快速成型胸椎个体化导航模板精确度实验研究

摘要

Objective: To observe the positioning accuracy of the template relative to the orientation of thoracic pedicle and provid reference for clinical application in the thoracic spine. Methods:Volumetric CT scan was performed on each of selected 12 complete dried thoracic vertebrae specimens and a 3-D reconstruction model was generated from the CT scan data. The optimal screw size and orientation were determined and a drill template was designed with a surface that is the inverse of the posterior vertebral surface. The drill template and its corresponding vertebra were manufactured using rapid prototyping technique . Subsequently, a diameter 2.0mm drill bit was inserted in the thoracic vertebrae specimen and its biomodel assisted by the drill template to simulate pedicle screw placement. The position and direction of drill bit in the pedicle and vertebral body was judged by visual observation. The accuracy of the rapid prototyping biomodel was measured by physical measurement With a vernier caliper of 0.02mm accuracy. Results: The drill bits were completely in the pedicle and vertebral body and in the same direction with the thoracic pedicles. There was the same anatomy morphous between the thoracic biomodel and its corresponding thoracic vertebrae specimen, the contours was unanimous between the template and posterior anatomy morphous of the thoracic vertebrae specimen. The error between the thoracic vertebrae and its corresponding biomodel was ( 0.49 ± 0.28 ) mm. Conclusion: Accurate location and orientation of the thoracic pedicle can be obtained by the rapid prototyping patient-specific navigational template in spite of the relative accuracy beteewn the rapid prototyping biomodel and real object.%目的:观察快速成型胸椎个体化导航模板的精确度,为快速成型个体化导航模板的临床使用提供参考.方法:选取12个完整的胸椎干燥骨标本,根据其CT扫描资料,利用计算机辅助设计及快速成型技术设计制作出相应的胸椎模型及个体化导航模板,通过个体化导航模板在胸椎标本及其模型上应用直径2.0mm的钻头模拟椎弓根螺钉置钉手术,直视观察钻头在椎弓根及椎体内的位置及走行方向.用精确度为0.02mm的游标卡尺对快速成型胸椎模型的精确性进行测量.结果:个体化导航模板和相应的胸椎标本及其模型后部解剖结构之间轮廓一致,贴附吻合良好,置入椎弓根进钉通道的钻头均完全位于椎弓根及椎体内,其走行方向和椎弓根的走行方向一致;所有胸椎模型和相应胸椎标本的解剖形态完全一致,胸椎标本和模型之间的误差范围在(0.49±0.28)mm之间.结论:虽然快速成型模型与实物之间有一定的误差,但其误差不影响对椎弓根准确定位及定向的精度要求.