Experimental Assessment of the Hip Trajectory Error Framework for Designing Prosthetic Feet for Above-Knee Amputees During Walking

Providing a well-fitting prosthetic foot can improve a user's mobility and satisfaction with their lower-limb prosthesis, but achieving high performance with a prosthetic foot for people with an above-knee amputation can be challenging. Prosthetic feet are generally designed for the needs of below-knee amputees, and these devices do not account for the unique gait patterns common to above-knee amputees, such as a lack of early-stance knee flexion, which can limit potential user outcomes. Hip Trajectory Error (HTE) is a novel framework for designing prosthetic feet that enables near able-bodied hip motion and accounts for this gait deviation. In this study, the performance of HTE feet was compared to users' daily-use prosthetic feet and to predictively designed prosthetic feet for below-knee amputees that have shown close replication of able-bodied biomechanics. The performance of each prosthetic foot was characterized by the deviation of kinetics and kinematics from able-bodied data. The study also evaluated how each prosthetic foot interacted with passive knee mechanisms by investigating the center of pressure (CoP) and ground reaction force orientation throughout the stance phase. After minimal acclimation time, HTE feet demonstrated significantly better performance than the below-knee-specific alternative and the same performance as daily-use prosthetic feet that were chosen and tuned specifically to the user. This work validates and quantifies the benefits of using the HTE framework for designing high-performance prosthetic feet specific to the needs of above-knee amputees.