Composite prosthetic bearing having a crosslinked articulating surface and method for making the same

Abstract

An implantable prosthetic bearing is constructed of a composite material having a first layer and second layer. The first layer has an articulating surface defined therein, whereas the second layer has a engaging surface defined therein for engaging either another prosthetic component or the bone itself. The first layer of the implantable prosthetic bearing is constructed of crosslinked polymer such as Ultra-High Molecular Weight Polyethylene, whereas the second layer of the implantable prosthetic bearing is constructed of polymer such as Ultra-High Molecular Weight Polyethylene that is either non-crosslinked or crosslinked to a lesser degree than the first layer. In such a manner, the first layer possesses mechanical properties which are advantageous in regard to the articulating surface (e.g., enhanced wear and oxidation resistance), whereas the second layer possesses mechanical properties which are advantageous in regard to the engaging surface (e.g., high ductility, toughness, and creep resistance). A method of making a prosthetic bearing is also disclosed.

1 . A method of making an implantable bearing for an orthopaedic prosthesis, comprising:
 exposing a first layer of polymer to a first dose of radiation,   molding the first layer of polymer to a second layer of polymer so as to create a composite, and   forming the composite into a predetermined shape of the implantable bearing.   
     
     
         2 . The method of  claim 1 , further comprising the step of exposing the second layer of polymer to a second dose of radiation, which is different than the first dose of radiation, prior to molding the first layer of polymer to the second layer of polymer. 
     
     
         3 . The method of  claim 2 , wherein the second dose of radiation is less than the first dose of radiation. 
     
     
         4 . The method of  claim 3 , wherein forming the composite comprises forming an articulating surface in the first layer of polymer. 
     
     
         5 . The method of  claim 2 , wherein:
 exposing the first layer of polymer comprises exposing the first layer of polymer to the first dose of radiation so as to crosslink the first layer of polymer to a first degree, and   exposing the second layer of polymer comprises exposing the second layer of polymer to the second dose of radiation so as to crosslink the second layer of polymer to a second degree which is less than the first degree.   
     
     
         6 . The method of  claim 1 , wherein molding the first layer of polymer to the second layer of polymer is contemporaneously performed with forming the composite into the predetermined shape of the implantable bearing. 
     
     
         7 . The method of  claim 1 , wherein molding the first layer of polymer to the second layer of polymer comprises compression molding the first layer of polymer and the second layer of polymer to one another. 
     
     
         8 . The method of  claim 1 , wherein:
 both the first layer of polymer and the second layer of polymer comprise polyethylene, and   molding the first layer of polymer to the second layer of polymer comprises melt-fusing the polyethylene of the first layer of polymer to the polyethylene of the second layer of polymer.   
     
     
         9 . The method of  claim 1 , wherein forming the composite comprises molding the composite into an acetabular bearing which is adapted to be implanted into an acetabulum of a patient. 
     
     
         10 . The method of  claim 1 , wherein forming the composite comprises molding the composite into a glenoid bearing which is adapted to be implanted into a glenoid of a patient. 
     
     
         11 . The method of  claim 1 , wherein forming the composite comprises molding the composite into a tibial bearing which is adapted to be implanted into a tibia of a patient. 
     
     
         12 . The method of  claim 1 , wherein:
 exposing the first layer of polymer comprises exposing a first polymer preform to the first dose of radiation, and   molding the first layer of polymer to the second layer of polymer comprises molding the first polymer preform to a second polymer preform so as to create the composite.   
     
     
         13 . The method of  claim 12 , further comprising exposing the second polymer preform to a second dose of radiation, which is less than the first dose of radiation, prior to molding the first polymer preform to the second polymer preform. 
     
     
         14 . The method of  claim 1 , wherein:
 exposing the first layer of polymer comprises exposing a polymer powder to the first dose of radiation, and   molding the first layer of polymer to the second layer of polymer comprises molding the polymer powder to a polymer preform so as to create the composite.   
     
     
         15 . The method of  claim 14 , further comprising exposing the polymer preform to a second dose of radiation, which is different than the first dose of radiation, prior to molding the polymer powder to the polymer preform. 
     
     
         16 . The method of  claim 1 , wherein:
 exposing the first layer of polymer comprises exposing a polymer powder to the first dose of radiation, and   molding the first layer of polymer to the second layer of polymer comprises molding the polymer powder to a polymer porous structure so as to create the composite.   
     
     
         17 . The method of  claim 16 , further comprising exposing the polymer porous structure to a second dose of radiation, which is different than the first dose of radiation, prior to molding the polymer powder to the polymer porous structure. 
     
     
         18 . The method of  claim 1 , wherein:
 exposing the first layer of polymer comprises exposing a polymer porous structure to the first dose of radiation, and   molding the first layer of polymer to the second layer of polymer comprises securing the polymer porous structure to a polymer preform so as to create the composite.   
     
     
         19 . The method of  claim 1 , wherein at least part of at least one of the first layer of polymer and the second layer or polymer is melted during the molding step. 
     
     
         20 . The method of  claim 1 , wherein molding the first layer of polymer to the second layer of polymer comprises melt-fusing the first layer of polymer and the second layer of polymer together. 
     
     
         21 . The method of  claim 1 , further comprising sterilizing the formed implantable bearing using a surface irradiation technique to a degree that is adequate for pre-implant sterilization. 
     
     
         22 . A method of making an implantable bearing for an orthopaedic prosthesis, comprising:
 molding a layer of crosslinked polymer to a layer of non-crosslinked polymer so as to create a composite, and   forming the composite into a predetermined shape of the implantable bearing.   
     
     
         23 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer is contemporaneously performed with forming the composite into the predetermined shape of the implantable bearing. 
     
     
         24 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises compression molding the layer of crosslinked polymer and the layer of non-crosslinked polymer to one another. 
     
     
         25 . The method of  claim 22 , wherein:
 both the layer of crosslinked polymer and the layer of non-crosslinked polymer comprise polyethylene, and   molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises fusing the polyethylene of the layer of crosslinked polymer to the polyethylene of the layer of non-crosslinked polymer.   
     
     
         26 . The method of  claim 22 , wherein forming the composite comprises molding the composite into an acetabular bearing which is adapted to be implanted into an acetabulum of a patient. 
     
     
         27 . The method of  claim 22 , wherein forming the composite comprises molding the composite into a glenoid bearing which is adapted to be implanted into a glenoid of a patient. 
     
     
         28 . The method of  claim 22 , wherein forming the composite comprises molding the composite into a tibial bearing which is adapted to be implanted into a tibia of a patient. 
     
     
         29 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding a crosslinked polymer preform to a non-crosslinked polymer preform. 
     
     
         30 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding a crosslinked polymer preform to a non-crosslinked polymer powder. 
     
     
         31 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding a crosslinked, polymer porous structure to a non-crosslinked polymer powder. 
     
     
         32 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding a crosslinked, polymer porous structure to a non-crosslinked polymer preform. 
     
     
         33 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding an articulating surface in the layer of crosslinked polymer. 
     
     
         34 . The method of  claim 22 , wherein at least part of one of the layer of crosslinked polymer and the layer of non-crosslinked polymer is melted during molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding. 
     
     
         35 . The method of  claim 22 , wherein at least one of the layer of crosslinked polymer and the layer of non-crosslinked polymer is melted during the step of molding the layer of crosslinked polymer to the layer of non-crosslinked polymer. 
     
     
         36 . The method of  claim 22 , wherein molding the layer of crosslinked polymer to the layer of non-crosslinked polymer comprises molding comprises melt-fusing the layer of crosslinked polymer and the layer of non-crosslinked polymer together. 
     
     
         37 . The method of  claim 22 , further comprising sterilizing the formed implantable bearing without gamma irradiation to a degree that is adequate for pre-implant sterilization.