AIM: Self-expandable metallic stents (SEMS) for the gastrointestinal tract have different types of flanges at either the oral end or both ends to prevent stent migration. The effect of flange shape on the properties of SEMS, to our knowledge, has not been evaluated. The aim of this study was to measure the strain that a SEMS imposes on the adjacent wall and the anti-migration force (AF) exerted by three stents, each with a different flange shape. METHODS: Stents with one of three different flanges (flared, dumbbell, and barrel) were designed and then their strain and AF values were measured with apparatuses devised in our laboratory. RESULTS: Although the average maximal strain values at the flange were similar (508.4 µm/m, 513.3 µm/m and 486.4 µm/m for flared, dumbbell and barrel, respectively), strain values for each position differed among the three different types of stents. Strain values for the flared shape increased toward the stent end, reaching the maximum value. Maximal strain values for the dumbbell and barrel shapes were observed near the flange's midpoint. Maximal AF values differed significantly according to flange shape. Thus, the median maximal AF values were 1.85 newton, 1.35 newton, and 1.13 newton, for barrel, dumbbell and flared shapes, respectively. CONCLUSIONS: The performance of braided esophageal SEMS with barrel shaped flanges is superior to that of SEMS with dumbbell or flared flanges, based on the strain on the adjacent wall and the prevention of stent migration.
AIM: Self-expandable metallic stents (SEMS) for the gastrointestinal tract have different types of flanges at either the oral end or both ends to prevent stent migration. The effect of flange shape on the properties of SEMS, to our knowledge, has not been evaluated. The aim of this study was to measure the strain that a SEMS imposes on the adjacent wall and the anti-migration force (AF) exerted by three stents, each with a different flange shape. METHODS: Stents with one of three different flanges (flared, dumbbell, and barrel) were designed and then their strain and AF values were measured with apparatuses devised in our laboratory. RESULTS: Although the average maximal strain values at the flange were similar (508.4 µm/m, 513.3 µm/m and 486.4 µm/m for flared, dumbbell and barrel, respectively), strain values for each position differed among the three different types of stents. Strain values for the flared shape increased toward the stent end, reaching the maximum value. Maximal strain values for the dumbbell and barrel shapes were observed near the flange's midpoint. Maximal AF values differed significantly according to flange shape. Thus, the median maximal AF values were 1.85 newton, 1.35 newton, and 1.13 newton, for barrel, dumbbell and flared shapes, respectively. CONCLUSIONS: The performance of braided esophageal SEMS with barrel shaped flanges is superior to that of SEMS with dumbbell or flared flanges, based on the strain on the adjacent wall and the prevention of stent migration.