Diffusion-hardened medical implant

Abstract

A composition and medical implant made therefrom, the composition including a thick diffusion hardened zone, and preferably further including a ceramic layer. Also provided are orthopedic implants made from the composition, methods of making the composition, and methods of making orthopedic implants from the composition.

1 . A medical implant comprising:
 a substrate comprising a zirconium-niobium alloy;   a diffusion hardened zone in contact with said substrate, said diffusion hardened zone comprising zirconium or zirconium alloy and a diffusion hardening species, said diffusion hardened zone having a thickness of greater than 5 microns; and   a substantially defect-free ceramic layer in contact with and overlaying said diffusion hardened zone and comprising a surface of said medical implant, said ceramic layer ranging in thickness from 0.1 to 25 microns; and   wherein the total thickness of the ceramic layer and the diffusion hardened zone is greater than 5 microns.   
     
     
         2 . The medical implant of  claim 1 , wherein said diffusion hardened zone has a thickness of greater than 10 microns. 
     
     
         3 . The medical implant of  claim 1 , wherein the ceramic layer comprises a secondary phase; and
 the diffusion hardened zone has a layered structure comprising at least two distinct layers under metallographic analysis, the layered structure characterized by:
 a first layer directly below the ceramic layer, wherein the first layer is predominantly alpha phase zirconium; 
 an interface between the first layer and the ceramic layer; and 
 a second layer directly below the first layer. 
   
     
     
         4 . The medical implant of  claim 3 , wherein said diffusion hardening species is oxygen and the diffusion hardened zone has concentration of oxygen which decreases in the direction of the substrate, said decrease of oxygen concentration being defined by a function selected from the group consisting of an error function, an exponential function, a near uniform distribution function, and any sequential combination thereof. 
     
     
         5 . The medical implant of  claim 3 , wherein said diffusion hardened zone has a hardness profile which is defined by a function selected from the group consisting of an error function, an exponential function, a near uniform distribution function, and any sequential combination thereof. 
     
     
         6 . The medical implant of  claim 3 , wherein said substrate has a niobium content of at least 1% (w/w). 
     
     
         7 . The medical implant of  claim 3 , further comprising an oxygen-containing zirconium alloy overlaying said ceramic layer on the surface of said implant, said alloy being in the metallic state. 
     
     
         8 . The medical implant of  claim 1 , wherein said substrate further comprises titanium, tantalum, hafnium, and any combination thereof; and
 said diffusion hardening species is selected from the group consisting of oxygen, nitrogen, boron, carbon, and any combination thereof.   
     
     
         9 . The medical implant of  claim 1 , further comprising:
 (a) a first implant portion comprising zirconium or zirconium alloy, said first implant portion having a bearing surface;   (b) a second implant portion comprising zirconium or zirconium alloy, said second implant portion having bearing surface;   wherein the bearing surface of said first implant portion and the bearing surface of said second implant portion each have a size and shape to engage or cooperate with one another.   
     
     
         10 . The medical implant of  claim 1 , wherein the medical implant is selected from one of a hip implant, a knee implant, a shoulder implant, an elbow implant, and a spinal implant. 
     
     
         11 . The medical implant of  claim 1 , wherein the medical implant is a hip implant. 
     
     
         12 . A medical implant comprising:
 a substrate comprising a zirconium-niobium alloy;   a diffusion hardened zone in contact with said substrate, said diffusion hardened zone comprising zirconium or zirconium alloy and a diffusion hardening species, said diffusion hardened zone having a thickness of greater than 5 microns; and   wherein the diffusion hardened zone has a layered structure comprising at least two distinct layers under metallographic analysis, said layered structure characterized by:
 a first layer on a surface of the implant; 
 a second layer directly below said first layer, wherein said first layer is predominantly alpha phase zirconium; and 
 said layered structure having a concentration of diffusion hardening species which decreases in the direction of the substrate, said decrease of concentration of diffusion hardening species being defined by a function selected from the group consisting of an error function, an exponential function, a near uniform distribution function, and any sequential combination thereof. 
   
     
     
         13 . The medical implant of  claim 12 , wherein said diffusion hardened zone has a thickness of greater than 10 microns. 
     
     
         14 . The medical implant of  claim 12 , wherein said diffusion hardening species comprises oxygen and the diffusion hardened zone has a concentration of oxygen which decreases in the direction of the substrate, said decrease of oxygen concentration being defined by a function selected from the group consisting of an error function, an exponential function, a near uniform distribution function, and any sequential combination thereof. 
     
     
         15 . The medical implant of  claim 12 , wherein the diffusion hardened zone has a hardness profile which is defined by a function selected from the group consisting of an error function, an exponential function, a near uniform distribution function any sequential combination thereof. 
     
     
         16 . The medical implant of  claim 12 , wherein said substrate has a niobium content of at least 1% (w/w). 
     
     
         17 . The medical implant of  claim 12 , wherein said substrate further comprises titanium, tantalum, hafnium, and any combination thereof; and
 said diffusion hardening species is selected from the group consisting of oxygen, nitrogen, boron, carbon, and any combination thereof.   
     
     
         18 . The medical implant of  claim 12 , further comprising:
 (a) a first implant portion comprising zirconium or zirconium alloy, said first implant portion having a bearing surface;   (b) a second implant portion comprising zirconium or zirconium alloy, said second implant portion having bearing surface;   wherein the bearing surface of said first implant portion and the bearing surface of said second implant portion each have a size and shape to engage or cooperate with one another.   
     
     
         19 . The medical implant of  claim 12 , wherein the medical implant is selected from one of a hip implant, a knee implant, a shoulder implant, an elbow implant, and a spinal implant. 
     
     
         20 . The medical implant of  claim 12 , wherein the medical implant is a hip implant.