A Quasi-Static Gait Simulator for Testing Transtibial Prostheses: Taking Steps While Standing Still

We present a novel gait simulator designed for lab-based testing of transtibial prosthetic sockets. Existing simulators are generally based on complex, expensive treadmill systems. Using the well understood kinetics of gait, we propose a pylon-stationary simulator that uses three electro-pneumatic actuators to replicate the forces and moments experienced by a transtibial prothesis during gait while holding the prosthesis relatively still. We verified the simulator's ability to reproduce specific and general walking gait loads applied to a prosthetic socket using both rigid and compliant mock residual limbs. The simulator accurately replicates vertical and horizontal forces and sagittal plane moments at frequencies up to 0.2 Hz. However, the simulator struggles to replicate sagittal plane moments at higher frequencies, particularly when the socket is highly compliant or poorly fitted. Internal force and moment measurements showed inaccuracies in the presence of large displacements associated with rocking or pistoning, highlighting areas for improvement. Despite its limitations, the proposed simulator provides a versatile and affordable tool for quantitatively assessing prosthetic socket and component performance, or testing novel concepts prior to clinical trials. Future improvements, including enhanced sensor integration, more advanced control schemes, and a user-friendly interface, will expand its utility and impact.