Stent to be implanted in human body and method of producing stent

Abstract

A stent, to be implanted in a human body, is made of a super-elastic metal which is formed approximately cylindrically and integrally and which shows super-elasticity before and after said stent is inserted into said human body. The stent has a plurality of annular parts (expansion element) deformable in a direction in which an outer diameter thereof contracts, when a stress is applied thereto and a plurality of connection parts (connection element) each connecting said adjacent annular parts to each other, with said annular parts arranged in an axial direction of said stent. Each of said annular parts is elastically deformable owing to super-elasticity thereof, whereas each of said connection parts is substantially a plastically deformable part not super-elastic entirely or partly.

What is claimed is:  
     
         1 . A stent, to be implanted in a human body, made of a super-elastic metal which is formed approximately cylindrically and integrally and which shows super-elasticity before and after said stent is inserted into said human body; 
 said stent having a plurality of annular parts deformable in a direction in which an outer diameter thereof contracts, when a stress is applied thereto and a plurality of connection parts each connecting said adjacent annular parts to each other, with said annular parts arranged in an axial direction of said stent,    wherein each of said annular parts is elastically deformable owing to super-elasticity thereof, whereas said connection part is substantially a plastically deformable part not super-elastic entirely or partly or a normal elastically deformable part not super-elastic entirely or partly.    
     
     
         2 . A stent according to  claim 1 , wherein said annular part is composed of a wavy linear material.  
     
     
         3 . A stent according to  claim 1 , wherein said annular part is composed of a linear constituent having a plurality of notches and a plurality of openings formed on a side surface thereof.  
     
     
         4 . A stent according to  claim 1 , wherein said connection part is curved or bent.  
     
     
         5 . A stent according to  claim 1 , wherein said connection part is curved or bent in a direction approximately orthogonal to an axial direction of said stent.  
     
     
         6 . A stent according to  claim 1 , wherein said stent has two or more connection parts between said annular parts adjacent to each other.  
     
     
         7 . A stent according to  claim 1 , wherein said connection part is substantially straight.  
     
     
         8 . A stent according to  claim 7 , wherein said connection part is substantially parallel with an axial direction of said stent.  
     
     
         9 . A stent according to  claim 7 , wherein said connection part is oblique to an axis of stent by a predetermined angle.  
     
     
         10 . A method of producing a stent to be implanted in a human body, comprising the steps of: 
 forming a base material for said stent having a plurality of annular parts deformable in a direction in which an outer diameter thereof contracts, when a stress is applied thereto and a plurality of connection parts each connecting said adjacent annular parts to each other, with said annular parts arranged in an axial direction of said stent, by partly removing a side surface of a prepared approximately cylindrical pipe, made of a super-elastic metal, having an outer diameter suitable for a portion of the human body in which said stent is implanted; and    heat-treating a part or an entirety of said connection part of said base material for said stent to substantially eliminate super-elasticity of said connection part and impart plastic deformability or normal elasticity thereto.    
     
     
         11 . A method according to  claim 10 , wherein said heat-treating step is performed by heat generation caused by a resistance of said connection part owing to energization of both ends of said connection part.  
     
     
         12 . A method according to  claim 10 , wherein said heat treatment is performed by laser beams emitted to said connection part.  
     
     
         13 . A method of producing a stent to be implanted in a human body, comprising the steps of: 
 forming a base material for said stent having a plurality of annular parts and a plurality of connection parts each connecting said adjacent annular parts to each other, with said annular parts arranged in an axial direction of said stent by preparing an approximately cylindrical metal pipe having an outer diameter smaller than an inner diameter of a portion in which said stent is implanted and having super-elasticity or a shape memory characteristic or to which said super-elasticity or said shape memory characteristic can be imparted and by partly removing a side surface of said pipe;    forming an expanded mode of said base material for said stent by expanding said base material for said stent so that an outer diameter thereof becomes suitable for said portion in which said stent is implanted and by heat-setting said base material for said stent in an expanded state to store a configuration of said expanded base material for said stent and allow said super-elasticity to appear; and    heat-treating said expanded base material for said stent by heating an entirety or a portion of said connection part to eliminate super-elasticity thereof substantially and impart plastic deformability or normal elasticity thereto.    
     
     
         14 . A method according to  claim 13 , wherein said heat-treating step is performed by disposing said expanded base material for said stent on a heat sink on which said expanded base material for said stent can be mounted and which has a plurality of concavities, with each annular part of said base material for said stent in contact with an outer surface of said heat sink and with said connection parts, an entirety of a portion thereof or a portion thereof disposed over said concavities of said heat sink and not in contact with said outer surface of the heat sink and by energizing said entire base material for said stent so that said base material for said stent self-heats and said annular part in contact with said outer surface of said heat sink radiates heat.  
     
     
         15 . A method according to  claim 7 , wherein said heat-treating step is performed by disposing said base material for said stent on a heat sink on which said base material for said stent can be mounted and which has a plurality of concavities, with each annular part of said base material for said stent in contact with an outer surface of said heat sink and with connection parts, an entirety of a portion thereof or a portion thereof disposed over said concavities of said heat sink and not in contact with said outer surface of said heat sink and by energizing said entire base material for said stent so that said base material for said stent self-heats and said annular part in contact with said outer surface of said heat sink radiates heat.