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Claw hand
Related Anatomy
Muscles
Abductor pollicis brevis
Dorsal interossei (hand)
Palmaris brevis
Flexor carpi ulnaris
Nerve Root
C8
T1
Brachial Plexus Cord
Medial cord
Claw Hand vs Ulnar Claw vs Benediction Sign
Hand deformities are best distinguished by the imbalance between intrinsic hand muscles (lumbricals/interossei) and extrinsic flexors/extensors.
- A true “claw hand” is classically due to a lower trunk (C8–T1) or medial cord lesion, affecting both median and ulnar contributions to intrinsic hand muscles, resulting in clawing of all digits at rest with MCP hyperextension and PIP/DIP flexion due to unopposed extensor digitorum and flexor digitorum profundus/superficialis.
- In contrast, an ulnar claw (ulnar neuropathy, e.g., cubital tunnel or Guyon canal) produces clawing of the 4th and 5th digits at rest, as loss of ulnar-innervated lumbricals and interossei leaves the medial digits most affected; the 2nd and 3rd digits are relatively spared due to intact median nerve lumbricals.
- The “hand of benediction” is seen in proximal median nerve injury and is elicited when the patient attempts to make a fist—there is failure to flex digits 1, 2, and 3 (due to loss of FDS, lateral FDP, and lumbricals), while digits 4 and 5 can still flex via ulnar innervation.
- High-yield distinction: ulnar claw = deformity at rest (digits 4–5), whereas benediction sign = deficit with attempted flexion (digits 1–3).