逆向寰枢椎椎弓根螺钉导板的可行性研究

An anatomical study of guidance drill template for reverse C1, C2 pedicle screws

目的通过3D打印技术制作逆向寰枢椎椎弓根螺钉导航模板并指导置钉,观察研究螺钉准确性及导板的钉道控制能力.方法选取正常成人颈椎标本12具,CT扫描后获取其医学数字成像与交互(DICOM)格式数据,导入Mimics软件后三维建模并为寰枢椎逆向椎弓根螺钉选取理想进针点及进针方向,设计螺钉导航模板后导出标准模板库(STL)数据,最终3D打印成型.在导板辅助下完成上颈椎逆向椎弓根螺钉的置入,术后评价螺钉的准确性.重建整合椎体、理想及真实钉道后,通过配对t检验比较寰枢椎真实与理想钉道之间在进针角度及进针点位置的差异.结果每具寰枢椎标本左右侧各置入1枚螺钉,12具标本共逆向置入24枚逆向寰椎椎弓根螺钉及枢椎椎弓根螺钉23枚.24枚寰椎螺钉中有1枚螺钉穿破后弓上缘,1枚螺钉在未攻丝情况下拧入致后弓劈裂,优良率为91.7%,真实进针点分别距中线及侧块下缘(14.88±0.88)、(11.75±0.80) mm,理想进针点则分别为(15.25 ±0.89)、(11.34±0.77) mm,真实外、尾倾角分别为(10.28±1.66)°、(8.30±0.97)°,理想外、尾倾角分别为(9.91 ±1.69)°、(7.97±0.97)°;1枚枢椎螺钉穿破椎弓根外侧皮质,优良率为95.7%.真实钉道进针点距中线及下终板(7.30±0.68)、(17.17 ±0.73) mm,外倾角(17.97±0.96)°,尾倾角(19.41±1.52)°,理想钉道进针点距中线及下终板(6.93 ±0.68)、(16.80±0.73)mm,外倾角(17.69±1.03)°,尾倾角(19.80±1.51)°.经统计学分析,寰枢椎逆向椎弓根螺钉实际钉道与理想钉道在进针点位置(t=1.254、1.852、1.795、1.614,P>0.05)及进针角度(t=0.749、1.134、0.885、0.830,P>0.05)的差异无统计学意义.结论寰枢椎逆向螺钉导航模板能有效控制螺钉的进针点及进针方向,提高置钉准确性,具有临床应用前景.

Objective To validate the accuracy of reverse C1, C2 pedicle screw placement using the guidance of navigation drill template based on 3D printing techniques. MethodsTwelve normal adult cervical specimens were selected. The CT scan data were imported into Mimics by DICOM format. After the 3D modeling of upper cervical vertebras, the template models were imported into 3D printer with ideal trajectories. The reverse C1, C2 pedicle screws were placed under the navigation of templates. The accuracy of screws was assessed by CT scan. ResultsTotally 24 reverse C1 pedicle screws were placed: 22 showed excellent position and accuracy rate was 91.7%, actual caudal-angles and extroversive-angles were (8.30±0.97)° and (10.28±1.66)°, ideal caudal-angles and extroversive-angles were (7.97±0.97)° and (9.91±1.69)°, ideal and actual distances between entry point and inferior margin of lateral mass were (14.88±0.88) and (15.25±0.89) mm, distances between entry point and median line were (11.75±0.80), and(11.34±0.77) mm. Twenty-three C2 pedicle screws were placed, one of them destructed pedicle laterally and accuracy rate was 95.7%. The actual extroversive-angles and caudal-angles were (17.97±0.96)° and (19.41±1.52)°, and the ideal were (17.69±1.03)° and (19.80±1.51)°;actual and ideal distances between entry point and median line were (7.30±0.69) and (6.93±0.68) mm;the real and ideal distances between entry point and inferior endplate were (17.17±0.71) mm and (16.80±0.73) mm. The differences in deviation in the position of entry point (t=1.254, 1.852, 1.795, 1.614, P>0.05) and direction (t=0.749, 1.134, 0.885, 0.830, P>0.05) between actual and ideal trajectories were not statistically significant. Conclusion3D printing navigation guidance template for reverse C1, C2 pedicle screws can improve the accuracy of screw placement and strictly control direction and entry point, showing a promising prospect for clinical application.