寰枕融合对枢椎椎弓根螺钉植入的影响

目的 研究寰枕融合(C1A)对枢椎(C2)椎弓根大小的影响及不同C2螺钉植入技术.方法 C1A患者17例,其中合并寰枢椎脱位14例,合并颅底凹陷、Chiari畸形3例;非寰枕融合(non-C1A)患者25例作为正常对照组.所有患者术前均行CT薄层扫描,导航系统中模拟植入C2椎弓根螺钉,以不破坏椎弓根骨皮质为准,分别测量两组患者C2椎弓根所能容纳的最大椎弓根螺钉直径(MPSD).结果 C1A组17例,34侧C2椎弓根平均MPSD为(5.8±1.4)mm,其中5侧小于4 mm(15%);non-C1A组25例,50侧C2椎弓根平均MPSD为(6.5±1.4)mm,4侧小于4 mm(8%).二组平均MPSD差异有统计学意义(P＜0.05).对不适合C2椎弓根螺钉植入的患者,延长固定节段至C3侧块2例,C2椎弓根峡部螺钉2例,椎板间螺钉1例.结论 C1A患者C2椎弓根较正常相对狭小,螺钉植入时应更加小心或选用其他固定方式.

Impact of C1 assimilation on C2 pedicle screw insertion

Objective To study the impact of C1 assimilation (C1 A) on C2 pedicle screw insertion,and variation of C2 screw insertion techniques. Methods Seventeen C1 A patients which needed C2 pedicle screw insertion and fixation were collected, including 14 cases of atlantoaxial dislocation and 3 cases of Chiari malformation. All patients underwent thin slice CT scanning. The C2 pedicle screw was virtually inserted by using computer-assisted navigation, and the maximum pedicle screw diameter (MPSD), which could be inserted without breaching the C2 pedicle cortex was measured in 3-plane reconstruction. All patients underwent surgery according to the measurement. Results In C1 A group, the mean MPSD of 34 pedicles was (5.8 ± 1.4)mm; and in 5 of 34 (15%) pedicles, the MPSD was less than 4 mm. In non-C1 A group, the mean MPSD of 50 pedicles was (6. 5 ± 1.4) mm; and in 4 (8%)pedicles, the MPSD was less than 4 mm. The mean MPSD had statistical significance between two groups (P ＜ 0. 05). For patients not suitable to C2 pedicle screw insertion, the fixation was executed by extending the fixation to C3 in 2 patients,by using C2 pars interarticularis screw in 2, and inter-laminar screw in 1. Conclusions C2 pedicle in C1 A patient is relatively narrower; more attention should be paid, or alternative screw insertion techniques can be used.