Dr. Ebraheim’s educational animated video describes the anatomy of the Interosseous muscles in the hand.
The interosseous muscles of the hand arise from the metacarpal bones in the hand and help to control the fingers. The interosseous muscles are inserted into the bases of the proximal phalanges. Metacarpal shafts give attachments to four dorsal and three palmar interossei muscles. The four dorsal interossei muscles are also inserted into the extensor expansion of the corresponding extensor digitorum tendon. The function of the four dorsal interossei muscles is to abduct the fingers. No dorsal interossei are inserted into the thumb or the little finger. There are three palmar interossei muscles.
The function of the three palmar interossei muscles is to adduct the fingers. The three palmar interossei muscles also assist the lumbricals in flexing the MP joints and extending the IP joints. No palmar interossei are inserted into the middle finger. Abduction of the fingers come from the dorsal (DAB) interossei. Adduction of the fingers come form the palmar interossei (PAD). The interosseous muscles help in the writing position of the hand by flexing the MCP joint and extending the PIP joint. The interosseous and lumbrical muscles function is to flex the MCP joint but they extend the PIP joint through the lateral bands and the central slip of the extensor digitorum communis.
All seven interosseous muscle of the hand are supplied by the deep branch of the ulnar nerve. Test abduction of the index finger against resistance. The function of the first dorsal interossei is tested by asking the patient to abduct the index finger against resistance. The first dorsal interosseous muscle can be seen and evaluated on the dorsum of the hand. Severe atrophy of the first dorsal interosseus muscle could indicate a bad prognosis for recovery of the ulnar nerve. The condition would be associated with a claw hand deformity.
Test adduction of the index finger against resistance (palmar interossei). The examiner has the patient adduct the index finger against resistance. Check for clawing of the 4th and 5th fingers. Clawing of the ulnar digits occurs in low ulnar nerve palsy. There will be hyperextension of the MP joint because of the unopposed pull of the long extensors and the IP joints are flexed due to unopposed actions of the long flexors. The intrinsic muscles are weak and cannot extend the PIP joint.
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Background music provided as a free download from YouTube Audio Library.
Song Title: Every Step
