Medical textile implants: hybrid fibrous constructions towards improved performances.

OBJECTIVES: One main challenge for textile implants is to limit the foreign body reaction (FBR) and in particular the fibrosis development once the device is implanted. Fibrotic tissue in-growth depends on the fiber size, the pore size, and the organization of the fibrous construction. Basically, non-woven fibrous assemblies present a more favorable interface to biological tissues than do woven structures. However, they are mechanically less strong. In order to combine both strength and appropriate topography properties, the design of a hybrid fibrous construct was considered and discussed in this work. METHODS: Two polyethylene terephthalate (PET) weaves (satin and plain) were assembled with a non-woven PET mat, using an ultrasound welding process. RESULTS: The physical and mechanical properties of the construction as well as its ability to interact with the biological environment were then evaluated. In particular, the wettability of the obtained substrate as well as its ability to interact with mesenchymal stem cells (MSC) at 24 h (adhesion) and 72 h (proliferation) in vitro were studied. CONCLUSIONS: The results show that the non-woven layer helps limiting cell proliferation in the plain weave construction and promotes conversely proliferation in the satin construction.

Editor's Choice -- Type IIIb Endoleaks: Fabric Perforations of Explanted New Generation Endoprostheses.

OBJECTIVE: To analyse explanted endografts (EGs) and describe fabric degradation responsible for type IIIb endoleaks. METHODS: As part of the European collaborative retrieval programme, 32 EGs with fabric defects on macroscopic evaluation were selected. The explanted EGs were processed and studied based on the ISO 9001 certified standard protocol. It includes instructions on the collection, transportation, cleaning, and examination of explanted material. The precise analysis was performed with a digital microscope of 20 - 200 times magnification. Possible perforation mechanisms were assessed in stress tests. RESULTS: The median time to explantation of the 32 EGs was 54 months. The explants included 65 separate EG modules, with 46 (70.8%) having a combined 388 fabric perforations. Each EG had a median of 4.79 mm2 (interquartile range [IQR] 9.86 mm2) of cumulated hole area (an average of 0.13% of an EG's area). There were 239 (61.6%) expanded polytetrafluoroethylene (ePTFE; 11 EGs) and 149 (38.4%) polyethylene terephthalate (PET; 21 EGs) fabric ruptures, with no difference in hole distribution between these types of material. Overall, 126 (32.5%) stent related and 262 (67.5%) non-stent related fabric perforations were identified. Perforations caused by fabric fatigue in ePTFE (151, 63.2%) and material kinking in PET (41, 27.5%) were the most common. The stent related perforations were larger in size (0.80 mm2) than non-stent related perforations (0.19 mm2); p < .001. Wider interstent spaces and prolonged implantation duration were associated with an increased risk of stent related perforation development; p < .001 and p = .004, respectively. Large stent related perforations were also detected in the short term, suggesting mechanical issues as underlying causes. CONCLUSION: The fabric of EGs may degrade and lead to the development of perforations. The largest perforations are stent related. Their occurrence and size depend on the implantation time and the EG shape affected by arterial tortuosity. The conclusions are limited to the samples from a select explant group.

Surface treatment of PET multifilament textile for biomedical applications: roughness modification and fibroblast viability assessment.

OBJECTIVES: The aim of this study was to investigate the potential of tuning the topography of textile surfaces for biomedical applications towards modified cell-substrate interactions. METHODS: For that purpose, a supercritical Nitrogen N2 jet was used to spray glass particles on multi-filament polyethylene terephthalate (PET) yarns and on woven fabrics. The influence of the jet projection parameters such as the jet pressure (P) and the standoff distance (SoD) on the roughness was investigated. RESULTS: The impact of the particles created local filament ruptures on the treated surfaces towards hairiness increase. The results show that the treatment increases the roughness by up to 17 % at P 300 bars and SoD 300 mm while the strength of the material is slightly decreased. The biological study brings out that proliferation can be slightly limited on a more hairy surface, and is increased when the surface is more flat. After 10 days of fibroblast culture, the cells covered the entire surface of the fabrics and had mainly grown unidirectionally, forming cell clusters oriented along the longitudinal axis of the textile yarns. Clusters were generated at yarn crossings. CONCLUSIONS: This approach revealed that the particle projection technology can help tuning the cell proliferation on a textile surface.

Mechanical Comparison between Fenestrated Endograft and Physician-Made Fenestrations.

INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Calcification of Synthetic Vascular Grafts: A Systematic Review.

Objective: Calcification of vascular grafts, including polyethylene terephthalate (PET) and expanded polytetrafluoroethylene (ePTFE) grafts may contribute to graft failure, but is under reported. The aim of this study was to review the literature to assess whether vascular graft calcification is deleterious to vascular graft outcomes. Data sources: The Medline and Embase databases were searched. Review methods: A systematic literature search according to PRISMA Guidelines was performed using a combined search strategy of MeSH terms. The MeSH terms used were "calcification, physiologic", "calcinosis", "vascular grafting", "blood vessel prosthesis", "polyethylene terephthalates", and "polytetrafluoroethylene". Results: The systematic search identified 17 cases of PET graft calcification and 73 cases of ePTFE graft calcification over a 35 year period. All cases of PET graft calcification were reported in grafts explanted for graft failure. The majority of cases of ePTFE graft calcification were unexpectedly noted in grafts used during cardiovascular procedures and subsequently removed. Conclusion: Calcification of synthetic vascular grafts is under reported but can compromise the long term performance of the grafts. More data, including specific analysis of radiological findings as well as explant analysis are needed to obtain a more sensitive and specific analysis of the prevalence and incidence of vascular graft calcification and the impact of calcification on synthetic graft outcomes.

Degradation phenomena on last generations of polyethylene terephthalate knitted vascular prostheses.

Objectives: The aim of this study was to analyze a series of new generations of explanted knitted polyethylene terephthalate (PET) vascular grafts (VGs) presenting nonanastomotic degradations according to preoperative computed tomography angiography (CTA) when available in order to better understand the mechanisms leading to rupture. Methods: Explanted knitted PET VGs were collected as part of the Geprovas European Collaborative Retrieval Program. VGs implanted after 1990 presenting a nonanastomotic rupture of the fabric were included. Clinical data and pre-explantation CTA data when available were retrieved for each VG. The ruptures were characterized by macroscopic examination and optical microscopy according to a standardized protocol. Results: Nineteen explants were collected across 11 European centers, 13 were implanted as infrainguinal bypasses, 3 at the aortic level, and 1 as an axillobifemoral bypass. The mean implantation duration was 9.2 years. Pre-explantation CTA data were available for 8 VGs and showed false aneurysms at the adductor canal level on 4 VGs, at the inguinal ligament level on 2 VGs, and in the proximal or middle third thigh level on 3 VGs. Examination revealed longitudinal ruptures on 9 explanted VGs (EVGs), transversal ruptures on 15 EVGs, 45°-oriented ruptures on 5 EVGs, V-shaped ruptures on 7 EVGs, and punctiform ruptures on 2 EVGs. Ruptures involved the remeshing line on 11 EVGs, the guideline on 10 EVGs, and the crimping valley on 15 EVGs.At the microscopic level, two main degradation phenomena could be identified: a decrease in the density of the meshing and local ruptures of the PET fibers. Fourteen EVGs presented a loosening of the remeshing line and 17 EVGs an attenuation of the crimping. Conclusions: New-generation PET VG degradation seems to result from both anatomic constraints and intrinsic textile structure phenomena.

Mechanical Performance Assessment of Physician Modified Aortic Stent Graft.

OBJECTIVE: This study aimed to compare various fenestration configurations of physician modified aortic stent grafts in order to identify which design parameters have a significant influence on the mechanical behaviour of the fenestration. METHODS: the fenestration configurations were considered according to different manufacturing parameters: cutting technique, fenestration reinforcement, suture material, reinforcement loop design, and number of suture points. The performance of the graft/bridging stent assembly was assessed at various levels: (1) branch pull out force; (2) fenestration enlargement and rupture strength; (3) balloon angioplasty resistance; and (4) behaviour under cyclic fatigue. RESULTS: Sixty manual fenestrations were created. The tests performed on the fenestrations had several main findings. First, reinforcement increased the radial force on the branch, which increased the pull out force; this may limit migration of the bridging stent in vivo. The phenomenon was amplified with a snare reinforced fenestration, which seemed to be the most efficient. Moreover, increasing the number of suture passes also appeared to increase the branch extraction force securing the assembly. The enlargement tests showed that non-reinforced fenestrations had the weakest radial strength. This was confirmed with the balloon angioplasty test, which showed that these latter specimens undergo the most significant textile degradation. After fatigue tests, all fenestrations were larger, showing that elastic recoil was incomplete in all samples. The largest recoil was observed in the non-reinforced ophthalmological cautery (OC) fenestrations (40%). Regarding the behaviour of the samples up to rupture, all samples behaved in a similar way; however, the double loop fenestration strength level was the highest. CONCLUSION: This study demonstrated that the snare double loop reinforcement has an advantage regarding durability of the graft branch assembly. Moreover, non-reinforced fenestrations show signs of weakness and lack of stability, which questions the in situ or laser fenestration procedures.

Quantifying the Functional Stiffness of Pullthrough Wires Used for Endovascular Aneurysm Repairs Using Comparative Tension Dynamometry.

Objective: There are only few studies on the stiffness of guidewires used to deliver devices during endovascular procedures, particularly abdominal/thoracic endovascular aneurysm repair. In certain situations, tensioned pullthrough wires are also used, but no studies have examined their effective/functional stiffness. The objective of this study was to assess the radial stiffness characteristics of pullthrough wires compared with standard stiff wires. Methods: Two types of stiff guidewires (Lunderquist Extra-Stiff and Amplatz Super Stiff; 0.035″ × 260 cm), were compared with a floppy guidewire (Radifocus Stiff M; 0.035″ × 260 cm) in two configurations: standard (non-tensioned) and pullthrough (tensioned). Radial stiffness was defined as the peak deformation force (PDF; newtons [N]) needed to deform the wires on an electromechanical dynamometer; data were logged on proprietary dynamometric software and peak load values assessed per wire. Three experimental runs were performed on three fresh sets of each wire per configuration. PDFs from straight configuration to midwire deformation at 15 mm were translated into Microsoft Excel for statistical analysis in Minitab 19 for Windows. Results: Mean ± SD PDFs were 7.83 ± 0.23 N for the Lunderquist and 9.87 ± 0.92 N for the Amplatz. This was 7.84 ± 0.52 N for the Radifocus wire in standard configuration, which increased to 15.48 ± 0.33 N when the Radifocus wire was in pullthrough configuration. This was significantly higher than both the Lunderquist and Amplatz Super Stiff wires (p < .001, one way analysis of variance). Conclusion: This study affirmed that a pullthrough wire becomes functionally more rigid than typical stiff wires used for endovascular procedures, and it is this stiffness that allows device delivery.

Validation and Verification of High-Fidelity Simulations of Thoracic Stent-Graft Implantation.

Thoracic Endovascular Aortic Repair (TEVAR) is the preferred treatment option for thoracic aortic pathologies and consists of inserting a self-expandable stent-graft into the pathological region to restore the lumen. Computational models play a significant role in procedural planning and must be reliable. For this reason, in this work, high-fidelity Finite Element (FE) simulations are developed to model thoracic stent-grafts. Experimental crimp/release tests are performed to calibrate stent-grafts material parameters. Stent pre-stress is included in the stent-graft model. A new methodology for replicating device insertion and deployment with explicit FE simulations is proposed. To validate this simulation, the stent-graft is experimentally released into a 3D rigid aortic phantom with physiological anatomy and inspected in a computed tomography (CT) scan at different time points during deployment with an ad-hoc set-up. A verification analysis of the adopted modeling features compared to the literature is performed. With the proposed methodology the error with respect to the CT is on average 0.92 ± 0.64%, while it is higher when literature models are adopted (on average 4.77 ± 1.83%). The presented FE tool is versatile and customizable for different commercial devices and applicable to patient-specific analyses.

Non-woven textiles for medical implants: mechanical performances improvement.

Non-woven textile has been largely used as medical implant material over the last decades, especially for scaffold manufacturing purpose. This material presents a large surface area-to-volume ratio, which promotes adequate interaction with biological tissues. However, its strength is limited due to the lack of cohesion between the fibers. The goal of the present work was to investigate if a non-woven substrate can be reinforced by embroidery stitching towards strength increase. Non-woven samples were produced from both melt-blowing and electro-spinning techniques, reinforced with a stitching yarn and tested regarding several performances: ultimate tensile strength, burst strength and strength loss after fatigue stress. Several stitching parameters were considered: distance between stitches, number of stitch lines (1, 2 or 3) and line geometry (horizontal H, vertical L, cross X). The performance values obtained after reinforcement were compared with values obtained for control samples. Results bring out that reinforcement can increase the strength by up to 50% for a melt-blown mat and by up to 100% for an electro-spun mat with an X reinforcement pattern. However, after cyclic loading, the reinforcement yarn tends to degrade the ES mat in particular. Moreover, increasing the number of stitches tends to fragilize the mats.

Vascular grafts collagen coating resorption and healing process in humans.

Background: The objective of the present study was to evaluate the bioresorption rate of collagen coating (CC) sealed on textile vascular grafts (VGs) and their healing in humans using histologic analysis of explanted VGs. Methods: A total of 27 polyester textile VGs had been removed during surgery from 2012 to 2020. The segments underwent histologic assessment. The CC bioresorption rate was assessed using morphometric analysis to determine the internal and external capsule thickness, inflammatory reaction degree, presence of neovessels, and endothelial cell layer. Results: A total of 27 VGs were explanted from 25 patients because of infection (n = 5; 18.5%), thrombosis (n = 7; 25.9%), stenosis (n = 2; 7.4%), rupture (n = 4; 14.8%), aneurysmal degeneration (n = 3; 11.1%), revascularization (n = 4; 14.8%), or another cause (n = 2; 7.4%), with a median implantation duration of 291 days (interquartile range [IQR], 48-911 days). VGs with remaining CC (n = 7; 26%) had been explanted earlier than had those without (n = 20; 74%; 1 day [IQR, 1-45 days] vs 516 days [IQR, 79-2018 days]; P = .001). After 1 year, no remaining CC was detected on the analyzed VG sections. VGs implanted for <90 days had had a greater CC maximal thickness (63.90 µm [IQR, 0-83.25 µm] vs 0 µm [IQR, 0-0 µm]; P = .006) and a greater CC surface coverage (180° [IQR, 0°-360°] vs 0° [IQR, 0°-0°]; P = .002) than those implanted for >90 days. VGs implanted for >90 days had a greater external capsule thickness (889.2 µm [IQR, 39.6-1317 µm] vs 0 µm [IQR, 0-0 µm]; P = .002), a higher number of inflammatory mononuclear cells and giant cells (168 cells [IQR, 110-310 cells] vs 0 cells [IQR, 0-94 cells]; P < .0001) and a higher number of neovessels (4 [IQR, 0-5] vs 0 [IQR, 0-0]; P = .001) than those implanted for <90 days. Conclusions: CC had a slow bioresorption rate in humans. Complete healing was never achieved, with no endothelial coverage observed. This finding implies that CC might not help graft healing.

Polyethylene terephthalate textile heart valve: How poly(ethylene glycol) grafting limits fibrosis.

Transcatheter aortic valve replacement (TAVR) is an alternative technique to surgical valve replacement for over 300,000 patients worldwide. The valve material used in the TAVR is made of biological tissues, whose durability remains unknown. The success of the TAVR favors the research toward synthetic valve leaflet materials as an alternative to biological tissues. In particular, polyethylene terephthalate (PET) textile valves have recently proven durability over a 6-month period in animal sheep models. Excessive fibrotic tissue formation remains, however, a critical issue to be addressed. The aim of this work was therefore to investigate the potential of PET textiles covalently conjugated with polyethylene glycol (PEG), known for its antifouling properties, to modulate the fibrosis formation both in vitro and in vivo. For this purpose, the surfaces of heart valves made of PET textiles were functionalized with an atmospheric pressure plasma, leading to the formation of carboxylic acid (COOH) groups, further used for PEG-NH2 conjugation. Surface modification efficiency was assessed by X-ray photoelectron spectroscopy and water contact angle measurements. The biological behavior of the as-modified surfaces was evaluated by in vitro assays, using rat cardiac fibroblast cells. The results show that PEG treated substrates restrained the fibroblasts adhesion and proliferation. The PEG treated valve, implanted in a juvenile sheep model, showed a significant fibrosis reduction. The explant also revealed calcification issues that need to be addressed.

Degradation Phenomena on "Homemade" Explanted Aortic Textile Endografts.

OBJECTIVE: In the 1990s, the concept of "homemade" endografts (EGs) using commercially available materials was proposed in clinical practice for endovascular abdominal aortic repair (EVAR). The aim of this study was to analyse the ageing phenomena of these EGs in light of explant analyses. METHODS: The study focused on five explanted homemade EGs collected from 2012 to 2014. The explants were assessed in accordance with the ISO 9001/13485 certified standard protocol, which included naked eye evaluation, organic remnant cleaning, and microscopic and endoscopic examinations and analysis (magnification range from 20% to 200%). The observations report followed a classification based on 12 features assessing the fabric cover, the stitch filament, and the stents. RESULTS: The reasons for explantation were type 1 endoleak in three cases and aneurysm sac growth in two. The implantation duration ranged from 56 to 202 months. Sixty three per cent of the fabric surface lesions (holes and tears) were related to abrasion between the fabric and the stents. Up to 33% of the knots used to connect adjacent stents were broken on one EG. Other defects including running suture rupture and stent corrosion were also observed. The overall hole cumulated surface ranged from 0.377 mm2 (56 month of implantation) up to 3.21 mm2 (78 month of implantation). CONCLUSION: In this study, various ageing phenomena on homemade textile EGs were identified and classified. The main damaging mechanisms were related to abrasion stress leading to tears and holes in the fabric, stitch ruptures, and detachment of stent segments responsible for serious EG deformations and further degradation.

Mechanical Behaviour of Fenestrations in Current Aortic Endografts.

OBJECTIVE: The aim of this study was to assess the mechanical characteristics of current commercially available fenestrated endografts (FE). The performance of the fenestrations according to the design were compared as the relationship between a bridging covered stent graft (CSG) and the fenestration. METHODS: A total of 21 Zenith (Cook Medical, Bloomington, IN, USA) and 17 Anaconda (Terumo Company, Inchinnan, UK) fenestrations were studied. Radial extension tests were performed, inserting two half cylinders spaced up to 2 mm in a 7 mm diameter fenestration from each device. Branch pull out force was measured to test the stability of the assembly with a calibrated 8 mm branch and two CSGs: Advanta V12 (Atrium Medical; Hudson, NH, USA) and BeGraft Peripheral Stent Graft (Bentley InnoMed GmbH, Hechingen, Germany). A branch was inserted in both the 7 mm diameter fenestrations and in a control 7 mm fenestration. Fatigue tests were performed on the devices to assess long term outcomes of the endograft. RESULTS: Over a 2 mm vertical displacement, the resulting loading curves look similar for both devices. The force value level was 33.4 ± 6.9 N for the Cook fenestration and 54.45 ± 18 N for the Anaconda fenestration (p = .001). With respect to an 8 mm calibrated branch, the required extraction strength from the fenestration was statistically significantly greater with the Anaconda device (9.5 ± 4.7 N vs. 4.49 ± 0.28 N; p = .001). The required strength to extract the V12 CSG from a control cylindered shape was statistically significantly higher than for the BeGraft CSG (6.75 ± 2.86 N vs. 1.83 ± 0.67 N; p = .003). The surface area of the fenestration of the Cook device was increased with cycling (7 200 cycles) compared with the Anaconda device (15.5% vs. 6.5% hole surface area increase). CONCLUSION: The mechanical performance of the fenestration can be fine tuned by considering its design. A CSG optimising the performance of the fenestration and the CGS-fenestration interface could reduce the risk of leakage in clinical practice.

Are All Wires Created the Same? A Quality Assurance Study of the Stiffness of Wires Typically Employed During Endovascular Surgery Using Tension Dynamometry.

OBJECTIVE: There have only been a few studies on the stiffness and load bearing characteristics of guidewires used to deliver devices during endovascular procedures, particularly endovascular aneurysm repair. The aim of this study was to compare the load bearing characteristics of typical stiff and floppy wires, including in the context of consistency for each wire type. METHODS: Two sets of stiff guidewires (Lunderquist Extra-Stiff and Amplatz Super Stiff [0.035" × 260 cm]), were compared with a floppy hydrophilic guidewire (Radifocus Stiff M [0.035" × 260 cm]). Radial stiffness was defined as the force (newtons [N]) needed to deform the wires on an electromechanical dynamometer. Tests were repeated with three runs on three sets of the same wire to check for consistency. Data were logged on proprietary dynamometric software and peak load values assessed per wire. Peak deformation forces (PDFs) from straight configuration to midwire deformation at 15 mm was translated into Microsoft Excel for statistical analysis in Minitab 19 for Windows. RESULTS: There was good agreement within each wire set, with no difference in PDFs from runs for each wire (p > .10). Mean ± standard deviation PDFs were 7.83 ± 0.23 N for the Lunderquist, 9.87 ± 0.92 N for the Amplatz, and 7.84 ± 0.52 N for the Radifocus wires. The Amplatz wire exhibited the greatest resistance to deformation vs. both the Lunderquist and Radifocus wires (p < .001, one way analysis of variance). Both Amplatz and Radifocus wires had non-linear deformation characteristics. CONCLUSION: This study confirmed that the represented hydrophilic wire is more deformable than the stiff wires. The Amplatz wire has complex construction features that yielded surprising baseline stiffness characteristics. The linear stiffness characteristics of the Lunderquist wire possibly contribute to it being the preferred choice for large endograft delivery.

Estimating the "Pull" on a Pullthrough Wire: A Pilot Study.

OBJECTIVE: Pullthrough/body floss wires are used to track endovascular devices across tortuous aorto-iliac anatomy encountered during endovascular repair of abdominal or thoracic aortic aneurysms. The tension imparted on such wires is arbitrary and has never been quantified. This pilot study attempted to quantify the tension used to stiffen the floppy hydrophilic wires typically used in such a scenario. METHODS: Two linked experiments were undertaken, the first by tasking 13 blinded vascular surgeons (eight male, five female; mean age 36 ± 11 years, including nine trainees) with pulling a long floppy hydrophilic wire (Radifocus Guidewire M Stiff, Terumo UK, Bagshot, Surrey, UK) attached at the other end to a horizontally configured industrial scale (HDN-N Hanging Scale, Kern & Sohn GmbH, Balingen, Germany), to simulate what they individually felt was an "appropriate" tension; the second by using the derived average tensioning force to set up a pullthrough wire within a rigid life like aorto-iliac model to assess whether a test device (16F Sentrant Introducer Sheath, Medtronic Limited, Watford, UK) could be delivered over such a tensioned wire in both brachiofemoral and femorofemoral configurations. RESULTS: The mean tension exerted by the group on the wire was 38.3 ± 14.8 N (equivalent to 3.9 kgf). Pullthrough wire tensioning was undertaken by fixing one end and applying a 3.9 kg weight at the other. The test device was successfully deployed into the infrarenal aortic position and also across the aortic bifurcation, via brachiofemoral and femorofemoral pullthrough configurations, respectively. CONCLUSION: Successful test device deliveries suggest that a minimum tension equivalent to almost 4 kgf applied to a floppy wire can provide "stiffeningË® to allow device tracking across tortuous aorto-iliac anatomy. More studies are needed to ascertain whether lower tensions can be applied; these results may help provide a platform for other such studies depending on configuration, aortic geometry, and device or wire/tension characteristics.

Fibrous biomaterials: Effect of textile topography on foreign body reaction.

Foreign Body Reaction (FBR) is a critical issue to be addressed when polyethylene terephthalate (PET) textile implants are considered in the medical field to treat pathologies involving hernia repair, revascularization strategies in arterial disease, and aneurysm or heart valve replacement. The natural porosity of textile materials tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. The purpose of this study is to assess the influence of the textile topography of various woven substrates on the wetting properties of these substrates and on their in vitro interaction with mesenchymal stem cells (MSC) at 24 and 72 hr. The tests were performed both at yarn and fabric level under forced wetting and ingrowth conditions in order to replicate the mechanisms going on in vivo under blood pressure. Results demonstrate that cell proliferation is influenced by the textile wetting properties, which can be tuned at yarn and fabric level. In particular, it is shown that a satin weave obtained from porous spun yarn limits cell proliferation due to the high porosity of the yarn and the limited saturation index of the weave. Yarn and fabric saturation seems to play a predominant role in cell proliferation on textile substrates.

Comprehensive Review of Physician Modified Aortic Stent Grafts: Technical and Clinical Outcomes.

OBJECTIVE: Physician modified stent grafts (PMSGs) present satisfactory results in selected cases of complex aortic pathologies. However, the technique lacks standardisation and depends on the surgeon and aortic segment. The aim of this article is to review comprehensively the technical details and clinical results of PMSGs related to patients with pathology in all aortic locations. METHODS: A MEDLINE search (last search 20 April 2020) identified 20 relevant papers in the English language published over the last 20 years evaluating clinical outcomes after a PMSG and specifying the technical details to design it. RESULTS: Seven hundred and eleven patients were included in the analyses, with 59% being operated on as an emergency. Ninety-two per cent of abdominal aortic segment PMSGs (A-PMSGs) were performed either as an emergency or before 2012. The main indications were available in 670 cases; 435 were degenerative aneurysms (64.9%) and 171 were aortic dissections (25.5%). Most of the endografts used were composed of polyethylene terephthalate, except for the Ankura (expanded polytetrafluoroethylene [Lifetech Scientific, Shenzhen, China]; n = 50, 7.5%). The Valiant (Medtronic, Minneapolis, MN, USA) represented 65% (n = 169) of aortic arch PMSGs (aa-PMSGs) and the Zenith platform (Cook Medical, Bloomington, IN, USA) 51% (n = 139) of A-PMSGs. A snare was used to reinforce the fenestration in 458 PMSGs (66%) and a cautery device cut the fenestration in 484 (75%) PMSGs. No bridging stent was used in 47 (7.0%) PMSGs (these aa-PMSGs had large fenestrations). Technical success ranged from 87.5% to 100% and 30 day mortality from 0% to 8%. Primary branch patency ranged from 96.3% to 100% at 12 month follow up. Zero to 14% of patients experienced type 3 or type 1 endoleak at 14.8 month follow up. CONCLUSION: PMSG is a useful technique, particularly when validated treatments are not available. However, it is a non-standardised technique and the long term consequences of modifications remain unknown.

Finite Element Simulations of the ID Venous System to Treat Venous Compression Disorders: From Model Validation to Realistic Implant Prediction.

The ID Venous System is an innovative device proposed by ID NEST MEDICAL to treat venous compression disorders that involve bifurcations, such as the May-Thurner syndrome. The system consists of two components, ID Cav and ID Branch, combined through a specific connection that prevents the migration acting locally on the pathological region, thereby preserving the surrounding healthy tissues. Preliminary trials are required to ensure the safety and efficacy of the device, including numerical simulations. In-silico models are intended to corroborate experimental data, providing additional local information not acquirable by other means. The present work outlines the finite element model implementation and illustrates a sequential validation process, involving seven tests of increasing complexity to assess the impact of each numerical uncertainty separately. Following the standard ASME V&V40, the computational results were compared with experimental data in terms of force-displacement curves and deformed configurations, testing the model reliability for the intended context of use (differences < 10%). The deployment in a realistic geometry confirmed the feasibility of the implant procedure, without risk of rupture or plasticity of the components, highlighting the potential of the present technology.

How yarn orientation limits fibrotic tissue ingrowth in a woven polyester heart valve scaffold: a case report.

Transcatheter Aortic Valve Implantation (TAVI) has become today a popular alternative technique to surgical valve replacement for critical patients. However, with only six years follow up on average, little is known about the long-term durability of transcatheter implanted biological tissue. Moreover, the high cost of tissue harvesting and chemical treatment procedures favor the development of alternative synthetic valve leaflet materials. In that context, thin, strong and flexible woven fibrous constructions could be considered as interesting candidates. However, the interaction of textile material with living tissue should be comparable to biological tissue, and the Foreign Body Reaction (FBR) in particular should be controlled. Actually, the porosity of textile materials tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. The purpose of this preliminary animal case study is to investigate the influence of the valve leaflet yarn orientation on the fibrotic tissue ingrowth. For that purpose the in vivo performances of 45° inclined yarn woven valve leaflets implanted in juvenile sheep model were assessed after three months implantation. Results bring out that in the frame of this case study the development of fibrosis is limited with a woven fabric valve obtained from 45° inclined yarns.