A patient with a Monteggia fracture-dislocation develops inability to extend the fingers at the metacarpophalangeal joints, yet wrist extension is retained and there is no area of sensory loss on the dorsum of the hand. Which muscle accounts for the preserved wrist extension?

• A Extensor carpi ulnaris
• B Extensor carpi radialis longus ✓
• C Extensor digitorum
• D Anconeus

Explanation

In a posterior interosseous nerve palsy, the nerve is damaged after the radial nerve divides in front of the lateral epicondyle. Extensor carpi radialis longus and part of brevis are supplied by the radial nerve proper before this division, so wrist extension is preserved, though weakened with radial deviation. The posterior interosseous nerve is purely motor and has no cutaneous branch, explaining the absent sensory loss and eliminating any option implying a sensory deficit.

Reference: Snell's Clinical Anatomy by Regions, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.