An endoprosthesis for delivery in a body lumen comprising: an annular element defined by a set of interconnected strut members, each strut member of the annular element including a first end and a second end (22"), the annular element being expandable between an unexpanded configuration and an expanded configuration; the first end of selected pair of circumferentially-adjacent strut members of the annular element being interconnected to define apices proximate a first longitudinal side of the annular element and the second end of selected pairs circumferentially-adjacent strut members being interconnected to define apices proximate a second longitudinal side of the annular element; characterized by: at least one of the selected pairs of circumferentially-adjacent strut members (508, 510) having a modulator (502, 504) disposed proximate the apex defined therebetween, the modulator having a first mode to allow expansion of the annular element from the unexpanded configuration toward the expanded configuration and a second mode to resist contraction of the annular element from the expanded configuration toward the unexpanded configuration, wherein the modulator (502, 504) includes a second segment extending between the strut members of the at least one selected pair of circumferentially-adjacent strut members (508, 510), the second segment having a bistable property between the first mode and the second mode and having at least two segments defining an angle therebetween. an annular element defined by a set of interconnected strut members, each strut member of the annular element including a first end and a second end (22"), the annular element being expandable between an unexpanded configuration and an expanded configuration; the first end of selected pair of circumferentially-adjacent strut members of the annular element being interconnected to define apices proximate a first longitudinal side of the annular element and the second end of selected pairs circumferentially-adjacent strut members being interconnected to define apices proximate a second longitudinal side of the annular element; characterized by: at least one of the selected pairs of circumferentially-adjacent strut members (508, 510) having a modulator (502, 504) disposed proximate the apex defined therebetween, the modulator having a first mode to allow expansion of the annular element from the unexpanded configuration toward the expanded configuration and a second mode to resist contraction of the annular element from the expanded configuration toward the unexpanded configuration, wherein the modulator (502, 504) includes a second segment extending between the strut members of the at least one selected pair of circumferentially-adjacent strut members (508, 510), the second segment having a bistable property between the first mode and the second mode and having at least two segments defining an angle therebetween. at least one of the selected pairs of circumferentially-adjacent strut members (508, 510) having a modulator (502, 504) disposed proximate the apex defined therebetween, the modulator having a first mode to allow expansion of the annular element from the unexpanded configuration toward the expanded configuration and a second mode to resist contraction of the annular element from the expanded configuration toward the unexpanded configuration, wherein the modulator (502, 504) includes a second segment extending between the strut members of the at least one selected pair of circumferentially-adjacent strut members (508, 510), the second segment having a bistable property between the first mode and the second mode and having at least two segments defining an angle therebetween.