A Unique Case of an Expanded Polytetrafluoroethylene Graft Rupture 14 Years after Abdominal Aortic Aneurysm Open Repair Managed with Placement of a Thoracic Endograft

We report a unique case of expanded polytetrafluoroethylene (ePTFE) tube graft rupture that occurred 14 years after abdominal aortic aneurysm (AAA) repair. Endovascular repair with a thoracic endograft was performed. Postoperatively, an increase in the size of the existing hematoma with active extravasation occurred and was managed with iliolumbar artery embolization. Τo the best of our knowledge, rupture of ePTFE graft used for AAA repair has not been reported in the literature.

Finite element analysis of the impact of the properties of dental wedge materials on functional features

Purpose: Defect of the interproximal wall of the tooth is filled with use the shaped matrix and wedge which seals bottom margin during filling. Better fit of the wedge and equalization of the pressure forces on the matrix is achieved by the compliance of the wedge structure through cuts and perforations and the use of silicone materials and unidirectionally expanded polytetrafluoroethylene (ePTFE). The work presents a methodology for model studies of the mechanics of dental wedges in order to evaluate and compare the impact of wedge materials on functional features. The hypothesis of the work was that the mechanical properties of ePTFE determine the effectiveness of the dental wedge. Design/methodology/approach: Effect of modulus of elasticity and friction coefficient of wedge and matrix materials on the functional features of the wedge was studied on the way Finite Element Analysis (FEA). Simulation included contact sliding between wedge and matrix what was simulated in nonlinear large displacements regime. The sealing evaluation criterion was the pressure distribution between the wedge and matrix below the lower edge of the defect. Displacement values were the criterion for the loss of convexity as a result of matrix deformation. Findings: The material for the wedge should be characterized by a low coefficient of friction, low elasticity (ensuring high compliance of the wedge) and at the same time the ability to large permanent deformations, which allows for plastic shaping of the matrix from the side of the defect in order to achieve the required wall convexity and the tangent point. Research limitations/implications: Results show tendency of phenomena in limitation to model simplification of the interdental gap and the ideal adhesion of the matrix to the tooth and linear elasticity of materials. Practical implications: The material that best meets the requirements is unidirectionally expanded polytetrafluoroethylene, which has one of the lowest coefficients of friction and very high plasticity necessary to shape the matrix from the inside of the cavity. Originality/value: Methodology of model study and criteria of functional characteristics of dental wedge was presented.

Impact of chronic kidney disease on the outcomes of infrapopliteal venous, and heparin-bonded expanded polytetrafluoroethylene bypass surgeries: A retrospective cohort study

The aim of this study was to analyze the results of infrapopliteal venous and prosthetic bypass surgeries for patients with chronic limb-threatening ischemia (CLTI) and moderate to severe chronic kidney disease (CKD). All consecutive patients undergoing infrapopliteal bypass surgeries at two academic vascular centers between March 2002 and November 2018 were included in this retrospective study. During this timeframe, infrapopliteal grafts were performed for 487 patients. Of these patients, 160 (32.9%; group 1) had normal renal function, 248 (50.9%; group 2) had moderate CKD, and 79 (16.2%; group 3) had severe CKD according to the Kidney Disease Improving Global Outcomes guidelines. After 5 years’ follow-up, the primary patency rate was 46.0% and the secondary patency rate was 54.9% without statistical significance noted between the CKD groups. Limb salvage (65.3%, p = 0.024) and long-term survival (19.6%, p < 0.001) were considerably lower in patients with severe CKD. In subgroup analysis, vein grafts had significantly better long-term patency rates compared to prosthetic grafts, regardless of CKD group. However, in patients with severe CKD, patency rates of vein and heparin-bonded expanded polytetrafluoroethylene (HePTFE) grafts were comparable at the 1-year mark. Our study shows that autologous vein grafts remain the first choice for infrapopliteal bypass surgeries in patients with CKD. HePTFE grafts showed good short-term results in patients with severe CKD. Given the short life expectancy of these high-risk patients, prosthetic HePTFE grafts may be reasonable in this population if a suitable vein is absent.

A Radiation-Crosslinked Gelatin Hydrogel That Promotes Tissue Incorporation of an Expanded Polytetrafluoroethylene Vascular Graft in Rats

A prosthetic vascular graft that induces perigraft tissue incorporation may effectively prevent serious sequelae such as seroma formation and infection. Radiation-crosslinked gelatin hydrogel (RXgel) mimics the chemical and physical properties of the in vivo extracellular matrix and may facilitate wound healing by promoting tissue organization. Fibroblasts cultured on RXgel actively migrated into the gel for up to 7 days. RXgels of three different degrees of hardness (Rx[10], soft; Rx[15], middle; Rx[20], hard) were prepared, and small disc-like samples of RXgels were implanted into rats. In vitro and in vivo results indicated that Rx[10] was too soft to coat vascular grafts. Thus, expanded polytetrafluoroethylene (ePTFE) vascular grafts coated with RXgel were developed using Rx[15] and Rx[20] gels, and ring-shaped slices of the graft were implanted into rats. Alpha-smooth muscle actin (SMA) and type III collagen (Col-III) levels were detected by immunohistochemistry. Immunohistochemical staining for SMA and Col-III demonstrated that RXgel-coated vascular grafts induced more granulation tissue than non-coated grafts on days 14 and 28 after implantation. RXgel-coated ePTFE vascular grafts may provide a solution for patients by reducing poor perigraft tissue incorporation.

Clinical, Radiographic, and Histomorphometric Evaluation of a Vertical Ridge Augmentation Procedure Using a Titanium-Reinforced Microporous Expanded Polytetrafluoroethylene Emrane: A Prospective Case Series with 1-Year Follow-Up

Vertical ridge augmentation for long-term implant stability is difficult in severely resorbed areas. We examined the clinical, radiological, and histological outcomes of guided-bone regeneration using novel titanium-reinforced microporous expanded polytetrafluoroethylene (MP-ePTFE) membranes. Eighteen patients who underwent implant placement using a staged approach were enrolled (period: 2018–2019). Vertical ridge augmentation was performed in areas with vertical bone defects ≥ 4 mm. Twenty-six implant fixtures were placed in 14 patients. At implant placement six fixtures had relatively low stability. On cone-beam computed tomography, the average vertical changes were 4.2 ± 1.9 (buccal), 5.9 ± 2.7 (central), and 4.4 ± 2.8 mm (lingual) at six months after vertical ridge augmentation. Histomorphometric analyses revealed that the average proportions of new bone, residual bone substitute material, and soft tissue were 34.91 ± 11.61%, 7.16 ± 2.74%, and 57.93 ± 11.09%, respectively. Stable marginal bone levels were observed at 1-year post-loading. The residual bone graft material area was significantly lower in the exposed group (p = 0.003). There was no significant difference in the vertical height change in the buccal side between immediately after the augmentation procedure and the implant placement reentry time (p = 0.371). However, all implants functioned well regardless of the exposure during the observation period. Thus, vertical ridge augmentation around implants using titanium-reinforced MP-ePTFE membranes can be successful.

Omniflow II biosynthetic grafts versus expanded polytetrafluoroethylene grafts for infrainguinal bypass surgery. A single-center retrospective analysis

Introduction: The aim of this study is to evaluate the outcome of Omniflow II biosynthetic vascular grafts as compared to synthetic expanded polytetrafluoroethylene (ePTFE) grafts in infrainguinal bypass surgery. Methods: A single-center, retrospective, observational study was performed reviewing patients with critical limb ischemia who underwent infrainguinal bypass surgery between 2014 and 2018. Patients characteristics, graft characteristics, and treatment outcomes were collected. Patency rates were compared using Kaplan–Meier estimates. Results: Sixty bypasses were performed in 57 patients. For above-knee surgery, six were Omniflow and 13 were synthetic. For below-knee surgery, 19 were Omniflow and 22 were synthetic. Patient characteristics between groups were similar. However, American Society of Anesthesiologists (ASA) classification scores were higher in the Omniflow group as compared to ePTFE (88% was ASA 3 or higher versus 60%; p = 0.018). Furthermore, wound, ischemia, and foot infection (WIfI) composite scores were higher in the Omniflow group ( p = 0.0001). There was a trend toward more active infection at time of surgery in the Omniflow group (40 vs 22.9%, p = 0.15). At 1 year, primary patency rates were 60.0% versus 46.9% for above-knee Omniflow versus ePTFE grafts, respectively ( p = 0.72). Secondary patency rates were 80.0% versus 82.5% ( p = 0.89), and limb salvage rates were 83.3% versus 100% ( p = 0.14). For below-knee surgery, 1- and 2-year primary patency rates in Omniflow versus ePTFE grafts were 36.0% versus 41.8% ( p = 0.60) and 36.0% versus 31.1% ( p = 0.87). Secondary patency rates were 66.8% versus 75.2% at 1 year ( p = 0.53) and 58.8% versus 48.3% ( p = 0.77) at 2 years. Below-knee limb salvage rates for Omniflow versus ePTFE after 2 years were 88.0% versus 68.3% ( p = 0.28), respectively. Aneurysmal degeneration occurred in 2/25 (8%) in the Omniflow group and 0/35 (0%) in the ePTFE group. Bypass infections occurred in 2/25 (8%) in the Omniflow group and 0/35 (0%) in the ePTFE group ( p = 0.09). Conclusion: Omniflow bypasses were more commonly implanted in patients with higher limb infection rate as confirmed with a higher adapted WIfI score. A trend toward a higher infection rate of Omniflow grafts was observed but not statistically significant. Graft infection rates were relatively low and treatable with antibiotics. No significant difference in graft performance was observed. The choice between the two studied grafts remains based on surgeon’s preference.