Manual of Surgery - Alexis Thomson (read me a book txt) 📗
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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.
Fig. 91.—To illustrate the Loss of Sensation produced by Division of the Median Nerve. The area of complete cutaneous insensibility is shaded black. The parts insensitive to light touch and to intermediate degrees of temperature are enclosed within the dotted line. (After Head and Sherren.)
The Median Nerve is most frequently injured in wounds made by broken glass in the region of the wrist. It may also be injured in fractures of the lower end of the humerus, in fractures of both bones of the forearm, and as a result of pressure by splints. After division at the elbow, there is impairment of mobility which affects the thumb, and to a less extent the index finger: the terminal phalanx of the thumb cannot be flexed owing to the paralysis of the flexor pollicis longus, and the index can only be flexed at its metacarpo-phalangeal joint by the interosseous muscles attached to it. Pronation of the forearm is feeble, and is completed by the weight of the hand. After division at the wrist, the abductor-opponens group of muscles and the two lateral lumbricals only are affected; the abduction of the thumb can be feebly imitated by the short extensor and the long abductor (ext. ossis metacarpi pollicis), while opposition may be simulated by contraction of the long flexor and the short abductor of the thumb; the paralysis of the two medial lumbricals produces no symptoms that can be recognised. It is important to remember that when the median nerve is divided at the wrist, deep touch can be appreciated over the whole of the area supplied by the nerve; the injury, therefore, is liable to be over looked. If, however, the tendons are divided as well as the nerve, there is insensibility to deep touch. The areas of epicritic and of protopathic insensibility are illustrated in Fig. 91. The division of the nerve at the elbow, or even at the axilla, does not increase the extent of the loss of epicritic or protopathic sensibility, but usually affects deep sensibility.
Fig. 92.—To illustrate Loss of Sensation produced by complete Division of Ulnar Nerve. Loss of all forms of cutaneous sensibility is represented by the shaded area. The parts insensitive to light touch and to intermediate degrees of heat and cold are enclosed within the dotted line. (Head and Sherren.)
The Ulnar Nerve.—The most common injury of this nerve is its division in transverse accidental wounds just above the wrist. In the arm it may be contused, along with the radial, in crutch paralysis; in the region of the elbow it may be injured in fractures or dislocations, or it may be accidentally divided in the operation for excising the elbow-joint.
When it is injured at or above the elbow, there is paralysis of the flexor carpi ulnaris, the ulnar half of the flexor digitorum profundus, all the interossei, the two medial lumbricals, and the adductors of the thumb. The hand assumes a characteristic attitude: the index and middle fingers are extended at the metacarpo-phalangeal joints owing to paralysis of the interosseous muscles attached to them; the little and ring fingers are hyper-extended at these joints in consequence of the paralysis of the lumbricals; all the fingers are flexed at the inter-phalangeal joints, the flexion being most marked in the little and ring fingers—claw-hand or main en griffe. On flexing the wrist, the hand is tilted to the radial side, but the paralysis of the flexor carpi ulnaris is often compensated for by the action of the palmaris longus. The little and ring fingers can be flexed to a slight degree by the slips of the flexor sublimis attached to them and supplied by the median nerve; flexion of the terminal phalanx of the little finger is almost impossible. Adduction and abduction movements of the fingers are lost. Adduction of the thumb is carried out, not by the paralysed adductor pollicis, but the movement may be simulated by the long flexor and extensor muscles of the thumb. Epicritic sensibility is lost over the little finger, the ulnar half of the ring finger, and that part of the palm and dorsum of the hand to the ulnar side of a line drawn longitudinally through the ring finger and continued upwards. Protopathic sensibility is lost over an area which varies in different cases. Deep sensibility is usually lost over an area almost as extensive as that of protopathic insensibility.
When the nerve is divided at the wrist, the adjacent tendons are also frequently severed. If divided below the point at which its dorsal branch is given off, the sensory paralysis is much less marked, and the injury is therefore liable to be overlooked until the wasting of muscles and typical main en griffe ensue. The loss of sensibility after division of the nerve before the dorsal branch is given off resembles that after division at the elbow, except that in uncomplicated cases deep sensibility is usually retained. If the tendons are divided as well, however, deep touch is also lost.
Care must be taken in all these injuries to prevent deformity; a splint must be worn, at least during the night, until the muscles regain their power of voluntary movement, and then exercises should be instituted.
Dislocation of the ulnar nerve at the elbow results from sudden and violent flexion of the joint, the muscular effort causing stretching or laceration of the fascia that holds the nerve in its groove; it is predisposed to if the groove is shallow as a result of imperfect development of the medial condyle of the humerus, and by cubitus valgus.
The nerve slips forward, and may be felt lying on the medial aspect of the condyle. It may retain this position, or it may slip backwards and forwards with the movements of the arm. The symptoms at the time of the displacement are some disability at the elbow, and pain and tingling along the nerve, which are exaggerated by movement and by pressure. The symptoms may subside altogether, or a neuritis may develop, with severe pain shooting up the nerve.
The dislocated nerve is easily replaced, but is difficult to retain in position. In recent cases the arm may be placed in the extended position with a pad over the condyle, care being taken to avoid pressure on the nerve. Failing relief, it is better to make a bed for the nerve by dividing the deep fascia behind the medial condyle and to stitch the edges of the fascia over the nerve. This operation has been successful in all the recorded cases.
The Sciatic Nerve.—When this nerve is compressed, as by sitting on a fence, there is tingling and powerlessness in the limb as a whole, known as “sleeping” of the limb, but these phenomena are evanescent. Injuries to the great sciatic nerve are rare except in war. Partial division is more common than complete, and it is noteworthy that the fibres destined for the peroneal nerve are more often and more severely injured than those for the tibial (internal popliteal). After complete division, all the muscles of the leg are paralysed; if the section is in the upper part of the thigh, the hamstrings are also paralysed. The limb is at first quite powerless, but the patient usually recovers sufficiently to be able to walk with a little support, and although the hamstrings are paralysed the knee can be flexed by the sartorius and gracilis. The chief feature is drop-foot. There is also loss of sensation below the knee except along the course of the long saphenous nerve on the medial side of the leg and foot. Sensibility to deep touch is only lost over a comparatively small area on the dorsum of the foot.
The Common Peroneal (external popliteal) nerve is exposed to injury where it winds round the neck of the fibula, because it is superficial and lies against the unyielding bone. It may be compressed by a tourniquet, or it may be bruised or torn in fractures of the upper end of the bone. It has been divided in accidental wounds,—by a scythe, for example,—in incising for cellulitis, and in performing subcutaneous tenotomy of the biceps tendon. Cases have been observed of paralysis of the nerve as a result of prolonged acute flexion of the knee in certain occupations.
When the nerve is divided, the most obvious result is “drop-foot”; the patient is unable to dorsiflex the foot and cannot lift his toes off the ground, so that in walking he is obliged to jerk the foot forwards and laterally. The loss of sensibility depends upon whether the nerve is divided above or below the origin of the large cutaneous branch which comes off just before it passes round the neck of the fibula. In course of time the foot becomes inverted and the toes are pointed—pes equino-varus—and trophic
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