Combined Bone Ingrowth and Remodeling Around Uncemented Acetabular Component: A Multiscale Mechanobiology-Based Finite Element Analysis

Bone ingrowth and remodeling are two different evolutionary processes which might occur simultaneously. Both these processes are influenced by local mechanical stimulus. However, a combined study on bone ingrowth and remodeling has rarely been performed. This study is aimed at understanding the relationship between bone ingrowth and adaptation and their combined influence on fixation of the acetabular component. Based on three-dimensional (3D) macroscale finite element (FE) model of implanted pelvis and microscale FE model of implant-bone interface, a multiscale framework has been developed. The numerical prediction of peri-acetabular bone adaptation was based on a strain-energy density-based formulation. Bone ingrowth in the microscale models was simulated using the mechanoregulatory algorithm. An increase in bone strains near the acetabular rim was observed in the implanted pelvis model, whereas the central part of the acetabulum was observed to be stress shielded. Consequently, progressive bone apposition near the acetabular rim and resorption near the central region were observed. Bone remodeling caused a gradual increase in the implant-bone relative displacements. Evolutionary bone ingrowth was observed around the entire acetabular component. Poor bone ingrowth of 3-5% was predicted around the centro-inferio and inferio-posteriosuperio-peripheral regions owing to higher implant-bone relative displacements, whereas the anterio-inferior and centro-superior regions exhibited improved bone ingrowth of 35-55% due to moderate implant-bone relative displacement. For an uncemented acetabular CoCrMo component, bone ingrowth had hardly any effect on bone remodeling; however, bone remodeling had considerable influence on bone ingrowth.