膨胀式脊柱椎弓根螺钉固定的生物力学研究

目的:测试膨胀式椎弓根螺钉(expansivepediclescrew,EPS)的骨-器械界面强度及耐疲劳强度,评价EPS的脊柱后路固定强度。方法:100个新鲜小牛腰椎随机分成A、B、C三组,以USS,Tenor,CDH螺钉为对照螺钉,分别对EPS进行最大旋出力矩实验、轴向拔出实验和翻修实验,记录最大旋出力矩(Tmax)、最大轴向拔出力(Fmax)和翻修后最大轴向拔出力。并在超高分子聚乙烯材料上对螺钉进行150万次的周期载荷疲劳实验。结果:EPS的Tmax、Famx显著大于三种对照螺钉(P<0.01)。EPS翻修时的Fmax亦显著高于对照螺钉(P<0.05)。150万次周期载荷疲劳实验完成后,四种螺钉均未出现疲劳折断现象。结论:EPS较目前常使用的非膨胀椎弓根螺钉有更好的脊柱固定作用及翻修性能,其耐疲劳强度与其它三种螺钉相当。

Biomechanical evaluation of an expansion pedicle screw (EPS) in calf vertebrae

Objective:To measure the strength of bone-screw interface of the newly-designed expansion pedicle screws(EPS) in calf lumbar spine,and to evaluate the biomechanical effectiveness of EPS.Method:100 fresh calf lumbar vertebrae were randomly classified into group A,B,C.In comparing with USS,Tenor and CDH screws,the turn-back testing,pull-out testing and revision testing were performed in group A,B,C respectively.The maximum turning-back torque(Tmax) and axial pullout strength(Fmax) were recorded.Fatigue testing was performed on ultra-high molecular weight polyethylene blocks served as vertebral elements in a corpectomy model.Result:The Tmax and Fmax of EPS screws was significantly greater than USS,Tenor and CDH screws.In revision testing,the Fmax of the EPS were higher than the three control screws significantly (P<0.05).No screws were broken or bent at the end of fatigue testing.Conclusion:Expansion pedicle screws can significantly improve the bone fixation and the pullout strength compared to USS,Tenor and CDH screws.The fatigue characteristic of EPS is similar to CDH,USS and Tenor screws.