寰枢椎椎弓根螺钉个体化导向模板的研制与实验研究

DESIGN AND EXPERIMENTAL STUDY OF INDIVIDUAL DRILL TEMPLATES FOR ATLANTOAXIAL PEDICLE SCREW FIXATION

目的利用计算机辅助设计和快速成型(rapid prototyping,RP)技术研制一种个体化导向模板,探讨其辅助寰枢椎椎弓根螺钉植入的准确性与可行性。方法对8具成人尸体寰枢椎标本行CT扫描获得Dicom格式数据,三维重建软件Mimics10.01中建立寰枢椎三维模型并测量寰枢椎椎弓根相关参数,模型以STL格式保存。在Imageware12.1软件中打开寰枢椎三维重建模型,读入点云数据、定位基准及参考平面;然后在Geomagic Studio10软件中对模型进行曲线和曲面的处理,确定模型的三角网格面;最后通过Pro/Engineer4.0软件设计椎弓根的最佳进钉通道,提取寰椎后弓及枢椎椎板后部的表面解剖学形态,建立与其解剖学形态相一致的反向模板,将设计的椎弓根螺钉进钉通道和反向模板合成在一起,在软件中建立起个体化导向模板的数据模型,以STL格式保存。将STL文件导入Dimension3D打印机,利用RP技术制作寰枢椎椎体实物模型和实物导向模板。在标本上利用个体化导向模板辅助植入寰枢椎椎弓根螺钉,术后通过肉眼观察和CT断层扫描两种方式评价螺钉植入的准确性。结果个体化导向模板大小设计合适,使用简便,每个模板均能紧密贴合于相应寰枢椎标本的后部骨性结构上,在植钉过程中未发现模板松动和移位。术中共应用8个个体化导向模板,辅助植入寰枢椎椎弓根螺钉32枚。术后肉眼观察及CT断层扫描显示所有螺钉进钉点准确,进钉方向适当。寰椎椎弓根螺钉准确性分级:0级15枚,Ⅰ级1枚;枢椎椎弓根螺钉准确性分级均为0级。结论利用RP技术生产出的个体化导向模板辅助寰枢椎椎弓根螺钉植入准确性高、操作简便,有一定的临床应用前景。

Objective To explore and evaluate the accuracy and feasibility of individual rapid prototype （RP） drill templates for atlantoaxial pedicle screw implantation. Methods Volumetric CT scanning was performed in 8 adult cadaveric atlas and axis to collect Dicom format datas. Then three-dimensional （3D） images of atlas and axis were reconstructed and the parameters of pedicles of 3D model were measured by using software Mimics 10.01. The 3D model was saved by STL format in Mimics. The scattered point cloud data of 3D model were processed and the 3D coordinate system was located in software Imageware 12.1. The curves and surfaces of 3D model were processed in software Geomagic Studio 10. The optimal trajectory of pedicle screw was designed and a template was constructed which accorded with the anatomical morphology of posterior arch of atlas and lamina of axis by using software Pro/Engineer 4.0. The optimal trajectory of pedicle screw and the template were integrated into a drill template finally. The drill template and physical models of atlas and axis were manufactured by RP （3D print technology）. The accuracy of pilot holes of drill templates was assessed by visually inspecting and CT scanning. Results The individual drill template was used conveniently and each template could closely fit the anatomical morphology of posterior arch of atlas and lamina of axis. Template loosening and shifting were not found in the process of screw implantation. Thirty-two pedicle screws were inserted. Imaging and visual inspection revealed that the majority of trajectories did not penetrate the pedicle cortex, only 1 cortical penetration was judged as noncritical and did not injury the adjacent spinal cord, nerve roots, and vertebral arteries. The accuracy of atlas pedicle screw was grade 0 in 15 screws and grade I in 1 screw, and the accuracy of axis pedicle screw was grade 0 in 16 screws. Conclusion The potential of individual drill templates to aid implantation of atlantoaxial pedicle screw is promising because of its high accuracy.