Clinical and Molecular Osteoporosis Research Unit, Department of Orthopaedics and Clinical Sciences, Lund University, Skane University Hospital, SE-205 02, Malmo, Sweden.
BMC Musculoskelet Disord. 2019 Sep 4;20(1):404. doi: 10.1186/s12891-019-2785-8.
Areal bone mineral density (aBMD) estimated by dual-energy X-ray absorptiometry (DXA) is used to estimate peak bone mass, define osteoporosis and predict fracture. However, as aBMD is calculated as bone mineral content (BMC) divided by the scanned area, aBMD displays an inverse relationship with bone size. In a skeleton that is increasing in size, this is a problem, as bone size is an independent factor that determines bone strength. It could therefore be questioned whether peak aBMD is the period with greatest bone strength, a period that in the hip then would occur in ages 16-19. The aim of this study was to evaluate whether there are changes in bone size in men after age 18 that may influence peak bone strength. Another aim was to provide updated normative DXA data.
We scanned left femoral neck by DXA in a cross-sectional study with a population-based selection of 1052 men aged 18-28, and then registered bone mineral content (BMC, gram), aBMD (gram/cm) and bone area (cm) in each one-year age group. We performed analyses of variance (ANOVA) to evaluate whether there were differences in these traits between the age groups. We then used Pearson's correlation analyses to test for trends with ageing after peak bone mass was reached.
We found the highest absolute femoral neck aBMD at age 19, with statistically significant differences between the one-year age groups in BMC, aBMD, and bone area (all p < 0.05). From peak bone mass onwards (n = 962), there are negative correlations between age and BMC (r = - 0.07; p < 0.05) and age and aBMD (r = - 0.12; p < 0.001), and positive correlation between age and bone area (r = 0.06; p < 0.05).
As femoral neck bone size in young adult men becomes larger after peak bone mass, it could be questioned whether DXA estimated peak aBMD correlates with peak bone strength. We infer that aBMD must be interpreted with care in individuals with a growing skeleton, since skeletal strength may then increase, in spite of decreasing aBMD. This should be taken into account when performing DXA measurements in these ages.
双能 X 射线吸收法（DXA）估计的骨矿物质密度（aBMD）用于估计峰值骨量、定义骨质疏松症和预测骨折。然而，由于 aBMD 是骨矿物质含量（BMC）除以扫描面积计算得出的，因此它与骨大小呈反比关系。在骨骼不断增大的情况下，这是一个问题，因为骨大小是决定骨强度的独立因素。因此，有人质疑峰值 aBMD 是否是骨强度最大的时期，在髋关节中，这个时期会出现在 16-19 岁。本研究旨在评估 18 岁后男性的骨骼大小是否发生变化，这些变化可能会影响峰值骨强度。另一个目的是提供更新的 DXA 正常参考值数据。
我们对 1052 名年龄在 18-28 岁的男性进行了基于人群的横断面研究，使用 DXA 扫描左侧股骨颈，并在每个年龄组中记录骨矿物质含量（克）、aBMD（克/厘米）和骨面积（厘米）。我们进行方差分析（ANOVA）以评估这些特征在年龄组之间是否存在差异。然后，我们使用 Pearson 相关分析来测试达到峰值骨量后与年龄的趋势。
我们发现 19 岁时股骨颈的绝对 aBMD 最高，BMC、aBMD 和骨面积在各年龄组之间存在统计学显著差异（均 p<0.05）。从峰值骨量开始（n=962），年龄与 BMC（r=-0.07；p<0.05）和年龄与 aBMD（r=-0.12；p<0.001）之间呈负相关，而年龄与骨面积（r=0.06；p<0.05）之间呈正相关。
由于年轻成年男性的股骨颈骨大小在达到峰值骨量后会增大，因此 DXA 估计的峰值 aBMD 是否与峰值骨强度相关值得质疑。我们推断，在骨骼生长的个体中，必须谨慎解读 aBMD，因为尽管 aBMD 下降，骨骼强度可能会增加。在这些年龄段进行 DXA 测量时，应该考虑到这一点。
