Expandable medical device with ductile hinges

Abstract

An expandable tissue supporting device of the present invention employs ductile hinges at selected points in the expandable device. When expansion forces are applied to the device as a whole, the ductile hinges concentrate expansion stresses and strains in small well defined areas. The expandable tissue supporting device includes a plurality of elongated-beams arranged in a cylindrical device and connected together by a plurality of ductile hinges. Although many ductile hinge configurations are possible, the ductile hinges preferably have a substantially constant hinge cross sectional area which is smaller than a beam cross sectional area such that as the device is expanded from a first diameter to a second diameter, the ductile hinges experience plastic deformation while the beams are not plastically deformed. The expandable tissue supporting device can be provided with segments which may be expanded in a specified sequence and/or framed hole features for accommodating bifurcations.

What is claimed is:  
     
         1 . An expandable medical device comprising: 
 a plurality of elongated beams, the plurality of elongated beams joined together to form a substantially cylindrical device which is radially expandable, the plurality of elongated beams having a beam width in a circumferential direction;    a plurality of ductile hinges connecting the plurality of beams together in the substantially cylindrical device, the ductile hinges having a width in a circumferential direction along a portion of a hinge length which is smaller than the beam width such that as the device is expanded the ductile hinges experience plastic deformation while the beams are not plastically deformed; and    wherein a first section of the substantially cylindrical device includes ductile hinges having a first width and a second section of the substantially cylindrical device includes ductile hinges having a second width different from the first width such that the first section expands before the second section.    
     
     
         2 . The expandable medical device according to  claim 1 , wherein the first section is a substantially cylindrical section at a first end of the device and the second section is a substantially cylindrical section at a second end of the device.  
     
     
         3 . The expandable medical device according to  claim 1 , wherein the first width and the second width are selected such that the entire first section expands prior to expansion of the second section.  
     
     
         4 . The expandable medical device according to  claim 1 , further comprising a balloon for expanding the device from a first diameter to a second diameter.  
     
     
         5 . The expandable medical device according the  claim 1 , further comprising a geometric deflection limiting feature for limiting an amount of bending of the ductile hinges.  
     
     
         6 . The expandable medical device according to  claim 5 , wherein the geometric deflection limiting feature is a V-shaped notch having side surfaces which contact each other when a maximum amount of bending is reached.  
     
     
         7 . The expandable medical device according to  claim 1 , wherein the plurality of elongated beams extend substantially axially and a plurality of circumferential beams are each connected at first and second ends to one of the axial beams by a ductile hinge.  
     
     
         8 . The expandable medical device according to  claim 1 , further comprising a side access hole formed in the device in an unexpanded state which accommodate a vessel bifurcation when the device is expanded.  
     
     
         9 . An expandable medical device comprising: 
 a plurality of elongated beams, the plurality of elongated beams joined together in a regular pattern to form a substantially cylindrical device which is radially expandable, the plurality of elongated beams having a beam width in a circumferential direction;    a plurality of ductile hinges connecting the plurality of beams together in the substantially cylindrical device, the ductile hinges having a width in a circumferential direction along a portion of a hinge length which is smaller than the beam width such that as the device is expanded the ductile hinges experience plastic deformation while the beams are not plastically deformed; and    a hole feature interrupting the regular pattern of the plurality of beams.    
     
     
         10 . The expandable medical device according to  claim 9 , wherein the hole feature is configured to accommodate a bifurcation in an artery.  
     
     
         11 . The expandable medical device according to  claim 9 , wherein the hole feature has a width in an unexpanded configuration of the device which is at least the width of two beams.  
     
     
         12 . The expandable medical device according to  claim 9 , wherein a plurality of ductile hinges surrounding the hole feature bend at a lower expansion force than a remainder of the ductile hinges.  
     
     
         13 . The expandable medical device according to  claim 9 , further comprising a geometric deflection limiting feature for limiting an amount of bending of the ductile hinges.  
     
     
         14 . The expandable medical device according to  claim 9 , wherein the hole feature is framed by a plurality of the elongated beams connected by a plurality of the ductile hinges.  
     
     
         15 . A method of expanding a medical device comprising: 
 providing a substantially cylindrical expandable medical device having a first section with ductile hinges of a first configuration and a second section with ductile hinges of a second configuration which requires a different force for expansion than the first configuration; and    expanding the device in a controlled expansion sequence with an expandable member.    
     
     
         16 . The method according to  claim 15 , wherein the hinges having the first configuration have a first hinge width which is smaller than a second hinge width of the hinges having the second configuration.  
     
     
         17 . The method according to  claim 15 , wherein the first section is expanded prior to expansion of the second section.  
     
     
         18 . The method according to  claim 15 , wherein the expansion is performed by inflating a balloon inside the cylindrical device.