Hip Trajectory Error: A Framework for Designing and Evaluating Passive Prosthetic Feet for People With an Above-Knee Amputation

This paper presents a novel hip trajectory error (HTE) framework for designing prosthetic feet specifically for people with an above-knee amputation. Finding a high-performance prosthetic foot for people with an above-knee amputation can greatly improve mobility and prosthesis satisfaction of a user and provide a predictable interaction with the knee prosthesis. The HTE framework accounts for the lack of early and midstance knee flexion, a common gait deviation in people with above-knee amputation compared to people with a below-knee amputation and able-bodied subjects. The goal of the HTE framework is to design prosthetic feet that closely replicate able-bodied hip motion, a kinematic target that is correlated with sufficient shock absorption lost due to the lack of knee flexion during early and midstance. This paper presents a design process to optimize HTE prosthetic feet and shows that the performance of the foot is not constrained by ankle height determined by the prosthetic knee choice. In simulation, HTE feet also demonstrate a closer replication of able-bodied hip motion compared to lower leg trajectory error framework, which designs prosthetic feet specifically for people with a below-knee amputation. The HTE framework may provide the above-knee amputee population around the world with high-performance prosthetic feet designed specifically for their needs, which could improve the overall function of the prosthetic limb and user satisfaction.