Influence of Assumed Boundary Conditions Derived from MBS on Numerically Simulated Strain-Adaptive Bone Remodeling in the Pelvis after Total Hip Replacement

Abstract

Total hip replacement (THR) is a routine procedure mostly used for the treatment of primary osteoarthrosis of the hip joint. Despite good clinical results aseptic loosening caused by strain-adaptive remodeling processes of bone tissue is the main cause for failure of the implant. As a consequence the migration of the cup can be significant [1].The presented study is an extension of our previous research work, where remodeling processes were already calculated in the prosthetic pelvis using a static load case [2]. In the present study the same finite element (FE) model has been used but the hip joint forces were derived from the multi-body simulation (MBS) of the gait cycle of a human test subject with normal walking speed. Hence, a more realistic load case is used which is supposed to affect the simulation result. This is due to our investigations in the femur [3], where a significant different simulation result for the bone mass loss has been computed comparing static load cases and the more realistic loads applied from a study of Bergmann et al. [4].The comparison of the simulation result of the static and the dynamic load cases confirms the assumptions of a lower decrease of the average bone density in the pelvis with the dynamic load case. Furthermore, a variation in the resorption area is determined as well. On the basis of the final density distribution in the acetabulum the loading situation of a migrated prosthesis should be determined with the MBS model to estimate the influence of the cup position on the hip resultant.