新型寰椎内径锥形螺钉的设计与拔出力的测试

目的比较两种设计的寰椎椎弓根钉的最大拔出力,为临床选择寰椎推弓根钉类型提供生物力学依据。方法设计制作两种寰椎椎弓根钉,根据螺纹部分分为皮质骨螺钉(A型螺钉)、内径锥形螺钉(B型螺钉),利用24节新鲜猪寰椎标本,置入两种类型的椎弓根钉,进行拔出试验,测定每种螺钉的最大拔出力,进行统计学分析比较。结果同一长度,不同设计的螺钉抗拔出力接近,均无显著性差异;同一直径两种设计的螺钉,28 mm比26 mm的抗拔出力略大,但均无显著性差异。结论新型寰椎内径锥形螺钉(3.0 mm)抗拔力高,螺钉根部强度好,抗弯曲、断裂性能好,可提供足够的即刻稳定性,是寰椎椎弓根固定的理想螺钉类型。

Design of new atlas diameter tapered screw and its pull-out strength test

Objective To compare the greatest pullout strength of two designed atlas pedicle screws for providing biome-chanical basis for clinical choosing the types of atlas pedicle screws.Methods Two kinds of atlas pedicle screws were designed according to the threaded part,and they’re classified into the threaded portion(A-type screws) and screw diameter cone(B-type screw).Twenty four samples of fresh pig atlas were used,the two types of pedicle screws were implanted and the maximum pullout strength for each screw was measured.The results were analyzed and compared by statistical method.Results In the condition of same diameter,the pull out strength of 28 mm was slightly larger than that of 26 mm,but there was no significant difference.In the condition of same length,the pull out strength of different types of screws was nearly the same,there was no significant difference.Conclusion The new atlas diameter tapered screw(3.0 mm) has high pulling force,the screw root strength and resistance to bending and fracture,can provide sufficient immediate stability.So it is the ideal type of atlas pedicle screws.