3D打印颈椎前路椎弓根螺钉导板的准确性评估

Accuracy assessment of 3D printed guider for cervical anterior transpedicular screw insertion in Sawbones cervical models

[目的]设计制作3D打印颈椎前路椎弓根螺钉置钉导板,通过导板置钉并分析置钉的准确性。[方法]选取4具Sawbones颈椎骨模(C_1~C_7)进行CT扫描,三维重建颈椎椎体,通过计算机辅助设计在重建的3D模型上模拟出椎弓根螺钉的安全通道,并选取与相应椎体前方贴合的区域为导板基底部,将通道和导板基底部结合起来设计出合理的置钉导板,利用3D打印机制作出导板,导板辅助下在4具颈椎骨模(C_3~C_7)上置入20枚椎弓根螺钉。然后将带有螺钉的颈椎模型进行二次CT扫描,测量螺钉在椎弓根横断面和矢状面偏离中线的值,按照螺钉偏离椎弓根的绝对值及相对值两种评价方式评价置钉安全性。[结果]3D打印导板能成功辅助颈椎前路椎弓根螺钉的置入。螺钉在横断面向内、外偏移差异无统计学意义(P=0.688),在矢状面向上、下偏移差异无统计学意义(P=0.967)。按照螺钉偏离椎弓根的绝对值评价,位于安全位置的螺钉为19/20(95%);按照螺钉偏离椎弓根的相对值评价,不安全置钉数为0/20。[结论]使用3D打印导板辅助置入颈椎前路椎弓根螺钉,简易、实用、安全。该技术的临床应用值得深入研究。

[Objective] To assess accuracy of the 3D printed guider for cervical anterior transpedicular screw （ATPS） inser- tion in Sawbones cervical models. [Methods] CT scanning was conducted on 4 Sawbones cervical models （C1-C7） to reconstruc- tion of the cervical segments. Safe traces of ATPS were mimicked in the reconstructed cervical spine with computer-aided de- sign （CAD） software, and then corresponding anterior vertebral surface were selected as fitting area for the base part of the guid- ers. Combined the safe screw traces with the base parts, complete guiders were designed, subsequently made by a 3D printer. Af- terward, 20 screws （ATPS） were inserted into the cervical pedicles anteroposterior leaded by the conforming 3D printed guiders in the 4 Sawbones cervical models （C3-C7）. Lastly, the cervical models placed with the ATPS underwent CT scanning again, to measure the deviations of each screw from the axis on sagittal and transverses planes because the security of screw insertion was determined by the absolute and relative deviations of the screw from the pedicle axis. [Results] All the 3D printed guiders suc- cessfuUy led ATPS insertion. There were no significant differences between medial and lateral deviations （P=0.688） or between ＂superior and inferior deviations （P=0.967）. In term of absolute value, 19/20 screws （95%） were placed in the safe zone, whereas 0/20 screws inserted in non-critical position regarding to the relative value. [Conclusion] The 3D printed guider is simple, easy and safe for assisting ATPS insertion. However, clinical application of this technique needs further researches.