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Extensor Side of the forearm and Hand

Extensor Side of the forearm and Hand. Phil Pullen, D.O. Garden City Hospital Orthopaedic Surgery Resident. Extensor muscles of the forearm. Can be divided into 3 functional groups:

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Extensor Side of the forearm and Hand

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  1. Extensor Side of the forearm and Hand Phil Pullen, D.O. Garden City Hospital Orthopaedic Surgery Resident

  2. Extensor muscles of the forearm • Can be divided into 3 functional groups: • Muscles that extend and abduct or adduct the hand (extensor carpi radialis longus, extensor carpi radialis brevis, and ext. carpi ulnaris) • Muscles that extend the medial 4 digits (ext digitorum, ext indicis, and ext digiti minimi) • Muscles that extend or abduct the thumb (abductor pollicis longus, ext pollicis brevis, and ext pollicis longus)

  3. Muscles • Brachioradialis: • origin – lateral supracondylar ridge of the humerus • Insertion- lateral surface of distal end of radius • Innervation – radial nerve • Action –flexes the forearm • Extensor Carpi Radialis Longus: • Origin – lateral supracondylar ridge • Insertion-base of 2nd MC • Innervation- radial nerve • Action- extend and abduct at wrist

  4. Muscles • Extensor Carpi Radialis Brevis: • Origin – lateral epicondyle of humerus • Insertion- base of 3rd MC • Innervation – deep branch of radial n. • Action – extend and abduct at wrist • Extensor Digitorum • Origin – lateral epicondyle • Insertion – extensor expansions of medial four digits • Innervation – posterior interosseus • Action – extends medial 4 digits at MCP and extends wrist

  5. Muscles • Extensor Digiti Minimi • Origin – lateral epicondyle • Insertion – extensor expansion of 5th digit • Innervation – posterior interosseus • Action – extends 5th digit at MCP and IP joints • Extensor Carpi Ulnaris • Origin – lateral epicondyle • Insertion – base of 5th MC • Innervation – post interosseus • Action – extends and adducts at wrist

  6. Muscles • Supinator: • Origin – lateral epicondyle and posterior border of the ulna • Insertion – lateral, post., and ant. Surfaces of the prox. 3rd of the radius • Innervation – deep branch of the radial • Action- supinates the forearm

  7. Muscles • Abductor Pollicis Longus: • Origin – post surfaces of ulna, radius and interosseus membrane • Insertion – base of 1st MC • Innervation – post interosseus • Action – abducts thumb and extends at the CMC joint

  8. Muscles • Extensor Pollicis Brevis • Origin – post surface of the radius and interosseus membrane • Insertion – base of prox phalanx of thumb • Innervation – post interosseus • Action – extends prox phalanx of thumb at CMC joint • Extensor Pollicis Longus • Origin – post surface of middle 3rd of ulna and interosseus membrane • Insertion – base of distal phalanx of thumb • Innervation – post interosseus • Action – extends distal phalanx of thumb at MCP and IP joints

  9. Muscles • Extensor Indicis • Origin – post surface of ulna and interosseus membrane • Insertion – extensor expansion of 2nd digit • Innervation – post interosseus • Action – extends 2nd digit and helps to extend hand

  10. Extensor mechanism • At the distal end of the MC and along the phalanges, the ext tendons flatten out to form the extensor expansions • Each ext digital expansion is a triangular tendinous aponeurosis that wraps around the dorsum of the head of the MC and prox phalanx

  11. Extensor mechanism • The hood is anchored on both sides to the palmar ligament to hold the tendon in the middle of the digit • This expansion divides into a median band that passes to the base of the middle phalanx • And 2 lateral bands that pass to the base of the distal phalanx

  12. Extensor mechanism • The interosseus and lumbrical muscles attach to the lateral bands of the extensor expansion

  13. Extensor Compartments • I – abductor pollicis longus, extensor pollicis brevis • II – extensor carpi radialis longus and brevis • III – extensor pollicis longus • IV – extensor digitorum, extensor indicis • V – extensor digiti minimi • VI – extensor carpi ulnaris

  14. Extensor Side of the Hand

  15. Nerves • Radial nerve leaves the posterior compartment of the arm to cross the anterior aspect of the lateral epicondyle • After it enters the forearm it branches into the deep and superficial branches and the posterior cutaneous nerve of the forearm • Nerve supply to the extensor muscles includes the radial nerve, the deep branch of the radial nerve and the posterior interosseus nerve which is a continuation of the deep branch of the radial nerve

  16. Cutaneous Nerves and Superficial Veins of the Forearm

  17. Arterial Supply to Extensor Side of Forearm • The arterial supply to the extensors of the forearm come from branches from the ulnar artery, namely the posterior interosseus artery with its muscular branches • The ulnar artery (the larger of two branches of the brachial artery) begins in the cubital fossa just medial to the biceps tendon

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