5.1 It is important to consider the durability of implants in deformation modes that are intended to model in vivo conditions. The appropriate amplitude and number of cycles in each of the modes have to be determined independently for the particular clinical use proposed for the implant. These tests do not replicate all varieties and aspects of the deployment process nor the in vivo mechanical environment in its entirety, and as such they cannot be proofs of durability. Instead, the tests provide evidence of durability. The durability tests can also provide a means of assessing design, material, or processing changes.

5.1.1 This guide might be useful for development testing, specification acceptance testing, and regulatory submission testing and filings as it provides a basic assurance that the tests are designed, executed, and reported in a suitable fashion.

5.1.2 If the tests are conducted using a well-defined FTF methodology, they can be useful in:

5.1.2.1 Potential implant improvement through identification of better and worse geometries, materials, and manufacturing processes;

5.1.2.2 Understanding implant durability by estimating the effects of changes in geometry, materials, or manufacturing processes;

5.1.2.3 Estimating the safety factor relative to the amplitudes and other factors in use conditions; and

5.1.2.4 Validating finite element analysis (FEA) and fatigue life models.

5.1.3 As stated in the scope, this guide is not intended to provide the in vivo physiologic deformation conditions to which an implant can be subjected. Reliable clinical data characterizing cyclic in vivo deformation may be lacking for some indications. The user should develop and justify the boundary conditions (e.g., by literature review, in vivo studies, cadaver studies, or modeling of implant in vivo interaction) for the chosen durability bench tests. Additional conditions that may be considered include vessel calcification, vessel taper, eccentric lesions, deformation excursions (e.g., exercise), and vessel remodeling.

5.1.4 Test methods other than those provided in the annexes of this document might be appropriate, depending upon implant design. However, these methods are beyond the scope of this guide.

1.1 This guide includes four separate cyclic deformation durability guides related to vascular stents and vascular stent-grafts: bending, axial, torsional, and compression.

1.2 This guide does not address whether a specific mode of durability testing is relevant for a particular vascular stent and vascular stent-graft design.

1.3 This guide does not address multi-mode testing. Nevertheless, the information included herein could be applicable to developing this type of test.

1.4 This guide applies to vascular stents and vascular stent-grafts, including balloon-expandable and self-expanding stents fabricated from metals and metal alloys commonly used to treat aneurysmal disease, peripheral vessel trauma, or to provide vascular access. These are referred to as the ‘implant’ throughout the subsequent text. The information provided herein does not address all issues related to testing of these devices.

1.5 This guide does not apply to structural heart implants including but not limited to: aortic valve replacement, mitral and tricuspid valve replacement and repair devices, annuloplasty rings, intra-atrial shunts, pacemaker leads, LVADs, etc.

1.6 This guide does not specifically address any attributes unique to coated implants (i.e., implants with a surface layer of an additional material(s)), monolithically polymeric implants, or absorbable implants, although the application of this standard to such products is not precluded.

1.7 This guide is applicable to testing of stents and stent-grafts (or a representative portion of a stent). While the scope of this document does not explicitly cover coupon or surrogate samples, the information in this guide can provide useful information for them.

1.8 This guide applies to in vitro testing of implant durability from non-radial motions. Such motions may arise from musculoskeletal activities, including walking, stair climbing, leg crossing, kneeling, breathing, valsalva, and cardiac motion, as well as extrinsic forces on the body such as lifting of patients between beds.

1.9 This guide does not provide the in vivo physiologic deformation conditions for testing. It is incumbent upon the user of the standard to develop and justify these boundary conditions (e.g., by literature review, in vivo studies, cadaver studies, or modeling of implant in vivo interaction) in these durability bench tests. Additional conditions that may be considered include vessel calcification, vessel taper, eccentric lesions, loading excursions (e.g., exercise), and vessel remodeling.

1.10 This guide does not result in quantitative estimates of implant durability, but rather provides qualitative results (i.e., pass or fail).

1.11 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.12 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.