To Örebro University

Hypothesis A radial hemiarthroplasty could obviate difficulties related to distal component loosening of the total wrist arthroplasty. The aim of this study is to investigate kinematically, the feasibility of a new design for radial wrist hemiarthroplasty.

Methods Six, fresh-frozen cadaveric wrist specimens were used. Testing was performed on the native wrist, after insertion of a radial hemi-arthroplasty with intact proximal carpal row (Hemi) and with proximal row carpectomy (Hemi+PRC). Each wrist was fixed to an experimental table with the tendons of the 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) attached to the apparatus. Range of motion, axis of rotation, and muscle moment arms were recorded in manually controlled movements in wrist flexion/extension, radial/ulnar deviation, dart throwers motion, and circumduction.

Results A statistically significant decrease in flexion range of motion occurred between the intact and Hemi conditions and between the intact and Hemi+PRC conditions with no significant differences in flexion range of motion occurring between the Hemi and Hemi+PRC conditions. No statistically significant changes in range of motion occurred in extension, radial deviation, ulnar deviation, flexion/ulnar deviation component of the dart throw, extension/radial deviation component of the dart throw, or circumduction functional tests.

Summary Points This study indicates that the new wrist radial hemiarthroplasty can produce a stable wrist with range of motion similar to the native wrist. Overall, wrist kinematics appears to be equally acceptable in hemiarthroplasty with and without resection of the proximal row.