Anatomical and radiological study applied to distal radius surgery.

PURPOSE: The purpose of this study was to determine, during anterior plating of the distal radius, the length of a screw above which there is a risk for the extensor tendons and the optimal shape of an anterior plate. It was also to determine the projection of the axis of the distal third of the radius on the distal articular surface in case of wrist arthroplasty in order to simplify the procedure.
METHODS: We studied 74 dry radii from adult cadavers. Each one underwent a CT scan. We measured the thickness of each radius at the dorsal tubercle level, at the second compartment level and at the third compartment level. We calculated the metaphyseal-epiphyseal angles of the lateral column and of the intermediate column (Rikli and Regazzoni in J Bone Joint Surg (Br) 78(4):588-592, 1996). We also calculated the projection of the longitudinal axis of the most distal 7 cm of the radius on the distal carpal surface of the radius.
RESULTS: Mean thickness at the dorsal tubercle level was 22.1 mm (18-26.1). The mean slope of the lateral column was 155° (143-167) while that of the intermediate column was 145° (134-153). We have found a statistically significant difference (p < 0.0001) between these two slopes. The axis of the distal radius was projected on the posterior-lateral quadrant of the distal articular surface.
CONCLUSIONS: The emergence of new implants needs a precise evaluation of a fractured, an arthritic or a reconstructed distal radius. The double slope of the distal radius complicates the manufacturing of an "anatomical" plate. The optimal shape is between these two slopes. Moreover, ancillaries for wrist replacement are still approximations, which means that it is important to know the projection of the radial axis on the articular surface of the distal radius.