Micro-computed tomography studies of biomaterials and bone

This thesis is presented in two parts; the first part is a study of the structure and properties of bioceramic scaffolds used for orthopaedic tissue engineering and how these factors may influence bone regeneration. The second part of this thesis is a study of the effects of bone microarchitecture on the mechanical properties of the human proximal femur. Strategies for orthopaedic tissue engineering involve the use of a porous ceramic or polymer scaffold to serve as a template for bone regeneration. However, the design and engineering of these scaffolds is ad hoc. The effect of porosity, pore size, shape, interconnectivity, transport and mechanical properties on bone ingrowth is not well understood and remains a significant challenge to successful bone regeneration. We use a 3D micro-CT imaging and analysis approach to generate measures of local and non local pore size, pore interconnectivity, transport and mechanical properties directly from images of explanted hydroxyapatite constructs from a sheep model. We develop a method to accurately phase separate pore, bone and scaffold phases using a three-phase segmentation algorithm. We also observe a strong correlation with bone ingrowth andmeasures of non local pore size which account for pore accessibility. This study demonstrates the utility of micro-CT and quantitative 3D analysis to analyse tissue engineered implants. Osteoporosis and bone fracture at the hip are increasingly common with an aging population. Current methods to diagnose and treat osteoporosis are ambiguous about the role of bone microstructure in bone fragility. A micro-CT and 3D imaging approach on 13 proximal femora is implemented. We derive corrections to the standard Hip Structural Analysis assumptions of square and circular cross section at the femoral neck. A finite element method (FEM) is used to estimate the full anisotropic elastic stiffness tensor and correlations are noted with age, and structural parameters (such as topology and porosity). The strength of hips has been inferred via modulus-porosity relationships undertaken on trabeculae from within the femoral head and neck. We show that the modulus-porosity relationships at the whole hip scale differ significantly (by 100-200%) from relationships derived on trabecular subsets. Therefore, empirical relationships of modulus-porosity for trabeculae do not match data at the whole hip scale; a different empirical scaling and better fit is derived. Decreases in Young’s and shear moduli were observed with age while