Medical implant or medical implant part and method for producing the same

Abstract

The invention provides a medical implant or medical implant part comprising a body and a surface layer, wherein the surface layer comprises a mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene having a weight average molecular weight of about 400,000 atomic mass units or more. The invention also provides a method for producing such a medical implant or medical implant.

1 . A method for producing a medical implant or medical implant part comprising a body and a surface layer, the method comprising the steps of: 
 (a) providing a compression mold for the medical implant or medical implant part having an internal volume,    (b) providing a matrix of ultrahigh molecular weight polyethylene, wherein the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 400,000 atomic mass units or more,    (c) dispersing at least one hydrophilic polymer in the matrix of ultrahigh molecular weight polyethylene to produce a mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene,    (d) filling at least a portion of the internal volume of the compression mold with the mixture obtained in step (c), (e) compressing the mixture contained within the compression mold for a time and under conditions sufficient to form a medical implant or medical implant part therefrom, and    (f) removing the medical implant or medical implant part from the compression mold.    
     
     
         2 . The method of  claim 1 , wherein the portion of the internal volume of the compression mold filled with the mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene comprises a portion of the surface layer of the medical implant or medical implant part, and the surface layer corresponds to an articulating surface of the medical implant or medical implant part.  
     
     
         3 . The method of  claim 2 , wherein the surface layer has a thickness of about 1 mm or more.  
     
     
         4 . The method of  claim 3 , wherein the portion of the internal volume of the compression mold corresponding to the body of the medical implant or medical implant part is filled with ultrahigh molecular weight polyethylene.  
     
     
         5 . The method of  claim 1 , wherein substantially all of the internal volume of the compression mold is filled with the mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene.  
     
     
         6 . The method of  claim 1 , wherein the method further comprises: 
 (g) irradiating at least a portion of the mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene for a time and under conditions sufficient to cross-link at least a portion of the hydrophilic polymer and ultrahigh molecular weight polyethylene contained therein.    
     
     
         7 . The method of  claim 6 , wherein the method further comprises: 
 (h) quenching a substantial portion of free radicals generated in the mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene during the irradiation of the mixture in step (g).    
     
     
         8 . The method of  claim 7 , wherein the method further comprises: 
 (i) sterilizing the medical implant or medical implant part using a non-irradiative process, and    (j) packaging the medical implant or medical implant part.    
     
     
         9 . The method of  claim 1 , wherein the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 1,000,000 atomic mass units or more.  
     
     
         10 . The method of  claim 1 , wherein the hydrophilic polymer is a water-soluble, biocompatible polymer.  
     
     
         11 . The method of  claim 10 , wherein the hydrophilic polymer is a water-soluble, biocompatible polymer selected from the group consisting of poly(ethylene oxide), polyvinylpyrrolidone, poly(vinyl alcohol), mixtures thereof, and copolymers thereof.  
     
     
         12 . The method of  claim 11 , wherein the hydrophilic polymer comprises about 0.1 to about 25 wt. % of the mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene.  
     
     
         13 . A medical implant or medical implant part comprising a body and a surface layer, wherein the surface layer is formed from a mixture comprising at least one hydrophilic polymer and an ultrahigh molecular weight polyethylene having a weight average molecular weight of about 400,000 atomic mass units or more, wherein the hydrophilic polymer is distributed as a discontinuous phase in a continuous phase of the ultrahigh molecular weight polyethylene.