Department of Anatomy and Anthropology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.
Curr Osteoporos Rep. 2011 Dec;9(4):177-83. doi: 10.1007/s11914-011-0072-1.
The age-related reduction in bone mass is disproportionally related to skeletal weakening, suggesting that microarchitectural changes are also important determinants of bone quality. The study of cortical and trabecular microstructure, which for many years was mainly based on two-dimensional histologic and scanning electron microscopy imaging, gained a tremendous momentum in the last decade and a half, due to the introduction of microcomputed tomography (μCT). This technology provides highly accurate qualitative and quantitative analyses based on three-dimensional images at micrometer resolution, which combined with finite elemental analysis predicts the biomechanical implications of microstructural changes. Global μCT analyses of trabecular bone have repeatedly suggested that the main age-related change in this compartment is a decrease in trabecular number with unaltered, or even increased, trabecular thickness. However, we show here that this may result from a bias whereby thick trabeculae near the cortex and the early clearance of thin struts mask authentic trabecular thinning. The main cortical age-related change is increased porosity due to negatively balanced osteonal remodeling and expansion of Haversian canals, which occasionally merge with endosteal and periosteal resorption bays, thus leading to rapid cortical thinning and cortical weakening. The recent emergence of CT systems with submicrometer resolution provides novel information on the age-related decrease in osteocyte lacunar density and related micropetrosis, the result of lacunar hypermineralization. Last but not least, the use of the submicrometer CT systems confirmed the occurrence of microcracks in the skeletal mineralized matrix and vastly advanced their morphologic characterization and mode of initiation and propagation.
与骨骼弱化不成比例的是，与年龄相关的骨量减少表明微观结构变化也是骨质量的重要决定因素。皮质和小梁微观结构的研究多年来主要基于二维组织学和扫描电子显微镜成像，由于引入了微计算机断层扫描（μCT），在过去的十五年中取得了巨大的进展。该技术基于具有微米分辨率的三维图像提供高度准确的定性和定量分析，结合有限元分析预测微观结构变化的生物力学影响。对小梁骨的全局 μCT 分析反复表明，该部位与年龄相关的主要变化是小梁数量减少，而小梁厚度不变，甚至增加。然而，我们在这里表明，这可能是由于一种偏差造成的，即皮质附近的厚小梁和早期清除的薄支柱掩盖了真实的小梁变薄。主要的皮质与年龄相关的变化是由于骨单位的负平衡重塑和哈弗斯管的扩张导致的孔隙率增加，哈弗斯管偶尔会与内皮质和骨膜吸收凹坑合并，从而导致皮质快速变薄和皮质弱化。具有亚微米分辨率的 CT 系统的最新出现提供了有关骨细胞腔隙密度和相关微矿化的与年龄相关的减少的新信息，这是腔隙过度矿化的结果。最后但同样重要的是，亚微米 CT 系统的使用证实了骨骼矿化基质中微裂缝的发生，并大大推进了它们的形态特征及其起始和传播模式。
