Posterior interosseous nerve


The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve. The nerve fibers originate from cervical segments C7 and C8.

Structure

Course

It descends along the interosseous membrane, anterior to the extensor pollicis longus muscle, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and articulations of the carpus.

Supply

It supplies all the muscles on the radial side and dorsal surface of the forearm, except the anconaeus, brachioradialis, extensor carpi radialis longus. In other words, it supplies the following muscles:
The posterior interosseous nerve may be entrapped at the arcade of Frohse, which is part of the supinator muscle. Posterior interosseous neuropathy is purely a motor syndrome resulting in finger drop due to no extension of IP joints and radial wrist deviation on extension.