Medical implant or medical implant part comprising porous UHMWPE and process for producing the same

Abstract

The invention provides a medical implant or medical implant part comprising porous ultrahigh molecular weight polyethylene having a weight average molecular weight of about 400,000 atomic mass units or more and a porosity of about 15% to about 65%. The invention further provides a process for producing a medical implant or medical implant part.

1 . A medical implant or medical implant part comprising porous ultrahigh molecular weight polyethylene, wherein (i) the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 400,000 atomic mass units or more, (ii) the ultrahigh molecular weight polyethylene has a porosity of about 20% or more, (iii) the average diameter of the pores in the ultrahigh molecular weight polyethylene is about 400 μm or less, and (iv) at least some of the ultrahigh molecular weight polyethylene comprises hydrophilic functional groups attached thereto.  
     
     
         2 . The medical implant or medical implant part 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.  
     
     
         3 . The medical implant or medical implant part of  claim 1 , wherein the hydrophilic functional groups comprise one or more functional groups selected from the group consisting of amino functional groups, carboxylic acid functional groups, hydroxyl functional groups, hydroxysulfuryl functional groups, and combinations thereof.  
     
     
         4 . The medical implant or medical implant part of  claim 3 , wherein the hydrophilic functional groups comprise one or more carboxylic acid functional groups.  
     
     
         5 . The medical implant or medical implant part of  claim 1 , wherein the hydrophilic functional groups are attached to the surface of the ultrahigh molecular weight polyethylene through hydrophilic monomers.  
     
     
         6 . A medical implant or medical implant part comprising porous ultrahigh molecular weight polyethylene, wherein (i) the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 400,000 atomic mass units or more, (ii) the ultrahigh molecular weight polyethylene has a porosity of about 15% to about 65%, and (iii) at least about 5% (by volume) of the pores in the ultrahigh molecular weight polyethylene have a diameter of about 200 μm or more.  
     
     
         7 . The medical implant or medical implant part of  claim 6 , wherein the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 1,000,000 atomic mass units or more.  
     
     
         8 . The medical implant or medical implant part of  claim 6 , wherein the ultrahigh molecular weight polyethylene has a porosity of about 20% to about 60%.  
     
     
         9 . The medical implant or medical implant part of  claim 6 , wherein about 5% or more (by number) of the pores in the ultrahigh molecular weight polyethylene have a diameter of about 200 μm or more.  
     
     
         10 . The medical implant or medical implant part of  claim 6 , wherein the average diameter of the pores in the ultrahigh molecular weight polyethylene is about 400 μm or less.  
     
     
         11 . The medical implant or medical implant part of  claim 6 , wherein at least some of the ultrahigh molecular weight polyethylene comprises hydrophilic functional groups attached thereto.  
     
     
         12 . The medical implant or medical implant part of  claim 11 , wherein the hydrophilic functional groups comprise one or more functional groups selected from the group consisting of amino functional groups, carboxylic acid functional groups, hydroxyl functional groups, hydroxysulfuryl functional groups, and combinations thereof.  
     
     
         13 . The medical implant or medical implant part of  claim 12 , wherein the hydrophilic functional groups comprise one or more carboxylic acid functional groups.  
     
     
         14 . The medical implant or medical implant part of  claim 11 , wherein the hydrophilic functional groups are attached to the ultrahigh molecular weight polyethylene through hydrophilic monomers.  
     
     
         15 . The medical implant or medical implant part of  claim 14 , wherein the hydrophilic monomer is selected from the group consisting of acrylic acid, poly(ethylene glycol), 2-hydroxyethyl methacrylate, and combinations thereof.  
     
     
         16 . A process for producing a medical implant or medical implant part comprising porous ultrahigh molecular weight polyethylene, the process comprising: 
 (a) providing a compression mold for the medical implant or medical implant part having an internal volume,    (b) providing a matrix comprising 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 a porogen comprising a melt-processable polymer in the matrix to produce a mixture comprising at least one porogen 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,    (f) removing the medical implant or medical implant part from the compression mold, and    (g) immersing the medical implant or medical implant part obtained in step (f) in a solvent for a time and under conditions sufficient to extract at least a portion of the porogen from the medical implant or medical implant part.    
     
     
         17 . The process of  claim 16 , wherein the ultrahigh molecular weight polyethylene has a weight average molecular weight of about 1,000,000 atomic mass units or more.  
     
     
         18 . The process of  claim 16 , wherein the melt-processable polymer has a melt index of about 5 g/10 min or less.  
     
     
         19 . The process of  claim 16 , wherein the melt-processable polymer is selected from the group consisting of polyethylene glycol, poly(ethylene oxide), polyvinylpyrrolidone, poly(vinyl alcohol), and mixtures thereof.  
     
     
         20 . The process of  claim 16 , wherein the porogen further comprises a water-soluble salt.  
     
     
         21 . The process of  claim 16 , wherein the process further comprises: 
 (h) modifying at least a portion of the ultrahigh molecular weight polyethylene contained within the medical implant or medical implant part to make the ultrahigh molecular weight polyethylene hydrophilic after the completion of step (g).    
     
     
         22 . The process of  claim 21 , wherein the ultrahigh molecular weight polyethylene is modified by introducing hydrophilic functional groups onto at least a portion of the surface of the ultrahigh molecular weight polyethylene.  
     
     
         23 . The process of  claim 22 , wherein the hydrophilic functional groups comprise one or more functional groups selected from the group consisting of amino functional groups, carboxylic acid functional groups, hydroxyl functional groups, hydroxysulfuryl functional groups, and combinations thereof.  
     
     
         24 . The process of  claim 23 , wherein the hydrophilic functional groups comprise one or more carboxylic acid functional groups.  
     
     
         25 . The process of  claim 22 , wherein the hydrophilic functional groups are introduced onto the surface of the ultrahigh molecular weight polyethylene by grafting hydrophilic monomers onto at least a portion of the surface of the ultrahigh molecular weight polyethylene.