Gradient porous implant

• US 20070150068A1
• Filed: 12/23/2005
• Published: 06/28/2007
• Est. Priority Date: 12/23/2005
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Inventors: Jones, Eric, Wang, Aiguo, Dong, Nicholas, Plaskon, Gregory
• Granted Patent: US 7,578,851 B2
• Time in Patent Office: Days
• US Class Current: 623/22.320
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence
• 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 2/34 Acetabular cups
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2/367 Proximal or metaphyseal parts of shafts trochanteric devices connected to said proximal parts A61F2/30739
• CPC Class Codes: A61F 2/3672 Intermediate parts of shafts
• CPC Class Codes: A61F 2/3676 Distal or diaphyseal parts of shafts
• CPC Class Codes: A61F 2002/30011 differing in porosity
• CPC Class Codes: A61F 2002/30322 differing in surface structures
• CPC Class Codes: A61F 2002/30324 differing in thickness
• CPC Class Codes: A61F 2002/30769 madreporic
• CPC Class Codes: A61F 2002/30822 Circumferential grooves
• CPC Class Codes: A61F 2002/30838 Microstructures
• CPC Class Codes: A61F 2002/3092 having an open-celled or open-pored structure
• CPC Class Codes: A61F 2002/30929 having at least two superposed coatings
• CPC Class Codes: A61F 2002/30968 Sintering
• CPC Class Codes: A61F 2002/3403 Polar aperture
• CPC Class Codes: A61F 2002/3611 : Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2002/3631 : with an integral complete or partial peripheral collar or bearing shoulder at its base
• CPC Class Codes: A61F 2002/368 : with lateral apertures, bores, holes or openings, e.g. for reducing the mass, for receiving fixation screws or for communicating with the inside of a hollow shaft
• CPC Class Codes: A61F 2250/0023 : differing in porosity
• CPC Class Codes: A61F 2250/0026 : differing in surface structures
• CPC Class Codes: A61F 2250/0036 : differing in thickness
• CPC Class Codes: A61F 2310/00011 : Metals or alloys
• 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 2310/00095 : Niobium or Nb-based alloys
• CPC Class Codes: A61F 2310/00131 : Tantalum or Ta-based alloys
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00401 : Coating made of iron, of stainless steel or of other Fe-based alloys
• CPC Class Codes: A61F 2310/00407 : Coating made of titanium or of Ti-based alloys
• CPC Class Codes: A61F 2310/00413 : Coating made of cobalt or of Co-based alloys
• CPC Class Codes: A61F 2310/00491 : Coating made of niobium or Nb-based alloys
• CPC Class Codes: A61F 2310/00544 : Coating made of tantalum or Ta-based alloys
• CPC Class Codes: B22F 2207/13 : Size gradients
• CPC Class Codes: B22F 2998/10 : Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 : Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/1137 : by coating porous removable preforms
• CPC Class Codes: B22F 3/1146 : After-treatment maintaining the porosity B22F3/114 takes precedence
• CPC Class Codes: B33Y 80/00 : Products made by additive manufacturing
• CPC Class Codes: C23C 26/00 : Coating not provided for in groups C23C2/00 - C23C24/00
• CPC Class Codes: C23C 28/00 : Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
• CPC Class Codes: C23C 28/026 : including at least one amorphous metallic material layer
• CPC Class Codes: C23C 28/028 : Including graded layers in composition or in physical properties, e.g. density, porosity, grain size

Abstract

An implantable medical device includes a porous metal foam or foam-like structure having pores defined by metal struts or webs wherein the porous structure has directionally controlled pore characteristics. The pore characteristics controlled include one or more of the metal structure porosity, pore size, pore shape, pore size distribution and strut thickness. The pore characteristics may vary in one or more directions throughout the structure. Preferably the pore characteristics are controlled to match the porous metal structure to various mechanical and biological requirements of different regions of the structure in order to optimize aspects of the implants performance and may vary not only over the surface of the porous structure but through the depth of the porous structure. The thickness of the porous metal structure may also be modified to establish a thickness profile that optimizes mechanical and biological requirements of the implants performance. Acetabular cup embodiments of the invention are described. Various methods of manufacturing implants having directionally controlled pore characteristics are described.

Claims

1. An acetabular cup comprising:

a bearing surface; and

a shell surrounding said bearing surface, said shell having an outer generally hemispherical surface for contacting bone, said hemispherical surface having a pole and an equator, said shell having an inner solid substrate layer with a porous outer layer said porous outer layer having a first thickness and a first porosity adjacent an equatorial region of said hemispherical surface and a second thickness and a second porosity adjacent a polar region of the hemispherical surface, said second thickness being greater than said first thickness.

2. The acetabular cup as set forth in claim 1 wherein said first thickness ranges from 0.1 mm to 1.5 mm.

3. The acetabular cup as set forth in claim 1 said second porosity being greater than said first porosity.

4. The acetabular cup as set forth in claim 1 said first porosity being greater than said second porosity.

5. The acetabular cup as set forth in claim 1 said first porosity and said second porosity being equal.

6. The acetabular cup as set forth in claim 1 wherein the thickness of said porous outer layer monotonically decreases along the outer shell surface on moving from said polar region to said equatorial region.

7. The acetabular cup as set forth in claim 1 wherein said shell has at least one aperture therethrough.

8. The acetabular cup as set forth in claim 1 wherein said shell has at least one aperture partially therethrough, said aperture passing substantially through said inner solid substrate layer and not passing through said porous outer layer.

9. The acetabular cup as set forth in claim 1 wherein the porosity of said outer layer decreases through said layer along a gradient normal to said surface.

10. The acetabular cup as set forth in claim 1 wherein the porosity of said outer layer decreases from said first porosity along a gradient normal to said surface through said first thickness.

11. The acetabular cup as set forth in claim 1 wherein the porosity of said outer layer decreases from said second porosity along a gradient normal to said surface through said second thickness.

12. The acetabular cup as set forth in claim 1 wherein said first porosity is in the range from 0% to 50% and the second porosity is in the range from 20% to 90%.

13. The acetabular cup as set forth in claim 1 wherein said first thickness ranges from 0.1 mm to 1.5 mm and said second thickness ranges from 1 mm to 20 mm.

14. The acetabular cup as set forth in claim 3 wherein said porosity decreases along said outer shell surface on moving from said polar region to said equatorial region.

15. The acetabular cup as set forth in claim 3 wherein the porosity of said outer layer decreases from said first porosity along a gradient normal to said surface through said first thickness.

16. The acetabular cup as set forth in claim 3 wherein the porosity of said outer layer decreases from said second porosity along a gradient normal to said surface through said second thickness.

17. The acetabular cup as set forth in claim 6 wherein the thickness of said porous outer layer decreases substantially continuously on moving from said polar region to said equatorial region.

18. The acetabular cup as set forth in claim 13 wherein said equatorial region has pore sizes of between 5 and 200 μ

m and said polar region has pores of between 100 and 1000 μ

M.

19. The acetabular cup as set forth in claim 16 wherein said thickness decreases linearly on moving from said polar region to said equatorial region.

20. The acetabular cup as set forth in claim 16 wherein said thickness decreases sinusoidaly on moving from said polar region to said equatorial region.

21. The acetabular cup as set forth in claim 1 wherein said porous outer layer comprises a polar partial spherical zone and an equatorial partial spherical zone, said polar partial spherical zone overlying said equatorial partial spherical zone in a polar region defined by a polar angle φ

1, said polar partial spherical zone and said equatorial partial spherical zone having different pore characteristics.

22. The acetabular cup as set forth in claim 1 wherein said porous outer layer comprises a polar partial spherical zone, an intermediate partial spherical zone and an equatorial partial spherical zone, said polar partial spherical zone overlying said intermediate partial spherical zone and said equatorial partial spherical zone in a polar region defined by a polar angle φ

1 and said intermediate partial spherical zone overlying said equatorial partial spherical zone in a region defined by polar angle φ

2, said polar partial spherical zone, said intermediate partial spherical zone and said equatorial partial spherical zone having different pore characteristics.

23. The acetabular cup as set forth in claim 1 wherein said porous outer layer comprises a polar partial spherical zone and an equatorial partial spherical zone, said polar partial spherical zone overlying said substrate in a polar region, said equatorial partial spherical zone overlying said substrate in an equatorial region and comprising an inner and outer layer said polar partial spherical zone and said equatorial partial spherical zone inner and outer layers each having different pore characteristics.

24. The acetabular cup as set forth in claim 23 wherein said polar partial spherical zone is more porous than said equatorial partial spherical zone outer layer and said equatorial partial spherical zone outer layer is more porous than said equatorial partial spherical zone inner layer.

25. The acetabular cup as set forth in claim 1 wherein said shell has an overall thickness and said first thickness is approximately less than 25% of said overall thickness and said second thickness is approximately more than 75% of said overall thickness.

27. The acetabular cup as set forth in claim 25 wherein said porous layer has a larger average pore size at said polar region than at said equatorial region.

28. The acetabular cup as set forth in claim 25 wherein said porous layer is thicker in said polar region than at said equatorial region.

29. The acetabular cup as set forth in claim 25 wherein said polar region has a first average pore size and said equatorial region has a second average pore size.

30. The acetabular cup as set forth in claim 25 wherein the pores are interconnected.

31. The acetabular cup as set forth in claim 25 wherein said porosity in the equatorial region is in the range from 5 to 200 μ

m and is in the range from 100 to 1000 μ

m in said equatorial region.

32. The acetabular cup as set forth in claim 25 wherein said porosity decreases along said outer shell surface on moving from said polar region to said equatorial region.

33. The acetabular cup as set forth in claim 31 wherein said porosity decreases continuously along said outer shell surface on moving from said polar region to said equatorial region.

34. The acetabular cup as set forth in claim 25 wherein said shell has at least one aperture therethrough.

35. The acetabular cup as set forth in claim 25 wherein the porosity of said outer layer decreases through said layer along a gradient normal to said surface.

36. The acetabular cup as set forth in claim 25 wherein the porosity of said outer layer decreases from said first porosity along a gradient normal to said surface through said first thickness.

37. The acetabular cup as set forth in claim 25 wherein the porosity of said outer layer decreases from said second porosity along a gradient normal to said surface through said second thickness.

38. The acetabular cup as set forth in claim 25 wherein said polar region average pore size is in the range from 300-1,000 μ

m and said equatorial region average pore size is in the range from 5-300 μ

m.

39. The acetabular cup as set forth in claim 25 wherein the combined thickness of said solid substrate layer and said porous layer is substantially the same in both said polar region and said equatorial region.

40. The acetabular cup as set forth in claim 31 wherein the rate of decrease of the porosity is linear.

41. The acetabular cup as set forth in claim 33 wherein said apertures are covered by a porous layer.

42. The acetabular cup as set forth in claim 1, wherein said shell is made from a metal selected from the group of titanium, titanium alloys, cobalt chrome alloys, stainless steel, niobium and tantalum.

43. The acetabular cup as set forth in claim 25, wherein said shell is made from a metal selected from the group of titanium, titanium alloys, stainless steel, chrome alloys, niobium and tantalum.

44. The acetabular cup as set forth in claim 1, wherein said porous outer layer is a porous metal foam network having an open cell structure wherein the openings of each cell are formed by metal webs, at least some of the webs covered with at least one layer of metal particles, the metal particles being bonded to the metal webs wherein the bonding is accomplished by sintering the metal particles to said webs.

45. The acetabular cup as set forth in claim 19, wherein said porous outer layer is a porous metal foam network having an open cell structure wherein the openings of each cell are formed by metal webs, at least some of the webs covered with at least one layer of metal particles, the metal particles being bonded to the metal webs wherein the bonding is accomplished by sintering the metal particles to said webs.

26. An acetabular cup comprising:

a bearing surface; and

a generally hemispherical shaped shell having an inner solid substrate layer and a porous outer bone contacting layer surrounding said bearing surface, said porous outer bone contacting layer having a first porosity adjacent an equatorial region of said shell and a second porosity adjacent a polar region of said shell, said second porosity being greater than said first porosity.

46. An orthopedic implant comprising:

an inner solid substrate layer and an overlying porous bone ingrowth layer, said layer comprising a porous outer trabecular bone contacting surface and a porous outer dense bone contacting surface and having a gradient of porosity through the depth of said porous bone ingrowth layer, said gradient defined by said porous bone ingrowth layer having a relatively lower porosity adjacent said substrate layer with respect to the porosity of said surfaces, said porous outer trabecular bone contacting surface having a first porosity and said porous outer dense bone contacting surface having a second porosity, said second porosity being less than said first porosity.

47. An orthopedic implant having a proximal to distal extent as defined by the implants intended installation in the human body comprising:

an inner solid substrate layer and an overlying porous bone ingrowth layer, said layer comprising a proximal porous outer bone contacting surface, an intermediate porous outer bone contacting surface and a distal porous outer bone contacting surface, said layer having a gradient of porosity through the depth of said porous bone ingrowth layer, said gradient defined by said porous bone ingrowth layer having a relatively lower porosity adjacent said substrate layer with respect to the porosity of said surfaces, said proximal porous outer bone contacting surface having a first porosity, said intermediate porous outer bone contacting surface having a second porosity, said distal porous outer bone contacting surface having a third porosity.

48. The orthopedic implant of claim 47 wherein said first porosity is greater than said third porosity.

49. The orthopedic implant of claim 47 wherein said third porosity is greater than said first porosity.

50. The orthopedic implant of claim 47 wherein said second porosity is greater than said first porosity.

51. The orthopedic implant of claim 47 wherein said second porosity is greater than said third porosity.

52. The orthopedic implant of claim 50 wherein said third porosity is greater than said second porosity.