Numerical investigations of the strain-adaptive bone remodeling in the prosthetic pelvis

Abstract

Bone remodeling due to stress shielding is a major cause of hip implants aseptic loosening. Previously, investigations on this phenomenon were based mainly on clinical observations. Currently, the finite element method (FEM) has been established as a reliable and efficient computing method to examine stress shielding after total hip arthroplasty and the related bone remodeling in the prosthetic Femur. The life of hip implants is not only limited by the loosening of the prosthesis stem, but also frequently affected by the loosening of acetabular components caused - among other factors - by resorption of the bone surrounding the prosthesis due to stress shielding. However, only few numerical research studies, which focus on the FE computation of the strainadaptive bone remodeling in the prosthetic pelvis, have been published. The aim of the work presented here is to estimate the changes in the physiological load distribution and the resulting bone remodeling in a pelvis provided with a cemented acetabular prosthesis component (cup) based on FEM. Therefore, a three-dimensional FE model of the left intact pelvis half was initially reconstructed based on CT data of a male patient with 85 kg weight. In a further step, a FE model of the prosthetic pelvis was built. The anchoring of the considered acetabular prosthesis component was carried out using a homogeneous cement layer of 2 mm thickness. Then the change of the apparent bone density in the prosthetic pelvis was calculated by means of FEM and the strain-adaptive bone remodeling in the acetabular region was analyzed. The analysis of the numerical results reflects significant estimated bone loss, especially in the acetabular limbus adjacent to the cup. As a result, loosening of the cemented prosthesis component can be anticipated. © 2010 International Federation for Medical and Biological Engineering.