基于有限元分析的钛合金椎弓根螺钉螺纹结构优化

钛及其合金因其优异的力学性能和生物相容性而被用于制作椎弓根螺钉。然而椎弓根螺钉松动会威胁内固定系统的稳定性，严重时需要进行二次手术，增加医疗成本及患者负担。最大拔出力是评价螺钉固定能力的常用指标，合理设计椎弓根螺钉结构参数可以有效地增大其拔出力。采用有限元分析的方法模拟钛合金椎弓根螺钉的拔出过程，对螺钉头部施加1.8 mm的轴向位移，记录其拔出载荷与位移，探讨螺钉结构参数对其最大拔出力的影响。结果表明：螺钉结构参数中螺钉外径对拔出力的影响最大，螺纹深度的影响最小；在椎弓根螺钉选型时尽量选择较大的螺钉外径、较小的螺距以及适中的螺纹深度。

Optimization of titanium alloy pedicle screw thread structure based on finite element analysis

Titanium and its alloys are used to make pedicle screws because of their excellent mechanical properties and biocompatibility. However, the loosening of pedicle screws will threaten the stability of the internal fixation system. In serious cases, secondary surgery is required, which increases the medical cost and the burden of patients. The maximum pullout force is a common index to evaluate the screw fixation ability. The pullout force can be effectively increased by the reasonably design of screw structure parameters of pedicle screws. The extraction process of titanium alloy pedicle screw was simulated by finite element analysis. The axial displacement of 1.8 mm was applied to the screw head, the extraction load and displacement were recorded, and the influence of screw structural parameters on its maximum extraction force was discussed. The results show that among the screw structural parameters, the screw outer diameter has the greatest influence on the pullout force, and the thread depth has the least influence. In the selection of pedicle screws, larger screw outer diameter, smaller screw pitch and moderate thread depth should be selected.