A computational study of fatigue resistance of nitinol stents subjected to walk‐induced femoropopliteal artery motion

R He,L.G Zhao,V.V Silberschmidt,H Willcock

doi:10.1016/j.jbiomech.2021.110295

Abstract

Fatigue resistance of nitinol stents implanted in femoropopliteal arteries is a critical issue because of their harsh biomechanical environment. Limb flexions due to daily walk expose the femoropopliteal arteries and, subsequently, the implanted stents to large cyclic deformations, which may lead to fatigue failure of the smart self-expandable stents. For the first time, this paper utilised the up-to-date measurements of walk-induced motion of a human femoropopliteal artery to investigate the fatigue behaviour of nitinol stent after implantation. The study was carried out by modelling the processes of angioplasty, stent crimping, self-expansion and deformation under diastolic-systolic blood pressure, repetitive bending, torsion and axial compression as well as their combination. The highest risk of fatigue failure of the nitinol stent occurs under a combined loading condition, with the bending contributing the most, followed by compression and torsion. The pulsatile blood pressure alone hardly causes any fatigue failure of the stent. The work is significant for understanding and improving the fatigue performance of nitinol stents through innovative design and procedural optimisation.

Highlights

Peripheral artery disease (PAD), narrowing of the peripheral arteries, is caused by the build-up of plaque on the inner wall of a blood vessel, which restricts the blood flow through the lower limbs
The results suggested that the inner corners of U-bends had a higher risk of fatigue failure due to blood pressure
This study is the first attempt to investigate the fatigue resistance of nitinol stents subjected to walk-induced femoropopliteal artery motion

Summary

Introduction

Peripheral artery disease (PAD), narrowing of the peripheral arteries, is caused by the build-up of plaque on the inner wall of a blood vessel, which restricts the blood flow through the lower limbs. Angioplasty alone was unsuccessful in about 50% of cases because of the acute elastic recoil, residual stenosis and long-term restenosis (Jeans et al, 1990; Saxon et al, 2003). Balloon-expandable stents reduced failure rates immediately after the deployment by preventing elastic recoil and scaffolding dissection. They do not perform well under large biomechanical deformations in the femoropopliteal arteries due to their limited flexibility and susceptibility to permanent deformation under external forces (Heuser and Henry, 2008). The long-term outcomes of stent deployment are disappointing due to the development of restenosis over time (Henry et al, 1995). Self-expandable nitinol stents were developed, which have excellent flexibility and can recover from deformation thanks to their unique superelastic behaviour.

Methods

Results

Conclusion