Posterior interosseous nerve of forearm

The posterior interosseous nerve of forearm (Posterior antebrachial interosseous nerve) is a continuation of the deep branch of the radial nerve after it penetrates the supinator muscle and innervates the muscles in the posterior compartment of the forearm.

The the deep branch of the radial nerve originates at the level of the lateral epicondyle of the humerus, where the radial nerve bifurcates into the superficial branch and the the deep branch of the radial nerve.

After penetrating in the suppinator muscle, the deep branch of the radial nerve becomes posterior interosseous nerve of forearm and travels through the supinator muscle, specifically through the arcade of Frohse, which is a fibrous arch in the supinator muscle. It exits the supinator approximately 6 cm distal to the lateral epicondyle. The nerve then courses along the posterior aspect of the interosseous membrane, supplying the extensor muscles of the forearm.

The terminal branches of the posterior interosseous nerve of forearm are organized into six main branches that innervate the extensor digitorum communis, extensor carpi ulnaris, extensor digiti minimi, extensor pollicis longus, extensor indicis proprius, extensor pollicis brevis, and abductor pollicis longus.