Microscopic analysis of three-dimensional trabecular structure using X-ray and syncrotron radiation

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1) There are two different types of anti-osteoporotic agents ; anti-resorptive agent and bone-formative agent. The effect of the former agent was shown to preserve trabecular connectivity, while that of the latter was to thicken trabeculae in the ovariectomized rats.2) According to the meta-analysis from several clinical trials of antiresorptive agents looking at the relative risk of vertebral fractures against the average change in bone mineral density (BMD) for each trial, most of the effect of treatment was explained by an 8% increase in spinal BMD, which produced a 41% risk reduction. However, there is no proofs nor explanations. Finite element analysis (FEA) demonstrated that this effect of anti-resorptive agent to preserve connectivity seemed to increase bone strength with small increase in BMD.3) Our micro-FEA system was validated to assess the mechanical properties of bone, including the individual properties of the spongiosa and cortex, in the osteoporotic rat model. We found that the mechanical property of each component had a significant relationship with the respective bone mass, volume or structure. While trabecular microstructure has a significant relationship with bone strength, in the OVX bone with deteriorated trabecular microstructure, the strength mainly depended on the cortical component.4) SR-CT seems to be a useful tool for delineating trabecular surfaces, evaluating bone mineralization, and for revealing precise trabecular structure. We could visualize and quantify the calcium density using the different mass attenuation coefficients depending on energy between calcium and carbon. We calculated the calcium density according to the formula : CT value= mca/ro x rca+mc/ro x rc