Dislocations in the Region of the Wrist
Dislocation may occur at the inferior radio-ulnar, the radio-carpal, mid-carpal, inter-carpal, or carpo-metacarpal joints, but the strong ligaments of these articulations, the comparatively free movement at the various joints, and the relative weakness of the lower end of the radius whereby it is so frequently fractured, render dislocation a rare form of injury.
Dislocation of the inferior radio-ulnar articulation may complicate fracture of the lower end of the radius, or accompany sub-luxation of the head of the radius. The head of the ulna usually passes backward.
In children, the commonest cause is lifting the child by the hand, and the displacement is only partial. In adults, it may result from forcible efforts at pronation or supination, as in wringing clothes, or from direct violence, the separation being frequently complete, and sometimes compound.
The head of the ulna is unduly prominent, and there is a depression on the opposite aspect of the joint. The hand is generally pronated, the rotatory movements at the wrist are restricted and painful, while flexion and extension are comparatively free.
Reduction is effected by making pressure on the displaced bone and manipulating the joint, especially in the direction of supination. If the ligaments fail to unite, the head of the ulna tends to slip out of place in pronation and supination—recurrent dislocation.
Dislocation at the radio-carpal articulation, usually spoken of as dislocation of the wrist, is attended by tearing of the ligaments and displacement of tendons, and is frequently compound. The carpus may be displaced backward or forward, and the articular edge of the radius towards which it passes may be chipped off.
Backward dislocation is commonest, the injury resulting from a severe form of violence, such as a fall from a height on the palm while the hand is dorsiflexed and abducted. The clinical appearances closely simulate those of Colles' fracture, or of separation of the lower radial epiphysis, but the unnatural projections, both in front and behind, are lower down, and end more abruptly ([Fig. 50]). The hand is more flexed, and the palm is shortened. The styloid processes retain their normal relations to one another, and the carpal bones lie on a plane posterior to the styloids, the articular surfaces may be recognised on palpation. The forearm is not shortened.
Forward dislocation of the carpus may result from any form of forced flexion, such as a fall on the back of the hand, or from direct violence. The displaced carpus forms a marked projection on the palmar aspect of the wrist, and there is a corresponding depression on the dorsum. The attitude of the hand and fingers is usually one of flexion.
In both varieties reduction is readily effected by making traction on the hand and pushing the carpus into position. A moulded poroplastic splint, which keeps the hand slightly dorsiflexed, adds to the comfort of the patient, but this should be removed daily to admit of movement and massage being employed.