Methodological analysis for enhancing vertical shock absorption and transversal rotation in prosthetic feet; examination of solutions and prototype development

Abstract

Rotational stress and vertical shock impacts on the stump pose everyday risks of injury which can heavily influence the prosthetic users mobiliy. Torsion and shock adapters for prosthetic feet address these critical risks, allowing rotational movement and absorbing impact forces, significantly reducing the risk of injury for prosthetic users, and improving ambulation. However, current adapters do not offer enough adjustability and functionality to fully meet these needs. This research develops and tests a functional prototype platform of a novel adapter design featuring gradually increasing torsion stiffness over range ofmotion, separately adjustable stiffness for left and right rotations, soft end stops for left and right, a smooth return to the neutral position, and allows for the locking of the mechanism. Initial exploration included compliant mechanisms, carbon springs, and polyurethane (PU) foam, which was ultimately chosen for its superior functionality, cost-effectiveness, and user satisfaction. The user tests rated the prototypes higher than Össur’s Pro-Flex LP Torsion, scoring 82.5 and 82 of 110 points, outscoring the latest product with a score of 46.5. These results highlight the potential of precompressed PU foam to improve prosthetic adapters, emphasizing the importance of high customization for users. Future designs should focus on fully integrating vertical shock absorption and developing a functional prototype optimized for the use of PU foam to reduce weight and size and improve robustness.