Nerve · Forearm

Deep branch of radial nerve

Ramus profundus nervi radialis

At the elbow the radial nerve divides in two, and this is the muscular half — the other, the superficial branch, is pure skin. The deep branch curves backwards round the lateral side of the radius, passing between the two heads of supinator and winding round the neck of that bone within the muscle before appearing on the back of the forearm as the posterior interosseous nerve. Its short course is entirely spent supplying supinator, and usually extensor carpi radialis brevis on the way in. Because it hugs the radial neck through a fibrous tunnel, it is described together with that part of the bone and with the muscle that wraps it. Its root value is given differently in different standard descriptions, so no segmental level is recorded here.