What is the functional anatomy of phalanges?

Updated: Jan 18, 2018
  • Author: Jay E Bowen, DO; Chief Editor: Craig C Young, MD  more...
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Answer

The lumbricals are 4 muscles that arise from the tendons of flexor digitorum profundus. Their tendons insert into the radial side of each of the proximal phalanges of the fingers and into the dorsal hood. They flex the metacarpophalangeal joints and extend the interphalangeal joints. The first and second lumbricals are supplied by the median nerve, and the third and fourth lumbricals are supplied by the ulnar nerve.

The palmar and dorsal interossei arise from the metacarpals. The palmar interossei insert into the proximal phalanx and the expansion of the extensor digitorum communis. The palmar interossei are adductor muscles. Dorsal interossei are abductors and insert into the proximal phalanges and the dorsal digital hood. The interosseous muscles are all supplied by the deep branch of the ulnar nerve.

As the tendons of the long flexor and extensor muscles reach the hand, the flexor tendons must first pass deep to the flexor retinaculum and the extensor tendons must pass under the extensor retinaculum. Flexor tendons on the palmar side are anchored to the phalanges by fibrous flexor sheaths to prevent "bow-stringing." Synovial sheaths prevent friction from occurring between fibrous flexor sheaths and the tendons. Synovial sheaths are present on the dorsum of the hand deep to the extensor retinaculum. They extend from a point proximal to the retinaculum to a point in the proximal one third of the dorsum of the hand.

Anatomy of the distal interphalangeal (DIP) joint includes the insertion of the extensor tendon on the distal phalanx.


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