Method of Making a Polymeric Stent

Abstract

An endoprosthesis is made by radially expanding and axially extending a polymer tube. Next, portions of the polymer tube are removed to form an open framework of struts that define a tubular body. The tubular body has an end segment and an intermediate segment adjoining the end segment. The end segment includes a circumferential series of closed cells having a first W-shape closed cell. The intermediate segment includes a circumferential series of closed cells having a second W-shape closed cell. There are linear link struts at opposite ends of the individual first and second W-shape closed cells. The linear link struts of the first W-shape closed cell are longer than linear link struts of the second W-shape closed cell.

What is claimed is: 
     
         1 . A method of making an endoprosthesis, the method comprising:
 radially expanding and axially extending a polymer tube; and followed by   removing portions of the polymer tube to form an open framework of struts defining a tubular body having an end segment and an intermediate segment adjoining the end segment, the end segment including a circumferential series of closed cells having a first W-shape closed cell, the intermediate segment including a circumferential series of closed cells having a second W-shape closed cell, there being linear link struts at opposite ends of the individual first and second W-shape closed cells, the linear link struts of the first W-shape closed cell being longer than linear link struts of the second W-shape closed cell.   
     
     
         2 . The method of  claim 1 , wherein the radially expanding and the axially extending of the polymer tube includes blow molding the polymer tube. 
     
     
         3 . The method of  claim 1 , wherein removing of portions of the polymer tube includes any of chemical etching, mechanical cutting, and laser cutting material away from the polymer tube. 
     
     
         4 . The method of  claim 1 , further comprising, before radially expanding the polymer tube, forming the polymer tube by conveying a polymer melt through an extruder. 
     
     
         5 . The method of  claim 4 , wherein the polymer melt is molten poly(L-lactide). 
     
     
         6 . The method of  claim 1 , wherein the polymer tube is made of poly(L-lactide). 
     
     
         7 . The method of  claim 1 , wherein each of the first and second W-shape closed cells has a perimeter that includes one of the linear link struts, followed by and joined directly to a series of four ring struts, followed by and joined directly to another one of the linear link struts, and wherein the series of four ring struts forms a W-shape. 
     
     
         8 . The method of  claim 1 , wherein each of the first and second W-shape closed cells has a perimeter that includes a first series of four ring struts, followed by and joined directly to one of the linear link struts, followed by and joined directly to a second series of four ring struts, and followed by and joined directly to another one of the linear link struts. 
     
     
         9 . The method of  claim 8 , wherein in each one of the perimeters:
 the four ring struts of the first series are joined to each other by three hinge elements,   the four ring struts of the second series are joined to each other by three hinge elements, and   each of the linear link struts is joined by a hinge element directly to the first series of ring struts and joined by a hinge element directly to the second series of ring struts.   
     
     
         10 . The method of  claim 1 , wherein one of the linear link struts within the end segment is a marker strut that includes one or more holes. 
     
     
         11 . The method of  claim 10 , wherein a closed cell immediately adjacent to one side of the marker strut is a mirror image or is substantially a mirror image of a closed cell immediately adjacent to the opposite side of the marker strut. 
     
     
         12 . The method of  claim 10 , wherein a first cell from among the closed cells of the end segment includes a first crest at one end of the marker strut and a second crest circumferentially adjacent the first crest, the first crest having an axial position that is axially spaced apart from the axial position of the second crest. 
     
     
         13 . The method of  claim 12 , wherein the first cell includes a third crest circumferentially adjacent the second crest, the second crest is located between the first and third crests, and the first and third crests have axial positions that coincide. 
     
     
         14 . The method of  claim 1 , wherein the closed cells of the end segment are bounded by a first ring and a second ring, the first ring located at a proximal end or a distal end of the tubular body, wherein the first ring includes a first trough and the second ring includes a second trough located axially across the first trough, the first trough having a circumferential position that is circumferentially spaced apart from the circumferential position of the second trough. 
     
     
         15 . The method of  claim 14 , wherein the end segment is a distal end segment, the tubular body further includes a proximal end segment, the closed cells of the proximal end segment are bounded by a first proximal ring and a second proximal ring, the first proximal ring is located at a proximal end of the tubular body, the first proximal ring includes a plurality of crests that have axial positions that coincide, the second proximal ring includes a plurality of crests that have axial positions that coincide, the first proximal ring includes a first trough and the second ring includes a second trough that is located axially across from and has an axial position that coincides with that of the first trough of the first proximal ring.