The radial nerve passes through the radial groove in the humerus of the upper limb. It is very close to the bone that it is frequently injured causing sensory and motor losses in the areas supplied by the nerve. The nerve supplies the sensory fibers to the back of the hand and motor fibers to the extensors of the wrist and the fingers. Therefore injury causes loss or impairment of sensation to the back of the hand and wrist and finger drop. Humeral fracture may cause injury to the nerve directly, or it may be injured when the fracture is being reduced, during surgery or trapped as the bone is healing (Radial Nerve Surgery, 2007).
The deformities caused by the damage include wrist drop which characterized by loss of wrist extension. The palmar flexors are unopposed by the dorsiflexors causing the wrist to remain in palmar flexion. Another deformity is wasting of forearm extensor muscles due to atrophy of the innervated muscle fibers. Sensory is also lost at the back of the forearm over a marrow strip and on the dorsum of the hand at the lateral side (Radial Nerve Injury, n.d.).
Radial nerve injury caused disability to the patient. The patient is unable to extend the wrist since the dorsiflexors are affected. Synergic action of the wrist is also affected. This causes loss of the grip power leading to weakening of its grip action. These disabilities makes the patient unable to place an object on a flat surface(Radial Nerve Injury, n.d.).
Injury of the radial nerve in the radial groove is classified as a high radial nerve palsy. All muscles supplied by the nerve except triceps brachii and the anconeous are affected. They include brachioradialis, wrist extensor, extensor digitorum and extensor pollicis longus. Very high radial palsy occurs when the injury is above the radial groove and it affects all the muscles it supplies including triceps brachii and the anconeous. In low radial palsy, the muscles in the distal arm are spared(Radial Nerve Injury, n.d.).