Selectively cross-linked polyethylene orthopedic devices

Abstract

An improved prosthetic medical device having improved wear resistance and toughness is provided in the present application. A method is provided to selectively cross-link the polymeric matrix comprising the medical device by employing an interrupting means such as a mask, wire mesh or chopper wheel placed in between the medical device and irradiation source. In addition, the medical device may be translated while being irradiated to further effect the selective cross-linking. The present invention also provides for an injection molding process wherein a prosthetic medical device is formed in a single step, then selectively cross-linked.

1 . An orthopedic prosthetic medical device produced by the process comprising the steps: 
 (a) providing a polyethylene workpiece having a joint or limb bearing surface area;    (b) positioning at least one irradiation source adjacent to the workpiece so that the workpiece may be exposed to irradiation from the irradiation source; and    (c) interrupting the irradiation source so that at least portions of the joint or limb bearing surface area are cross-linked and adjacent portions of the joint or limb bearing surface area are not cross-linked.    
     
     
         2 . The orthopedic prosthetic medical device of  claim 1 , further comprising the step of shaping the workpiece into an orthopedic prosthetic device.  
     
     
         3 . The orthopedic prosthetic medical device of  claim 1 , wherein the polyethylene is UHMWPE.  
     
     
         4 . The orthopedic prosthetic medical device of  claim 1 , wherein the irradiation is interrupted by a perforated mask.  
     
     
         5 . The orthopedic prosthetic medical device of  claim 1 , wherein the workpiece exposure to irradiation is provided at a dose of between about 2.5 to 100 Mrads.  
     
     
         6 . The orthopedic prosthetic medical device of  claim 1 , wherein the workpiece exposure to irradiation is provided at a dose of between about 5 to 25 Mrads.  
     
     
         7 . The orthopedic prosthetic medical device of  claim 1 , wherein the workpiece exposure to irradiation is provided at a dose of between about 10 to 20 Mrads.  
     
     
         8 . The orthopedic prosthetic medical device according to  claim 1 , further comprising the step of translating the workpiece.  
     
     
         9 . The orthopedic prosthetic medical device of  claim 1 , wherein the steps effectuate cross-linking of a selected pattern on the joint or limb bearing surface area.  
     
     
         10 . The orthopedic prosthetic medical device of  claim 1 , wherein the steps effectuate cross-linking of a selected percentage of the joint or limb bearing surface area.  
     
     
         11 . The orthopedic prosthetic medical device of  claim 10 , wherein the selected percentage of cross-linking is within a range of between 1 to 90%.  
     
     
         12 . The orthopedic prosthetic medical device of  claim 10 , wherein the selected percentage of cross-linking is within a range of between about 2.5 to 50%.  
     
     
         13 . The orthopedic prosthetic medical device of  claim 10 , wherein the selected percentage of cross-linking is within a range of between about 5 to 30%.  
     
     
         14 . The orthopedic prosthetic medical device of  claim 10 , wherein the selected percentage of cross-linking is within a range of between about 1 to 50%.  
     
     
         15 . The orthopedic prosthetic medical device of  claim 10 , wherein the selected percentage of cross-linking is within a range of between about 2.5 to 40%.  
     
     
         16 . The orthopedic prosthetic medical device of  claim 9 , wherein the selected pattern comprises a cross-hatched pattern of cross-linked and non-cross-linked zones.  
     
     
         17 . An orthopedic prosthetic medical device produced by the process comprising the steps: 
 (a) providing a polyethylene workpiece;    (b) positioning at least one irradiation source adjacent to the workpiece so that at least the surface of the workpiece may be exposed to irradiation from the irradiation source;    (c) interrupting the irradiation source to form a plurality of cross-linked areas and non-cross-linked areas on the surface of the workpiece; and    (d) forming an orthopedic prosthetic joint or limb bearing surface on the workpiece including both said plurality of cross-linked and non-cross-linked areas.    
     
     
         18 . An orthopedic prosthetic medical device produced by the process comprising the steps: 
 (a) providing a polyethylene workpiece having a joint or limb bearing surface area;    (b) positioning at least one irradiation source adjacent to the workpiece so that the workpiece may be exposed to irradiation from the irradiation source; and    (c) interrupting the irradiation source so that at least portions of the joint or limb bearing surface area are formed by a plurality of cross-linked areas adjacent to a plurality of non-cross-linked areas.    
     
     
         19 . An orthopedic prosthetic medical device comprising a selectively cross-linked polyethylene polymer joint or limb bearing surface area, whereby the joint or limb bearing surface area is selectively cross-linked to a range between 2.5 to 40%.  
     
     
         20 . An orthopedic prosthetic medical device comprising a selectively cross-linked polyethylene polymer joint or limb bearing surface area is selectively cross-linked to a range between about 5 to 30%.  
     
     
         21 . An orthopedic prosthetic medical device comprising a selectively cross-linked polyethylene polymer joint or limb bearing surface area, whereby the joint or limb bearing surface area is selectively cross-linked to a range between about 2.5 to 50%.