下颈椎前路椎弓根螺钉置入的实验研究

目的 探讨下颈椎前路椎弓根螺钉置入技术的可行性.方法 取18具成人尸体正常颈椎标本,剔除其周围软组织至清楚显露椎体前壁.CT扫描后,用Mimics软件重建三维模型,并测量C3～C7个体化置钉参数,包括进钉点(即椎弓根中轴线在椎体前壁投影点)、置钉方向(螺钉在横断面和矢状面上的倾斜角度)以及螺钉长度.严格按照测量结果,直视下置入椎弓根螺钉.术后作CT扫描,评价置钉效果.结果 进针点:C3、C4位于置钉椎弓根对侧,正中矢状面旁2～3 mm,距上终板6～7 mm；C5～ C7与置钉椎弓根同侧,其中C5位于正中矢状面旁1～2 mm,距上终板7.0～7.5 mm,C6、C7则为4～5 mm和7.5 ～8.5 mm.置钉方向:理想角度在C3、C4为外倾角46°～47°,头倾角-11°～-7°；在C5外倾角约48°,头倾角接近0°；C6、C7为36°～40°和8～13°.螺钉长度:可选择28、30、32 mm,其直径为3.5 mm.本组共置钉144枚.术后CT示,全部螺钉均经椎体前方置入椎弓根内抵达侧块.其中,有16枚胀破椎弓根外侧皮质,3枚穿破外侧皮质(均发生在C3、C4节段).结论 下颈椎前路椎弓根螺钉置入技术是可行的.

Insertion of lower cervical spine anterior pedicle screw in 18 cadavers

Objective To study the feasibility of lower cervical spine anterior pedicle screw(APS) insertion and provide basis for its clinical application according to the preoperative APS related technological parameters.Methods Normal cervical spine specimens of 18 cadavers were carefully dissected to resect the surrounding tissue and to clearly expose the centrum antetheca.Following the CT scans,three dimensional model was reconstructed by Mimics software.The imaging data to measured key parameters of anterior transpedicular screw fixation were also produced by Mimics software.The individual screw insertion parameters including intersection point(projective point of pedicle central axis on the centrum antetheca),insertion angle(the inclined angle of screws in cross-sectional and sagittal plane of the centrum) and screws length of C3-C7 were measured.Under direct vision,we strictly inserted pedicle screws according to the results of measurement and evaluated the efficacy by postoperative CT scanning.Results The insertion points for C3 and C4 was 2 to 3 mm beside the centrum median plane and in the opposite of operated pedicle,and 6 to 7 mm from the upper end-plate of centrum plane.The insertion points for C3-C7 were in the same side of operated pedicle,point for C5 1 to 2 mm beside the centrum median plane and 7 to 7.5 mm from the upper end-plate of centrum plane.These parameters for C6 and C7 were 4 to 5 mm and 7.5 to 8.5 mm respectively.The screw insertion direction was outside inclined in cross-sectional plane,and cranially inclined in sagittal plane.The favorable outside inclined angles for C3 or C4,C5 and C6 or C7 were 46 to 47,48 and 36 to 40 respectively.Cranially inclined angles for them were-11 to-7,0 and 8 to 13 respectively.The screw length could be chosen among 28,30 and 32 mm,with a diameter of 3.5 mm.Basing on the relative measurements,we finally inserted 144 screws.Postoperative CT scan showed that all screws had arrived lateral side via anterior insertion into pedicle inside,but there were 16 screws exposure from pedicle lateral cortex,and 3 screws perforating pedicle lateral cortex,which mostly occurred in C3 and C4.Conclusion Lower cervical spine anterior pedicle screw fixation is feasible.