The flexor digiti minimi brevis is the central hypothenar muscle, flexing the little finger at the MCP joint and assisting in opposition. It shares its origin from the hook of the hamate with the ADM and opponens digiti minimi. Hook of hamate fractures, common in golfers and tennis players from club or racket handle impact, can cause direct pressure on the FDMB and ulnar nerve branches passing through the hypothenar region.
| Origin | Hook of the hamate and flexor retinaculum |
|---|---|
| Insertion | Ulnar side of the base of the proximal phalanx of the little finger |
| Nerve Supply | Deep branch of the ulnar nerve (C8, T1) |
| Blood Supply | Ulnar artery |
| Actions | Flexion of the little finger MCP joint; Assists in opposition of the little finger |
|---|
Flexing the little finger MCP joint while the interossei flex the IP joints, it contributes to the finger flexion cascade needed for gripping, and enables the little finger opposition that improves the cup of the hand for holding round objects.
FDMB weakness contributes to the claw deformity of ulnar nerve palsy at the little and ring fingers, where the MCP joints hyperextend because of intrinsic weakness while the FDP keeps the IP joints flexed. Hook of hamate fractures affecting the FDMB origin can cause ulnar-sided hand pain and hypothenar tenderness that reproduces with gripping.
The FDMB is the central component of the hypothenar eminence, palpable between the ADM and opponens digiti minimi during resisted little finger MCP flexion.
Stress or direct impact fracture at the FDMB and ADM origin producing ulnar-sided hand pain with grip and hypothenar tenderness, confirmed by CT and managed with cast immobilisation or surgical excision of the hook fragment.
