Development of customized finite element models of medial column fixation using an intramedullary beam: A computational sensitivity analysis

Intramedullary beaming is commonly used for medial column arthrodesis to prevent or correct rocker-bottom deformities; however, the biomechanics of these reconstructions have not been rigorously studied. Customized FE models of intramedullary beaming of the medial column were developed and compared to a previous cadaveric study, which resulted in a strong correlation in medial column stiffness (ρ = 0.83, p = .079) and implant failure locations. A design of experiments was performed to quantify the models' sensitivities to varying cortical shell and cartilage thicknesses, cancellous bone and cartilage elastic moduli, and surgical medial column compression distance. Cartilage thickness and cartilage elastic modulus had the largest impact on medial column stiffness and compression distance had the greatest effect on cartilage contact area. Cortical shell thickness and cancellous bone properties did not have a significant effect on the measured parameters for the values tested. Overall, the FE models exhibited behavior that is consistent with known mechanical principles related to bending and composite structures as well as the experimental results. This study elucidates the effects of varying commonly assumed model parameters that can aid future studies aimed at screening implant designs.