Multiscale changes in bone due to bio-resorbable implants

Bio-resorbable tissue replacements have moved into the focus of research in recent years. Particularly promising candidates for bone implants are magnesium-based alloys, whose biocompatibility and principal suitability as implant material have been demonstrated. Since bone is a complex, highly adaptive material and known to react to mechanical stimuli and chemical influences, implant placement and successive degradation can be expected to alter the bone structure, which is also supported by our preliminary results. Nevertheless a detailed study of the multilevel structural changes of bone during degradation of resorbable implants is still missing. This is of greatest scientific interest because it represents a model system for bone response to a continuously changing healing front and changing load situation. It is also of prime importance for future clinical use of bio-resorbable implants and optimization of medical treatment. The main aim of this project is therefore to elucidate the multiscale structural changes in bone caused by a degrading Mg-implant, the correlation of structural changes with changing loading patterns and studying the consequences for the mechanical performance of bone. To this purpose we propose to investigate the local morphology and nanostructure in rat bone both at the interface to bio-resorbable magnesium implants, and further away from it. Since bone is a complex 3- dimensional material, these structural investigations and mechanical modeling shall be conducted in 3D as well. They will be carried out at several time points during implant degradation and shall be correlated to the degradation kinetics, healing process and mechanical loading pattern. The influence of mechanical stimuli by physical training shall also be studied. For this purpose we will combine the x-ray computed tomography with micrometer resolution (CT) with nanostructure investigations using scanning small-angle x-ray scattering (SAXS) and SAXS tensor tomography, recently developed at the Paul Scherrer Institute. Structural 3D information on multiple length scales (macroscopic/micrometer/nanometer) shall be combined with local mechanical data and fed into multiscale models. Also potential systemic effects on the body shall be monitored. This approach will allow us to gain a comprehensive picture about bone adaptation and develop models that can serve the understanding and prediction of bone response and mechanical performance after resorbable implant placement and degradation.

Bio-resorbable tissue replacements have moved into the focus of research in recent years. Particularly promising candidates for bone implants are magnesium-based alloys, whose biocompatibility and principal suitability as implant material have been demonstrated. Since bone is a complex, highly adaptive material and known to react to mechanical stimuli and chemical influences, implant placement and successive degradation can be expected to alter the bone structure, which is also supported by our preliminary results. Nevertheless a detailed study of the multilevel structural changes of bone during degradation of resorbable implants is still missing. This is of greatest scientific interest because it represents a model system for bone response to a continuously changing healing front and changing load situation. It is also of prime importance for future clinical use of bio-resorbable implants and optimization of medical treatment. The main aim of this project is therefore to elucidate the multiscale structural changes in bone caused by a degrading Mg-implant, the correlation of structural changes with changing loading patterns and studying the consequences for the mechanical performance of bone. To this purpose we propose to investigate the local morphology and nanostructure in rat bone both at the interface to bio-resorbable magnesium implants, and further away from it. Since bone is a complex 3-dimensional material, these structural investigations and mechanical modeling shall be conducted in 3D as well. They will be carried out at several time points during implant degradation and shall be correlated to the degradation kinetics, healing process and mechanical loading pattern. The influence of mechanical stimuli by physical training shall also be studied. For this purpose we will combine the x-ray computed tomography with micrometer resolution (CT) with nanostructure investigations using scanning small-angle x-ray scattering (SAXS) and SAXS tensor tomography, recently developed at the Paul Scherrer Institute. Structural 3D information on multiple length scales (macroscopic/micrometer/nanometer) shall be combined with local mechanical data and fed into multiscale models. Also potential systemic effects on the body shall be monitored. This approach will allow us to gain a comprehensive picture about bone adaptation and develop models that can serve the understanding and prediction of bone response and mechanical performance after resorbable implant placement and degradation.