Bone remodelling is an equilibrium process that occurs continually throughout the mature skeleton and is known to be a function of the loading environment. The replacement of a hip produces abrupt changes in the localised loading conditions in the proximal femur and will cause preferential remodelling. The resulting changes in bone mass can lead to the loosening of the implant over long periods of time.

A technique to model the long-term adaptation process of bone has been developed using the Finite Element Method. This approach used the standard ABAQUS Finite Element software to produce swelling strains within the cortical bone to represent remodelling growth and resorption. The method has been validated against the remodelling seen in the avian ulna experimental model (Brown et al. 1995), and the results demonstrated good agreement with the remodelling patterns in the ulna mid-shaft sections. Under the conditions presented by Brown et al, it was concluded that remodelling using the most tensile principal stress stimulus produced the best agreement. In addition, the remodelling of cancellous bone has been demonstrated in this study by altering the stiffness of the material in response to the applied stimulus.

A Finite Element model of the human proximal femur has been constructed from CT scan data and implanted with an Exeter stem. The resulting remodelling showed resorption in the calcar region of the bone under both strain energy density and most compressive principal strain stimuli. The predictions demonstrated good agreement with the current evidence regarding the stimulus to which bone remodels (Weinans et al. 1993, Rubin et al. 1990)