新型和传统寰椎椎弓根螺钉生物力学稳定性的有限元分析

目的验证新型寰椎椎弓根螺钉离体生物力学稳定性。方法通过CT扫描获取1名健康成年男性志愿者C_(0~3)图像信息,应用Hypermesh 12.0等图像处理软件构建C_(0~3)三维有限元模型并验证其有效性。置入新型寰椎椎弓根螺钉并枢椎椎弓根螺钉或传统寰椎椎弓根螺钉并枢椎椎弓根螺钉建立2种内固定模型,观察其前屈、后伸、侧曲、扭转等加载条件下C_0/C_1、C_1/C_2、C_2/C_3的活动度及内固定的应力分布,比较2种内固定的生物力学特性。结果置入新型螺钉后C_1/C_2扭转活动度比传统螺钉减少20.331 8%,其他加载条件下活动度基本等同。在侧曲与扭转状态下,新型螺钉最大应力均小于传统螺钉,在前屈、后伸时最大应力相当。结论新型螺钉的生物力学稳定性与传统螺钉相当,在对抗扭转活动方面优于传统螺钉;新型螺钉使应力更加合理分散,最大应力减小,有助于降低内固定失效风险。

Finite element analysis of biomechanical stability of new and traditional type atlas pedicle screw

Objective To evaluate the biomechanical stability of new type atlas pedicle screw in vitro. Methods C_0-3 image of a health male volunteer was obtained by CT scan. A three dimensional finite element model was constructed by Hypermesh12.0 and other image processing softwares, and it was validated by standard reference model. Then new type/traditional atlas pedicle screw and axis pedicle screw were implanted into the model respectively in order to construct 2 internal fixation models. The activity of C₀/C₁, C₁/C₂ and C₂/C₃ and the stress distribution of internal fixation under loading conditions of flexion and extension, lateral bending(left and right), torsion(left and right) was observed. Biomechanical property was compared between 2 internal fixations. Results Comparing new type screw with traditional screw, the torsional activity of C₁/C₂ was decreased by 20.331 8%, while activity in other conditions was approximately equal. The maximum stress of new type screws was less than that of the traditional screw under lateral bending and torsion conditions, while that was equal under flexion and extension conditions. Conclusion The biomechanical stability of new type screw is similar to that of traditional screw, and the new type screw is superior to traditional screw in fighting against torsion. The new type screw allows stress to be more reasonably dispersed, maximum stress to be decreased and helps reduce the risk of internal fixation failure.