导航系统辅助下颈椎椎弓根螺钉置钉准确性的实验研究

目的：评价导航系统辅助下颈椎（C3～C7）椎弓根螺钉内固定置钉的准确性.方法：将32具成人尸体颈椎标本随机分为4组,分别采用盲法、透视法、透视导航法和CT导航法进行下颈椎椎弓根螺钉置入.术后采用标本大体解剖观察的方法评价置钉准确性.分优（螺钉完全在椎弓根内）、可（仅有螺纹穿出,对周围组织无损伤）和差（螺钉明显穿出）进行统计.结果：共置入螺钉318枚.盲法80枚,平均手术时间27min,优29枚（36 3%）、可21枚（26.3%）、差30枚（37.5%）;透视法78枚（有1例C4、C5右侧椎弓根均细小,不能容纳3.5mm螺钉）,平均手术时间112min,优35枚（44.9%）、可29枚（37.2%）、差14枚（17.9%）;透视导航法80枚,平均手术时间69min,优34枚（42.5%）,可36枚（45%）,差10枚（12.5%）;CT导航法80枚,平均手术时间98min,优70枚（87.5%）、可10枚（12.5%）.各组间手术时间均有显著性差异（P＜0.05）,透视法与透视导航法的置钉准确率间无显著性差异,其余各组间均有显著性差异（P＜0.05）.结论：单纯根据术前影像结果盲法行下颈椎椎弓根螺钉内固定不安全.透视法和透视导航法可提高置钉准确性,但手术风险仍较大,透视导航法比透视法置钉的手术时间缩短.CT导航法并未比透视法增加手术时间,但置钉准确性显著提高.

The study of accuracy of screw placement in lower cervical pedicle assisted by navigation system

Objective:To assess the accuracy of transpedicular screw placement in the lower cervical spines(C3-C7) assisted by navigation system.Method:32 human cadaveric cervical spines were utilized and 3.5mm screws were placed into the C3~C7 pedicles following four kinds of techniques:blind screw placement(group 1),assisted by X-ray fluoroscopy(group 2),assisted by virtual fluoroscopy navigation system(group 3),assisted by CT-based navigation system(group 4).Thereafter,cortical integrity of every sample was examined by anatomic dissection.Cortical breaches were classified by critical or non-critical breaches.Result:All together,there were 318 pedicles involved.Group 1,80 pedicles,the average operation time per sample was 27 minutes.36.3% of the screws were placed entirely within the pedicle,26.3% showed non-critical breaches, and 37.5% showed critical breaches.Group 2,78 pedicles,the average operation time was 112 minutes.44.9% were placed entirely within the pedicle,37.2% showed non-critical breaches,and 17.9% showed critical breaches.Group 3,80 pedicles,the average operation time was 69 minutes.42.5% were placed entirely within the pedicle,45% showed non-critical breaches,and 12.5% showed critical breaches.Group 4,80 pedicles,the average operation time was 98 minutes.87.5% were placed entirely within the pedicle,12.5% showed non-critical breaches.There were statistically significant difference among the four groups with respect to the average operation time and the accuracy of screw placement(P<0.05),except for the comparison of accuracy between fluoroscopy and virtual fluoroscopy navigation system,which had no statistically significant difference.Conclusion:Blind screw placement is insecure.The assistance of fluoroscopy or virtual fluoroscopy navigation system definitely enhances accuracy.But the odds of severe breaches are still high.The virtual fluoroscopy navigation system has a shorter operation time than fluoroscopy,however it can not improve the accuracy of screw placement.CT-based navigation system drastically enhances accuracy and further improves the security of transpedicular screw placement.