Test Protocol to Assess the Adaptability of a Prosthetic Foot on Irregular Surfaces

Foot prostheses, when used on irregular surfaces, face significant adaptability challenges because many conventional designs do not include foot structures that enhance this capability. To evaluate the performance of prostheses in such conditions, tests are performed to measure variables associated with stability during gait, which involves using specialized equipment, recruitment of users, and approval of ethical protocols, which increases both costs and validation time. The work proposes an experimental methodology based on load tests according to category P5 of ISO 22675 and interaction tests with irregular surfaces as a preliminary filter to identify promising designs for in vivo testing. In load tests, the design provides a return energy greater than 92% at any stage (heel strike, mid-stance, and toeoff) and a stiffness of $62.15 \mathrm{kN} / \mathrm{m}$ and $1.91 \mathrm{kNm} / \mathrm{rad}$ at toeoff, values comparable to LP Vari-flex prostheses. In addition, the design has 95% greater heel stiffness than commercial prostheses. The interaction tests with irregular surfaces showed that more significant obstacles cause an increase in the ankle compensatory angle and a reduction of the support polygon length. Additional tests are required to assess the influence of the load on the compensatory ankle angle and the support polygon length since the 15 N loads did not allow the complete deformation of the elastic element of the prosthesis, which could potentially limit its performance.