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Flexor Pollicis Brevis
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| Flexor Pollicis Brevis | |
|---|---|
| Muscle Type | |
| Origin | Distal ridge of the trapezium, the trapezoid, capitate, and flexor retinaculum |
| Insertion | Base of the proximal phalanx of the thumb on the radial side |
| Action | MCP flexion |
| Synergists | |
| Antagonists | |
| Spinal innervation | C8, T1 |
| Peripheral Innervation | Median Nerve, Ulnar Nerve |
| Vasculature | |
Palpation
The ulnar side of the first metacarpal
Manual Muscle Testing
Manual strength testing of the flexor pollicis brevis (FPB) clasically targets thumb MCP joint flexion while keeping the IP joint extended to minimize flexor pollicis longus (FPL) contribution. Further research found that flexing the IP joint yields a more isolated FPB contraction.[1]
The FPB is often dual-innervated (median and ulnar nerves). Therefore thumb MCP flexion strength may appear intact unless both nerves are compromised.
| FPB Portion | Peripheral Nerve | Nerve Root | |
|---|---|---|---|
| Deep head | Ulnar Nerve | C8 dominant, T1 minor | |
| Superficial Head | Median Nerve (recurrent branch) | C8 minor, T1 dominant |
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References
