寰椎椎弓根骨性标志的应用解剖学研究

Anatomical study of bone landmark of atlas pedicle

目的:研究寰、枢椎旋转脱位或二者间有较大移位时确定寰椎椎弓相关骨性标志,为术中定位寰椎椎弓根提供解剖学依据。方法:100具寰椎干燥标本,标记寰椎椎弓根轴线(M线),采用游标卡尺和量角器测量M线与寰椎椎弓根上方及内外侧骨性标志的各相关参数,并采用尸体标本进一步验证寰椎椎弓根骨性标志的定位效果。结果:寰椎椎弓根轴线内倾角平均(17.67°±4.21°),进钉点距寰椎后弓后侧皮质与后正中线的交点间距平均(25.00±2.33)mm,距横突外缘平均(22.33±2.77)mm。寰椎上关节突后凸尖较为突出,其下的骨质弧形隆起,经此弧形隆起顶点的垂线与上关节突后凸尖的垂线基本重叠,上关节突后凸尖的垂线与M线在后弓处的重叠率左侧为48%,右侧为65%,其余的垂线均位于M线外(0.89±1.16)mm。出钉点位于M线与侧块前缘相交处的侧块前缘垂线的中点,左右出钉点连线(BB线)与前结节顶点有36%的重叠率,其余前结节顶点大部位于BB线下(3.37±1.80)mm。结论:寰椎后结节中点及上关节突后凸尖下的骨质隆起的顶点可作为寰椎椎弓根螺钉进钉点的准确标志,上关节突后凸尖及横突尖可作为寰椎椎弓根螺钉进钉点的大体标志;沿寰椎椎弓根轴线进钉较为安全,内倾17.67°,仰角变异大,出钉参照寰椎前结节顶点。

Objective： To set up a safe axes （M line） of atlas pedicle when an atlas pedicle was inserted a screw and to provide the anatomical basis about anatomical landmark of atlas pedicle in the course of operation when atlan toaxis existed a rotatory dislocation or obvious separation from each other. Methods： One hundred dry atlas speci mens were measured to get the parameters about the M line and the superior, medial and lateral anatomic landmarks of the atlas pedicle by using a digital caliper and a goniometer after marked M line. The results of the measurement were checked by experiment of cadaveric specimens. Results： The angulation of the pedicle axes of atlas relative to sagittal plan was 17.67°±4.21°. The entrance point of screw was （25.00±2.33） mm to the junction of the posterior arch and posterior median line. The entrance point of screw was （22.33±2.77） mm to the lateral edge of transverse process. The posterior convexity of superior articular surface of atlas was protrusion and a bulge of bone cortex under the posterior convexity was protrusion. The peak of the bulge accorded with the vertical line through the posterior convexity of the superior articular surface of atlas. The superimpose rate of the vertical line with the M line were 48% to left and 65% to right. The surplus existed in 0.89±1.16 mm to the M line. The exit point of screw was in the median point of vertical line of lateral mass. The superimpose rate of the line （BB line） linked the exit points of screw with anterior tubercle was 36 %. The surplus of anterior tuberle existed in 3.37±1.80 mm under BB line. Conclusions： The median point of posterior tubercle and the peak of the bulge can be as accurate landmarks. The posterior convexity of the superior articular surface of atlas and transverse process of atlas can be as relative landmarks. It was safe that inserting a screw accorded with the atlas axes relative to sagittal plane 17.67°. The exit point of screw should refer to anterior tubercle because the angle relative to the coronal plane existed variation.