Multiphysics and multiscale computational modelling of bone tissue

Multiphysics and multiscale computational modelling of bone tissue Experimental studies to quantify the mechanical environment surrounding bone cells are challenging and as such computational and theoretical approaches have modelled either the solid or fluid environment of osteocytes to predict how these cells are stimulated in vivo. Osteocytes are composed of an elastic cell membrane that deforms in response to the external fluid flow imposed by mechanical loading. This represents a most challenging multi-physics problem in which fluid and solid domains interact and as such no previous study has accounted for this complex behaviour. Dr. McNamara’s group employ fluid-structure interaction (FSI) modelling to investigate the complex mechanical environment of osteocytes in vivo. Fluorescent staining of osteocytes is performed in order to visualise their native environment and develop geometrically accurate models of the osteocyte in vivo. These are the first computational FSI models to simulate the complex multi-physics mechanical environment of osteocyte in vivo and provide a deeper understanding of bone mechanobiology. Experimental and computational studies have sought to understand the role of bone composition and organisation in regulating the biomechanical behaviour of bone. However, due to the complex hierarchical arrangement of the constituent materials, the reported experimental values for the elastic modulus of trabecular and cortical tissue have conflicted greatly. Furthermore finite element studies of bone have largely made the simplifying assumption that material behaviour was homogeneous or that tissue variability only occurred at the microscale based on grey values from micro-CT scans. Dr. McNamara’s group have developed a three-scale finite element homogenisation scheme to enable prediction of homogenised effective properties of tissue level bone from its fundamental nanoscale constituents of hydroxyapatite mineral crystals and organic collagen proteins. This approach could provide a preclinical tool to predict bone mechanics following prosthetic implantation or bone fracture during disease.