导航模板辅助下颈椎皮质骨螺钉置入准确性的研究

目的　探讨基于皮质骨螺钉轨迹入路，导航模板辅助椎弓根螺钉置入的可行性和准确性。 方法　获取4具下颈椎标本（C3~7）CT数据,经Mimics软件三维重建后设计椎弓根皮质骨螺钉轨迹，并建立导航模板。随机分成2组,分别采用快速成型（RP）和数控机床技术（CNC）制造出两种材质导航模板并测量其在颈椎椎弓根辅助置钉的精确性。 结果　RP、CNC两组在进钉点的水平面上绝对偏差分别为：(0.28±0.24) mm、(0.32±0.23) mm；矢状面上分别为：(0.30±0.20) mm、(0.52±0.44) mm。钉道中点在水平面上分别为：(0.26±0.22) mm、(0.39±0.32) mm；矢状面上分别为：(0.37±0.29) mm、(0.49±0.50) mm。螺钉安全分级，RP组1级螺钉20枚；CNC组1级螺钉19枚，2级1枚。两组的绝对偏差值、安全分级差异均无统计学意义（P＞0.05）。 结论　CNC导航模板经皮质骨螺钉轨迹辅助置钉是可行的，为下颈椎椎弓根置钉提供了一种全新、安全的方法。

Accuracy of patient-specific drill template cervical pedicle screws insertion via cortical bone trajectory

Objective　To validate the security and accuracy of cervical pedicle screws insertion (CPSI) with the assistance of patient-specific drill templates (PDTs) via cortical bone trajectory.　Methods Four normal cervical spine specimens（C3~7） were selected and randomly divided into two groups. All specimens received CT scan. After images processing, the individual guide templates with cortical bone trajectory (CBT) were designed and subsequently produced by rapid prototyping (RP) and computer numerical control (CNC) technology, respectively. Then, their security and accuracy were evaluated in facilitating CPSI.　Results　The absolute deviations at the entry point were (0.28±0.24) mm in group RP and (0.32±0.23) mm in group CNC on the transverse plane, and were (0.30±0.20) mm in group RP and (0.52±0.44) mm in group CNC on the sagittal plane. The absolute deviations at the midpoint of the pedicle were (0.26±0.22) mm in group RP and (0.39±0.32) mm in group CNC on the transverse plane, and were (0.37±0.29) mm in group RP and (0.49±0.50) mm in group CNC on the sagittal plane. For the screw position, 20 screws position were in grade 1 in group RP; 19 screws position were in grade 1 and 1 was in grade 2 in group CNC. No statistically significant difference existed (P>0.05) in deviation and screw position between the two groups.　Conclusion　CNC-PDTs via cortical bone trajectory are viable in facilitating CPSI with good feasibility and accuracy. It is a new alternative method to lower cervical pedicle insertion.