Manufacturing and finite element assessment of a novel pressure reducing insole for Diabetic Neuropathic patients

Diabetes is one of the metabolic diseases. Uncontrolled diabetes can lead to diabetic foot ulcers and if it was not treated would lead to amputation. Foot ulcers can be prevented by using suitable insoles which are made of appropriate material and geometrically designed by constituent layers. In this study, single-layer and three-layer insoles have been compared during static and dynamic loading. The selected materials were silicone gel (SG), plastazote foam (PLZ), polyfoam (PF) and ethyl vinyl acetate foam (EVA). Four single-layer and 18 combinations of three-layer insoles were selected. Materials behaviors were determined by using a uniaxial pressure test. The description of stress and strain is obtained by using the model of three dimensional nonlinear Finite Element Method (FEM). Then samples were tested by using commercially available plantar pressure measurement system. The FEM results showed that the SG and PLZ insoles are more appropriate compared to single-layer insoles. The combinations of PLZ, SG and EVA (from top to bottom) are recognized as the best between three-layer insoles. Also the best three-layer insole is more effective in promoting a favourable stress and strain distribution than single-layer insoles, especially in dynamic mode. According to simulation results, three-layer insole decreases stress concentration by 9 %. Also experimental tests showed that using three-layer insole decreases plantar pressure by 63 % compared to barefoot condition bare foot