Bone density growth and the biomechanics of healthy and prosthetic femur

Abstract

The development of computational models to describe bone behavior when prosthetic devices are used has gained tremendous importance. In particular, computational modeling for bone growth and resorption processes can be a useful tool to determine the implant success or failure. We present a model for investigating bone density growth for healthy and prosthetic femur with a total hip arthroplasty. The model, which is based on a continuum theory for density growth and remodeling in biological materials that accounts for the coupling between biological and mechanical effects, is implemented in COMSOL Multiphysics and two simulation examples are presented. In the first example, where mechanical loads due to daily physical activities are considered, it is shown that higher stress zones (in prosthetic femur mid-diaphysis of about 46 MPa) and lower stress zones (in prosthetic femur neck of about 28 MPa) are candidates for bone growth and resorption zones, respectively. In addition, it is shown that higher and lower stress levels in these zones may lead to possible periprosthetic fractures (bone mid-diaphysis overloaded in 7–10 MPa post-operatively) and eventually to implant aseptic loosening due to resorption (bone femoral neck unloaded in 13–17 MPa post-operatively). In the second example, where the mechanical load corresponds to the average of the loads considered previously, the obtained results for bone density are in good agreement with real bone density distribution in the proximal femur, which illustrates the model capability to locate bone density growth zones (of about 1615 kg / m 3 in the mid-diaphysis) and bone density resorption zones (of about 1259 kg / m 3 in the neck) due to mechanical loads for the femur post-operative condition after a total hip arthroplasty surgical procedure.