Lordotic interbody spinal fusion implants

• US 6,447,544 B1
• Filed: 10/04/1999
• Issued: 09/10/2002
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Gary K. Michelson
• Inventors: Michelson, Gary Karlin
• Primary Examiner(s): Isabella, David J.
• Assistant Examiner(s): Chattopadhyay, Urmi
• Application Number:
  US09/412,090
• Time in Patent Office: 1,072 Days
• Field of Search: 623/17.16, 623/17, 606/60, 606/61, 606/594
• US Class Current: 623/17.16
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• 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 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• 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 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/3037 Translation along the common longitudinal axis, e.g. piston
• CPC Class Codes: A61F 2002/30398 Sliding
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30556 for adjusting thickness
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30599 : stackable
• CPC Class Codes: A61F 2002/30604 : modular
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30777 : Oblong apertures
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/30797 : internally-threaded
• CPC Class Codes: A61F 2002/30836 : knurled
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30843 : Pyramidally-shaped
• CPC Class Codes: A61F 2002/30904 : serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2002/3092 : having an open-celled or open-pored structure
• CPC Class Codes: A61F 2002/4485 : comprising three or more adjacent spinal implants
• CPC Class Codes: A61F 2002/449 : comprising multiple spinal implants located in different intervertebral spaces or in different vertebrae
• CPC Class Codes: A61F 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2210/0004 : bioabsorbable
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0009 : for adjusting thickness
• CPC Class Codes: A61F 2250/0063 : Nested prosthetic parts
• 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: Y10S 606/90 : Lumbar stabilizer
• CPC Class Codes: Y10S 606/907 : Composed of particular material or coated
• CPC Class Codes: Y10S 606/908 : Bioabsorbable material

Abstract

The present application is directed to interbody spinal fusion implants having a structural configuration that provides for the maintaining and creating of the normal anatomic angular relationship of two adjacent vertebrae of the spine to maintain and create spinal lordosis. The spinal fusion implants are sized to fit within the disc space created by the removal of disc material between two adjacent vertebrae and conform wholly or in part to the disc space created. The spinal fusion implants of the present invention have upper and lower surfaces that form a support structure for bearing against the end plates of the adjacent vertebrae. The upper and lower surfaces are disposed in a converging angular relationship to each other such that the implants have an overall “wedged-shape” in an elevational side view. The angular relationship of the upper and lower surfaces places and maintains the vertebrae adjacent to those surfaces in an angular relationship to each other, creating and maintaining the desired lordosis.

Claims

1. An artificial interbody spinal fusion implant for insertion within an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine, the vertebral bodies having an anterior aspect and a posterior aspect therebetween, said implant comprising:

a leading end for insertion first into the disc space and a trailing end opposite said leading end, a mid-longitudinal axis, and a depth along said mid-longitudinal axis;

a top and a bottom between said leading and trailing ends adapted to space apart the adjacent vertebral bodies, a height between said top and said bottom, said top and said bottom having at least one opening therethrough, said openings being in communication with one another to permit for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said top and said bottom being in an angular relationship to each other along at least a portion of the depth of said implant sufficient to maintain the adjacent vertebral bodies in an angular relationship to each other, said top and said bottom each having an interior surface oriented toward one another, said interior surfaces being spaced apart to define a hollow interior in communication with said openings; and

opposite sides between said top and said bottom, and between said leading and trailing ends, a width between said opposite sides, and a maximum width of said implant being larger than a maximum height of said implant.

2. The implant of claim 1, wherein said implant includes an access opening for accessing said hollow interior.

3. The implant of claim 2, wherein said access opening is larger than the largest of said openings.

4. The implant of claim 2, wherein said access opening is configured to permit insertion of osteogenic material into said hollow interior.

5. The implant of claim 4, wherein said osteogenic material includes a fusion promoting material.

6. The implant of claim 4, wherein said osteogenic material is bone.

7. The implant of claim 4, wherein said osteogenic material is a material other than bone.

8. The implant of claim 2 further comprising a cover for closing said access opening.

9. The implant of claim 8, wherein said cover cooperatively engages said access opening.

10. The implant of claim 9, wherein said cover comprises a slidable door.

11. The implant of claim 1, wherein said top and said bottom further comprise it least a second opening.

12. The implant of claim 1, wherein at least one of said openings are approximately 1 mm to 3 mm in diameter.

13. The implant of claim 1, wherein at least one of said openings is macroscopic in size.

15. The implant of claim 1, wherein at least one opening in said top and at least one opening in said bottom form a channel through said implant.

16. The implant of claim 1, wherein said trailing end includes at least one perforation.

17. The implant of claim 1 having a plurality of openings capable of retaining fusion promoting material.

18. The implant of claim 1, wherein said sides have at least one aperture.

19. The implant of claim 1, wherein said at least one aperture is sized in the range of approximately 1 mm to 3 mm.

20. The implant of claim 18, wherein said at least one aperture is in communication with said openings in said top and said bottom.

21. The implant of claim 1, wherein the junctions of said sides and at least one of said trailing end and said leading end are rounded.

22. The implant of claim 1, wherein said sides are generally parallel to one another.

23. The implant of claim 1, wherein said sides are generally flat.

24. The implant of claim 1, wherein said sides are curved.

25. The implant of claim 1, wherein the shape of said sides is generally trapezoidal.

26. The implant of claim 1, wherein said implant is configured to generally taper from said trailing end to said leading end.

27. The implant of claim 1, wherein each of said top and bottom have a length greater than the depth of said implant along the mid-longitudinal axis.

28. The implant of claim 1, wherein said implant is a wedge.

29. The implant of claim 1, wherein said implant has a width that is approximately 32 mm for use in the lumbar spine.

30. The implant of claim 1, wherein said implant has a width in the range of approximately 28 mm to 48 mm for use in the lumbar spine.

31. The implant of claim 1, wherein said implant has a generally rectangular cross section transverse to the mid-longitudinal axis along at least a portion of its depth.

32. The implant of claim 1, wherein said leading end is at least in part curved.

33. The implant of claim 1, wherein at least a portion of said leading end is tapered for facilitating insertion of said implant between the two adjacent vertebral bodies.

34. The implant of claim 1, wherein said leading end is curved.

35. The implant of claim 34, wherein said leading end generally conforms to the disc space proximate the posterior aspect of the vertebral bodies.

36. The implant of claim 1, wherein said leading end is convex.

37. The implant of claim 1, wherein said trailing end is curved.

38. The implant of claim 1, wherein said trailing end is convex.

39. The implant of claim 1, wherein the maximum depth of said implant is less than the posterior to anterior depth of the end plates of the adjacent vertebral bodies.

40. The implant of claim 1, wherein said implant is adapted for insertion from the anterior aspect of the vertebral bodies.

41. The implant of claim 1, wherein said implant is sized to replace a substantial portion of the disc with a single implant.

42. The implant of claim 1, wherein said implant has substantially the same shape as a space created by the removal of at least a substantial portion of the nucleus pulposus and a portion of the annulus fibrosus from between the two adjacent vertebral bodies.

43. The implant of claim 1, wherein said implant has a height substantially equal to the height of the space created by the removal of disc material from between the adjacent vertebral bodies.

44. The implant of claim 1, wherein said implant has substantially the same height, width and depth as a space created by the removal of at least generally the nucleus pulposus and at least a portion of the annulus fibrosus from between the two adjacent vertebral bodies.

45. The implant of claim 1, wherein said implant dimensionally corresponds to the space created by the removal of at least generally all of the nucleus pulposus and a portion of the annulus fibrosus when said adjacent vertebral bodies are distracted and placed in angular relationship to each other.

46. The implant of claim 1, wherein the depth of said implant is in the range of approximately 11 mm to 21 mm for use in the cervical spine.

47. The implant of claim 1, wherein the width of said implant is in the range of approximately 14 mm to 28 mm for use in the cervical spine.

48. The implant of claim 1, wherein said implant has the maximum height in the range of approximately 5 mm to 10 mm, the maximum width in the range of approximately 14 mm to 28 mm, and a depth in the range of approximately 11 mm to 21 mm for use in the cervical spine.

49. The implant of claim 1 for use in the lumbar spine, wherein the depth of aid implant is in the range of approximately 20 mm to 34 mm.

50. The implant of claim 1, wherein said implant has the maximum height in the range of approximately 8 mm to 16 mm, the maximum width in the range of approximately 28 mm to 48 mm, and depth in the range of approximately 20 mm to 34 mm for use in the lumbar spine.

51. The implant of claim 1, wherein the depth of said implant is substantially the same as the depth of a space created by the removal of the nucleus pulposus from between the two adjacent vertebral bodies.

52. The implant of claim 1, wherein the width of said implant is substantially equal to the transverse width of a space created by the removal of the nucleus pulposus from between the two adjacent vertebral bodies.

53. The implant of claim 1, wherein said top has a fixed shape which is generally configured to match the contours of the endplate of one of the two adjacent vertebral bodies.

54. The implant of claim 1, wherein said bottom has a fixed shape which is generally configured to match the natural contours of the endplate of one of the two adjacent vertebral bodies.

55. The implant of claim 1, further comprising at least one protrusion extending from said top and said bottom for engaging the adjacent vertebral bodies to maintain said implant within the disc space.

56. The implant of claim 55, wherein said protrusion comprises a ridge.

57. The implant of claim 55, wherein said protrusion comprises a plurality of ridges facing the same direction to prevent expulsion of said implant in a direction opposite to said same direction.

58. The implant of claim 55, wherein said protrusion comprises a tooth.

59. The implant of claim 55, wherein said protrusion comprises a ratchet.

60. The implant of claim 59, wherein said protrusion comprises a plurality of ratchets facing the same direction to prevent expulsion of said implant in a direction opposite to said same direction.

61. The implant of claim 1, further comprising an irregular surface for engaging the adjacent vertebral bodies and for maintaining said implant in place, said irregular surface being present on at least a part of said top and said bottom.

62. The implant of claim 61, wherein said irregular surface comprises at least one groove.

63. The implant of claim 61, wherein said irregular surface includes knurling.

64. The implant of claim 61, wherein said irregular surface includes at least one spike.

65. The implant of claim 1, further comprising a plurality of surface roughenings for engaging said adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said top and said bottom.

66. The implant of claim 65, wherein said roughenings cover substantially the entire top and bottom of said implant, said roughenings being generally tapered from said trailing end to said leading end.

67. The implant of claim 65, herein a height of each roughening measured from the mid-longitudinal axis of the implant decreases from said trailing end to said leading end.

68. The implant of claim 65, wherein said surface roughenings comprise at least one groove.

69. The implant of claim 1, wherein said top and said bottom have a bone ingrowth surface.

70. The implant of claim 1, wherein said implant has an exterior surface that is at least in part porous.

71. The implant of claim 1, wherein said implant comprises a mesh-like material having a plurality of interstices for receiving fusion promoting material.

72. The implant of claim 1, wherein said implant is porous.

74. The implant of claim 1, in combination with a fusion promoting material other than bone at least in part within said hollow interior.

75. The implant of claim 1, wherein said implant comprises a bone ingrowth material other than bone.

76. The implant of claim 1, further comprising a material that intrinsically participates in the growth of bone from one of the adjacent vertebral bodies to the other of the adjacent vertebral bodies.

77. The implant of claim 1, wherein said implant is treated with a fusion promoting substance.

78. The implant of claim 77, wherein said fusion promoting substance is autogenous bone.

79. The implant of claim 1, wherein said implant is stronger than bone.

80. The implant of claim 1, further in combination with an osteogenic material at least in part within said hollow interior.

81. The implant of claim 80, wherein said osteogenic material is a material other than bone.

82. The implant of claim 1, wherein said implant comprises a bone ingrowth material for promoting bone ingrowth between said implant and said two adjacent vertebral bodies.

83. The spinal fusion implant of claim 1, wherein said implant is at least in part bioresorbable.

84. The implant of claim 1, wherein said implant is adapted to be centrally placed within the disc space.

85. The implant of claim 1, wherein at least one of said leading and trailing ends of said implant is configured to engage a driving instrument for implanting said implant within the disc space between the two adjacent vertebral bodies.

86. The implant of claim 1, further comprising an expander moving said top and bottom apart in said diverging angular relationship.

87. The implant of claim 1, wherein said trailing end has a height greater than said leading end.

88. The implant of claim 1, wherein at least one of said top and bottom is substantially flat.

89. The implant of claim 88, further comprising an irregular surface for engaging the adjacent vertebral bodies and for maintaining said implant in place, said irregular surface being present on at least a part of said top and said bottom.

90. The implant of claim 89, wherein said irregular surface comprises at least one groove.

91. The implant of claim 89, wherein said irregular surface includes knurling.

92. The implant of claim 88, further comprising a plurality of surface roughenings for engaging said adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said top and said bottom.

93. The implant of claim 92, wherein said roughenings cover substantially the entire top and bottom of said implant, said roughenings being generally tapered from said trailing end to said leading end.

94. The implant of claim 1, wherein at least one of said top and bottom is generally planar.

95. The implant of claim 94, further comprising an irregular surface for engaging the adjacent vertebral bodies and for maintaining said implant in place, said irregular surface being present on at least a part of said top and said bottom.

96. The implant of claim 95, wherein said irregular surface comprises at least one groove.

97. The implant of claim 95, wherein said irregular surface includes knurling.

98. The implant of claim 94, further comprising a plurality of surface roughenings for engaging said adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said top and said bottom.

99. The implant of claim 98, wherein said roughenings cover substantially the entire top and bottom of said implant, said roughenings being generally tapered from said trailing end to said leading end.

100. The implant of claim 1, wherein each of said top and bottom are substantially flat.

101. The implant of claim 100, further comprising an irregular surface for engaging the adjacent vertebral bodies and for maintaining said implant in place, said irregular surface being present on at least a part of said top and said bottom.

102. The implant of claim 101, wherein said irregular surface comprises at least one groove.

103. The implant of claim 101, wherein said irregular surface includes knurling.

104. The implant of claim 100, further comprising a plurality of surface roughenings for engaging said adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said top and said bottom.

105. The implant of claim 104, wherein said roughenings cover substantially the entire top and bottom of said implant, said roughenings being generally tapered from said trailing end to said leading end.

106. The implant of claim 1, wherein each of said top and bottom are generally planar.

107. The implant of claim 106, further comprising an irregular surface for engaging the adjacent vertebral bodies and for maintaining said implant in place, said irregular surface being present on at least a part of said top and said bottom.

108. The implant of claim 107, wherein said irregular surface comprises at least one groove.

109. The implant of claim 107, wherein said irregular surface includes knurling.

110. The implant of claim 106, further comprising a plurality of surface roughenings for engaging said adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said top and said bottom.

111. The implant of claim 110, wherein said roughenings cover substantially the entire top and bottom of said implant, said roughenings being generally tapered from said trailing end to said leading end.

112. The implant of claim 1, wherein said implant has a generally quadrilateral cross section transverse to the mid-longitudinal axis along at least a portion of its depth.

113. The implant of claim 1, wherein said implant is sized to replace a substantial portion of the disc with a single implant.

114. The implant of claim 1, in combination with a fusion promoting substance at least in part within said hollow interior.

115. The spinal fusion implant of claim 114, wherein said fusion promoting substance includes at least one of bone, bone morphogenetic protein, hydroxyapatite, and hydroxyapatite tricalcium phosphate.

14. An artificial interbody spinal fusion implant for insertion within an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine, the vertebral bodies having an anterior aspect and a posterior aspect therebetween, said implant comprising:

a leading end for insertion first into the disc space and a trailing end opposite said leading end, a mid-longitudinal axis, and a depth along said mid-longitudinal axis;

a top and a bottom between said leading and trailing ends adapted to be placed within the disc space to contact and support space apart the adjacent vertebral bodies, a height between said top and said bottom, said top and said bottom having at least one opening therethrough, said openings being in communication With one another to permit for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said top and said bottom being in an angular relationship to each other along at least a portion of the depth of said implant sufficient to maintain the adjacent vertebral bodies in an angular relationship to each other, said top and said bottom each having an interior surface oriented toward one another, said interior surfaces being spaced apart to define a hollow interior in communication with said openings, and

wherein at least one of said openings is microscopic in size.

73. An artificial interbody spinal fusion implant for insertion within an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine, the vertebral bodies having an anterior aspect and a posterior aspect therebetween, said implant comprising:

a leading end for insertion first into the disc space and a trailing end opposite said leading end, a mid-longitudinal axis, and a depth along said mid-longitudinal axis;

a top and a bottom between said leading and trailing ends adapted to space apart the adjacent vertebral bodies, a height between said top and said bottom, said top and said bottom having at least one opening therethrough, said openings being in communication with one another to permit for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said top and said bottom being in an angular relationship to each other along at least a portion of the depth of said implant sufficient to maintain the adjacent vertebral bodies in an angular relationship to each other, said top and said bottom each having an interior surface, said interior surfaces being spaced apart to define a hollow interior in communication with said openings;

opposite sides between said top and said bottom, and between said leading and trailing ends, a width between said opposite sides, and a maximum width of said implant being larger than a maximum height of said implant; and

an exterior surface, at least a portion of which is treated to promote bone ingrowth between said surface and a vertebral body.

116. An artificial interbody spinal fusion implant for insertion within a disc space between adjacent vertebral bodies of a human spine, the vertebral bodies having an anterior aspect and a posterior aspect, said implant comprising:

a leading end for insertion first into the disc space and a trailing end opposite said leading end, a mid-longitudinal axis, and a depth along said mid-longitudinal axis;

a top and a bottom between said leading and trailing ends adapted to be placed within the disc space to contact and support the adjacent vertebral bodies, said top and said bottom having at least one opening therethrough, said openings being in communication with one another to permit for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said top and said bottom being in an angular relationship to each other along at least a portion of the depth of said implant sufficient to maintain the adjacent vertebral bodies in an angular relationship to each other, each of said top and said bottom having an interior surface, said interior surfaces being spaced apart to define a hollow interior in communication with said openings;

opposite sides between said top and said bottom, and between said leading and trailing ends;

an access opening for accessing said hollow interior; and

a cover for closing said access opening, said cover cooperatively engaging said access opening, said cover including a surface deviation to facilitate opening and closing of said access opening with said cover.