腓骨支撑踝关节融合的三维有限元分析

Three-dimensional finite element analysis of ankle arthrodesis with fibular strut graft

背景:利用有限元法进行模拟实验具有实验时间短、费用低、可模拟复杂边界条件、力学性能测试全面和可重复性好等优点。目的:通过建立腓骨支撑固定融合踝关节三维有限元模型,分析其生物力学稳定性及安全性,并进一步探讨其生物力学特性。方法:基于正常人体足踝部的三维CT断层数据集,重建踝关节几何形态,应用Abaqus6.9软件模拟踝关节4种活动模式(中立位、背屈位、内旋位和外旋位)时的受力状况,进行静力学有限元分析。结果与结论:成功建立了腓骨支撑固定踝关节融合三维有限元模型,具有良好的几何相似性;在4种载荷下,背屈位引起的螺钉应力峰值最大,应力分布主要集中在螺钉的融合面水平,同时融合面发生的位移最大;而4枚螺钉中,胫骨后外侧螺钉应力最大;外侧支撑腓骨的应力主要集中在钉孔周围及上下钉孔之间的腓骨体部。说明踝关节行腓骨支撑固定融合时,应注意合理放置2枚交叉螺钉,避免应力过分集中,而内固定后应加强抗背屈方向的制动;在处理外侧支撑腓骨时,螺钉钉孔应避免靠近腓骨边缘且上下钉距不宜过大,可有效降低内固定失效的风险。

BACKGROUND：Finite element modeling in biomechanical experiment has advantages in shorter experiment time,lower expense,simulation of complex boundary condition,full analysis of biomechanical characteristics and repeatability.OBJECTIVE：To establish a finite element model of ankle arthrodesis with fibular strut graft,to evaluate the biomechanical stability and safety,and to study the biomechanical characteristics of ankle arthrodesis with fibular strut graft.METHODS：A three-dimensional model of a healthy ankle was developed from computed tomography images.Ankle arthrodesis was simulated by Abaqus 6.9 software,and the model was submitted to mechanical analysis under four load procedures according to the postoperative activity pattern of ankle（neutral position,dorsiflexion,external rotation and internal rotation）.RESULTS AND CONCLUSION：The model was successful established and had high geometric similarity.In dorsiflexion status,posterior-anterior screw yielded maximum stress concentration at middle part;meanwhile,maximum displacement occurred at the fusion site.Screw stress at posterolateral tibial was maximal.A high concentrated stress was found surrounding the screw hole.High stress was distributed between the screw holes of fibular strut.To avoid the high concentration of stress distribution,the crossed screws should be configured appropriately.And additional ante-dorsiflexion immobilization might lower the risk of screw implant failure.Shortening of distance between parallel screws and centralized drilling on fibula also tended to reduce the risk of strut failure.