枢椎以横突后支与下关节突交界处为解剖标志行椎弓根置钉的应用解剖研究

Cadaveric study on axis anatomic landmark featured by the junction between lateral border of inferior articular process and posterior branch of transverse process for C2 pedicle screw fixation

中文关键词:  枢椎  椎弓根螺钉  解剖学

英文关键词:Axis  Pedicle screw fixation  Anatomy

中文摘要:

  【摘要】 目的：探讨枢椎以横突后支与下关节突交界处为解剖标志行椎弓根置钉的可行性，为临床应用提供参考。方法：30具湿性成人颈椎尸体标本，显露并以枢椎横突后支与下关节突外侧缘交界处作为参照点标志。经该解剖标志作水平线，以椎弓根内、外侧缘与侧块交界处连线的中点作纵垂线，以两线的交点偏外1～2mm处为进钉点。分别测量枢椎横突后支的宽度，进钉点与该解剖标志、C2神经根、横突孔内下壁和椎管内侧壁的距离。取上述进钉点，经枢椎双侧椎弓根以内倾角25°～30°、头倾角20°～25°共置入60枚螺钉，再行CT扫描观察钉道的完整性，测量置入螺钉的内倾角和头倾角，统计螺钉偏置率。结果：所有解剖参数及螺钉角度左、右侧比较差异均无统计学意义（P＞0.05），双侧数据合并后计算总体平均数值。枢椎横突后支的宽度为5.13±0.15mm，进钉点与解剖标志、C2神经根、横突孔内下壁和椎管内侧壁的距离分别为5.73±0.62mm、4.04±0.21mm、5.32±0.49mm和4.94±0.38mm。螺钉内倾角和头倾角分别为28.4°±3.1°和22.5°±2.9°。60枚螺钉中，共有4枚螺钉偏置进入横突孔或椎管，螺钉偏置率为6.7%（4/60）；4枚螺钉过长穿破椎体前缘骨皮质。结论：枢椎以横突后支与下关节突交界处作为椎弓根置钉进钉点的参照点解剖标志是可行的，但因解剖差异仍存在螺钉误置的可能。

英文摘要:

  【Abstract】 Objectives: To describe the feasibility of C2 pedicle screw fixation by means of axis anatomic landmark confirmed by the junction between lateral border of inferior articular process and posterior branch of transverse process, and to provide a reference for its clinical practice. Methods: Morphometric measurements and radiological techniques were implemented in 30 adult embalmed cadaveric specimens. The junction between lateral border of inferior articular process and posterior branch of transverse process in axis was exposed to serve as anatomic landmark. The entry point of C2 transpedicular screw fixation was determined as 1-2mm lateral to the crossing point of two lines, a horizontal line through the anatomic landmark, and a vertical line through the midpoint of distance from the junction of pedicle medial and lateral border to lateral mass. The next five anatomic parameters were measured separately,including the width of posterior branch of transverse process, the distance from entry point to anatomic landmark, C2 nerve root, the inner and inferior wall of transverse foramen, the medial wall of vertebral canal. Finally, the total of 60 pedicle screws were inserted at the entry point with an angle of 25°-30° medial to the sagittal plane and 20°-25° superior to the axial plane. A 3-dimensional computed tomogram was checked ostoperatively to evaluate screw placement and to verify its angulation. Results: No statistical differences were found in all of anatomic parameters and screw angulations between left and right side(P＞0.05). Therefore, the overall mean data were gained by means of bilateral summation. The overall mean width of posterior branch of transverse process was 5.13±0.15mm. The overall mean distance from entry point to anatomic landmark, C2 nerve root, transverse foramen and vertebral canal was 5.73±0.62mm, 4.04±0.21mm, 5.32±0.49mm and 4.94±0.38mm respectively. The averaged screw angles specified as 28.4°±3.1° medially and 22.5°±2.9° superiorly. There were four screws shown to extend into transverse foramen and vertebral canal. The incidence of screw malposition was 6.7%(4/60). Moreover, four screws excess over the length of pedicle. Conclusions: The study shows that anatomic landmark stated above has definite assistance in locating the C2 entry point to achieve pedicle screw fixation. However, there still be a potential of screw malposition due to anatomic variation.