1.#$TABSchool of medical instrument and food engineering,University of Shanghai for Science and Technology;2.Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine
目的 研究可吸收镁合金螺钉应用于寰枢椎脱位固定的可行性。方法 选用WE43型镁合金,设计三角形、矩形、梯形、锯齿形四种不同螺纹形式镁合金螺钉,对螺钉-聚氨酯试验块模型、寰枢椎固定系统模型进行有限元仿真分析,获得模型上的应力分布和位移分布。结果 四种不同螺纹形式的镁合金螺钉按照ASTM F 543标准进行拔出力仿真分析,结果表明：三角形螺纹螺钉上应力峰值最小,矩形、梯形螺纹螺钉较大,锯齿形螺纹螺钉上应力峰值最大；用三角形螺纹镁合金螺钉进行寰枢椎固定有良好的固定效果；在三角形螺纹螺钉表面喷涂羟基磷灰石(HA)涂层后,可降低螺钉的应力峰值。 结论 在相同载荷条件下,三角形螺纹螺钉具有较好的稳定性,抗拔出力性能最佳；使用热处理后的三角形螺纹镁合金螺钉进行寰枢椎固定,螺钉强度满足承载要求；在螺钉表面喷涂HA涂层,可优化螺钉的力学性能,并且涂层与螺钉之间有良好的结合强度。
Objective To investigate the feasibility of absorbable magnesium alloy screws in atlantoaxial dislocation fixation. Methods Four kinds of screws with triangular, rectangular, trapezoidal and zigzag screw thread were designed with WE43 magnesium alloy. The finite element simulation analyses were performed on the screw- polyurethane model and atlantoaxial fixation system model. The stress and displacement distributions on the models were obtained. Results The pull-out force simulations were carried out on four kinds of magnesium alloy screws according to ASTM F 543. The results show that the peak stress on the screw with triangular thread is the smallest, and that on the screw with zigzag thread is the largest. The magnesium alloy screw with triangular thread has good fixation effect on atlantoaxial dislocation. Hydroxyapatite (HA) coating on the surface of screw with triangular thread can reduce the peak stress of the screw. Conclusions Under the same loading condition, the screw with triangular thread has good stability and the best pull-out force performance. After heat treatment, the strength of magnesium alloy screw with triangular thread meets the load-bearing requirements for atlantoaxial dislocation fixation. HA coating on the screw surface can optimize the mechanical properties of screw, and there is a good bonding strength between the coating and the screw.