Radiolucent bone graft

• US 6,846,327 B2
• Filed: 04/30/2002
• Issued: 01/25/2005
• Est. Priority Date: 05/01/2001
• Status: Expired due to Term

• Current Assignee: CTL Medical Corporation
• Original Assignee: Amedica Corporation
• Inventors: Khandkar, Ashok C., Rao, Mahendra S.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Priddy, Michael B.
• Application Number:
  US10/137,106
• Publication Number:
  US 20030009225A1
• Time in Patent Office: 1,001 Days
• Field of Search: 623/11.11, 623/16.11
• US Class Current: 623/16.11
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4603 for insertion or extraction of endoprosthetic joints or of accessories thereof
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30011 differing in porosity
• CPC Class Codes: A61F 2002/30016 differing in hardness, e.g. Vickers, Shore, Brinell
• CPC Class Codes: A61F 2002/30064 Coating or prosthesis-covering structure made of biodegradable material
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30166 H-shaped or I-shaped
• CPC Class Codes: A61F 2002/30179 X-shaped
• CPC Class Codes: A61F 2002/30224 cylindrical
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/30266 wedge-shaped parallelepipeds
• CPC Class Codes: A61F 2002/3028 polyhedral different from parallelepipedal and pyramidal
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30616 : Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30677 : Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30733 : Inserts placed into an endoprosthetic cavity, e.g. for modifying a material property
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30777 : Oblong apertures
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/3082 : Grooves
• CPC Class Codes: A61F 2002/30822 : Circumferential grooves
• CPC Class Codes: A61F 2002/30827 : Plurality of grooves
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30881 : Circumferential ribs, flanges or fins
• CPC Class Codes: A61F 2002/30891 : Plurality of protrusions
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/30896 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/3092 : having an open-celled or open-pored structure
• CPC Class Codes: A61F 2002/30968 : Sintering
• CPC Class Codes: A61F 2002/4627 : with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2002/4648 : Means for culturing bone graft
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0028 : Shapes in the form of latin or greek characters
• CPC Class Codes: A61F 2230/0058 : X-shaped
• CPC Class Codes: A61F 2230/0063 : Three-dimensional shapes
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0019 : differing in hardness, e.g. Vickers, Shore, Brinell
• CPC Class Codes: A61F 2250/0023 : differing in porosity
• CPC Class Codes: A61F 2310/00203 : containing alumina or aluminium oxide
• CPC Class Codes: A61F 2310/00239 : containing zirconia or zirconium oxide ZrO2
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: A61F 2310/00928 : Coating or prosthesis-covering structure made of glass or of glass-containing compounds, e.g. of bioglass
• CPC Class Codes: A61F 2310/0097 : Coating or prosthesis-covering structure made of pharmaceutical products, e.g. antibiotics
• CPC Class Codes: A61F 2310/00976 : Coating or prosthesis-covering structure made of proteins or of polypeptides, e.g. of bone morphogenic proteins BMP or of transforming growth factors TGF
• CPC Class Codes: A61L 2430/02 : for reconstruction of bones; weight-bearing implants
• CPC Class Codes: A61L 2430/38 : for reconstruction of the spine, vertebrae or intervertebral discs
• CPC Class Codes: A61L 27/10 : Ceramics or glasses
• CPC Class Codes: A61L 27/30 : Inorganic materials
• CPC Class Codes: A61L 27/32 : Phosphorus-containing materials, e.g. apatite
• CPC Class Codes: A61L 27/3608 : Bone, e.g. demineralised bone matrix [DBM], bone powder
• CPC Class Codes: A61L 27/365 : Bones
• CPC Class Codes: A61L 27/3804 : characterised by specific cells or progenitors thereof, e.g. fibroblasts, connective tissue cells, kidney cells
• CPC Class Codes: A61L 27/3834 : Cells able to produce different cell types, e.g. hematopoietic stem cells, mesenchymal stem cells, marrow stromal cells, embryonic stem cells
• CPC Class Codes: A61L 27/3847 : Bones
• CPC Class Codes: A61L 27/56 : Porous materials, e.g. foams or sponges

Abstract

An improved ceramic bone graft is provided for human implantation, particularly such as a spinal fusion cage for implantation into the inter-vertebral space between two adjacent vertebrae. The improved spinal fusion cage includes a substrate block of high strength ceramic having a selected size and shape to fit the anatomical space, and a controlled porosity analogous to natural bone. The substrate block is coated with a bio-active surface coating material such as hydroxyapatite or a calcium phosphate to promote bone ingrowth and enhanced bone fusion. Upon implantation, the fusion cage provides a spacer element having a desired combination of mechanical strength together with osteoconductivity and osteoinductivity to promote bone ingrowth and fusion, as well as radiolucency for facilitated post-operative monitoring. The fusion cage may additionally carry one or more natural or synthetic therapeutic agents for further promoting bone ingrowth and fusion.

Claims

1. A bone graft, comprising:

a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone, said porous ceramic substrate block having a first region of relatively low porosity substantially mimicking natural cortical bone, and a second region of relatively high porosity substantially mimicking cancellous patient bone; and

a bio-active and resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone.

2. The bone graft of claim 1 wherein said porous ceramic substrate block comprises a ceramic structure formed from alumina, zirconia, or composition thereof.

3. The bone graft of claim 2 wherein said porous ceramic substrate block comprises an alumina-zirconia composition having an alumina to zirconia ratio ranging from about 100% to about 25%.

4. The bone graft of claim 2 wherein said porous ceramic substrate block comprises an alumina-zirconia composition having from about 10% to about 25% zirconia in alumina.

5. The bone graft of claim 1 wherein said porous ceramic substrate block is formed from a material with a flexural strength greater than about 500 mega-Pascals, and a fracture toughness greater than about 5 mega-Pascal root meter.

6. The bone graft of claim 1 wherein said porous ceramic substrate block has a porosity ranging from about 2% to about 80% by volume, and further wherein the pore size ranges from about 5 microns to about 1,500 microns.

7. The bone graft of claim 6 wherein said porosity ranges from about 10% to about 50% by volume, and wherein the pore sizes range from about 100 microns to about 500 microns.

8. The bone graft of claim 1 wherein said first region has a porosity of less than about 5%, and wherein said second region has a porosity ranging from about 30% to about 80%.

9. The bone graft of claim 1 wherein said substrate block further includes means for facilitated grasping and manipulation with a surgical instrument for implantation.

10. The bone graft of claim 1 wherein said bio-active surface coating is selected from the group consisting of hydroxyapatite and calcium compounds.

11. The bone graft of claim 1 wherein said bio-active surface coating comprises an organic coating material.

12. The bone graft of claim 11 wherein said organic coating material is selected from the group consisting of autologous bone marrow aspirates, bone morphogenic proteins, growth factors and progenitor cells, and mixtures thereof.

13. The bone graft of claim 12 wherein said progenitor cells include mesenchymal stem cells, hematopoietic cells, and embryonic stem cells.

14. The bone graft of claim 1 wherein said porous ceramic substrate block is substantially radiolucent.

15. The bone graft of claim 1 further including a therapeutic agent carried by said substrate block.

16. The bone graft of claim 15 wherein said therapeutic agent comprises a natural or synthetic osteoconductive or osteoinductive agent.

17. The bone graft of claim 1 wherein said substrate block has a rough exterior surface.

18. The bone graft of claim 1 wherein said substrate block has a ribbed exterior surface.

19. The bone graft of claim 1 wherein said substrate block has a laterally open bore formed therein, and further including an osteoconductive material supported within said bore.

20. The bone graft of claim 19 wherein said osteoconductive material comprises morselized bone graft material.

21. A bone graft, comprising:

a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone, said porous ceramic substrate block having a variable porosity gradient substantially mimicking natural cortical and cancellous bone; and

a bio-active and resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone.

22. A bone graft, comprising:

a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone; and

a bio-active and resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone;

said bio-active surface coating being internally and externally applied to said porous ceramic substrate block.

23. A bone graft, comprising:

a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone; and

a bio-active and resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone;

said bio-active surface coating comprising a partially or fully amorphous osteoinductive material including a glass and osteoinductive calcium compound.

24. A bone graft, comprising:

a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone; and

a bio-active and resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone;

the pores formed within said substrate block being in substantially open fluid communication sufficient to transmit fluid pressure therebetween.

25. A bone graft for implantation between and fusion with adjacent bone, comprising:

a substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone, said substrate block having a first region of relatively low porosity substantially mimicking natural cortical bone, and a second region of relatively high porosity substantially mimicking cancellous patient bone; and

a bio-active and relatively rapidly resorbable surface coating applied to said substrate block, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with the adjacent bone;

said substrate block being relatively nonresorbable or resorbable at a rate substantially less than said surface coating.

26. A bone graft method, comprising the steps of:

forming a porous ceramic substrate block having a relatively high strength corresponding substantially with natural cortical and cancellous bone;

applying a bio-active and resorbable surface coating to said substrate block to form a bone graft implant, said surface coating having osteoconductive and osteoinductive properties to promote interbody bone ingrowth and fusion attachment with adjacent patient bone; and

surgically implanting the bone graft implant within a patient at a selected bone regeneration/ingrowth site.

27. The bone graft method of claim 26 wherein the porous ceramic substrate block comprises a ceramic structure formed from alumina, zirconia, or composition thereof.

28. The bone graft method of claim 26 wherein said substrate block forming step comprises forming the substrate block with a porosity ranging from about 2% to about 80% by volume, and further with a pore size ranging from about 5 microns to about 1,500 microns.

29. The bone graft method of claim 28 wherein said porosity ranges from about 10% to about 50% by volume, and wherein the pore sizes range from about 100 microns to about 500 microns.

30. The bone graft method of claim 26 wherein said substrate block forming step comprises forming the substrate block with a variable porosity gradient substantially mimicking natural cortical and cancellous bone.

31. The bone graft method of claim 26 wherein said substrate block forming step comprises forming the substrate block with a first region of relatively low porosity substantially mimicking natural cortical bone, and a second region of relatively high porosity substantially mimicking cancellous patient bone.

32. The bone graft method of claim 26 wherein said step of applying the bio-active surface coating comprises applying the bio-active surface coating internally and eternally to the substrate block.

33. The bone graft method of claim 26 wherein the bio-active surface coating is selected from the group consisting of hydroxyapatite and calcium compounds.

34. The bone graft method of claim 26 wherein the bio-active surface coating comprises a partially or fully amorphous osteoinductive material including a glass and osteoinductive calcium compound.

35. The bone graft method of claim 26 wherein the bio-active surface coating comprises an organic coating material.

36. The bone graft method of claim 35 wherein the organic coating material is selected from the group consisting of autologous bone marrow aspirates, bone morphogenic proteins, growth factors and progenitor cells, and mixtures thereof.

37. The bone graft method of claim 36 wherein said progenitor cells include mesenchymal stem cells, hematopoietic cells, and embryonic stem cells.

38. The bone graft method of claim 26 wherein the porous ceramic substrate block is substantially radiolucent.

39. The bone graft method of claim 26 further including the step of adding a therapeutic agent to the substrate block.

40. The bone graft method of claim 39 wherein said step of adding the therapeutic agent is subsequent to said step of applying the bio-active surface coating.

41. The bone graft method of claim 39 wherein the therapeutic agent comprises a natural or synthetic osteoconductive or osteoinductive agent.

42. The bone graft method of claim 39 wherein the therapeutic agent is selected from the group consisting of autologous bone marrow aspirates, bone morphogenic proteins, growth factors and progenitor cells, and mixtures thereof.

43. The bone graft method of claim 42 further including the steps of extracting the therapeutic agent from a patient, and culturing the therapeutic agent in vitro using the bone graft implant as a culture medium and substrate prior to said implanting step.

44. A bone graft method, comprising the steps of:

forming a porous ceramic bone graft implant;

extracting from a patient a therapeutic agent selected from the group consisting of autologous bone marrow aspirates, bone morphogenic proteins, growth factors and progenitor cells, and mixtures thereof;

culturing the therapeutic agent in vitro using the bone graft implant as a culture medium and substrate prior to implanting; and

surgically implanting the bone graft implant within a patient at a selected bone regeneration/ingrowth site.

45. The bone graft method of claim 44 wherein the progenitor cells are mesenchymal stem cells, hematopoietic stem cells, embryonic stem cells, or a combination thereof.