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， 双能X线骨密度仪（DXA）测量 通过提供股骨近端替代指标评估髋部骨折风险 实力由于DXA是一种平面成像模式， 重要的限制。首先，DXA量化整体骨量和密度， 而皮质和小梁间室对机械的影响 强度可能超过它们对整体骨量的贡献。第二，DXA BMD测量值与骨骼大小成比例;较大的骨骼似乎密度更大。的 我们研究的总体目标是了解DXA的投射性质 成像影响其描述两个股骨近端强度的能力 髋部骨折发生率、体积BMID、骨 大小和皮质厚度。为达致这个目标，我们会在 在体内比较股骨近端强度、间室BMD和几何结构， 400名老年白人和非裔美国女性。为了评估股骨强度， 我们将对受试者进行容积定量计算机断层扫描， （vQCT），并使用 vQCT扫描。我们将通过载荷计算股骨近端失效载荷（FL） 这些模型在力的作用下发生故障， 在大转子的后外侧和关节反应 模拟自然断裂的力为了确定 在这两个种族组中DXA BMD和FL之间，我们将获得DXA髋关节扫描 在所有的科目。为了确定FL、房室 BMD和3-D骨几何学，我们将用计算机分析vQCT扫描 算法，该算法提取骨小梁/皮质BMD的测量值， 横截面几何形状。通过确定三维几何和/或BMD因子， 这导致更大的股骨近端骨强度，并了解如何 这些措施是由平面投影修正，我们将获得可观的 深入了解DXA的性能，DXA是用于估计 股骨近端强度，因此，髋关节骨折风险。

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.