Evaluation of the mechanical behavior of a direct compression molded porous tantalum-UHMWPEconstruct: A microstructuralmodel

Monoblock constructs, for example, porous tantalum and ultra high molecular weight polyethylene (UHMWPE), offer an opportunity to combine the fixation properties of metal-backing and the wear properties of UHMWPE for total joint replacement in one component. Aim: The objective of this research was to develop a two-dimensional microstructural finite element (FE) model to represent a monoblock-construct's structure and to investigate the influence of various design parameters on the construct's structural response. Method: A parametric study to evaluate the mechanical behavior of a direct compression molded porous tantalum - UHMWPE construct was performed through a microstructural FE modeling approach. Results: Using a factorial analysis of the overall stiffness, it was found that the most significant design parameters were the Trabecular MetalTM porosity and UHMWPE thickness. It was shown that under normal implant operating conditions (linearly elastic stress and small strain ε <0.002), increasing the porosity level and polyethylene layer thickness decreased the structure's stiffness. Conclusions: Based on different values for apparent elastic modulus from the literature and the parametric analysis, a preliminary UHMWPE thickness could be determined for a proposed design. This approach could help to develop designs in which implant stiffness is sought to be similar to the original stiffness of the biological structure and to better understand the interaction between the main parameters.