Carpo-metacarpal Dislocations.—Any or all of the metacarpal bones may be separated from the carpus by forced movements of flexion or extension. The commonest displacement is backward. The thumb seems to suffer oftener than the other digits. These injuries, however, are so rare, and the deformity is so characteristic, that a detailed description is unnecessary.
Sprain of the wrist is a common injury, and results from a fall on the hand, a twist of the wrist, or from the back-firing of a motor-crank dorsiflexing the hand. The marked swelling which rapidly ensues may render it difficult to distinguish a sprain from the other injuries that are liable to result from similar causes—Colles' fracture, separation of the lower radial epiphysis, dislocation of the wrist, and fractures and dislocations of the carpal bones.
In a sprain the normal relations of the styloid processes and other bony points about the wrist are unaltered, and there is no radial deviation of the hand, as in Colles' fracture. The most marked swelling is over the line of the articulation on the anterior and posterior aspects of the joint. There is usually some effusion into the sheaths of the tendons passing over the joint, and in some cases on moving the fingers a peculiar creaking, which may simulate crepitus, can be elicited. There is marked tenderness on making pressure over the line of the joint, as well as over one or other of the collateral ligaments, depending upon which ligament has been over-stretched or torn. Movements that tend to put the damaged ligaments on the stretch also cause pain. It has to be borne in mind, however, that in many cases of Colles' fracture there is extreme tenderness on pressing over the ulnar styloid and medial ulno-carpal ligament, as these structures are frequently injured as well as the radius, but the point of maximum pain and tenderness is over the seat of fracture of the radius. In all doubtful cases the X-rays should be employed to establish the diagnosis.
The treatment consists in the immediate employment of massage and movement, supplemented by alternate hot and cold douches, on the same lines as in sprains of other joints.
Injuries of the Fingers
Fracture.—Fractures of the metacarpals of the fingers are comparatively common. When they result from direct violence, such as a crush between two heavy objects, they are often multiple and compound. Indirect violence, acting in the long axis of the bone and increasing its natural curve, such as a blow on the knuckle in striking with the closed fist, usually produces an oblique fracture about the middle of the shaft, the proximal end of the distal fragment projecting towards the dorsum. Apart from this there is little deformity, as the adjacent metacarpals act as natural splints and tend to retain the fragments in position. A sudden sharp pain may be elicited at the seat of fracture on making pressure in the long axis of the finger; and unnatural mobility and crepitus may usually be detected. These fractures are readily recognised by the X-rays. Firm union usually results in three weeks.
The shaft of the metacarpal of the thumb is frequently broken by a blow with the closed fist. The fracture is usually transverse, and situated near the proximal end of the shaft; frequently it is comminuted, and in some instances there is a longitudinal split.
Treatment.—When the fracture is transverse, and especially when it implicates the middle or ring fingers, the most convenient method is to make the patient grasp a firm pad, such as a roller bandage covered with a layer of wool, and to fix the closed fist by a figure-of-eight bandage. In this way the adjoining metacarpals are utilised as side splints. Active and passive movements must be carried out from the first, and the bandage may be dispensed with at the end of a week or ten days.
In oblique fractures with a tendency to overriding of the fragments, especially in the case of the index and little fingers, it is sometimes necessary to apply extension to the distal segment of the digit, by means of adhesive plaster, to which elastic tubing is attached and fixed to the end of a bow splint, reaching well beyond the finger-tips ([Fig. 52]). This should be worn for a week or ten days.