Tuning the Functionality and Topology of a Femur Implant by Metamaterials

This investigation has led to a new femur hybrid metaimplant with enhanced properties. It consists of honeycomb and auxetic cells with a tuned material ratio along the femur stem. In the design of the metaimplant, we focused on creating the desired lateral expansion, which makes it a good candidate as the personalized femur implant, decreasing the chance of bone–implant interface failure. For this aim, analytical and computational homogenization methods are used to evaluate a hybrid metamaterial under off-axial compression loading. We show that the lateral expansions of the metamaterial are widely tunable by tailoring Young’s modulus, Poisson’s ratio, and the material ratio of the constituent materials. The hybrid metamaterial outperformed all-auxetic and all-honeycomb designs in terms of bilateral expansion, and the one with maximum lateral expansion was selected for implementation in the design of the metaimplants. The resulting metaimplants show compression on either side of the implant and give smoother stress distribution and lower stress concentration at the contact region of the implants with the femur bone surfaces in comparison to the solid and porous femur implants.