Expandable stent

Abstract

An expandable stent comprising a tubular body made up of a plurality of separated tubular elements ( 1 ) arranged along a common longitudinal axis. Each tubular element ( 1 ) comprises a plurality of rhombic-shaped closed cell elements ( 2 ) joined by circumferentially extending linking members ( 3 ). The closed cell elements ( 2 ) are expandable to allow the tubular elements, and hence the stent itself, to expand. In the direction of the longitudinal axis of the stent, the extremities of each of the closed cell elements has an enlarged loop ( 30 ) with waisted portions ( 33 ) which allow the tubular elements to interlock to create a stable structure, at least when in the unexpanded condition.

1 . A stent comprising a tubular body made up of a plurality of separate, radially expandable, tubular elements aligned along a common longitudinal axis, wherein at least some of the tubular elements each comprise a plurality of closed cell elements, each joined to the next by a circumferentially-extending linking member.  
     
     
         2 . A stent as claimed in  claim 1  wherein the tubular elements are also compressible.  
     
     
         3 . A stent as claimed in  claim 1  further including interlock means for mechanically holding the tubular elements together, at least in an unexpanded condition of the stent.  
     
     
         4 . A stent as claimed in  claim 3  in which said interlock means are provided by inter-engaging elements provided on said tubular elements.  
     
     
         5 . A stent as claimed in  claim 4  wherein each of said closed cell elements is provided with a respective inter-engaging element which engages a corresponding inter-engaging element on an adjacent tubular element.  
     
     
         6 . A stent as claimed in  claim 1  wherein some, but not all, of said closed cell elements are provided with a respective inter-engaging element which engages a corresponding inter-engaging element on an adjacent tubular element.  
     
     
         7 . A stent as claimed in  claim 1  wherein each closed cell element is expandable in the circumferential direction of the tubular element, thus allowing the tubular element to expand and contract.  
     
     
         8 . A stent as claimed in  claim 7  wherein each closed cell element is positioned symmetrically with respect to the circumferential linking members.  
     
     
         9 . A stent as claimed in  claim 7  wherein each closed cell element comprises two attachment points at each of which it joins to a respective circumferential linking member, and wherein the closed cell element is such as to be capable of expanding from a first position in which the attachment points are relatively close together, to a second position in which the attachment points are relatively further apart.  
     
     
         10 . A stent as claimed in  claim 9  wherein, between said attachment points, each closed cell element comprises proximal and distal members, mutually spaced apart in the direction of the longitudinal axis, said proximal and distal members being capable of bending to accommodate the expansion from the first position to the second position.  
     
     
         11 . A stent as claimed in  claim 10  wherein the proximal and distal members of each closed cell element are joined together at each of their circumferentially spaced ends by means of a respective hinge member.  
     
     
         12 . A stent as claimed in  claim 11  wherein each hinge member is attached at one end of a respective circumferentially-extending linking members the other end of the linking member having attached thereto the opposite hinge member of the next adjacent closed cell element.  
     
     
         13 . A stent as claimed in  claim 10  wherein the proximal and distal members each comprise a flexible member joining the attachment points.  
     
     
         14 . A stent as claimed in  claim 10  wherein the proximal and distal members each comprise two or more relatively rigid side members joined by a hinge.  
     
     
         15 . A stent as claimed in  claim 14  wherein said four side members together form the shape of a rhombus.  
     
     
         16 . A stent as claimed in  claim 14  wherein each of said side members is of rectilinear shape.  
     
     
         17 . A stent as claimed in claims  5  or  10  wherein said inter-engaging elements are each formed by a respective loop formed by each of said proximal and distal members.  
     
     
         18 . A stent as claimed in  claim 14  wherein the hinge joining each of said two side members comprises a loop which forms one of said inter-engaging elements, and wherein the loop joins the adjacent side members by a waisted portion which, together with the corresponding waisted portion from the next adjacent closed cell element in the same tubular element, forms a cooperating inter-engaging element.  
     
     
         19 . A stent as claimed in  claim 1  wherein all of the closed cell elements making up each tubular element are of the same shape.  
     
     
         20 . A stent as claimed in  claim 1  wherein some of the closed cell elements making up each tubular element are of a different shape to the remainder.  
     
     
         21 . A stent as claimed in  claim 1  wherein the exterior surface of the tubular body is equipped with wells which open onto its exterior surface, said wells being suitable to contain one or more therapeutic agents.  
     
     
         22 . A stent as claimed in  claim 21  in which the wells comprise holes or grooves opening into the exterior surface of the stent.  
     
     
         23 . A stent as claimed in  claim 22  wherein the holes or grooves are blind, i.e. do not pass through the material of the stent.  
     
     
         24 . A stent as claimed in  claim 22  wherein the holes or grooves pass through to the interior of the stent.  
     
     
         25 . A stent as claimed in  claim 24  in which the inner end of the hole or groove, is plugged by a material which prevents or considerably reduces the flow of therapeutic agent therethrough.  
     
     
         26 . A stent as claimed in  claim 25  wherein said material is, or contains, therapeutic agent.  
     
     
         27 . A stent as claimed in  claim 21  wherein the closed cell elements are formed with blocks on each of which are formed one or more of said wells.  
     
     
         28 . A stent as claimed in  claim 21  wherein at least some of said wells contain multiple therapeutic agents arranged in layers so as to release in sequence.