Fig. 90.—Drop-wrist following Fracture of Shaft of Humerus.
If the lesion is high up, as it is, for example, in crutch paralysis, the triceps and anconeus may also suffer.
Treatment.—The slighter forms of injury by compression recover under massage, douching, and electricity. If there is drop-wrist, the hand and forearm are placed on a palmar splint, with the hand dorsiflexed to nearly a right angle, and this position is maintained until voluntary dorsiflexion at the wrist returns to the normal. Recovery is sometimes delayed for several months.
In the more severe injuries associated with fracture of the humerus and attended with the reaction of degeneration, it is necessary to cut down upon the nerve and free it from the pressure of a fragment of bone or from callus or adhesions. If the nerve is torn across, the ends must be sutured, and if this is impossible owing to loss of tissue, the gap may be bridged by a graft taken from the superficial branch of the radial nerve, or the ends may be implanted into the median.
Finally, in cases in which the paralysis is permanent and incurable, the disability may be relieved by operation. A fascial graft can be employed to act as a ligament permanently extending the wrist; it is attached to the third and fourth metacarpal bones distally and to the radius or ulna proximally. The flexor carpi radialis can then be joined up with the extensor digitorum communis by passing its tendon through an aperture in the interosseous membrane, or better still, through the pronator quadratus, as there is less likelihood of the formation of adhesions when the tendon passes through muscle than through interosseous membrane. The palmaris longus is anastomosed with the abductor pollicis longus (extensor ossis metacarpi pollicis), thus securing a fair amount of abduction of the thumb. The flexor carpi ulnaris may also be anastomosed with the common extensor of the fingers. The extensors of the wrist may be shortened, so as to place the hand in the position of dorsal flexion, and thus improve the attitude and grasp of the hand.
The superficial branch of the radial (radial nerve) and the deep branch (posterior interosseous), apart from suffering in lesions of the radial, are liable to be contused or torn is dislocation of the head of the radius, and in fracture of the neck of the bone. The deep branch may be divided as it passes through the supinator in operations on old fractures and dislocations in the region of the elbow. Division of the superficial branch in the upper two-thirds of the forearm produces no loss of sensibility; division in the lower third after the nerve has become associated with branches from the musculo-cutaneous is followed by a loss of sensibility on the radial side of the hand and thumb. Wounds on the dorsal surface of the wrist and forearm are often followed by loss of sensibility over a larger area, because the musculo-cutaneous nerve is divided as well, and some of the fibres of the lower lateral cutaneous branch of the radial.
