寰椎椎弓根与枢椎侧块关系的解剖与临床研究

Anatomic and clinical evaluation of the location relation between C1 pedicle and C_2 lateral mass

目的研究寰椎椎弓根与枢椎侧块的位置关系,建立以枢椎侧块为解剖标志的寰椎椎弓根螺钉进钉定位技术,并通过临床应用评价其可靠性。方法取50套干燥寰枢椎标本,测量寰椎椎弓根和枢椎侧块的内缘、中点(内、外缘中点)、外缘与正中矢状线的垂直距离,计算寰椎椎弓根与枢椎侧块的内缘间距、中点间距和外缘间距,建立寰椎椎弓根螺钉进钉定位技术。临床应用该定位技术进行后路寰椎椎弓根螺钉固定治疗寰枢椎不稳患者6例,男5例,女1例;平均年龄41岁。其中游离齿突1例,齿突发育不良3例,齿突陈旧性骨折2例。结果寰椎椎弓根的内缘、中点、外缘分别在枢椎侧块的内缘、中点、外缘的内侧(1.37±0.51)mm、(1.60±0.61)mm、(2.15±0.60)mm处。确定寰椎椎弓根螺钉的进钉点为:经枢椎侧块内、外缘的中点作纵垂线,与寰椎后弓上缘交点的正下方3.0mm处。6例患者共放置寰椎椎弓根螺钉12枚,术中无脊髓和椎动脉损伤等并发症,术后X线及CT扫描显示螺钉位置均良好。结论枢椎侧块与寰椎椎弓根间存在较恒定的解剖位置关系,枢椎侧块可作为术中确定寰椎后弓显露范围和判断寰椎椎弓根螺钉进钉点的解剖学标志,可简化术中繁琐的定位操作。

Objective To study the relevant position of atlas pedicle to axis lateral mass, set up a technique of C1 pedicle screw placement with the lateral mass of axis as an anatomic landmark, and evaluate the reliability of the present screw placement technique by clinical practice. Methods 50 paired atlas and axis specimens were used to measure the distance from the sagittal midline to the medial border, the midpoint (the middle point of the mediolateral border) and the lateral border of C1 pedicle and C2 lateral mass. Furthermore, the distance between the medial border of C1 pedicle and that of C2 lateral mass, the distance between the midpoint of C1 pedicle and that of C2 lateral mass and the distance between the lateral border of C1 pedicle and that of C2 lateral were calculated respectively. The technique of C1 pedicle screw fixation was established. Using the present landmark technique, C1 pedicle screws were placed in 6 patients of atlantoaxial instability, including 5 males and 1 female averaged 41 years old, with os odontoideum in 1, odontoid hypoplasia in 3, and old odontoid fractures in 2. Results The medial border, the midpoint and lateral border of C1 pedicle was averaged (1.37±0.51) mm, (1.60±0.61) mm and (2.15±0.60) mm medial to C2 lateral mass, respectively. The entry point of C1 pedicle screw in present technique was defined as the method of making a vertical line through the midpoint of C2 lateral mass, and the entry point was 3 mm under the cross point of the superior rim of C1 posterior arch with the vertical line. 12 C1 pedicle screws were placed exactly in all 6 patients, and no neural or vascular injury was observed. The postoperative radiographs and CT scans verified all of C1 screws with a good position. Conclusion There is a steady anatomic relation between C1 pedicle and C2 lateral mass, the C2 lateral mass could be as a convenient anatomic landmark to determine the location of C1 pedicle and the position of C1 pedicle screw entry point.