Biomechanical Comparison of the Validity of Two Configurations of Simulators for Body-Powered Hand Prostheses

Simulators are often used in prosthesis research to evaluate new devices or characterize aspects of prosthesis use, so as to recruit participants without amputations. Simulators, in general, must locate the prosthesis somewhere other than where the intact biological limb exists. In this study, we compared two configurations of simulators for hand prostheses to determine which leads to more natural elbow and shoulder kinematics, and in turn, which is the more valid simulator. One configuration located the prosthesis in-line with the forearm, beyond the biological hand; the other located it beside the hand. We measured the kinematics of 12 non-amputee participants during three clinical tests of hand-arm dexterity, which were completed 1) using each simulator configuration with a body-powered Hosmer 5X hand prosthesis and 2) using the biological hand with a wrist brace. The beside-the-hand configuration resulted in kinematics that were more similar to those measured with the biological hand, particularly during the Box and Blocks Test, which involved navigating the prosthesis around obstacles. Therefore, we concluded that simulators with the beside-the-hand configuration are likely to better emulate the use of hand prostheses for activities involving a wide variety of arm movement. We suggest using this configuration in general, except when arm movement is of secondary importance and when this configuration would be obstructive, visually or otherwise.