Method for Predicting Deformation Characteristics of Prosthetic Feet

Abstract

ABSTRACT Introduction Although clinical studies have found that individuals with amputation prefer prosthetic feet that provide energy return, biomechanical studies investigating these findings have been mixed. The objective of this study was to develop a method that predicts the deformation of a prosthetic foot during a standardized loading profile representing gait. The specific aim was to provide insight into the timing aspects of mechanical properties influenced by features of the device. Materials and Methods Mechanical properties were measured from a series of force-deflection curves obtained at specific loads and shank angles extracted from a standard dataset used in ISO22675. Five commercially available prosthetic feet with differing design features and structural properties were analyzed to provide the predicted vertical deflection as a function of normalized stance time. Results The method successfully identified differences in features across different designs and across differing weight classes of a similar design. Furthermore, it was observed that in most specimens tested, the predicted peak displacement did not occur at the peak loading. In the heel, peak displacement led the peak force, whereas in the forefoot, peak displacement lagged the peak force. The observations of heel displacement lead and forefoot displacement lag reflect the nonlinear mechanical characteristics of these devices and the complex loading expected during gait. Conclusion The method extends those currently used by describing deformation throughout stance and predicting temporal aspects of prosthetic foot mechanical properties related to loading during prosthetic gait. Future studies should address how individual user loading characteristics affect these measurements.