Chemically crosslinked ultrahigh molecular weight polyethylene for artificial human joints

Abstract

The present invention discloses a method for enhancing the wear-resistance of polymers by crosslinking them, especially before irradiation sterilization. In particular, this invention presents the use of chemically crosslinked ultrahigh molecular weight polyethylene in in vivo implants.

1 - 48 . (canceled).  
     
     
         49 . A medical implant for use within a body, said implant being formed of a crosslinked ultrahigh molecular weight polyethylene having a polymeric structure of 51% crystallinity or less, so as to increase wear resistance of said implant within the body.  
     
     
         50 - 110 . (canceled).  
     
     
         111 . A medical implant comprising: 
 a first member adapted to be secured to a first bone constituting a first portion of a joint;    an articulating surface on the first member;    a second member adapted to be secured to a second bone constituting a second portion of the joint; and    a bearing component adapted for disposition between the second member and the articulating surface, said bearing component being adapted to receive said articulating surface for movement therein, the bearing component being made of crosslinked ultrahigh molecular weight polyethylene characterized by a polymeric structure of about 3.4 degrees of swelling or less.    
     
     
         112  The medical implant of  claim 111 , wherein crosslinking is achieved according to the method selected from the group consisting of: chemically crosslinking a polyethylene, irradiation crosslinking a polyethylene, and photocrosslinking a polyethylene.  
     
     
         113 . The medical implant of  claim 112 , wherein said medical implant is further irradiated in the solid state for sterilization.  
     
     
         114 . The medical implant of  claim 113 , wherein said medical implant is irradiated in air at a sterilization dose.  
     
     
         115 . The medical implant of  claim 112 , wherein said crosslinked ultrahigh molecular weight polyethylene is further characterized by its lack of shrinkage.  
     
     
         116 . The medical implant of  claim 111 , wherein said crosslinked ultrahigh molecular weight polyethylene is further characterized by a polymeric structure of about at least 97% gel.  
     
     
         117 . The medical implant of  claim 111 , wherein the medical implant is a prosthesis selected from the group consisting of: hip, knee, ankle, elbow, jaw, shoulder, finger and spine prostheses.  
     
     
         118 . The medical implant of  claim 117 , wherein the medical implant is a hip or knee prosthesis.  
     
     
         119 . The medical implant of  claim 114 , wherein said crosslinked ultrahigh molecular weight polyethylene has about 45% crystallinity or less as measured by differential scanning calorimetry.  
     
     
         120 . The medical implant of  claim 111 , wherein said ultrahigh molecular weight polyethylene is further characterized by a smoother fracture surface, decreased tensile strength at break point, and decreased Young's modulus compared to a corresponding uncrosslinked ultrahigh molecular weight polyethylene.  
     
     
         121 . The medical implant of  claim 111 , wherein the medical implant is for use in a hip joint replacement, wherein: 
 (a) the first bone is a femur,    (b) the second bone is a pelvic bone,    (c) the first member is a stem,    (d) the second member is an acetabular shell;    (e) the articulating surface is a femoral head; and    (f) the bearing component is an acetabular cup liner.    
     
     
         122 . The medical implant of  claim 121 , wherein said medical implant is irradiated in air at a sterilization dose and said irradiated crosslinked ultrahigh molecular weight polyethylene has about 45% crystallinity or less, and the crystallinity is measured by differential scanning calorimetry.  
     
     
         123 . A medical implant comprising: 
 a first member adapted to be secured to a first bone constituting a first portion of a joint;    an articulating surface on the first member;    a second member adapted to be secured to a second bone constituting a second portion of the joint; and    a bearing component adapted for disposition between the second member and the articulating surface, said bearing component being adapted to receive said articulating surface for movement therein, the bearing component being made of crosslinked ultrahigh molecular weight polyethylene characterized by a polymeric structure of at least about 97% gel content.    
     
     
         124 . The medical implant of  claim 123 , wherein crosslinking is achieved according to the method selected from the group consisting of: chemically crosslinking a polyethylene, irradiation crosslinking a polyethylene, and photocrosslinking a polyethylene.  
     
     
         125 . The medical implant of  claim 124 , wherein said implant is further irradiated in the solid state for sterilization.  
     
     
         126 . The medical implant of  claim 125 , wherein said implant is irradiated in air at a sterilization dose.  
     
     
         127 . The medical implant of  claim 124 , wherein said crosslinked ultrahigh molecular weight polyethylene is further characterized by its lack of shrinkage.  
     
     
         128 . The medical implant of  claim 123 , wherein the medical implant is a prosthesis selected from the group consisting of: hip, knee, ankle, elbow, jaw, shoulder, finger and spine prostheses.  
     
     
         129 . The medical implant of  claim 123 , wherein said implant is for use in a hip or knee joint replacement.  
     
     
         130 . The medical implant of  claim 126 , wherein said ultrahigh molecular weight polyethylene has about 45% crystallinity or less as measured by differential scanning calorimetry.  
     
     
         131 . The medical implant of  claim 123 , wherein said ultrahigh molecular weight polyethylene is further characterized by a smoother fracture surface, decreased tensile strength at break point, and decreased Young's modulus compared to a corresponding uncrosslinked ultrahigh molecular weight polyethylene.  
     
     
         132 . The medical implant of  claim 123 , wherein the medical implant is for use in a hip joint replacement, wherein: 
 (a) the first bone is a femur;    (b) the second bone is a pelvic bone;    (c) the first member is a stem;    (d) the second member is an acetabular shell;    (e) the articulating surface is a femoral head; and    (f) the bearing component is an acetabular cup liner.    
     
     
         133 . The medical implant of  claim 132 , wherein said medical implant is irradiated in air at a sterilization dose and said irradiated ultrahigh molecular weight polyethylene has about 45% crystallinity or less, and the crystallinity is measured by differential scanning calorimetry.  
     
     
         134 . A hip joint prosthesis comprising: 
 (a) a prosthetic stem adapted at its first end to be secured to a femur constituting a first portion of the joint;    (b) a prosthetic femoral head at a second end of the prosthetic stem;    (c) a prosthetic acetabular shell adapted to be secured to a pelvic bone constituting a second portion of the joint; and    (d) a prosthetic acetabular liner adapted for disposition between the prosthetic acetabular shell and the prosthetic femoral head, said prosthetic acetabular liner being adapted to receive said prosthetic femoral head for movement therein, said prosthetic acetabular liner being made of crosslinked ultrahigh molecular weight polyethylene characterized by a polymeric structure of about 3.4 degrees of swelling or less and about at least 97% gel content.    
     
     
         135 . A medical implant comprising: 
 a first member adapted to be secured to a first bone constituting a first portion of the joint;    an articulating surface on the first member;    a second member adapted to be secured to a second bone constituting a second portion of the joint, said second member being adapted to receive said articulating surface for movement therein, and said second member being made of crosslinked ultrahigh molecular weight polyethylene characterized by at least one of the following:    (a) a polymeric structure of about 3.4 degrees of swelling or less; and    (b) a polymeric structure of about at least 97% gel content.    
     
     
         136 . The medical implant of  claim 135 , wherein crosslinking is achieved according to the method selected from the group consisting of: chemically crosslinking a polyethylene, irradiation crosslinking a polyethylene, and photocrosslinking a polyethylene.  
     
     
         137 . The medical implant of  claim 135 , wherein the medical implant is a prosthesis selected from the group consisting of: hip, knee, ankle, elbow, jaw, shoulder, finger and spine prostheses.  
     
     
         138 . The medical implant of  claim 135 , wherein the implant is a hip prosthesis and: 
 (a) the first bone is a femur;    (b) the second bone is a pelvic bone;    (c) the first member is a stem;    (d) the second member is an acetabular cup; and    (e) the articulating surface is a femoral head.    
     
     
         139 . The medical implant of  claim 111 , wherein said articulating surface and said first member are separate units.  
     
     
         140 . The medical implant of  claim 123 , wherein said articulating surface and said first member are separate units.  
     
     
         141 . The medical implant of  claim 134 , wherein said prosthetic femoral head and said prosthetic stem are separate units.  
     
     
         142 . The medical implant of  claim 135 , wherein said articulating surface and said first member are separate units.  
     
     
         143 . The medical implant of  claim 121 , wherein said femoral head and said stem are separate units.  
     
     
         144 . The medical implant of  claim 132 , wherein said femoral head and said stem are separate units.  
     
     
         145 . The medical implant of  claim 138 , wherein said femoral head and said stem are separate units.