寰椎改良椎弓根螺钉钉道进钉点及进钉角度的影像学测量

Imaging measurement of the entry point and insertion angle of the modified atlas pedicle screw

目的在寰椎CT重建图像上测量以前、后弓和侧块交接点连线方向(改良椎弓根螺钉钉道方向)为进钉角度及以寰椎后弓内缘与侧块交接点为参照标志的椎弓根螺钉最佳的钉道位置。方法选取2015年1月至2017年12月郑州大学第一附属医院行颈椎64层CT平扫的健康成年人97名,包括男48名,女49名,在寰椎横断面上测量以前、后弓和侧块交接点连线方向为内倾角的螺钉钉道可利用间隙宽度,分别与以0°、5°、10°、15°为内倾角时的可利用间隙宽度比较,测量钉道过最宽可利用间隙宽度中内1/3点(改良的椎弓根螺钉钉道位置)时进钉点距寰椎后弓内缘与侧块交接点的水平间距、进钉角度及钉道长度。结果内倾角为0°、5°、10°、15°及与前、后弓和侧块交接点连线方向平行(改良椎弓根螺钉钉道方向)时,随螺钉内倾角的增大,螺钉可利用间隙宽度呈增大趋势,并且两相邻内倾角的螺钉可利用间隙宽度比较,差异有统计学意义(P <0. 05)。男性内倾角为0°、5°、10°、15°、改良椎弓根螺钉内倾角度时所对应的螺钉可利用间隙宽度大于女性,差异有统计学意义(P <0. 05)。男性和女性改良椎弓根螺钉进钉点距寰椎后弓内缘与侧块交接处的水平距离分别为(7. 20±0. 72)、(6. 48±0. 52) mm;以改良椎弓根螺钉进钉点为标志时,男性和女性的螺钉内倾角度分别为(18. 73±2. 58)°、(18. 78±1. 87)°,男性和女性的钉道长度分别为(30. 85±1. 45)、(29. 45±1. 14) mm。男性改良椎弓根螺钉进钉点距寰椎后弓内缘与侧块交接点的水平距离、钉道长度较女性长,差异有统计学意义(P <0. 05)。男、女螺钉最佳内倾角度比较,差异无统计学意义(P> 0. 05)。结论以寰椎后弓内缘与侧块交接点为参照标志,水平向外[男性(7. 20±0. 72) mm、女性(6. 48±0. 52) mm]做纵垂线与寰椎后弓下缘交点正上方2 mm处作寰椎椎弓根螺钉进钉点是安全可行的,内倾角选择改良椎弓根螺钉钉道方向,即与前、后弓和侧块交接点连线平行时是最优的。

Objective In the CT reconstruction image of the atlas, the angle of screw entry was measured when the direction was paralleled to the line passed through the junctions of the anterior arch, the posterior arch and the lateral mass (the direction of the modified pedicle screw) and the optimal position for the pedicle screw was measured by the junction of the posterior arch and the lateral mass as the reference mark. Methods A total of 97 healthy adults who underwent cervical 64-slice CT in the First Affiliated Hospital of Zhengzhou University from January of 2015 to December of 2017 were collected, including 48 males and 49 females. The space available for the transpedicular screw was measured on atlas axis image when the screw path was paralleled to the line which passed through the junctions of the anterior arch, the posterior arch and the lateral mass, which was compared with the space available for the transpedicular screw when the introversion angles were 0°, 5°, 10°, 15° respectively. To measure the horizontal distance from the entry point to the junction which contacted the inner edge of the posterior arch and the lateral mass, and the insertion angle and the length of the screw channel at the inner one third point of the available gap width (the position of modified pedicle screw). Results When the angles of inclination were 0°, 5°, 10°, 15° and paralleled to the line which passed through the junctions of the anterior arch, the posterior arch and the lateral mass, the available gap width of the screw increased with the increase of the angle of inclination, and the available gap widths of the screws with two adjacent angles of inclination were compared, and the differences were statistically significant (P <0.05 ). When the inclination angles were 0°, 5°, 10°, 15° and the modified pedicle screw inclination angle, the available gap widths of the screw of male were larger than those of the female, and the differences were statistically significant (P <0.05 ). The horizontal distances from the entry point to the junction which contacted the inner edge of the posterior arch and the lateral mass in male group and female group were (7.20± 0.72) mm and (6.48±0.52) mm respectively. With the improved pedicle screw entry point as the mark, the screw introversion angles of male and female were (18.73±2.58)° and (18.78±1.87)° respectively, and the lengths of the trajectory of male and female were (30.85±1.45) mm and (29.45±1.14) mm respectively. The horizontal distance from improved pedicle screw entry point to the junction which contacted the inner edge of the posterior arch and the lateral mass in male group was longer than that in female group, and the length of the trajectory in male group was longer than that in female group, while the differences were statistically significant (P <0.05 ). There was no statistically significant difference in the best internal inclination angle between male and female group (P >0.05 ). Conclusion To use the intersection point between the inner edge of the posterior arch of atlas and the lateral mass as a reference sign to make the vertical line horizontal outward, while (7.20±0.72) mm in male and (6.48±0.52) mm in female, it is safe and feasible to use the point as the pedicle screw entry point which was 2 mm above the connection point between the vertical line and the intersection point of the lower edge of the posterior arch of atlas. It is optimal when the screw introversion angle parallel to the line which passes through the junctions of the anterior arch, the posterior arch and the lateral mass (the direction of the modified pedicle screw).