The posterior interosseous nerve (deep branch of the radial nerve) can be compressed at the arcade of Frohse. Which movement is specifically lost while wrist extension is preserved?

• A Supination of the forearm
• B Extension of the MCP joints of fingers and thumb abduction ✓
• C Extension at the wrist (wrist drop)
• D Flexion of the DIP joints

Explanation

The posterior interosseous nerve (deep branch of radial nerve) is a pure motor branch that supplies all the muscles of the posterior compartment of the forearm except extensor carpi radialis longus (ECRL), which is supplied more proximally by the radial nerve itself. Thus, at the arcade of Frohse compression, wrist extension is preserved (via ECRL/ECRB), but MCP joint extension of fingers (extensor digitorum) and thumb abduction/extension (APL, EPL, EPB) are lost. The superficial branch (sensory) is unaffected.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.