股骨转子下骨折内固定的生物力学有限元比较研究

Biomechanical finite element comparative study of internal fixation for subtrochanteric fracture

目的借助于有限单元技术探讨髓内和髓外方式固定股骨转子下骨折的生物力学特性。方法建立完整股骨的三维有限元模型以及PFP和加长型PFNA的CAD模型,按照标准骨科手术技术予以固定,于股骨头处加载应力,分析内固定的应力分布状态和骨折块的位移。结果 PFP钢板的应力主要集中在钢板的内侧和钢板螺钉交界处。其中最大应力为190.6MPa,集中在最远端的螺钉钢板交界处。钢板螺钉交界处的应力集中也非均等分布。其头端和远端的应力较为集中,中间三颗螺钉应力集中并不明显。加长型PFNA固定的应力分布主要集中在主钉的外侧中段和下端。应力集中的最大值为165Mpa。最大应力集中在头端螺钉与主钉交界处。PFP固定转子下骨折的骨折块位移,分别取第一、二、三块(由近端及远端)骨折块靠近骨折线的节点作为标记点,以标记骨折在应力加载后的位移度。第一骨折块位移2.38mm,第二骨折块位移为2.25mm,第三骨折块位移1.74mm。PFNA加长型固定转子下骨折的骨折块位移,分别取第一、二、三块(由近端及远端)骨折块靠近骨折线的节点作为标记点,以标记骨折在应力加载后的位移度。第一骨折块位移2.13mm,第二骨折块位移为2.35mm,第三骨折块位移1.75mm,两者的差异具有统计学意义。结论从静力分析角度,加长型PFNA比PFP在固定股骨转子下粉碎性骨折方面,更有优势。

Objective To investigate the biomechanical characteristics of intramedullary and extramedullary fixation of snbtrochanteric fractures of the femur With the aid of finite element technique. Methods A three- dimensional finite element model of the intact femur,PFP model and CAD model with long PFNA were established and fixed according to the standard Department of orthopedics surgical technique,the stress was loaded at the femoral head,the stress distribution of the internal fixation and the displacement of the fracture block were analyzed. Results The stress of PFP steel plate was mainly concentrated At the junction between the inside of the steel plate and the plate screws.The maximum stress was 190.6MPa,coneentrated at the distal end of the screw plate junction.The stress concentration at the juncture between the steel plate and the screw was not equally distributed.The stress at the head and distal end was more concentrated,and the stress concentration among the three screws was not obvious.The stress distribution of the lengthened PFNA was mainly concentrated in the middle and lower ends of the outer side of the main nails.The maximum of the stress concentration was 165Mpa.The maximum stress concentrated at the junction of the head end of screw and the main nail.For the Fracture displacement of subtrochanteric fracture fixed by PFP,the first,second,three blocks （from the proximal and distal nodes） fracture block near the fracture line were taken as a marker to mark the fracture stress after loading displacement.The first block fracture displacement was 2.38mm,the second fracture displacement was 2.25mm,the third fracture displacement was 1.74mm.For the fracture displacement of PFNA lengthened subtrochanteric fracture,the first,second,three blocks （proximal and distal） fracture block near the fracture line were taken as the mark point to mark the displacement of the fracture after stress loading.The first block fracture displacement was 2.35 mm,the second fracture displacement was 1.75mm,the difference was statistically significant. Conclusion From the point of view of static analysis,lengthened PFNA is more advantage than PFP in comminuted fracture of fixed subtrochanteric femur.