Abstract


Background: Lower limb amputations significantly impact an individual’s mobility and quality of life. Passive-elastic prosthetic feet are often prescribed to restore ambulatory functions; however, selecting the correct prosthesis for patients is challenging due to the diverse mechanical properties and designs of commercially available prostheses. Furthermore, prosthetic prescriptions rely heavily on clinical judgment rather than patient feedback. Current alternatives for prosthetic foot trials face logistical and practical limitations.

Objective: This study aims to develop and evaluate a novel ankle prosthesis emulator capable of emulating the mechanical behaviour of multiple commercial passive-elastic prosthetic feet, allowing for rapid back-to-back trials in both clinical and real-world environments.

Methods: The Variable Stiffness Prosthetic Ankle (VSPA) was modified to accommodate a multicam mechanism, allowing the emulation of five different prosthetic feet. Mechanical properties, such as the torque-angle relationship, were characterized for the emulated feet using finite element analysis (FEA) and mechanical testing with a 3D-printed prototype. The FEA predicted results and experimental results were compared with the original commercial prosthetic feet data to validate the emulator.

Results: The FEA predicted torque-angle relationship of the emulated prosthetic feet closely matched the mechanical properties of their corresponding commercial feet, with percentage errors of 2.87% in dorsiflexion and 9.28% in plantarflexion. The torque-angle relationship generated from the 3D-printed multicam mechanism exhibited a similar nature to the experimental data. However, the torque magnitudes were significantly less than the actual prostheses. The switching mechanism of the cam profiles was also successfully demonstrated by the 3D-printed setup.

Conclusion: Based on FEA the novel ankle prosthesis emulator can effectively replicate the mechanical behavior of commercial prosthetic feet, demonstrating its potential as a cost-effective and time-efficient tool for patient trials and prosthesis selection. However, the same needs to be validated based on real-world tests using the manufactured prototype. The 3D-printed multicam mechanism was not able to effectively emulate the commercial feet due to the dissimilarities in material properties of the 3D-printed and proposed components. Future work should focus on manufacturing the mechanism using the proposed materials and optimizing the structure to reduce weight and complexity for long-term clinical applications.