Designation and Analysis of the Effective Parameters on the Performance of the ESAR Prosthetic Foot

Abstract

The energy-storing and releasing (ESAR) prosthetic foot permits capturing the elastic energy and then returning it as forward propulsion. Although ESAR has been widely accepted by the majority of amputees, the selection of an alternative prosthetic for a certain user is always related to clinical feedback rather than engineering standardization. This work aims to identify the influential design parameters in the geometry of the ESAR prosthetic foot. The whole study specified four effective parameters and assigned four iterative analyses, namely: foot thickness (t), ankle curvature (Ra), keel slope (θ), and base plate convexity (Rb). To examine the induced stress, displacement, and the amount of energy stored during the gait cycle, the numerical stress analysis was performed by the finite element method using Ansys software. The recorded data confirmed that by modifying the geometric factor magnitudes, reliable outcomes can be obtained in terms of structure strength, stiffness, and energy storage level. The estimation of the desirable quantities of the effective coefficients was established by agreement between the amount of energy stored and an adequate plantar flexion angle ( 0> θplantar \geq 15°) and dorsiflexion angle ( 0 >θdorsi \geq25o ). The numerical analysis of foot components demonstrated higher induced stress and deformation in the keel region. The generated stresses and displacements are reduced when increasing foot thickness (t) and base plate curvature (Rb), while they increase when increasing keel slope (θ) and ankle radius (Ra). Parametric analysis indicates that the energy storage level is substantially dependent on ankle radius (Ra), particularly in the keel part of the prosthetic foot.