Computational Modeling of Avascular Femoral Necrosis using Finite Element Analysis

Abstract

The purpose of this study is to conduct computational modeling and simulation of Avascular Femoral Necrosis (AVN) using linear elastic finite element analysis to predict failure in femoral neck. AVN is complex disease of the femoral head. Since femur is the only weight bearing bone in the body, AVN may cause hindered movements and stiffness in the hip joint. Clinical and anatomical significance of AVN has been well established already in the literature. Moreover, it is extensively studied that bone become weaker to provide mechanical support after necrosis. Until now, different animal models have been developed to study mechanical strength and properties of healthy and necrotic bones. However not a single human model is reported in the literature to predict rate of degradation for estimation analysis. In this research, an effort is made to create computer models using physics of different stages of AVN deploying techniques like image based modeling and Finite Elements. This will enable us to understand more about distribution of stresses localized in the groin area and femoral head w.r.t load alignment. A mechanically elastic finite element analysis was performed. Our results show that with the progress in bone damage during necrosis, bone behavior changes. Stress become higher in the femoral neck at the point of articulation and shaft become weaker hence prone to fracture. With the increase in the load, femoral neck narrowing risk also increases due to more stresses in this localized region. Von Mises Stress on the superior and inferior regions of femoral neck intersected with frontal plane. Additionally, this study also conducted a mechno-elastic finite element analysis with varying body weights. Increasing weights tend to increase the unborn stresses. Convergence analysis was also carried out for finer meshes. Maximum stress of (146MPa) and displacement of (0.04mm) was observed in stage IV of the AVN models whole bone model whereas in the necrotic region a localized Von Mises stress value of 4.6MPa is observed compared to the health model which was only 1.6MPa. The stresses inferred from this research reasonably correlates with values reported in the literature. We believe that results obtained from this study will be very useful for clinical xvii prognosis in future; since these computer models will be used as an aid to understand in depth analysis and etiology of necrosis in various stages with numerical accuracy. Keywords: Finite element analysis, validation, simulation and AVN.