Effect of Total Wrist Arthroplasty Alignment on Wrist Range of Motion and Component Impingement.

Abstract

The purpose of this study was to evaluate whether total wrist arthroplasty (TWA) component alignment affects wrist range of motion (ROM), component impingement, and tendon forces. Six fresh frozen cadaver wrists were moved through five wrist motions before and after implantation of the KinematX TWA using a "refined alignment" strategy: the radial component was aligned parallel to the longitudinal axis of the forearm in the coronal plane, and the carpal component colinear with the ulnar cortex of the long finger metacarpal shaft. Comparisons were made to a prior study that tested six specimens with "classic alignment": the radial component was aligned parallel to the distal radial shaft axis, and the carpal component colinear with the long finger metacarpal shaft. Maximum wrist ROM and tendon forces were compared before and after implantation. When comparing wrist ROM between classic and refined alignments after TWA implantation, there were no significant differences in wrist flexion with either neutral or free radioulnar deviation. With the refined alignment, there was a significant increase in wrist extension at both neutral and free radioulnar deviation. There was also greater radial and ulnar deviation with the refined alignment. Only one of the six refined alignment specimens impinged in maximum radial deviation, compared with four of the six classic alignment specimens. There was no significant increase in the tendon forces during any of the five wrist motions after TWA using the refined alignment. Aligning the TWA radial component in line with the forearm axis and the carpal component in line with the ulnar cortex of the long finger metacarpal shaft increased wrist extension and radial and ulnar deviation, resulting in less component impingement. This study demonstrates the importance of implant alignment on wrist ROM and component impingement, informing both surgeons and implant designers on the refinement of surgical technique.