短节段钉钩结合脊柱内固定的生物力学研究

Biomechanical study of short seg-ment pedicle screw and hook combined with spinal internal fixation

目的 设计短节段椎弓根钉与椎板钩结合使用的脊柱内固定方法 (modifiedcotrel duboussetinstrumentation ,MCD) ,比较MCD、CD、RF、Steffee、Dick在胸腰椎骨折固定中的力学效果。方法 用 7具人尸胸腰段标本 ,按Panjabi方法制作骨折模型 ,分别安放 5种固定器 ,利用生物力学的电测实验应力分析方法测试固定后脊柱的强度、刚度、扭转强刚度和极限强度。结果 MCD较CD固定后骨折椎上应力减小 31 % ,位移下降 32 % ,脊柱的轴向刚度、弯曲刚度和扭转刚度分别提高38%、2 6%和 2 5% ,整个结构承载能力提高 2 0 % ,差异均有非常显著性 (P <0 .0 1 )。与其他 3种固定方法相比 ,各项测试指标差异均有非常显著性 (P <0 .0 1 )。结论 短节段钉钩结合内固定符合生物力学原理 。

Objective\ To design a new method that used short segment pedicle screws and hooks combined with spinal internal fixation (modified cotrel dubousset, MCD), and compare the biomechanical effects of 5 short segment transpedicular internal fixation systems: MCD, CD, RF, Steffee, Dick. Methods \ Seven cadaveric thoracolumbar spinal specimens were harvested to imitate thoracolumbar fracture according to Panjabi method. Biomechanical tests of stability were performed by measuring spinal strength, stiffness, torsional rigidity and load to failure after 5 different instruments were placed respectively. Results \ Strain, stress and displacement in MCD was increased by 31% and 32% respectively, while axial stiffness, laterial bending stiffness, torsional regidity and the ability of load was increased by 38%, 26%, 25% and 20% respectively, as compared with those in CD ( P <0.01). There was significant difference in all indices between MCD and any of other three instruments ( P <0.01). Conclusion\ The method of pedicle screws and hooks in short segment combined with for spinal internal fixation accords with the principle of biomechanics and has a better biomechanical stability.\;