At which anatomical site is the posterior interosseous nerve most commonly entrapped?

• A Cubital tunnel beneath the arcuate ligament
• B Fibrous proximal edge of the supinator muscle (arcade of Frohse) ✓
• C Between the two heads of flexor carpi ulnaris
• D Radial groove of the humerus

Explanation

After winding around the lateral neck of the radius, the posterior interosseous nerve enters supinator through the arcade of Frohse, a fibrous arch on the superficial head of supinator, and this is the commonest entrapment site. The radial groove, the tempting distractor, is a site of radial nerve injury in humeral shaft fractures, but that involves the main trunk before the PIN is given off.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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