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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 develop an individualized orientation template using computer-aided design and rapid prototyping (RP) technique to investigate the accuracy and feasibility of assisted transthoracic pedicle screw implantation. Methods Dicom format data were obtained from 8 adult cadaveric atlantoaxial specimens by CT scanning. The three-dimensional reconstruction software Mimics10.01 was used to establish the atlantoaxial three-dimensional model and to measure the related parameters of atlantoaxial pedicle. The model was preserved in STL format. Open the three-dimensional reconstruction model of atlantoaxial vertebra in Imageware12.1 software, read in the point cloud data, locate the datum and reference plane, and then process the curves and surfaces in the Geomagic Studio10 software to determine the triangular mesh surface of the model. Finally Pro / Engineer4.0 software design pedicle optimal pedicle screw access, extraction atlas and posterior arch of the vertebral lamina at the posterior surface of the anatomical shape, and its anatomical form consistent with the reverse template, the design Pedicle screw into the nail channel and the reverse template synthesis together in the software to establish a personalized guide template data model, STL format to save. The STL file into the Dimension3D printer, the use of RP technology to create the physical model of atlantoaxial vertebral body and the physical orientation template. The individualized orientation templates were used to assist in the implantation of atlantoaxial pedicle screws on the specimens. The accuracy of screw placement was evaluated by both macroscopic and CT scan after operation. Results The sizes of individualized orientation templates were well designed and easy to use. Each template could be closely attached to the posterior bony structure of the corresponding atlantoaxial specimens. No loosening or displacement of the template was found during the nailing. A total of eight individualized orientation templates were used in the procedure to assist the implantation of 32 atlantoaxial pedicle screws. Macroscopic observation and CT tomography after surgery showed that all the screws entered the nail accurately, and the direction of nail entry was appropriate. The accuracy of atlas pedicle screw grading: 0 grade 15, grade Ⅰ 1; axial pedicle screw accuracy grade were 0. Conclusion The individualized orientation template produced by RP technique can assist the atlantoaxial pedicle screw implantation with high accuracy, simple operation and certain clinical application prospect.