椎弓根螺钉器械应力分析

Analysis of the stress of pedicle screw instrument

目的 测试椎弓根螺钉器械受力状态 ,为脊柱内固定器械的研制及应用提供理论依据。方法 利用聚酰胺棒加工成人工椎体模型 ,将椎弓根螺钉器械植入椎体模型 ,模拟脊柱最不稳定状态———椎体完全缺失且无韧带影响 ,在试验机上以 5 0N的增幅逐渐增加载荷 ,记录不同载荷下的前屈应变值 ,计算器械在轴向压力及弯矩下的应变值。结果 弯曲受拉应变值明显高于弯曲受压应变值 ;弯矩应变值明显高于轴向压力应变值。在相同的载荷下SDR的应变值明显低于VSP与Dick器械的同侧应变值。结论 椎弓根螺钉器械受力以弯曲力矩为主。

Objective To test the standing force state of pedicle screw's instrumentation and provide a theoretical basis for developing and using spinal instrumentation. Methods Polyamide 6 was standardized and machined to represent vertebral body. A total corpectomy defect was simulated by using two independent fixation cyclinders instrumented with the spinal device, representing a 'worst case scenario' for the implant system with an entire vertebral body missing. Anterior compressive flexure strains were analyzed according to a pattern in which the load was increased progressively at the rate of 50N step by step, and the value of bilateral strains was recorded, corresponding calculation was carried out to analyze the pull and compressive strains of instrumentation induced by bending.Results The loading strain test demonstrating the computing strains of bending pull side was larger than the bending compressive side under the equal load. The strains of SDR was significantly lower than the same side of VSP and Dick under the equal load.Conclusion At the same anterior flexure compressive load, the strains of pedicle screw implants are mainly caused by bending morement.