The FDMB forms the central hypothenar muscle, flexing the little finger MCP joint. With the ADM and opponens digiti minimi it completes the hypothenar eminence. The hook of the hamate, its origin, is fractured in racket sport and golf injuries, and hamate fractures can compress adjacent hypothenar muscles.
| Origin | Hook of the hamate and flexor retinaculum |
|---|---|
| Insertion | Ulnar side of the proximal phalanx base of the little finger |
| Nerve Supply | Deep branch of the ulnar nerve (C8, T1) |
| Blood Supply | Ulnar artery |
| Actions | MCP joint flexion of the little finger; Assists in little finger opposition |
|---|
The FDMB positions the little finger for grip by flexing the MCP joint, complementing the ADM's abduction component to cup the medial palm.
Hamate hook fracture (from repetitive grip impact in racket sports and golf) can damage the FDMB origin and compress the deep motor branch of the ulnar nerve as it passes around the hamate, producing hypothenar weakness.
The FDMB is palpable as the central hypothenar bulk alongside the ADM.
Racket sport impact fracture of the hamate hook near the FDMB origin producing hypothenar pain and potential ulnar nerve motor branch compression.
