具有可扩张翼的动力髋螺钉固定股骨转子间骨折的三维有限元分析

Finite element analysis of intertrochanteric fracture fixed by dynamic hip screw with expandable airfoil

目的运用三维有限元法探讨具有可扩张翼的动力髋螺钉固定股骨转子间骨折的生物力学稳定性。方法基于正常成人股骨及动力髋螺钉的CT扫描数据,利用Mimics 13.0、Freeform、Ansys 14.0软件建立具有可扩张翼的动力髋螺钉和普通动力髋螺钉固定的股骨转子间骨折有限元模型;运用有限元分析软件Ansys 14.0,模拟70 kg正常人缓慢行走单腿站立状态的轴向压缩试验及在股骨近端加载一定扭转力矩的扭转实验,比较两组内固定和股骨的应力分布情况,分析两种内固定的生物力学稳定性。结果在轴向压缩试验中,两种骨折内固定模型应力分布情况相似,两组股骨模型的总体应力分布较均匀,两组内固定模型在拉力螺钉与侧方钢板套筒连接部位可见应力集中;在扭转试验中,具有可扩张翼的动力髋螺钉固定的股骨转子间骨折有限元模型可抵抗25 N·m以上、50 N·m以下的扭矩,而普通动力髋螺钉固定的股骨转子间骨折有限元模型只能抵抗5 N·m以上、10 N·m以下的扭矩。结论具有可扩张翼的动力髋螺钉固定股骨转子间骨折的生物力学稳定性较普通动力髋螺钉更具优势。

Objective To analyze the biomechanical stability of intertrochanteric fracture fixed by the dynamic hip screw with expandable airfoil using three-dimensional （3D） finite element method. Methods Based on CT scanning data of normal adult femur and dynamic hip screw, the 3D finite element model of intertrochanteric fracture fixed by the dynamic hip screw with expandable airfoil and conventional dynamic hip screw was established by the software of MIMICS 13.0, Freeform and ANSYS 14.0. The hip was loaded by simulating a 70 kg normal adult slowly walking with one foot landing on the ground or a certain torque; the biomechanical stability of the two kinds of internal fixation was compared for stress distribution of the femur and screw. Results In axial compression test, the stress distribution of the two kinds of fracture-internal fixation model were similar. The stress of two femur models distributed uniformly; the stress of both kinds of internal fixators concentrated upon the joint part of lag screw and lateral steel plate sleeve. In the torsion test, intertrochanteric fracture model fixed by the dynamic hip screw with expandable airfoil could sustain more than 25 N · m torque and less than 50 N·m torque. However, the intertrochanteric fracture model fixated by conventional dynamic hip screw only sustained more than 5 N ·m torque and less than 10 N ·m torque. Conclusion The dynamic hip screw with expandable airfoil has more advantages than conventional dynamic hip screw in the aspect of biomechanics and worth for clinical application.