步态周期垂直力下股骨转子间骨折股骨近端防旋髓内钉内固定的生物力学特征

Biomechanical Characteristics of Proximal Femoral Nail Anti-Rotation for Femoral Intertrochanteric Fracture under the Vertical Force of Gait Cycle

目的:仿真模拟步态周期垂直力下2018版AO31-A1.3型股骨转子间骨折股骨近端防旋髓内钉(PFNA)内固定的生物力学特征。方法:获取一名老年女性髋部骨折患者的CT资料并在Mimics中重建股骨近端三维模型,在SolidWork中构建PFNA三维模型,将股骨近端模型与PFNA模型进行装配,导出至Hypermesh进行前处理,最后导出至LS-DYNA进行求解仿真。结果:PFNA应力集中在螺旋刀片和主钉上;PFNA应力达峰后逐渐减小又逐渐增大。PFNA位移以螺旋刀片尖端的最大,达6.74 mm;主钉次之,为1.79 mm;尾钉的最大位移为0.83 mm。头颈骨折块成角包含了3个方向的成角,达峰后逐渐减小并维持在2.5°。股骨应力及位移主要发生在脚掌踏地相和脚尖离地相之间;最大应力集中在头颈骨折块下内侧与股骨干相接处;最大位移位于股骨头内侧。PFNA应力及位移主要在脚掌踏地相和脚尖离地相之间;最大应力集中在螺旋刀片与主钉孔交界、主钉上段与下段交界处;螺旋刀片最大位移在其尖端。结论:股骨转子间骨折PFNA内固定的应力位移变化不完全与步态周期同步,呈现一定滞后性。

Objective:To simulate the biomechanical characteristics of proximal femoral nail anti-rotation(PFNA) in treating A1.3 type femoral intertrochanteric fracture under the vertical force of gait cycle.Methods:The CT images of an elderly female hip fracture patient were recruited and used to reconstruct three-dimensional model of proximal femur in Mimics.The 3 D model of PFNA was constructed in SolidWorkand, and these two models were assembled.Then components were exported to Hypermesh for pre-processing, and finally output for calculation in LS-DYNA.Results:The stress of PFNA was concentrated on helical blade and nail, and it gradually decreased and increased again after reaching the peak.The maximal displacement of PFNA was 6.74 mm at the tip of helical blade, then followed by nail with 1.79 mm and the locking bolt with 0.83 mm.The angle of the head-neck fragment included three directions, which gradually decreased and maintained at 2.5° after reaching the peak.The results showed that the stress and displacement of femur mainly occurred between the plantar stepping phase and the toe off phase, the maximal stress was concentrated in the joint between the medial side of head-neck fragment connect with shaft, and maximal displacement of femur head located in the medial side.The stress and displacement of PFNA mainly occurred between the plantar stepping phase and the toe off phase.The maximal stress was concentrated at the conjunction of helical blade and nail.The maximal displacement of helical blade located on the tip.Conclusion:The changes of stress and displacement of PFNA and femoral in intertrochanteric fracture are not completely synchronized with the gait cycle, which shows a certain lag.