The dislocations at the wrist may be due to traumatism or may occur spontaneously. There may be either a displacement of the carpus at the radiocarpal joint or of the ulna at the inferior radio-ulnar articulation. These luxations are very rare.

Dislocations At The Radiocarpal Joint

It is to Dupuytren that we owe the recognition of the fact that what were previously regarded as luxations of the wrist were really cases of fracture, usually of the radius. True luxations are exceedingly rare; they may be either backward or forward and are often compound. They are usually the result of great violence and the ends of the radius and ulna in many cases protrude on the palmar or dorsal surface.

Backward luxation is the more common of the two. The question of diagnosis is most important in relation to this injury. Many cases which have been diagnosed as luxations afterwards prove to be fractures. In backward luxation the deformity resembles that of Colles's fracture, with the following differences: the palmar swelling in dislocation extends farther down toward the hand than is the case in Colles's fracture, - this is owing to the displacement occurring at the joint instead of some distance above, as in fracture; in luxation the protrusion forming the hump on the dorsal surface has an abrupt upper edge which is lacking in cases of fracture, and both styloid processes - of the radius and the ulna - remain attached to the shaft of the bones.

Anterior luxation may occur from injury, but more commonly it is seen in the form of a subluxation which occurs slowly and spontaneously usually between the ages of 16 and 25 years. It was first described by Dupuytren and later by Madelung. The ulna projects markedly toward the dorsal surface while the radius is somewhat less prominent; there is a marked hollow on the palmar surface of the forearm just above the hand. Fig. 357, from a girl 18 years of age, shows these points clearly.

Dislocation Of The Ulna At The Lower Radio-Ulnar Joint

The ulna may be dislocated forwards or backwards. When associated with fracture of the radius it is not so rare, but otherwise it is seldom seen. Posterior luxation is the most common. The internal lateral ligament and triangular cartilage both usually remain attached to the lower end of the ulna, which projects markedly on the dorsal surface. The injury has been produced by falls on the hand and forced pronation.

In recent cases reduction can usually be accomplished by direct pressure and rotation of the hand, with traction. The secret of success in the diagnosis of these obscure fractures and luxations in the region of the wrist lies in knowing the surface anatomy and in being able to recognize the various deeper structures by the sense of touch.