寰椎后弓交叉螺钉置入相关参数的三维CT分析

Parameters of cross screw placement of posterior arch of atlas using three-dimensional computed tomography

目的应用CT三维重建测量技术对寰椎后弓交叉螺钉置入的相关参数进行测量,研究影响置钉的解剖结构因素。方法从2018年9月至2019年5月于福建省立医院行头颈CT血管造影扫描的患者中选取头颈部未见异常者305例,利用其CT影像数据进行寰椎三维数字化重建,测量寰椎后弓交叉螺钉置钉相关的解剖学数据,并分析寰椎后弓交叉螺钉固定的解剖限制性因素。结果寰椎后结节中央高度值为(9.53±1.67)mm,其中小于7mm的占6.2%,距中线5mm、10mm、15mm处后弓高度分别为(8.53±2.05)mm、(6.91±1.82)mm、(4.53±1.45)mm,其中小于3.5mm的分别占4.4%、11.5%、18.9%,寰椎后结节中央宽度为(7.51±1.82)mm,距中线5mm、10mm、15mm处后弓宽度分别为(7.03±1.53)mm、(6.51±1.27)mm、(6.63±1.05)mm,其中小于3.5 mm的分别占4.3%、5.7%、5.2%。寰椎后弓交叉螺钉置钉点位于后中线旁开左侧为(2.98±0.65)mm,右侧为(3.07±0.88)mm,理想钉道长度左侧为(17.78±2.65)mm,右侧为(17.37±2.48)mm,钉道的外展角为左侧(27.65±7.36)°,右侧(26.84±7.64)°。不同性别和身高层次之间长度测量值差异有统计学意义(P<0.05),但钉道外展角差异无统计学意义。结论寰椎后弓高度和宽度为后弓交叉螺钉固定的主要解剖限制性因素,钉道长度小于15mm有利于避免螺钉穿破后弓骨皮质,减少对椎动脉的损伤,术前应通过CT测量获得准确的个体化置钉参数。

Objective To measure the relevant parameters of cross screw fixation in the posterior arch of atlas using three-dimensional computed tomography(CT)reconstruction.Methods 305 patients were selected to undergo three-dimensional digital reconstruction of atlas.No abnormalities in the head and neck were confirmed by CT angiography.The anatomical data were collected to analyze the limiting factors of cross screw fixation of posterior arch of atlas.Results The central height of the posterior tubercle of atlas was(9.53±1.67)mm,of which 6.2%was less than 7mm.The height of posterior arch at the distance of 5mm,10mm and 15mm from the midline was(8.53±2.05)mm,(6.91±1.82)mm and(4.53±1.45)mm,respectively,of which 4.4%,11.5%and 18.9%were less than 3.5mm.The central width of the posterior tubercle of atlas was(7.51±1.82)mm.The widths of the posterior arch at 5mm,10mm and 15mm from the midline were(7.03±1.53)mm,(6.51±1.27)mm and(6.63±1.05)mm,respectively,of which 4.3%,5.7%and 5.2%were less than 3.5mm.The point for screw placement in the posterior arch of atlas was(2.98±0.65)mm at the left side of the posterior midline opening,and(3.07±0.88)mm at the right side of the posterior midline opening.The ideal screw length was(17.78±2.65)mm at the left side,and(17.37±2.48)mm at the right side.The abduction angle of the nail path was(27.65±7.36)°at the left side,and(26.84±7.64)°at the right side.The length parameters across different genders and age groups were statistically significant,whereas the abduction angle of the screw trajectory was not.Conclusion The height and width of the posterior arch of the atlas are the main anatomical limiting factors for cross screw fixation in the posterior arch.The screw length less than 15mm is beneficial to preventing the screw from penetrating the posterior arch cortex and reducing the injury to the vertebral artery.Preoperative CT measurement should be used to obtain accurate and individualized parameters of screw placement.