The posterior interosseous nerve (deep branch of radial nerve) enters the posterior compartment of the forearm by passing through the radial tunnel. It does NOT supply which of the following muscles?

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

Explanation

The extensor carpi radialis longus (ECRL) is supplied by the radial nerve proper (before it divides at the lateral epicondyle into superficial and deep branches), not by the posterior interosseous nerve (PIN). The radial nerve gives branches to brachioradialis, ECRL, and sometimes extensor carpi radialis brevis (ECRB) before entering the radial tunnel. The PIN (deep branch) supplies extensor carpi ulnaris, extensor digitorum, extensor digiti minimi, extensor indicis, extensor pollicis longus and brevis, abductor pollicis longus, and ECRB (variable). This is clinically relevant: PIN palsy at the arcade of Frohse causes finger and thumb extensor paralysis but spares wrist extension because ECRL 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.