Comparison via Roll-Over Shape of the kinematic performance of two low-cost foot prostheses

Bench tests are not sufficient to compare the performance of foot prostheses since only the dynamic behavior can be evaluated in the testing machines. This work supplements the bench tests described by several standards with a single patient (below knee amputee) kinematic evaluation using the concept of Roll-Over Shape to compare two low-cost prostheses against the sound limb. The Roll-Over Shape is generated first, by experimentally obtaining the trajectories of the patient´s ankle, knee, and center of pressure throughout the stance phase of the gait cycle; and second by mathematically transforming these trajectories into a shank-based coordinate system with the ankle as origin. Unlike previous work that compares the roll-over parameters obtained via the quasi-static method, this paper compares the roll-shape of a trans tibia amputee wearing eather a SACH foot, or a high energy return foot (TEC-LIMBS), and the contralateral sound limb. The outcomes demonstrate a lower difference in the Roll-over radius of the TEC-LIMBS foot with respect to the sound limb (<;10%), while the SACH foot presents a greater difference with respect to the sound limb (>40%). The findings of the tests performed in this study indicate that the TEC-LIMBS foot has a better kinematic performance than the SACH type prosthesis, a prosthesis widely used for humanitarian purposes.