Abductor Digiti Minimi (Hand)
| Abductor Digiti Minimi (Hand) | |
|---|---|
| Muscle Type | |
| Origin | Pisiform bone and tendon of the flexor carpi ulnaris muscle |
| Insertion | Base of the proximal phalanx of the fifth digit (ulnar side) and dorsal expansion of the extensor digiti minimi |
| Action | Finger Abduction, also assists with extension of the wrist |
| Synergists | Interossei (Hand) |
| Antagonists | |
| Spinal innervation | C8, T1 |
| Peripheral Innervation | Ulnar Nerve |
| Vasculature | |
Palpation
Along ulnar border of the 5th metacarpal
Manual Muscle Testing
The abductor digiti minimi is the primary muscle responsible for moving the little finger away from the ring finger. Manual testing of the ADM involves having the patient abduct the fifth finger against resistance. Typically, the hand is pronated flat on a table or supinated with the fingers extended, and the examiner applies pressure on the lateral side of the little finger, trying to push it toward the ring finger. A strong ADM contraction can usually be both seen and palpated along the ulnar border of the hand (hypothenar eminence).This test is highly useful for assessing ulnar nerve function
In ulnar neuropathy, patients may exhibit Wartenberg’s sign, an involuntary abduction of the little finger. This occurs because the paralyzed palmar interosseus (which normally adducts the little finger) can no longer counteract the slight abducting pull of extensor tendons. When the ADM itself is weak or denervated, the patient cannot generate strong fifth-finger abduction. Conversely, in a healthy hand, resisting little-finger abduction yields a firm end-point due to ADM activation.
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