The kinetics of normal and prosthetic wrists.

The purposes of this study were (1) to describe normal wrist kinetics, and (2) to investigate the in-vitro kinetics of four currently available wrist prostheses (Swanson, Meuli, Volz, Hamas). The effective tendon moment arms of the six major wrist muscles were determined through the use of load cells and applied weights. Testing was conducted in a neutral wrist configuration with hand pronation-supination both constrained and unconstrained. The results indicate that each of the muscles studied has a unique set of effective tendon moment arms about the normal wrist as well as about wrists with the implanted prostheses, and that none of the prosthetic wrists studied duplicated normal wrist kinetics.