The treatment is to seek for the divided ends of the nerve, and to unite them if possible. Should the interspace be too great to allow direct suture, an attempt might be made to restore continuity by cutting a long flap from the proximal extremity of the nerve and bringing it down to the distal end; or by the transplantation of a portion of nerve from an amputated limb, or from one of the lower animals. Where the wound lies immediately above the wrist, it is well to remember that the ulnar nerve and vessels are covered by a fibrous band, which passes from the radial side of the flexor carpi ulnaris tendon in this situation to blend with the anterior annular ligament. It should also be recollected that the deep branch of the nerve, which is occasionally implicated in penetrating wounds over the hypothenar eminence, runs around the ulnar side of the tip of the unciform process, and may there be exposed without much difficulty.[7] After operation the hand should be placed in a position of adduction and flexion, and the wound dressed antiseptically. Should this measure fail, the apparatus devised by Duchenne may be applied to replace the action of the paralysed muscles.
Musculo-spiral paralysis may be induced by ordinary wounds or contusions, by fractures of the humerus, or by long-continued compression of the nerve against the bone, either by the handle of a crutch, or while the patient is sleeping with his head resting upon an arm which is supported by the back of a chair. The consequences are paralysis of the elbow extensors, the supinator longus, the supinator brevis, and the whole of the extensors of the wrist, thumb, and fingers; and loss of sensation over the cutaneous areas supplied by the nerve in the arm, forearm, and hand. For the patient the most striking symptoms are the flexion of the wrist and fingers, the loss of power to abduct the thumb, and especially the enfeeblement of grasp due to the inability to fix the wrist during the action of the finger flexors. If the wrist be held firmly by the other hand, or by another person, in the position of extension, the power of grip becomes restored. A similar condition is present in lead poisoning; but here the loss of power is confined to the extensor muscles, and the supinator longus remains unaffected. The possibility of a crutch paralysis should lead the surgeon to warn every patient who is compelled to use the implement, in order that the paralysis may be prevented, or, should it occur, that it may be perceived and arrested in its earliest stages. When the condition has become established, an attempt should be made to restore function by massage and electricity, and if these fail, the nerve should be exposed at the seat of injury, and its continuity restored by the excision of the atrophic portion and union of the two free extremities.
In paralysis of the Median nerve by a wound above the wrist, the most distressing symptoms are referable to the trophic lesions in the integuments of the thumb, index, middle, and ring fingers (radial side) on their palmar surface and the distal half of their dorsal aspect. There is, in addition, a partial loss of power of flexion and abduction of the thumb, with wasting of the thenar eminence and some interference with the delicacy of the movements of the index and middle fingers, owing to the paralysis of the first and second lumbricales. If the nerve be divided above the elbow, the pronators and all the flexors of the wrist, thumb, and fingers, except those supplied by the ulnar nerve (flexor carpi ulnaris, and ulnar half of the flexor digitorum profundus), are paralysed, and consequently the hand is, for all practical purposes, quite useless. The rules for treatment are similar in principle to those laid down for injuries of the musculo-spiral and ulnar nerves.
Spastic Paralyses, in connection with central disease, need not be discussed; but the surgeon is sometimes consulted for conditions of persistent spasm which apparently depend upon excessive use of certain muscles. Erichsen refers to, and figures, a case of flexion with pronation attributed to cutting with heavy shears. He notes that when the wrist was extended the fingers became flexed, and when the wrist was extended the fingers became bent in. It is not stated whether the permanency of the contraction was tested by the use of an anæsthetic, but the patient, as well as another in whom the extensors were affected in like manner, became cured by means of friction and galvanism, with the use of a straight splint. A case of spastic contraction of the right little finger of thirty-five years’ duration was recently in the Mile End Infirmary. The flexion of the finger is associated with slight adduction of the hand, but the parts can be straightened completely by passive force. The condition is attributed to a wound near the elbow. There is no lesion of sensation.
The group of affections known as Writer’s cramp usually fall within the province of the physician, and will only be briefly referred to. They are of uncertain pathology, vary considerably in their manifestations, and, although most common in persons much engaged in writing, are by no means confined to these. The symptoms may assume three different types—spastic, paralytic, and tremulous—affecting the muscles of the hands and forearm, and these may be combined in various ways. The prognosis is unfavourable; but the treatment found most hopeful is to relieve the affected muscles from the strain to which they have been accustomed, and strengthen them by massage and galvanism. Interference by surgical operation has been unsuccessful, except in one case, in which Stromeyer divided the flexor longus pollicis tendon.
CONGENITAL AND INFANTILE CONTRACTIONS.
These are usually of paralytic origin, but include a proportion of cases of true hammer finger. The common form is that already described by Mr. William Adams (Medical Society, December 1890), in which the inter-phalangeal joints of one or more fingers (most frequently the fifth) are flexed, and the integument on the palmar aspect forms a longitudinal fold, which becomes tense when an attempt is made to straighten the digit; the metacarpo-phalangeal joint is super-extended. At first the finger may be fully extended by passive force, but after a few years the position of flexion at the first inter-phalangeal joint is rendered permanent by imperfect development of the ligamentous fascial and even cutaneous structures in front of the articulation, while the terminal phalanx usually remains more or less helpless. The condition is probably dependent upon an infantile paralysis of the flexors of the affected digit. The use of friction, passive movement, and electricity, may be of value in the early stages.
TRIGGER FINGER.
The description of this curious affection has been left until the last because its true nature is still an unsolved problem, and it is hence difficult to place it in any of the groups already described. It is indeed rather a pathological curiosity than an important item in surgical disease, and many surgeons of long experience have never met with a single example. Of the mechanism of its causation we know almost nothing, of its ultimate tendencies we know little more, and its morbid anatomy is almost entirely speculative. Nevertheless, it has a literature extending over forty years, and comprising nearly a hundred separate contributions, the last of which, a model in its way, is a monograph of 250 closely printed large octavo pages, the work of Dr. Carlier.
Trigger finger, the doigt à ressort of French authors, may be defined as a peculiar defect in the motions of the digit, consisting, first, of an impediment which obstructs the movement of flexion or of extension, or of both, followed, if the motive force be continued, by a sudden cessation of the resistance, and a brusque, spring-like action that often bears a remarkable resemblance to that which accompanies the opening and closure of the blade of a penknife. The first observation was that of Notta in 1850. A finger attacked by this affection generally lies when at rest in a position of flexion, and by a voluntary effort or by passive force may be straightened, with the peculiar result described in the definition, the resistance to extension suddenly yielding with a trigger- or spring-like action; and the same phenomenon is usually but not necessarily repeated when the digit is again bent. In exceptional cases a reverse condition obtains: the passive finger is kept in a state of extension, and it is during flexion that the trigger phenomenon is elicited. The movement may be merely inconvenient, or it may be more or less painful. The sign may be constant, accompanying every movement, or it may be intermittent, disappearing and recurring without any obvious reason. It is usually confined to a single finger, but it may be multiple. The digits most frequently involved are the middle finger, the ring finger, and the thumb, while the index and little fingers are relatively free, and the right side is more often affected than the left. It is rather more common in women than in men (in the proportion of three to two); and much more frequent in adults than in children, but may appear at all ages. The etiology is ill understood. In many cases an important influence, direct or remote, has been assigned to rheumatism; in others the condition has been attributed to injuries of various kinds; in others to occupations necessitating over-use of the digital articulations (as in sempstresses); but no cause has yet been recognised which can account for any large proportion of the examples.