Title: Adaptive Gradient Elasticity and Mechanical Stimulation in Bone Remodelling
Funder: Engineering and Physical Sciences Research Council

Abstract: In nowadays ageing population, the problems related to bone loss are on the rise. As such it is of crucial importance to the public health and well-being in general to offer a strategy that can reverse bone degradation. Computational modelling strategies are needed to complement and enhance a recently developed treatment for bone degradation, namely using mechanical vibrations of low magnitude to trigger bone regrowth. The computer modelling will subsequently be used to optimise this treatment for individual patients. The project is interdisciplinary between Engineering ("mechanical vibrations") and Biomedical Sciences ("bone regrowth") and it requires strong mathematical modelling input to complement the existing experimental biomedical programme. The degradation of bone is a widespread phenomenon that is often followed by fracture. Bone degradation has various causes, most prominent of which are osteoporosis, bone cancer and common ageing. Certain groups of individuals are particularly prone to bone degradation, such as post-menopausal women. Reversing bone degradation has been recognised by leading medical specialists around the world to be of crucial importance to public health and public well-being. Bone regrowth can be stimulated by pharmaceutical measures; however, their long-term effects remain unspecified and there may be undesired side effects. More recently, research efforts have been directed towards triggering bone regrowth through mechanical stimulation. Especially dynamic loading (as opposed to static loading) is advantageous to stimulate bone growth namely through exposing the patient repeatedly (say 20 minutes per day for the duration of a year) to straining of the intensity of everyday activities such as standing. Unfortunately, the experimental programmes are expensive and require a lot of organisation and research efforts. It is also often necessary to acquire approval of the relevant Professional Institutions or Ethical Committees. As in many areas of engineering, computer modelling can be used to complement and/or partially replace the expensive experimental programmes. It is thought to be opportune to suggest in the present research computer modelling techniques that can be used to simulate bone remodelling due to vibrationary mechanical stimulation, thereby taking into account the microstructure of the bone material via a multi-scale approach. It is suggested to use upscaling techniques and translate these microstructural responses into effective properties on the macro-scopic level. The resulting models would be relatively simple to use and much more "transparent" than the associated microstructural models; thus, their use by the beneficiaries should be much more straightforward. In this research, a particular type of multi-scale techniques, adaptive gradient elasticity model, will be developed for the benefit of subsequent applications. Finally the dependence of bone stimulation on the various aspects of the mechanical vibration, such as frequency, amplitude and duration will be analysed. The partial sensitivities to these aspects can be quantified and subsequently used to manipulate the details of the mechanical vibrations in order to optimise bone growth and rationalising patient treatment.


Research activity codes: 5.7 PHYSICAL
Health categories: MUSCULOSKELETAL