Effect of Prosthetic Foot-Ankle Stiffness on Standing and Walking Performance in Transfemoral Prosthesis Users

The stiffness of a prosthetic foot-ankle component is typically prescribed based on a patient's weight and activity level, which may not be optimal for a particular individual. This study investigates how systematically varying prosthetic foot-ankle stiffness affects standing and walking performance. The aim is to determine an optimal prosthetic foot-ankle stiffness that will enhance standing and walking abilities for transfemoral prosthesis users. The study mechanically characterized the keel and bumper components on the College Park Venture Foot, which revealed an increasing stiffness from soft to hard configuration. Kinematic and kinetic data were collected in a motion analysis research laboratory to determine the roll-over shape (ROS) radii of the different prosthetic foot-ankle combinations. A novel method was developed to create a best-fit circle of the ROS and can be applied in future studies. Utilizing gradient descent for determining the ROS allows for a streamlined procedure while maintaining the outcome precision. The radii created by the different prosthetic keel-bumper combinations in the ROS experiment were directly proportional to their measured stiffness from the mechanical testing. These results indicate that prosthetists can prospectively prescribe a prosthetic foot-ankle stiffness to simultaneously optimize both standing and walking performance in their patients.