腰椎椎弓根螺钉进钉点个体化X线片定位法

Individualized Localization of the Lumbar Pedicle Screw Entrance Points by the X-ray Film

目的介绍一种简易有效并体现个体化的椎弓根螺钉进针点定位方法。方法取5具附带躯干的腰椎脊柱标本(L1～5),摄取X线正位片,以椎弓根投影水平中线和投影外缘交点作为最佳进钉点,测量最佳进钉点距离同椎体横突上缘和椎板外缘的垂直距离。L5椎弓根外缘和椎板边缘投影欠清,定位参照L4椎板外缘,并在L5椎弓根投影内缘旁开10mm。按照常规后路入路暴露相关解剖结构,测量并确定进钉点,模拟打入椎弓根螺钉,随后解剖出每个椎体的椎弓根,观察预设的进钉点位置和椎弓根螺钉位置。结果各椎体椎弓根解剖显示预设的椎弓根螺钉进钉点选址良好。50枚椎弓根螺钉中,1枚轻微挤裂L1椎弓根内壁,椎弓根内壁骨折,螺钉没有露出;1枚轻微挤裂L1椎弓根外壁,螺钉没有露出;还有1枚轻微穿破L2椎弓根外壁,螺钉露出少许螺纹。整体穿破率为6%,L1椎弓根穿破率为20%。结论参照腰椎正位X线片上椎弓根投影与椎板外缘和横突上缘的关系来确定椎弓根螺钉进钉点是一种简易有效的个体化定位方法。

Purpose To introduce a simple and individualized method to localize the entrance point of the lumbar pedicle screws by X-ray film. Methods Anterior-posterior views of the X-ray film were taken on 5 cadaveric spine （L1-5） with intact soft tissue. The intersection point of the pedicle projection＇ s horizontal midline and lateral margin tangent line was determined as the optimal entrance point. On the X-ray film, the distance from the optimal entrance point to the correspondence superior margin of the transverse process, and to the lateral margin of the laminae was measured （X-ray had 10 % magnification）. In case of unclear projection of the lateral margins of the L5 laminar and pedicle, L4 laminal lateral margin and medial margin of L5 pedicle were selected as localization marks, point about 10 mm lateral to the medial margin of L5 pedicle projection was defined as entrance point. Then the posterior structures were exposed, the optimal entrance point was determined by the localization marks,the pedicle screws was entered （5.5 mm screw diameter）. In the last,every pedicles were dissected for investigating the entrance points and the placement of the screws. Results All pedicle screw entrances were acceptable. Among 50 screws,one screw split slightly the inner wall of the L1 pedicle,one split slightly the outer wall of the L1 pedicle, and the other one screw split outer wall the L2. pedicle, the screw thread could be seen. The total misplacement rate was 6 % , and 20 % in LI. Conclusions The projection of the lumbar pedicle on the X-ray film and its relationship with the superior margin of the transverse process and lateral margin of the laminae could be selected as individualized reference marks to localize the optimal entrance point for the lumbar pedicle screw.