Porous metal articles having a predetermined pore character

• US 20060002810A1
• Filed: 07/02/2004
• Published: 01/05/2006
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Praxis Powder Technology, Inc.
• Original Assignee: Praxis Powder Technology, Inc.
• Inventors: Grohowski, Joseph A. Jr.
• Granted Patent: US 7,674,426 B2
• Time in Patent Office: Days
• US Class Current: 419/2
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/30771 applied in original prostheses, e.g. holes or grooves
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2002/30011 differing in porosity
• CPC Class Codes: A61F 2002/30929 having at least two superposed coatings
• CPC Class Codes: A61F 2002/30957 using a positive or a negative model, e.g. moulds
• CPC Class Codes: A61F 2002/30968 Sintering
• CPC Class Codes: A61F 2250/0023 differing in porosity
• 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 2310/00047 Aluminium or Al-based alloys
• CPC Class Codes: A61F 2310/00071 Nickel or Ni-based alloys
• CPC Class Codes: A61F 2310/00077 Copper or Cu-based alloys
• CPC Class Codes: A61F 2310/00095 Niobium or Nb-based alloys
• CPC Class Codes: A61F 2310/00131 Tantalum or Ta-based alloys
• CPC Class Codes: A61L 27/04 : Metals or alloys
• CPC Class Codes: A61L 27/56 : Porous materials, e.g. foams or sponges
• CPC Class Codes: B01D 39/2093 : Ceramic foam
• CPC Class Codes: B22F 1/103 : containing an organic binding agent comprising a mixture of, or obtained by reaction of, two or more components other than a solvent or a lubricating agent
• CPC Class Codes: B22F 2998/00 : Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 3/02 : Compacting only
• CPC Class Codes: B22F 3/1025 : not by heating only
• CPC Class Codes: B22F 3/1109 : Inhomogenous pore distribution composite layers of porous nature B22F7/002
• CPC Class Codes: B22F 3/1134 : Inorganic fillers carbonaceous or paper filler B22F3/1121
• CPC Class Codes: B22F 3/20 : by extruding
• CPC Class Codes: B22F 3/22 : for producing castings from a slip
• CPC Class Codes: B22F 3/225 : by injection molding
• CPC Class Codes: B29C 43/006 : Pressing and sintering powders, granules or fibres
• CPC Class Codes: B29L 2031/7532 : Artificial members, protheses
• CPC Class Codes: B30B 11/001 : using a flexible element, e.g. diaphragm, urged by fluid pressure; Isostatic presses

Abstract

A porous metal article having a predetermined pore structure. The porosity is provided by the use of an extractable particulate in a powder forming route to create a desired porosity. Extraction of the pore forming particulate prior to sintering of the powder minimizes contamination of the sintered article and allows for the processing of material sensitive to contamination such as titanium. Added functionality can be gained by co-forming the porous material with non-porous material to create an article with layers of differing characteristics. The article is suitable for use as an implant body is porous enough to facilitate tissue in-growth and bony fusion.

Claims

1. An apparatus comprising a porous metal structure including a tailored pore character throughout the structure.

2. The apparatus as set forth in claim 1, wherein the tailored pore character is pore density.

3. The apparatus as set forth in claim 1, wherein the tailored pore character is pore size.

4. The apparatus as set forth in claim 1, wherein the tailored pore character is pore distribution within the apparatus.

5. The apparatus as set forth in claim 1, wherein the tailored pore character is pore size distribution.

6. The apparatus as set forth in claim 1, wherein the tailored pore character is pore shape.

7. The apparatus as set forth in claim 1, wherein the tailored pore character is determined by an extractable particulate.

8. The apparatus as set forth in claim 7, wherein the extractable particulate is soluble in a fluid.

9. The apparatus as set forth in claim 8, wherein the fluid is water.

10. The apparatus as set forth in claim 1, wherein the porous metal structure is a green article.

11. The apparatus as set forth in claim 1, wherein the porous metal structure comprises a metal powder.

12. The apparatus as set forth in claim 11, wherein the metal powder is compacted to less than 95 percent of theoretical density.

13. The apparatus as set forth in claim 11, wherein the metal powder is unsintered.

14. The apparatus as set forth in claim 11, wherein the metal powder is sintered.

15. The apparatus as set forth in claim 1, wherein the porous metal structure comprises a metal selected from the group consisting of titanium, tantalum, cobalt, chromium, niobium, stainless steel, nickel, copper, aluminum, and alloys thereof

16. The apparatus as set forth claim 1, wherein the apparatus is an orthopedic implant.

17. The apparatus as set forth claim 1, wherein the apparatus is a filter.

18. An article comprising a porous metal structure having pores defined by a metal matrix.

19. The article as set forth in claim 18, wherein the pores are formed by an extractable particulate.

20. The article as set forth in claim 19, wherein the extractable particulate is soluble in a fluid.

21. The article as set forth in claim 20, wherein the fluid is water.

22. The article as set forth in claim 19, wherein the metal matrix comprises sintered metal powder.

23. The article as set forth in claim 22, wherein the extractable material is extracted prior to sintering.

24. The article as set forth in claim 19, wherein the metal matrix comprises less than 2000 ppm of the extractable particulate.

25. The article as set forth in claim 19, wherein the pores have a pore volume ranging from 0 to 95 percent of the total volume of the metal article.

26. The article as set forth in claim 19, wherein at least a portion of the metal article is dense.

27. The article as set for the in claim 18, wherein the porous metal structure comprises at least two layers of differing pore character.

28. The article as set forth in claim 18, wherein the metal matrix is selected from the group consisting of:

titanium, tantalum, cobalt, chromium, niobium, stainless steel, nickel, copper, aluminum, and alloys thereof.

29. The article as set forth in claim 18, wherein the porous metal article is attached to a non-porous substrate by a bond.

30. The article as set forth in claim 29, wherein the bond is formed by sintering.

31. The article as set forth in claim 18 wherein the pores are interconnected and have a pore size of less than 1000 micron.

32. The article as set forth in claim 18 wherein the article is an orthopedic implant.

33. The article as set forth in claim 18 wherein the article is a filter.

34. A sintered porous metal article having a cross section greater than 2.5 centimeters.

35. A method of making a porous metal article, the method comprising:

a. blending a metal powder and an extractable particulate to form a composite;

b. forming the composite into a green article;

c. removing the extractable particulate from the green article to form a metal matrix and pore structure;

d. sintering the metal matrix and pore structure.

36. The method of claim 35, further comprising adding a homogenizing aid to the composite.

37. The method of claim 36, wherein the homogenizing aid is a volatile liquid.

38. The method of claim 36, wherein the homogenizing aid is acetone.

39. The method of claim 36, wherein the homogenizing aid is an organic material.

40. The method of claim 36, wherein the homogenizing aid is polyethylene glycol.

41. The method of claim 36, wherein the homogenizing aid is an alcohol.

42. The method of claim 36, wherein the homogenizing aid is an isoparaffinic solvent.

43. The method of claim 35, wherein the metal powder is selected from the group consisting of:

titanium, tantalum, cobalt chrome, niobium, stainless steel, nickel, copper, aluminum, and alloys thereof.

44. The method of claim 43, wherein the metal powder is −

100 mesh.

45. The method of claim 35, wherein the extractable particluate is selected from the group consisting of:

salts, sorbates, inorganic materials, and organic materials.

46. The method of claim 35, wherein the extractable particulate has a diameter between about 100 and 2000 micron.

47. The method of claim 35, wherein the green article is formed by slip casting.

48. The method of claim 35, wherein the green article is formed by compaction.

49. The method of claim 35, wherein the green article is formed by extrusion.

50. The method of claim 35, wherein the green article is formed by injection molding.

51. The method of claim 35, wherein the extractable particulate is removed by dissolving the extractable particulates in a fluid.

52. The method of claim 51, wherein the fluid is water.

53. The method of claim 51, wherein the fluid is a gas.

54. The method of claim 35, wherein the metal matrix and pore structure has sufficient green strength to be handled prior to sintering.

55. The method of claim 35, wherein the porous metal article is an orthopedic implant.

56. The method of claim 35, wherein the porous metal article is a filter.

57. The method of claim 35, wherein the porous metal article has a pore size substantially the similar to the size of the extractable particulate used to form the pore.

58. The method of claim 57, wherein the pore size can be varied by changing the size of the extractable particulates.

59. The method of claim 35, wherein the porous metal article has a pore shape substantially similar to the shape of the extractable particulate used to form the pore.

60. The method of claim 59, wherein the pore shape can be varied by changing the shape of the extractable particulates.

62. An orthopedic implant comprising the porous metal article according to claim 35.

63. The orthopedic implant of claim 62 wherein the metal matrix and pore structure is suitable for bone ingrowth.

61. A method of making a porous metal article, the method comprising:

a. blending a metal powder and an extractable particulate to form a composite;

b. forming the composite onto a substrate;

c. removing the extractable particulate

d. sintering the metal powder.