The objective of this thesis is to develop efficient technologies for bone quality evaluation. The effort has been focused on three different aspects which are relevant to bone’s biomechanical functions.

Trabecular plates and rods are important microarchitectural features in determining the mechanical properties of trabecular bone. Based on digital topological analysis (DTA), a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Based on the direct measurement of each individual trabecula, a set of individual trabeculae segmentation (ITS) based morphological parameters, which characterize the properties of trabecular plates and rods separately, was derived and compared with the standard morphological parameters. The results suggested that the ITS-based morphological analyses provide a more comprehensive characterization of the trabecular morphology and orientation. Assisted by the ITS technique, the contributions of the microarchitecture, trabecular types and orientations to the mechanical properties of trabecular bone were examined quantitatively. First, it was demonstrated that the microarchitecture alone affects the elastic moduli of trabecular bone. It was also suggested that trabecular plates dominate the apparent elastic moduli and yield strength. However, under the axial compression, the local yielding initiates at trabecular rod under small strains and the accumulation of the damage within the yielded rods is much faster than that of the plate. analysis (DTA), a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Based on the direct measurement of each individual trabecula, a set of individual trabeculae segmentation (ITS) based morphological parameters, which characterize the properties of trabecular plates and rods separately, was derived and compared with the standard morphological parameters. The results suggested that the ITS-based morphological analyses provide a more comprehensive characterization of the trabecular morphology and orientation. Assisted by the ITS technique, the contributions of the microarchitecture, trabecular types and orientations to the mechanical properties of trabecular bone were examined quantitatively. First, it was demonstrated that the microarchitecture alone affects the elastic moduli of trabecular bone. It was also suggested that trabecular plates dominate the apparent elastic moduli and yield strength. However, under the axial compression, the local yielding initiates at trabecular rod under small strains and the accumulation of the damage within the yielded rods is much faster than that of the plate. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.In addition, the results suggested that the axial loading of trabecular bone is mainly sustained by the axially aligned volume. Consistent with this finding, we found that the transverse trabecular rods have the most significant contributions to the in-plane mechanical properties when compared to the longitudinal and oblique rods.

Based on the ITS technique, further image analysis was developed to substitute a 2-node beam or 3-node shell element with associated diameter or thickness for each individual trabecular plate and rod. The simplified plate-rod (P-R) microstructural model of each image was implemented in a finite element (FE) software (Abaqus, RI) and subjected to both linear elastic and nonlinear analysis to derive the axial elastic moduli and yield strength. Both the apparent moduli and yield strength predicted by the P-R model are consistent with those predicted by the traditional voxel model. The conversion of voxel based FE model to the P-R microstructural FE model can result in a 30-fold reduction of model size, 1000-fold reduction of CPU time for linear analysis, and 12000- fold reduction of CPU time for the nonlinear analysis.

A realistic bone remodeling simulation was developed to model the dynamic osteoclast resorption and coupled osteoblast formation process on 3D fiCT images of trabecular bone. Microscopic bone loss mechanisms:​ perforation, disconnection and isolated fragment, were modeled based on the DTA technique. With all the physiological parameters such as activation frequency and 3D morphology of resorption cavity strictly based on the bone biopsy measurements, this simulation successfully predicted the menopausal bone loss in spine and femoral neck (FN). A transition from trabecular plate to rod was identified by the ITS-based morphological analyses. Furthermore, the plate perforation was indicated as the primary cause of menopausal bone loss.