Midcarpal instability caused by malunited fractures of the distal radius.

Thirteen patients with malunited fractures of the distal radius developed symptoms of pain and instability of the midcarpal joint. In six cases, a recurrent voluntary midcarpal subluxation was also present during ulnar deviation. These symptoms were first noticed several weeks, and at times several months, after all immobilization for the treatment of the original fracture had been discontinued. We believe that the loss of the normal palmar tilt of the distal articular surface of the radius prepositions the carpus in a dorsal collapse alignment, which enables this instability to develop. Although the instability is localized to the midcarpus , it is treated best, in our opinion, by a corrective osteotomy of the distal radius. In nine patients, osteotomies resulted in relief of preoperative symptoms and correction of midcarpal instability. In one patient, osteotomy of the radius was deemed unnecessary because the loss of palmar tilt of the radius was minimal. Instead the midcarpal ( triquetrohamate ) joint was stabilized by ligament reconstruction. Only transient correction was obtained, with later recurrence of the voluntary midcarpal subluxation.