下颈椎后路三种内固定稳定性的生物力学测试和评价

Biomechanical Test and Assessment on three Internal Fixations on Spine Subaxial Cervical

目的:评价下颈椎椎板减压后应用经关节突钢丝植骨、侧块螺钉钢板、椎弓根螺钉钢板的稳定性,为临床选择恰当的内固定提供理论依据。方法:取5具新鲜尸体的颈椎(C3～C7)为标本,于C4～C5行全椎板减压术,造成下颈椎不稳定模型。然后依次行经关节突钢丝植骨、侧块螺钉钢板、椎弓根螺钉钢板等三种内固定技术。在2.0Nm纯力矩下进行柔韧性实验,检测C4～C6在前屈后伸、左右侧弯的运动范围(用位移表示),左右旋转8°的扭矩(计算出刚度)。所得数据进行组间比较的T检验,评价三种内固定技术的稳定效果。结果:在前屈后伸方面,椎弓根螺钉和侧块螺钉钢板没有明显区别;椎弓根螺钉左右旋转的刚度最强;经关节突钢丝植骨在侧弯方向和侧块螺钉没有明显差异,在其它方向的稳定性较差。结论:尽管椎弓根螺钉内固定仍有一定的技术难度,和其他两种内固定相比,其有较高的稳定性。从生物力学的角度来看,下颈椎不稳应用椎弓根螺钉固定是恰当的选择。在椎板减压情况下,侧块螺钉固定可满足临床的需要。经关节突钢丝植骨的稳定性较差。

To evaluate the primary stabilities of 3 different instrumentations in the subaxial cervical spine and to provide a theory basis for the selection internal fixations reasonably in clinical. Methods： Five fresh human cadavers cervical specimens（C3～C7） were loaded nondestructively with 2.0Nm pure moments. A decompression laminectomy instability was created in C4～C5 and the motion at C4～C6 was measured in nexion extension,lateral bending,and axial rotation. The five specimens were instrumented by the following fixation techniques, respectively, 1. the intact state 2. after the C4～C5 decompression laminectomy 3. facet wiring with bone graft 4. lateral mass screws. 5. pedicle screws. Data analysis was per formed by calculating the ranges of motion,and statistical differences were determined by the test for group comparison. Resuits： No significant difference was observed in nexion-extension between pedicle screws and lateral mass screws. Pedicle screw showed a significantly higher stabilitv in torsion. No difference was found between facet wiring with bone graft and lateral mass screws in lateral bending, in other load directions the stability was even worse. Conclusions： The major investigation of the current study was the higher stability of pedicle screws over lateral mass fixation and facet wiring with bone graft with respect to primary stability and stability. From the biomechanical point of view the use of pedicle screws in the subaxial cervical spine seems justified. In decompression laminectomy, lateral mass screws could meet the need in clinics. The stability of facet wiring with bone graft was worse.