ABSTRACT
The radial nerve supplies the triceps brachii and anconeus muscles in the upper arm. In the spiral groove, the posterior antebrachial cutaneous nerve branches off. As the nerve pierces the septum to lie anteriorly, it lies in a sulcus or “canalis” limited by the brachioradialis muscle (laterally) and the brachialis muscle (medially). In this sulcus, the radial nerve branches into its terminal components: the posterior interosseous nerve and the superficial radial nerve. While the superficial radial nerve is predominantly a sensory branch, the posterior interosseus nerve supplies the majority of the extensor muscles in the forearm.
