Prof. Saeed Abuel Prof. Saeed Abuel MakaremMakarem

FOREARM

objectivesobjectives

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

Enumerates the group of muscles forming the forearm.Enumerates the group of muscles forming the forearm. Arrange these muscles into anterior (flexors) and Arrange these muscles into anterior (flexors) and

posterior (extensors).posterior (extensors). Enumerate each of these groups of muscles into Enumerate each of these groups of muscles into

superficial and deep muscles.superficial and deep muscles. Remember the nerve supply and action of these Remember the nerve supply and action of these

muscles.muscles.

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

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

The 2 bones articulating The 2 bones articulating with each other in with each other in superior and inferior superior and inferior radioulnar joints.radioulnar joints.

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

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

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

Fascial Compartments of the Forearm

The forearm is enclosed in a sheath of deep fascia.The deep fascia is attached to posterior subcutaneous border of the ulna .This fascial sheath, together with the interosseous membrane & intermuscular septa, divides the forearm into several compartments, each having its own muscles, nerves, and blood supply.

I-Superficial: I-Superficial: 441.1. Pronator teres.Pronator teres.2.2. Flexor carpi Flexor carpi

radialis.radialis.3.3. Palmaris longus.Palmaris longus.4.4. Flexor carpi ulnaris.Flexor carpi ulnaris.

II-Intermediate: II-Intermediate: 11 Flexor digitorum Flexor digitorum

superficialis.superficialis.

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

III- Deep: III- Deep: 33

1.1. Flexor digitorum Flexor digitorum profundus.profundus.

2.2. Flexor pollicis longus.Flexor pollicis longus.

3.3. Pronator quadratus.Pronator quadratus.

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 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 of Base of 22ndnd metacarpal metacarpal bonebone

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

Palmaris Palmaris LongusLongusInsertionInsertion:: into the into the

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

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

May Be Absent

Flexor Flexor RetinaculumRetinaculum

Thick band of deep fascia Thick band of deep fascia infront of the wrist joint.infront of the wrist joint.

It keeps the long flexor tendons It keeps the long flexor tendons in position.in position.

Structures passing Structures passing superficial to the superficial to the retinaculum, from medial to retinaculum, from medial to lateral:lateral:

11. Ulnar nerve.. Ulnar nerve.

2. Ulnar artery.2. Ulnar artery.

3. Palmar cutaneous branch of 3. Palmar cutaneous branch of ulnar.ulnar.

4. Tendon of palmaris longus.4. Tendon of palmaris longus.

5. Palmar cutaneous branch of 5. Palmar cutaneous branch of median nerve.median nerve.

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 surface of radius

• InsertionInsertion::• Base of

middle phalanges of the medial 4 fingers..

• ActionAction:: • Flexes middle Flexes middle

and proximal and proximal phalanges of phalanges of medial 4 medial 4 fingers, and fingers, and the hand the hand (wrist).(wrist).

Deep FlexorsDeep Flexors One above radiusOne above radius: :

Flexor pollicis Flexor pollicis longus.longus.

One above ulnaOne above ulna: : Flexor Digitorum Flexor Digitorum profundus.profundus.

One above the two One above the two

bones:bones:

Pronator Quadratus.Pronator Quadratus.

Flexor Flexor Digitorum Digitorum Profundus Profundus ((Double nerve Double nerve supply).supply).

InsertionInsertion: bases : bases of the distal of the distal phalanges of the phalanges of the medial four medial four digitsdigits

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

Flexor Pollicis Flexor Pollicis LongusLongus

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

ActionAction: flexes : flexes interphalangeal, interphalangeal, metacarpophalangmetacarpophalangeal & eal & carpometacarpal carpometacarpal joints of thumb joints of thumb

Pronator Pronator QuadratusQuadratus• InsertionInsertion: :

distal fourth distal fourth of ant. surface of ant. surface of radiusof radius

• ActionAction: : pronates pronates forearm forearm (primover), (primover), helps to hold helps to hold the bones the bones together together

Supination and

pronation

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

Muscles produce supination

Biceps brachii, (flexed elbow Supinator, (extended elbow)

Muscles produce pronation

Pronator teres. pronator quadratus.

NB. Brachioradialis put the forearm in midprone-supine position.

Posterior compartment: 3 groupsSuperficial group 5

Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnarisAnconeus

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 2BrachioradialisExtensor carpi radialis longus(The 2 muscles originate from the lateral supracondylar ridge).

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

lateral to medial)lateral to medial) Brachioradialis, (BR).Brachioradialis, (BR). Extensor carpi radialis Extensor carpi radialis

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

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

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

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

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

Superficial Superficial extensorsextensors

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, 3 , 3 (BR, (BR, EXRL & anconeus).EXRL & anconeus).

All cross the wrist All cross the wrist EXCEPTEXCEPT, , 22, , (brachioradialis (brachioradialis & Anconeus)& Anconeus)

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

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

longus.longus. These 3 muscles are These 3 muscles are

supplied by the radial nerve supplied by the radial nerve itselfitself

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 supine 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 (deep branch of radial 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 & dorsal interossei and lumbricals muscles. All these tendons unite to form one tendon above the proximal phalanges. Then each divides into 3 slips, a median one attached to middle phalanges and 2 lateral attached to the terminal phalanges.

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