Abstract
NiTi (nickel-titanium) stents are nowadays commonly used for the percutaneous treatment of peripheral arterial disease. However, their effectiveness is still debated in the clinical field. In fact a peculiar cyclic biomechanical environment is created before and after stent implantation, with the risk of device fatigue failure. An accurate study of the device fatigue behavior is of primary importance to ensure a successful stenting procedure. Regulatory authorities recognize the possibility of performing computational analyses instead of experimental tests for the assessment of medical devices. However, confidence in numerical methods is only possible after verification and validation of the models used. For the case of NiTi stents, mechanical properties are strongly dependent on the device dimensions and the whole treatments undergone during manufacturing process. Hence, special attention should be paid to the accuracy of the description of the device geometry and the material properties implementation into the numerical code, as well as to the definition of the fatigue limit. In this paper, a path for setting up an effective numerical model for NiTi stent fatigue assessment is proposed and the results of its application in a specific case study are illustrated.
Highlights
Nowadays nickel-titanium (NiTi) is commonly used in the production of medical devices
In this paper we propose a path, combining experimental and numerical tests, which can be followed to set up an effective finite element (FE) model of a NiTi stent suitable for fatigue assessment
We focus on those steps that precede the proper device fatigue FE analyses, but are fundamental for getting reliable results from them
Summary
Nowadays nickel-titanium (NiTi) is commonly used in the production of medical devices. The material capability of undertaking high deformation without residual permanent strain makes NiTi extremely advantageous for endovascular applications. Referring in particular to the cardiovascular field, NiTi stents are used widely for the treatment of peripheral arterial disease, one of the major manifestations of systemic atherosclerosis [1]. The introduction of self-expandable stents for the treatment of peripheral arteries has strongly improved the efficacy of the interventional procedure: thanks to pseudo-elasticity, NiTi ensures the recovery from the expanded configuration at the end of each cyclic deformation and the preservation of the normal blood stream [3]. Endovascular treatment success is still undermined by stent long-term fatigue failure due to the cyclic loading, possibly leading to re-occlusion of the artery (in-stent restenosis) [4,5]
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