Palmar carpal instability secondary to dislocation of scaphoid and lunate: report of case and review of the literature.

An isolated dislocation of scaphoid and lunate is presented. We believe that this injury was responsible for the later development of a palmar carpal instability pattern. Carpal kinematics and pertinent literature are reviewed to support this belief. In our patient, the scaphoid relationship to the trapezium and trapezoid had remained largely undisturbed. The separation of lunate and capitate, a frequent form of carpal dislocation, could be explained on an anatomical basis. The lunate remained attached to the scaphoid, but completely dissociated from the triquetrum. This provided a rare clinical model for the evaluation of the effects of triquetrolunate dissociations on carpal alignment.