Foot model for investigating foot biomechanics and footwear design

Information on load transfer of foot internal structures as well as the foot-support interface during various activities is useful in enhancing biomechanical knowledge for foot support design. Modeling of the human foot and ankle is challenging because of the very complex structures. Computational models can be used to understand joint biomechanics and design proper foot supports. Three-dimensional geometrically accurate finite element (FE) models of the human foot-ankle structures were developed from reconstructed magnetic resonance (MR) images. The foot FE model consists of 28 separate bones, 72 ligaments, and the plantar fascia, embedded in a volume of encapsulated soft tissue. The main bone interactions were simulated as contacting deformable bodies. The analyses took into consideration the nonlinearities of material properties, large deformations, and interfacial slip/friction conditions. A series of experiments on human subjects and cadavers were conducted to validate the model measurements. These experiments recorded plantar pressure distribution, foot arch and joint motion, and plantar fascia strain under different simulated weight-bearing and orthotic conditions of the foot. The validated models can be used for parametric studies to investigate the biomechanical effects of tissue stiffness, and orthotic performances on the foot-ankle complex.