寰枢椎后路钉棒系统交叉棒固定及平行棒固定的生物力学稳定性

Biomechanical stability of crossed-rod fixation and parallel-rod fixation of atlantoaxial posterior screw-rod system

背景:前期研究证明交叉棒在由C_(1)椎弓根螺钉与C_(2)一侧椎弓根螺钉/另一侧椎板螺钉组成的寰枢椎后路钉棒系统中能增加其旋转稳定性。因此推测,寰枢椎后路交叉棒固定可能是一种简单有效的新型内固定结构框架,无论是在与C_(2)双侧椎板螺钉还是双侧椎弓根螺钉组成的钉-棒系统中,交叉棒的连接方式与传统平行棒相比较,都可能进一步增强其结构的生物力学稳定性。目的:评价C_(1)双侧椎弓根螺钉分别和C_(2)双侧椎弓根螺钉、C_(2)双侧椎板螺钉组成钉-棒系统的生物力学稳定性。方法:6例新鲜寰枢椎脱位标本,完成完整状态和失稳状态的测量后,每一例标本均置入C_(1)双侧椎弓根螺钉、C_(2)双侧椎板螺钉、C_(2)双侧椎弓根螺钉,按顺序分别测量C_(2)双侧椎板螺钉平行棒固定、C_(2)双侧椎板螺钉交叉棒固定、C_(2)双侧椎弓根螺钉平行棒固定和C_(2)双侧椎弓根螺钉交叉棒固定的后伸前屈、左/右侧屈、左/右旋转活动度。结果与结论:①4种内固定方式在屈伸、侧屈、旋转方向上,与正常状态下和失稳状态下相比较,差异均有显著性意义(P<0.05);②C_(2)双侧椎弓根螺钉组成的钉-棒系统,无论是交叉棒还是平行棒连接方式,稳定性均强于由C_(2)双侧椎板螺钉组成的钉-棒系统;③而交叉棒固定可增强由C_(2)双侧椎板螺钉组成的钉-棒系统的后伸、左/右侧屈、左/右旋转的稳定性,以及由C_(2)双侧椎弓根螺钉组成的钉-棒系统在旋转方向上的稳定性;④因此交叉棒固定方式可进一步提升寰枢椎后路钉棒系统的生物力学稳定性,可作为临床应用的选择。

BACKGROUND:Preliminary study has shown that the crossed rod fixation of the short segment screw rod fixation system composed of C_(1) bilateral pedicle screws and C_(2) unilateral lamina screw can increase its axial rotation stability.Therefore,posterior atlantoaxial crossed rod fixation may be a simple and effective new internal fixation framework.Whether in the screw rod system composed of C_(2) bilateral lamina screws or bilateral pedicle screws,the connection mode of crossed rod may further enhance the biomechanical stability of its structure compared with the traditional parallel rod.OBJECTIVE:To evaluate the biomechanical stability of the fixation technique for the crossed rod and parallel rod by the C_(1) bilateral pedicle screws combined with C_(2) bilateral lamina screws or bilateral pedicle screws.METHODS:Six fresh adult craniocervical specimens were used to test the biomechanical stability.Following intact state and under destabilization testing,C_(1) bilateral pedicle screws,C_(2) bilateral lamina screws and bilateral pedicle screws were implanted in each specimen.The specimens were then tested in the following sequence:C_(2) bilateral laminar screws+parallel rod,C_(2) bilateral laminar screws+crossed rod,C_(2) bilateral pedicle screws+parallel rod,and C2 bilateral pedicle screws+crossed rod.The ranges of motion of the C_(1-2) segments were measured in flexion-extension,lateral bending,and axial rotation.RESULTS AND CONCLUSION:(1)The four fixed modes significantly increased stability compared with both the intact and destabilization group in flexion-extension,lateral bending,and axial rotation(P<0.05).(2)When C_(2) was implanted with bilateral pedicle screws,whether crossed rod or parallel rod connection was stronger than that composed of C_(2) bilateral lamina screws.(3)The crossed rod fixation could enhance the stability of the internal fixation system composed of C_(2) bilateral lamina screws in extension,lateral flexion and rotation,and the stability of the screw rod system composed of C_(2) bilateral pedicle screws in the direction of rotation.(4)Therefore,crossed rod fixation can further improve the biomechanical properties of atlantoaxial posterior screw-rod system and can be used as a choice for clinical application.