骨水泥分布位置与含量对股骨反转子间骨折应力、位移影响的有限元分析

Finite element analysis of the effect of the distribution position and content of bone cement on the stress and displacement of reverse femoral intertrochanteric fracture

背景:股骨近端防旋髓内钉是治疗骨质疏松性反转子间骨折的首选治疗方案,其中骨水泥增强可减少股骨近端防旋髓内钉切出与切穿的概率,但目前没有相关生物力学研究证明骨水泥的含量及位置对骨折端应力及位移的影响。目的:通过有限元方法分析骨水泥增强型股骨近端防旋髓内钉中骨水泥含量及位置对老年骨质疏松性股骨反转子间骨折应力、应变及位移的影响。方法:采用Mimics软件建立健康成年女性右侧股骨模型,并在Geometric软件中进行光滑处理,利用Solidworks软件分别建立股骨近端防旋髓内钉(无骨水泥、头端球形1 mL骨水泥、头端球形2 mL骨水泥、头端球形3.4 mL骨水泥、螺旋刀片周围圆柱形5 mL骨水泥)5种类型内固定方式及股骨反转子间骨折(AO分型31-A3.1型)模型,装配后,在Ansys软件中比较5种模型内植物的总应力分布、应力峰值及位移。结果与结论:①无骨水泥与头端球形1 mL、头端球形2 mL、头端球形3.4 mL、螺旋刀片周围圆柱形5 mL骨水泥增强型股骨近端防旋髓内钉组内植物的应力峰值分别为571.07 MPa(位于螺旋刀片与主钉交界处),495.45 MPa(位于螺旋刀片与主钉交界处)、467.20 MPa(位于主钉与远端螺钉连接处)、642.70 MPa(位于主钉与远端螺钉连接处)、458.58 MPa(位于远端与主钉交界处);②无骨水泥与头端球形1 mL、头端球形2 mL、头端球形3.4 mL、螺旋刀片周围圆柱形5 mL骨水泥增强型股骨近端防旋髓内钉组内植物的最大位移量分别为9.2605,7.5891,7.3168,6.7907,6.6157 mm,均位于股骨头近端;③结果显示,采用股骨近端防旋髓内钉内固定股骨反转子间骨折时,骨水泥增强较未增强有明显的力学稳定性,并且螺旋刀片周围5 mL骨水泥的增强效果最好,对于老年不稳定型股骨转子间骨折是优先选择。

BACKGROUND:The proximal femoral nail antirotation is the preferred treatment for reverse osteoporotic intertrochanteric fractures.Bone cement enhancement can reduce the probability of proximal femoral nail antirotation cut-out and cut-through,but there are no relevant biomechanical studies demonstrating the effect of bone cement content and location on the stress and displacement of the fracture end.OBJECTIVE:To investigate the effects of different contents and locations of bone cement in cement-reinforced proximal femoral nail antirotation on stress,strain,and displacement of reverse osteoporotic femoral intertrochanteric fractures in the elderly by finite element analysis.METHODS:A healthy adult female right femur model was extracted by Mimics software and smoothed in Geometric software.Five types of internal fixation methods of proximal femoral nail antirotation(cementless,cephalic spherical 1 mL,cephalic spherical 2 mL,cephalic spherical 3.4 mL,and cylindrical 5 mL around spiral blade)and femoral intertrochanteric fracture(AO subtype 31-A3.1 type)model were established in Solidworks software.After assembly,the total stress distribution,peak stress and displacement of the five models of implants with the femur were compared in Ansys software.RESULTS AND CONCLUSION:(1)The peak stresses of proximal femoral nail antirotation with head-end spherical 1 mL,head-end spherical 2 mL,head-end spherical 3.4 mL,and cylindrical 5 mL enhanced proximal femoral nail antirotation around the spiral blade respectively were 571.07 MPa(located at the junction of the spiral blade and the main nail),495.45 MPa(located at the junction of the spiral blade and the main nail),467.20 MPa(located at the junction of the main nail and the distal screw connection),642.70 MPa(located at the junction of the main nail and distal screw connection),and 458.58 MPa(located at the junction of the spiral blade and the main nail).(2)The maximum displacements of proximal femoral nail antirotation with head end sphere 1 mL,head end sphere 2 mL,head end sphere 3.4 mL,and with cylindrical 5 mL enhancement around the spiral blade were 9.2605,7.5891,7.3168,6.7907,and 6.6157 mm,respectively,all of which were located at the proximal end of the femoral head.(3)These findings revealed that for reverse femoral intertrochanteric fractures treated with proximal femoral nail antirotation,the bone cement enhancement had significant mechanical stability compared with no enhancement,and the enhancement of the spiral blade 5 mL around the perimeter was the best,which is more preferable for aged unstable intertrochanteric fractures.