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.

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.

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.

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.

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.

Disruption of a Covered Nitinol Self Expanding Stent Graft Implanted in the Common Femoral Artery.

INTRODUCTION: Common femoral artery aneurysm is a rare condition and can be treated by open or endovascular surgery. There is a general understanding that open surgery is the recommended option because of the anatomical location and the biomechanical constraints posed by hip flexion. REPORT: The case of a 66 year old man treated with an endograft for an asymptomatic abdominal aortic aneurysm followed by the implantation of a nitinol covered stent graft (Fluency™, Bard Peripheral Vascular, Temple, AZ) for a 25 mm diameter left common femoral artery aneurysm is reported. Two years later, follow up revealed a rupture of the nitinol covered stent graft, requiring an open iliofemoral reconstruction. DISCUSSION: Systematic analysis with protocolised cleaning, and macroscopic and microscopic evaluation (Keyence VHX-600 digital microscope) of the explanted nitinol covered stent graft showed membrane perforation at the level of an acute angle formed by the struts.

Heart valves from polymeric fibers: potential and limits.

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 biological tissue harvesting and chemical treatment procedures favor the development of alternative synthetic valve leaflet materials. In that context, thin, flexible and porous textile constructions could be considered as interesting candidates. However, these constructions must be strong enough to withstand the load applied on the leaflet especially in aortic position. Moreover, the interaction of textile material with living tissue should be comparable to biological valve tissue, and the foreign body reaction (FBR) as well as the calcification mechanisms should be controlled. In the frame of heart valve tissue engineering strategies, the use of bioresorbable polymer scaffolds is expected to limit that FBR. However, to precisely control the degradation of the polymer is not trivial. Conversely, when permanent textile polymers are considered, the porosity of the fibrous scaffold tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. In that context, the ideal synthetic fibrous valve leaflet remains to be found. The purpose of this study was to investigate the possible strategies which have been adopted over the last 50 years regarding the use of textile as heart valve leaflet material. Results showed that textile presented potential, despite remaining strong challenges. It came out that hybrid textiles combining bioresorbable and permanent polymer fibers arranged in both non-woven and woven or knitted way could probably help providing strength and generating appropriate tissue ingrowth.

Current status on aortic endografts.

Endovascular treatment has become widespread to treat aneurysmal disease, especially located in the aorta. The modern era of abdominal aortic aneurysm repair started between 1986 and 1991, and in the last 30 years, Endovascular Treatment for abdominal aortic aneurysms evolved both due to the development of new materials and devices and the increasing appeal and effectiveness of the endovascular therapy itself. Vascular surgeons are using nowadays different solutions of Endovascular Treatment to treat all the expressions of aortic pathology (aneurysms, dissections and trauma) both in the acute and elective setting. Despite its use in every location of the aorta (the ascending aorta, the aortic arch, the thoracic aorta, thoraco-abdominal aorta, pararenal, iuxtarenal and infrarenal aortic aneurysms and iliac aneurysms), its safety and efficiency, endovascular treatment for aortic aneurysms presents some drawbacks: despite a lower short-term morbi-mortality, reinterventions and long-term patency are higher compared to open repair. In this review, we detail the most used types of endografts according to location, their performances and durability for each device. We conclude by discussing options to overcome ET limitations. Therefore, an obvious question arises: what we need in the future? What can the technological progress gives to physicians to further improve this new way of treating aorta?

Current status on vascular substitutes.

In the last decades, the main evolution in the field of vascular surgery was correlated to the development and introduction of vascular substitutes. Currently, two types of synthetic vascular substitutes have been widely adopted: polyethylene terephthalate and expanded polytetrafluoroethylene. Ideally, they should demonstrate a behavior as close as possible as that of human arteries in terms of mechanical and biological properties. However, no vascular substitute has been found to compare with the patency rates of gold-standard autologous conduits, and major drawbacks of current vascular substitutes remain both thrombogenicity and infectability.

Compliance of Textile Vascular Prostheses Is a Fleeting Reality.

OBJECTIVE: Compliance is considered to be a major property influencing the long term performances of synthetic vascular substitutes that could play a role in anastomotic false aneurysm and intimal hyperplasia stenosis onset. Over the last decades, manufacturers have tried to develop substitutes that mechanically mimic arterial properties and avoid a compliance mismatch at the anastomoses in particular. However, data are missing about how initial compliance properties could change with time. The goal of this study was to evaluate how the compliance of vascular grafts evolves under cyclic loading conditions in vitro. METHODS: The compliance of three different models of commercially available textile polyethylene terephthalate (PET) grafts was evaluated. Tests were performed with and without their original coating. Compliance was assessed with a specific device dedicated to measure the deformations undergone by a graft under cyclic pressure loading conditions, using image analysis software. In each experiment, image analysis was performed under 60 and 140 mmHg pressure loading conditions at loading start (H0) and after three, six, and 24 h (H3, H6, H24) loading time. Average radial, longitudinal, and volumetric compliance was calculated from the obtained images. RESULTS: Twenty-four samples were tested. Results demonstrate that all values decreased significantly within only a few hours. On average, the loss of compliance after 3 h of cyclic loading ranged on average from 35% for longitudinal compliance to 39% for radial compliance and 37% (p < .050) for volume compliance. After 24 h, the loss of radial, longitudinal and volume compliance was respectively 63 ± 3%, 60.5 ± 2% and 61 ± 7%. CONCLUSION: In this in vitro model, PET graft compliance has already decreased significantly within 3 h. The rapid loss of compliance identified in this experimental study helps explain the mismatch mentioned in clinical observations.

Laser Uses in Noncoronary Arterial Disease.

BACKGROUND: In the past decade, excimer laser angioplasty (ELA) has emerged in the field of peripheral artery disease (PAD). Laser indications now extend to off-label uses, such as in situ fenestration of aortic endograft. The aim of this study was to review the different therapeutics applications of lasers in arterial disease treatment. METHODS: We reviewed the English-language literature using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. We selected 106 relevant papers. We excluded unrelated papers (n = 67), letters and commentaries (n = 6), and review articles (n = 7), leaving 26 articles to form the basis of this review. RESULTS: A total of 18 articles were included in the analysis of ELA applications in PAD. Nine articles were related to atherosclerotic plaques. With a mean follow-up of 15 ± 7 months, primary patency was 65% ± 20%. The mean distal embolism rate during the procedure was 5%. Eight more articles focused on in-stent restenosis. The mean technical success was 98%, and the rate of distal embolism during the procedure was 9%. With a mean follow-up of 10 ± 4 months, primary patency was 68% ± 18%. Eight articles described "off-label" excimer laser indications in endovascular therapy, including 5 papers regarding in situ fenestrations for complex aortic aneurysms. CONCLUSION: Laser atherectomy and laser-assisted techniques are an important part of a vascular surgeon and interventionalist's armamentarium.

Fibrous composite material for textile heart valve design: in vitro assessment.

With over 150,000 implantations performed over the world, transcatheter aortic valve replacement (TAVR) has become a surgical technique, which largely competes with open surgery valve replacement for an increasing number of patients. The success of the procedure favors the research toward synthetic valve leaflet materials as an alternative to biological tissues, whose durability remains unknown. In particular, fibrous constructions have recently proven to be durable in vivo over a 6-month period of time in animal sheep models. Exaggerated fibrotic tissue formation remains, however, a critical issue to be addressed. This work investigates the design of a composite fibrous construction combining a woven polyethylene terephthalate (PET) layer and a non-woven PET mat, which are expected to provide, respectively, strength and appropriate topography toward limited fibrotic tissue ingrowth. For this purpose, a specific equipment has been developed to produce non-woven PET mats made from fibers with small diameter. These mats were assembled with woven PET substrates using various assembling techniques in order to obtain hybrid fibrous constructions. The physical and mechanical properties of the obtained materials were assessed and valve samples were manufactured to be tested in vitro for hydrodynamic performances. The results show that the composite fibrous construction is characterized by properties suitable for the valve leaflet function, but the durability of the assembling is however limited under accelerated cyclic loading.

Explanted Vascular and Endovascular Graft Analysis: Where Do We Stand and What Should We Do?

OBJECTIVE/BACKGROUND: Since the late 1950s, major advances in vascular surgical practice have been closely associated with the introduction of novel vascular implants. These devices have been constructed from a variety of materials and have been designed to be implanted in several different ways. Despite a rigorous regulatory process, regular failures continue to be observed. A systematic review of the literature and of the Geprovas registry was performed in order to improve understanding of the failures. METHODS: A systematic review was performed via a search of the MEDLINE and Embase databases. Full text, English, German, or French language studies without any chronological limit were included. The reference lists of included studies, as well as the first 20 related items, were scanned for other potentially relevant studies. RESULTS: Data extraction allowed the evaluation of 184 publications; 72 publications met the inclusion criteria. Only 12 publications reported sufficient data for structural, histopathological, and epidemiological analysis. However, explant analysis allowed the understanding of degenerative phenomena: "warp knitted" replaced "weft knitted" polyethylene terephthalate grafts, decreasing the risk of dilatation or rupture; inter-nodal distance was modified in order to improve polytetrafluoroethylene graft incorporation capacities; and index of saturation, endograft fabric/stent interactions, and stent fatigue phenomena have been extensively studied in an attempt to improve endovascular device durability. CONCLUSION: A general lack of depth of reporting of explants remains. Dedicated systematic explant analysis programs are the key to improving the performance of future generations of devices.

How Compression Inside a Delivery System can Degrade the Cover of Aortic Endografts.

BACKGROUND: The goal of the present study was to identify the potential degradations undergone by textile endoprostheses (EPs) over the crimping process related to the catheter insertion purpose. In particular, we studied how the device design parameters can influence the wrinkling of the textile material, assuming that wrinkling induces stress concentration and may jeopardize the lifetime of the device. MATERIALS AND METHODS: Custom-designed EPs were obtained from various stent designs and textile constructions. Monofilament and multifilament materials were considered for the cover. Stent segment size, distance, and wire diameter were considered as variable for the stent. The EPs of 26-mm diameter were then crimped in a mock transparent 6-mm diameter catheter sheath for 8 and 30 days duration. After releasing the EPs from the sheath, the textile cover was characterized for roughness properties to identify the crease level induced on the surface by crimping. RESULTS: Results brought out that the monofilament material was characterized by a larger number of deeper creases in the zones where the stent was in contact with the cover. Conversely, the multifilament was more folded in the zones between stent segments. Moreover, it appeared that the stent design influenced the creases' topography. The textile seemed to be less prone to heavy wrinkling with stent segments made from larger wire diameter and larger segment size. Regarding the crimping duration, it came out that a longer stay in the sheath tends to promote more significant wrinkling. CONCLUSIONS: In this work, it was shown that wrinkling of the textile cover occurs in the EPs already at crimping level. However, an appropriate design of the EPs should limit the phenomenon and improve the performances of the EPs.

Learning Curve of Robotic-Assisted Anastomosis: Shorter than the Laparoscopic Technique? An Educational Study.

BACKGROUND: Achieving aortic anastomosis in laparoscopic surgery remains a technical challenge. The Da Vinci robot could theoretically counteract this issue by minimizing the technical challenge. The aim of this study was to compare the learning curves of performing vascular anastomoses by trainees without any experience using purely laparoscopic versus robotic-assisted techniques. METHODS: Surgery residents were randomly included in the laparoscopic group (group A, n = 3) and the robotic group (group B, n = 3). They performed 10 end-to-end anastomoses on 18-mm-diameter tubular expanded polytetrafluoroethylene grafts. The parameters recorded were duration to complete the anastomosis and an indirect sealing quality evaluation (ISQE) defined as the following ratio: number of stitches with a distance of less than 4 mm/total number of stitches. RESULTS: The mean duration to perform the anastomosis decreased from 2340 s (±64) for the first anastomosis to 651 s (±248) for the last in group A (P < 0.05) and from 1989 s (±556) to 801 s (±120) in group B (P < 0.05). The mean ISQE increased from 74% (±18) for the first anastomosis to 98% (±3) for the last in group A (P < 0.05) and decreased from 100% to 98% (±2) in group B (nonsignificant). The mean duration to perform the first anastomosis was lower in group B than in group A (P < 0.05). The mean duration to perform the last anastomosis was not significantly different between the groups. Sealing tended to be better in group B for the first anastomosis compared with group A. CONCLUSIONS: Minimally invasive laparoscopic technique training demonstrates a learning curve to perform vascular anastomoses. The robotic-assisted technique tended to improve suturing skills and should be considered as a valuable tool to reduce the technical learning curve.