Influence of Loading on Tissue Differentiation and Bone Ingrowth in a Three-Dimensional Finite Element Model with the Application of Mechano-Regulation Algorithm

The objective of this study was to evaluate the effects of various mechanical loading scenarios on osseointegration of an additively manufactured surface coating for orthopedic implants. In order to mimic the implant’s geometry and structure, a specific three-dimensional finite element model with a volumetric porosity of 80% was established. The mechano-regulatory tissue differentiation algorithm developed by Prendergast et al. as modified by Liu et al., as well as the modified bone pathway algorithm, were implemented. With the applied compressive and shear displacements, the simulation can predict tissue differentiation in the interface between host bone and a porous scaffold coating. The results were compared for the different algorithms and levels of applied micromotion with four major conclusions. First, the model without any loading resulted in resorption of the entire interface. Second, the application of the smoothing procedure ensured the outcomes provide a continuous process of gradually evolved tissue differentiation. Third, most of the differences between the two different computational algorithms were seen in the early iterations, while the overall tissue distributions were similar at the completion of the simulation. Fourth, low levels of shear micromotion stimulated successful bone ingrowth in the model, while 20 µm or higher shear micromotion caused the interface’s failure, which is similar to the clinical outcome for similar ingrowth surfaces.