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Title: Multi-scale mechanical investigation of stainless steel and cobalt-chromium stents
Authors: Kapnisis, Konstantinos 
Constantinides, Georgios 
Georgiou, Harry 
Cristea, Daniel 
Gabor, Camelia 
Munteanu, Daniel 
Brott, Brigitta C. 
Anderson, Peter G. 
Lemons, Jack E. 
Anayiotos, Andreas 
Keywords: Fracture;In-stent restenosis (ISR);Mechanical properties;Nanoindentation;Stents
Category: Materials Engineering
Field: Engineering and Technology
Issue Date: 1-Dec-2014
Publisher: Elsevier Ltd
Source: Journal of the Mechanical Behavior of Biomedical Materials, 2014, Volume 40, Pages 240-251
Abstract: In-stent restenosis (ISR) remains a significant limitation despite the considerable previous clinical and investigative emphasis on the problem. Complications arising from the interaction of stent materials with the surrounding vessel wall as well as from the mechanical forces developing after implantation, play an important role in the development of ISR. To investigate the relation between mechanical factors and stent structural integrity, and to identify any structural weakness points on the geometry of commercially available Stainless Steel and Cobalt-Chromium stents, accelerated pulsatile durability tests were carried out in a simulated physiological environment. Potential spatial variations in the mechanical properties on stent struts and their role in the observed premature failures of the stent devices during operation were also examined. Fretting wear and fatigue-induced fractures were found on stent surfaces after exposure to cyclic loading similar to that arising in vivo. Nanoindentation studies performed on various locations along the stent struts have shown that the hardness of specific stent locations significantly increases after mechanical expansion. The increase in hardness was associated with a reduction of the material's ability to dissipate energy in plastic deformations, therefore an increased vulnerability to fracture and fatigue. We conclude that the locations of fatigue fractures in stent struts are controlled not only by the geometrically-driven stress concentrations developing during cyclic loading but also by the local material mechanical changes that are imparted on various parts of the stent during the deployment process.
ISSN: 17516161
Rights: © 2014 Elsevier Ltd.
Type: Article
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