下颈椎椎弓根螺钉置入有限开放技术的实验研究与初步临床应用

目的 评价有限开放技术在置入下颈椎椎弓根螺钉中的安全性和准确性.方法 新鲜尸体20具,利用有限开放技术对C_3～C_7椎弓根置入199枚螺钉,评价螺钉的位置;解剖观察C_3、C_4共40椎、80侧椎弓根管入口形状结构,并测量与钉道位置相关的参数.临床应用7例,在侧块外上限刮除有限松质骨开窗,暴露侧块和椎弓根内侧骨皮质移行部,确定进钉点.参照X线片和CT测量的角度,用自制单刃圆头探针准备钉道,置入螺钉29枚,术后通过X线和CT扫描评估螺钉位置.结果 C_3、C_4侧块深层皮质骨和椎弓根内侧皮质骨汇合成椎弓根入口内侧,形成向外突起的弧状面,骨质厚实坚硬,未发现有滋养血管孔.钉道入针点分布在侧块外上限,侧块表面的开口直径平均5.2 mm,椎弓根入口宽度平均7.5 mm,钉的内倾角为42°,上倾10°.置钉准确率在标本中为94.5%,临床为100%.结论 在侧块表面有限开窗,暴露侧块和椎弓根移行部,作为下颈椎椎弓根螺钉置入的标志,结合单刃圆头探针进行置钉,是一种安全性高、创伤小、准确率高的下颈椎椎弓根螺钉置入技术.

Subaxial cervical pedicle screw placement using limited opening technique: experimental study and preliminary clinical report

Objectives To evaluate the safety and accuracy of limited opening technique for traspedicular screw placement in subaxial cervical spine. Methods Twenty fresh cervical specimens (C_3-C_7) were included in this study and placed with 199 pedicle screws using limited open technique for evaluation of the location of the screws. Forty C_3-C_4 specimens (80 sides) were used to observe architec-ture of the cervical pedicle and measure parameters related with screw placement. Seven patients with cer-vical instability were treated with pedicle screw fixation (29 screws) using this limited open technique.The cancellous bone in the junction of lateral mass and medical wall of pedicle was removed to find the in-let of the pedicle. The pedicle screws were inserted according to the measurement results of CT and X-ray. The patients were then evaluated radiographically for the location of the pedicle screw. Results The key structure safely leading into the pedicle was the junction between deep cortex of C_3、C_4 lateral mass and medial wall of the pedicle, which was located at the lateral upper quadrant of the lateral mass,with hard contour surface but without nutrient foramens. The screw insertion points were distributed at lat-eral upper quadrant of the lateral mass, with mean debouchement diameter of 5.2 mm, mean inlet width of 7.5 mm, medial angle of 42°and upward angle of 10°. The accuracy rate of screw placement was 94.5% in specimens and 100% in patients. Conclusion Limited opening at lateral mass surface combined with single-blade blunt end probe is proved to be a safe and accurate technique for subaxial cer-vical pedicle screw placement.