Assessment of Plantar Pressure in a Foot Finite Element Model Considering a Sliding Contact Between Soft Tissues

Abstract

Currently, most finite element models of the foot in literature have simplifications, mainly in terms of real and complete modeling of soft tissues and their proper transmission of the force, causing limitations in the response of the model. A deficient transmission of the force among muscles, tendons and plantar fascia occurs due to unions with other tissues or excessive displacement. These kinds of problems can be fixed, doing the separation among tissues and applying appropriated contacts or displacement constraint conditions. Therefore, the objective of this study is to evaluate changes in plantar pressure in a three-dimensional model of finite elements of a foot in the second rocker of gait when considering the relative displacement and load transmission between muscles, tendons and plantar fascia. Through scanning and 3D processing, the geometries of the tissues were obtained. First-order tetrahedral elements were used for meshing and were considered models of linear elastic and hyperelastic material. The fixed connections among tissues were separated, and in some of these areas, contacts were simulated, allowing a relative sliding of the tissues and proper transmission of force. Results obtained into this work showed a maximum contact pressure localized under the calcaneus of 0.1925 MPa for the sliding contact model (SCM) and 0.1710 MPa for the non-sliding contact model (N-SCM). These numerical values mean a variation of the plantar pressure between both models of up to 12.57%. Analysis suggests that including sliding contacts on the foot model had a significant improvement in the qualitative plantar pressure response.