An anatomic and kinematic analysis of a new total wrist arthroplasty design

Background Total wrist arthroplasty (TWA) is a viable surgical treatment for disabling wrist arthritis. While current designs are a notable improvement from prior generations, radiographic loosening and failures remain a concern. Purpose The purpose of this investigation is to evaluate a new total wrist arthroplasty design kinematically. The kinematic function of a native, intact cadaveric wrist was compared with that of the same wrist following TWA. Method Six, fresh-frozen wrist cadaveric specimens were utilized. Each wrist was fixed to an experimental table and its range of motion, axis of rotation, and muscle moment arms were calculated. The following tendons were attached to the apparatus to drive motion: extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), and abductor pollicis longus (APL). The wrist was then manually moved along a guide by an experimenter through a series of motions including flexion-extension, radial-ulnar deviation, and circumduction. The experiment was then performed on the specimen following implantation of the TWA. Results Following the TWA procedure, there were statistically significant decreases in the ulnar deviation and the flexion/ulnar deviation component of dart throw ranges of motion. There were no statistically significant changes in flexion, extension, radial deviation, the extension/radial deviation component of the dart thrower motion, or the circumduction range of motion. Conclusions Kinematic analysis of the new TWA suggests that a stable, functional wrist is achievable with this design. Clinical Relevance While appreciating the limitations of a cadaveric study, this investigation indicates that the TWA design studied merits study in human populations.