Ulnar Nerve Palsy

Definition & Cause

Ulnar nerve palsy produces the ‘claw hand’. The ulnar nerve is most often injured at the elbow (behind the medial epicondyle — the ‘funny bone’, in cubital tunnel syndrome or after elbow fractures) and at the wrist (Guyon’s canal, lacerations).

Clinical Features

The ulnar nerve supplies most of the small intrinsic muscles of the hand. Paralysis causes the ulnar claw hand — hyperextension at the MCP joints and flexion at the IP joints of the ring and little fingers — with wasting of the interossei (guttering) and hypothenar eminence, a positive Froment’s sign (thumb IP flexion when pinching paper, using FPL to compensate for weak adductor pollicis), and sensory loss over the little and ulnar half of the ring finger.

Management

Treatment depends on the cause and severity. Compression at the elbow may respond to activity modification, splinting and nerve decompression ± transposition. A divided nerve is repaired or grafted. Late/irrecoverable palsies are managed with tendon transfers to correct the claw and restore pinch, plus hand therapy.

Complications & Assessment

Longstanding ulnar palsy leads to fixed clawing, wasting and a weak, clumsy pinch that is disabling for fine tasks. Examination documents the intrinsic wasting (dorsal interosseous guttering), tests the interossei (finger abduction/adduction) and adductor pollicis (Froment’s sign), and maps the sensory loss over the little and ulnar-ring fingers, while nerve conduction studies localise the lesion to the elbow or wrist and guide whether decompression or transfer is appropriate.

Ulnar paradox — higher lesions produce less clawing.

• Ulnar nerve palsy = claw hand; injured at the elbow (cubital tunnel) or wrist (Guyon’s canal).
• Interossei/hypothenar wasting, clawing of ring & little fingers, positive Froment’s sign.
• Ulnar paradox: higher lesion → less claw; lower lesion → more claw.
• Decompression/transposition or repair; tendon transfers for irrecoverable claw.