后路经寰枢关节螺钉固定术在儿童可行性的三维CT研究

The feasibility study of atlanto-axial transarticular fixation in children using multipanar reconstruction of helical computed tomography

目的了解影响儿童后路经寰枢关节螺钉安全置入的相关因素，提高手术的安全性。方法选取80名儿童的寰枢椎CT影像学资料，按年龄（Y）分为Y〈2岁组、2≤Y≤4岁组、4〈Y≤8岁组、8〈Y≤12岁组，每组各20名。三维重建后选取合适的轴性斜平面和双侧旁矢状斜平面，测量后路经寰枢关节螺钉固定的相关指标。结果（1）观察160侧所选取的旁矢状位斜平面CT影像，发现Ⅰ型椎动脉沟占76．25％、Ⅱ／型占6．25％、Ⅲ型占12．5％、Ⅳ型占5％。（2）不同年龄组间椎弓峡部宽度和高度有统计学意义（P〈0．05），理想螺钉路径到椎动脉的距离和置钉角度参数差异无统计学意义（P〉0．05）。（3）按设定标准1：椎弓峡部宽度、高度〉5mm，理想螺钉路径到椎动脉沟的距离〉2．5mm；标准2：椎弓峡部宽度、高度〉4．5mm，理想螺钉路径到椎动脉沟的距离〉2．5mm。Y〈2组儿童对于3．5mm螺钉一侧可置钉率分别为15％与40％；2≤Y≤4组为55％与85％；4〈Y≤8组为85％与95％；8〈Y≤12组为90％与90％。结论理想螺钉路径到椎动脉沟的距离能够更好地评估椎动脉沟变异对经寰枢关节螺钉固定术的影响。儿童进钉的合适内倾角和上倾角平均约为10°和40°。

Objective To investigate the factors that influence the appropriate placement of atlantoaxial transarticular screws in children. Methods 80 children were divided equally into 4 groups by the age （Y）： Y〈2, 2≤Y≤4, 4〈Y≤8 and 8〈Y≤ 12 respectively, and the 3D CT images of cervical spines were captured and analysed. Some parameters were measured in the appropriate oblique axial planes and oblique parasagittal planes by using 3D reconstruction of the image on CT workstation. Results （1） In the oblique parasagittal CT images, Type Ⅰ vertebral artery groove contributed to 76.25%, type Ⅱ contributed to 6.25%, type Ⅲ contributed to 12.5%, and type Ⅳ contributed to 5%. （2） There were significant differences in the bilateral isthmus width and height within different groups. However, no significant differences were found for the distance between optimal screw path and artery groove, and the same result for angular parameters. （3） The first criterion was that both the isthmus width and height were greater than 5 mm, while the distance between optimal screw path and vertebral artery groove was greater than 2.5 mm. The second criterion was that both isthmus width and height were greater than 4.5 mm, while the distance between optimal screw path and artery groove was greater than 2.5 mm. The acceptance rates of 3.5mm screws on at least one side in group Y〈2 was 15% and 40% respectively according to criteria 1 and 2. The rates in group 2≤Y≤4 were 55% and 85%, were 85% and 95% in group 4〈Y ≤8, and were 90% and 90% in group 8〈Y ≤ 12. Conclusion The distance between optimal screw path and vertebral artery groove can provide a better evaluation than vertebral artery groove variation alone for atlantoaxial transarticular screws fixation. The average medial angle and sagittal angle are about 10°and 40°respectively, and that can be used as reference values.