寰椎骨折前路复位内固定钢板置钉参数研究

目的　明确寰椎骨折前路复位内固定钢板寰椎侧块置钉可行性及置钉技术参数。 方法　用Mimics软件，对40例被检查者的CT数据进行三维重建，解剖测量，并模拟置入寰椎侧块螺钉，测量并获得置钉的技术参数。 结果　椎动脉孔内侧壁距离中线23.2 mm。寰椎后弓与寰椎侧块移行处内侧壁距离中线距离13.2 mm。寰椎侧块上位螺钉置钉点距离上关节面前缘6.2 mm，距离寰椎中线20.0 mm。上位螺钉长21.5 mm，于矢状面上成角范围向上1.5°～向下11.6°。寰椎侧块下位螺钉置钉点距离下关节面前缘8.9 mm，长15.2 mm，最大下倾角为20.7°，距离椎动脉孔内侧壁1.9 mm。距中线17.6~23.2 mm的侧块为JeRP钢板侧块螺钉置入的相对安全区域。 结论　寰椎侧块置入上下位螺钉具备可行性。置钉点及钉道方向必须根据患者术前的三维CT数据做最终的决定。上位螺钉置钉角度应宁下勿上，下位螺钉置钉角度应宁内勿外。

Study of technical parameters of C1 lateral screws placement in Jefferson-fracture reduction plate

Objective　To clarify the technical parameters of C1 lateral mass screw in anterior Jefferson-fracture reduction plate. 　Methods　Anatomic structure of C1 lateral mass using 1-mm CT scans were measured with MIMICS software in 80 C1 lateral mass of 40 cases. 2 entry points were selected for superior and inferior screw placement and screws (2.5mm in diameter) , and simulation procedure was performed at these entry points. Length, angle of screw and relation with adjacent anatomical structures were recorded.　Results　Distance from medial wall of vertebral artery hole to midline of atlas was 23.2 mm. Distance between medial wall of posterior arch junction with lateral mass and midline was 13.2 mm, and from entry point of superior screw to anterior edge of superior articular and midline were 6.2mm, 20.0mm respectively. The length of superior screw was 21.5 mm and the range of sagittal angulation was upward 1.5° to downward 11.6°. Distance from entry point of inferior screw to anterior edge of inferior articular was 8.9mm. Length of inferior screw was 15.2mm. The largest downward angulation for inferior screw was 20.7°. Distance from medial wall of vertebral hole to inferior screw was 1.9mm. The area of lateral mass (17.6~23.2) mm away from midline of atlas is relative safe for screw placement.　 Conclusions　It is feasible to place C1 lateral mass screws (superior and inferior screw) in anterior Jefferson-fracture reduction plate. Making final decision of entry points and screw direction must depend on preoperative 3-dimensional CT evaluation. According to our research, the angulation of superior screw below turn to downward, and the angulation of inferior screw turn to inside were recommended.