有限元分析股骨颈骨折伴下后方不同程度骨缺损空心螺钉内固定后的稳定性

Finite element analysis of femoral neck fracture with different degrees of posterior-inferior bone defect after cannulated screw internal fixation

背景:空心螺钉固定为新鲜股骨颈骨折的首选治疗方法,但对于伴有骨缺损的患者,由于股骨近端力学传导及稳定性发生明显改变,易导致内固定物失效、骨折不愈合或延迟愈合等,因此生物力学研究具有重要的临床意义。目的:利用有限元方法探究骨缺损后股骨近端的生物力学改变,比较不同构型空心螺钉固定内收型股骨颈骨折伴下后方不同程度骨缺损的生物力学效果。方法:获取一名成年健康男性志愿者股骨近端CT扫描DICOM原始数据,利用MIMICS 10.01软件、Rhino3D NURBS软件制作内收型股骨颈骨折伴后下方不同程度骨缺损模型(无缺损模型、小缺损模型、中缺损模型与大缺损模型),在4组模型中各配置两种构型的空心螺钉(倒三角、正三角),装配完成后进行网格划分、材料属性赋值;通过ABAQUS 6.12软件建立股骨头中心和表面的耦合关系,对所有模型施加缓慢行走时的载荷和约束。结果与结论:①无缺损模型的股骨颈内侧承受压应力,外侧承受张应力,股骨头应力分布较为均匀,随着股骨颈下后方缺损程度的增加,压力侧和张力侧空心螺钉、空心螺钉尾部及股骨头的应力峰值逐渐上升;②随着缺损程度的增加,空心螺钉压力侧应力峰值逐渐增加,在中、大缺损模型中,倒三角组高于正三角组(P<0.05),在其余模型中两组之间无差异(P>0.05);③随着缺损程度的增加,空心螺钉张力侧应力峰值逐渐增加,在无缺损与小缺损模型中,正三角组高于倒三角组(P<0.05);在大缺损模型中,正三角组低于倒三角组(P<0.05);在中缺损模型中两组无差异;④随着缺损程度的增加,股骨头应力峰值逐渐增加,3种模型中倒三角组与正三角组均无明显差异(P>0.05);⑤随着缺损程度的增加,空心螺钉尾部应力峰值逐渐增加,在小、中、大缺损模型中,倒三角组高于正三角组(P<0.05),在无缺损模型中两组无差异(P>0.05);⑥结果表明,下后方不同程度骨缺损可显著影响股骨近端力学性能,对于无缺损或缺损程度较小的股骨颈骨折,空心螺钉倒三角构型的生物力学性能优于正三角构型,而对于缺损程度较大的股骨颈骨折,空心螺钉正三角构型的生物力学性能优于倒三角构型。

BACKGROUND:Cannulated screw fixation is the first choice for the treatment of fresh femoral neck fracture.However,in the patients with bone defect,the mechanical conduction and stability of the proximal femur are obviously changed,which easily leads to the failure of internal fixation,nonunion or delayed healing of the fracture,so the study of biomechanics has important clinical significance.OBJECTIVE:To explore the biomechanical changes of proximal femur with posterior-inferior bone defect using finite element analysis,compare the biomechanical effect of cannulated screws with different configurations in treatment of adductive femoral neck fractures.METHODS:Original DICOM data of CT scan of proximal femur in an adult healthy male volunteer were obtained.MIMICS 10.01 software and Rhino3D NURBS software were used to make the models of femoral neck fracture with different degrees of posterior-inferior bone defects(no defect model,small defect model,medium defect model and large defect model).Two configurations of cannulated screws(inverted triangle and positive triangle)were used in four models.Mesh generation and material property assignment were conducted after assembly.The coupling relationship was established between the center and the surface of the femoral head by ABAQUS 6.12 software.The load and constraints of slow walking were applied to all models.RESULTS AND CONCLUSION:(1)The inner side of the femoral neck was subjected to compressive stress,and the lateral side was subjected to tensile stress for the non-defect model.The stress distribution of the femoral head was more uniform.With the increase of the degrees of posterior-inferior bone defect,the stress peak value of femoral head,femoral neck pressure side and tension side,and cannulated screw tail were increased gradually.(2)With the increase of the defect degree,the peak value of the stress on the pressure side of the cannulated screw increased gradually.In the middle and large defect models,the stress in the inverted triangle group was higher than in the regular triangle group(P<0.05),and there was no difference between the two groups in the other models(P>0.05).(3)With the increase of the defect degree,the peak stress on tension side of cannulated screw increased gradually.In the model of no defect and small defect,the stress in the regular triangle group was higher than in the inverted triangle group(P<0.05).In the large defect model,the stress in the regular triangle group was lower than in the reverted triangle group(P<0.05).In the middle defect model,there was no difference between the two groups.(4)With the increase of the defect degree,the peak stress of femoral head increased gradually.There was no significant difference between the inverted triangle group and the regular triangle group in the three models(P>0.05).(5)With the increase of the defect degree,the peak value of stress in the tail of cannulated screw increased gradually.In the small,medium and large defect models,the stress in the inverted triangle group was higher than in the regular triangle group(P<0.05).No significant difference was found between the two groups in models without bone defect(P>0.05).(6)Results suggested that different degrees of posterior-inferior bone defects could obviously affect the biomechanical properties of the proximal femur.For femoral neck fracture with no defect or lesser degree of defect,the biomechanical effect of inverted triangle was superior to regular triangle.For femoral neck fracture with big defect,the biomechanical effect of regular triangle was superior to inverted triangle.