Self-expanding Nitinol stents for endovascular peripheral applications: A review

Peripheral arterial diseases affect a significant portion of the global population, fostering research to find innovative and effective solutions to improve people's life. A primary focus for researchers and manufacturers is the continuous improvement of the most important, non-surgical treatment for this pathology, the endovascular stent. This device is the main feature enabling a lifesaving technique: the percutaneous vascular interventions. Stents are vital for restoring blood flow and enhancing long-term vessel patency, they are available in various materials, shapes and typologies. Recent advancements in stent design, particularly through additive manufacturing, create new opportunities for optimizing the device performance and possibly opening new areas of intervention. This review provides a detailed quantitative analysis on the most widely used category of devices: self-expanding stents made of Nitinol, a nickel-titanium alloy that shows a superelastic behavior. A set of figures of merit related to stent design are described and analyzed, with a focus on the influence of geometry on mechanical performance. Additionally, a comprehensive comparative analysis of the commercial stents evaluates the geometry and performance of many commercial solutions, including both arterial and venous types. This analysis offers quantitative tools to assist surgeons and designers in selecting the most important features of a stent with respect to its main application. To conclude this work, an overview of future manufacturing possibilities is provided mainly focusing on the additive manufacturing technology. The freedom of shape given by this method opens up new paths in terms of global shapes, strut geometry and sizes, revealing new avenues which point strongly towards ad-hoc and specifically patient-customized stent design.