A patient with a supracondylar fracture of the humerus in childhood develops a delayed onset 'claw hand' affecting all four fingers, with wasting of all intrinsic hand muscles. What is the most likely explanation?

• A Acute anterior interosseous nerve injury at the time of fracture
• B Delayed ulnar nerve injury due to cubitus valgus (tardy ulnar nerve palsy) ✓
• C Combined median and radial nerve injury
• D Klumpke's palsy from traction on lower trunk of brachial plexus

Explanation

Supracondylar fracture of the humerus in children can lead to gradual cubitus valgus deformity (lateral angulation), which progressively stretches the ulnar nerve at the elbow. This 'tardy ulnar nerve palsy' presents years after the fracture with ulnar nerve compression signs — wasting of hypothenar and interossei muscles, clawing of ring and little fingers (4th-5th lumbrical weakness), and sensory loss over ulnar 1.5 fingers. It is a classic delayed complication and distinct from acute nerve injury at time of fracture.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.