Radially rigid and longitudinally flexible multi-element intravascular stent

Abstract

A multi-element, vascular stent may be used to maintain or enhance patency of a blood vessel. The stent may be used in peripheral blood vessels, which may be long and/or tortuous. By using multiple, separate stent elements that are balloon expandable, the multi-element stent may be stronger than a traditional self-expanding stent but may also be more flexible, due to its multiple-element configuration, than a traditional balloon-expandable stent. The distance between stent elements may be based on characteristics of the stent and the target vessel location such that the stent elements do not touch one another during skeletal movement. Thus, the multi-element, vascular stent described herein may be particularly advantageous for treating long lesions in tortuous peripheral blood vessels.

What is claimed is: 
     
         1 . A method for manufacturing an intravascular stent comprising:
 loading a multi-element stent comprising multiple individual stent elements onto an inflatable balloon such that the stent elements are positioned serially along a longitudinal length of the balloon and the stent elements do not touch one another, wherein the stent elements are spaced such that after implantation the stent elements do not touch one another at a target vessel location during skeletal movement;   wherein the distance between each stent element is based on a diameter (D) of the stent element in an expanded state at a target vessel location, wherein the distance between each stent element increases with increased D;   wherein the distance between each stent element is further based and an angle (θ) created between stent elements during maximal flexion of the target vessel location during skeletal movement, wherein the distance between each stent element decreases with increased cosθ.   
     
     
         2 . The method of  claim 1 , wherein the distance between each stent element is further based on a length of the stent elements, wherein the distance between each stent element increases with increased length of the stent elements. 
     
     
         3 . The method of  claim 1 , wherein the distance between each stent element is further based on a number of elements in the multi-element stent, wherein the distance between each stent element decreases with increased number of elements in the multi-element stent. 
     
     
         4 . The method of  claim 1 , wherein the distance between each stent element is further based on a maximum percent axial compression of the stent elements at the target vessel location, wherein the distance between each stent element increases with an increase of the maximum percent axial compression of the stent elements at the target vessel location. 
     
     
         5 . The method of  claim 1 , wherein the stent elements are equal in length. 
     
     
         6 . The method of  claim 1 , wherein the multi-element stent is comprised of more than two stent elements, and wherein the distances between each stent element are equal. 
     
     
         7 . The method of  claim 1 , wherein each of the stent elements are separated by a distance of at least half a millimeter while mounted on the balloon and after implantation. 
     
     
         8 . The method of  claim 1 , wherein the stent is formed from a material comprising poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), poly(D,L-lactic acid) (PDLLA), semicrystalline polylactide, polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(iodinated desamino tyrosyl-tyrosine ethyl ester) carbonate, polycaprolactone (PCL), salicylate based polymer, polydioxanone (PDS), poly(hydroxybutyrate), poly(hydroxybutyrate-co-valerate), polyorthoester, polyanhydride, poly(glycolic acid-co-trimethylene carbonate), poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, polyphosphoester, polyphosphoester urethane, poly(amino acids), cyanoacrylates, poly(trimethylene carbonate), poly(iminocarbonate), polyalkylene oxalates, polyphosphazenes, polyiminocarbonates, and aliphatic polycarbonates, fibrin, fibrinogen, cellulose, starch, collagen, polyurethane including polycarbonate urethanes, polyethylene, polyethylene terephthalate, ethylene vinyl acetate, ethylene vinyl alcohol, silicone including polysiloxanes and substituted polysiloxanes, polyethylene oxide, polybutylene terephthalate-co-PEG, PCL-co-PEG, PLA-co-PEG, PLLA-co-PCL, polyacrylates, polyvinyl pyrrolidone, polyacrylamide, or combinations thereof. 
     
     
         9 . The method of  claim 8 , wherein the material is extruded into a cylindrical tubing. 
     
     
         10 . The method of  claim 1 , wherein the stent elements are coated with an anti-proliferative agent. 
     
     
         11 . The method of  claim 1 , wherein the stent elements comprise a plurality of diamond shaped closed cells longer in a longitudinal direction than in a radial direction when in an unexpanded state. 
     
     
         12 . The method of  claim 1 , wherein the stent elements comprise a plurality of diamond shaped closed cells longer in a radial direction than in a longitudinal direction in the expanded state. 
     
     
         13 . The method of  claim 1 , wherein the distance between each stent element in an unexpanded state is less than or equal to the distance between each stent element in the expanded state. 
     
     
         14 . A device for placement within a blood vessel to maintain or enhance blood flow through the blood vessel, the device comprising:
 multiple, balloon-expandable, stent elements configured to be implanted in the blood vessel as a multi-element stent;   wherein the stent elements are positioned serially along a longitudinal length of a balloon and the stent elements do not touch one another in an unexpanded state;   wherein the stent elements are spaced such that after implantation the stent elements do not touch one another at a target vessel location during skeletal movement;   wherein a distance between each stent element is greater than or equal to                     D   2       2     (   1   −   cos   θ   )         ​         ​   ​               ,         
wherein D is a diameter of the stent element in an expanded state at a target vessel location and θ is an angle created between stent elements during maximal flexion of the target vessel location during skeletal movement. 
     
     
         15 . The device of  claim 14 , wherein the stent elements are equal in length. 
     
     
         16 . The device of  claim 14 , wherein the multi-element stent is comprised of more than two stent elements, and wherein the distances between each stent element are equal. 
     
     
         17 . The device of  claim 14 , wherein each of the stent elements are separated by a distance of at least half a millimeter while mounted on the balloon and after implantation.