Objective: To explore the normal distribution of cervical sagittal alignment and the relationship between cervical alignment and global spine balance in asymptomatic young adults.
Methods: A cohort of 272 asymptomatic Chinese adults (including 161 males and 111 females, with an average age of (23.2±4.4) years, ranging from 18 to 45 years) were prospectively recruited from November 2011 to December 2014. The C0-C2 angle, disk angles from C2-C3 to C6-C7, vertebral angles from C3 to C7, T1 slope, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), C2-C7 sagittal vertical axis (C2-C7SVA), center of gravity of head to C7SVA (CGH-C7SVA), C7-S1SVA were measured and statistically analyzed. All the subjects were categorized with the Roussouly classification and the cervical morphologies were evaluated as lordotic, straight, sigmoid or kyphotic. Spinal sagittal alignment parameters were compared between different sexes and Roussouly classifications with independent student t test, analysis of variance (ANOVA) or Chi-square test. Correlations between cervical sagittal alignment and global spine sagittal alignment were calculated using the Pearson and Spearman correlation coefficient. Linear regression analysis was performed.
Results: Sixty-seven males and 59 females aged from 18 to 30 years old were included in the study. The mean value of C0-C7 was 26.0°±12.8°, composed of 15.2°±6.7° for C0-C2, 9.1°±12.1° for sum of disk angles from C2-C3 to C6-C7, and 1.4°±10.2° for sum of vertebral angles from C3 to C7. C2-C7SVA [(18.6±7.9) mm] and CGH-C7SVA [(22.9±12.3) mm]were offset ideally by C7-S1SVA [(-21.6±31.0) mm]. Males had a larger T1 slope (P < 0.05) and accordingly, a larger cervical lordosis C2-C7 (P < 0.01) and C0-C7 angle (P < 0.01) than females. Males had a smaller C7-S1SVA (P < 0.01) and accordingly, a smaller CGH-C7SVA (P=0.165) than females. Significant difference was found between cervical alignment of different Roussouly types (P < 0.01). In general, a larger LL was consistent with a set of larger TK, C2-C7angle, C0-C7 angle, and vice versa. There was no significant correlation between cervical morphology and the Roussouly classification (Chi-square=10.548, P=0.308). There was significant correlation between cervical alignment and T1 slope (P < 0.01), TK (P < 0.01). There was significant correlation between adjacent segmental angles from T1 slope up to C0-C2 angle (P < 0.05).
Conclusion: Normative values of each vertebral angle and disk angle were established. The cervical lordosis occurred mainly at C0-C2 and disk levels, which was influenced by parameters of other parts of the spine, such as T1 slope, TK and the Roussouly classification. There was significant correlation between adjacent disk angles.
目的: 探讨无症状中国年轻人颈椎矢状位曲度的正常值及其与全脊柱平衡的关系。
方法: 2011年11月—2014年12月招募并选择年龄18~30岁的志愿者行全脊柱侧位X线检查，在X线片上测量指标包括C0-C2角、从C2-C3到C6-C7的间盘角、从C3到C7的椎体角、T1倾斜角、胸椎后凸角(thoracic kyphosis, TK)、腰椎前凸角(lumbar lordosis, LL)、骨盆入射角(pelvic incidence, PI)、骶骨倾斜角(sacral slope, SS)、C2-C7矢状轴向垂线(C2-C7 sagittal vertical axis, C2-C7SVA)、头重心至C7的矢状位轴向垂线(center of gravity of head to C7SVA, CGH-C7SVA)、C7到S1的矢状位轴向垂线(C7-S1SVA)。依据脊柱骨盆矢状位形态进行Roussouly分型，比较不同Roussouly分型下的颈椎曲度及形态。
结果: 共纳入126名志愿者参与研究，其中男性67名，女性59名，平均年龄(21.4±2.3)岁。C0-C7前凸角平均为26.0°±12.8°，其中C0-C2前凸角平均为15.2°±6.7°，C2-C3到C6-C7间盘前凸角总和平均为9.1°±12.1°，C3到C7的椎体前凸角总和平均仅为1.4°±10.2°。C2-C7SVA(18.6±7.9) mm和CGH-C7SVA[(22.9±12.3) mm]由C7-S1SVA[(-21.6±31.0) mm]完美代偿。不同的Roussouly分型间颈椎曲度差异有统计学意义(P < 0.01)。颈椎曲度与T1倾斜角(P < 0.01)、胸椎后凸角(P < 0.01)有显着相关性。从T1倾斜角到C0-C2角，相邻节段间盘角之间存在显著相关性(P < 0.05)。
结论: 测量并计算了无症状中国年轻人颈椎椎体角和间盘角的正常值，发现颈椎前凸主要发生在C0-C2和椎间盘水平，这些角度受到其他脊柱部位形态(T1倾斜角、胸椎后凸角和Roussouly分型)的影响，且相邻间盘角之间存在显著的相关性。
Keywords: Cervical spine; Disk angle; Global spine balance; Sagittal alignment; Vertebral angle.