寰椎后弓变异患者寰椎椎弓根螺钉的置钉策略

Strategies of posterior screw fixation on C1 pedicle with the variation of posterior arch of altas

中文关键词:  寰椎  椎弓根  椎弓根螺钉  影像学测量

英文关键词:Atlas  Pedicle screw  Image anatomy

中文摘要:

  【摘要】 目的：探讨寰椎后弓变异患者寰椎椎弓根螺钉的置钉方法及其安全性。方法：回顾性分析2005年1月~2011年1月寰椎后弓变异行寰椎椎弓根螺钉固定的28例患者，其中男11例，女17例；年龄6～75岁,平均36.2±15.5岁。根据CT重建图像将寰椎椎弓根划分为后弓表面、椎动脉沟底和椎弓根侧块交界区3个切面，并将每个切面再分为内侧、外侧2个部分。对各部位相应切面的后弓高度进行测量，根据所测结果，将变异寰椎后弓分为3种类型，并采用相应的椎弓根螺钉置钉方法：Ⅰ型（寰椎后弓表面高度＜3.5mm，椎动脉沟底椎弓根高度＞3.5mm），采取后弓下置钉；Ⅱ型（后弓表面高度及椎动脉沟底椎弓根高度均＜3.5mm），采取椎弓根侧块交界点处置钉；Ⅲ型（后弓表面高度＞3.5mm，椎动脉沟底椎弓根高度＜3.5mm），采取in-out-in技术置钉。术后采用CT片评价置钉准确性，并观察并发症发生情况。结果：56个寰椎后弓变异的椎弓根中，Ⅰ型34个，Ⅱ型18个，Ⅲ型4个。术中成功置钉54枚，成功率96.4%；2个Ⅱ型变异后弓椎弓根（2例一侧）因椎弓根过小无法置钉而改用椎板钩固定。术后CT显示理想和可接受置钉52枚（96.3%）；不可接受置钉2枚（3.7%），均表现为螺钉穿入椎管。2例患者术后出现枕大神经刺激症状，1例经对症处理、1例拆除内固定后症状缓解。术中与术后均未发生大出血，无椎动脉、神经根及脊髓损伤，无寰椎后弓骨折等其他并发症。结论：寰椎后弓变异患者仍可采用寰椎椎弓根螺钉固定，在实施时应根据不同分型采用相应的置钉策略。

英文摘要:

  【Abstract】 Objectives: To investigate the strategy and safety of posterior screw fixaiton on C1 pedical with variation. Methods: 28 cases from January 2005 to January 2011 suffering from upper cervical spine instability and with C1 pedicle variation treated surgically in our hospital were reviewed retrospectively. There were 11 males and 17 females, with the ages ranging from 6 to 75 years old（average, 36.2±15.5 years）. Three cross sections(surface of posterior arch, vertebral artery groove and junction of pedicle and lateral mass) and their two sides(lateral and medial side) were divided on CT reconstruction image, and the height of posterior arch was measured thereby. Three types of the atlas with variation could be defined accordingly. Depended on these types, different screw placements were performed as follows: type Ⅰ(height of C1 posterior arch less than 3.5mm and vertebral artery groove more than 3.5mm) with the screw placed under posterior arch; type Ⅱ(both of them less than 3.5mm) with the fixation at the boundary between pedicle and lateral mass; type Ⅲ(height of C1 posterior arch more than 3.5mm and vertebral artery groove less than 3.5mm) with in-out-in screw placement technique. The accuracy of screw placement and associated complications were evaluated. Results: 56 atlas pedicles were placed which included 34 type Ⅰ, 18 type Ⅱ and 4 type Ⅲ. A total of 54 screws was successfully placed into the atlas(96.4%), while the other 2 screws failed and changed into laminar hook due to small pedicle diameter from type II variation. After operation, CT scan showed ideal or acceptable(96.3%) screw position in 52 and unacceptable(3.7%)in 2 with screws penetrating into spinal canal. There were no obvious complications in the present series, while two patients complained of greater occipital nerve irritation which was alleviated after appropriate treatment. Conclusions: Pedicle screw can be inserted safely in the C1 with posterior arch variation. Different screw placement strategies can be employed depending on the C1 variation types.