Multiscale tissue-specific bone models have not yet been realised as this requires data on tissue-level strain fields in whole bones. This cannot be obtained through experimental measurements and numerical simulations are limited in scope. Whole bone models that are tissue specific would be invaluable to researchers in unravelling the relation between bone microstructure and function. Scientists on the project TISSSPECBONEFEM (Incorporation of multiscale tissue-specific properties into musculoskeletal finite element modelling) worked to develop accurate bone models using finite element (FE) analysis on sheep femur. Researchers experimentally characterised the bone geometry, bone mineral density, tissue types and microscale elastic properties of sheep femur bone. Using a site-matched database, they developed FE musculoskeletal models of the sheep femur that represented tissue-specific, anisotropic elastic bone properties as well as physiologically relevant loading conditions. TISSSPECBONEFEM collected site-matched multimodal and multiscale properties and analysed them in combination with predicted physiological strains to determine structure-function relationships. They discovered that remodelling in osteonal bones such as the femur is triggered more from the local muscular shear forces rather than bone compression and bending. Osteocytes are bone cells involved in mechano-sensing and orchestrate bone remodelling. Through FE and synchrotron X-ray phase nano-tomography, researchers analysed pore network geometry at the submicron scale and studied the in situ deformation of osteocytes. Using ultrasound-based bidirectional axial transmission measurement, researchers assessed the centimetre-scale properties of cortical bone in in vivo-like conditions. This tool would be useful in assessing case-specific bone material properties. Researchers successfully quantified bone mineralisation, complete stiffness tensor and pore network morphology. Correlation with anatomical location, tissue type and animal age provided deeper insight into their structure-function relationship as well as the remodelling process. Project members also developed a numerical framework for application on an established sheep osteotomy model to study fracture healing at different strain levels. TISSSPECBONEFEM tools, database and study outcomes could prove invaluable in designing and monitoring bone fixation implants to promote fracture healing. For the rapidly ageing European population, clinical application of such findings could improve patient mobility while reducing health care costs associated with fractures and joint replacements.
Musculoskeletal, whole bone models, rehabilitation, fractures, bone remodelling