The design and modeling of a low profile pediatric prosthetic foot

Abstract

There is a great need for a new low profile prosthetic foot for children, as the current foot from Össur has been reported to be too stiff and lack reliability. This report describes the ongoing design process of a new foot while introducing new tools to aid and accelerate design iterations. The foot’s design criteria, focused on in this report, are the design of a low profile, functional, and reliable foot that can be used in corrosive environments. New design and material selection of an injection molded top blade and a pyramid are introduced to achieve the foot’s low build height and waterproofness. Three-point bending test was performed to compare S-glass and carbon fiber composites as the structural material of the foot. The results showed that the S-glass fibers are more compliant and allow for more flexure before fracture while maintaining similar strength. This allows for a more compliant and flexible foot. Finite element models were developed to meet the functional and reliability design criteria of the foot. The models showed an acceptable correlation with experimental stiffness data and were able to calculate the stiffness of the middle blade and the foot’s assembly along with an estimation of ankle angles during loading. The models also allowed for optimization of the shape of the top blade based on contact analysis and comparison of designs to reduce interlaminar shear stress at the free edge of the middle blade. Finally, a prototype was created for comparison with other feet on the market. Results showed that the new design is much more functional and dynamic than the other low profile feet on the market and is promising for further development.