The dorsal interosseous muscles abduct the fingers, flex the metacarpophalangeal joints, and extend the interphalangeal joints. Observe that the middle finger (III) has two muscles, one abducting the finger toward the radial side and the other abducting it toward the ulnar side. The line of reference for abduction is midway down the middle finger.
Reproduced with permission from: The upper limb. In: Grant's Dissector, 15th ed, Tank PW (Ed), Lippincott Williams & Wilkins, Philadelphia 2012. Copyright © 2012 Lippincott Williams & Wilkins.
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