Replication of Coupled Movements of the Wrist: A Cadaveric Study of Total Wrist Arthroplasty

Abstract

Purpose: The purpose of this study was to determine how well the active range of motion and the forces required to achieve motions are maintained following cadaveric implantation of the ball-and-socket style total wrist arthroplasty (TWA).

Methods: An active wrist motion simulator was used to produce flexion, extension, radioulnar deviation, dart-thrower's motion, and circumduction in 14 fresh-frozen cadaveric wrists before and after TWA. Identical tendon displacements were applied to five major wrist flexors and extensors to control motion presurgery and postsurgery. Motion trials were recorded using biplanar video fluoroscopy and digitally reconstructed with 6 degrees of freedom using x-ray reconstruction of moving morphology. Wrist angles were subsequently measured with respect to an anatomically based radial coordinate system. Forces applied to the five actuated tendons were recorded by the simulator throughout all motion trials. Maximum wrist angles, dart-thrower's motion plane orientation, circumduction ellipse parameters, and peak tendon forces in pre-TWA and post-TWA conditions were compared.

Results: There were no significant differences in maximal flexion, extension, radial, or ulnar deviation angles when comparing preoperative anatomic wrists with the same wrist following implantation of the TWA. Orientation of dart-thrower's motion planes and circumduction ellipses with respect to the sagittal plane increased after cadaveric surgery, whereas the area of the circumduction ellipses remained similar. Tendon forces were similar in anatomic and TWA wrists apart from flexor forces, which decreased in flexion in TWA wrists.

Conclusions: In our cadaveric setup, the TWA was able to recreate functional motion patterns without significantly increased tendon forces.

Clinical relevance: The results of this study support the assertion that a ball-and-socket style TWA can provide a postoperative range of motion adequate to perform activities of daily living.

Keywords: Motec; range of motion; tendon force; total wrist arthroplasty; wrist motion simulation.