Crosslinking of polyethylene for low wear using radiation and thermal treatments

Abstract

The present invention discloses methods for enhancing the wear-resistance of polymers, the resulting polymers, and in vivo implants made from such polymers. One aspect of this invention presents a method whereby a polymer is irradiated, preferably with gamma radiation, then thermally treated, such as by remelting of annealing. The resulting polymeric composition preferably has its most oxidized surface layer removed. Another aspect of the invention presents a general method for optimizing the wear resistance and desirable physical and/or chemical properties of a polymer by crosslinking and thermally treating it. The resulting polymeric compositions is wear-resistant and may be fabricated into an in vivo implant.

1 . A preformed polymeric composition comprising a crosslinked thermally treated polymer. 
     
     
         2 . An implantable bearing component made by the process comprising the steps of:
 (a) crosslinking, by irradiation, a preformed polymer without melting it;   (b) subsequently melting the crosslinked polymer at atmospheric pressure; and   (c) fashioning the implantable bearing component from the crosslinked and melted polymer, wherein the polymer is selected from the group consisting of: ultra high molecular weight polyethylene (UHMWPE) and high molecular weight polyethylene (HMWPE).   
     
     
         3 . The implantable bearing component of  claim 2 , wherein the polymer is crosslinked by gamma radiation at a dose of from about 1 to about 100 Mrad. 
     
     
         4 . The implantable bearing component of  claim 3 , wherein the gamma radiation dose is from about 4 to about 15 Mrad. 
     
     
         5 . The implantable bearing component of  claim 4 , wherein the gamma radiation dose is from about 4.5 to about 10 Mrad. 
     
     
         6 . The implantable bearing component of  claim 4 , wherein the implantable bearing component is for use in a joint prosthesis. 
     
     
         7 . The implantable bearing component of  claim 6 , wherein the joint prosthesis is selected from the group consisting of hip, knee, ankle, elbow, jaw, shoulder, finger and spine joint prostheses. 
     
     
         8 . The implantable bearing component of  claim 7 , wherein the joint prosthesis is selected from the group consisting of: hip and knee joint prostheses. 
     
     
         9 . The implantable bearing component of  claim 4 , wherein the implantable bearing component is selected from the group consisting of: an acetabular cup and a liner of an acetabular cup. 
     
     
         10 . A joint prosthesis comprising:
 a first member that can be secured to a first bone constituting a first portion of a joint;   an articulating surface on the first member;   a second member that can be secured to a second bone constituting a second portion of the joint; and   the implantable bearing component of  claim 4 , said implantable bearing component can be disposed between the second member and the articulating surface, said implantable bearing component can receive said articulating surface for movement therein.   
     
     
         11 . The joint prosthesis of  claim 10 , wherein the joint prosthesis is selected from the group consisting of: hip, knee, ankle, elbow, jaw, shoulder, finger and spine joint prostheses. 
     
     
         12 . The joint prosthesis of  claim 11 , wherein the joint prosthesis is selected from the group consisting of: hip and knee joint prostheses. 
     
     
         13 . The joint prosthesis of  claim 10 , wherein the joint prosthesis 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 prosthetic stem;   (d) the second member is a prosthetic acetabular shell;   (e) the articulating surface is a prosthetic femoral ball; and   (f) the implantable bearing component is an acetabular cup liner.   
     
     
         14 . The joint prosthesis of  claim 10 , wherein said articulating surface and said first member are separate units. 
     
     
         15 . A joint prosthesis comprising:
 a first member that can be secured to a first bone constituting a first portion of the joint;   an articulating surface on the first member;   the implantable bearing component of  claim 4  that can be secured to a second bone constituting a second portion of the joint, said implantable bearing component can receive said articulating surface for movement therein.   
     
     
         16 . The joint prosthesis of  claim 15 , wherein the joint prosthesis is selected from the group consisting of: hip, knee, ankle, elbow, jaw, shoulder, finger and spine joint prostheses. 
     
     
         17 . The joint prosthesis of  claim 16 , wherein the joint prosthesis is selected from the group consisting of: hip and knee joint prostheses. 
     
     
         18 . The joint prosthesis of  claim 15 , wherein the joint prosthesis 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 prosthetic stem;   (d) the implantable bearing component is a prosthetic acetabular cup; and   (e) the articulating surface is a prosthetic femoral ball.   
     
     
         19 . The joint prosthesis of  claim 15 , wherein said articulating surface and said first member are separate units. 
     
     
         20 . The joint prosthesis of  claim 13 , wherein said prosthetic femoral ball and said prosthetic stem are separate units. 
     
     
         21 - 98 . (canceled)