Three days after a displaced Colles' fracture treated in a below-elbow cast, a patient develops increasing pain out of proportion, paraesthesiae in the thumb, index and middle fingers, and weakness of abduction of the thumb. Passive extension of the fingers is painless. The most likely diagnosis is:

• A Reflex sympathetic dystrophy of the hand
• B Volkmann's ischaemic contracture of the flexor compartment
• C Injury of the anterior interosseous nerve at the time of fracture
• D Acute carpal tunnel syndrome from compression of the median nerve within the wrist ✓

Explanation

Haemorrhage and oedema within the carpal canal after a displaced distal radius fracture can produce acute median nerve compression. Paraesthesiae in the median distribution, weak abductor pollicis brevis and disproportionate early pain point to this, and it demands urgent release by splitting the cast and decompressing the carpal tunnel. In Volkmann's contracture, passive extension of the fingers is exquisitely painful, which is absent here. Anterior interosseous palsy spares sensation, and reflex sympathetic dystrophy evolves later.

Reference: Maheshwari's Textbook of Orthopedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.