DaVinci medical academy

No 55/2, New Avadi Road, Alagappa Nagar, Kilpauk. Chennai

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  • 31 October, 2020

FOREARM

  • The forearm is divided into two compartments
    • A ventromedial or flexor compartment
    • A dorsolateral or extensor compartment.
  • Muscles of the forearm segregate into these compartments consisting of
    • (1) An anterior group (the flexors of the wrist and fingers and the pronators)
    • (2) A posterior group (the extensors of the wrist and fingers and the supinator)
  • Muscles of anterior forearm
    • Superficial – 4 muscles
    • Intermediate – 1 muscle
    • Deep- 3 muscles
  • Superficial group – arises mostly from a common flexor tendon that attaches to the anterior part of the medial epicondyle of the humerus, and from adjacent fascia. These muscles are supplied chiefly by the median nerve
    • Pronator teres (pierced by median nerve)
    • Flexor carpi radialis
    • Palmaris longus
    • Flexor carpi ulnaris
  • Intermediate muscle- arises from this common tendon and along the anterior surface of the ulna and radius and is also supplied by the median nerve.
    • Flexor digitorum superficialis
  • Deep group – is supplied mostly by a branch of the median nerve(the anterior interosseous nerve)
    • Flexor pollicis longus
    • Flexor digitorum profundus
    • Pronator quadratus

NOTE

  • Those muscles in the superficial and deep groups that are not innervated by the median (i.e., the flexor carpi ulnaris and the ulnar part of the flexor digitorum profundus) are supplied by the ulnar nerve.

CLINICAL EDGE

Volkmann’s ischemic contracture

  •  Increased pressure in the anterior compartment of the forearm, like in an instance, injury to the brachial artery near the elbow (e.g., from a supracondylar fracture of the humerus) can prevent normal blood flow to the compartment and ischemic damage to the deep flexors (pollicis longus and digitorum profundus).
  • This can cause muscle scarring, with flexion deformity of the wrist and fingers

 KEYNOTE

  • Flexion at elbow- by all superficial muscles
  • Flexion at wrist- flexor carpi radialis,flexor carpi ulnaris and Palmaris longus
  • Flexion at finger – flexor digitorum superficialis and flexor digitorum profundus
  • Pronation- pronator teres and pronator quadratus

MUSCLES OF THE POSTERIOR FOREARM

KEYNOTE:

  • Muscles helping in supination- supinator, biceps brachii,brachioradialis
  • Paralysis of extensor muscle leads to wrist drop + finger drop