寰椎椎弓根髓腔大小对椎弓根螺钉置入的影响

The impact of the size of atlas pedicle medullary canal on C1 pedicle screw placement

目的：评估寰椎椎弓根髓腔大小对椎弓根螺钉置入的影响。方法：从2009年1月-2012年6月在本院行寰枢椎后路固定融合术的患者中，筛选出年龄≥20岁、术前影像学测量寰椎椎弓根高度〉4mm的患者97例，男41例，女56例，年龄20-79岁，平均41.6岁。术中选择内固定方法时，寰椎首先选择椎弓根螺钉固定，若椎弓根螺钉置钉失败则改用椎板钩或侧块螺钉固定。其中145个椎弓根成功置入椎弓根螺钉，49个椎弓根因无法形成椎弓根螺钉通道，改用椎板钩或侧块螺钉固定。用CT三维重建技术测量所有患者寰椎椎弓根髓腔的高度。根据髓腔高度将寰椎椎弓根分为3型：Ⅰ型，髓腔高度≥2mm；Ⅱ型，髓腔高度＜2mm；Ⅲ型，无髓腔。统计每型椎弓根成功置入椎弓根螺钉的比率，比较其差异。结果：椎弓根螺钉固定组中，Ⅰ、Ⅱ、Ⅲ型椎弓根个数（比率）分别为104个（71.7％）、39个（26.9％）、2个（1.4％）；非椎弓根螺钉固定组中，Ⅰ、Ⅱ、Ⅲ型椎弓根个数（比率）分别为2个（4.1％）、28个（57.1％）、19个（38.8％）。Ⅰ、Ⅱ、Ⅲ型椎弓根成功置入椎弓根螺钉的比率分别为98.1％（104/106）、58.2％（39/67）、9.5％（2/21），Ⅰ型明显高于Ⅱ型和Ⅲ型，Ⅱ型明显高于Ⅲ型，差异均有统计学意义（P〈0.001）。结论：寰椎椎弓根髓腔大小对椎弓根螺钉的置入有一定影响。寰椎椎弓根髓腔高度≥2mm时建议行椎弓根螺钉固定，髓腔高度＜2mm时可根据术者情况选择固定方法；无髓腔时建议不行椎弓根螺钉固定。

Objectives： To investigate the impact of the size of atlas pedicle medullary canal on C1 pedicle screw placement. Methods： From patients who underwent posterior atlantoaxial fixation between January 2009 and June 2012, those with an age ≥20 year, and with the height of the C1 pedicle greater than 4mm were included in our study. 97 patients met the inclusion criterion. There were 41 males and 56 females, with an average age of 41.6 years（range, 20-79 years old）. If the placement of atlas pedicle screws failed, then an alternative approach such as C1 lateral mass screws or lamina clamps were used. 145 pedicle screws were implanted successfully, but the other 49 atlas pedicle screw placements failed, subsequently other fixation methods were used. The height of the medullary canal of all patients′ pedicles were measured by using computed tomography（CT） multi-planar reconstruction technique. The pedicles of the atlas were classified into 3 types according to the size of the medullary canal. Type Ⅰ： the height of the medullary canal ≥2mm; type Ⅱ： the height of the medullary canal 〈2mm; type Ⅲ： no medullary canal in the pedicle. The percentage of atlas pedicle screw fixation in each type of pedicles was calculated, and the differences among the three types were compared. Results： In the pedicle screw fixation group, the number（percentage） of the pedicles of type Ⅰ, type Ⅱ, type Ⅲ was 104（71.7%）, 39（26.9%）, 2（1.4%）respectively; while in the non-pedicle screw fixation group, the number（percentage） of the pedicles of type Ⅰ, type Ⅱ, type Ⅲ was 2（4.1%）, 28（57.1%）, 19（38.8%） respectively. The percentage of atlas pedicle screw fixation in type Ⅰ, type Ⅱ, type Ⅲ pedicle was 98.1%（104/106）, 58.2%（39/67）, 9.5%（2/21）, respectively. The percentage of C1 pedicle screw fixation in type Ⅰ pedicle was greater than type Ⅱ and type Ⅲ, and the percentage of C1 pedicle screw fixation in type Ⅱ pedicle was greater than type Ⅲ（P〈0.001）. Conclusions： The size of the medullary canal of the atlas pedicle is critical in atlas pedicle screw placement. When the size of the medullary canal of the atlas pedicle is ≥2mm, pedicle screw fixation is suggested; when it is 〈2mm, various fixation techniques can be considered based on the technology of the surgeon; pedicle screw fixation is not suggested when there is no medullary canal in the pedicle.