Finite element contact stress analysis of the diabetic foot and foot orthosis - A three-dimensional analysis

The objective of this research is to utilize the finite element method to analyze the contact stress between a diabetic plantar and the orthosis used in treating ulcers. It is desirable to understand the stress distributions between plantar and functional foot orthosis made of different insole materials. In this research, 3-dimensional finite element models of the foot in contact with regular insole and with custom foot orthosis were built and a commercial finite element analysis package - MARC was used to investigate the contact pressure distributions at the plantar. Deformable contact bodies were used to simulate the contact behavior between the foot and the orthosis. The geometry of the foot was obtained from MR images, and the boundary conditions were set to be the maximum pressure in the gait cycle. The plantar was divided into nine regions named big toe, toes, first metatarsal, second metatarsal, third metatarsal, fourth metatarsal, fifth metatarsal, arch and heel. The reductions of average stresses in different regions were 49%, 41%, 74%, 61%, 24%, 64%, 62%, 37%, 53% respectively; and the reductions of peak stress were 49%, 69%, 61%, 63%, 14%, 77%, 68%, 62%, 75% respectively. The results from this research can provide valuable information for orthosis designers and makers for diabetic patients.