An in vitro study of silk stent morphology

Abstract

By design, the wires of the silk stent move relative to each other. In a curved model, the PAC is different at the convexity, concavity, and lateral walls. The stent diameter affects the PAC. These results are clinically relevant because it is desirable to maximize and minimize the PAC across the aneurysm neck and branch vessel orifice, respectively.

The Varying Porosity of Braided Self-Expanding Stents and Flow Diverters: An Experimental Study

“…6,7 The increased porosities on the convexity of an acute curve may also decrease the efficacy of a FD strategy. 2,4 This has recently been shown in computational fluid dynamics models. 7 Although the bench experiments can show the changing porosity of the device, the reality of deploying flow diverters within a curve is more complex.…”

“…1,2,5 The benchtop experiments presented here were designed to model in vivo findings we encountered after experimentation in a canine aneurysm model, as shown in Fig 7. Many of our observations were most obvious when there was a significant discrepancy between stent size and vessel lumen. Previous in vitro studies have emphasized the importance of matching the size of the device with the diameter of the parent artery, 4 and to this we are adding that device oversizing may also increase the length of the transition zone, a segment of device whose porosity is greater than the expansion zone. It is noteworthy that unlike the compaction zone, the porosity of the transition Zone 2 cannot be decreased with technical maneuvers such as axial compression.…”

“…2,3 In vitro studies that have hitherto been published have failed to uncover these variations because they studied stents and FDs in closed tubes. 4 We here present the results of several simple experiments that permit a better understanding and more accurate prediction of the changes in structure of braided self-expanding stents and FDs as these adapt to the common types of geometric constraints encountered in treating aneurysms. This work can help inform the proper choice of stent and length of landing zone, and perhaps also illuminate some technical aspects of an intervention, in terms of the utility of the practice of intentional device compaction across the aneurysm neck.…”

Flow-Diverter Silk Stent for the Treatment of Intracranial Aneurysms: 1-year Follow-Up in a Multicenter Study

“…The incidence of acute PAO in the literature is difficult to compare from Silk to Pipeline (Chestnut Medical Technologies, Menlo Park, California) studies because of population heterogeneity, but it seems that PAO is more likely to happen with the Silk stent: 9.3% in our experience; 10% in the series of Byrne et al 10 ; and 4% in the experience of Lubicz et al 12 rather than with the Pipeline device: no PAO in the Lylyk et al 4 and Nelson et al 5 series; and 2.4% in the series of Szikora et al 3 A curved landing zone and stent oversizing are the main parameters to take into account. 13 Therefore, accurate preoperative measurements both upstream and downstream of the landing zone are critical to match the Silk stent to the arterial diameter. Stent coverage of perforators or side branch arteries may be responsible for ischemic complications.…”

Actual Metal Coverage at the Neck Is Critical for Flow-Diverting Stents in Treating Intracranial Aneurysms

“…4 In an in vitro study of SFD morphology, the local actual MCR of the FD stent at different curvatures in different vessel models can change from 19% to 63%. 5 The MCR decreases to a minimum, which is only approximately 20%, when the included angle decreases to 90°in an FD stent as shown in Fig 1. This actual MCR at the neck may not significantly change hemodynamics. Even though the included angle between wires can enhance the MCR when decreased to Ͻ90°, the stent is severely stretched; this change may cause the stent not to open.…”