Ulnar midcarpal instability-clinical and laboratory analysis.

Patients with ulnar midcarpal instability have a characteristic pattern of clinical signs and symptoms related to the midcarpal joint. The usual presenting complaint is a painful wrist click which can be reproduced by ulnar deviation, axial compression, and pronation of the wrist. Routine x-rays are usually normal, but cinefluoroscopy reveals sudden dissociation between the proximal and distal carpal rows resulting in a dorsiflexion collapse deformity. In six of our patients, conservative therapy sufficed to relieve symptoms. Four other patients required surgical stabilization. We close to stabilize the triquetrohamate joint because it was a relatively easy procedure and eliminated instability in most instances. Laboratory studies aided in understanding the pathomechanics of midcarpal instability, which consisted of dorsal subluxation of the capitate and hamate on the lunate and triquetrum. We believe that midcarpal instability is not a rare condition but may often be confused clinically with more common carpal dissociations.