Purpose

To compare the Atlas (C1) lateral mass screw placement between screw trajectories of 0° and 15° medial angulation while using the intersection between lateral mass and inferomedial edge of the posterior arch.

Methods

Forty-eight Atlas lateral masses were prepared and divided into 2 groups: Group 1; screws inserted at 3 mm lateral to the reference point with screw trajectory of 0° angulation(N = 24) and Group 2; those inserted with screw trajectory of 15° medial angulation(N = 24). We evaluated the atlas anatomy, screw purchase and the presence of any breaches using CT scan.

Results

The radiographic parameters for Groups 1 and 2 were found statistically different (p-value < 0.05): bilateral intraosseous screw lengths (17.92 ± 1.47 mm. vs. 20.71 ± 2.4 mm.), bilateral screw length (29.92 ± 1.72 mm. vs. 33.13 ± 1.78 mm.), left screw medial angulation (x°) (0.67° ± 0.78° vs.14.17° ± 3.51°), right screw medial angulation (y°) (0.83° ± 1.03° vs.14.25° ± 2.53°) and bilateral screw medial angulation (0.75° ± 0.9° vs. 14.21° ± 2.99°). Twenty-two screws (91.67%) using the 0° medial angulation and nineteen screws (79.17%) using the 15° medial angulation had no cortical violations (Grade 0). However, two screws (8.33%) with 0° medial angulation and five screws (20.83%) with 15° medial angulation had breach less than 2 mm (Grade 1). There were no screws with breach between 2 and 4 mm (Grade 2) or greater than 4 mm. (Grade 3).

Conclusion

A starting point of 3-mm lateral to the intersection between lateral mass and inferomedial edge of the Atlas posterior arch can be safely and effectively used to insert C1 lateral mass using both 0° and 15° medial angulation.

中文翻译：

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Atlas (C1) 侧块螺钉放置使用侧块和后弓下内侧边缘之间的交叉点：尸体研究

目的

比较 Atlas (C1) 侧块螺钉在 0° 和 15° 内侧角度螺钉轨迹之间的放置，同时使用侧块和后弓下内侧边缘之间的交叉点。

方法

制备了 48 个阿特拉斯侧块，分为 2 组：第 1 组；第 1 组；第 1 组；第 在参考点外侧 3 mm 处插入螺钉，螺钉轨迹为 0° 角度（N  = 24）和第 2 组；以 15° 内侧角度的螺钉轨迹插入的那些（N  = 24）。我们使用 CT 扫描评估了寰椎解剖结构、螺钉购买和是否存在任何裂口。

结果

第 1 组和第 2 组的射线照相参数存在统计学差异（p值 < 0.05）：双侧骨内螺钉长度（17.92 ± 1.47 毫米对 20.71 ± 2.4 毫米），双侧螺钉长度（29.92 ± 1.72 毫米对33.13 ± 1.78 mm.), 左侧螺钉内侧角度 ( x °) (0.67° ± 0.78° vs.14.17° ± 3.51°), 右侧螺钉内侧角度 ( y°)（0.83° ± 1.03° 与 14.25° ± 2.53°）和双侧螺钉内侧角度（0.75° ± 0.9° 与 14.21° ± 2.99°）。使用 0° 内侧角度的 22 个螺钉 (91.67%) 和使用 15° 内侧角度的 19 个螺钉 (79.17%) 没有皮质侵犯（0 级）。然而，两个内侧角度为 0° 的螺钉 (8.33%) 和五个内侧角度为 15° 的螺钉 (20.83%) 的缺口小于 2 毫米（1 级）。没有螺钉的缺口在 2 到 4 毫米之间（2 级）或大于 4 毫米。（三年级）。

结论

使用 0° 和 15° 内侧角度，可以安全有效地使用距外侧块和阿特拉斯后弓下内侧边缘交叉点外侧 3 毫米的起点来插入 C1 侧块。