Numerical research on the biomechanical behaviour of braided stents with different end shapes and stent‐oesophagus interaction

Abstract

Quasi-static and dynamic numerical analyses are carried out by referring to computational models of commercial self-expandable braided stents with 3 commonly used end shapes, to evaluate the influence of different end shapes of stent on the biomechanical interaction between stent and oesophagus. The end shape has no influence on the equivalent stress, but has a great influence on the contact stress in the narrowest zone of the oesophagus-neoplasm system. However, the end shapes have significant effect on the equivalent stress and the contact stress in the healthy area of the oesophagus in contact with the stent ends. The results show that the maximum equivalent stress of the oesophagus occurs in the zone contact with the cup-shaped end and the maximum contact stress occurs in the zone contact with the edge of the trumpet-shaped stent end. Moreover, the stent apposition is almost not affected by the end shapes. Although small zones with an incomplete stent apposition appear in the transition zones of spherical-cup-shaped stent, such occurrence might not contribute to stent malapposition or stent migration. Therefore, these stents with 3 types of end shapes all have good stent apposition. Finally, the numerical simulation results can be used to assess the mechanical performance of stents with different end shapes, the effectiveness of stent expansion therapy, and the possibility of complications after stent implantation.

Computational modeling of braided‐stent deployment for interpreting the mechanism of stent flattening

“…Much attention has been paid to the mechanical characteristics of the braided stent because of the stent's increasing clinical importance, and computational approaches have greatly contributed to clarifying apparent mechanical properties of the stent 18‐25 . Several numerical experiments that consider detailed mechanical characteristics of stent wires, such as the material nonlinearity 18,20,21,24 and three‐dimensional stress‐field, 21,22,25 have been conducted. This study also conducted a computational mechanical analysis of the braided stent; however, the motivation and aim of this study are different from those of existing computational studies.…”

“…To remedy this issue, theoretical models of the braided stent have been proposed for estimating the radial forces of the braided stent for self‐expansion, in which the braided stent is modeled as an assembly of single helical springs 14‐17 . Numerical experiments using mechanically consistent computational models are also expected to be an effective alternative and several studies have attempted quantitative estimation of apparent mechanical characteristics of the braided stent 18‐29 . These numerical experiments considered material nonlinearities of stent wires (ie, superelasticity 18,20,21 and viscoelasticity 24 ), three‐dimensional (3‐D) mechanics within the wire cross‐sections through discretization of 3‐D volume meshes, 21 and structural design of the braided stent 19,22,23,25 and performed quantitative validations by conducting experiments and assessments of the stent mechanical characteristics.…”

“…Numerical experiments using mechanically consistent computational models are also expected to be an effective alternative and several studies have attempted quantitative estimation of apparent mechanical characteristics of the braided stent 18‐29 . These numerical experiments considered material nonlinearities of stent wires (ie, superelasticity 18,20,21 and viscoelasticity 24 ), three‐dimensional (3‐D) mechanics within the wire cross‐sections through discretization of 3‐D volume meshes, 21 and structural design of the braided stent 19,22,23,25 and performed quantitative validations by conducting experiments and assessments of the stent mechanical characteristics. However, existing computational evaluations mainly focused on basic apparent characteristics of the braided stent, such as the radial stiffness, 18,19,25,28 apparent axial rigidity, 21,22,24 and flexural rigidity 18,22,23 because the models have a high computational cost.…”

“…These numerical experiments considered material nonlinearities of stent wires (ie, superelasticity 18,20,21 and viscoelasticity 24 ), three‐dimensional (3‐D) mechanics within the wire cross‐sections through discretization of 3‐D volume meshes, 21 and structural design of the braided stent 19,22,23,25 and performed quantitative validations by conducting experiments and assessments of the stent mechanical characteristics. However, existing computational evaluations mainly focused on basic apparent characteristics of the braided stent, such as the radial stiffness, 18,19,25,28 apparent axial rigidity, 21,22,24 and flexural rigidity 18,22,23 because the models have a high computational cost. Hence, underlying mechanisms of inadequate stent expansion, such as stent flattening and the fish‐mouth phenomenon, are still poorly understood.…”

Fatigue behavior of stent in tapered arteries: The role of arterial tapering and stent material

“…10 With the rapid development of computer technology, finite element analysis (FEA) technology has been widely used in cardiovascular disease researches due to its high efficiency and low cost. [11][12][13][14][15][16] Whitcher 17 adopted FEA to conduct fatigue analysis on the nitinol stent and highlighted that the simulation results were in good agreement with in vitro experiment. Auricchio et al, 18 by simulating the fatigue resistance of stents under cyclic bending and pulsation pressure loads, found that stents were more likely to become invalid under cyclic bending loads.…”