Spinal Surgery Department, The First Affiliated Hospital of Fujian Medical University, Quanzhou Orthopedic-Traumatological Hospital of Fujian Traditional Chinese Medicine University, Fuzhou, Fujian, China.
Spinal Surgery Department, Quanzhou Orthopedic-Traumatological Hospital of Fujian Traditional Chinese Medicine University, Quanzhou, Fujian, China.
J Orthop Surg Res. 2020 Apr 7;15(1):131. doi: 10.1186/s13018-020-01639-0.
T1s, C2-7 lordosis, and C2-7 sagittal vertical axis (SVA) are the three most important sagittal parameters in the cervical spine. This study was conducted to investigate the relationships between classical sagittal alignment parameters and a new parameter, K-line tilt, and to study the impact of K-line tilt.
A total of 72 patients who underwent adjacent two-level anterior cervical discectomy and fusion (ACDF) were retrospectively analyzed. Radiographic measurements included T1 slope (T1s), C2-7 lordosis, segment angle (SA), C2-7 SVA, and K-line tilt. The Neck Disability Index (NDI) scores were used to evaluate the clinical prognosis. Pearson correlation coefficients were calculated between radiographic measures. Linear regression analysis was used to analyze the relationship between follow-up K-line tilt and NDI.
ΔNDI was positively correlated with ΔT1s (r = 0.620, p < 0.05), ΔC2-7 SVA (r = 0.645, p < 0.05), and ΔK-line tilt (r = 0.702, p < 0.01); ΔK-line tilt was positively correlated with ΔT1s (r = 0.650, p < 0.05), ΔSA (r = 0.269, p < 0.05), and ΔC2-7 SVA (r = 0.293, p < 0.05); ΔT1s was positively correlated with ΔC2-7 lordosis (r = 0.428, p < 0.05), ΔSA (r = 0.631, p < 0.01), and ΔC2-7 SVA (r = 0.235, p < 0.05); ΔC2-7 lordosis was positively correlated with ΔSA (r = 0.666, p < 0.05) and negatively correlated with ΔC2-7 SVA (r = - 0.467, p < 0.01). The preoperative and postoperative K-line tilt values were statistically significant (p < 0.01), increasing from (7.50 ± 6.48)° to (9.95 ± 5.09)°. Preoperative NDI was positively correlated with preoperative C2-7 SVA (r = 0.639, p = 0.011) and K-line tilt (r = 0.516, p = 0.026); follow-up NDI was positively correlated with follow-up T1s (r = 0.664, p = 0.038), C2-7 SVA (r = 0.756, p = 0.004), and K-line tilt (r = 0.832, p = 0.006). The linear regression model showed that when the follow-up K-lint tilt was > 23.75°, NDI scores were > 25 (R = 0.737, p = 0.000).
This study showed that the K-line tilt was strongly correlated with the C2-C7 SVA, indicating that the K-line tilt can be used as another cervical parameter to evaluate cervical alignment in adjacent two-level ACDF. K-line tilt is an important parameter similar to the classical parameter C2-C7 SVA. In particular, a K-line tilt greater than 23.75 corresponded to a worse clinical prognosis, which was defined as an NDI score greater than 25.
T1 倾斜角、C2-7 矢状位曲度和 C2-7 矢状垂直轴（SVA）是颈椎最重要的三个矢状位参数。本研究旨在探讨经典矢状位参数与新参数 K 线倾斜角之间的关系，并研究 K 线倾斜角的影响。
回顾性分析了 72 例行相邻两节段颈椎前路椎间盘切除融合术（ACDF）的患者。影像学测量包括 T1 倾斜角（T1s）、C2-7 矢状位曲度、节段角（SA）、C2-7 SVA 和 K 线倾斜角。使用颈痛残疾指数（NDI）评分评估临床预后。计算影像学测量值之间的 Pearson 相关系数。采用线性回归分析探讨随访 K 线倾斜角与 NDI 的关系。
ΔNDI 与 ΔT1s（r = 0.620，p < 0.05）、ΔC2-7 SVA（r = 0.645，p < 0.05）和 ΔK 线倾斜角（r = 0.702，p < 0.01）呈正相关；ΔK 线倾斜角与 ΔT1s（r = 0.650，p < 0.05）、ΔSA（r = 0.269，p < 0.05）和 ΔC2-7 SVA（r = 0.293，p < 0.05）呈正相关；ΔT1s 与 ΔC2-7 矢状位曲度（r = 0.428，p < 0.05）、ΔSA（r = 0.631，p < 0.01）和 ΔC2-7 SVA（r = 0.235，p < 0.05）呈正相关；ΔC2-7 矢状位曲度与 ΔSA（r = 0.666，p < 0.05）呈正相关，与 ΔC2-7 SVA（r = - 0.467，p < 0.01）呈负相关。术前和术后 K 线倾斜角值有统计学意义（p < 0.01），从（7.50 ± 6.48）°增加到（9.95 ± 5.09）°。术前 NDI 与术前 C2-7 SVA（r = 0.639，p = 0.011）和 K 线倾斜角（r = 0.516，p = 0.026）呈正相关；随访 NDI 与随访 T1s（r = 0.664，p = 0.038）、C2-7 SVA（r = 0.756，p = 0.004）和 K 线倾斜角（r = 0.832，p = 0.006）呈正相关。线性回归模型显示，当随访 K 线倾斜角 > 23.75°时，NDI 评分> 25（R = 0.737，p = 0.000）。
本研究表明，K 线倾斜角与 C2-C7 SVA 密切相关，提示 K 线倾斜角可作为评估相邻两节段 ACDF 颈椎矢状位的另一个参数。K 线倾斜角是与经典参数 C2-C7 SVA 相似的重要参数。特别是，K 线倾斜角大于 23.75°对应于更差的临床预后，定义为 NDI 评分大于 25。
