基于CT影像的下颈椎椎弓根钉道虚拟构建法

A novel technique of lower cervical pedicle screw placement controlled by virtual safe core of pedicle screw trajectory based on CT data

目的探讨基于CT影像的下颈椎椎弓根钉道虚拟构建法及其对提高置钉操作准确性的作用。方法收集60例成人颈椎疾病患者的C3,4椎体CT图像数据及标准颈椎正侧位X线片数据,男30例,女30例;年龄(55.42±10.38)岁(范围39~84岁)。导入Mimics 20.0软件,自行设计下颈椎钉道虚拟构建法进行钉道构建。记录虚拟椎弓根钉道及其安全核区的构建成功率;安全核区与椎体的空间位置关系:包括冠状面安全核区与上下钩椎关节外缘连线的距离,椎体矢状面安全核区与椎体后缘的距离;测量虚拟钉道安全核区的长度、宽度、高度;以直径3.5 mm的柱形模拟置钉,记录以安全核区为控制轴心的椎弓根钉在椎体水平横断面的外展角及椎弓根矢状面头尾倾角范围,进钉区皮质至安全核区中心点的距离;计算进钉区冠状面投影面积。结果虚拟钉道安全核构建法的有效率:C3、C4有效率分别为95%(57/60)、100%(60/60),总有效率为97.5%(117/120);钉道安全核高度为:C3左侧(4.99±1.04)mm、右侧(4.95±0.88)mm,C4左侧(5.41±0.93)mm、右侧(5.16±1.39)mm;安全核宽度:C3左侧(3.79±0.87)mm、右侧(3.44±0.88)mm,C4左侧(3.99±0.68)mm、右侧(3.60±0.92)mm;冠状面安全核区与上下钩椎关节外缘连线的距离为:C3左侧(0.66±0.54)mm、右侧(0.69±0.67)mm,C4左侧(0.62±0.59)mm、右侧(0.65±0.64)mm;椎体矢状面安全核区中心与椎体后缘的距离为:C3(2.08±0.41)mm,C4(2.34±0.60)mm,C4距离大于C3,空间位置均位于椎体内;椎体横断面椎弓根钉外展角区间为:C3左侧(28.16°±7.82°)^(67.46°±7.54°)、右侧(29.46°±7.5°)^(64.08°±9.79°),C4左侧(27.64°±4.56°)^(69.95°±6.66°)、右侧(29.17°±5.92°)^(71.14°±5.07°)。椎弓根矢状面的椎弓根钉头尾倾角区间为:C3左侧24.12°±5.35°、右侧24.40°±4.86°,C4左侧24.87°±5.7°、右侧25.65°±5.62°;进钉区皮质至安全核区中心点的距离为:C3左侧(11.93±0.76)mm、右侧(12.12±0.83)mm,C4左侧(11.24±0.71)mm、右侧(11.34±1.01)mm。进钉区冠状面投影面积为:C3左侧(41.38±15.68)mm2、右侧(37.66±13.77)mm2,C4左侧(44.54±12.96)mm2、右侧(40.33±15.54)mm2,左侧大于右侧。结论基于CT影像的下颈椎椎弓根钉道虚拟构建法对C3,4虚拟椎弓根钉道的构建有效率高。椎弓根钉道的构建证实C3,4适合植入目前常用的直径3.5 mm的颈椎椎弓根钉。安全核区形态学特点稳定,在标准颈椎正侧位X线片上可转化为容易辨认的解剖标志,为下颈椎椎弓根钉技术的实施提供参考。

Objective To introduce a novel method of the virtual construction for pedicle screw trajectory(PST)of subaxial cervical spine based on CT data and to investigate its effects on improving the accuracy rate of subaxial cervical pedicle screw technique.Methods The CT data of cervical spine(C3,4)of 60 subjects,including 30 males and 30 females,were collected for analysis.The data were imported into Mimics 20.0.Further,the virtual safe core(G-zone)of the PST was constructed using the method designed by authors.The following data was collected:1)the efficiency rate of the method for virtual constructed of PST and G-zone;2)the spatial position of the virtual safe core,including the distance between G-zone and the tangent line of upper and lower outer edge of Luschka's joint on the coronal plane,and the distance between the G-zone and the posterior edge of the vertebral body on sagittal plane;3)the length,width and height of G-zone;4)the abduction angle of pedicle screw on axial plane,and the cranial and caudad inclination angle on the sagittal plan of the pedicle;5)the mean distance between the cortex of lateral mass and the G-zone;6)the positive projection area of the trajectory on the coronal plan.Results The efficiency rate of the method for virtual constructed of PST and safe core were C395%(57/60)and C4100%with 97.5%(117/120)the total efficiency rate.The mean height of safe core was C34.99±1.04 mm(left)and 4.95±0.88 mm(right),C45.41±0.93 mm(left)and 5.16±1.39 mm(right).The mean width of safe core was C33.79±0.87 mm(left)and 3.44±0.88 mm(right),C43.99±0.68 mm(left)and 3.60±0.92 mm(right).The mean length of safe core was 3.5 mm.The distance between the G-zone and the tangent line of upper and lower outer edge of Luschka's joint on the coronal plane was C30.66±0.54 mm(left)and 0.69±0.67 mm(right),C40.62±0.59 mm(left)and 0.65±0.64 mm(right).The distance between the G-zone and the posterior edge of the vertebral body on sagittal plane was C32.08±0.41 mm and C42.34±0.60 mm,C4>C3(P<0.05).The interval of abduction angle on the axial plane of C3 were 28.16°±7.82°to 67.46°±7.54°(left)and 29.46°±7.5°to 64.08°±9.79°(right),C427.64°±4.56°to 69.95°±6.66°(left)and 29.17°±5.92°to 71.14°±5.07°(right).The range of cranial and caudad inclination angle of pedicle screw on sagittal plane were C324.12°±5.35°(left)and 24.40°±4.86°(right),C424.87°±5.7°(left)and 25.65°±5.62°(right).The mean distance between the entering cortex and the center of G-zone was C311.93±0.76 mm(left)and 12.12±0.83 mm(right),C411.24±0.71 mm(left)and 11.34±1.01 mm(right).The positive projection area of the PST on the coronal plan was C341.38±15.68 mm2(left)and 37.66±13.77 mm2(right),C444.54±12.96 mm2(left)and 40.33±15.54 mm2(right),C4 left>C4 right(P<0.05).Conclusion The efficiency rate of the virtual construction method for PST and safe core of the subaxial cervical spine was 97.5%.The length,width,and height of the virtual safe core were suitable for the implantation of the commonly used cervical pedicle screw with a diameter of 3.5 mm.The virtual G-zone was morphologically stable and easy to recognize on the anteroposterior and lateral cervical fluoroscopy view,which can provide a reliable landmark for the implementation of the pedicle screw of the subaxial cervical spine.