Synthetic Tube Research Articles

Neurosurgical Microvascular Anastomosis: Systematic Review of the Existing Simulators and Proposal of a New Training Classification System.

The literature lacks a combined analysis of neurosurgical microvascular anastomosis training models. We performed a systematic literature search to provide an overview of the existing models and proposed a classification system based on the level of simulation and reproducibility of the microvascular anastomosis. The systematic literature search followed the PRISMA guidelines. We consulted MEDLINE, Web of Knowledge, and EMBASE independently for papers about bypass training models. Every training model was analyzed according to six tasks supposed to esteem their fidelity to the real operative setting by using a scoring system from zero to two. Finally, authors classified the models into five classes, from A to E, by summing the individual scores. This study included 109 papers for analysis. Training models were grouped into synthetic tubes, ex vivo models (animal vessels, fresh human cadavers, human placentas) and in vivo simulators (live animals-rats, rabbits, pigs). By applying the proposed classification system, live animals and placentas obtained the highest scores, falling into class A (excellent simulators). Human cadavers and animal vessels (ex vivo) were categorized in class B (good simulators), followed by synthetic tubes (class C, reasonable simulators). The proposed classification system helps the neurosurgeon to analyze the available training models for microvascular anastomosis critically, and to choose the most appropriate one according to the skills they need to improve.

Techniques for abductor reattachment in proximal femoral replacement for non-oncological reconstructions: a narrative review.

Proximal femoral replacement due to revision hip arthroplasty or catastrophic proximal femur fracture fixation failures with considerable proximal femur bone loss can lead to a substantial loss of function of the soft tissue around the hip and the abductor muscles in particular. Surgical techniques of gluteus medius repair and/or abductor mechanism reattachment/reconstruction are widely debated in the literature, but it is quite rarely dealt with in the context of megaprosthesis and femoral reconstruction, particularly in non-oncologic patients. The aim of this study is to present a narrative review of the literature on techniques for abductor reattachment in proximal femoral replacement for non-oncological reconstructions. MEDLINE, Embase, and Cochrane databases were searched by two researchers independently from inception until February 1st, 2023 (923 for MEDLINE and 963 for Embase; Cochrane is a composite of multiple databases and thus does not report a standard inception date). Articles examining proximal femoral reconstruction with megaprosthesis or allograft prosthesis were included. Studies concerning cadaver and oncologic patients were excluded. If the researchers failed to find an agreement on whether to include a study, the senior researcher would make a final decision in such cases. Data were extracted and stored, and qualitative synthesis was performed. A total of 1,157 articles from MEDLINE, 11,187 articles from Embase, and 0 articles from Cochrane were identified. Of 12,344 articles, the structured screening process revealed 10 eligible trials. Four different types of abductor musculature reconstruction/reinsertion were identified. Multiple and complex revision hip arthroplasties as well as multiple surgical procedures for proximal femur fracture fixations failures may have a great impact on proximal femur bone stock condition and soft tissue preservation requiring the use of a proximal femur megaprosthesis. In such cases, the abductor mechanism reconstruction and/or reattachment is achievable with different techniques that can be resumed in four different groups: direct suture to the prosthesis, trochanteric sleeve osteotomy, muscle-to-muscle suture, and synthetic tube augmentation suture.

A method of assessing peripheral stent abrasiveness under cyclic deformations experienced during limb movement

Poor outcomes of peripheral arterial disease stenting are often attributed to the inability of stents to accommodate the complex biomechanics of the flexed lower limb. Abrasion damage caused by rubbing of the stent against the artery wall during limb movement plays a significant role in reconstruction failure but has not been characterized. Our goals were to develop a method of assessing the abrasiveness of peripheral nitinol stents and apply it to several commercial devices. Misago, AbsolutePro, Innova, Zilver, SmartControl, SmartFlex, and Supera stents were deployed inside electrospun nanofibrillar tubes with femoropopliteal artery-mimicking mechanical properties and subjected to cyclic axial compression (25%), bending (90°), and torsion (26°/cm) equivalent to five life-years of severe limb flexions. Abrasion was assessed using an abrasion damage score (ADS, range 1–7) for each deformation mode. Misago produced the least abrasion and no stent fractures (ADS 3). Innova caused small abrasion under compression and torsion but large damage under bending (ADS 7). Supera performed well under bending and compression but caused damage under torsion (ADS 8). AbsolutePro produced significant abrasion under bending and compression but less damage under torsion (ADS 12). Zilver fractured under all three deformations and severely abraded the tube under bending and compression (ADS 15). SmartControl and SmartFlex fractured under all three deformations and produced significant abrasion due to strut penetration (ADS 20 and 21). ADS strongly correlated with clinical 12-month primary patency and target lesion revascularization rates, and the described method of assessing peripheral stent abrasiveness can guide device selection and development. Statement of significancePoor outcomes of peripheral arterial disease stenting are related to the inability of stents to accommodate the complex biomechanics of the flexed lower limb. Abrasion damage caused by rubbing of the stent against the artery wall during limb movement plays a significant role in reconstruction failure but has not been characterized. Our study presents the first attempt at assessing peripheral stent abrasiveness, and the proposed method is applied to compare the abrasion damage caused by Misago, AbsolutePro, Innova, Zilver, SmartControl, SmartFlex, and Supera peripheral stents using artery-mimicking synthetic tubes and cyclic deformations equivalent to five life-years of severe limb flexions. The abrasion damage caused by stents strongly correlates with their clinical 12-month primary patency and target lesion revascularization rates, and the described methodology can be used as a cost-effective and controlled way of assessing stent performance, which can guide device selection and development.

Beyond Classic Anastomoses Training Models: Overview of Aneurysm Creation in Rodent Vessel Model.

Nowadays, due to the decline in the number of microsurgical clippings for cerebral aneurysms and revascularization procedures, young neurosurgeons have fewer opportunities to participate and train on this type of surgery. Vascular neurosurgery is a demanding subspecialty that requires skills that can only be acquired with technical experience. This background pushes the new generations to be ready for such challenging cases by training hard on different available models, such as synthetic tubes, chicken wings, or placenta vessels. Although many training models for vascular neurosurgery have been described worldwide, one of the best is the rodent vessels model. It offers pulsation, coagulation, and real blood flow conditions in a physiologic atmosphere that mimics perfectly the intracranial human vessels environment, especially in terms of size. However, the current differences in governmental different regulations about the use of living animals in medical experimentation and the social awareness, as well as the lack of financial support, cause more difficulties for neurosurgeons to start with that kind of training. In this review, we describe the tools and techniques as basic steps for vascular microsurgery training by using rodent models, that provide an accurate copy of brain vessels environment under stable conditions. The initial three classical known microanastomoses for neurosurgeons are end-to-end, end-to-side, and side-to-side, but in literature, there have been described other more complex exercises for training and investigation, such as aneurysm models. Although there is still little data available, we aim to summarize and discuss aneurysm's training models and reviewed the current literature on the subject and its applications, including a detailed description of the techniques.

Tubular shape aware data generation for segmentation in medical imaging.

Chest X-ray is one of the most widespread examinations of the human body. In interventional radiology, its use is frequently associated with the need to visualize various tube-like objects, such as puncture needles, guiding sheaths, wires, and catheters. Detection and precise localization of these tube-like objects in the X-ray images are, therefore, of utmost value, catalyzing the development of accurate target-specific segmentation algorithms. Similar to the other medical imaging tasks, the manual pixel-wise annotation of the tubes is a resource-consuming process. In this work, we aim to alleviate the lack of annotated images by using artificial data. Specifically, we present an approach for synthetic generation of the tube-shaped objects, with a generative adversarial network being regularized with a prior-shape constraint. Namely, our model uses Frangi-based regularization to draw synthetic tubes in the predefined fake mask regions and, then, uses the adversarial component to preserve the global realistic appearance of the synthesized image. Our method eliminates the need for the paired image-mask data and requires only a weakly labeled dataset, with fine-tuning on a small paired sample (10-20 images) proving sufficient to reach the accuracy of the fully supervised models. We report the applicability of the approach for the task of segmenting tubes and catheters in the X-ray images, whereas the results should also hold for the other acquisition modalities and image computing applications that contain tubular objects.

Casing Wear Log Using a Prewear Ellipse Shape from Ultrasonic Logging Data

Summary The inspection of casing integrity is an important field of study regarding well safety assessment. In casing design, casing wear prediction is usually performed with a torque and drag model calibrated with laboratory simulation results. The availability of ultrasonic logging data makes it possible to calibrate these models, correlating actual conditions with similar equipment, operations, and trajectory. This work presents an accurate methodology that quantifies casing wear under a certain uncertainty level using data from ultrasonic logging tools. An ellipse equation is adopted to estimate the prewear condition of the cross section, and then it is applied to calculate wear. Also, a methodology to generate synthetic tube cross sections with prescribed ovality, eccentricity, and groove wear, with any intensities and locations, is presented. A model error analysis is carried out to compare the accuracy of the proposed strategy with others found in the literature. A statistical error analysis shows how the measurement noise is related to the estimated wear. This provides the level of uncertainty of the response, which can improve the right interpretation of data. Results demonstrate that the strategy successfully achieves an adequate quantification and can be applied to estimate casing wear profiles, under an admissible uncertainty tolerance.

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles

A Novel Silicone Simulation Model for Microvascular Anastomosis.

Purpose:Surgical simulation of microvascular anastomosis has become increasingly popular. There are several living and silicone models available. Current silicone models fail to accurately reproduce a vessel’s loose adventitial layer, which may lead to the development of improper microsurgical technique. Our purpose is to create a realistic 3-dimensional microsurgical simulator that incorporates an adventitial vessel layer for higher fidelity manipulation of vessels.Methods:A microvascular anastomosis simulator was manufactured using metal moulds and inorganic materials. Synthetic tubing was created with a metal cylinder, 1.65 mm in diameter, painted with 2 sequential layers of silicon with a shore hardness of 2A. Silicone was allowed to fully cure in-between layers. Vessel adventitia was created with a 100-micron polyester mesh adhered to the silicone vessel exterior. Once dry, the synthetic tube is removed from the metal cylinder is then clipped to reveal the inner lumen. Both Resident and attending physicians evaluated the model with and without the adventitial layer and completed a questionnaire.Results:Grasping and manipulation of the vessel were scored on Average score 4.5 and 3 out of 5, with adventitia and without, respectively (P = .00906). Usefulness as a teaching tool was scored on average 4.9 and 4.2, with adventitia and without, respectively (P = .0232). The analysis included: simulation realism, educational utility, and overall satisfaction. Responses in all domains were favourable, suggesting the utility of this model.Conclusion:We created a realistic, high fidelity microvascular anastomosis simulator that is low cost and easily reproducible. Initial feedback is encouraging regarding realism, educational utility, and overall usefulness. Further validation is required to assess its effectiveness in resident education and skill transfer to the operating room.

Neutrophil Activation and Neutrophil Extracellular Trap Formation in Dialysis Patients

Rationale & ObjectiveThe removal of metabolic waste by passing blood through synthetic tubing and membranes generates an immune response, even with the most biocompatible materials available. We evaluated blood levels of neutrophil activation and cell death during dialysis to devise a set of markers by which future dialysis interventions might be measured for biocompatibility.Study DesignObservational, case control.Setting & Participants30 patients with end-stage kidney disease in Seattle, WA, evaluated during 30 dialysis procedures in out- and inpatient settings were compared with 27 healthy (negative) controls and 20 nondialysis patients with systemic lupus erythematosus as positive controls.Predictor(s)Blood levels of neutrophil activation (calprotectin and peroxidase activity) and cell death (cell-free DNA and neutrophil extracellular traps) were assayed.Outcome(s)Markers of neutrophil activation and cell death can be used to assess immune response during dialysis.Analytical ApproachDescriptive analysis and group comparisons.ResultsIntradialytic levels of neutrophil activation markers are higher than prehemodialysis levels (P < 0.05), demonstrating neutrophil activation during hemodialysis. Less neutrophil activation occurs with peritoneal dialysis (P < 0.05). Immunosuppressive treatment and anticoagulant therapy did not seem to affect the capacity of neutrophils to undergo activation with hemodialysis. Finally, levels of hemodialysis-induced neutrophil activation correlated with markers of endothelial activation (r = 0.44; P = 0.01).LimitationsLow sample size with heterogeneous patient cohort.ConclusionsNeutrophil activation occurs during hemodialysis, potentially contributing to endothelial inflammation and damage. Neutrophil activation markers are novel and sensitive measures of biocompatibility for improving dialysis.

Grapefruit Training Model for Distal Anterior Cerebral Artery Side-to-Side Bypass

Simulation models enable trainees to master microsurgical skills before performing surgeries. Vascular bypass is a critical component of cerebrovascular and many nonneurologic procedures. However, most available bypass training models lack important spatial, tactile, and physiologic aspects of real surgery. Animal and placental models provide true physiology but are expensive. While some models adequately simulate superficial temporal artery-middle cerebral artery bypass, there is no model for side-to-side distal anterior cerebral artery bypass. The objective is to create a realistic and inexpensive training model for this important procedure. The depth of interhemispheric fissures in cadaver brains was compared with the grapefruit radii. Grapefruits were dissected to simulate the operative field within the deep and narrow interhemispheric fissure. Pericallosal arteries were mimicked with chicken wing vessels or synthetic tubing, with an aquarium pump providing closed circulation. Twelve board-certified neurosurgeons who were given bypass training using the grapefruit model were blindly surveyed on model realism and training suitability. Grapefruit depths from pith to central column were comparable with interhemispheric cadaveric fissure depths. Approximate preparation time of grapefruit training models was 5-10 minutes. Surveyed neurosurgeons rated the model a better replicate for cerebral artery bypass (P<0.02) and more challenging than common training models (P < 0.01). They also rated the grapefruit model as likely to be superior for improving surgical skills before surgery (P < 0.05). This grapefruit model provides a realistic simulation of side-to-side distal anterior cerebral artery bypass procedure that can be inexpensively and easily implemented in nearly any resource environment.

Synthesis and characterization of kaolinite nanotubes (KNTs) as a novel carrier for 5-fluorouracil of high encapsulation properties and controlled release

Kaolinite nanotubes (KNTs) were synthesized successfully from raw well crystalline kaolinite and characterized using different analytical techniques. The synthetic tubes appear as multi-walled scrolls with length ranges from 50 nm to 600 nm with an average pore diameter of 12 nm and specific surface area of 105m2/g. The outer diameter range of kaolinite tubes from 10 nm to 50 nm, and the inner diameter range from about 2 to about 20 nm. The synthetic kaolinite nanotubes were used as Nano-carriers for 5-fluorouracil (5FU) with encapsulation capacity reach about 103 mg/g which was confirmed by HRTEM, FT-IR and XRD analysis for the samples after the loading process. The synthetic KNTs loaded by 5FU (KNTs/5FU) is of controlled release properties that continued to about 60 h at releasing percentage of about 74.3% and 91% using intestinal fluid and colonic fluid, respectively. The cell viability studies utilizing L929 cells line resulted in very high cell viability percentage and non-cytotoxicity induced the application of KNTs as a promising carrier for 5FU of effective anticancer properties.

Band Gap Closing in a Synthetic Hall Tube of Neutral Fermions.

We report the experimental realization of a synthetic three-leg Hall tube with ultracold fermionic atoms in a one-dimensional optical lattice. The legs of the synthetic tube are composed of three hyperfine spin states of the atoms, and the cyclic interleg links are generated by two-photon Raman transitions between the spin states, resulting in a uniform gauge flux ϕ penetrating each side plaquette of the tube. Using quench dynamics, we investigate the band structure of the Hall tube system for a commensurate flux ϕ=2π/3. Momentum-resolved analysis of the quench dynamics reveals a critical point of band gap closing as one of the interleg coupling strengths is varied, which is consistent with a topological phase transition predicted for the Hall tube system.

Echinoderm-Inspired Tube Feet for Robust Robot Locomotion and Adhesion

Movement in echinoderms is facilitated by the coordinated activity of thousands of individually addressable and reversibly adhesive tube feet. To investigate the potential applicability of these unique biological actuators as a locomotory structure for robotics applications, we describe here the design, fabrication, and evaluation of an elastomeric structural analogue. The synthetic tube feet were modeled as bistable deformable domes, containing an embedded magnet to facilitate the reversible attachment to ferromagnetic materials. Two unique robots were developed using the bistability of these domes - CircleBot, which is capable of rolling on ferrous surfaces using a pull and roll technique, and PlanarBot, which uses a programmed deflection direction in the domes to move in a plane.

Progress of nerve bridges in the treatment of peripheral nerve disruptions

Progress of nerve bridges in the treatment of peripheral nerve disruptions Qiang Ao Department of Tissue Engineering, School of Fundamental Science, China Medical University, Shenyang, Liaoning, Peoples’ Republic of China Abstract: Clinical repair of a nerve defect is one of the most challenging surgical problems. Autologous nerve grafting remains the gold standard treatment in addressing peripheral nerve injuries that cannot be bridged by direct epineural suturing. However, the autologous nerve graft is not readily available, and the process of harvesting autologous nerve graft results in several complications. Thus, it is necessary to explore an alternative to autologous nerve graft. In the last few decades, with significant advances in the life sciences and biotechnology, a lot of artificial nerve grafts have been developed to aim at the treatment of peripheral nerve disruptions. Artificial nerve grafts range from biological tubes to synthetic tubes and from nondegradable tubes to degradable tubes. Among them, acellular nerve allografts and artificial nerve repair conduits are two kinds of the most promising substitutes for nerve autografts. The history, research status, and prospect of acellular nerve allografts and artificial nerve repair conduits are described briefly in this review. Keywords: peripheral nerve injury, repair, acellular nerve graft, nerve conduit

Repairing peripheral nerve injury using tissue engineering techniques.

Each year approximately 360,000 people in the United States suffer a peripheral nerve injury (PNI), which is a leading source of lifelong disability (Kelsey et al., 1997; Noble et al., 1998). The most frequent cause of PNIs is motor vehicle accidents, while gunshot wounds, stabbings, and birth trauma are also common factors. Patients suffering from disabilities as a result of their PNIs are also burdensome to the healthcare system, with average hospital stays of 28 days each year (Kelsey et al., 1997; Noble et al., 1998).

Past, Present, and Future of Nerve Conduits in the Treatment of Peripheral Nerve Injury.

With significant advances in the research and application of nerve conduits, they have been used to repair peripheral nerve injury for several decades. Nerve conduits range from biological tubes to synthetic tubes, and from nondegradable tubes to biodegradable tubes. Researchers have explored hollow tubes, tubes filled with scaffolds containing neurotrophic factors, and those seeded with Schwann cells or stem cells. The therapeutic effect of nerve conduits is improving with increasing choice of conduit material, new construction of conduits, and the inclusion of neurotrophic factors and support cells in the conduits. Improvements in functional outcomes are expected when these are optimized for use in clinical practice.

Advanced water treatment using a meshed synthetic tube as biological filter media in pilot plant scale

ABSTRACT The purpose of this study is to remove suspended solids (SS) and soluble organic matter from waste water using meshed synthetic tubes, made of synthetic poly propylene fiber to allow free water flow from any direction. The capacity of 450 m3/d pilot plant was operated to treat effluent of secondary settling tank in sewage treatment plant. Removals of SS, soluble organic matter and phosphorus (w/additional chemical treatment), were monitored. As a result, maximum SS-loading rate for the plant was found 3.8 kg SS/m3 d, and operation time was limited up to 45 h, and the maximum linear velocity was found 16 m3/m2 h. The maximum SS removal for each unit reactor was 7.1 kg/cage m3. With the meshed tube biofilter, not only SS but also soluble organic matter removal and nitrification were observed. Because of its relatively fast filtration rate and high filtration capacity, it seemed to be used properly as a direct filtration.

Observation of a mouse sperm motility in a natural uterine tube-inspired microfluidic channel

Bio-inspired engineering has been promisingly spotlighted recently due to the replication of unique natural environments and processes. Fertilization occurs when sperm meets an egg, typically within the uterine tube. Using bio-inspired engineering, we developed natural uterine mimicry for studying sperm motility via the synthetic microfluidic tube system. Mature sperm were collected from the testicular cauda epididymis, and subsequently remained stable for up to 2 days. The primary sperm cells were infused into a single 1.5 cm wrinkle wave patterned microfluidic channel, moving in a prototypical forward sine wave pattern. This study may be useful in understanding the natural behavior of sperm and also may be applied to fertility treatments in the future.

Prostate carcinoma cell growth-inhibiting hydrogel supports axonal regeneration in vitro

Prostate cancer is the most common malignant tumor in men. Radical prostatectomy, the most common surgical therapy, is typically accompanied by erectile dysfunction and incontinence due to severing of the axons of the plexus prostaticus. To date, no reconstructive therapy is available as the delicate network of severed nerve fibers preclude the transplantation of autologous nerves or synthetic tube implants. Here, we present an injectable hydrogel as a regenerative matrix that polymerizes in situ and thus, adapts to any given tissue topography. The two-component hydrogel was synthesized from a hydrolyzed collagen fraction and stabilized by enzymatic crosslinking with transglutaminase. Physical analysis employing osmolarity measurements and cryosectioning revealed an isotonic, microstructured network that polymerized within 2min and displayed pronounced adhesion to abdominal tissue. Cell culturing demonstrated the biocompatibility of the gel and a general permissiveness for various neuronal and non-neuronal cell types. No effect on cell adhesion, survival and proliferation of cells was observed. A chemotherapeutic drug was integrated into the hydrogel to reduce the risk of fibrosis and tumor relapse. Significantly, when the hydrogel was employed as a drug release depot in vitro, aversive fibroblast- and prostate carcinoma cell growth was inhibited, while axonal outgrowth from peripheral nervous system explants remained completely unaffected. Taken together, these results suggest that the gel's adequate viscoelastic properties and porous microstructure, combined with its tissue adhesion and neuritotrophic characteristics in the presence of a cell type-specific cytostatic, may constitute an appropriate hydrogel implant applicable to patients suffering from prostatectomy associated side effects.

Aortic valve sparing operations in aortic root aneurysms: remodeling or reimplantation?

Over the past two decades, there has been a significant paradigm shift towards aortic valve sparing (AVS) operations over the more traditional method of prosthetic replacement for suitable aortic pathologies. Such operations, by virtue of preserving the patient’s native aortic valvular anatomy, carry numerous benefits, most notably the obviation of life-long anticoagulation medication and the reduced need for reoperation when compared to mechanical and biosynthetic valves. Two main valve-sparing operations have dominated modern surgical practice: the David ‘reimplantation’ technique, whereby the entire aortic valve is preserved and securely sewn within a synthetic tube graft (1), and the Yacoub ‘remodeling’ technique, which replaces all three sinuses by means of a triple-tongue-shaped graft (2). Whether one technique is superior than the other has polarised the surgical community. The present article summarises the recent evidence comparing remodelling and reimplantation techniques (3).