股骨干骨折3种不同固定方式的有限元分析

Finite element analysis of three internal fixation methods for treating femoral shaft fracture

背景:股骨干骨折目前的主流治疗策略是采取手术治疗,方法包括髓内钉固定、钢板固定以及近年来逐渐流行的桥接组合式内固定,然而对比3种内固定方式的生物力学性能研究相对较少。目的:应用有限元技术模拟股骨中段骨折,分析锁定钢板、桥接组合式内固定、髓内钉系统在不同工况条件下的生物力学特点。方法:采集1例来源于遵义医科大学附属医院符合文章纳入排除标准的健康志愿者的左股骨CT资料,通过Mimics及Geomagic软件逆向构建股骨中段骨折伴缺损的数字模型,根据内固定原则,在将骨折模型导入Pro/E软件中后分别与合适尺寸的锁定钢板、桥接组合式内固定系统、髓内钉完成装配,再经过几何清理、模型网格化后纳入Abaqus软件中,应用有限元分析法分析股骨中段骨折3种内固定方式在不同受力状态下的位移及应力情况。结果与结论:在有限元分析结果中可以观察到3种股骨内固定模型在不同的工况下,表现出不同的力学特性。①在垂直应力的加载下,髓内钉受力沿主钉方向分布较为均匀,其承受应力最小;桥接系统两根连接棒在骨折端附近产生“Z”字形变分摊了整体应力,产生的位移最小,稳定性最佳;②在水平应力的加载下,桥接系统承受的应力和产生的位移最小,稳定性最佳,应力集中于桥接系统连接棒上的第1-3固定块及其毗邻金属部件;③在扭转应力的加载下,髓内钉发生的位移最小,稳定性最佳;桥接系统承受的应力和产生的位移最大,应力集中于近端锁钉与骨接触面,稳定性最差;④上述结果证实,股骨桥接系统具有良好的抗压缩和抗弯曲的力学特性,而在抗扭转力方面股骨交锁髓内钉则更具有优势,锁定钢板作为传统偏心固定方案,其垂直抗压和抗折弯稳定性不如前两者,但在抗扭转方面优于双棒桥接系统不如交锁髓内钉。

BACKGROUND:At present,the mainstream treatment strategy for femoral shaft fracture is surgical treatment,including intramedullary nail fixation,steel plate fixation,and Bridge combined fixation system,which is becoming more and more popular in recent years.However,there are relatively few studies on the biomechanical properties of the three internal fixation methods.OBJECTIVE:To simulate the fracture of the middle femur using finite element technique,and analyze the biomechanical characteristics of locking plate,Bridge combined fixation system,and intramedullary nail internal fixation under different working conditions.METHODS:The CT data of left femur of a healthy volunteer from the Affiliated Hospital of Zunyi Medical University meeting the inclusion and exclusion criteria were collected in this study.The digital model of middle femoral fracture with defect was constructed by Mimics and Geomagic software.According to the principle of internal fixation,the fracture model was assembled with appropriate size locking plate,Bridge combined fixation system,and intramedullary nail respectively after introducing the fracture model into Pro/E software.After geometric cleaning and gridding,the model was incorporated into Abaqus software to analyze the displacement and stress of three internal fixation methods of middle femoral fracture under different stress conditions by finite element analysis.RESULTS AND CONCLUSION:In the results of finite element analysis,three kinds of femoral internal fixation models showed different mechanical properties under different working conditions.(1)Under the loading of vertical stress,the force of the intramedullary nail was uniformly distributed along the direction of the main nail,and the stress was the least,and the Z-shaped deformation of the two connecting rods in the bridging system near the fracture end distributed the overall stress,resulting in the smallest displacement and the best stability.(2)Under the loading of horizontal stress,the stress and displacement of the bridging system were the smallest,and the stability was the best.Stress was concentrated on the 1-3 fixing block on the bridging system connection rod and its adjacent metal components.(3)Under the loading of torsional stress,the displacement of the intramedullary nail was the smallest and the stability was the best,while the stress and displacement of the bridging system were the largest,and the stress was concentrated on the interface between the proximal locking nail and the bone,and the stability was the worst.(4)The results show that the femoral bridging system has good mechanical properties of anti-compression and antibending,while the femoral interlocking intramedullary nail has more advantages in anti-torsion force.As a conventional eccentric fixation,locking plate is less stable in vertical compression and bending,but better resistant to torsion than double-bar bridging system and inferior to the interlocking intramedullary nail.