[Carpal Malalignment in Malunited Fractures of the Distal Radius].

Purpose: To evaluate and classify carpal alignment in malunited fractures of the distal radius.

Materials and methods: On standardized lateral radiographs of the involved wrist of 72 patients with a symptomatic extra-articular malunion of the distal radius, 43 with a dorsal and 29 with a palmar angulation, radius tilt (RT), radiolunate (RL) and lunocapitate angle were measured. Malposition of the radius was defined as RT plus 11° in dorsal malunion and RT minus 11° in palmar malunion. A palmar tilt of the radius was marked with a minus sign. At the time of corrective osteotomy 9 dorsal malunions underwent for different reasons evaluation of the scapholunate ligament with 4 having a complete scapholunate ligament disruption.

Results: With respect to the RL-angle, carpal malalignment was categorized as follows: type P with a RL-angle less than -12°, type K with a RL-angle between -12 and 10°, type A with a RL-angle more than 10°, but less than the malposition of the radius, type D with a RL-angle greater than the malposition of the radius. All types of carpal malalignment were found in both, dorsally and palmarly tilted malunion. Type A carpal alignment was identified as the leading type in dorsal malunion (25 out of 43 patients), whilst in palmar malunion colinear subluxation of the carpus (type C) was the dominant type (12 out of 29 patients). To return the hand to a neutral position the rotation of the lunate was compensated by a contrarotation of the capitate in the dorsal malunion. In the palmar malunion a dorsal extension of the capitate returned the hand to a neutral position. In 4 of the 5 patients with type D carpal alignment, who had scapholunate ligament evaluation, a complete ligament tear was found.

Conclusion: In this study four different types of carpal alignment in malunited extra-articular fractures of the distal radius were identified. Based on this data we suspect that type D carpal alignment in dorsal malunion may be associated with a scapholunate ligament tear. Therefore, we recommend wrist arthroscopy for this group of patients.