Effects of Stent Structure on Stent Flexibility Measurements

Abstract

Adequate delivery and placement of intracoronary artery stents is dependent on various properties of the stent itself, including flexibility and high-radial strength. Although these properties can be assessed via determination of the bending stiffness and radial stiffness of a stent, the mesh structure of the stent does not lend easily to such measurements. The goal of the present study was to determine an optimal method for determining stent bending stiffness. The four-points bending test was used to evaluate stent flexibility, and the finite element method (FEM) was employed to assess the effect of stent structure on flexibility in stents with differing link structures. The four-points bending test yielded the following bending stiffness values: 85.28 N mm2 for the stent with an S-shaped link; 41.67 N mm2 for the stent with an N-shaped link; 78.79 N mm2 for the stent with a modified W-shaped link; and 188.67 N mm2 for the stent with a W-shaped link. The stent with the point symmetric link configuration (S-, N- and modified W-shaped link) had high flexibility. FEM analysis revealed that low flexibility resulted from interference between the struts at the compressive side. Further, the flexibility predicted from FEM analysis correlated with bending stiffness of the stents. We conclude that use of the four-points bending test yields information that is critical for the design of flexible stents.

Composite Material Stent Comprising Metallic and Non-metallic Materials

“…In their discussion on the mechanism of emergence of kinks in stents using the Finite Element Method, Mori et al state that stent meshes or struts contacting or colliding with each other will cause decrease in their flexibility and lead to formation of kinks (Mori et al, 2004). As a solution to interference of adjacent loops in knitted stents in bending transformation described above, we devised knitted stents whose two wires differed significantly in bending stiffness.…”

“…(Fransen et al 2003) Also, when a stent is bent to an acute angle, adjacent struts come into contact and transform themselves in such a way that they protrude inward, which may result in kinks. (Mori et al 2004) In a composite material stent of metallic and non-metallic materials, mechanical properties such as expansile force and restoring force are determined almost exclusively by the material and structural properties of the metallic component, as the materials have significantly different degrees of bending stiffness. That is, the structural properties of a hybrid stent are similar to those of metallic spirals.…”

Design and Evaluation of Self-Expanding Stents Suitable for Diverse Clinical Manifestation Based on Mechanical Engineering

“…They then proposed a method to evaluate stent and its performances. (Mori & Saito, 2005) performed a four-point bending test using a stainless steel stent to assess flexural rigidity for each different stent structure. (Carnelli et al, 2010) performed two mechanical tests on six kinds of carotid stents.…”

“…They carried out a four-point bending test to assess flexibility of the stent. Their method of bending test was similar to that by (Mori & Saito, 2005). They also conducted a three-point compression test to measure the radial stiffness of the stent.…”

A Study on Designing Balloon Expandable Magnesium Alloy Stent for Optimization of Mechanical Characteristics

“…Therefore, an appropriate stent structure design is required to ensure radial rigidity. Although there are numerous papers on the mechanical properties of stent structure [1][2][3], only a few [4][5][6] were found on the design parameters of balloon-expandable stents. In addition, there are no reports relating to the design of a magnesium alloy stent.…”