Leonard Mary B, Shults Justine, Elliott Dawn M, Stallings Virginia A, Zemel Babette S
Department of Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Bone. 2004 Jun;34(6):1044-52. doi: 10.1016/j.bone.2003.12.003.
The assessment of bone health in children requires strategies to minimize the confounding effects of bone size on dual energy X-ray absorptiometry (DXA) areal bone mineral density (BMD) results. Cortical bone composes 80% of the total skeletal bone mass. The objective of this study was to develop analytic strategies for the assessment of whole body DXA that describe the biomechanical characteristics of cortical bone across a wide range of body sizes using peripheral quantitative computed tomography (pQCT) measures of cortical geometry, density (mg/mm(3)), and strength as the gold standard. Whole body DXA (Hologic QDR 4500) and pQCT (Stratec XCT-2000) of the tibia diaphysis were completed in 150 healthy children 6-21 years of age. To assess DXA and pQCT measures relative to age, body size, and bone size, gender-specific regression models were used to establish z scores for DXA bone mineral content (BMC) for age, areal BMD for age, bone area for height, bone area for lean mass, BMC for height, BMC for lean mass, and BMC for bone area; and for pQCT, bone cross-sectional area (CSA) for tibia length and bone strength (stress-strain index, SSI) for tibia length. DXA bone area for height and BMC for height were both strongly and positively associated with pQCT CSA for length and with SSI for length (all P < 0.0001), suggesting that decreases in DXA bone area for height or DXA BMC for height represent narrower bones with less resistance to bending. DXA BMC for age (P < 0.01) and areal BMD (P < 0.05) for age were moderately correlated with strength. Neither DXA bone area for lean mass nor BMC for lean mass correlated with pQCT CSA for length or SSI for length. DXA BMC for bone area was weakly associated with pQCT SSI for length, in females only. Therefore, normalizing whole body DXA bone area for height and BMC for height provided the best measures of bone dimensions and strength. DXA BMC normalized for bone area and lean mass were poor indicators of bone strength.
评估儿童骨骼健康需要采取策略，以尽量减少骨骼大小对双能X线吸收法（DXA）面积骨密度（BMD）结果的混杂影响。皮质骨占骨骼总质量的80%。本研究的目的是开发用于评估全身DXA的分析策略，该策略使用外周定量计算机断层扫描（pQCT）测量的皮质几何形状、密度（mg/mm³）和强度作为金标准，来描述不同体型儿童皮质骨的生物力学特征。对150名6至21岁的健康儿童进行了全身DXA（Hologic QDR 4500）和胫骨骨干的pQCT（Stratec XCT - 2000）检查。为了评估DXA和pQCT测量值与年龄、体型和骨骼大小的关系，使用了性别特异性回归模型来建立年龄的DXA骨矿物质含量（BMC）、年龄的面积BMD、身高的骨面积、瘦体重的骨面积、身高的BMC、瘦体重的BMC以及骨面积的BMC的z分数；对于pQCT，则建立胫骨长度的骨横截面积（CSA）和胫骨长度的骨强度（应力应变指数，SSI）的z分数。身高的DXA骨面积和身高的BMC与胫骨长度的pQCT CSA以及胫骨长度的SSI均呈强正相关（所有P < 0.0001），这表明身高的DXA骨面积或身高的DXA BMC降低代表骨骼变窄且抗弯能力降低。年龄的DXA BMC（P < 0.01）和年龄的面积BMD（P < 0.05）与强度呈中度相关。瘦体重的DXA骨面积和瘦体重的BMC与胫骨长度的pQCT CSA或胫骨长度的SSI均无相关性。仅在女性中，骨面积的DXA BMC与胫骨长度的pQCT SSI呈弱相关。因此，将全身DXA骨面积按身高进行标准化以及将BMC按身高进行标准化，能提供对骨骼尺寸和强度的最佳测量。按骨面积和瘦体重进行标准化的DXA BMC是骨强度的不良指标。
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