Mechanical Characterization of Prosthetic Feet and Shell Covers Using a Force Loading Apparatus

Abstract

To assist in the redirection of kinetic energy many modern prosthetic feet often utilize a so called energy storing and return (ESAR) design that is achieved through dorsiflexion and elastic bending to facilitate forward propulsion during push-off. Consequently, the proper selection of the foot stiffness and mechanical response for an individual amputee is significant; however, the component stiffness and mechanical properties between manufactures remains largely unreported. This study reports independent characterization of TLM Prosthetics TaiLor Made foot with interchangeable springs and Freedom Innovations Renegade foot using mechanical testing techniques to determine the stiffness, viscoelasticity, and localized material strain in prosthetic feet and their cosmetic covers. Mechanical data are acquired during the compressive loading of the prosthetic foot via force-deflection sensors and digital image correlation. In doing so, this contribution demonstrates a curtailed characterization process that can be used to quantify properties for other modern foot prosthetics.