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Khatami M, Doniavi A, Abazari AM, Fotouhi M. Enhancing flexibility and strength-to-weight ratio of polymeric stents: A new variable-thickness design approach. J Mech Behav Biomed Mater 2024; 150:106262. [PMID: 38029464 DOI: 10.1016/j.jmbbm.2023.106262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 12/01/2023]
Abstract
This paper presents a new design strategy to improve the flexibility and strength-to-weight ratio of polymeric stents. The proposed design introduces a variable-thickness (VT) stent that outperforms conventional polymeric stents with constant thickness (CT). While polymeric stents offer benefits like flexibility and bioabsorption, their mechanical strength is lower compared to metal stents. To address this limitation, thicker polymer stents are used, compromising flexibility and clinical performance. Leveraging advancements in 3D printing, a new design approach is introduced in this study and is manufactured by the Liquid Crystal Display (LCD) 3D printing method and PLA resin. The mechanical performance of CT and VT stents is compared using the Finite Element Method (FEM), validated by experimental tests. Results demonstrate that the VT stent offers significant improvements compared to a CT stent in bending stiffness (over 20%), reduced plastic strain distribution of expansion (over 26%), and increased radial strength (over 10%). This research showcases the potential of the VT stent design to enhance clinical outcomes and patient care.
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Affiliation(s)
- Mohamad Khatami
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Ali Doniavi
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Amir Musa Abazari
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Mohammad Fotouhi
- Department of Materials, Mechanics, Management & Design (3MD), Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, the Netherlands.
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2
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Wang Q, Huang S, Miao J, Chen Z, Li H, Zhao L, Yuan J. Impact of inverse unequal height strut structure on the functional performance of an additively manufactured cardiovascular stent. J Mech Behav Biomed Mater 2023; 146:106058. [PMID: 37549521 DOI: 10.1016/j.jmbbm.2023.106058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/29/2023] [Accepted: 07/31/2023] [Indexed: 08/09/2023]
Abstract
Recently, additive manufacturing (AM) has been investigated as an innovative method to manufacture stents due to its capability in producing complex and customized structures. In this paper, the cardiovascular stents of M-type and N-type with inverse unequal height strut structure and N-type with equal height strut structure were designed and manufactured by Selective Laser Melting (SLM). Following surface polishing, balloon expansion, plane compression and three-point bending experiments were carried out to evaluate the mechanical performance of the stent. The stents designed with inverse unequal height strut structure showed higher radial support performance and lower radial recoil when compared to the stents with uniform design. This study proved the feasibility of SLM in rapid manufacturing of cardiovascular stents that can be used for performance evaluation in design stage.
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Affiliation(s)
- Qilong Wang
- School of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan, 056038, China
| | - Suxia Huang
- School of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan, 056038, China; School of Mechanical Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Jingtao Miao
- School of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan, 056038, China
| | - Zhiang Chen
- School of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan, 056038, China
| | - Hezong Li
- School of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan, 056038, China; Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province, Handan, 056038, China.
| | - Liguo Zhao
- School of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
| | - Jiangyong Yuan
- Affiliated Hospital of Hebei Engineering University, Handan, 056001, China
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3
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Evaluation of coronary stents: A review of types, materials, processing techniques, design, and problems. Heliyon 2023; 9:e13575. [PMID: 36846695 PMCID: PMC9950843 DOI: 10.1016/j.heliyon.2023.e13575] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 01/22/2023] [Accepted: 02/02/2023] [Indexed: 02/11/2023] Open
Abstract
In the world, one of the leading causes of death is coronary artery disease (CAD). There are several ways to treat this disease, and stenting is currently the most appropriate way in many cases. Nowadays, the use of stents has rapidly increased, and they have been introduced in various models, with different geometries and materials. To select the most appropriate stent required, it is necessary to have an analysis of the mechanical behavior of various types of stents. The purpose of this article is to provide a complete overview of advanced research in the field of stents and to discuss and conclude important studies on different topics in the field of stents. In this review, we introduce the types of coronary stents, materials, stent processing technique, stent design, classification of stents based on the mechanism of expansion, and problems and complications of stents. In this article, by reviewing the biomechanical studies conducted in this field and collecting and classifying their results, a useful set of information has been presented to continue research in the direction of designing and manufacturing more efficient stents, although the clinical-engineering field still needs to continue research to optimize the design and construction. The optimum design of stents in the future is possible by simulation and using numerical methods and adequate knowledge of stent and artery biomechanics.
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Vellaparambil R, Han WS, Di Giovanni P, Avril S. Potential of auxetic designs in endovascular aortic repair: A computational study of their mechanical performance. J Mech Behav Biomed Mater 2023; 138:105644. [PMID: 36608533 DOI: 10.1016/j.jmbbm.2022.105644] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/01/2022] [Accepted: 12/25/2022] [Indexed: 12/27/2022]
Abstract
With the rising popularity of endovascular aortic repair (EVAR) for aortic aneurysms and dissections, there is a crucial need for investigating the delayed appearance of post-EVAR complications such as stent-graft kinking, fracture and migration respectively. These complications have been noted to be influenced by the radial stiffness and bending flexibility attributes of stent-grafts. Auxetic designs with negative Poisson's ratio offer interesting advantages such as enhanced fracture toughness, superior indentation resistance and adaptive stiffness in response to intricate morphology for stenting applications over conventional stent designs. The objective of this study is to propose different auxetic stent candidates and to compare their mechanical performance with two conventional stent candidates for endovascular applications using numerical simulation through crimp/crushing tests for their radial stiffness and three-point bending/kinking tests for their flexibility, respectively. The results demonstrate that the novel hybrid auxetic designs (CRE and CSTAR) possess the best trade-off between radial stiffness and bending flexibility characteristics among all candidates for stent-graft applications.
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Affiliation(s)
- Rahul Vellaparambil
- Mines Saint-Etienne, Univ Lyon, Univ Jean Monnet, Etablissement Francais du Sang, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Etienne, France; R&D Department, HSL S.R.L, Trento, Italy
| | - Woo-Suck Han
- Mines Saint-Etienne, Univ Lyon, Univ Jean Monnet, Etablissement Francais du Sang, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Etienne, France
| | | | - Stéphane Avril
- Mines Saint-Etienne, Univ Lyon, Univ Jean Monnet, Etablissement Francais du Sang, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Etienne, France.
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Pan C, Zeng X, Han Y, Lu J. Investigation of braided stents in curved vessels in terms of "Dogbone" deformation. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2022; 19:5717-5737. [PMID: 35603375 DOI: 10.3934/mbe.2022267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
"Dogbone" deformation that the diameters of two ends are larger than the middle diameter of the stent under the effect of the balloon expanding, is one of the important standards to evaluate the mechanical properties of vascular stents. It is a huge challenge to simulate and evaluate the "Dogbone" behaviors of braided stents in the curved vessels. In this study, the key work was to investigate the "Dogbone" deformations of braided stents in the curved vessels by designing main parameters including strut diameter, braiding angle, and the circumferential number of unit cell. Based on the "Dogbone" stents in the curved vessels, the impact of "Dogbone" on the fatigue properties of braided stents was analyzed under the pulsatile effect of vessels. The influence of "Dogbone" stents on stress distribution of vascular walls was studied. To evaluate the "Dogbone" behaviors of stents in the curved vessels, the calculation method of "Dogbone" was improved by calculating the centerline and the bus bar of the curved vessels. Braided stents with various parameters (strut diameter t = 100,125 and 152 μm, braiding angle α = 30, 40 and 50°, the circumferential number of unit cell N = 8, 10, and 12) were designed respectively. Numerical simulation method was used to mimic the "Dogbone" deformation after stent expansion. The results showed that strut diameter and braiding angle had more influence on "Dogbone" deformations than the circumferential number of unit cell. "Dogbone" deformation could adversely affect fatigue performance and vascular walls.
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Affiliation(s)
- Chen Pan
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
- Institute of Engineering Medicine, Beijing Institute of Technology, Beijing 100081, China
| | - Xinyun Zeng
- Institute of Engineering Medicine, Beijing Institute of Technology, Beijing 100081, China
| | - Yafeng Han
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Jiping Lu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
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Li Y, Wang Y, Shen Z, Miao F, Wang J, Sun Y, Zhu S, Zheng Y, Guan S. A biodegradable magnesium alloy vascular stent structure: Design, optimisation and evaluation. Acta Biomater 2022; 142:402-412. [PMID: 35085798 DOI: 10.1016/j.actbio.2022.01.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 01/05/2022] [Accepted: 01/18/2022] [Indexed: 02/07/2023]
Abstract
The existing biodegradable magnesium alloy stent (BMgS) structure is prone to problems, such as insufficient support capacity and early fracture at areas of concentrated stress. Herein, a stent structural design, which reduced the cross section of the traditional sin-wave stent by nearly 30% and introduces a regular arc structure in the middle of the support ring. The influence of the dual-parameter design of bending radius (r) and ring length (L) on plastic deformation, expansion and compression resistance performances are discussed. The non-dominated sorting genetic algorithm II (NSGA-II) was used to search for the optimal solution. It was found that the introduction of parameter r effectively improved the plastic deformation and expansion performance, and the reduction of L improved stent compression resistance. Finally, an optimized stent configuration was obtained. In vitro mechanical tests, including balloon inflation, radial strength and flexibility, verified the simulation results. The radial strength for the optimised stent increases by approximately 40% compared with that for the sinusoidal stent. Microarea X-ray diffraction result shows that the circumferential residual stress for the optimised stent decreases by half compared with that for the sinusoidal stent, thus effectively reducing the stress concentration phenomenon. STATEMENT OF SIGNIFICANCE: Despite current progress in BMgS research, the optimal design of the structure is limited. We present a new type of structurally designed stent. The performance of this stent was analysed by a finite element method and experimentally verified. The structural design positively influenced stent performance.
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Affiliation(s)
- Yafei Li
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Yan Wang
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Zhenquan Shen
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Fulong Miao
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Jianfeng Wang
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China; Henan Key Laboratory of Advanced Magnesium Alloys, Zhengzhou 450002, China; Key Laboratory of Advanced Materials Processing & Mold Ministry of Education, Zhengzhou 450002, China
| | - Yufeng Sun
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China; Henan Key Laboratory of Advanced Magnesium Alloys, Zhengzhou 450002, China; Key Laboratory of Advanced Materials Processing & Mold Ministry of Education, Zhengzhou 450002, China
| | - Shijie Zhu
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China; Henan Key Laboratory of Advanced Magnesium Alloys, Zhengzhou 450002, China; Key Laboratory of Advanced Materials Processing & Mold Ministry of Education, Zhengzhou 450002, China
| | - Yufeng Zheng
- School of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Shaokang Guan
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China; Henan Key Laboratory of Advanced Magnesium Alloys, Zhengzhou 450002, China; Key Laboratory of Advanced Materials Processing & Mold Ministry of Education, Zhengzhou 450002, China.
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7
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Characterizing the Mechanical Performance of a Bare-Metal Stent with an Auxetic Cell Geometry. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12020910] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This study develops and characterizes the distinctive mechanical features of a stainless-steel metal stent with a tailored structure. A high-precision femtosecond laser was used to micromachine a stent with re-entrant hexagonal (auxetic) cell geometry. We then characterized its mechanical behavior under various mechanical loadings using in vitro experiments and through finite element analysis. The stent properties, such as the higher capability of the stent to bear upon bending, exceptional advantage at elevated levels of twisting angles, and proper buckling, all ensured a preserved opening to maintain the blood flow. The outcomes of this preliminary study present a potential design for a stent with improved physiologically relevant mechanical conditions such as longitudinal contraction, radial strength, and migration of the stent.
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Pan C, Han Y, Lu J. Structural Design of Vascular Stents: A Review. MICROMACHINES 2021; 12:mi12070770. [PMID: 34210099 PMCID: PMC8305143 DOI: 10.3390/mi12070770] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/16/2021] [Accepted: 06/24/2021] [Indexed: 11/18/2022]
Abstract
Percutaneous Coronary Intervention (PCI) is currently the most conventional and effective method for clinically treating cardiovascular diseases such as atherosclerosis. Stent implantation, as one of the ways of PCI in the treatment of coronary artery diseases, has become a hot spot in scientific research with more and more patients suffering from cardiovascular diseases. However, vascular stent implanted into vessels of patients often causes complications such as In-Stent Restenosis (ISR). The vascular stent is one of the sophisticated medical devices, a reasonable structure of stent can effectively reduce the complications. In this paper, we introduce the evolution, performance evaluation standards, delivery and deployment, and manufacturing methods of vascular stents. Based on a large number of literature pieces, this paper focuses on designing structures of vascular stents in terms of “bridge (or link)” type, representative volume unit (RVE)/representative unit cell (RUC), and patient-specific stent. Finally, this paper gives an outlook on the future development of designing vascular stents.
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Affiliation(s)
- Chen Pan
- School of Mechanical Engineering, Beijing Institute of Technology, Zhongguancun South Street No. 5, Haidian District, Beijing 100081, China; (C.P.); (J.L.)
- Institute of Engineering Medicine, Beijing Institute of Technology, Zhongguancun South Street No. 5, Haidian District, Beijing 100081, China
| | - Yafeng Han
- School of Mechanical Engineering, Beijing Institute of Technology, Zhongguancun South Street No. 5, Haidian District, Beijing 100081, China; (C.P.); (J.L.)
- Correspondence:
| | - Jiping Lu
- School of Mechanical Engineering, Beijing Institute of Technology, Zhongguancun South Street No. 5, Haidian District, Beijing 100081, China; (C.P.); (J.L.)
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PANNEERSELVAM NISANTHKUMAR, MUTHUSWAMY SREEKUMAR. DESIGN AND ANALYSIS OF NEW STENT PATTERNS FOR ENHANCED PERFORMANCE. J MECH MED BIOL 2020. [DOI: 10.1142/s0219519420500396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Deploying a stent to restore blood flow in the coronary artery is very complicated, as its internal diameter is smaller than 3[Formula: see text]mm. It has already been proven that mechanical stresses induced on stent and artery during deployment make the placement of stent very difficult, besides the development of complications due to artery damage. Various stent designs have already been developed, especially in the metallic category. Still, there are possibilities for developing new stent designs and patterns to overcome the complexities of the existing models. Also, the technology of metallic stents can be carried forward towards the development of bioresorbable polymeric stents. In this work, three new stent cell designs (curvature, diamond, and oval) have been proposed to obtain better performance and life. The finite element method is utilized to explore the mechanical behavior of stent expansion and determine the biomechanical stresses imposed on the stent and artery during the stenting procedure. The results obtained have been compared with the available literature and found that the curvature cell design develops lower stresses and, hence, be suitable for better performance and life.
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Affiliation(s)
- NISANTHKUMAR PANNEERSELVAM
- Department of Mechanical Engineering, Indian Institute of Information Technology, Design and Manufacturing, Kancheepuram Chennai 600127, India
| | - SREEKUMAR MUTHUSWAMY
- Department of Mechanical Engineering, Indian Institute of Information Technology, Design and Manufacturing, Kancheepuram Chennai 600127, India
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Xue H, Luo Z, Brown T, Beier S. Design of Self-Expanding Auxetic Stents Using Topology Optimization. Front Bioeng Biotechnol 2020; 8:736. [PMID: 32766219 PMCID: PMC7381139 DOI: 10.3389/fbioe.2020.00736] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 06/10/2020] [Indexed: 01/08/2023] Open
Abstract
Implanting stents is the most efficient and minimally invasive technique for treating coronary artery diseases, but the risks of stent thrombosis (ST) and in-stent restenosis (IRS) hamper the healing process. There have been a variety of stents in market but dominated by ad hoc design motifs. A systematic design method that can enhance deliverability, safety and efficacy is still in demand. Most existing designs are focused on patient and biological factors, while the mechanical failures related to stenting architectures, e.g., inadequate stent expansion, stent fracture, stent malapposition and foreshortening, are often underestimated. With regard to these issues, the self-expanding (SE) stents may perform better than balloon-expandable (BE) stents, but the SE stents are not popular in clinic practice due to poor deliverability, placement accuracy, and precise match of the stent size and shape to the vessel. This paper addresses the importance between stent structures and clinic outcomes in the treatment of coronary artery disease. First, a concurrent topological optimization method will be developed to systematically find the best material distribution within the design domain. An extended parametric level set method with shell elements is proposed in the topology optimization to ensure the accuracy and efficiency of computations. Second, the auxetic metamaterial with negative Poisson’s ratio is introduced into the self-expanding stents. Auxetics can enhance mechanical properties of structures, e.g., fracture toughness, indentation and shear resistance and vibration energy absorption, which will help resolve the drawbacks due to the mechanical failures. Final, the optimized SE stent is numerically validated with the commercial software ANSYS and then prototyped using additive manufacturing techniques. Topological optimization gives a rare opportunity to exploiting the unique advantages of additive manufacturing. Hence, the topologically optimized auxetic architectures will provide a new solution for developing novel stenting structures, especially conductive to self-expanding SE stents. The new design will overcome the limitations of conventional SE stents associated with mechanical structures while maintain their valuable features, to help reduce the occurrence of ST and ISR and benefit the clinic practice in treating coronary heart disease.
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Affiliation(s)
- Huipeng Xue
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, NSW, Australia
| | - Zhen Luo
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, NSW, Australia
| | - Terry Brown
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, NSW, Australia
| | - Susann Beier
- School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW, Australia
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Praveen Kumar G, Louis Commillus A, Cui F. A finite element simulation method to evaluate the crimpability of curved stents. Med Eng Phys 2019; 74:162-165. [PMID: 31635945 DOI: 10.1016/j.medengphy.2019.07.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/15/2019] [Accepted: 07/28/2019] [Indexed: 10/25/2022]
Abstract
Stenting of curved arteries is more challenging than straight vessels. There has been an increasing need for new techniques to treat lesions in highly curved locations. One generic idea is to use curved stents to treat lesions in such curved locations. Computational modeling of straight stent crimping which is being used to evaluate the structural performance of the stents has been done vastly in the past. However, there has not been much simulation work on crimping of curved stents due to the challenges associated with applying the boundary conditions. Here we propose a new method to crimp a curved stent to a smaller diameter by incorporating a simple algorithm to generate the required boundary conditions supplementing the finite element (FE) code. To achieve this, a curved crimper is modeled and used to apply crimping loading on the curved stent evaluate its crimpability. Our method provides a simple yet very useful tool which can be implemented in finite element packages to simulate crimping of curved stents using curved crimpers. This method can also be used to expand balloon expandable stents by inflating curved balloons.
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Affiliation(s)
| | | | - Fangsen Cui
- Institute of High Performance Computing, A*STAR, 138632, Singapore
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