The effect of bone remodelling on bone ingrowth into a novel porous hip implant—a finite element study integrated with a mechanoregulatory algorithm

Peri-prosthetic bone remodelling and bone ingrowth into porous implants are two different evolutionary processes that occur simultaneously post-implantation. Local mechanical stimuli generated in the implant-bone structure play a major role in these processes. Bone remodelling changes the bone density, influencing the local mechanical stimuli. Independent numerical predictions of bone remodelling and bone ingrowth have been reported in the literature. However, the influence of bone remodelling on bone ingrowth has rarely been investigated. The objective of this numerical study was to determine the effect of bone remodelling on bone ingrowth into a lattice porous hip stem using computed-tomography (CT) based model of a femur. In the finite element models, bone material property was assigned based on the CT-grey value. Peak loadings for normal walking and stair climbing were applied. Bone remodelling was simulated in the implanted bone macromodel using a strain-energy-density based phenomenological bone remodelling algorithm. Whereas, bone ingrowth was simulated on four submodels using a mechanoregulatory algorithm. A mapping framework was developed to exchange information between the macroscale model and the submodels. The simulation of bone ingrowth without bone remodelling predicted 72%-91% of bone ingrowth considering all submodels. When bone remodelling was integrated with bone ingrowth simulation, the amount of bone ingrowth was reduced to 66%-81%. Computational model-based validation indicated that the lattice-porous hip stem could achieve an estimated bone in growth of at least 66% under simulated bone remodelling conditions. Consequently, the average Young's moduli of the newly formed tissues (in four submodels) were found to be lower when bone remodelling was integrated with the bone ingrowth simulation. Prediction of bone ingrowth was considerably influenced by the bone remodelling process.