Race differences in hip strength, density and geometry

描述(来自申请人的逐字描述)：在临床环境中，面积骨 双X射线骨密度仪(DXA)测量骨密度 为股骨近端提供替代测量的髋部骨折风险 力量。由于DXA是一种平面成像方式，它具有潜在的 重要的局限性。首先，DXA量化了整体骨量和密度， 而皮质和小梁区对机械性能的影响 强度可能超过它们对整体骨量的贡献。第二，DXA 骨密度测量结果与骨骼大小成正比；骨骼越大，密度越大。这个 我们研究的总体目标是了解DXA的投射性质 成像影响其描述股骨近端力量的能力 髋部骨折发生率、体积BMID、骨骼存在已知差异的人群 大小和皮质厚度。为了达到这一目标，我们将在 活体比较股骨近端的强度、间隔部骨密度和几何形状 400名高加索和非洲裔老年妇女。为了估计股骨的强度， 我们将用体积定量计算机断层扫描对受试者进行成像。 (VQCT)建立有限元(FE)模型。 VQCT扫描。我们将通过加载来计算股骨近端失效载荷(FL 这些模型通过力来模拟坠落到一侧的冲击力而失败 大粗隆后外侧与关节反应 模拟自发性骨折的力。为了确定这一关系 在这两个种族组的DXA骨密度和FL之间，我们将获得DXA髋部扫描 在所有的科目中。确定FL、房间隔的关系 BMD和三维骨几何，我们将用计算机分析vQCT扫描 算法，该算法提取骨小梁/皮质骨密度和 横截面几何图形。通过确定三维几何和/或BMD因素 从而提高股骨近端的强度，并了解如何 这些措施被修改为平面投影，我们将获得相当大的收益 洞察DXA的性能，这是用于估计的主要技术 股骨近端的力量，因此，髋部骨折的风险。

DESCRIPTION (Verbatim from the Applicant): In the clinical setting, areal bone mineral density (BMD) measurements by dual x-ray absorptiometry (DXA) estimate hip fracture risk by providing a surrogate measure for proximal femoral strength. Because DXA is a planar imaging modality, it has potentially important limitations. First, DXA quantifies integral bone mass and density, whereas the influence of the cortical and trabecular compartments on mechanical strength may exceed their contributions to the integral bone mass. Second, DXA BMD measurements scale with bone size; larger bones appear to be denser. The overall goal of our study is to understand how the projectional nature of DXA imaging affects its ability to depict proximal femoral strength in two populations with known differences in hip fracture rates, volumetric BMID, bone size and cortical thickness. To achieve this goal, we will carry out a study in vivo comparing proximal femoral strength, compartmental BMD and geometry in 400 elderly Caucasian and African-American women. To estimate femoral strength, we will image the subjects with volumetric quantitative computed tomography (vQCT) of the proximal femur and construct finite element (FE) models using the vQCT scans. We will calculate proximal femoral failure load (FL) by loading these models to failure with forces simulating a fall to the side with impact on the posterolateral aspect of the greater trochanter and a joint reaction force simulating a spontaneous fracture. In order to determine the relationship between DXA BMD and FL in these two race groups, we will acquire DXA hip scans in all of the subjects. To determine the relationship between FL, compartmental BMD and 3-D bone geometry, we will analyze the vQCT scans with a computer algorithm, which extracts measures of trabecular/cortical BMD and cross-sectional geometry. By determining the 3-D geometric and/or BMD factors which result in greater proximal femoral bone strength and understanding how these measures are modified by planar projection, we will gain considerable insight into the performance of DXA, the principal technique used to estimate proximal femoral strength and therefore, hip fracture risk.