螺旋CT三维重建技术术前重建枢椎椎弓根内固定的钉道轨迹

目的探讨CT三维重建技术术前重建枢椎椎弓根内固定钉道轨迹的方法及其临床意义.方法GELightSpeed 16 Pro螺旋CT扫描完整成人枢椎干燥骨标本15具,在ADW4.2软件上采用容积再现（volume rendering,VR）和多平面重建（multiple planar reformatting,MPR）技术重建和分析图像.在图像工作站中模拟3 mm直径螺钉的经枢椎椎弓根不同方法内固定,观察虚拟螺钉在骨性通道中通行的情况.方法A：进钉点为下关节突根部的中垂线,出至上关节突与齿突交界处.方法B：进钉点为下关节突背侧的头内1/4处,约平行于狭部轴线至上关节突下缘.结果螺钉的轨迹可以从多方位、多角度以及任意3个轴面上得到动态观察.方法A与B两者的钉道长度相近（P＞0.05）;方法A的上倾角度和内倾角度大于方法B（P值分别为0.0381和0.0001）,并有3枚虚拟螺钉穿透横突孔内侧壁,方法B中螺钉均完全在骨性通道中走行,但两者横突孔内侧壁破坏率的差别无统计学意义（P=0.075）.结论CT三维重建技术术前重建枢椎椎弓根内固定可以动态观察螺钉的轨迹是否完全在骨性结构内通行,可以模拟不同进钉点、不同直径的螺钉以及不同角度,在临床治疗和科研中有较大的应用价值.

Technique of helical CT volume rendering in preoperative reformatting C2 pedicle screw trajectory

Objective To study the technique and value of preoperative reformatting C_2 pedicle screw trajectory by helical CT volume rendering.?Methods GE LightSpeed 16 Pro spiral CT scans of 15 dry adult C_2 vertebras were loaded into an imaging station(software ADW4.2).Two methods of C_2 pedicle screw placement were analyzed through virtual pedicle screw trajectory by VR(volume rendering) and MPR(multiple planar reformatting).In method A,the screw entry point was at the intersection between the vertical line and the cranial C_2 inferior facet joint.In method B, the screw trace was from the cranial and medial quadrant of the dorsal part of C_2 inferior facet joint.The virtual pedicle crew trajectories were observed dynamically when they passed through the bone structure.?Results The screw trace could be observed dynamically from all angles of view and all planes.Two vertebras were disqualified for screw fixation,as the isthmus was not high enough and the medial wall of the transverse foramen was too thin.Comparison of virtual screw between method A and method B showed that the angles toward the cephalad(in sagittal plane) and the midline(in transverse plane) in method A were bigger than that in method B(P=0.0381 and 0.0001,respectively),and no difference in vitual screw length between the two methods was noticed(P>0.05).?Conclusions All individual pedicle screw entry points,screw diameters and entry angles can be simulated.The screw trace could be observed dynamically,showing if it transit through the bone structure properly.Preoperative reformatting C_2 pedicle screw trajectory with helical CT volume rendering is of value in clinical and basic researches.