Bench-top Comparison of Physical Properties of 4 Commercially-Available Self-Expanding Intracranial Stents

Abstract

PurposeTo better understand the performance of four commercially available neurovascular stents in intracranial aneurysm embolization, the stents were compared in terms of their basic morphological and mechanical properties.Materials and MethodsFour different types of stents that are currently being used for cerebral aneurysm embolization were prepared (two stents per type). Two were laser-cut stents (Neuroform and Enterprise) and two were braided from a single nitinol wire (LEO and LVIS stents). All were subjected to quantitative measurements of stent size, pore density, metal coverage, the force needed to load, push, and deploy the stent, radial force on deployment, surface roughness, and corrosion resistance.ResultsCompared to their nominal diameters, all stents had greater diameters after deployment. The length generally decreased after deployment. This was particularly marked in the braided stents. The braided stents also had higher pore densities than the laser-cut stents. Metal coverage was highest in the LEO stent (14%) and lowest in the Enterprise stent (5%). The LIVS stent had the highest microcatheter loading force (81.5 gf). The LEO stent had the highest passage force (55.0 gf) and deployment force (78.9 gf). The LVIS and LEO stents had the highest perpendicular (37.1 gf) and circumferential (178.4 gf) radial forces, respectively. The Enterprise stent had the roughest stent wire, followed by the LVIS, LEO, and Neuroform stents.ConclusionThe four neurovascular stent types differed in terms of morphological and physical characteristics. An understanding of this diversity may help to decide which stent is most suitable for specific clinical situations.

Flow-Diversion Effect of LEO Stents: Aneurysm Occlusion and Flow Remodeling of Covered Side Branches and Perforators

“…10 The braided stents have relatively higher pore density (0.979 and 0.782 pore/mm 2 ) than the laser-cut stents (0.276 pore/mm 2 for both Enterprise [Codman & Shurtleff, Raynham, Massachusetts] and Neuroform [Stryker Neurovascular, Kalamazoo, Michigan] stents), giving greater metal coverage (14% for LEO stents versus 5%-10% for Enterprise and Neuroform stents). 2 These characteristics may have important therapeutic implications. Indeed, although their metal surface coverage is lower than that in a flow diverter (30% for the Pipeline Embolization Device; Covidien, Irvine, California), LEO stents have been successfully used as stent monotherapy, especially for distal and complex small aneurysms.…”

“…1 Based on the braided morphology, LEO stents have a relatively small pore size (cell size of approximately 0.9 mm) that gives a higher metal coverage ratio compared with other self-expandable stents, allowing a certain grade of flow-diverting hemodynamic effect. 2 Accordingly, LEO stents have been recently reported as stent monotherapy for the treatment of small and complex intracranial aneurysms based on their flow-modification capacity and their biologic effects. 3,4 The deployment of low-porosity flow-diverter stents across side branches or perforators has a potential risk of occlusion and related symptomatic ischemic lesions.…”

Treatment of Intracranial Aneurysms with Self-Expandable Braided Stents: A Systematic Review and Meta-Analysis

“…4,5 In addition to providing mechanical support, the braided morphology gives a relatively higher pore density than the laser-cut stents, theoretically improving the flow-diverting hemodynamic effect of these devic-es. [6][7][8] Recently, the low-profile design of the braided stents (LEO Baby and LVIS Jr) allowed delivery through a 0.0165-inch microcatheter and navigation in small vessels, with the possibility of treating distally located aneurysms. 9,10 Improved understanding of treatment-related outcomes of braided stents can help practitioners in the selection of lesions amenable to being effectively treated with these devices.…”

Flow diversion for treatment of intracranial aneurysms: Mechanism and implications

“…17 This means that FDs have a lower ratio of metal-free surface area to total stent surface area. For example, the metal coverage for the PED is roughly 30%, whereas the metal coverage for traditional stents typically ranges from 5 to 16%.…”

“…For example, the metal coverage for the PED is roughly 30%, whereas the metal coverage for traditional stents typically ranges from 5 to 16%. 17 This means that FDs have a lower ratio of metal-free surface area to total stent surface area. Therefore, they have a higher degree of metal coverage, this being the ratio of surface area covered by metal to total surface area of the stent.…”