Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
J Neurosurg Spine. 2010 Jun;12(6):602-12. doi: 10.3171/2009.12.SPINE09543.
Effective methods for fixation of the axis include C1-2 transarticular and C-2 pedicle screw placement. Both techniques pose a risk of vertebral artery (VA) injury in patients with narrow pedicles or an enlarged, high-riding VA. Pars screws at C-2 avoid the pedicle, but can cause VA injury with excessively long screws. Therefore, the authors evaluated various entry points and trajectories to determine ideal pars screw lengths that avoid breaching the transverse foramen.
Both pars were studied on 50 CT scans (100 total). Various pars lengths were assessed using 2 entry points and 3 trajectories (6 measurements). Entry point A was the superior one-fourth of the lateral mass. Entry point B was 3-mm rostral to the inferior aspect of the lateral mass. Using entry points A and B, Trajectory 1 was the minimum distance to the transverse foramen; Trajectory 2 was the maximum distance to the transverse foramen; and Trajectory 3 was the steepest angle to the pars/C-2 superior facet junction without transverse foramen breach.
The mean patient age was 46 +/- 17 years, and 84% of the CT scans reviewed were obtained in men. There was no significant difference in right or left measurements. Entry point B demonstrated greater pars lengths for each trajectory compared with entry point A (p < 0.0001). For both entry points, Trajectory 3 provided the greatest pars length. Using Trajectory 3 with entry point B, 84, 95, and 99% had a pars length that measured >or= 18, 16, and 14 mm, respectively. Using Trajectory 3 with Entry point A, only 41, 64, and 87% had a pars length that measured >or= 18, 16, and 14 mm, respectively.
Using an entry point 3-mm rostral to the inferior edge of the lateral mass and a trajectory directed toward the superior facet/pars junction, 99% of partes interarticularis in this study would tolerate a 14-mm screw without breach of the transverse foramen.
颈椎关节突螺钉固定技术是颈椎后路固定的有效方法，包括 C1-2 经关节突螺钉固定和 C-2 椎弓根螺钉固定。这两种技术都有损伤椎动脉（VA）的风险，尤其是在椎弓根狭窄或椎动脉高位、增粗的患者中。C2 侧块螺钉避开了椎弓根，但过长的螺钉可能会导致 VA 损伤。因此，作者评估了各种进钉点和进钉轨迹，以确定理想的侧块螺钉长度，避免横突孔穿透。
在 50 例 CT 扫描（共 100 例）上研究了双侧侧块。使用 2 个进钉点和 3 个进钉轨迹（共 6 个测量值）评估了不同的侧块长度。进钉点 A 为侧块外侧缘的上 1/4。进钉点 B 位于侧块下缘 3mm 处。使用进钉点 A 和 B，轨迹 1 为距离横突孔最近的距离；轨迹 2 为距离横突孔最远的距离；轨迹 3 为与侧块/C2 上关节突交界处成最大角度而不穿透横突孔。
患者的平均年龄为 46±17 岁，84%的 CT 扫描为男性。左右测量值无显著差异。与进钉点 A 相比，进钉点 B 各轨迹的侧块长度均较大（p<0.0001）。对于两个进钉点，轨迹 3 提供了最大的侧块长度。使用进钉点 B 和轨迹 3，84%、95%和 99%的侧块长度测量值>或=18、16 和 14mm，分别。使用进钉点 A 和轨迹 3，只有 41%、64%和 87%的侧块长度测量值>或=18、16 和 14mm，分别。
使用进钉点位于侧块下缘 3mm 上方，进钉轨迹朝向关节突/侧块交界处，99%的研究中的颈椎关节突在不穿透横突孔的情况下可容纳 14mm 的螺钉。
