Stiffness properties and linear modeling of Flex-foot: a case study

Prosthetic foot is an essential element of lower limb prosthesis، which plays an important role in the amputee gait. There is a growing trend towards development of energy storing prosthetic feet considering the amputee needs during walking. Several researches have focused on kinetics and kinematics of energy storing feet، however little is known about the mechanical properties of these commercial feet. Assess the mechanical properties of Flex-foot using its force-deformation curve and a linear elastic model. This was a case study in which gait of a healthy subject was analysed and maximum force of 800 N was defined as applied load on the prosthetic foot. Load-deformation test was performed on heel and forefoot regions of Flex-foot using a testing machine. A linear elastic behaviour was assumed، and thus the slope of the force-deformation curve was defined as the stiffness. The linear elastic model was found relatively appropriate (R2 > 0. 9). The stiffness in heel and forefoot was found to be 88. 85 and 74. 54 N/mm، respectively. The results of this study show that a linear elastic model could predict mechanical behaviour of this foot adequately. The higher stiffness in heel compared to forefoot is an indicator of greater storing capacity in this region.