下颈椎“钉道安全核区”的构建及辅助徒手椎弓根钉置钉的可行性研究

The accuracy and feasibility study of freehand pedicle screw insertion for subaxial cervical spine assisted with safe core-referred technique

目的构建下颈椎“钉道安全核区”并验证其指导椎弓根置钉的准确性与可行性。方法本研究为实验研究。根据纳入和排除标准从赣南医学院第一附属医院CT数据库中进行筛选,纳入2015年1月至2020年3月行颈椎CT检查的60例患者的CT图像。将CT图像导入Mimics 20.0软件,按自行设计的“下颈椎椎弓根钉道虚拟构建法”,构建C_(3~7)的虚拟椎弓根钉道及钉道安全核区。记录虚拟“钉道安全核区”的构建成功率;测量安全核区的空间位置数据,包括冠状位平面安全核区与上下钩椎关节外缘连线间距离、矢状位平面安全核区与椎体后壁线的距离。测量后方进钉区皮质至安全核区中心点的钉道长度、横断面椎弓根钉外展角可变区间、冠状位平面进钉区域投影面积。应用8例成人颈椎标本进行模拟置钉实验,在X线机实时监测下以虚拟“钉道安全核区”为影像参考标志徒手置钉。椎体左侧采用“钉道安全核区参考法”徒手置钉(实验组);右侧采用传统徒手置钉法(Abumi法)置钉(对照组)。术者依据X线片对徒手置钉操作的准确性所做主观评判,并以CT扫描结果验证,比较两种置钉方法的术者判断正确率及实际置钉准确率。组间数据比较采用χ^(2)检验。结果下颈椎“钉道安全核区”的有效构建率为97.0%(291/300);冠状面上安全核区与上、下钩椎关节外缘连线的距离[M(IQR)]为0.91(0.98)mm(范围:0~1.85 mm);椎体矢状面安全核区与椎体后壁线的距离为(2.01±0.86)mm(范围:0.67~3.53 mm)。前段钉道长度为(11.58±1.00)mm(范围:8.27~14.93 mm)。进钉区冠状面投影面积为(36.18±11.67)mm^(2)(范围:13.38~83.11 mm^(2))。人体标本置钉实验结果方面,实验组的钉道制备修正率为7.5%(3/40),对照组为12.5%(5/40)(χ^(2)=0.139,P=0.709)。钉道制备完成后行CT检查,实验组正确率为100%(40/40),对照组正确率为82.5%(33/40),差异有统计学意义(χ^(2)=5.638,P=0.018)。置钉完成后CT检查结果显示实验组置钉准确率为100%(40/40),对照组为90.0%(36/40)(χ^(2)=2.368,P=0.124)。将术者主观判断置钉准确与否的结果与CT检查结果对比,实验组术者主观判断的正确率为100%(83/83),对照组为92.9%(79/85),差异有统计学意义(χ^(2)=4.199,P=0.040)。结论下颈椎“钉道安全核区”的构建成功率高,“钉道安全核区”辅助徒手椎弓根钉置钉技术可提高术者依据X线影像监测所作主观判断的准确性,进而提高下颈椎椎弓根钉技术的准确性,但仍需在临床实践中进一步验证。

Objectives To construct the“safe core”of the pedicle screw trajectory using CT imaging data of the subaxial cervical spine in adults,and to assess the accuracy and feasibility of the pedicle screw insertion assisted with the“safe core-referred technique”for subaxial cervical spine with a cadaver specimen study.Methods This is an experimental study.From January 2015 to March 2020,60 adults′CT images data of the cervical spine were collected from the database of the First Affiliated Hospital of Gannan Medical University,and were imported into Mimics 20.0 software.Virtual cervical pedicle trajectory and safe core were constructed according to the self-designed“virtual construction method of pedicle in the subaxial cervical spine”.The success rate of the construction and the spatial position data of the virtual safe core of was recorded,including the distance between the safe core and the tangent line of the upper and lower outer edge of Luschka′s joint on coronal plane,and the distance between the safe core and the posterior edge of the vertebral body on sagittal plane.The 3.5 mm column was used to simulate the pedicle screw placement,using the safe core as the only hub in pedicle screw trajectory.The length of the anterior pedicle screw trajectory,the interval of the abductive angle of the pedicle screw in axial plane,and the projection area of the entry area on periapical radiograph was calculated.In addition,8 adult cervical cadaver specimens were collected for the pedicle screw insertion experiment.The left side group used the“safe core-referred technique”for pedicle screw insertion,while the right side group used the Abumi method for pedicle screw insertion.The accuracy of pedicle screw placement was verified by CT scan.The difference between the accuracy of subjective judgment based on X-ray monitoring of operator and the actual accuracy of pedicle screw insertion verified by CT scan was compared between the two groups.The chi-square test was used to compare the intergroup data.Results The total success rate of the virtual construction method for the safe core of the subaxial cervical spine was 97.0%(291/300);The distance between the safe core and the tangent line of the upper and lower outer edge of Luschka′s joint on coronal plane was(M(IQR))0.91(0.98)mm(range:0 to 1.85 mm);The distance between the safe core and the posterior wall on the sagittal plane of the vertebral body was(2.01±0.86)mm(range:0.67 to 3.53 mm).The distance(anterior pedicle screw trajectory)from the posterior cortex to the central point of the safe core was(11.58±1.00)mm(range:8.27 to 14.93 mm).The projection area of the entry point on the coronal plane was(36.18±11.67)mm^(2)(range:13.38 to 83.11 mm^(2)).Pedicle screw insertion experiment in cervical cadaver specimen showed the rate of intraoperative correction of the pedicle screw trajectory was 7.5%(3/40)in the experimental group and 12.5%(5/40)in the control group(χ^(2)=0.139,P=0.709).The operator′s correct rate of subjective judgment on CT in the stage of pedicle screw trajectory preparation was 100%(40/40)in the experimental group and 82.5%(33/40)in the control group,the difference was statistically significant(χ^(2)=5.638,P=0.018).The actual correct rate of CT verification in the stage of pedicle screw insertion was 100%(40/40)in the experimental group and 90.0%(36/40)in the control group,the difference was statistically significant(χ^(2)=2.368,P=0.124);The operator′s correct rate of subjective judgment in the stage of pedicle screw insertion completion was 100%(83/83)in the experimental group and 92.9%(79/85)in the control group(χ^(2)=4.199,P=0.040).Conclusions The virtual safe-core of subaxial cervical spine can be use as a reliable anatomical fluoroscopy landmark for freehand pedicle screw insertion.“Safe core-referred technique”can improve the accuracy rate of the operator′s subjective judgment on the intraoperative fluoroscopy monitoring,and hence improve the accuracy of freehand pedicle screw insertion technology for subaxial cervical spine.And it still needs to be further verified in clinical practice.