寰枢椎经关节螺钉联合寰椎椎弓根螺钉置钉的安全性研究

Safety of atlantoaxial transarticular screw combined with C1 pedicle screw fixation

目的探讨国人后路寰枢椎经关节螺钉联合寰椎椎弓根螺钉固定的置钉安全性。方法收集宁波市第六医院共48例结构完整的上颈椎CT数据,其中男26例,女22例;年龄26~58岁[(37.3±13.5)岁]。通过Mimics 19.0软件建模得到96侧联合固定模型并进行模拟置钉。首先在寰枢椎模型中建立寰椎垂直平面P1和寰椎水平平面P2,其次在C2下关节突中点向上3 mm、向外2 mm选择进钉点,并采用Margel法置入寰枢椎经关节螺钉S0,然后寰椎侧块中线与寰椎后弓下缘的交点上方3 mm作为寰椎椎弓根螺钉的进钉点,在该进钉点置入4枚直径3.5 mm的虚拟螺钉。置钉方法如下:S1为螺钉与S0的外侧或寰椎椎弓根内侧壁相切;S2为螺钉与寰椎椎弓根外壁相切;S3为螺钉与寰椎椎弓根上壁相切;S4为螺钉和寰椎椎弓根下壁相切。测量S1、S2与P1的夹角来确定外倾角,S3、S4与P2的夹角来确定头倾角;计算外倾角和头倾角的安全范围。测量S1、S2、S3、S4的进钉长度。在所有模型中,间隔2°调整外倾角和头倾角的进钉角度,计算每一个外倾角和头倾角的成功例数,并计算置钉成功率。结果所有寰枢椎模型置钉成功,外倾角最小值、最大值和安全范围分别为(-6.7±2.4)°、(10.4±4.3)°、(17.1±3.7)°;其头倾角的最小值、最大值和安全范围分别为(-3.6±1.0)°、(11.0±5.8)°、(14.6±4.6)°。4种寰椎椎弓根螺钉的进钉长度:S1(31.1±2.4)mm,S2(28.3±2.5)mm,S3(29.2±3.8)mm,S4(29.6±3.0)mm(P<0.05)。置钉外倾角为-1°~5°时置钉成功率为87.5%,其中2°外倾角置钉的成功率为100%,置钉头倾角为5°时可以达到93.8%的置钉成功率。结论后路寰枢椎经关节螺钉联合寰椎椎弓根螺钉置钉具有满意的置钉长度和较高的置钉成功率。

Objective To investigate the safety of posterior atlantoaxial transarticular screw combined with atlas pedicle screw fixation in Chinese.Methods CT data of upper cervical spine in 48 patients were collected from Ningbo No.6 Hospital,including 26 males and 22 females aged 26-58 years[(37.3±13.5)years].All CT data was transformed into 3D dimensional model and inserted with virtual screws by Mimics 19.0.Firstly,the vertical plane P1 and the horizontal plane P2 of the atlas were built in those atlantoaxial models,secondly the atlantoaxial transarticular screw S0 was inserted by Margel method,and it's insertion point was located at 3 mm lateral and 2 mm cephalad in the C2 inferior articular process.Finally,four atlas pedicle screws were inserted at the midline of atlas lateral mass.The four screws are inserted as follows.S1:the screw was tangent to the lateral side of the S0 or the medial of the atlas pedicle.S2:the screw was tangent to the lateral wall of the atlas pedicle.S3:the screw was tangent to the upper wall of the atlas pedicle.S4:the screw was tangent to the inferior wall of the atlas pedicle.The angles between S1,S2 and P1 as the camber angle,and the angle between S3,S4 and P2 as the gantry angle were measured.Then the safety range of camber angle and gantry angle were calculated,and the screw length of S1,S2,S3 and S4 was measured.In all models,the camber angle and gantry angle of the screws were adjusted an interval of 2°,the number of successful cases was calculated and the success rate of insertion was calculated.Results All 3D models were inserted successfully.The minimum value,maximum value and safety range of the camber angle of atlas pedicle screws were(-6.7±5.2)°,(10.4±4.3)°,(17.1±3.7)°,respectively;and of the gantry angle were(-0.5±3.5)°,(11.0±5.8)°,(11.5±4.9)°,respectively.The length of screw placement was S1:(31.1±2.4)mm,S2:(28.3±2.5)mm,S3:(29.2±3.8)mm,S4:(29.6±3.0)mm,respectively(P<0.05).When the camber angle was from-1°to 5°,the success rate of screw placement was 87.5%;when inserting with 2°camber angle,the success rate was 100%;when the gantry angle was 5°,the success rate was 93.8%.Conclusion The posterior atlantoaxial transarticular screw combined with atlas pedicle screw can achieve satisfy insertion length and success rate.