Orthopaedic polymer-on-polymer bearings

Abstract

The invention is a prosthetic joint, for example knee joint, including a first joint component which is preferably polyetheretherketone containing barium sulphate and a second joint component which is preferably a polyolefin.

What is claimed is: 
     
         1 . An orthopaedic prosthetic joint comprising a joint couple comprising:
 (a) a first joint component having a first bearing surface comprising a first material which comprises a first polymer;   (b) a second joint component having a second bearing surface comprising a second material which comprises a second polymer;   wherein said first and second bearing surfaces are in sliding engagement with one another;   wherein said first polymer is harder than said second polymer;   wherein said first material includes barium sulphate.   
     
     
         2 . A joint according to  claim 1 , wherein said first material is a polyacetal or a polyaryletherketone and said second material is a polyolefin, a polyurethane or a polyamide. 
     
     
         3 . An orthopaedic prosthetic joint comprising a joint couple comprising:
 (a) a first joint component having a first bearing surface made of a first polymer; and   (b) a second joint component having a second bearing surface made of a second polymer;   wherein said first and second bearing surfaces are in sliding engagement with one another;   wherein said first bearing surface is made of a first material which is harder than a second material from which the second joint surface is made;   wherein said first material comprise a polyaryletherketone and barium sulphate.   
     
     
         4 . A joint according to  claim 1 , wherein said barium sulphate has a D 10  particle size in the range 0.1 to 1.0 μm. 
     
     
         5 . A joint according to  claim 1 , wherein the ratio of the wt % of barium sulphate to the wt % of said first polymer is greater than 0.04 and is less than 0.4. 
     
     
         6 . A joint according to  claim 1 , wherein said first bearing surface includes at least 1 wt % barium sulphate and includes 30 wt % or less of barium sulphate. 
     
     
         7 . A joint according to  claim 1 , wherein said polyaryletherketone has a repeat unit of formula (I) 
       
         
           
           
               
               
           
         
       
       where t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2. 
     
     
         8 . A joint according to  claim 1 , wherein said polyaryletherketone has a melt viscosity (MV) of at least 0.35 kNsm −2 . 
     
     
         9 . A joint according to  claim 1 , wherein said polyaryletherketone has a crystallinity of greater than 25%. 
     
     
         10 . A joint according to  claim 1 , wherein said second material is selected from a polyethylene, a polyurethane, a polyamide and a composite of these polymers. 
     
     
         11 . A joint according to  claim 1 , wherein said first joint component consists essentially of polyetheretherketone and barium sulphate; and at least 80 wt % of said second joint component is made up of said second polymer. 
     
     
         12 . A joint according to  claim 1 , wherein said second material comprises at least 60 wt % of a polymeric material selected from polyethylene, a polyurethane and a polyamide. 
     
     
         13 . A joint according to  claim 12 , wherein said second material comprises a polyethylene. 
     
     
         14 . A joint according to  claim 1 , which is a knee joint. 
     
     
         15 . A method of making an orthopaedic prosthetic joint according to any preceding claim, the method comprising a moulding step and optional machining step to make the first joint component; and a moulding step and optional machining step to make the second joint component. 
     
     
         16 . The use of a first joint component according to  claim 1 , and a second joint component in the manufacture of an orthopaedic prosthetic joint which comprises said first and second joint components bearing against one another for implantation into the human body, for example to replace a structural element of the body. 
     
     
         17 . A joint according to  claim 3 , wherein said barium sulphate has a D 10  particle size in the range 0.1 to 1.0 μm. 
     
     
         18 . A joint according to  claim 3 , wherein the ratio of the wt % of barium sulphate to the wt % of said first polymer is greater than 0.04 and is less than 0.4. 
     
     
         19 . A joint according to  claim 3 , wherein said first bearing surface includes at least 1 wt % barium sulphate and includes 30 wt % or less of barium sulphate. 
     
     
         20 . A joint according to  claim 3 , wherein said polyaryletherketone has a repeat unit of formula (I) 
       
         
           
           
               
               
           
         
       
       where t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2. 
     
     
         21 . A joint according to  claim 3 , wherein said polyaryletherketone has a melt viscosity (MV) of at least 0.35 kNsm −2 . 
     
     
         22 . A joint according to  claim 3 , wherein said polyaryletherketone has a crystallinity of greater than 25%. 
     
     
         23 . A joint according to  claim 3 , wherein said second material is selected from a polyethylene, a polyurethane, a polyamide and a composite of these polymers. 
     
     
         24 . A joint according to  claim 3 , wherein said first joint component consists essentially of polyetheretherketone and barium sulphate; and at least 80 wt % of said second joint component is made up of said second polymer. 
     
     
         25 . A joint according to  claim 3 , wherein said second material comprises at least 60 wt % of a polymeric material selected from polyethylene, a polyurethane and a polyamide.