采用“漏斗技术”植入椎弓根螺钉固定胸段脊柱的生物力学研究

Biomechanical study on thoracic spine segment fixed by pedicle screws placed with "funnel technique"

目的研究用"漏斗技术"植入椎弓根螺钉对固定胸段脊柱生物力学性能的影响。方法采集成人胸节段脊柱(T6～T10)标本14具。将这些标本分为两组,每组7具,分别用"漏斗技术"和Magerl技术作椎弓根螺钉固定。对完整和固定的脊柱标本分别测量各种体位下的位移刚度、包括纵向压缩、前屈、后伸、左右侧屈及轴向旋转,并测量椎弓根螺钉的拔出强度。结果与完整脊柱段相比,两种技术内固定均使脊柱标本的位移刚度明显增加(P<0.05),但这两种技术间无显著差异。用"漏斗技术"固定的螺钉拔出强度明显低于Magerl法固定(P<0.05)。结论由于"漏斗技术"咬除了椎弓根后侧部分骨质,可提高置钉的准确性和安全性。虽然该技术对固定脊柱的刚度无显著影响,但可降低螺钉的锚固强度。因此,我们建议将其作为胸椎椎弓根螺钉固定的一种补充方法。

Objective To investigate mechanical properties of the thoracic spine fixed with pedicle screws that were placed using a ＂funnel technique＂. Method Fourteen thoracic spinal segments （T6 to T10） were collected from adult cadavers. These specimens were divided into two groups,7 in each,and fixed with pedicle screw using funnel and Magerl techniques. The displacement stiffness of the spinal segment and the pull-out strength of the pedicle screw were tested for intact and fixed spinal specimens. The displacement stiffness was measured from different loading directions,including axial compression,anterior flexion,posterior extension,lateral bending and axial torsion. Results Compared to the intact spine segments,the displacement stiffness is significantly increased （P〈0.05） at all directions in the segments fixed with either funnel or Magerl technique; however,there is no significant difference between the groups fixed with different technique. The screw pull-out strength is significantly decreased （P〈0.05） in spine segments fixed with Funnel technique compared to those fixed with Magerl technique. Conclusions Since funnel technique removed a portion of bone from the posterior side of the vertebral pedicle,it can raise the accuracy and safety for the placement of pedicle screw. Although this technique does not affect the stiffness of fixed spinal segment,it may decrease the anchor strength of pedicle screw. Accordingly,we recommend that the funnel technique can be considered as a complement method for the fixation of vertebral fracture using pedicle screws.