Pseudo fatigue test of passive energy-returning prosthetic foot

Improving in the quality of life by expanding functionality and durability while continually reducing the fabrication costs and maintaining the possibility of local fabrication, these are the four key design requirements for lower-limb prosthetics with humanitarian applications. Currently, however, there are few foot prostheses that meet these requirements. The solutions available world-wide include passive-static solid-ankle cushion-heel (SACH), passive-dynamic, and active prostheses. Perhaps the best solution available is the injection-molded one-size-fits-all Niagara foot but it is both unstable for heavier patients and not suitable to interface with patient footware, thereby limiting its acceptance in footware conscious cultures. This research focuses on demonstrating the functionality and durability of the Tec-LIMBS fiber reinforced polymer (FRP) prosthetic foot designed with the aforementioned four-fold objective. We hypothesize that a low-cost FRP passive-dynamic prosthetic foot can be manufactured locally while still meeting durability, energy-return requirements and being socially aesthetic. The prosthesis is validated first, for energy-return via static tests as compared to two other commercial products, and second, for durability through a 500,000 gait-cycle fatigue test based on the ISO 22675 standard. Both tests are conducted employing a universal testing machine. The work reported herein is a continuation of prior prototyping that compared the prostheses via roll-over shape. The designed prosthesis has a comparatively higher energy-return characteristic for both keel and heel — above the two common competitors — and has successfully passed the fatigue test without deformation. The reported testing further demonstrates that the prosthesis design is ready for in-field patient testing and manufacture.