Deployable stent

Abstract

A stent 1 comprises a sheet 2 of biocompatible material having a tubular shape and folded with a pattern of folds allowing the sheet 2 to be collapsed for deployment. The pattern of folds comprises a unit cell repeated over the sheet 2 . A variety of different unit cells 3 are described. The pattern of folds may progress helically around the tubular shape of the sheet 2 which assists in implantation by synchronising deployment. The stent 1 further comprises a frame extending around the tubular shape of the sheet 2 and reinforcing the sheet 2 . The frame comprises a plurality of elongate members arranged to fold relative to each other in conformity with the sheet 2 to allow the frame to be collapsed with the sheet 2 for deployment of the stent 1 . The stent 1 prevents tissue in-growth because it is formed of a continuous sheet 2.

1 . A stent comprising a biocompatible sheet having a tubular shape and being folded with a pattern of folds allowing the sheet to be collapsed for deployment of the stent, the pattern of folds comprising a unit cell repeated over at least a portion of the sheet, the unit cell comprising: 
 an outer circumferential edge of folds of a first type comprising a pair of longitudinal edge folds extending along the tubular shape of the sheet and transverse edge folds extending around the tubular shape of the sheet;    a central longitudinal fold extending along the tubular shape of the sheet between the transverse edge folds; and    angular folds extending from each intersection of a longitudinal edge fold with a transverse edge fold to the central longitudinal fold,    the stent further comprising a frame extending around the tubular shape of the sheet and reinforcing the sheet, the frame being arranged to be collapsed with the sheet for deployment of the stent.    
   
   
       2 . A stent according to  claim 1 , wherein the frame comprises a plurality of elongate members lying along the sheet and arranged to fold relative to each other in conformity with the sheet to allow the frame to be collapsed with the sheet for deployment of the stent.  
   
   
       3 . A stent according to  claim 2 , wherein the frame is a separate element from the sheet.  
   
   
       4 . A stent according to  claim 3 , wherein the frame is disposed inside the sheet.  
   
   
       5 . A stent according to  claim 3 , wherein the elongate members comprise wire.  
   
   
       6 . A stent according to  claim 3 , wherein the elongate members a respective portions of a piece of sheet material.  
   
   
       7 . A stent according to  claim 2 , wherein the frame is constituted by portions of the sheet having a thickness greater than the thickness of the remainder of the sheet.  
   
   
       8 . A stent according to  claim 2 , wherein the elongate members of the frame extend along respective folds of the pattern of folds of the sheet.  
   
   
       9 . A stent according to  claim 8 , wherein the elongate members of the frame extend along respective folds of said outer circumferential edge of said unit cells.  
   
   
       10 . A stent according to  claim 9 , wherein the elongate members of the frame are arranged in a pattern comprising an array of adjacent loops, each loop extending around at least one of said unit cells.  
   
   
       11 . A stent according to  claim 10 , wherein each loop extends around a plurality of said unit cells.  
   
   
       12 . A stent according to  claim 2 , wherein the elongate members are arranged in a line extending helically around the tubular shape of the sheet.  
   
   
       13 . A stent according to  claim 1 , wherein for each pair of angular folds at opposite longitudinal ends of the unit cell, the pair of angular folds intersect the central longitudinal fold at the same position.  
   
   
       14 . A stent according to  claim 13 , wherein the lengths of: 
 a transverse edge fold from the intersection with a longitudinal edge fold to a central intersection with the central longitudinal fold; and    the portion of the central longitudinal fold from said central intersection with the transverse edge fold to the intersection with the angular folds, are the same.    
   
   
       15 . A stent according to  claim 1 , wherein the angular folds are folds of a second type inverse to said first type and the portions of the central longitudinal fold extending from a respective one of the transverse edge folds to a respective intersection with the angular folds are folds of said first type.  
   
   
       16 . A stent according to  claim 1 , wherein the angular folds all intersect the central longitudinal fold at the same position  
   
   
       17 . A stent according to  claim 1 , wherein said pairs of angular folds intersect the central longitudinal fold at separated positions between which the central longitudinal fold is a fold of said second type.  
   
   
       18 . A stent according to  claim 1 , wherein the angle between a transverse edge fold and an angular fold is 45°.  
   
   
       19 . A stent according to  claim 1 , wherein the angle between a transverse edge fold and an angular fold is less than 45°.  
   
   
       20 . A stent according to  claim 1 , wherein the angle between a transverse edge fold and an angular fold is greater than 45° and less than or equal to 60°.  
   
   
       21 . A stent according to  claim 1 , wherein the unit cell further comprises a ring of folds of said second type each parallel to an adjacent edge fold, the pattern of folds inside the ring of folds of said second type reversing from folds of said first type to folds of said second type and vice versa.  
   
   
       22 . A stent according to  claim 1 , wherein the unit cell is symmetrical about the central longitudinal fold.  
   
   
       23 . A stent according to  claim 1 , wherein the unit cell is symmetrical about an imaginary line extending around the tubular shape of the sheet.  
   
   
       24 . A stent according to  claim 1 , wherein the folds of said first type are hill folds and the folds of said second type are valley folds.  
   
   
       25 . A stent according to  claim 1 , wherein the pattern of folds comprises a single unit cell repeated over the entire sheet.  
   
   
       26 . A stent according to  claim 1 , wherein the pattern of folds comprises a plurality of rows of unit cells extending around the tubular shape of the sheet.  
   
   
       27 . A stent according to  claim 1 , wherein the pattern of folds comprises a plurality of rows of unit cells extending around the tubular shape of the sheet and the unit cells of adjacent rows are offset with the longitudinal edge folds of each row meeting the central longitudinal folds of the adjacent rows.  
   
   
       28 . A stent according to  claim 27 , wherein the longitudinal edge folds of alternate rows and the central longitudinal folds which meet form an uninterrupted fold line progressing helically around the tubular shape of the sheet.  
   
   
       29 . A stent according to  claim 27 , wherein at least two of the rows comprise a respective, different unit cell repeated around the tubular shape of the sheet.  
   
   
       30 . A stent according to  claim 1 , wherein the pattern of folds comprises at least one row of unit cells progressing helically around the tubular shape of the sheet.  
   
   
       31 . A stent according to  claim 30 , wherein the pattern of folds comprises two rows of unit cells each two rows progressing helically around the tubular shape of the sheet.  
   
   
       32 . A stent according to  claim 1 , wherein the tubular shape of the sheet is conical along at least a portion thereof.  
   
   
       33 . A stent according to  claim 1 , wherein at at least some of the nodes where folds intersect the sheet has apertures having a greater width than the width of the folds.  
   
   
       34 . A stent according to  claim 1 , wherein the outer surface of the sheet on the outer side of the tubular shape of the sheet has a higher degree of friction than the inner surface of the sheet on the inner side of the tubular shape of the sheet.  
   
   
       35 . A stent according to  claim 1 , wherein the outer surface of the sheet on the outer side of the sheet is roughened.  
   
   
       36 . A stent according to  claim 1 , wherein the outer surface of the sheet on the outer side of the sheet has a sufficient degree of friction to provide anchorage at an anatomical site.  
   
   
       37 . A stent according to  claim 1 , wherein the sheet has edges joined along the length of the tubular shape of the sheet.  
   
   
       38 . A stent according to  claim 1 , wherein the sheet is continuous around the tubular shape of the sheet.