CA2439278A1 - Demineralized bone-derived implants - Google Patents

Abstract

Selectively demineralized bone-derived implants are provided. In one embodiment, a bone sheet for implantation includes a demineralized field surrounding mineralized regions. In another embodiment, a bone defect filler includes a demineralized cancellous bone section in a first geometry. The first geometry is compressible and dryable to a second geometry smaller than the first geometry, and the second geometry is expandable and rehydratable to a third geometry larger than the second geometry.

Claims (89)

1. A bone sheet for implantation, the sheet comprising an at least partially demineralized field substantially surrounding at least one mineralized region.

2. The bone sheet according to claim 1 having at least one rib providing localized thickness to the sheet.

3. The bone sheet according to claim 1, wherein the sheet is formed of cortical bone.

4. The bone sheet according to claim 3 wherein the sheet comprises a plurality of mineralized regions.

5. The bone sheet according to claim 4 wherein at least two of the mineralized regions are connected by a strut.

6. The bone sheet according to claim 3, wherein the at least one mineralized region defines at least one hole in the sheet.

7. The bone sheet according to claim 6, wherein the at least one hole is configured and dimensioned to receive at least one fastener.

8. The bone sheet according to claim 3, wherein the sheet has a thickness of between about 0.5 mm and about 3 mm.

9. A method of forming a flexible bone sheet comprising:
providing a sheet of cortical bone;
creating at least one hole in the cortical sheet which is configured and dimensioned to receive a fastener;
masking the cortical sheet proximate the at least one hole to create a masked region surrounding the at least one hole; and applying demineralizing agents to the cortical sheet around the masked region.

10. The method according to claim 9, wherein a plurality of masking elements are removably attached to the sheet to provide masking proximate the at least one hole.

11. The method according to claim 9, wherein the masking is provided by at least one of the group consisting of tape, paint, and a coating.

12. The method according to claim 9, further comprising creating perforations in the sheet that are substantially smaller than the at least one hole.

13. The method according to claim 9, further comprising cutting a bone section along a spiral path.

14. A sheet formed of bone comprising two or more strips of bone each having a bone grain orientation, wherein the bone grain orientation of at least one strip is disposed transverse to the grain orientation of another strip.

15. The sheet according to claim 14, wherein the strips are interwoven.

16. The sheet according to claim 14, wherein the strips are selected from at least one of the group consisting of mineralized bone, demineralized bone, and partially demineralized bone.

17. The sheet according to claim 14, wherein a portion of at least one strip is at least partially demineralized.

18. The sheet according to claim 14, wherein the strips are interwoven to form a plurality of generally parallel rows and a plurality of generally parallel columns.

19. The sheet according to claim 14, wherein the strips have a width between about 1 mm and about 6 mm.

20. The sheet according to claim 19, wherein the strips have a thickness of between about 0.5 mm and about 2 mm.

21. The sheet according to claim 14, wherein the strips have a width of about 5 mm and a thickness of about 1 mm.

22. The sheet according to claim 14, wherein the bone strips are unitary in construction.

23. The sheet according to claim 14, wherein at least one strip is formed by braiding two or more bone fibers.

24. The sheet according to claim 14, wherein each bone strip has a longitudinal axis and the bone grain orientation is substantially parallel thereto.

25. A method of providing a bone implant comprising:
demineralizing a cancellous bone section having a first geometry;
compressing the bone section from the first geometry to a second geometry smaller than the first geometry;
drying the bone section while the bone section has approximately the second geometry; and inserting the bone section into a space.

26. The method of claim 25, wherein when the bone section is inserted into the space, the bone section is at least partially surrounded by a wall while having approximately the second geometry.

27. The method of claim 25, further comprising:
expanding the bone section from the second geometry to a third geometry larger than the second geometry.

28. The method of claim 27, wherein the bone section is expanded by rehydrating.

29. The method of claim 27, further comprising allowing the bone section to expand to contact the wall.

30. A method of maintaining a distance between vertebral bodies comprising:
demineralizing a bone section having a first geometry;
drying the bone section;
inserting the bone section in between vertebral bodies; and expanding the bone section to a second geometry.

31. The method of claim 30, wherein the bone section is demineralized cortical bone.

32. The method of claim 30, wherein the drying step comprises freeze drying the bone section.

33. The method of claim 30, wherein the bone section is expanded by hydrating.

34. The method of claim 30, further comprising compressing the bone section.

35. The method of claim 34, wherein the bone section is cancellous bone.

36. The method of claim 30 used to replace the nucleus of a vertebral disc.

37. A method of replacing nucleus of a vertebral disc comprising:
providing a demineralized cortical bone section having a first geometry;
inserting the bone section in between vertebral bodies; and expanding the bone section to a second geometry.

38. The method of claim 37, wherein the bone section is expanded by hydrating.

39. The method of claim 37, wherein the bone section is expanded to a height in the second geometry which is larger than the height in the first geometry.

40. The method of claim 37, wherein the bone section in the second geometry has a top surface and a bottom surface, each of the top and bottom surfaces being configured to approximately match a concave vertebral endplate.

41. The method of claim 40, wherein the top and bottom surfaces are convex with a radius of between about 50 min and about 70 mm.

42. An implant comprising demineralized cancellous bone capable of being softened and compressed into a smaller first shape and hardened in said first shape, and capable of expanding into a second shape larger than said first shape when resoftened and permitted to expand.

43. The implant of claim 42, wherein said bone is softened by hydration.

44. The implant of claim 42, wherein said bone is hardened by dehydration.

45. The implant of claim 42, wherein said bone is configured and dimensioned to by received in an anatomical void.

46. The implant of claim 45, wherein said first shape is smaller than said anatomical void.

47. The implant of claim 46, wherein said second shape is about the same as the shape of said anatomical void.

48. The implant of claim 46, wherein said second shape spans a lateral dimension of said anatomical void.

49. The implant of claim 42, further comprising cortical bone.

50. The implant of claim 49, wherein the implant is configured and dimensioned to be disposed in a burr hole or void in the cranial region of the skull.

51. The implant of claim 50, wherein the implant forms a burr hole cap comprising an upper cortical bone section and a lower, demineralized cancellous bone section, at least the lower section being sized to fill the burr hole when in the expanded second shape.

52. The implant of claim 50, wherein the implant is generally T-shaped and comprises an upper cortical bone section and a lower, demineralized cancellous bone section.

53. The implant of claim 52, wherein in the expanded second shape, at least the lower section is sized to contact walls of the void.

54. The implant of claim 52, wherein the upper section has an arcuate portion for generally matching the contour of the skull.

55. The implant of claim 49, further comprising slits extending through at least a portion of one or both of the cortical bone and cancellous bone.

56. A cranial void filler comprising:
an upper mineralized cortical bone section, and a lower, at least partially demineralized cortical bone section, wherein the lower section is adapted and configured to contact walls of a cranial void.

57. The cranial void filler of claim 56, wherein the upper and lower sections form a T-shape.

58. The cranial void filler of claim 56, further comprising at least one slit extending through at least a portion of at least one of the upper and lower sections.

59. The cranial void filler of claim 56, wherein at least one slit extends through a portion of the upper section and at least one slit extends through the lower section.

60. The cranial void filler of claim 59, wherein the at least one slit in the lower section is colinear with the slit in the upper section.

61. The cranial void filler of claim 56, wherein the upper section has a rounded upper surface portion.

62. The cranial void filler of claim 56, wherein the upper section has a curved lower surface portion.

63. A plate comprising:
a unitary body with a pair of portions having a first width and a central portion disposed therebetween having a second width, the first width being greater than the second width, and the body being formed of cortical bone; and at least one partially demineralized region, wherein the at least one partially demineralized region confers flexibility to the plate.

64. The plate of claim 63, further comprising a plurality of fastener holes.

65. The plate of claim 64, wherein the body has a central longitudinal axis and a first at least partially demineralized region that is coaxial therewith.

66. The plate of claim 65, wherein the first at least partially demineralized region extends substantially across the entire length of the body.

67. The plate of claim 65, wherein the fastener holes are disposed proximate ends of the body.

68. The plate of claim 67, wherein the fastener holes are disposed on a central longitudinal axis, and a first at least partially demineralized region is coaxial therewith.

69. The plate of claim 68, wherein a at least a second at least partially demineralized region is disposed transverse to the first at least partially demineralized region.

70. The plate of claim 69, wherein the at least second at least partially demineralized region is generally perpendicular to the first at least partially demineralized region.

71. The plate of claim 70, wherein the at least second at least partially demineralized region intersects at least one fastener hole.

72. The plate of claim 63, wherein the body is relatively thin compared to its length or width.

73. The plate of claim 63, wherein the at least one partially demineralized region extends substantially across the second width.

74. The plate of claim 73, wherein the body has a central longitudinal axis and the at least partially demineralized region extends transverse to the central longitudinal axis.

75. The plate of claim 74, further comprising a plurality of fastener holes.

76. The plate of claim 63, wherein the body is generally dogbone shaped.

77. The plate of claim 63, wherein the body has a central longitudinal axis, and the length of the body along the central axis is between about 10 mm and about 20 mm.

78. The plate of claim 77, wherein the first width is between about 4 mm and about 7 mm.

79. The plate of claim 78, wherein the body has a thickness between about 1 mm and about 3 mm.

80. The plate of claim 78, wherein the body has a length of about 15 mm, a first width of about 5 mm, and a thickness of about 2 mm.

81. An implant comprising a unitary section of cortical bone having a first portion that is mineralized and a second portion that is at least partially demineralized, wherein the mineralized portion includes a plurality of slits to facilitate bending of the unitary section.

82. A method of forming an implant comprising:
obtaining cortical fibers;
at least partially demineralizing the fibers;
allowing the fibers to clump together; and allowing the fibers to dry in a clumped state.

83. The method of claim 82, wherein the fibers are allowed to dry in a mold.

84. The method.of claim 83, further comprising pressing the fibers while the fibers are clumped together.

85. The method of claim 82, wherein the fibers are obtained by milling.

86. An implant for maintaining a space in a bisected vertebrae comprising:
a cortical bone cord having a first and second free ends adapted for engaging exposed portions of the lamina, and a region positioned between the first and second ends, wherein the region is at least partially demineralized to provide flexibility.

87. The implant of claim 86, wherein the free ends are mineralized.

88. The implant of claim 86, wherein the cord further comprises a pair of at least partially demineralized regions with a mineralized central region therebetween.

89. The implant of claim 86, wherein the at least partially demineralized region is centrally located between mineralized free ends.