Nazarian Ara, Muller John, Zurakowski David, Müller Ralph, Snyder Brian D
Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA 02215, USA.
J Biomech. 2007;40(11):2573-9. doi: 10.1016/j.jbiomech.2006.11.022. Epub 2007 Jan 26.
With the prevalent use of DXA-measured BMD to assess pathologic hip fractures and its recently reported lack of reliability to predict fracture or account for efficacy of anti-resorptive therapy, it is reasonable to assess whether variations in the primary and secondary tensile and compressive trabecular microstructure can account for variations in proximal femur strength in comparison to DXA-measured BMD. To that end, microstructural and densitometric measures of trabecular bone specimens, from discrete sites within the proximal femur, were correlated with their mechanical properties. We hypothesize that accounting for regional variations in trabecular microstructure will improve predictions of proximal femur strength and stiffness compared to bone density measured by DXA. Forty-seven samples (seven donors) from seven distinct sites of human proximal femur underwent DXA and muCT imaging and mechanical testing. The results revealed significant variations in BMC, morphometric indices and mechanical properties within the proximal femur. This work has demonstrated that the mechanical performance of each sub-region is highly dependent on the corresponding trabecular microstructure. BMD measured by DXA at standard regions of interest cannot resolve the variations in trabecular density and microstructure that govern the mechanical behavior of the proximal femur. This work suggests that a quantitative Singh index that uses high resolution QCT to monitor the trabecular microstructure at specific sub-regions of the proximal femur may allow better predictions of hip fracture risk in individual patients and an improved assessment of changing bone structure in response to pharmacological interventions.
随着双能X线吸收法（DXA）测量的骨密度（BMD）被广泛用于评估病理性髋部骨折，且近期报道其在预测骨折或评估抗吸收治疗疗效方面缺乏可靠性，评估与DXA测量的BMD相比，股骨近端主要和次要拉伸及压缩小梁微结构的变化是否能解释股骨近端强度的变化是合理的。为此，对来自股骨近端离散部位的小梁骨标本的微结构和密度测量值与其力学性能进行了相关性分析。我们假设，与通过DXA测量的骨密度相比，考虑小梁微结构的区域差异将改善对股骨近端强度和刚度的预测。对来自人类股骨近端七个不同部位的47个样本（七个供体）进行了DXA、微观计算机断层扫描（muCT）成像和力学测试。结果显示股骨近端的骨矿含量（BMC）、形态学指标和力学性能存在显著差异。这项研究表明，每个子区域的力学性能高度依赖于相应的小梁微结构。在标准感兴趣区域通过DXA测量的BMD无法分辨控制股骨近端力学行为的小梁密度和微结构的变化。这项研究表明，使用高分辨率定量CT（QCT）监测股骨近端特定子区域小梁微结构的定量Singh指数可能有助于更好地预测个体患者的髋部骨折风险，并改善对药物干预后骨结构变化的评估。
