Analytical methods for braided stents design and comparison with FEA

Zaccaria, Alissa; Pennati, Giancarlo; Petrini, Lorenza

doi:10.1016/j.jmbbm.2021.104560

Cited by 19 publications

(13 citation statements)

References 30 publications

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“…The friction constraint model between monofilaments is shown in Figure 6b. Zaccaria et al studied the radial strength of stents with different braided structures by finite element analysis and showed that the contact pressure at the contact point of single wire was obviously large 38 . Therefore, the increase in the number of contact points ( N p ) will increase the radial strength.…”

Section: Resultsmentioning

confidence: 99%

“…Zaccaria et al studied the radial strength of stents with different braided structures by finite element analysis and showed that the contact pressure at the contact point of single wire was obviously large. 38 Therefore, the increase in the number of contact points (N p ) will increase the radial strength. It can be clearly found that the friction contact points between monofilaments increase after adding axial stiffeners, so the constraint effect is enhanced.…”

Section: Analytical Model Of Constraints Between Monofilamentsmentioning

confidence: 99%

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Evaluation of mechanical properties of poly(L‐lactic acid) braided stents with axial stiffeners

Zhao

Liu

Tian

et al. 2022

J of Applied Polymer Sci

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Poly(L-lactic acid) (PLLA) has been widely used in constructing biodegradable braided stents due to high biocompatibility and biodegradability. However, poor mechanical properties of this stent are main weaknesses. In this paper, the mechanical properties of PLLA braided stents containing axial stiffeners were evaluated. The stents with stiffener diameters of 0.11, 0.19 and 0.28 mm are named SS11, SS19 and SS28, respectively, and the stent without stiffener is named SS00 as control. The results show that compared with SS00, the bending stiffness of SS11, SS19 and SS28 is increased by 0.77, 1.76, and 2.70 times, respectively. Meanwhile, chronic outward force at an indicated use diameter of 5 mm is increased by 0.83, 0.50, and 0.21 times, but elastic recovery rate is decreased by 5.6%, 14.6%, 22.5%. In addition, radial stiffness of SS11, SS19, and SS28 are increased by 2.81, 2.08 and 1.62 times, respectively. Therefore, the radial support performance is improved and the bending flexibility is weakened by adding stiffeners. Taken together, SS11 can provide sufficient radial support force and low axial force in clinical applications. This study may provide a reference for optimizing the mechanical properties of the biodegradable braided stents.

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Section: Resultsmentioning

confidence: 99%

Section: Analytical Model Of Constraints Between Monofilamentsmentioning

confidence: 99%

Evaluation of mechanical properties of poly(L‐lactic acid) braided stents with axial stiffeners

Zhao

Liu

Tian

et al. 2022

J of Applied Polymer Sci

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“…The difference might be explained by different deformations under their corresponding loading conditions. During the radial crimping, the straight cylindrical braided stent undergoes a change in the pitch angles, resulting in a diameter reduction as well as a longitudinal elongation of the whole device [ 25 , 26 ]. Applying axial loading, the double-disc braided occluder undergoes obvious bending of the loading disc, besides elongation and change in the pitch angles.…”

Section: Discussionmentioning

confidence: 99%

A Finite Element Investigation on Material and Design Parameters of Ventricular Septal Defect Occluder Devices

Zhang

Xiong

Hu³

et al. 2022

JFB

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Background and Objective: Ventricular septal defects (VSDs) are the most common form of congenital heart defects. The incidence of VSD accounts for 40% of all congenital heart defects (CHDs). With the development of interventional therapy technology, transcatheter VSD closure was introduced as an alternative to open heart surgery. Clinical trials of VSD occluders have yielded promising results, and with the development of new material technologies, biodegradable materials have been introduced into the application of occluders. At present, the research on the mechanical properties of occluders is focused on experimental and clinical trials, and numerical simulation is still a considerable challenge due to the braided nature of the VSD occluder. Finite element analysis (FEA) has proven to be a valid and efficient method to virtually investigate and optimize the mechanical behavior of minimally invasive devices. The objective of this study is to explore the axial resistive performance through experimental and computational testing, and to present the systematic evaluation of the effect of various material and braid parameters by FEA. Methods: In this study, an experimental test was used to investigate the axial resistive force (ARF) of VSD Nitinol occluders under axial displacement loading (ADL), then the corresponding numerical simulation was developed and compared with the experimental results to verify the effectiveness. Based on the above validation, numerical simulations of VSD occluders with different materials (polydioxanone (PDO) and Nitinol with different austenite moduli) and braid parameters (wire density, wire diameter, and angle between left and right discs) provided a clear presentation of mechanical behaviors that included the maximal axial resistive force (MARF), maximal axial displacement (MAD) and initial axial stiffness (IAS), the stress distribution and the maximum principal strain distribution of the device under ADL. Results: The results showed that: (1) In the experimental testing, the axial resistive force (ARF) of the tested occluder, caused by axial displacement loading (ADL), was recorded and it increased linearly from 0 to 4.91 N before reducing. Subsequent computational testing showed that a similar performance in the ARF was experienced, albeit that the peak value of ARF was smaller. (2) The investigated design parameters of wire density, wire diameter and the angle between the left and right discs demonstrated an effective improvement (7.59%, 9.48%, 1.28%, respectively, for MARF, and 1.28%, 1.80%, 3.07%, respectively, for IAS) for the mechanical performance for Nitinol occluders. (3) The most influencing factor was the material; the performance rose by 30% as the Nitinol austenite modulus (EA) increased by 10,000 MPa. The performance of Nitinol was better than that of PDO for certain wire diameters, and the performance improved more obviously (1.80% for Nitinol and 0.64% for PDO in IAS, 9.48% for Nitinol and 2.00% for PDO in MARF) with the increase in wire diameter. (4) For all of the models, the maximum stresses under ADL were distributed at the edge of the disc on the loaded side of the occluders. Conclusions: The experimental testing presented in the study showed that the mechanical performance of the Nitinol occluder and the MARF prove that it has sufficient ability to resist falling out from its intended placement. This study also represents the first experimentally validated computational model of braided occluders, and provides a perception of the influence of geometrical and material parameters in these systems. The results could further provide meaningful suggestions for the design of biodegradable VSD closure devices and to realize a series of applications for biodegradable materials in VSD.

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“…Numerical simulation is an effective method for analyzing the mechanical performances of stents. It has high accuracy and requires fewer resources (Zaccaria et al, 2021), and it can also be used to design and optimize stents (Balossino et al, 2008). Záhora et al derived the equations of the physical model for the spiral stent to describe the mutual transformation between the axial force and Frontiers in Bioengineering and Biotechnology frontiersin.org the radial pressure (Záhora et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, the influence of geometric features of braided metal stents, including wire diameter and wire density, have been predicted under radial compression ( Fu et al, 2018 ), localized radial compression ( Kim et al, 2008 ), bending ( Fu et al, 2018 ; Zaccaria et al, 2020 ) and elongation ( De Beule et al, 2009 ). Furthermore, the finite element method (FEM) has been widely used to investigate stent mechanics ( Tan et al, 2001 ; McKenna and Vaughan, 2021 ; Zaccaria et al, 2021 ). Yet, there are still no studies on the mechanical properties of the nasal stent, and the influence of geometric parameters on the performance of the stent remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Mechanical property analysis and design parameter optimization of a novel nitinol nasal stent based on numerical simulation

Huang

Zheng

Qiu

et al. 2022

Front. Bioeng. Biotechnol.

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Background: A novel braided nasal stent is an effective alternative to nasal packing after septoplasty that can be used to manage the mucosal flap after septoplasty and expand the nasal cavity. This study aimed to investigate the influence of design parameters on the mechanical properties of the nasal stent for optimal performance.Methods: A braided nasal stent modeling method was proposed and 27 stent models with a range of different geometric parameters were built. The compression behavior and bending behavior of these stent models were numerically analyzed using a finite element method (FEM). The orthogonal test was used as an optimization method, and the optimized design variables of the stent with improved performance were obtained based on range analysis and weight grade method.Results: The reaction force and bending stiffness of the braided stent increased with the wire diameter, braiding density, and external stent diameter, while wire diameter resulted as the most important determining parameter. The external stent diameter had the greatest influence on the elongation deformation. The influence of design parameters on von-Mises stress distribution of bent stent models was visualized. The stent model with geometrical parameters of 25 mm external diameter, 30° braiding angle, and 0.13 mm wire diameter (A3B3C3) had a greater reaction force but a considerably smaller bending stiffness, which was the optimal combination of parameters.Conclusion: Firstly, among the three design parameters of braided stent models, wire diameter resulted as the most important parameter determining the reaction force and bending stiffness. Secondly, the external stent diameter significantly influenced the elongation deformation during the compression simulation. Finally, 25 mm external diameter, 30° braiding angle, and 0.13 mm wire diameter (A3B3C3) was the optimal combination of stent parameters according to the orthogonal test results.

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Analytical methods for braided stents design and comparison with FEA

Cited by 19 publications

References 30 publications

Evaluation of mechanical properties of poly(L‐lactic acid) braided stents with axial stiffeners

Evaluation of mechanical properties of poly(L‐lactic acid) braided stents with axial stiffeners

A Finite Element Investigation on Material and Design Parameters of Ventricular Septal Defect Occluder Devices

Mechanical property analysis and design parameter optimization of a novel nitinol nasal stent based on numerical simulation

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