Mechanical stiffness of running-specific prostheses in consideration of clamped position

Abstract

Athletes with lower extremity amputations need to clearly understand the mechanical stiffness of running-specific prostheses to select the most suitable one. However, manufacturers do not show the detailed stiffness data, and currently, there is no standardized testing method available. In this study, load-deflection behavior and mechanical stiffness of carbon fiber composite prosthesis were evaluated under a static compressive load. Fifteen testing conditions were employed by changing the position and length of adapter jig. The results of compression tests showed all load-deflection relations to be non-linear. The mechanical stiffness increased with increasing the applied load and decreasing the adapter jig length. Immediately after loading, the backward lateral force was applied to the prosthesis shank, and then, the forward lateral force was generated in continuing loading. By interaction of the adapter jig position and length, fifteen load-deflection diagrams were classified into seven tendencies. From the observation results of deformation behavior, the product of the adapter jig position and length was defined as the positional parameter, which quantitatively indicated the clamped condition. Consequently, the evaluation method of mechanical stiffness correlated with the applied load and the positional parameter was proposed.