A cricketer sustains a direct blow to the lateral aspect of the elbow. He develops weakness of wrist and finger extension and forearm supination with preserved triceps power and intact sensation over the dorsum of the hand. Which nerve and at which level?

• A Radial nerve at the spiral groove of humerus
• B Posterior interosseous nerve (deep branch of radial nerve) at the radial tunnel ✓
• C Radial nerve at the lateral epicondyle
• D Superficial branch of radial nerve

Explanation

The posterior interosseous nerve (PIN) is the deep motor branch of the radial nerve, arising after the radial nerve divides at the lateral elbow. It passes through the radial tunnel (between the two heads of supinator — the arcade of Frohse being the proximal edge). Damage here produces weakness of wrist/finger extension and supination (by extensor carpi radialis longus and brevis are spared as they arise proximal to the division, so there is radial deviation of wrist), but triceps and brachioradialis are spared. Sensation over the dorsum of the hand is carried by the superficial radial nerve which is also spared.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.