短与长髓内钉治疗不稳定粗隆下骨折的有限元分析

A finite element analysis on short versus long intramedullary nail for fixation of unstable subtrochanteric femur fractures

[目的]对长、短型髓内钉治疗Seinsheimer V型不稳定骨折进行有限元分析,为临床提供生物力学证据。[方法]三维重建Sawbones股骨模型,制备包含四部分骨折块且有20 mm范围内侧缺损的粗隆下骨折模型。制作长、短髓内钉模型。将模型进行匹配、网格划分、赋值属性等有限元分析前处理。装配、定义接触面、边界条件、载荷设置,进行有限元分析。[结果]随着外力增加长钉以及短钉治疗下各组参考指标均呈线性增长,差异有统计学意义(P<0.001)。2 000 N载荷下,短钉组近端骨块最小位移显著小于长钉组[(16.397±0.044) mm vs(17.210±0.044)mm,P<0.001],短钉组近端骨块最大位移也显著小于长钉组[(28.578±0.020) mm vs(31.171±0.013) mm,P<0.001。此外,短钉组近端骨折线缝隙显著小于长钉组[(1.396±0.074) mm vs(1.798±0.052) mm,P<0.001],短钉组外侧骨折线缝隙显著小于长钉组[(0.525±0.012) mm vs(0.755±0.017) mm,P<0.001]。[结论]短髓内钉较长髓内钉有更佳的控制骨折块移动和对骨折块的把持力,应做为股骨粗隆下骨折内固定的首选。

[Objective]To explore the biomechanical characteristics of short versus long intramedullary nail for fixation of Seinsheimer type V subtrochanteric fractures,and provide biomechanical evidence to the clinical practice.[Methods]A 3-D reconstruction model was created by using the Sawbones,and then mimic four-part subtrochanteric fractures were conducted with UG software,which included a wedge with a 20-mm medial defect to simulate loss of the medial calcar.After pre-processing,including model matching,meshing,as well as assigning properties,interfaces and loading,the finite element analysis were conducted.[Results]Along with increase of loading,the fragmental displacements and fracture voids significantly increased in both the short nail group and long nail group(P<0.001).Under 2000 N loads,the minimal displacement of proximal fracture fragment proved significantly less in the short nail group than that in the long nail group[(16.397±0.044)mm versus(17.210±0.044)mm versus,P<0.001],consistently,the maximal displacement of proximal fracture fragment was of((28.578±0.020)mm versus(31.171±0.013)mm,P<0.001)In addition,the proximal fracture void in the short nail proved significantly less than that in the long nail group[(1.396±0.074)mm versus(1.798±0.052)mm.P<0.001],similarly the lateral fracture void in the short nail group was significantly less than the long nail group((0.525±0.012)mm versus 0.755±0.017)mm,P<0.001)[Conclusion]The short intramedullary nail with advantages of better bone fragment holding,and higher capacity to restrain fragment micro-motion than the long intramedullary nail,should be the first choice for internal fixation of subtrochanteric fractures.