Tissue ingrowth in a porous acetabular component: Influence of mechanobioregulatory stimuli

Porous acetabular component has been often used in total hip arthroplasty since they allow biological anchorage with the host bone, facilitating long term implant stability. However, the extent of the tissue ingrowth around porous metal-backing has been scarcely investigated. Using a novel multiscale mechanobioregulatory framework, the study investigated the spatio-temporal evolution of tissue ingrowth in an optimally designed functionally graded porous acetabular component. Finite element microscale models corresponding to different acetabular regions were developed, along with the macroscale model of the implanted hemipelvis. The variable implant-bone relative displacements and the host bone material properties in ten interfacial regions, were mapped from the macroscale model to microscale model. Bone formation of 0.55 - 86.65% was predicted across the microscale models, resulting in an average elastic modulus ranging between 32.52 and 1977.70 MPa. The overall average percentage of peri-acetabular bone ingrowth was ∼ 27%, with high bone ingrowth of ∼ 40 - 87% around the acetabular dome. Although the biological stimulus was favourable in vicinity of the bone layer, the mechanical stimuli in the tissue elements adjacent to the implant was found to be more favourable for bone formation as compared to the elements adjacent to bone. Predicted amount of peri-prosthetic tissue ingrowth was observed to be dependent on the biological factors, in addition to the mechanical environment. Occurrence of contact osteogenesis indicated the predominant influence of mechanical stimuli over biological factors in the predictions of bone ingrowth around functionally graded porous acetabular component.