The finite element analysis for endochondral ossification process of a fractured tibia applied with a composite IM-rod based on a mechano-regulation theory using a deviatoric strain

The bone healing process of fractured tibias applied with various composite IM rods, respectively, was analyzed using finite element analysis. Based on a mechano-regulation theory with a deviatoric strain as a mechanical stimulation the process of tissue differentiation was simulated by a user's subroutine programmed by a Python code for an iterative calculation. Several representative composite IM rods (fabric composites made of a carbon/epoxy and a glass/polypropylene) were investigated to find the rod modulus appropriate for healing bone fractures. It was found that the initial loading condition was the most sensitive factor of healing performance and that the flexible composite IM rod (WSN3k [±45]nT) was able to accelerate tissue differentiation under a reasonable initial loading condition (3 point gait after surgery), resulting in early bone union.