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Lumbricals (Hand)
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| Lumbricals (Hand) | |
|---|---|
| Muscle Type | |
| Origin | |
| Insertion | |
| Action | |
| Synergists | |
| Antagonists | |
| Spinal innervation | C8, T1 |
| Peripheral Innervation | Median Nerve (1 & 2), Ulnar Nerve (3 & 4) |
| Vasculature | |
The lumbricals challenging to test in isolation. Their action is to flex the MCP and extend the IP joints of those fingers, but interossei muscles synergize on the same motion, making pure lumbrical testing difficult. The standard clinical attempt is to place the fingers in an “intrinsic plus” position (MCP flexed, PIP/DIP extended) and apply resistance against MCP flexion or IP extension. However, EMG and biomechanical studies show that interossei contribute the majority of force in this position, whereas lumbricals are relatively weak.
| Lumbricals Portion | Peripheral Nerve | Spinal Nerve |
|---|---|---|
| 1st & 2nd | Median Nerve | Minor C8, Dominant T1 |
| 3rd & 4th | Ulnar Nerve | Dominant C8, Minor T1 |
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