The effects of dorsally angulated distal radius fractures on carpal kinematics.

A cadaver model was used in a biomechanical study of dorsally angulated distal radius fractures to evaluate alterations in carpal kinematics. Distal radius fractures were simulated by dorsal closing-wedge osteotomy and fixed with a custom-designed external fixator. A magnetic tracking device measured the carpal bone motions in several positions of dorsal angulation from neutral tilt to 30 degrees dorsal tilt. Changes in carpal alignment showed different patterns between each specimen consisting of a spectrum from dorsal subluxation of the entire carpus to adaptive dorsal carpal instability (DISI deformity). Components of carpal bone motion were altered markedly at all positions of dorsal angulation of the distal radius. The severity of the DISI deformity and related carpal instability correlated well with the alterations of carpal kinematics during wrist flexion and extension, whereas dorsal subluxation alone had a poor relationship with changes in carpal kinematics. The amount of DISI deformity and the degree of dorsal angulation of the radius may be prognostic factors when considering whether to perform a corrective osteotomy of the distal radius.