Radial Strength Research Articles

Evaluation on the structure and mechanical property of crimped woven vascular graft with continuous variable cross-sections

To improve the clinical performance of textile vascular graft, a crimping treatment was applied on the prepared woven vascular graft prototypes with continuous variable cross-sections (CVCW vascular graft), then the structure and mechanical properties of crimped CVCW vascular graft woven samples with different fabric weaves and conical angles were evaluated. The results indicated that the corrugation wall structure of the crimped CVCW vascular graft was still uniform after the crimping treatment, while both their average pore size and the water permeability decreased. On the other hand, the stress-strain behavior of the crimped woven CVCW vascular grafts obeyed the BoxLucas equation. Further, all of the radial compression strength (>15cN), the bursting strength (>15Mpa) and the radial compliance (0.85%) of the crimped CVCW vascular grafts were greatly improved, but the elastic recovery was reduced in comparison with the round straight tubular graft. Generally, this work demonstrated the good performance of the crimped CVCW vascular grafts for future clinical practice, as well as the feasibility of the crimping treatment techniques in improving the biomimetic design of woven CVCW vascular graft.

Material Analysis of a Sample Airless Wheel That Can Be Used in The Landing Gear of Small UAVs for Smart Agriculture Using the Finite Element Method

Unmanned Aerial Vehicles (UAV) in categories 1 and 2 are small in size and have a maximum gross take-off weight between 5 - 40 N and 40 - 250 N, with a normal operating altitude of 120 m above ground level. One of the major concerns for UAVs is the weight of aerial vehicles, which is aided primarily by material changes. Tires for UAVs are primarily made of ABS, rubber silicone, and nylon to reduce flight problems. These tires add to the dead weight and drag during flight.
 In response to these issues, a rigorous analysis was performed to select the best possible configuration using various materials such as Acrylonitrile Butadiene Styrene (ABS), rubber silicone, and nylon materials. UAV wheel manufacturing is commonly known as the production of high-strength light-weighing parts. It also provides a broader range of design options and favors an iterative design approach, so it is important the method of production. To achieve the best results, the iterative design approach was used in the analysis application. The study incorporated a design for airless tires with 40 spokes, leveraging Autodesk Inventor Pro for modeling. Subsequently, the designs underwent Finite Element Analysis to assess static radial strength. Bending and torsion stresses during landing were deemed negligible owing to the lightweight nature of categories 1 and 2 UAVs and were thus excluded from the analysis.
 The modeled wheel design in Autodesk Inventor Pro analysis based on Finite Element Analysis of the airless wheels revealed that wheels made of rubber silicone exhibited superior shock absorption, with a deformation of only 2.314 mm at 625 N upon impact during UAV landing maneuvers.

Shape Morphing of Tubular Structures with Tailorable Mechanical Properties

Tubular structures are in high demand in robotics, medicine, and electronics. They are expected to match different shapes under loading and simultaneously exhibit certain mechanical behavior, e.g., specific radial strength and local flexibility, that poses a complex engineering design task. Herein, strategies to achieve programmable shape morphing in patterned tubular structures are explored, whose mechanical properties for all types of deformation modes can be tailored on demand. The general design problem is formulated, and the programmable response for fundamental—expansion, bending, and twisting—modes activated by tension and pressurization is demonstrated. The design problem for expansion modes is solved analytically; the numerical results agree well with the experimental data for stereolithography three‐dimensional printed cellular tubes. The effects of loading and boundary conditions on the deformed shapes and the structural mechanical response are analyzed. Algorithm‐based design strategies are proposed to achieve quantitative and automatic design for complex deformation modes. The possible use of the proposed structures is also discussed with respect to several applications. The findings pave the way for multifunctional tubular structures by exploring the pluridimensional space of the geometric parameters of metamaterial patterns.

Magnetohydrodynamical Torsional Oscillations from Thermoresistive Instability in Hot Jupiters

Hot Jupiter atmospheres may be subject to a thermoresistive instability where an increase in the electrical conductivity due to ohmic heating results in runaway of the atmospheric temperature. We introduce a simplified one-dimensional model of the equatorial substellar region of a hot Jupiter that includes the temperature dependence and time dependence of the electrical conductivity, as well as the dynamical back-reaction of the magnetic field on the flow. This model extends our previous one-zone model to include the radial structure of the atmosphere. Spatial gradients of electrical conductivity strongly modify the radial profile of Alfvénic oscillations, leading to steepening and downward transport of magnetic field, enhancing dissipation at depth. We find unstable solutions that lead to self-sustained oscillations for equilibrium temperatures in the range T eq ≈ 1000–1200 K and radial magnetic field strength in the range ≈10–100 G. For a given set of parameters, self-sustained oscillations occur in a narrow range of equilibrium temperatures that allow the magnetic Reynolds number to alternate between large and small values during an oscillation cycle. With our simplified geometry, outside of this temperature window the system reaches a steady state in which the effect of the magnetic field can be approximated as a magnetic drag term. Our results show that thermoresistive instability is a possible source of variability in magnetized hot Jupiters at colder temperatures and emphasize the importance of including the temperature dependence of electrical conductivity in models of atmospheric dynamics.

Enhancing decellularized vascular scaffolds with PVDF and PCL reinforcement: a fused deposition modeling approach

BackgroundDecellularized xenogenic scaffolds represent a promising substrate for tissue-engineered vascular prostheses, particularly those with smaller diameters (<6 mm). Despite their benefits, a notable limitation presents itself during decellularization, namely, the diminished mechanical strength that introduces the risk of aneurysmal dilations in the early post-implantation period. This study introduces a strategy for modification the mechanical properties of these biological scaffolds through the forming of an external polymeric reinforcement via thermal extrusion.MethodsThe study utilized scaffolds fabricated from bovine internal mammary arteries through decellularization and preservation. The scaffolds were divided into subgroups and reinforced with polymeric helices made of Polyvinylidene fluoride (PVDF) and Polycaprolactone (PCL), n = 5 for each. An experimental setup for external reinforcement coating was designed. Computed microtomography was employed to obtain accurate 3D models of the scaffolds. Mechanical properties were evaluated through in vitro uniaxial tension tests (Z50, Zwick/Roell, Germany), compliance evaluation and numerical simulations (Abaqus/CAE, Dassault Systemes, France) to investigate the effect of external reinforcement on aneurysm growth.ResultsUsing a double-layer helix for the reinforcement significantly enhanced the radial tensile strength of the scaffolds, increasing it up to 2.26 times. Yet, the comparison of vessel's compliance between two reinforced and the Control scaffolds within the physiological pressures range did not reveal any significant differences. Numerical simulation of aneurysm growth showed that thin-walled regions of the Control scaffold developed aneurysmal-type protrusions, bulging up to 0.7 mm, with a substantial degradation of mechanical properties. In contrast, both PVDF and PCL reinforced scaffolds did not exhibit significant property degradation, with deformations ranging 0.1–0.13 mm depending on the model, and a maximum decrease in the modulus of elasticity of 23%.ConclusionThe results of the study demonstrated that the external polymer helical reinforcement of decellularized scaffolds via thermal extrusion enables a controlled modification of mechanical properties, notably enhancing radial strength while maintaining sufficient compliance within the physiological pressure range. A series of in vitro tests demonstrated the consistency and potential of this approach for decellularized xenogenic scaffolds, a concept that had not been explored before.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Enhancing flexibility and strength-to-weight ratio of polymeric stents: A new variable-thickness design approach

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.

Fabrication and characterization of PLLA/PCL/Mg‐Zn‐Y alloy composite stent

AbstractBioresorbable polymeric stents (BPS) can become a promising alternative over permanent stents, as it reduce in‐stent thrombosis, endothelial dysfunction, and thrombogenicity. Although, a few limitations like uncontrolled degradation, inadequate strength, and lack of radiopacity restrict its application. Thus, a novel bioresorbable radiopaque Mg‐Zn‐Y Alloy (BRM) of high effective atomic number (Zeff) was developed to reinforce and attenuate X‐rays in the polymers. After that, the optimized BRM microparticles were blended with radiolucent poly (L‐lactide)/poly (ε‐caprolactone) (PLLA/PCL) polymer and extruded into biaxially expanded (BAE) tubes. Further, in this work, BAE tubes of PLLA/PCL/BRM and PLLA/PCL were cut using the optimized Femtosecond laser machine (FSLM) parameters for fabricating cardiovascular stents. These stent materials were assessed to sustain the angioplasty procedure, such as radial strength, crimping, recoil, expansion process, and performance under cycling loading.Highlights A novel biodegradable radiopaque Mg‐Zn‐Y alloy was developed. Adding Mg alloy (5% wt.) in PLLA/PCL imparts X‐ray visibility. Composite stents show better compressive radial strength and flexibility. It also reveals low crimping recoil, expansion recoil, and foreshortening. Composite stents can withstand arterial vasomotion better than PLLA/PCL.

Radial spectrum spread of Laguerre-Gaussian beam transmission in weak compressible turbulence

Turbulence effects can seriously affect the propagation of structured light, especially for orbital angular momentum (OAM) modes, causing spread and crosstalk. We derive an analytical solution to the mode spectrum of a Laguerre-Gaussian beam (LGB) propagating in weak compressible turbulence. The influence of the radial number and turbulence strength in the mode spectrum on the probability of LGB propagation is mainly considered. The results show that the weak compressible turbulence interferes strongly with the LGB, and this effect is mainly reflected in the sharp drop of the signal mode energy at short transmission distance. We find that the pure radial mode has a higher signal mode energy than the pure OAM mode, which means that the pure radial mode is more resilient to compressible turbulence than the pure OAM mode. In addition, the increase of radial number can improve the performance of the OAM dimension, but on the other hand, it reduces the probability of the radial dimension. Finally, we discussed the propagation properties of higher-order modes. Our research clarifies the interaction of OAM mode and radial mode in turbulence, and provides a theoretical basis for applications based on radial modes in the field of free-space communication.

MORPHOLOGICAL AND MECHANICAL ASSESSMENT OF ELECTROSPUN PLGA VASCULAR SCAFFOLDS

Cardiovascular disorders are the leading cause of global mortality and typically necessitate bypass surgery to replace the damaged blood vessel. Currently used grafts are insufficient to replace small-diameter blood vessels due to the scarcity and harsh harvesting procedure of autologous vessels and the shortcomings in the clinical performance of synthetic grafts, which might result in intimal hyperplasia, thrombosis, and compliance mismatch. Therefore, there is a critical need for tissue-engineered vascular grafts that can meet morphological, mechanical, and biological characteristics. In this study, poly(lactic-co-glycolic acid) tubular scaffolds with randomly distributed or radially oriented fibers were produced by electrospinning, and the effect of fiber orientation on morphological and mechanical properties was investigated. The findings demonstrate that, while the successful implementation of radial fiber orientation with high rotational speed production enhanced burst strength and radial tensile strength values, it was unfavorable for compliance.

Bioresorbable Vascular Scaffolds: Should We use Them Again?

Context: An important development in the percutaneous management of coronary artery disease was the creation of the drug-eluting stent (DES). The DES reduces the high incidence of target lesion revascularization associated with balloon angioplasty and bare metal stents by overcoming vessel recoil and restenosis. Despite these advantages, DES carries a persistent risk of stent-related problems due to the permanent implantation of a foreign body and the limitation of arterial vasomotion. Similar to DES, bioresorbable vascular scaffolds (BRS) are intended to distribute drugs and offer mechanical support before completely degrading over the years. Evidence Acquisition: This study was a review article. The data were acquired from PubMed and Google Scholar. Medical Subject Headings (MeSH) terms were used when available, and only English articles were included in the review. Results: Recent studies have shown that the BRS is not inferior to modern DES clinically, although some clinical results are worrying, particularly the greater rates of scaffold thrombosis. Early studies showed that BRS was superior to DES; nevertheless, larger-scale applications and longer observations revealed serious problems with their use, such as reduced radial strength and a higher risk of thrombosis, which led to a higher rate of serious adverse cardiac events. Conclusions: The position of DES was not directly challenged by additional attention to procedural details and research on the second generation of BRS with innovative features. Bioresorbable vascular scaffolds still have an opportunity to demonstrate their supremacy in standout indicators.

Optimized structure design of asymmetrical Mg alloy cerebrovascular stent with high flexibility

In the treatment of cerebral artery stenosis via stent intervention, it is required that the stent can pass through the tortuous blood vessel with high curvature to reach the lesion position smoothly, and the damage to the artery should be as small as possible. This determines that the coronary artery stent cannot be directly applied to the diseased cerebrovascular, but a specialized cerebrovascular stent with high flexibility should be specifically designed. Differing from the commonly employed symmetrical structure, in this work, an asymmetrical and unequal-heigh stent structure was designed, which helps to improve the flexibility of the stent and reduces the self-contact phenomenon that occurs after the ordinary stent is bent. To balance the comprehensive properties of the stent, multi-objective optimization on the stent structure was carried out. The optimized stent structure shows better radial strength and flexibility and does not significantly affect equivalent plastic strain after stent expansion and volume average stress. In addition, this work provides a universal workflow for the customized stent structure.

Delamination Strength Comparison of Additively Manufactured Composite Curved Beams Using Continuous Fibers.

The objective of this study is to show the applicability of various 3D-printed composite curved beams using continuous fibers and their delamination strength when they are subjected to bending loading. Four-point bending tests are configured for comparative research on evaluating the effect of fiber types on the delamination strength and failure mode. Out-of-plane tensile properties are calculated analytically by using experimental data. The number of curved beams per build during multiple printing is examined to observe the effect of delay time between each deposited layer of parts. Macro-scale finite element simulations including surface-based cohesive concept for the selected 3D-printed composite curved beam design are also presented and compared. The analytical results show that carbon fiber reinforced curved beam design is superior to the other fiber types by at least 18% in the interlaminar tensile strength and is relatively challenging against the conventionally manufactured composite curved beams in the literature despite its low fiber volume ratio. There is no gross effect of delay time between each deposited layer of parts, although printing a single sample is favorable for better strength. There is a presence of compatibility between the analytical and numerical results as the percentage difference for maximum load, radial tensile strength and maximum displacement are found as 1.8%, 2.4% and 1.5%, respectively, in a 3D cohesive model. A 2D cohesive model offers a fast solution and a competitive agreement with test results when the 2D and 3D finite element models are compared.

A novel double arrowhead auxetic coronary stent

A stent implantation is a standard medical procedure for treating coronary artery diseases. Over the years, various different designs have been explored for the stents which come with a range of limitations, including late in-stent restenosis (due to low radial strength), foreshortening, radial recoil, etc. Contrary, stents with auxetic design, characterized by a negative Poisson's ratio, display unique deformation characteristics that result in enhanced mechanical properties in terms of its radial strength, radial recoil, foreshortening, and more. In this study, we have analysed a novel double arrowhead (DA) auxetic stent that aims to overcome the limitations associated with traditional stents, specifically in terms of radial strength, foreshortening, and radial recoil. The parametric analysis was done initially on the DA's unit ring structure to optimize the design by evaluating the effect of three design parameters (angle, amplitude, and width) on the mechanical characteristics (radial strength and radial recoil) using finite element analysis. The width of the strut was found to be the primary determinant of the stent structure's properties. Consequently, the angle and width were found to have the least effect on altering the stent's mechanical properties. After performing the parametric analysis, optimal design factors were selected to design the full-length DA auxetic stent. The mechanical characteristics of the DA auxetic stent were assessed and compared in a case study with the Cypher™ commercial stent. The radial strength of DA auxetic stent was found to be 7.26 N/mm, which is more than double the Cypher™ commercial stent's radial strength. Additionally, the proposed stent possesses reduced radial recoil property and completely eliminates the stent foreshortening issue, which shows the superior mechanical properties of the proposed auxetic stent and its potential as a promising candidate for future stent designs.

Test methods for evaluation of balloon expandable vascular stents – measurement of radial strength and stiffness

Abstract The radial strength of balloon expandable stents represents a key property for a successful recanalization of sclerotic blood vessels. This study focuses on the most commonly used method for investigation of radial strength and radial stiffness via segmented head test setup. A custom made user software was used for evaluation of the radial force curves considering requirements of international standards such as ASTM F3067. Contributing factors during measurement such as friction and test setup deformation as well as the single cycle and multi cycle approach were addressed and discussed.

Engineering Analysis of Non-Braided Polycaprolactone Bioresorbable Flow Diverters for Aneurysms.

This paper reports a nonbraided, bioresorbable polycaprolactone (PCL) flow diverter (FD) for the endovascular treatment of aneurysms. Bioresorbable FDs can reduce the risk associated with the permanent metallic FDs as they are resorbed by the body after curing of aneurysms. PCL FDs were designed and fabricated using an in-house hybrid electromelt spinning-fused deposition fabrication unit. Flow diverter's properties, surface qualities, and mechanical characteristics of PCL FDs of 50%, 60%, and 70% porosities were studied using scanning electron microscope (SEM), atomic force microscopy (AFM), and high precision universal testing machine (UTM). The deployability through a clinically relevant catheter was demonstrated in a PDMS aneurysm model. The angiographic visibility of the developed PCL FDs was evaluated using BaSO4 and Bi2O3 coatings of various concentration. The average strut thicknesses were 74.12 ± 6.63 μm, 63.07 ± 1.26 μm, and 56.82 ± 2.09 μm for PCL FDs with 50%, 60%, and 70% porosities, respectively. They average pore areas for the 50%, 60% and 70% porosities FDs were 0.055 ± 0.0056 mm2, 0. 0605 ± 0.0065 mm2, and 0.0712 ± 0.012 mm2, respectively. The surface quality was great with an RMS roughness value of 14.45 nm. The tensile, radial strength, and flexibility were found to be satisfactory and comparable to the nonbraided coronary stents. The developed PCL FDs were highly flexible and demonstrated to be deployable through conventional delivery system as low as 4 Fr catheters in a PDMS aneurysm model. The visibility under X-ray increases with the increasing concentration of coating materials BaSO4 and Bi2O3. The visibility intensity was slightly higher with Bi2O3 coating of PCL FDs. The overall results of the engineering analysis of the developed nonbraided PCL FDs are promising.

Effects of Process Parameters on the Microstructure and Mechanical Properties of Large PE Pipe via Polymer Melt Jetting Stacking

The conventional methods for producing large-diameter pipes, such as extrusion and winding fusion welding, suffer from various drawbacks including difficulties in forming, complex molds, and high costs. Moreover, the flexibility and production efficiency of traditional manufacturing processes are relatively low. To address these challenges, this study proposes a new manufacturing process for polymer melt jetting and stacking based on fused deposition modeling (FDM) and rolling forming principles. This innovative approach aims to overcome the limitations of conventional methods and improve the flexibility and production efficiency in large-diameter pipe manufacturing. In the polymer melt jetting and stacking process, a plastic melt with a specific temperature and pressure is extruded by an extruder. The melt is then injected through the nozzle embedded in the previous layer of the pipe blank. By utilizing the localized rolling action of the forming device and adjusting the diameter using a diameter adjustment device, the newly injected plastic melt bonds with the previous layer of the pipe blank. Finally, the continuous large-diameter plastic pipe is formed through cooling and solidification. Experimental investigations demonstrate that the polymer melt jetting and stacking process can produce pipes with diameters ranging from 780 mm to 850 mm and thicknesses of 20 mm to 25 mm. The radial tensile strength, impact strength, and microstructural orientation of the produced pipes exhibit superior performance compared to those in the axial direction. Additionally, process parameters such as rolling speed, cooling temperature, melt extrusion speed, and tractive velocity significantly influence the microstructure and mechanical properties of the pipes.

Identification of Rotor Position of Permanent Magnet Spherical Motor Based on Compressed Sensing

The accurate identification of the rotor position of permanent magnet spherical motor (PMSM) is crucial to its closed-loop control. A novel method for rotor position identification of the PMSM based on compressive sensing is proposed, which can obtain accurate rotor position by a limited number of Hall sensors. Firstly, the paper designs a Hall sensor array based on the distribution characteristics of the rotor magnetic and the frequency domain characteristics of the air gap magnetic field, combined with the Fibonacci sequence. Then, an observation matrix construction method is proposed, used for compressed sensing of the radial magnetic field strength information in air gap. Finally, the position of the spherical rotor is identified according to the reconstructed information based on the sensor output value. The identification method is verified by experiments, which shows that the identification accuracy is about 1 degree.

Stent expansion in calcified coronary chronic total occlusions: The impact of different stent platforms.

To evaluate the stent expansion of the durable-polymer Zotarolimus-eluting stent (dp-ZES), the durable-polymer Everolimus-eluting stent (dp-EES), and the bioabsorbable-polymer Sirolimus-eluting stent (bp-SES) in calcified coronary chronic total occlusions (CTO). The newer generation stents with ultrathin struts might raise concerns regarding reduced radial strength and higher stent recoil (SR) when implanted in calcified CTOs. Between January 2017 and June 2021 consecutive patients with CTO undergoing percutaneous coronary intervention with dp-ZES, dp-EES, or bp-SES were evaluated. The analysis was performed in calcific and in noncalcific CTOs. Quantitative coronary angiography analysis was used to assess diameter stenosis (DS), absolute and relative SR, absolute and relative focal SR, absolute and relative balloon deficit (BD), and absolute and relative focal BD. The primary endpoint was DS. A total of 213 CTOs were evaluated, 115 calcific CTOs (dp-ZES:25, dp-EES:29, bp-SES:61) and 98 non-calcific CTOs (dp-ZES:41, dp-EES:11, bp-SES:46).In calcific CTOs, residual DS was lower in dp-ZES than in dp-EES and bp-SES (-1.00% [-6.50-6.50] vs. 13.00% [7.0-19.00] vs. 15.00% [5.00-20.00]; p < 0.001). Dp-ZES was also an independent predictor of residual DS ≤ 10% (OR 11.34, 95% CI 2.6-49.43, p = 0.001). Absolute and relative focal SR and absolute and relative SR were similar between dp-ZES, dp-EES, and bp-SES (p = 0.913, p = 0.890, p = 0.518, p = 0.426, respectively). In noncalcified CTOs, the residual DS was similar in the three groups (p = 0.340). High relative focal SR was less frequent in dp-ZES than in dp-EES and in bp-SES (19.5% vs. 54.5% vs. 37.0%; p < 0.048). The three stent platforms demonstrated an overall low residual DS when implanted in CTOs. However, dp-ZES was associated with the lowest residual DS and identified as independent predictor of residual DS ≤ 10% in patients with calcific CTOs. Dp-ZES was associated with a lower incidence of high relative focal stent recoil, in noncalcific CTOs. Balloon deficit might be considerate as a surrogate for stent expansion in calcified CTOs.

Mechanical Comparison between Fenestrated Endograft and Physician-Made Fenestrations.

A fenestrated endograft (FE) is the first-line endovascular option for juxta and pararenal abdominal aortic aneurysms. A physician-modified stent-graft (PMSG) and laser in situ fenestration (LISF) have emerged to circumvent manufacturing delays, anatomic standards, and the procedure's cost raised by FE. The objective was to compare different fenestrations from a mechanical point of view. In total, five Zenith Cook fenestrations (Cook Medical, Bloomington, IN, USA) and five Anaconda fenestrations (Terumo Company, Inchinnan, Scotland, UK) were included in this study. Laser ISF and PMSG were created on a Cook TX2 polyethylene terephthalate (PET) cover material (Cook Medical, Bloomington, IN, USA). In total, five LISFs and fifty-five PMSG were created. All fenestrations included reached an 8 mm diameter. Radial extension tests were then performed to identify differences in the mechanical behavior between the fenestration designs. The branch pull-out force was measured to test the stability of assembling with a calibrated 8 mm branch. Fatigue tests were performed on the devices to assess the long-term outcomes of the endograft with an oversized 9 mm branch. The results revealed that at over 2 mm of oversizing, the highest average radial strength was 33.4 ± 6.9 N for the Zenith Cook fenestration. The radial strength was higher with the custom-made fenestrations, including both Zenith Cook and Anaconda fenestrations (9.5 ± 4.7 N and 4.49 ± 0.28 N). The comparison between LISF and double loop PMSG highlighted a higher strength value compared with LISF (3.96 N ± 1.86 vs. 2.7 N ± 0.82; p= 0.018). The diameter of the fenestrations varied between 8 and 9 mm. As the pin caliber inserted in the fenestration was 9 mm, one could consider that all fenestrations underwent an "elastic recoil" after cycling. The largest elastic recoil was observed in the non-reinforced/OC fenestrations (40%). A 10% elastic recoil was observed with LISF. In terms of mechanical behavior, the custom-made fenestration produced the highest results in terms of radial and branch pull-out strength. Both PMSG and LISF could be improved with the standardization of the fenestration creation protocol.