Ex vivo evaluation of anti-migration forces of ureteral self-expanding metal stents with different flange designs

To evaluate the anti-migration forces of ureteral self-expanding metal stents (SEMS) with various flange designs. In the initial study, 240 fresh porcine ureters were divided into ten groups to evaluate ten custom-made SEMS (Type I-X). Type I and II lacked flanges (8 mm and 10 mm diameters, respectively), while Types III-X had various proximal flange designs. In the subsequent study, 96 ureters were divided into four groups to evaluate four SEMS: a custom-made prototype with the same flange design as Type X (double-stepped shoulders) and three commercial stents, including Urexel, Uventa, and Allium. Proximal and distal anti-migration forces were measured using a universal testing machine. In the initial study, only Type X demonstrated a significantly higher distal anti-migration force than the 8-mm non-flanged SEMS (Type I) (P = 0.001). None of the SEMS (Types II-X) showed significantly higher proximal anti-migration force compared to Type I (all > 0.05). In the subsequent study, Uventa demonstrated significantly higher proximal and distal anti-migration forces than the prototype (P < 0.001 and P = 0.001, respectively). The prototype demonstrated significantly higher proximal and distal anti-migration forces than Urexel (both P < 0.001). Allium unraveled during initial testing and was excluded from the analysis. Only the double-stepped shoulders improved distal anti-migration force among eight flange designs. Compared with commercial SEMS, the prototype featuring this design demonstrated higher anti-migration force than Urexel but lower than Uventa.