Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15203, USA.
Spine J. 2011 Jul;11(7):659-67. doi: 10.1016/j.spinee.2011.05.007.
Bone mineral density (BMD) measurements acquired from quantitative computed tomography scans have been shown to correlate with bone mechanical properties such as strength, stiffness, and yield load. There are currently no reports of BMD as a function of anatomic location within each vertebra.
The overall objective of this study was to characterize BMD in the cervical spine as a function of level and anatomic location.
Cervical spine BMD was evaluated in vivo using a clinically relevant age group.
Twenty-two subjects (13 women and 9 men) were included with an average age of 48 ± 7 years (range, 35-61 years). Ten subjects were recently diagnosed with cervical radiculopathy (age 49 ± 8 years; six women and four men; and two smokers and eight nonsmokers), and 12 subjects were asymptomatic controls (age 46 ± 6 years; seven women and five men; and three smokers, three quit smoking, and six nonsmokers).
Physiologic measures included overall BMD for C3-C7, average BMD within 11 anatomically defined regions of interest for each vertebra, and density distribution (by volume) within each anatomic region and vertebral level.
Subject-specific three-dimensional bone models were created from high-resolution computed tomography scans of the subaxial cervical spine (C3-C7). Custom software calculated the average BMD within 11 anatomically defined regions of interest for each three-dimensional bone model. Bone mineral density values for each voxel of bone tissue were binned into 50 mg/cc ranges to determine the density distribution by volume. Repeated-measures analysis of variance was used to test for differences within subjects by level (C3-C7) and anatomic location. The correlation between BMD in the central vertebral body and the pedicle and lateral mass regions was tested using Pearson correlation.
Average BMDs by level were 476, 503, 507, 473, and 414 mg/cm(3) for C3-C7, respectively. C3 and C6 BMDs were significantly less than those of C4 and C5 (p<.007). C7 BMD was significantly less than those of all other levels (all p<.001). Control and female subjects showed a trend toward higher BMD than radiculopathy and male subjects across all levels (p value: .06-.17). Wide variation in BMD was observed over anatomical regions, with the pedicles having significantly higher BMD than all other anatomic locations and the anterior portion of the central vertebral body having significantly lower BMD than all other anatomic locations. There was a significant positive correlation between central vertebral body BMD and lateral mass BMD at each level. Bone mineral density distribution by volume plots revealed women had a higher volume of very high-density bone than men but only in the posterior elements.
This study has characterized BMD in the cervical spine according to vertebral level and anatomic location within each vertebral level using live subjects from a clinically relevant age group. The results indicate significant differences in BMD according to vertebral level and among anatomical regions within each vertebra. The results suggest to the surgeon and device manufacturer that surgical procedures involving instrumentation attached to C7 may require a modification in instrumentation or in surgical technique to attain results equivalent to more superior levels. The results suggest to the basic scientist that computational models may be improved by taking into account the wide variation in BMD over different anatomical regions.
定量计算机断层扫描（quantitative computed tomography，QCT）获得的骨密度（bone mineral density，BMD）与骨力学性能（如强度、刚度和屈服载荷）相关。目前尚无关于每个椎体内部解剖位置的 BMD 报告。
本研究的总体目标是描述颈椎的 BMD 与水平和解剖位置的关系。
使用具有临床相关性的年龄组，对颈椎 BMD 进行了体内评估。
共纳入 22 例受试者（13 名女性和 9 名男性），平均年龄 48 ± 7 岁（范围，35-61 岁）。其中 10 例患者最近被诊断为颈椎病（年龄 49 ± 8 岁；6 名女性和 4 名男性；2 名吸烟者和 8 名不吸烟者），12 例为无症状对照者（年龄 46 ± 6 岁；7 名女性和 5 名男性；3 名吸烟者、3 名戒烟者和 6 名不吸烟者）。
生理测量包括 C3-C7 的总体 BMD、每个椎体 11 个解剖感兴趣区的平均 BMD，以及每个解剖区域和椎体水平的骨密度分布（按体积）。
使用颈椎下位轴（C3-C7）的高分辨率计算机断层扫描（CT），为每位受试者创建了特定的三维骨骼模型。定制软件计算了每个三维骨骼模型 11 个解剖感兴趣区的平均 BMD。通过将骨组织的每个体素的骨矿物质密度值分为 50mg/cc 范围，确定了按体积的密度分布。使用重复测量方差分析测试受试者内部的水平（C3-C7）和解剖位置的差异。使用 Pearson 相关性检验测试椎体中央体和椎弓根及侧块区域的 BMD 之间的相关性。
C3-C7 的平均 BMD 分别为 476、503、507、473 和 414mg/cm3。C3 和 C6 的 BMD 明显低于 C4 和 C5（p<.007）。C7 的 BMD 明显低于其他所有水平（均 p<.001）。控制组和女性受试者的 BMD 水平普遍高于颈椎病组和男性受试者（p 值：.06-.17）。在解剖区域之间观察到 BMD 存在广泛的差异，椎弓根的 BMD 明显高于所有其他解剖部位，椎体中央前部的 BMD 明显低于所有其他解剖部位。在每个水平，中央椎体 BMD 与侧块 BMD 之间存在显著的正相关。按体积绘制的骨矿物质密度分布图显示，女性的高密度骨体积明显高于男性，但仅在后部元素中如此。
这项研究使用来自具有临床相关性的年龄组的活体受试者，根据椎体水平和每个椎体水平内的解剖位置描述了颈椎的 BMD。结果表明，BMD 根据椎体水平和每个椎体内部的解剖区域存在显著差异。结果提示外科医生和器械制造商，涉及附着于 C7 的器械的手术可能需要修改器械或手术技术，以获得与更高级别相当的结果。结果提示基础科学家，计算模型可能会通过考虑不同解剖区域中 BMD 的广泛变化而得到改进。
