Modelling the effect of prosthetic feet and shoes on the heel-ground contact force in amputee gait

Gait laboratory measurements have been widely used to explore footwear and prosthetic effects on intact and amputee gait in spite of the confounding effects of adaptation, acclimation and inherent variability of human subjects. To facilitate understanding of the variables that affect impact forces that arise from heel–ground contact during amputee walking, a lumped parameter model is proposed to simulate the movement of the human body, prosthetic components and footwear during the period immediately following initial contact. Non-linear viscoelastic properties of prosthetic feet have a proportional relationship to both the magnitude of the impact peak and the rate of increase in the ground reaction force (GRF) immediately following initial contact. Footwear, in spite of a larger capacity to dissipate impact energy than a prosthetic foot alone, can actually amplify the magnitude of the impact peak. These results suggest limitations in the ability of conventional prosthetic feet and footwear to attenuate transmission of potential tissue-damaging forces.