal phalanges of medial four of medial four digitsdigits

Flexor Pollicis Flexor Pollicis LongusLongus

InsertionInsertion: Base of : Base of distal phalanx of distal phalanx of thumbthumb

ActionAction: flexes (all : flexes (all joints of the joints of the thumb), thumb), interphalangeal, interphalangeal, metacarpophalangmetacarpophalangeal & eal & carpometacarpal carpometacarpal joints. joints.

Pronator Pronator QuadratusQuadratus• InsertionInsertion: :

distal one distal one fourth of ant. fourth of ant. surface of surface of radiusradius

• ActionAction: : pronates the pronates the forearm forearm (primover), (primover),

• Hold the two Hold the two bones bones together together

Supination and

pronation

It occurs in the superior and inferior radioulnar joints; (pivot synovial joint)

Muscles produce supination

Biceps brachii. Supinator.

Muscles produce pronation

Pronator teres. pronator quadratus.NB. Brachioradialis put the forearm in midprone-supine position, (initiates pronation and supination).

Posterior Compartment: 3 groups

Superficial group 51. Extensor carpi radialis brevis.2. Extensor digitorum .3. Extensor digiti minimi.4. Extensor carpi ulnaris.5.Anconeus .

Deep group 5 (3 to thumb+ 1 to index + supinator).Supinator.Abductor pollicis longus. Extensor pollicis brevis.Extensor pollicis longus.Extensor indices.

Origin: Common Extensor Origin (front of the lateral epicondyle).

Lateral group 21.Brachioradialis.2.Extensor carpi radialis longus.(These two muscles arises from the lateral supracondylar ridge).

Posterior compartmentPosterior compartment I- Superficial group:I- Superficial group: 7 muscles 7 muscles ( from ( from

laterallateral to medial)to medial)1.1. Brachioradialis, (BR).Brachioradialis, (BR).2.2. Extensor carpi radialis Extensor carpi radialis

longus, (ECRL).longus, (ECRL).3.3. Extensor carpi radialis Extensor carpi radialis

brevis, (ECRB).brevis, (ECRB).4.4. Extensor digitorum, Extensor digitorum,

(ED).(ED).5.5. Extensor digiti minimi, Extensor digiti minimi,

(EDM).(EDM).6.6. Extensor carpi ulnaris, Extensor carpi ulnaris,

(ECU).(ECU).7.7. Anconeus. (An).Anconeus. (An).

Superficial Superficial extensorextensor

All arises from the All arises from the commoncommon extensor originextensor origin, (, (front of front of lateral epicondylelateral epicondyle of the of the humerus), humerus), EXCEPTEXCEPT, 2 , 2 (BR (BR & EXRL).& EXRL).

All cross the wrist All cross the wrist EXCEPTEXCEPT, , one,one, (brachioradialis. (brachioradialis.

All supplied by deep branch All supplied by deep branch of radial nerve, of radial nerve, EXCEPTEXCEPT ABEABE

AA,, Anconeus Anconeus BB,, Brachioradialis Brachioradialis EE,, Extensor carpi radialis Extensor carpi radialis

longuslongus These 3 muscles are These 3 muscles are

supplied by the radial supplied by the radial nerve itselfnerve itself

BrachioradBrachioradialisialis

Origin:Origin: Lateral

supracondylar ridge of humerus

Insertion: Insertion: Base of styloid

process of radius

ActionAction:: Flexes

forearm; (elbow).

Rotates forearm to the midprone position

Extensor Extensor Carpi Carpi radialis radialis longuslongus

Origin:Origin: Lateral

supracondylar ridge of humerus

Insertion: Insertion: Posterior

surface of base of second metacarpal bone

ActionAction:: Extends and

abducts hand at wrist joint

Extensor carpi radialis brevis: base of 3rd metacarpal bone.Extensor digitorum: Extensor expansion of the medial 4 fingers.Extensor digiti minimi: Extensor expansion of the little finger.Extensor carpi ulnaris:Base of the 5th metacarpal bone.

INSERTION

II- Deep group: 5 muscles 1- Abductor pollicis longus, (APL). 2- Extensor pollicis brevis, (EPB). 3- Extensor pollicis longus, (EPL). 4- Extensor indicis (EI). 5- Supinator.All back muscles of forearm are supplied by posterior interosseous nerve except , ABE by Radial nerve.

Dorsal Extensor Expansion

It is formed by the union of the tendons of: Extensor digitorum, Extensor indicis, extensor digiti minimi, palmar interossei, dorsal interossei and lumbricals muscles. All these tendons unite to form one tendon which divides into 3 slips, a median one attached to middle phalanges and 2 lateral attached to the terminal phalanges.

May I please be excused? My brain is full” HAHH