Objectives: Femoral neck fracture is the most serious osteoporotic fractures that is responsible for high medical costs and high mortality. Femoral neck geometric parameters (FNGPs) are important parameters that reflect the geometrical characteristics of femoral neck, and are closely related to the strength of femoral neck and the risk of fragility fracture.There are differences in the incidence of femoral neck fractures among races. However, whether there is difference in FNGPs among races is unknown.Therefore, this study aims to compare the differences in FNGPs between Chinese and Japanese females.
Methods: This study was a cross-sectional study, in which 3 859 healthy females aged 10-86 (45.7±17.1) years old were recruited from Changsha City of Hunan Province and surrounding areas. The weight and height were measured and recorded, and the body mass index (BMI) was calculated. A dual energy X-ray absorptiometry (DXA) bone densitometer was used to measure femoral neck projective bone area (BA) and bone mineral density (BMD). FNGPs were calculated using the BMD and BA, which included the outer diameter (OD), cross-sectional area (CSA), cortical thickness (CT), endocortical diameter (ED), buckling ratio (BR), section modulus (SM), cross-sectional moment of inertia (CSMI), and compression strength index (CSI). The data of FNGPs in Japanese females was collected from literature. These subjects were grouped by 10-year age. The mean and standard deviation of height, weight, BMI, femoral neck BMD, and FNGPs of each group were calculated. The model with the best goodness-of-fit was selected from various mathematical regression models to analyze the distribution trend and the best fitting curve of FNGPs with age. The differences in FNGPs between Chinese and Japanese females were analyzed by using age-corresponding mean fitting curve for paired t-test, and the relative change rates of FNGPs were compared.
Results: The mean values of FNGPs were significantly different among different years old healthy females (all P<0.01). The mean values of OD, CSA, CT, SM, and CSMI in femoral neck were high at 30 to 39 years old, and then they were gradually decreased with age. The CSI reached its peak at 20-29 years old, and it was decreased gradually after 30 years old. ED and BR were at a low level before 40 years old, they were gradually increased after 40 years old, and reached the maximum average value at 80-86 years old. The variations in FNGPs with age were fitted with the best goodness-of-fit by applying the cubic regression model and the determination coefficients of regression equations (R2: 0.062-0.404) were significant (all P<0.01). The distribution trend of FNGPs with age varied with the indices, among which CSA, CT, SM, CSMI and CSI were increased with age before 35 years old, and then they were decreased with age; BR was at a low level in the early stage, and then it was increased with age after about 40 years. There were significant differences in the fitting curves of FNGPs related to age between Chinese and Japanese females (all P<0.01). The fitting curves of OD, ED, BR and SM in Chinese females were significantly higher than those in Japanese females (all P<0.01), while those of CSA and CT in Chinese females were significantly lower than those in Japanese females (all P<0.01). Before the age of 50, the curves of CSMI and CSI of Chinese females were significantly higher than those of Japanese females (all P<0.01), while after the age of 60 the situation was reversed (all P<0.01). Except for SM and CSI, there were significant differences in the rate of OD, CSA, CT, ED, BR and CSMI with age (all P<0.01). By the age of 80 years old, the rates of change in OD, ED, and BR with the age in Chinese females were increased by 0.91%,3.94%, and 47.5%, respectively, while those in Japanese females were increased by 8.57%, 15.8% and 85.3%, respectively；the rates of change of CSA, CT, and CSMI with the age in Chinese females were declined 28.0%, 29.6%, and 25.2%, respectively, while those in Japanese females were declined 29.9%, 36.2%, and 10.9%, respectively. There were significant difference in the rates of change in FNGPs with the age between Chinese and Japanese females (all P<0.01).
Conclusions: The study reveals the variation of FNGPs with age in Chinese, and confirms that there are racial differences in FNGPs between Chinese and Japanese females, which may be one of the important reasons for the difference in the incidence of femoral neck fracture between Chinese and Japanese females.
目的: 股骨颈脆性骨折是后果最严重、医疗花费最高和病死率最高的骨质疏松性骨折类型。股骨颈几何参数(femoral neck geometric parameters，FNGPs)是反映股骨颈几何学特征的重要参数，与股骨颈强度和脆性骨折风险密切相关。股骨颈脆性骨折的发病率存在明显的种族差异，但FNGPs是否有种族差异尚未明确。本研究旨在比较中国女性与日本女性FNGPs的差异。方法: 本研究为横断面研究，从湖南省长沙市及周边地区招募女性健康志愿者3 859名，年龄为10.0~86.0(45.7±17.1)岁。测量并记录研究对象的体重、身高，并计算其体重指数(body mass index，BMI)，采用双能X线骨密度测量仪测量研究对象的股骨颈投射骨面积(bone area, BA)和股骨颈骨密度(bone mineral density，BMD)。采用BA和/或BMD计算各种FNGPs，包括股骨颈轴长中点的外周直径(outer diameter，OD)、横截面积(cross-sectional area，CSA)、平均皮质厚度(cortical thickness，CT)、内皮质直径(endocortical diameter，ED)、抗曲比率(buckling ratio，BR)、截面系数(section modulus，SM)、截面转动惯量(cross-sectional moment of inertia，CSMI)和抗压强度指数(compressive strength index，CSI)。日本女性FNGPs的数据来自相关的文献。研究对象年龄按10年分组，分别计算各组的身高、体重、BMI、股骨颈BMD和各种FNGPs的平均值及标准差。从各种数学回归模型中选择拟合优度最佳的模型，分析各种FNGPs随年龄的分布趋势及最佳拟合曲线。对于中国女性和日本女性的各种FNGPs的差异采用各组年龄相应的平均值拟合曲线进行配对t检验，并比较其相对变化率。结果: 不同年龄的志愿者之间各种FNGPs的均数差异均有统计学意义(均P<0.01)。在30~39岁的志愿者中，股骨颈的CSA、CT、SM和CSMI的均数处于较高水平，之后这些指标随着年龄增大而逐渐下降；CSI的峰值年龄最小为20~29岁，30岁之后随年龄增大而逐渐下降；ED和BR在40岁之前处于较低水平，40岁之后呈逐渐增加趋势，最大平均值出现在80~86岁。各种FNGPs与年龄的变化关系均采用3次回归模型拟合优度最佳，回归方程的决定系数(R2：0.062~0.404)均有统计学意义(均P<0.01)。它们的散点分布趋势随指标而异，其中CSA、CT、SM、CSMI和CSI在35岁之前随年龄增大而增加，之后随年龄增大而减少；只有BR在40岁之前处于较低水平，之后则随着年龄增大而增加。中国女性与日本女性年龄相关的FNGPs的拟合曲线差异均存在统计学意义(均P<0.01)，中国女性OD、ED、BR和SM的拟合曲线显著高于日本女性(均P<0.01)，CSA和CT则显著低于日本女性(均P<0.01)。在50岁之前，中国女性的CSMI和CSI拟合曲线显著高于日本女性(均P<0.01)，在60岁之后则显著低于日本女性(均P<0.01)。除SM和CSI外，中国女性与日本女性之间其余的FNGPs(包括OD、CSA、CT、ED、BR和CSMI)随着年龄增大其变化率差异均有统计学意义(均P<0.01)。到80岁时，中国女性OD、ED和BR的变化率分别增加0.91%、3.94%和47.5%，日本女性分别增加8.57%、15.8%和85.3%；中国女性CSA、CT和CSMI的变化率分别下降28.0%、29.6%和25.2%，日本女性分别下降29.9%、36.2%和10.9%，两者之间差异均有统计学意义(均P<0.01)。结论: 本研究揭示了中国女性FNGPs随年龄变化的规律，并证实中国女性与日本女性的FNGPs存在种族差异，这种差异可能是导致中国女性与日本女性股骨颈骨折发病率存在差异的重要原因之一。.
Keywords: bone densitometry; female population; femoral neck geometric parameters; race difference.