DIFFUSION-HARDENED MEDICAL IMPLANT

• US 20110320007A1
• Filed: 06/27/2011
• Published: 12/29/2011
• Est. Priority Date: 12/15/2005
• Status: Active Grant

• Current Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith & Nephew Incorporated Reconstructive
• Inventors: Pawar, Vivek, Jani, Shilesh C., Weaver, Carolyn
• Granted Patent: US 8,647,701 B2
• Time in Patent Office: Days
• US Class Current: 623/23.53
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2002/30016 differing in hardness, e.g. Vickers, Shore, Brinell
• CPC Class Codes: A61F 2002/30922 Hardened surfaces
• CPC Class Codes: A61F 2002/30929 having at least two superposed coatings
• CPC Class Codes: A61F 2210/0076 multilayered, e.g. laminated structures
• CPC Class Codes: A61F 2250/0019 differing in hardness, e.g. Vickers, Shore, Brinell
• CPC Class Codes: A61F 2250/0041 differing in wear resistance
• CPC Class Codes: A61F 2310/00017 Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00089 Zirconium or Zr-based alloys
• CPC Class Codes: A61F 2310/00101 Molybdenum or Mo-based alloys
• CPC Class Codes: A61F 2310/00485 Coating made of zirconium or Zr-based alloys
• CPC Class Codes: A61F 2310/00592 Coating or prosthesis-covering structure made of ceramics or of ceramic-like compounds
• CPC Class Codes: A61F 2310/00598 Coating or prosthesis-covering structure made of compounds based on metal oxides or hydroxides
• CPC Class Codes: A61F 2310/00856 : Coating or prosthesis-covering structure made of compounds based on metal nitrides
• CPC Class Codes: A61L 2400/00 : Materials characterised by their function or physical properties
• CPC Class Codes: A61L 27/045 : Cobalt or cobalt alloys
• CPC Class Codes: A61L 27/047 : Other specific metals or alloys not covered by A61L27/042 - A61L27/045 or A61L27/06
• CPC Class Codes: A61L 27/06 : Titanium or titanium alloys
• CPC Class Codes: A61L 27/10 : Ceramics or glasses
• CPC Class Codes: A61L 27/30 : Inorganic materials
• CPC Class Codes: A61L 27/50 : Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: C23C 8/12 : using elemental oxygen or ozone
• CPC Class Codes: C23C 8/80 : After-treatment
• CPC Class Codes: Y10T 428/12611 : Oxide-containing component

Abstract

The present invention relates to a new composition and medical implant made therefrom, the composition comprising a thick diffusion hardened zone, and preferably further comprising a ceramic layer. The present invention relates to orthopedic implants comprising the new composition, methods of making the new composition, and methods of making orthopedic implants comprising the new composition.

Claims

1. A medical implant comprising:

a substrate comprising a biocompatible alloy;

a diffusion hardened zone in contact with said substrate, said diffusion hardened zone comprising a diffusion hardening species;

a ceramic layer in contact with said diffusion hardened zone, and

a metallic hardened layer comprising a surface of said medical implant.

2. The medical implant of claim 1 wherein said diffusion hardening species comprises oxygen and said biocompatible alloy comprises zirconium, said medical implant further comprising a ratio of atomic concentration of oxygen to atomic concentration of zirconium that increases in the direction of the substrate.

3. The medical implant of claim 2 wherein a portion of said increase in the ratio of atomic concentration of oxygen to atomic concentration of zirconium occurs in the metallic hardened layer.

4. The medical implant of claim 2 wherein said ratio of atomic concentration of oxygen to atomic concentration of zirconium ranges between 0.3 and 1.2.

5. The medical implant of claim 1 having an X-ray diffraction pattern where a reflection of tetragonal phase is negligible.

6. The medical implant of claim 1 wherein said substrate comprises grain size of less than 10 microns.

7. A medical implant comprising:

a first implant portion, said first implant portion having a first bearing surface; and

a second implant portion, said second implant portion having a second bearing surface;

wherein said first bearing surface and said second bearing surface are capable of engaging one another;

wherein one of said first bearing surface and second bearing surface comprises;

a substantially defect-free ceramic layer in contact with a diffusion hardened zone, wherein said diffusion hardened zone has a thickness of at least 2 microns;

wherein the thickness of the diffusion hardened zone is at least equal to or greater than the thickness of the substantially defect free ceramic layer.

8. The medical implant of claim 7, wherein the other of said first bearing surface and said second bearing surface comprises:

a substantially defect-free ceramic layer in contact with a diffusion hardened zone, wherein said diffusion hardened zone has a thickness of at least 2 microns;

wherein the thickness of the diffusion hardened zone is at least equal to or greater than the thickness of the substantially defect free ceramic layer.

9. The medical implant of claim 7, wherein the other of said first bearing surface and said second bearing surface comprises a material selected from the group consisting of polyethylene, ultra high molecular weight polyethylene, cross-linked polyethylene, polyurethane, alumina, silicon nitride, silicon carbide, zirconia, diamond, diamond-like carbon, metal oxides, metal nitrides, metal carbides, and any combination thereof.

10. The medical implant of claim 7 comprising a material selected from the group consisting of zirconium, zirconium alloy, titanium, tantalum, hafnium, niobium, and any combination thereof.

11. The medical implant of claim 7, wherein said diffusion hardened zone has a hardness profile 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.

12. The medical implant of claim 7, wherein said diffusion hardening zone comprises a diffusion hardening species selected from the group consisting of oxygen, nitrogen, boron, carbon, and any combination thereof.

13. The medical implant of claim 7, wherein the diffusion hardened zone comprises:

a first layer above a second layer, the thickness of said first layer is greater than said second layer.

14. The medical implant of claim 13 wherein said diffusion hardened zone further comprises a third layer below said second layer, the thickness of said first layer is greater than said third layer.

15. The medical implant of claim 7 further comprising a substrate below said diffusion hardened zone having grain size between about 1 micron and about 10 microns.

16. A medical implant comprising:

a substrate comprising a biocompatible alloy;

a diffusion hardened zone in contact with said substrate, said diffusion hardened zone comprising a diffusion hardening species, wherein the diffusion hardened zone has a layered structure comprising at least two distinct layers under metallographic analysis; and

a substantially defect free ceramic layer comprising a surface of said medical implant.

17. The medical implant of claim 16 wherein the diffusion hardening zone comprises a diffusion hardening species concentration that decreases in the direction of the substrate.

18. The medical implant of claim 17 wherein said concentration 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.

19. The medical implant of claim 16 further comprising a monoclinic content of at least 96%.

20. The medical implant of claim 16 wherein the thickness of said at least two distinct layers are substantially the same.

21. The medical implant of claim 16 wherein said at least two distinct layers comprise a first layer above a second layer, the thickness of said first layer is greater than said second layer.

22. The medical implant of claim 16 wherein said substantially defect free ceramic layer comprises a secondary phase extending through substantially the entire thickness of said substantially defect free ceramic layer.

23. The medical implant of claim 16 wherein said substrate comprises grain size between about 1 micron and about 10 microns.

24. A medical implant comprising:

a substrate comprising a biocompatible alloy;

a substantially defect-free ceramic layer in contact with a diffusion hardened zone, wherein said diffusion hardened zone has a thickness of at least 2 microns, wherein the thickness of the diffusion hardened zone is at least equal to or greater than the thickness of the substantially defect free ceramic layer; and

a metallic hardened layer comprising a surface of said medical implant.

25. The medical implant of claim 24, wherein said diffusion hardened zone has a hardness profile 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.

26. The medical implant of claim 24, wherein the diffusion hardened zone comprises:

a first layer above a second layer, the thickness of said first layer is greater than said second layer.

27. The medical implant of claim 26 wherein said diffusion hardened zone further comprises a third layer below said second layer, the thickness of said first layer is greater than said third layer.

28. The medical implant of claim 24 wherein said substrate comprises grain size between about 1 micron and about 10 microns.