Advances in materials technology have brought about a class of prosthetic foot and ankle components for the lower limb amputee, called Dynamic Elastic Response (DER). These components are designed to store energy during the stance phase of gait in a leaf spring keel, and return a portion of the stored energy at the end of stance phase to contribute to the forward progression of the limb. This energy storage and return is designed to partially replace the push-off of active ankle plantarflexor muscles in late stance.

Typical subjective responses to DER feet are favorable. However, the majority of research investigations seeking to compare different DER designs have concluded that the feet offer no advantage over a conventional lower limb prosthesis. One goal of this research is to improve upon several of the techniques used in the literature to evaluate DER feet, contributing to a better understanding of their function.

The second goal of this research is the complete characterization of the material properties of an existing DER foot with the eventual goal of functional theoretical modeling to serve alternative amputee populations, including the largest patient group of elderly amputees secondary to peripheral vascular disease or diabetic neuropathy.

Materials testing was performed on the DER foot in question, the Carbon Copy High Performance (HP), to determine model inputs and to evaluate the errors in the common processing method, inverse dynamics. Results indicated hysteresis in the foot structure not accounted for by inverse dynamics as well as cantilever beam deformation in the anterior of the foot apart from the anatomical ankle joint, another deficiency with the standard approach. A new method is proposed to calculate energy storage and return, utilizing power flow into the proximal foot and out of the distal foot. The method contains several theoretical advantages over existing techniques.

Material properties of the foot deformation plates and the surrounding cosmetic foam were quantified and formulated into coefficients appropriate for a rigid-body model. The foot geometry was characterized through a novel set of imaging and processing techniques to enable the accurate representation of geometry in the model.