Development of an Internal Bone Remodelling Theory and Applications to Some Problems in Orthopaedic Biomechanics*

Bone tissue is a porous, heterogeneous and anisotropic material, which adapts its mechanical properties depending of the local stress level. This evolutive behaviour of the bone is normally known as bone remodelling. In this work, a bone-remodelling theory, based on the principles of continuum damage mechanics, is presented. The corresponding mathematical formulation has been implemented in a finite element code in order to predict the bone response after implantation of a prosthesis or fixation. Although the present model is not based on experimental verification, the model predicts important qualitative experimental results, being still necessary to test against experimental/clinical work. The main aim of this paper has been, therefore, the qualitative study of the long-term bone evolution, especially of the human femur when different types of implants are employed. A comparative analysis between two widely used hip prostheses (the Exeter and the SHP), has been performed. We have also studied the treatment of proximal femoral fractures by means of extramedullary and intramedullary implants.