Nickel-titanium Alloy Stent Research Articles

Selective Tumor Inhibition Effect of Drug-Free Layered Double Hydroxide-Based Films via Responding to Acidic Microenvironment.

Nickel-titanium alloy stents are widely used in the interventional treatment of various malignant tumors, and it is important to develop nickel-titanium alloy stents with selective cancer-inhibiting and antibacterial functions to avoid malignant obstruction caused by tumor invasion and bacterial colonization. In this work, an acid-responsive layered double hydroxide (LDH) film was constructed on the surface of a nickel-titanium alloy by hydrothermal treatment. The release of nickel ions from the film in the acidic tumor microenvironment induces an intracellular oxidative stress response that leads to cell death. In addition, the specific surface area of LDH nanosheets could be further regulated by heat treatment to modulate the release of nickel ions in the acidic microenvironment, allowing the antitumor effect to be further enhanced. This acid-responsive LDH film also shows a good antibacterial effect against S. aureus and E. coli. Besides, the LDH film prepared without the introduction of additional elements maintains low toxicity to normal cells in a normal physiological environment. This work offers some guidance for the design of a practical nickel-titanium alloy stent for the interventional treatment of tumors.

Microfabricated Nitinol Stent Retrievers with a Micro-Patterned Surface.

Stent retrievers are medical devices that are designed to physically remove blood clots from within the blood vessels of the brain. This paper focuses on microfabricated nitinol (nickel-titanium alloy) stent retrievers, which feature micro-patterns on their surface to enhance the effectiveness of mechanical thrombectomy. A thick film of nitinol, which was 20 µm in thickness, was sputtered onto a substrate with a micro-patterned surface, using electroplated copper as the sacrificial layer. The nitinol film was released from the substrate and then thermally treated while folded into a cylindrical shape. In vitro experiments with pig blood clots demonstrated that the micro-patterns on the surface improved the efficacy of blood clot retrieval.

Impact of Two Urethral Stent Types on Complications after One-Stage Hypospadias Repair Using the Duckett Procedure.

The authors evaluated whether the new nickel-titanium alloy stent (NTAS) is superior to the traditional silicone stent used in hypospadias repair surgery in preventing complications such as urinary fistula. This retrospective cohort study included 576 patients with hypospadias who underwent NTAS or traditional silicone stent placement after hypospadias surgery between March of 2002 and August of 2019. The primary outcome was the rate of urinary fistula occurrence at 4 weeks (stent removal time), and the secondary outcomes were the rate of other complications, such as urethral stricture, urethral diverticulum, infection, and so on. The occurrence of complications in both groups was compared, and the important contributing factors of urinary fistula and urethral stricture were determined. Among 576 patients, 398 were assigned to the NTAS group, and 178 were assigned to the silicone group. Thirty-five patients in the NTAS group and 30 in the silicone group developed urinary fistula, with a rate of 8.8% and 16.9%, respectively ( P = 0.005). Subgroup analysis showed that the differences were mainly in preschool patients (6 years or younger) ( P = 0.004) and those with the penile type of hypospadias ( P = 0.008). In addition, urethral stricture complicated five patients in the NTAS group and two in the silicone group, with a rate of 1.3% and 1.1%, respectively ( P = 1.000). Logistic regression showed that hypospadias type ( P = 0.001) and stent type ( P = 0.001) are the important risk factors for urethral fistula. The NTAS reduced the occurrence of urinary fistula complications after hypospadias repair in preschool patients, and can be presented as a better choice for hypospadias surgery. Therapeutic, III.

In vitro degradation and biocompatibility evaluation of typical biodegradable metals (Mg/Zn/Fe) for the application of tracheobronchial stenosis

Tracheobronchial obstruction in children due to benign stenosis or tracheobronchomalacia still remains a challenging matter of concern. Currently, there is 10%–20% complication rate in clinical treatment. The non-biodegradable property of silicone stents and nickel-titanium memory alloy stents take the primary responsibility for drawbacks including stimulating local granulation tissue proliferation, displacement, and stent-related infections. Permanent tracheobronchial stent will be a persistent foreign object for a long time, causing excessive secretion of tracheal mucosa, ulceration and even perforation, which is particularly unsuitable for young children with persistent tracheal growth. In this study, the degradation and biocompatibility performance of three typical biodegradable metals were investigated as potential tracheobronchial stent materials. The results exhibited that these materials showed different degradation behaviors in the simulating respiratory fluid environment compared with SBF. Except for pure iron group, high purity magnesium and zinc showed favorable cell adhesion and proliferation in three culture methodologies (direct culture, indirect culture and extraction culture). The proper corrosion rate and good biocompatibility indicated that high purity magnesium and zinc may be good candidates as tracheobronchial stent materials.

Magnetic resonance imaging of patients with airway stents.

Airway stent implantation is a highly effective treatment for airway stenosis. However, it is presently unclear whether patients with airway stents can safely undergo magnetic resonance imaging (MRI). Such stents may be metallic or non-metallic, and MRI may induce stent dislodgment or heating and may be associated with stent-induced artifacts. We thoroughly reviewed the literature, experimental data, and manufacturer information on non-metallic, stainless steel (SS) and nickel-titanium alloy stents. Non-metallic stents are made of non-ferromagnetic materials associated with no MRI concerns. SS stents may shift in a magnetic field, generating significant artifacts. Nickel-titanium alloy stents are not at risk of dislodgement or heating, but may create some artifacts affecting image quality. Both non-metallic and nickel-titanium alloy stents are safe for patients who must undergo MRI. However, the safety of SS stents depends on the type of steel used.

<i>In vitro</i> pharmacokinetics of sirolimus-coated stent for tracheal stenosis

Purpose: To investigate the in vitro pharmacokinetics of sirolimus-coated stent for tracheal stenosis Methods: Naked nickel titanium alloy stent was placed in methylene chloride leaching solution with different ratios of sirolimus/poly(lactic-co-glycolic acid) (PLGA). The morphology, thickness, and pellicles on the surface of the stent were observed by scanning electronic microscopy. Drug release from the stent was determined by enzyme amplification immunoassay. Results: Sirolimus was smoothly and uniformly attached to the stent, with an optimal sirolimus: PLGA coating ratio of 1:10. Further increases in sirolimus: PLGA ratio did not improve stent drug loading. A slow release of sirolimus from the stent was observed in the first week, followed by a rapid release and then much slower release process. Release of sirolimus persisted in the stent throughout the period of 42 days. Conclusion: The sirolimus-coated stent has a good surface morphology, and sustained and effective drug release characteristics. Thus, it may be effective and safe for use in the treatment of tracheal stenosis in vivo . Keywords: Tracheal stenosis, Sirolimus, Drug-coated stents, poly(lactic-co glycolic acid) PLGA

Supera self-expanding stents for endovascular treatment of femoropopliteal disease: a review of the clinical evidence.

Femoropopliteal lesions account for a significant proportion of endovascular interventions for peripheral artery disease in patients with disabling claudication or chronic limb ischemia. The femoropopliteal artery crosses two joint structures (hip and knee joints) and courses through the muscular adductor canal in the thigh, which places the artery at increased biomechanical stress. There is a critical need for stent platforms with a reduced risk of stent fracture while maintaining patency during long-term follow-up. The Supera peripheral stent system has a braided nickel–titanium alloy stent designed to withstand the unique stressors along the course of the femoropopliteal artery. This design may be associated with improved patency in association with reduced stent fracture rates on short- and medium-term follow-up. Further studies, including randomized controlled studies, comparing the Supera interwoven nickel–titanium alloy stent system with other stent platforms and angioplasty alone are needed.

In reference to Late complications of nickel‐titanium alloy stent in tracheal stenosis

The LaryngoscopeVolume 123, Issue 2 p. 549-549 Letter to the Editor In reference to Late complications of nickel-titanium alloy stent in tracheal stenosis Glenn W. Knox MD, JD, FACS, Glenn W. Knox MD, JD, FACS University of Florida/Shands Jacksonville Mandarin Hearing and Balance Center Jacksonville, FloridaSearch for more papers by this author Glenn W. Knox MD, JD, FACS, Glenn W. Knox MD, JD, FACS University of Florida/Shands Jacksonville Mandarin Hearing and Balance Center Jacksonville, FloridaSearch for more papers by this author First published: 30 January 2013 https://doi.org/10.1002/lary.23587Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume123, Issue2February 2013Pages 549-549 RelatedInformation

Development of Nitinol Stents: Etching Experiments

The present study focus on the chemical etching of shape memory nickel-titanium (nitinol) alloy stents made by laser cutting. Application of nitinol stents widely spread in case of atherosclerosis of peripheral vessels. This type of stent has to have appropriate surface quality, flexibility and strength. The aim of chemical etching is removing the burr, which arises during the laser cutting. Etching is one step of the production of stents. The appropriate parameters allow the laser burned surface and most of protruding material removing without significant damage of stent shape. During these experiments etching time was changed. After etching the cross section area was determined by metallographic examinations. The results of the examinations show the relationship between the etching time and the cross-section area. The analysis of measurement data revealed the change of etching velocity. Before and after etching the samples was examined by scanning electron microscopy (SEM). The different surfaces also were compared and the findings were discussed.

Visualization of stent lumen in MR imaging: relationship with stent design and RF direction.

Magnetic resonance imaging (MRI) visualization of metallic stent lumens is possible if the stent structure counteracts eddy currents in the lumen induced by the radio frequency magnetic field, B(1). To examine the effectiveness of various stent designs in counteracting eddy currents, we anchored eight copper stent models and 2 commercially available nickel-titanium alloy (Nitinol) stents in a gel phantom, perpendicular or parallel to the direction of B(1). A mesh stent lumen showed hypointensity irrespective of its alignment relative to B(1). A solenoid stent lumen showed hypointensity with the stent axis parallel to B(1), but it had the same signal intensity as outside the lumen when perpendicular to B(1). A Moebius stent lumen showed no signal reduction, irrespective of alignment relative to B(1). Lumens of the commercially available stents showed hypointensity regardless of alignment relative to B(1). Computer simulation revealed that the signal intensities of the stents corresponded to magnetic flux densities of B(1) in the stents, which are modified by the structure of the stent. While in vivo MRI viewing of a Moebius stent lumen is likely possible regardless of axis alignment, inherent structural weakness may be problematic. As a more practical choice, the solenoid stent is easier to manufacture and generates no hypointensive signal when the axis is parallel to B(0).

Late complications of nickel–titanium alloy stent in tracheal stenosis

To investigate and treat the late complications of using nickel-titanium alloy stents in laryngotracheal, bronchial, and esophageal stenosis patients who developed severe laryngotracheal stenosis (SLS). Retrospective clinical study. Thirteen patients with SLS or tracheoesophageal fistula secondary to insertion of a nickel-titanium alloy stent for treatment of laryngotracheal, bronchial, or esophageal stenosis treated between May 2004 and March 2010 were retrospectively analyzed. Of the 13 total patients, nine had one stent placed, and four had two stents placed. The late complications observed were glottic and/or subglottic extension of cervical tracheal stenosis (n = 6), new stricture of the thoracic trachea (n = 4), severe left bronchial stricture with massive left pulmonary collapse (n = 1), and cervical tracheoesophageal fistula (n = 2). Six patients with glottic and/or subglottic to cervical tracheal stenosis underwent successful laryngotracheal reconstruction. Two patients with subglottic and upper thoracic tracheal stenosis were successfully treated by staged operation for the stenosis. Two patients with subglottic and distal thoracic tracheal stenosis are still undergoing treatment. One patient with severe left bronchial stricture and massive left pulmonary collapse has been treated but has not achieved full recovery. One patient with cervical tracheoesophageal fistula underwent successful repair but died later from metastatic disease. One patient with tracheoesophageal fistula died from massive hemorrhage and asphyxiation induced by the stent, which had not been removed. The nickel-titanium alloy stents should be used with extreme caution in patients with laryngotracheal, bronchial, or esophageal stenosis treatment that can be corrected by surgical therapy.

Metal Ureteral Stent for Benign and Malignant Ureteral Obstruction

Metal ureteral stents are a relatively new version of a device with a long history of relieving ureteral obstruction. Metal stents are effective for relieving ureteral obstruction but success regarding patient tolerability has been variable. We present our single institution experience with long-term metal ureteral stent placement. The charts of patients undergoing metal ureteral stent placement for chronic ureteral obstruction were reviewed. Data collected included patient age, gender, diagnosis/cause of obstruction, laterality, duration of indwelling metal stent, number of routine metal stent changes, complications and early discontinuations or stent changes. A total of 23 patients underwent placement of metal ureteral stents between February 2008 and September 2010. Bilateral stents were placed in 5 patients and 9 underwent a yearly metal stent exchange for a total of 42 ureteral units treated with metal ureteral stents. All metal stents were placed to relieve ureteral obstruction due to ureteral stricture, ureteropelvic junction obstruction, retroperitoneal fibrosis or extrinsic malignant obstruction. There were 3 metal stent failures in 2 patients with malignant ureteral obstruction. There were no complications, or early discontinuations or changes due to adverse symptoms, patient dissatisfaction, worsening renal function or progressive hydronephrosis. Metal ureteral stents are effective for benign and malignant ureteral obstruction in the absence of urolithiasis. Good tolerability and annual stent exchange make metal stents an appealing alternative for patients with chronic ureteral obstruction treated with indwelling ureteral stents.

New Combined Approach in Metallic Ureteral Stenting to Avoid Urothelial Hyperplasia: Study in Swine Model

We assessed the therapeutic value of a new treatment option for ureteral strictures that may avoid urothelial hyperplasia, which is the main cause of metallic stent failure. We used 24 pigs in this study. An experimental model of ureteral stricture was induced in all animals. Obstruction was confirmed by ultrasound and retrograde ureteropyelogram 6 weeks after model creation. The pigs were then randomly allocated to 2 experimental groups. Therapy involved placement of a 6 × 30 mm metallic ureteral covered stent in the ureteral stricture in group 1 and subsequent endoureterotomy at the ureteral segments adjacent to the 2 ends of the stent in group 2. A double pigtail stent was then deployed for 3 weeks. Completion studies 6 months after therapy included retrograde ureteropyelogram, endoluminal ultrasound and ureteroscopy to assess urothelial hyperplasia formation. At the end of the study evidence of urothelial hyperplasia was seen in 50% of the pigs in group 1 and in 29% in group 2. Four and 2 cases of cranial stent migration in groups 1 and 2, respectively, were seen at 6 months. Hyperplasia and renal involvement were statistically significantly different between the groups with more damage in group 1 than in group 2. Hyperplasia was markedly reduced when ureteral peristalsis was inhibited by endoureterotomy at the area of interaction between the stent and the ureter.

Total arch replacement and open stent graft implantation using a newly developed stent graft: Report of a case

We experienced a case in which a total arch replacement and an open stent implantation were performed for a distal aortic arch aneurysm using a newly developed stent graft (Ube CL-0201; Ube Medical, Tokyo, Japan). This novel stent graft is composed of a woven polyester graft and a nickel-titanium alloy stent, and has been under evaluation in clinical trials at four institutions in Japan, including our hospital, since 2008. The patient was weaned from the respirator on the day after surgery, and 9 months have passed since the surgery with no complications. A follow-up computed tomography scan showed that the stent part was sufficiently open, and no complications, such as an endoleak, have been observed.

Experience of diagnosis and treatment for cervical tracheoesophageal fistula complicated with laryngotracheal stenosis

To explore the treatment of cervical tracheoesophageal fistula (TEF) with complicated or remnant laryngotracheal stenosis (LTS) and anterior neck defect (AND). From 1980 to 2007, 14 patients were diagnosed as TEF. Among them, 9 patients had complicated or remnant LTS, 3 patients had complicated AND, and 2 patients had TEF which were induced by Nickel-Titanium alloy mesh stent for treating benign esophageal stricture. All these patients were retrospectively studied in Tangdu Hospital. Treatment consisted of conservative therapy of TEF, staged surgical repair of TEF and laryngotracheal reconstruction according to the dimension (small or large) of TEF and complications. Four patients with small TEF (2 - 3 mm length) complicated LTS underwent laryngotracheal reconstruction stented with silicone T tube and TEF was adopted conservative treatment. The TEF and LTS were healed. Six patients with larger TEF (10 - 25 mm length) were repaired by staged surgical repair of TEF and laryngotracheal reconstruction. Among them, 3 cases had complicated LTS and AND, 2 cases had recent LTS and 1 case had TEF without complication. Two patients had TEF and LTS, whose TEF healed before laryngotracheal reconstruction, the remnant LTS were reconstructed and healed. During the follow-up ranged from one to ten years, 12 patients were successfully treated without complications. One patient with TEF and LTS was treated only LTS because of a segment of esophagus was closed and treated with esophagogastrostomy in the department of thoracic surgery after LTS was successfully reconstructed and cured. One patient died of bleeding and asphyxia induced by the Nickel-Titanium alloy stent because of the stent had not been taken out. The small cervical TEF complicated or remnant LTS can be treated by laryngotracheal reconstruction and conservative treatment of TEF at the same time. A larger TEF complicated LTS should be treated by staged repair of TEF and LTS.

Endotracheal Stent Granulation Stenosis Resolution after Colchicine Therapy in a Dog

Endotracheal Stent Granulation Stenosis Resolution after Colchicine Therapy in a Dog

Application of memory metallic stents to urinary tract disorders in pediatric patients

The use of memory metallic stents for the urinary tract in pediatric patients has not been reported. The authors report on 2 patients with urinary tract disorders who were successfully treated with a memory metallic stent. A thermoexpandable, nickel-titanium alloy stent was placed at the urethroureteral junction of a 4-year-old boy with ureteral stenosis associated with cloacal exstrophy for 18 months and at the urethra of a 2-year-old girl with ischuria after a repair of cloacal anomaly for 6 months. Temporary insertion of a memory metallic stent is a safe and effective alternative for organic stricture or functional obstruction of the urinary tract in pediatric patients.

BIOCOMPATIBILITY OF NITINOL AND STAINLESS STEEL IN THE BLADDER: AN EXPERIMENTAL STUDY

We tested the biocompatibility of nitinol, a nickel titanium alloy, and stainless steel (SS) as bladder implant materials. Rats received a nitinol implant, an SS implant or were sham controls. Two, 3, 6 and 8 weeks following implantation 24-hour voiding behavior studies were performed to investigate bladder irritation. All animals were sacrificed 8 weeks after implantation and a sample of urine was aspirated for culture. The bladders were examined by light microscopy and scanning electron microscopy (SEM). No visible encrustations or infections were noted in urine. Voiding frequency in the light period 6 weeks after implantation was significantly decreased in the 2 implant groups compared with sham controls. There were no other significant differences in frequency or mean volume per void in the light or dark periods at any time point. Light microscopy demonstrated similar implant tissue effects in all groups with little or no inflammation or fibrosis. Under SEM all implants showed a brittle, amorphous coating devoid of cells. The transition between the urothelium mucosa and the rod was smoother for SS than for nitinol, suggesting an affinity of SS for mucosa. In all nitinol rods discontinuity was present between the mucosa and rod. Nitinol and SS do not cause more irritation than the effects of surgery alone and the 2 materials seem to be biocompatible in the bladder. Nitinol may be more inert than SS based on SEM results.

NICKEL-TITANIUM SHAPE MEMORY ALLOY MEMOKATH 051 URETERAL STENT FOR MANAGING LONG-TERM URETERAL OBSTRUCTION: 4-YEAR EXPERIENCE

We present our 4-year experience with the thermo-expandable shape memory alloy Memokath 051 stent (Engineers and Doctors of Copenhagen, Copenhagen, Denmark) for managing long-term ureteral obstruction. We used a nickel-titanium shape memory alloy ureteral stent to treat 28 patients 29 to 86 years old (mean age 59.2). Ureteral obstruction was caused by malignancy in 18 cases and by recurrent benign disease in 10. A total of 37 stents were inserted from November 1996 to November 2000 using general anesthesia. Mean followup was 19.3 months (range 3 to 35). Upper tract decompression was achieved in all cases. Currently 15 stents are functional in 13 patients, while 8 patients died with a total of 13 functioning stents in place. In 7 patients 9 stents were removed for various reasons. There has been no radiological evidence of encrustation to date. No patient has been rehospitalized with stent related sepsis pain or hematuria, resulting in improved quality of life. This stent seems to provide a significant benefit over conventional Double-J (Medical Engineering Corp., New York, New York) and other metallic stents. Its remarkable thermal memory permits removal, a feature that until recently was not available in any other metallic ureteral stent. Durable and complication-free decompression of the upper tract can be achieved with the Memokath 051.

The self-expanding metallic ureteric stent in the long-term management of benign ureteric strictures.

To evaluate and assess the long-term complications of using the thermo-expandable, nickel-titanium alloy stent (Memokath 051, Engineers & Doctors A/S, Hornbaek, Denmark) for managing benign ureteric strictures. Over a 3-year period, 13 Memokath stents were inserted in 11 patients (mean age 58 years, range 35-85) with 12 lower ureteric strictures. The cause of the stricture was benign in all cases, i.e. radiation fibrosis in three, retroperitoneal fibrosis, ischaemic uretero-ileal anastomosis and scarring after ureteroscopy in two each, and diathermy damage, extraluminal endometriosis and stone passage in one each. Four stents were 9 F with proximal expansion to 17 F and the other nine used were 10.5 F with proximal expansion to 20 F. The patients were followed for a mean (range) of 18 (1.5-33) months. No complications or side-effects occurred with nine stents; four stents were removed at a mean (range) of 16.3 (4-33) months. Three of these had become encrusted, two of which had been placed in patients who had either a history of stone disease or recurrent urinary tract infection. The other stent had migrated. The Memokath stent appears to have a useful role in managing benign ureteric strictures, but it must be closely monitored in patients who are predisposed to encrustation.