Finite element analysis for fatigue behaviour of a self-expanding Nitinol peripheral stent under physiological biomechanical conditions.

Self-expanding Nitinol stents are increasingly used to treat femoropopliteal artery (FPA) occlusions, but the risk of stent fatigue failure exists due to complex artery deformation during daily activities. Finite element analysis (FEA) has been widely applied to study the stent fatigue behaviours, but physiological deformation and atherosclerotic plaque were not considered simultaneously in previous studies. In this work, to show the necessity and feasibility of considering both factors in evaluation of the stent fatigue behaviours, a comprehensive FEA framework considering both factors is established, and an easy loading method for the complex boundary condition is proposed. Four comparative simulations are successfully conducted, and the stent fatigue behaviours are analysed based on the distributions and maximum values of the self-defined mean and alternating strains. Results show that both the physiological deformation and atherosclerotic plaque significantly contribute to the stent fatigue life. The case with the complex boundary condition and atherosclerotic plaque is the most critical of the four cases, and the minimum safety factor is 0.62. In conclusion, it is necessary to consider both physiological deformation and atherosclerotic plaque in the evaluation of stent fatigue behaviours, and ignoring any of them would lead to overestimation of the stent fatigue life. The work in this paper offers a solid foundation for accurate evaluation of the stent fatigue lifetime in patient-specific surgery plans via FEA.