1Kaan Yücel M.D., Ph.D 28.December.2012 Friday

POSTERIOR ASPECT OF THE FOREARM

IN 7 QUESTIONS

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1. How are the muscles in the posterior compartment estabslihed?

In two layers: a superficial layera deep layer.

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2. Which muscles are in the superficial layer?

Common origin lateral epicondyle of the humerus Except for the brachioradialis and anconeus, extend as tendons into the hand.

Brachioradialis

Extensor carpi radialis longusExtensor carpi radialis brevisExtensor carpi ulnarisExtensor digitorum

Extensor digiti minimi

Base of 2nd metacarpal

Base of 3rd metacarpalBase of 5th metacarpal

Anconeus

Proximal part of supraepicondylar ridge of humerus

Lateral surface of distal end of radius proximal to styloid process

Distal part of supraepicondylar ridge of humerus

Base of 2nd metacarpal

Lateral epicondyle of humerus common extensor origin

Base of 3rd metacarpals

Lateral epicondyle of humerus common extensor origin

Base of the 5th metacarpal

Lateral epicondyle of humerus

dorsal aspects of the bases of the middle and distal phalanges of the medial four digits

Lateral epicondyle of humerus

Extensor expansion (hood) of the 5th digit

Lateral epicondyle of humerus

Olecranon and proximal posterior surface of ulna

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3. Which muscles are in the deep layer?

Except for the supinator muscle, all these deep layer muscles originate from the posterior surfaces of the radius, ulna, and interosseous membrane and pass into the thumb and fingers.

Supinator

Abductor pollicis longus

Extensor pollicis brevisExtensor pollicis longus

Extensor indicis

Superficial (humeroulnar) head•lateral epicondyle of humerus•radial collateral and anular ligaments Deep (ulnar) head Supinator crest of the ulna

Lateral surface of radius superior to the anterior oblique line

Posterior surface of proximal halves of ulna, radius, and interosseous membrane

Base of 1st metacarpal

Posterior surface of middle third of ulna and interosseous membraneDorsal surface of base of distal phalanx of thumb

Posterior surface of distal third of radius and interosseous membraneDorsal surface of base of proximal phalanx of the thumb

Posterior surface of distal 1/3 of ulna and interosseous membrane

Extensor expansion (hood) of 2nd digit

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4. What movements do these muscles do?

EXTENSION OF THE HAND & FINGERSABDUCTION OF THE FINGERSSUPINATION

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5. How are the muscles of the posterior compartment of the forearm innervated?BrachioradialisExtensor carpi radialis longusRadial nerve (Main nerve)

Supinator Extensor carpi radialis brevisDeep branch of radial nerve

RestPosterior interosseous nervecontinuation of deep branch of radial nerve

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6. ....arteries in the posterior compartment of the forearm?Radial artery

Posterior interosseous artery

origin: common interosseous branch of

the ulnar arteryrecurrent interosseous arteryEnd by joining to dorsal carpal arch of the wrist

Anterior interosseous artery

origin: common interosseous branch of the ulnar artery

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7. ...radial nerve in the posterior compartment of forearm?Deep branch becomes posterior interosseous nerve after emerging from between 2 heads of supinator

Posterior interosseous nerve passes deep to extensor pollicis longus to reach the wrist.