The second dorsal interosseous abducts the middle finger toward the index finger. The four dorsal interossei abduct the index (first DI), middle (second DI radially, third DI ulnarly), and ring fingers (fourth DI) from the midline axis of the hand (middle finger).
| Origin | Adjacent sides of the second and third metacarpal shafts |
|---|---|
| Insertion | Radial side of the middle finger proximal phalanx and extensor expansion |
| Nerve Supply | Deep branch of ulnar nerve (C8, T1) |
| Blood Supply | Second dorsal metacarpal artery |
| Actions | Abducts the middle finger radially — away from the ring finger; Assists middle finger MCP flexion with IP extension |
|---|
Second DI wasting alongside first DI indicates ulnar nerve palsy. Individual dorsal interosseous testing assesses the deep ulnar nerve branch integrity. In Dupuytren's disease, the natatory cord can compress the second DI.
Tested by resisted middle finger abduction toward the index finger.
Second dorsal interosseous wasting alongside first DI in ulnar nerve palsy, assessed by resisted middle finger radial abduction.
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