枢椎椎弓根螺钉置钉失误的影像学分析

Image analysis of pedicle screw misplacement in axis

中文关键词:  枢椎  椎弓根螺钉  置钉失误  椎动脉孔解剖变异

英文关键词:Axis  Pedicle screw  Pedicle placement malposition  Anatomic abnormality of vertebral foramen

中文摘要:

  【摘要】　目的：分析枢椎椎弓根螺钉置钉失误的原因，探讨提高置钉成功率的方法。方法：2002年1月~2006年12月我院因上颈椎外伤、脱位和肿瘤接受寰枢椎后路内固定手术的患者50例，共置入100枚枢椎椎弓根螺钉。根据术前CT薄层扫描结果将枢椎椎动脉孔分为Ⅰ、Ⅱ、Ⅲ、Ⅳ型；在术后颈椎侧位X线片上测量枢椎椎弓根螺钉钉道上倾角，在术后CT片上测量钉道内倾角，并根据CT结果将置钉失误分为两类，A类为钉道偏内指向椎管，B类为钉道偏外指向椎动脉孔。结果：100个枢椎椎动脉孔分为Ⅰ型76个，Ⅲ型10个，Ⅳ型14个。100枚枢椎椎弓根螺钉共发生A类失误8枚（8％），其中Ⅰ型5枚，Ⅲ型1枚，Ⅳ型2枚；B类失误2枚（2%），其中Ⅲ型、Ⅳ型各1枚。Ⅰ型、Ⅲ型、Ⅳ型的置钉失误率分别为6.6％、20%、21.4%。A类失误组的钉道上倾角为14.8°±8.5°，明显小于钉道正确组的18.3°±9.7°（P<0.05），B类失误组为17.5°±6.8°，与正确钉道组无显著性差异（P>0.05）。A类失误组的钉道内倾角为21.4°±7.1°，明显小于钉道正确组的33.7°±7.3°（P<0.05）；B类失误组为44.9°±8.8°，明显大于正确钉道组（P<0.05）。结论：枢椎椎动脉孔的解剖变异是导致置钉失误的客观因素；而术中钉道内倾角和上倾角偏小是引起置钉失误的最常见原因。术前应根据CT扫描结果充分掌握枢椎椎动脉孔的特点，结合“宁上勿下，宁内勿外”的原则，合理把握钉道方向，以提高置钉成功率。

英文摘要:

  【Abstract】 Objective：To investigate the causes of pedicle screw misplacement in axis and the way to ensure the accuracy.Method：From January 2002 to December 2006，50 patients suffering from upper cervical trauma and tumor and undergoing posterior surgery were included in this study.A total of 100 axis pedicle screws were placed.Based on preoperative slice CT scan results，the vertebral artery grooves were divided into 4 types（Ⅰ，Ⅱ，Ⅲ，Ⅳ）.After operation，the pedicle trajectory′s medial-inclination angle and superior-inclination angle were measured respectively on lateral radiograph and CT scan image.The pedicle screw misplacement were divided into two groups：type A，the vertebral artery groove violation；type B：the vertebral canal violation.Result：The 100 axis vertebral artery grooves included 76 type Ⅰ，10 type Ⅲ and 14 type Ⅳ.Type A malposition accounted for 8（8%），including 5 type Ⅰ，1 type Ⅲ，and 2 type Ⅳ；while type B malposition accounted for 2（2%），including 1 type Ⅲ and 1 type Ⅳ.With the malposition rate for type Ⅰ，Ⅲ and Ⅳ was 6.6％，20％ and 21.4％ respectively.The superior inclination angle for type A was 14.8°±8.5°，which was less than no malposition group（18.3°±9.7°）；while that for type B was 17.5°± 6.8°，which showed no statistical difference compared with no malposition group（P>0.05）.The medial inclination angle for type A was 21.4°±7.1°，which was less than no malposition group（33.7°±7.3°）（P<0.05）；and that for type B was 44.9°± 8.8°，which was higher than no malposition group（P<0.05）.Conclusion：The anatomic abnormality for vertebral artery foramen is an objective factor to affect the accuracy of pedicle screw placement；less medial inclination angle and superior inclination angle are more prevalenting attention to vertebral artery foramen in axis based on CT scan and placement principle “upper better than down and introversion better than extroversion” can improve screw placement accuracy.