China
Africa
Explore chapters and articles related to this topic
Principles of Surgical Management
Published in Alaaeldin (Alaa) Azmi Ahmad, Aakash Agarwal, Early-Onset Scoliosis, 2021
Initial staples used for spinal deformities were similar to those used in long bones and made of stainless steel. Being rigid, they were prone to dislodge due to motion in the spine. To overcome this, special staples made up of Nitinol (Nickel Titanium Naval Ordnance Laboratory) were designed. Nitinol is a biocompatible metal alloy of 50% titanium and 50% nickel. The uniqueness of this staple is that it is made out of a shape memory alloy in which the prongs are straight when cooled but assume a C-clamp shape in the bone for secure fixation when the staple returns to body temperature. The temperature at which the staples will undergo the shape transformation can be controlled by the manufacturing process [13]. Nitinol has a low corrosion rate, has been used extensively in orthodontic implants and cardiovascular stents, and found to be safe. It does not lead to significant elevations in the nickel levels in the tissues or blood, and its properties are not altered with any sterilization methods used in the operating room [14,15]. The US Food and Drug Administration has given 510(k) approval for Nitinol shape memory staples for fixation of a bone screw in the anterior spine as well as for hand and foot osteotomies. The staples are not approved for use across the disc space and are used off-label [16].
Guidewires
Published in Vikram S. Kashyap, Matthew Janko, Justin A. Smith, Endovascular Tools & Techniques Made Easy, 2020
Justin A. Smith, Ravi N. Ambani, Karem C. Harth
Core Material: Stainless steel and nitinol are the primary materials found in the core of wires. Stainless steel is generally stiffer, providing the user with greater ability to steer the guidewire tip and superior support, while flexible enough to navigate tortuous vessels; this material also retains its shape better, conveying greater durability (2). Stainless steel can generally be found in the cores of support/working wires (e.g., Amplatz, Lunderquist) used to carry large endografts (thoracic endovascular aortic repair [TEVAR], endovascular aneurysm repair [EVAR]) where a stiff guide is paramount to ensuring these devices track safely and reliably into place. Nitinol is known for being malleable and highly flexible. Malleability allows better navigation along more tortuous vessels while flexibility allows it to be resistant to kinking, which would prevent further passage down a vessel (2). Such nitinol cores are useful in specialty wires used to navigate tortuous vessels, or cross-complex lesions, conveying good support with the flexibility to track and cross, establishing initial access to be used for wire exchange or device delivery. Wire cores can be either homogenous in their material construction or heterogeneous with transitions from proximal to distal (usually stainless steel at the shaft and nitinol at the tip).
Results of the United States Multicenter Prospective Study Evaluating the Zenith Fenestrated Endovascular Graft for Treatment of Juxtarenal Abdominal Aortic Aneurysms
Published in Juan Carlos Jimenez, Samuel Eric Wilson, 50 Landmark Papers Every Vascular and Endovascular Surgeon Should Know, 2020
Juan Carlos Jimenez, Samuel Eric Wilson
The Zenith fenestrated stent graft has design limitations imposed by the original trial design. Although outside the United States these devices can be manufactured with almost no design constraint with respect to the number of fenestrations and the delivery system, in the United States the stent is approved with a maximum of three fenestrations, of which only two are reinforced by nitinol ring. Therefore, the design is applicable to approximately two-thirds of the overall patient population of complex abdominal aortic aneurysms. Patients with pararenal or paravisceral aneurysms, and those with extent IV thoracoabdominal aortic aneurysms are not ideally suited for the current version of the Zenith fenestrated stent graft. In these cases, devices designed with four fenestrations and a supra-celiac seal zone provide a more durable alternative and reliable seal. To overcome these anatomical constraints, ongoing and future design trials, such as the Gore thoracoabdominal multibranched endoprosthesis (TAMBE) and the Cook Zenith fenestrated plus trials, will investigate the more extensive designs.
Intraoperative Left Atrial Appendage Occluder Implantation with the Amplatzer Cardiac Plug
Published in Structural Heart, 2021
Jeffrey A. Marbach, Marino Labinaz, Vincent Chan, Trevor Simard, Anthony Poulin, Mark Hynes, Mimi Xiaoming Deng, Benjamin Hibbert
In this small cohort study, we evaluated the feasibility of surgical device implantation for LAAO using an approved device designed for percutaneous implantation. Intra-operative TEE was satisfactory for device size selection, and implantation resulted in satisfactory clinical and echocardiographic outcomes out to 6 months. While not designed for surgical implantation, the nitinol base frame was optimal for device compression and seating in the LAA during surgical implantation. While two implants had residual gaps with residual flow, these were within acceptable limits for percutaneous implants and the long-term implications for stroke risk appear to be minima l. Of note, limitations of traditional surgical techniques include incomplete occlusion (10–77%), atrial tears resulting in tamponade and a remnant thrombogenic stump.2 Certainly, associated pericardial effusions and device-related thrombus are known complications from percutaneous implants and likely would be seen in larger series. Nevertheless, our report highlights the feasibility of surgical implantation, which may offer a simple, reproducible LAAO in patients undergoing CV surgery. Studies with currently approved or novel designed implants are warranted to test for efficacy and safety.
Devices for transcatheter mitral valve repair: current technology and a glimpse into the future
Published in Expert Review of Medical Devices, 2021
Daniel Perez-Camargo, Mi Chen, Maurizio Taramasso
The Carillon system consists of an implant device and a 9-Fr delivery catheter. The implant is made of nitinol and has three main components: a pair of distal and proximal anchors and a fixed-length arc which connects the two anchors. The distal anchor is intended to be deployed and locked in the distal CS and to subsequently plicate the mitral periannular tissue by tensioning the delivery catheter; once a satisfactory reduction in MR and adequate coronary perfusion is observed, the proximal anchor is deployed and locked in the proximal CS [72]. In 2016, an updated device was launched (mXE2), with new features in the anchoring mechanism to reduce the strain in the device [73]. Given that the system doesn’t directly interact with the MV, it allows for future interventions if required. Nonetheless, important caveats must be mentioned: first, the CS is immediately adjacent to the LA free wall, not the mitral annulus, which is estimated to be on average, 9.7 mm below the CS; second, the anatomic relation and proximity between the CS and the main circumflex artery or its branches has the potential for ischemic complications; finally, the implant device might preclude other devices deployment in the CS, such as resynchronization therapy leads or vice versa [74].
Device profile of the Wingspan Stent System for the treatment of intracranial atherosclerotic disease: overview of its safety and efficacy
Published in Expert Review of Medical Devices, 2020
Zachary R. Barnard, Michael J. Alexander
The stent is made of highly elastic nitinol, which is an alloy composed of 55% Nickel and 45% Titanium. Nitinol has been shown to have excellent biocompatibility in numerous medical implants. Its passive titanium oxynitride layer protects the alloy from corrosion and minimizes nickel release [1]. The nitinol is laser-cut, and subsequently undergoes a heat treatment process, which sets the stent shape and fixes the elastic properties of the finished stent. The stent surface is then treated through a series of processes including mechanical deburring, chemical etching, and electrochemical polishing and passivation processes. These processes make the stent surface smoother and less thrombogenic as an arterial implant. The nitinol stent is not well visualized on fluoroscopy, so there are four radio-opaque markers at both ends of the stent in order to visualize the stent position during delivery. As the stent is delivered and begins to expand, the four markers on the ends of the stent spread apart to appose the arterial inner lumen. These marker bands consist of 90% platinum and 10% iridium and are easier to visualize than the stent itself on both fluoroscopic imaging and x-ray spot films. The markers are flattened tubes appearing rectangular in shape and each measures 0.03 inches long, 0.0136 inches wide, and 0.0065 inches high.