变异型寰椎椎弓根的影像解剖及后路置钉策略

Radiological anatomy and posterior screw placement strategy on C1 pedicle

目的：探讨变异型寰椎椎弓根螺钉的置钉策略及其安全性。方法：2005年1月-2011年1月共收治上颈椎不稳且存在寰椎椎弓根变异者28例，男11例，女17例；年龄18～75岁。术前测量寰椎后弓表面、椎动脉沟底及椎弓根近侧块根部三个切面的内、外侧区域高度，将变异型寰椎椎弓根分为3型。I型（寰椎后弓表面高度〈3．5ram，椎动脉沟底高度〉3．5ram）采取后弓下置钉，Ⅱ型（后弓表面高度及椎动脉沟底高度均〈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，椎动脉沟底高度〈3．5ram）采取in-out-in的技术置钉。术后评价置钉准确性及并发症情况。结果：56个变异型寰椎椎弓根中I型34个，Ⅱ型18个，Ⅲ型4个。寰椎近侧块面的椎弓根高度均〉5．0ram，内、外侧区域无显著性差异；椎动脉沟底的高度外侧区域显著高于内侧区域（t=13．07，P〈0．01），其中60％外侧区域高度〉3．5mm；后弓表面高度绝大多数〈3．0mm，且内、外侧区域无显著性差异。根据相应置钉策略，术中成功置钉54枚，成功率96．4％。术后CT显示理想和可接受置钉52枚占96．3％，不可接受置钉2枚占3．7％；术中与术后均未发生大出血以及椎动脉、神经根、脊髓损伤、寰椎后弓骨折等并发症．2例患者术后出现枕大神经刺激症状。结论：变异型寰椎椎弓根应根据不同分型采用相应的置钉策略，椎弓根外侧区域置钉更加安全可靠。

Objectives： To investigate the strategy and safety of posterior screw fixation on C1 pedicle. Methods： From January 2005 to January 2011, 28 cases suffering from upper cervical spine instability as well as C1 pedicle variation treated surgically in our hospital were reviewed retrospectively. There were 11 males and 17 females, with age ranging from 18 to 75 years old. Based on the height of medial and lateral part at 3 sections on C1 posterior arch, the vertebral artery groove and the boundary between pedicle and lateral mass, the atlas with variation were divided. Each category underwent specific strategy： Type I （height of posterior arch of atlas less than 3.Smm and vertebral artery groove more than 3.5ram） had anchoring point inferior to the posterior arch; Type ]] （both data less than 3.5ram） had anchoring point between pedicle and lateral mass; Type ]][（height of posterior arch of atlas more than 3.5ram and vertebral artery groove less than 3.5mm） underwent in-out-in technique. The accuracy and complication of screw fixation were evaluated in each category.