Radial Nerve

Radial nerve damage produces wrist drop (Figure 223.1).Extension of the fingers is impaired. Elbow flexion with the forearm in midposition, between supination and pronation, will be affected by lesions above the elbow. Lesions below the elbow do not affect elbow flexion because the branch for the brachioradialis muscle leaves the radial nerve above the elbow. Finger flexion is normal when the wrist is placed in a neutral position.
Radial nerve lesions do not involve the deltoid and biceps muscles, nor do they involve muscles innervated by the same spinal segment as the radial nerve (C6-C8) but through a different peripheral nerve. Median and ulnar nerve lesions do not produce wrist drop.

Figure 223.1.— Left wrist drop and finger extension weakness in a patient with a radial nerve injury. Weakness was noted after an intravenous board was removed. It resolved with physical therapy.