The radial nerve is close to the humerus in the middle and lower 1/3 of the humerus. It is vulnerable to injury when the humerus is fractured. Excessive callus growth and anterior dislocation of the radial head can compress the radial nerve. Inadvertent surgery can also injure this nerve. The radial nerve is composed of fibers from the C5-8 and T1 nerve roots, and is the continuation of the posterior bundle of the brachial plexus. In the upper arm, after the radial nerve leaves the axilla, it follows the deep brachial artery from the inner side of the upper arm through the long head and medial head of the triceps to the back of the upper arm, and then passes between the medial and lateral heads of the triceps and bypasses the radial nerve groove of the humerus to descend. When it reaches the upper and lateral sides of the elbow, it is divided into two branches, the superficial and deep, and then enters the forearm. The radial nerve branches successively in the upper arm, innervating the triceps, brachioradialis, and radial wrist extensor longus. In the forearm, the superficial branch is located deep to the brachioradialis and runs along with the radial artery. The superficial branch is mainly sensory nerve fibers, distributed in the radial skin of the dorsum of the hand and the back of the two and a half radial fingers, but does not include the skin on the back of the distal two segments. The deep branch, also known as the dorsal interosseous nerve, passes through the deep surface of the brachioradialis muscle to the back of the forearm, passes through the supinator muscle, and then descends between the superficial and deep muscles. The muscles innervated by the branches are: the radial extensor carpi brevis and supinator muscle above the supinator muscle; the extensor digitorum communis, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, and extensor index finger proper.