In Vitro Comparison of Self-Expanding Versus Balloon-Expandable Stents in a Human Ex Vivo Model

Abstract

The objective was to compare the radial strength and expansile precision of self-expanding stents and balloon-expandable stents in a human cadaver bifurcation model. Seven different self-expanding (LUMINEXX, JOSTENT SelfX, JOSTENT SelfX hrf, Sinus-Repo, Sinus SuperFlex, Easy Wallstent, SMART) and four different balloon-expandable stent models (Palmaz, Sinus Stent, SAXX Medium, JOSTENT peripheral), each type 10 stents (total n = 110 stents) were implanted into the common iliac arteries of human cadaver corpses. The maximum stent diameter was 10 mm for all models. After stent implantation, the specimens were filled with silicone caoutchouc. After 24 h, the vascular walls including the stents were removed from the hardened casts. Diameters were taken and the weight of the cast cylinders was measured in air and in purified water to calculate the volume of the bodies (according to Archimedes Law) as a relative but precise degree for the radial strength of the implanted stents. The cylindrical casts of the self-expanding stents showed lower mean diameters (8.2 +/- 1.0 mm) and mean volumes (0.60 +/- 0.14 ml/cm) than in the balloon-expandable stent group (10.1 +/- 0.3 mm and 0.71 +/- 0.04 ml/cm, respectively; p < 0.01). The nominal maximum diameter of 10 mm was not achieved in any of the self-expanding stents, but this was achieved in more than 70% (29/40) of the balloon-expandable stent specimens (p < 0.05). The variation between achieved volumes was significantly larger in self-expanding (range: 0.23-0.78 ml/cm) than in balloon-expandable stents (range: 0.66-0.81 ml/cm; p < 0.05). Self-expanding stents presented considerably lower radial expansion force and lower degree of precision than balloon-expandable stents.

Delivery and release of nitinol stent in carotid artery and their interactions: A finite element analysis

“…The insufficient stent scaffolding also accords with the experimental results of nitinol stents, which had considerably lower radial expansion force than stainless-steel stents (Grenacher et al, 2006). This phenomenon can be partially explained by much lower Young's modulus of nitinol (60 GPa here) than that of stainless steel (about 200 GPa).…”

“…However, in-stent restenosis of CAS still remains (Clark et al, 2006) and a trial to prove noninferiority of CAS vs. CEA failed recently (Ringleb et al, 2006). The nitinol stent biomechanical properties and stent-vessel interactions are considered as two of major factors of shortand long-term stenting outcomes (Hart et al, 2006), which are studied by experiments (Tanaka et al, 2004;Hanus and Zahora, 2005;Grenacher et al, 2006) or finite element methods (FEM) (Whitcher, 1997;Migliavacca et al, 2004;Brand and Ryvkin, 2005). However, nitinol stent implantation in carotid arteries has not been studied by FEM yet.…”

Endograft Sizing for Abdominal Aortic Aneurysms

“…In a study with longer follow-up (4 years) but with smaller sample size, all patients showed at least 2 mm of neck dilatation [33]. These results follow a previous description that the self-expandable stent-grafts dilate the aortic neck until the nominal diameter of the stent graft is reached [34]. This initial adaptation has been reported for almost all the self-expandable endograft-treated aortic necks as an adjustment to the devices present and is associated with the percentage of oversizing [31].…”

Self-expanding stents and aortoiliac occlusive disease: a review of the literature

“…Moreover, precision and reproducibility of the achieved expansion was significantly lower in the self-expanding group 47. As the self-expandable stent begins to emerge from the constraint, there is a natural tendency for it to spring forward that results from several stent properties, including bridge design, longitudinal stiffness, and friction.…”