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TM_F_2606_
_08_2014
Designation:F260608(Reapproved 2014)Standard Guide forThree-Point Bending of Balloon Expandable Vascular Stentsand Stent Systems1This standard is issued under the fixed designation F2606;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide provides guidelines for quantitatively char-acterizing balloon-expandable stent and stent system flexibilityusing three-point bending procedures.Guidelines are providedfor characterizing deployed stent flexibility,and for character-izing pre-deployment stent system flexibility in the region ofthe stent and balloon.1.2 This guide is not recommended for test articles thatcannot be appropriately evaluated using a span length to stentouter diameter(as tested)ratio of at least 4:1.Test articles thatdo not meet this requirement are likely to exhibit appreciabledeformation by modes other than bending.1.3 This guide does not provide procedures for characteriz-ing the bending flexibility of self-expanding stents,self-expanding stent systems,endoprostheses(stent-grafts),or en-doprostheses systems.However,some aspects of this guidemay be useful for developing appropriate three-point bendingcharacterization procedures for these devices.While this guidewas developed with vascular stents and stent systems in mind,it may be useful for characterizing the bending flexibility ofballoon-expandable stents and stent systems used in non-vascular applications.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.2.Terminology2.1 Definitions:2.1.1 bending flexibility,na measure of the ability of a testspecimen to bend.2.1.2 bending stiffness,na measure of the ability of a testspecimen to resist bending.2.1.3 conformability,nthe degree to which a stent or stentsystem matches the native curvature of the vasculature.2.1.4 deflection,ndisplacement of the dynamic support(loading anvil)at any point in the test.2.1.5 delivery system,ncatheter that is used to deliver anddeploy a stent at the target site.A delivery system forballoon-expandable stents may be similar to a balloon-dilatation(angioplasty)catheter.2.1.6 midspan bending moment,na linear estimate of thebending moment at the center of the span.See 8.5.2.1.7 midspan curvature,na linear estimate of the curva-ture of the center of the span.See 8.5.2.1.8 span length,ndistance between the centers of thesupports.2.1.9 stent system,ndelivery system with a pre-mountedstent.2.1.10 stent,vascular,nsynthetic structure that is perma-nently implanted in the native or grafted vasculature and that isintended to provide mechanical radial support to enhancevessel patency.3.Significance and Use3.1 This guide can be used to obtain force versus deflectionor midspan bending moment versus midspan curvature curvesfor stents and stent systems subjected to three-point bendingconditions.Bending flexibility of a stent system may be afactor in its ability to track through the vascular anatomy,andmay be a factor in vascular trauma along the delivery pathwaydistal to the guide catheter.Bending flexibility of a deployedstent may be one measure of its ability to flex with a vessel,orto conform to the natural curvature of a vessel.Bendingflexibility of a delivery system may also be of interest if it isdesired to assess the separate contributions of the deliverysystem and the mounted stent to the overall flexibility of thestent system.3.2 This guide is not intended to determine materialproperties,stent system trackability(ability of a stent system tofollow a guide wire and/or guide catheter through vasculartortuosity),or stent system deliverability(ability of a stentsystem to deliver a stent to the implantation site(s)or throughparticular level(s)of vascular tortuosity).While this guide doesnot determine stent system trackability or deliverability,it canprovide quantitative insight into how stent system bending1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.30 on Cardiovascular Standards.Current edition approved March 1,2014.Published April 2014.Originallyapproved in 2008.Last previous edition approved in 2008 as F2606 08.DOI:10.1520/F2606-08R14.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 flexibility affects trackability and deliverability.Similarly,while this guide does not determine conformability of adeployed stent,it can provide quantitative insight into howstent and/or stent system bending flexibility affects deployedstent conformability.Since this guide quantifies bendingflexibilit