Patent ID: 8500751

Claim:
A method for treating a bifurcation or trifurcation aneurysm, in a patient, occurring at a first artery, the first artery and a second artery joining to a third artery, the method comprising: inserting a medical device partially in the first artery and partially in the third artery, the medical device comprising an expandable latticework frame having a plurality of struts that each define a radially outermost edge, a radially innermost edge, and an axial strut width, the radially outermost edge and the radially innermost edge defining a wall thickness therebetween, the medical device further comprising a porous membrane that extends around and between the plurality of struts, the membrane having a single sheet web portion that extends only in a central region, from a first strut of the plurality of struts to a second strut adjacent to the first strut, the first strut being spaced from the second strut at an interstitial spacing that is greater than the first or second axial strut width, the central region being (i) bounded radially between the radially outermost edges and the radially innermost edges of the first and second struts and (ii) bounded axially between the first strut and the second strut, the membrane web portion defining a web thickness that is less than the first or second strut wall thickness, the device having a flexibility such that the frame can be deflected 1 mm from a neutral line by applying a force against the frame of less than 8 grams; expanding the device radially outwardly from a first position to a second position such that, when the device is in the second position, a first region of an exterior surface of the device engages an inner surface of the first artery and a second region of the exterior surface of the device engages an inner surface of the third artery, so as to maintain a fluid pathway through said arteries; and positioning the device such that, when the device is in the second position, the porous membrane, secured to the device, is located at a neck of the aneurysm; wherein the membrane has a substantially uniform porosity over a length extending from a distal end of the membrane to a proximal end of the membrane, and a distance between adjacent pores of the membrane does not exceed 75 microns; and wherein, when the device is in the second position and the membrane is positioned at the neck of the aneurysm, the membrane is effective to: (i) reduce blood supply into the aneurysm, and (ii) permit blood supply through pores of the membrane and into perforators and/or microscopic branches of the first artery so as not to inhibit blood supply functions of the perforators and/or microscopic branches.