基于正侧位X线片上钉道尖端位置判断枢椎椎弓根螺钉置钉安全性的影像学研究

Imaging study on the safety of axial pedicle screw placement by the position of the screw trajectory tip on the anteroposterior and lateral radiographs

目的提出一种基于正侧位X线片上钉道尖端位置判断枢椎椎弓根螺钉置钉安全性的方法。方法选取2020年12月至2021年12月温州医科大学附属第二医院入院患者40例颈椎CT数据,男24例,女16例,年龄(47.6±13.2)岁。基于Mimics软件三维模型重建及X-ray功能,模拟枢椎椎弓根螺钉置钉及其正侧位片的透射。模拟螺钉钉道尖端位置在正位虚拟片上由内至外被分为5个区域(区域Ⅰ~Ⅴ),虚拟侧位片上分为上下两个区域(区域a、b),通过调整螺钉方向,使得钉道尖端在正位及侧位虚拟投影上分别位于对应的10个位置区域(每个区域80个螺钉),并通过CT分析其准确性,判断是否穿破椎弓根内侧壁或椎动脉孔。收集2014年1月至2021年12月34例行枢椎椎弓根螺钉置钉的患者(共置入枢椎椎弓根螺钉67枚)的正侧位X片和术后CT数据,男18例,女16例,年龄(45.8±14.1)岁。以同样的方式划分钉道尖端在正位及侧位片上的位置,分别统计对应10个位置上的螺钉数量,并通过CT分析判断各枚螺钉是否穿破椎弓根内侧壁或椎动脉孔。结果影像学模拟置钉研究结果显示,模拟螺钉钉道尖端在区域Ⅳ和区域Ⅴ内其椎动脉孔穿破率分别为75.0%(120/160)和100%(160/160),而在区域Ⅰ时其椎弓根内侧壁穿破率为85.6%(137/160)。区域Ⅱ和Ⅲ内置钉失误率相对较低,其中位于区域a的模拟螺钉表现更优于区域b,区域a-Ⅱ和a-Ⅲ的置钉椎弓根内侧壁穿破率分别为7.5%(6/80)和0,椎动脉孔穿破率为0和21.3%(17/80)。影像学回顾性研究中同样显示区域Ⅰ、Ⅳ和Ⅴ内螺钉失误率较高,区域Ⅱ和Ⅲ内失误率相对较低,其中区域a-Ⅱ和a-Ⅲ内共15枚螺钉且未发生任何椎弓根内侧壁和椎动脉孔的破坏。结论区域a-Ⅱ和a-Ⅲ是枢椎椎弓根螺钉置钉时钉道尖端位置的“安全区域”。通过分析正侧位X线片上钉道尖端所在区域,术者可以确定合理的置钉轨迹,预防颈髓和椎动脉的损伤,降低手术风险。

Objective To propose a method to judge the safety of axial pedicle screw placement based on the position of the tip of the screw trajectory on the anteroposterior and lateral X-ray radiographs.Methods The cervical CT data of 40 patients admitted to the Second Affiliated Hospital of Wenzhou Medical University from December 2020 to December 2021 were selected,including 24 males and 16 females,with a mean age of(47.6±13.2)years.Based on the three-dimensional model reconstruction of Mimics software and its function of X-ray,the transmission of the axial pedicle screw and its anteroposterior and lateral films was simulated.The position of the tip of the simulated screw trajectory was divided into 5 regions(regionsⅠ-Ⅴ)from the inside to the outside on the anteroposterior virtual radiographs,and the upper and lower regions(regions a,b)on the lateral virtual radiographs.By adjusting the direction of the screw,the tip of the screw was located in the corresponding 10 regions(80 screws in each area)on the virtual projections of the anteroposterior and lateral virtual radiographs respectively,and its accuracy was analyzed by CT to determine whether each screw penetrated the medial wall of the pedicle or vertebral artery foramen.The anteroposterior and lateral X-rays and postoperative CT data of 34 patients who underwent axial pedicle screw placement(67 axial pedicle screws were placed in total)from January 2014 to December 2021 were collected,including 18 males and 16 females,with a mean age of(45.8±14.1)years.The position of the tip of the screw trajectory on the anteroposterior and lateral films was divided in the same way.The number of screws in the corresponding 10 positions was counted,and CT analysis was used to determine whether each screw penetrated the medial wall of the axial pedicle or the vertebral artery foreman.Results The results of the imaging simulation screw placement study showed that the perforation rate of the vertebral artery foramen in regionⅣandⅤwas 75.0%(120/160)and 100%(160/160),respectively,while the perforation rate of the medial wall of the axial pedicle in the regionⅠwas 85.6%(137/160).The failure rate in regionsⅡandⅢwas relatively lower,and the performance of simulated screws located in the region a was better than those in region b.The perforation rates of the medial wall in regions(a-Ⅱ)and(a-Ⅲ)was 7.5%(6/80)and 0(0/80),respectively,and the perforation rates of the vertebral foramen was 0(0/80)and 21.3%(17/80),respectively.The retrospective imaging study also showed a higher rate of placement failure in regionsⅠ,ⅣandⅤ,and relatively lower in regionsⅡandⅢ.There were total of 15 screws in region a-Ⅱand a-Ⅲ,and no destruction of the medial wall of the axial pedicle and the vertebral artery foreman occurred there.Conclusions Regions a-Ⅱand a-Ⅲare the"safety areas"of the tip of the pedicle screw trajectory in the axial vertebra.By analyzing the tip of the pedicle screw trajectory on the anteroposterior and lateral radiographs,the operator can determine the reasonable trajectory of axial pedicle screw placement,prevent the injury of the cervical spinal cord and vertebral artery,and reduce the risk of operation.