The radial nerve (C5 to C8, T1) is the largest branch of the brachial plexus and is the main continuation of its posterior cord. In the axilla, it lies behind the outer end of the axillary artery on the subscapularis, latissimus dorsi, and teres major muscles. Leaving the axilla, it enters the arm between the brachial artery and the long head of the triceps brachii muscle.
Continuing downward and accompanied by the deep brachial artery, the nerve pursues a spiral course behind the humerus, lying close to the bone in the shallow radial nerve sulcus. It passes between the long and medial and medial and lateral heads of the triceps brachii muscle and then lies deep to the lateral head. On reaching the distal third of the arm at the lateral margin of the humerus, it pierces the lateral intermuscular septum to enter the anterior compartment of the arm. Then it descends anterior to the lateral epicondyle of the humerus and the articular capsule of the elbow joint, lying deep in the furrow between the brachialis muscle medially and the brachioradialis and extensor carpi radialis longus muscles laterally. At this point, it divides into its deep and superficial branches.
In the axilla, the radial nerve gives off the small pos- terior brachial cutaneous nerve and a muscular branch to the long head of the triceps brachii muscle.
In the arm, the radial nerve supplies muscular, cutaneous, vascular, articular, and osseous branches. The first muscular branch is long and slender, arising as the nerve enters the radial nerve sulcus; it accompanies the ulnar nerve to the lower arm to supply the distal part of the medial head of the triceps brachii muscle and to furnish twigs to the elbow joint. A second, larger branch arises from the nerve as it lies in the radial nerve sulcus; it soon subdivides into smaller branches that enter the medial head of the triceps brachii muscle, with some twigs to the humeral periosteum and bone. A stouter subdivision supplies the lateral head of the triceps brachii muscle. It descends through the muscle accompanied by the medial branch of the deep brachial artery.
It then penetrates and supplies the anconeus muscle and sends branches to the humerus and the elbow joint.
Anterior to the lateral intermuscular septum, the radial nerve gives muscular branches to the lateral part of the brachialis, brachioradialis, and extensor carpi radialis longus muscles and, occasionally, to the extensor carpi radialis brevis. Vascular branches and twigs are furnished to the elbow joint.
Three cutaneous branches arise from the radial nerve above the elbow the posterior brachial cutaneous, inferior lateral brachial cutaneous, and posterior antebrachial cutaneous nerves.
Nerve Supply To The Elbow
Nerves reach the joint anteriorly from the musculocutaneous, median, and radial nerves and posteriorly from the ulnar nerve and the radial nerve branch to the anconeus muscle.