Finite element framework for investigating the mechanical response of podiatric insole: A pilot study

In podiatry, polymeric orthopedic insoles are widespread, to optimize athletic performances or for diabetic care. Despite computer-aided design development, the choice of materials, their distribution in the sole and their thickness is empirical. The research question of this study is to determine the relationship between the properties of the materials of a sole, the stacking of these materials, and the overall mechanical response of the sole. Cohort studies are inefficient to solve this complex problem, due to numerous parameters, nor to elucidate the effort transmission through the insoles. In this study, finite element simulations are used for the prediction of the pressure distribution at the interface between the foot and the insole for a range of commercial podiatric insole materials with Shore hardness between 18 and 60 (3 ethylene vinyl acetate copolymers, Poron© polyurethane and an elastomer). After measuring the mechanical properties of these materials, the simulated pressure distribution under various insoles was compared to measured pressure distribution. For 15 configurations, simulated pressure agrees with measured pressure for 84% of the sensors. In addition to validating the finite element methodology for podiatric insoles, the hyper foam law parameters determined for each material in this study can be used to predict the mechanical reaction of insole - foot systems.