Metal-ceramic composite articulation

• US 6,881,229 B2
• Filed: 06/13/2002
• Issued: 04/19/2005
• Est. Priority Date: 06/14/2001
• Status: Expired due to Term

• Current Assignee: SiNtx Technologies, Inc.
• Original Assignee: Amedica Corporation
• Inventors: Khandkar, Ashok C., Lakshminarayanan, Ramaswamy, Hofmann, Aaron A.
• Primary Examiner(s): McDermott, Corrine
• Assistant Examiner(s): Landrem, Kamrin R.
• Application Number:
  US10/171,376
• Publication Number:
  US 20030153984A1
• Time in Patent Office: 1,041 Days
• Field of Search: 623/23.56, 623/22.15, 623/23.4, 623/926, 623/19.11, 623/20.14
• US Class Current: 623/23.56
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2002/3611 Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2310/00317 containing silicon nitride
• CPC Class Codes: A61L 2430/24 for joint reconstruction
• CPC Class Codes: A61L 27/045 Cobalt or cobalt alloys
• CPC Class Codes: A61L 27/10 Ceramics or glasses
• CPC Class Codes: A61L 27/42 having an inorganic matrix
• CPC Class Codes: A61L 27/427 of other specific inorganic materials not covered by A61L27/422 or A61L27/425

Abstract

A ceramic-metal composite articulation is provided with substantial elimination of wear debris, wherein a ceramic material is provided with superior mechanical properties tailored for articulating with ceramic articulations having high flexural strength (greater than about 700 MPa), high fracture toughness (greater than about 7 MPa^1/2) and a high Weibull modulus (greater than about 20), in comparison with presently available bio-ceramics such as alumina or zirconia. The mechanical property enhancement enables ceramic materials with greater reliability and significantly reduced in-vivo fracture risk to be obtained. Preliminary in-vitro wear performance, to several million cycles using established test protocols, of head/cup components in a prosthetic hip joint made from these ceramics also demonstrates the ultra low wear characteristics. These material properties substantially eliminate polyethylene (PE) wear debris mediated implant failures by offering an optimal combination of bio-mechanical safety and reliability with ultra low wear performance.

Claims

1. A joint prosthesis for articulation, comprising:

a first component shaped as a cup prosthesis and having a generally concave articulation surface formed from a biocompatible doped silicon nitride ceramic having a flexural strength greater than about 700 Mega-Pascal (MPa) and a toughness greater than about 7 Mega-Pascal root meter (MPam^0.5); and

a second component shaped as a head prosthesis and having a generally convex articulation surface formed from a biocompatible cobalt chromium metal alloy.

2. The joint prosthesis of claim 1 wherein said doped silicon nitride further includes dopants selected from the group consisting of yttrium oxide, magnesium oxide, strontium oxide, alumina, and combinations thereof.

3. The joint prosthesis of claim 1 wherein said biocompatible ceramic comprises Si₃N₄ doped with 6 weight % Y₂O₃+4 weight % Al₂O₃.

4. The joint prosthesis of claim 1 wherein said joint prosthesis is shaped as a hip prosthesis.

5. The joint prosthesis of claim 1 wherein said first component is shaped as a hip joint acetabular cup prosthesis and said second component is shaped as a hip joint femoral head prosthesis.

6. The joint prosthesis of claim 1 wherein the articulation surface of said biocompatible ceramic has a surface roughness of less than about 0.05 μ

m.

7. The joint prosthesis of claim 1 wherein the diametral clearance between articulation surfaces of said first and second components is between about 75 and about 250 μ

m.

8. The joint prosthesis of claim 7 wherein said clearance is between about 100 and about 200 μ

m.

9. The joint prosthesis of claim 1 wherein said joint prosthesis is shaped as a knee prosthesis.

10. The joint prosthesis of claim 1 wherein said joint prosthesis is shaped as a shoulder prosthesis.

11. The joint prosthesis of claim 1 wherein said second component comprises a cobalt chromium alloy having from about 0.06 to about 0.35% carbon by weight.

12. The joint prosthesis of claim 1 wherein said second component comprises an alloy having from about 58 to about 69 weight % cobalt, from about 26 to about 30 weight % chromium, from about 5 to about 7 weight % molybdenum and less than about 5 total weight % of other elements.

13. The joint prosthesis of claim 12 wherein said alloy further comprises up to about 1 weight % nickel, up to about 0.75 weight % iron, up to about 1 weight % silicon, up to about 1 weight % manganese and up to about 0.25 weight % nitrogen.

14. The joint prosthesis of claim 12 wherein said second component comprises a wrought alloy.

15. The joint prosthesis of claim 12 wherein said wrought alloy conforms to ASTM specification F1537.

16. A hip joint prosthesis, comprising:

an acetabular cup having an articulation surface formed from a biocompatible doped silicon nitride ceramic having a flexural strength greater than about 700 Mega-Pascal (MPa) and a toughness greater than about 7 Mega-Pascal root meter (MPam^0.5); and

a femoral head having an articulation surface formed from a biocompatible cobalt chromium metal alloy.

17. The hip joint prosthesis of claim 16 wherein said second component comprises a cobalt chromium alloy having a carbon content in the range of from about 0.06 to about 0.35% by weight.

18. The hip joint prosthesis of claim 16 wherein said doped silicon nitride further includes dopants selected from the group consisting of yttrium oxide, magnesium oxide, strontium oxide, alumina, and combinations thereof.

19. The hip joint prosthesis of claim 16 wherein said biocompatible ceramic comprises Si₃N₄ doped with 6 weight % Y₂O₃+4 weigh % Al₂O₃.

20. The hip joint prosthesis of claim 16 wherein the articulation surface of said femoral head is formed from a cobalt chromium alloy having a carbon content ranging from about 0.06 to about 0.35 weight %.

21. The hip joint prosthesis of claim 16 wherein the articulation surface of said biocompatible ceramic has a surface roughness of less than about 0.05 μ

m.

22. The hip joint prosthesis of claim 16 wherein the diametral clearance between the articulation surfaces of said acetabular cup and said femoral head is between about 75 and about 250 μ

m.

23. The hip joint prosthesis of claim 22 wherein said clearance is between about 100 and about 200 μ

m.

24. The hip joint prosthesis according to claim 16 wherein the articulation surface of said femoral head has a diametric size ranging from about 22 mm to about 44 mm.

25. A joint prosthesis for articulation, comprising:

a first component including an articulation surface formed from a biocompatible and high compressive strength doped silicon nitride ceramic, said articulation surface having a flexural strength greater than about 700 Mega-Pascal (MPa) and a toughness greater than about 7 Mega-Pascal root meter (MPam^0.5); and

a second component having an articulation surface formed from a biocompatible and high tensile strength cobalt chromium metal alloy;

said first component comprising a cup component and said second component comprising a head component for substantially mated articulation with said cup component.

26. The joint prosthesis of claim 25 wherein said first component comprises an acetabular cup for a hip prosthesis, and wherein said second component comprises a femoral head for a hip prosthesis.

27. The joint prosthesis of claim 25 wherein said first component comprises a tibial component of a knee prosthesis, and wherein said second component comprises a condylar component of a knee prosthesis.

28. The joint prosthesis of claim 25 wherein said joint prosthesis is shaped as a shoulder prosthesis.