Frusto-conical interbody spinal fusion implants

• US 6,923,810 B1
• Filed: 06/07/1995
• Issued: 08/02/2005
• Est. Priority Date: 06/13/1988
• Status: Expired due to Term

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Inventors: Michelson, Gary Karlin
• Primary Examiner(s): REIP, DAVID OWEN
• Application Number:
  US08/484,928
• Time in Patent Office: 3,709 Days
• Field of Search: 606/60, 606/61, 633/16, 633/17, 633 1711- 1716
• US Class Current: 606/247
• CPC Class Codes: A61B 17/025 Joint distractors
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/1757 for the spine
• CPC Class Codes: A61B 17/32 Surgical cutting instruments A61B18/042 takes precedence; suture cutters A61B17/0467; instruments for ligaturing or cutting A61B17/128; instruments for rupturing the amniotic membrane A61B17/4208; specially adapted knives for eye surgery A61F9/0133
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61B 2017/922 Devices for impaction, impact element
• CPC Class Codes: A61B 2090/036 abutting on tissue or skin
• 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 2/30771 applied in original prostheses, e.g. holes or grooves
• 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 2/4603 for insertion or extraction of endoprosthetic joints or of accessories thereof
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• 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 2002/3013 figure-"8"- or hourglass-shaped
• CPC Class Codes: A61F 2002/30131 horseshoe- or crescent- or C-shaped or U-shaped
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30148 : lozenge- or diamond-shaped
• CPC Class Codes: A61F 2002/3021 : frustoconical
• CPC Class Codes: A61F 2002/30217 : hollow cones, e.g. tubular-like cones
• CPC Class Codes: A61F 2002/30224 : cylindrical
• CPC Class Codes: A61F 2002/30235 : tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30405 : made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30426 : Bayonet coupling
• CPC Class Codes: A61F 2002/30593 : hollow
• 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 2002/30795 : Blind bores, e.g. of circular cross-section
• CPC Class Codes: A61F 2002/30797 : internally-threaded
• CPC Class Codes: A61F 2002/30808 : parallel
• CPC Class Codes: A61F 2002/3081 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30836 : knurled
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30879 : Ribs
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/30894 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30904 : serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2002/30906 : shot- sand- or grit-blasted
• CPC Class Codes: A61F 2002/30909 : Nets
• CPC Class Codes: A61F 2002/448 : comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two 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 2002/4619 : for extraction
• CPC Class Codes: A61F 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2002/4649 : Bone graft or bone dowel harvest sites
• CPC Class Codes: A61F 2002/4681 : by applying mechanical shocks, e.g. by hammering
• 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 2230/001 : Figure-8-shaped, e.g. hourglass-shaped
• CPC Class Codes: A61F 2230/0013 : Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0067 : conical
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2250/0063 : Nested prosthetic parts
• 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 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00293 : containing a phosphorus-containing compound, e.g. apatite
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

The present invention is directed to a variety of interbody spinal fusion implants having at least a partially frusto-conical configuration. The spinal fusion implants of the present invention may be relatively solid or hollow and may have surface roughenings to promote bone ingrowth and stability. The spinal fusion implants of the present invention may have wells extending into the material of the implant from the surface for the purpose of holding fusion promoting materials and to provide for areas of bone ingrowth fixation. A variety of surface irregularities may be employed to increase implant stability and implant surface area, and/or for the purpose of advancing the spinal fusion implant into the fusion site.

Claims

1. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between adjacent vertebral bodies of a human spine, the implant comprising:

a body having a mid-longitudinal axis, an insertion end, a trailing end, a length between said ends, an upper portion adapted to be oriented toward one of the adjacent vertebral bodies, a lower portion adapted to be oriented toward the other of the adjacent vertebral bodies, and a height between said upper portion and said lower portion transverse to the length, the height of said upper and lower portions along a portion of the length of said implant being constant, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant; and

a non-threaded bone engaging means extending from at least a portion of said upper and lower portions adapted to engage said implant to the adjacent vertebral bodies of the spine when implanted in the spine, said bone engaging means having a maximum height that increases from one of said ends to the other of said ends along at least a portion of the length of said body where the height of said upper and lower portions is constant, said implant being made of a material appropriate for human implantation.

2. The spinal fusion implant of claim 1 in which said body includes two opposed sides between said upper and lower portions, said sides being planar along at least a portion of the length r.

3. The spinal fusion implant of claim 1 in which said upper and lower surfaces form at least a portion of a cylinder.

4. The spinal fusion implant of claim 1 in which said implant comprises a bone ingrowth material.

5. The spinal fusion implant of claim 1 in which said implant comprises a fusion promoting material.

6. The spinal fusion implant of claim 1 in which said implant is at least in part bioabsorbable.

7. The spinal fusion implant of claim 1 in which said body has a plurality of openings adapted to retain fusion promoting material.

8. The spinal fusion implant of claim 1 in which said bone engaging means includes an outer surface that is at least in part porous.

9. The spinal fusion implant of claim 1 in which said bone engaging means comprises a plurality of posts spaced apart along at least a portion of the outer surface of said body.

10. The spinal fusion implant of claim 9 in which said plurality of posts have a head portion and a stem portion, said head portion having a wider diameter than said stem portion.

11. The spinal fusion implant of claim 1 in which said bone engaging means comprises a mesh-like material having a plurality of interstices for receiving fusion promoting material.

12. The spinal fusion implant of claim 1 in which said bone engaging means includes a plurality of surface roughenings for engaging the adjacent vertebral bodies and for maintaining said implant in place, said surface roughenings being present on at least a portion of said outer surface of said implant.

13. The spinal fusion implant of claim 12 in which said surface roughenings include a plurality of ratchetings.

14. The spinal fusion implant of claim 12 in which said surface roughenings include knurling.

15. The spinal fusion implant of claim 1 in which said body has an internal chamber and means for accessing said internal chamber.

16. The spinal fusion implant of claim 15 in which said internal chamber is capable of containing fusion promoting material.

17. The spinal fusion implant of claim 15 in which said body includes a wall surrounding said internal chamber.

18. The spinal fusion implant of claim 17 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

19. The spinal fusion implant of claim 15 in which said body has a cap for closing said accessing means.

20. The spinal fusion implant of claim 1 in which said implant includes an engagement means for engaging instrumentation for the insertion of said implant.

21. The spinal fusion implant of claim 1 in which at least a portion of said outer surface comprises wells having at least partial walls.

22. The spinal fusion implant of claim 1 in which said implant is configured to be placed in close proximity in a side by side alignment to a second spinal fusion implant, said first and second implants when placed together having a combined overall width that is less than the sum of the individual maximum diameters of each of said first and second implants.

23. The spinal fusion implant of claim 1 in which said body has at least one truncated side forming a planar surface parallel to the mid-longitudinal axis.

24. The spinal fusion implant of claim 1, in combination with a fusion promoting material.

25. The spinal fusion implant of claim 24, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

26. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between two adjacent vertebral bodies of a human spine, said implant comprising a body having a substantially frusto-conical configuration along a sufficient portion of said body that is adapted to contact the adjacent vertebral bodies when implanted in the spine so as to maintain an angulation of the adjacent vertebral bodies relative to one another, said body having an insertion end, a trailing end, and an outer surface including bone engaging means for engaging said implant to the adjacent vertebral bodies, the locus of said bone engaging means forming a substantially cylindrical configuration, said implant being made of a material appropriate for human implantation.

27. The spinal fusion implant of claim 26 in which said trailing end is larger than said insertion end.

28. The spinal fusion implant of claim 26 in which said implant comprises a bone ingrowth material.

29. The spinal fusion implant of claim 26 in which said implant comprises a fusion promoting material.

30. The spinal fusion implant of claim 26 in which said implant is at least in part bioabsorbable.

31. The spinal fusion implant of claim 26 in which said body has a plurality of openings for retaining fusion promoting material.

32. The spinal fusion implant of claim 26 in which said bone engaging means includes said outer surface being porous at least in part.

33. The spinal fusion implant of claim 26 in which said bone engaging means comprises a plurality of posts spaced apart along at least a portion of the outer surface of said body.

34. The spinal fusion implant of claim 33 in which said plurality of posts have a head portion and a stem portion, said head portion having a wider diameter than said stem portion.

35. The spinal fusion implant of claim 26 in which said bone engaging means comprises a mesh-like material having a plurality of interstices for receiving fusion promoting material.

36. The spinal fusion implant of claim 26 in which said bone engaging means includes 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 outer surface of said implant.

37. The spinal fusion implant of claim 26 in which said surface roughenings include a plurality of ratchetings.

38. The spinal fusion implant of claim 36 in which said surface roughenings include knurling.

39. The spinal fusion implant of claim 26 in which said body has an internal chamber and means for accessing said internal chamber.

40. The spinal fusion implant of claim 39 in which said internal chamber is capable of containing fusion promoting material.

41. The spinal fusion implant of claim 39 in which said body includes a wall surrounding said internal chamber.

42. The spinal fusion implant of claim 39 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

43. The spinal fusion implant of claim 39 in which said body has a cap for closing said accessing means.

44. The spinal fusion implant of claim 26 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

45. The spinal fusion implant of claim 26 in which at least a portion of said outer surface comprises wells having at least partial walls.

46. The spinal fusion implant of claim 26 in which said implant is configured to be placed in close proximity in a side by side alignment to a second spinal fusion implant, said first and second implants when placed together having a combined overall width that is less than the sum of the individual maximum diameters of each of said first and second implants.

47. The spinal fusion implant of claim 26 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

48. The spinal fusion implant of claim 26, in combination with a fusion promoting material.

49. The spinal fusion implant of claim 48, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

50. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between the adjacent vertebral bodies, the implant comprising a body having a substantially frusto-conical configuration along a sufficient portion of said body that is adapted to contact the adjacent vertebral bodies when implanted in the spine so as to maintain an angulation of the adjacent vertebral bodies relative to one another, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said body having an insertion end, a trailing end being larger than said insertion end, and an outer surface including bone engaging projections for engaging said implant to the adjacent vertebral bodies, the outer locus of said bone engaging projections forming a substantially frusto-conical configuration, at least one of said bone engaging projections having a forward portion oriented toward said insertion end and being ramped to facilitate linear insertion of said implant into the disc space and having a rearward portion oriented toward said trailing end adapted to resist expulsion of said implant in a direction opposite to the direction of insertion, said implant being made of a material appropriate for human implantation.

51. The spinal fusion implant of claim 50 in which said implant comprises a bone ingrowth material.

52. The spinal fusion implant of claim 50 in which said implant comprises a fusion promoting material.

53. The spinal fusion implant of claim 50 in which said implant is at least in part bioabsorbable.

54. The spinal fusion implant of claim 50 in which said body includes a plurality of openings adapted to retain fusion promoting material.

55. The spinal fusion implant of claim 50 in which said bone engaging projections include said outer surface being at least in part porous.

56. The spinal fusion implant of claim 50 in which said bone engaging projections comprise a mesh-like material having a plurality of interstices adapted to receive fusion promoting material.

57. The spinal fusion implant of claim 50 in which said bone engaging projections include 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 outer surface of said implant.

58. The spinal fusion implant of claim 57 in which said surface roughenings include a plurality of ratchetings.

59. The spinal fusion implant of claim 50 in which said implant has an internal chamber and means for accessing said internal chamber.

60. The spinal fusion implant of claim 59 in which said internal chamber is configured to contain fusion promoting material.

61. The spinal fusion implant of claim 59 in which said body includes a wall surrounding said internal chamber.

62. The spinal fusion implant of claim 61 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

63. The spinal fusion implant of claim 59 in which said body has a cap for closing said accessing means.

64. The spinal fusion implant of claim 50 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

65. The spinal fusion implant of claim 50 in which at least a portion of said outer surface comprises wells having at least partial walls.

66. The spinal fusion implant of claim 50 in which said implant is configured to be placed in close proximity in a side by side alignment to a second spinal fusion implant, said first and second implants when placed together having a combined overall width that is less than the sum of the individual maximum diameters of each of said first and second implants.

67. The spinal fusion implant of claim 50 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

68. The spinal fusion implant of claim 50, in combination with a fusion promoting material.

69. The spinal fusion implant of claim 68, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

70. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between adjacent vertebral bodies of a human spine, the implant comprising a body having an insertion end, a trailing end, and an outer surface including a plurality of posts having a head and a stem, said head being wider than said stem, said stem having a first portion proximate said head and a second portion proximate said body, a maximum dimension transverse to the length of said stem at said second portion being smaller than a maximum dimension transverse to the length of said stem at said first portion, said posts being spaced apart along at least a portion of said outer surface of said body for engaging said implant to adjacent vertebral bodies of the spine, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said implant being made of a material appropriate for human implantation.

71. The spinal fusion implant of claim 70 in which said implant comprises a bone ingrowth material.

72. The spinal fusion implant of claim 70 in which said implant comprises a fusion promoting material.

73. The spinal fusion implant of claim 70 in which said implant is at least in part bioabsorbable.

74. The spinal fusion implant of claim 70 in which said body includes a plurality of openings adapted to retain fusion promoting material.

75. The spinal fusion implant of claim 70 in which said outer surface is at least in part porous.

76. The spinal fusion implant of claim 70 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 outer surface of said body.

77. The spinal fusion implant of claim 70 in which said implant has an internal chamber and means for accessing said internal chamber.

78. The spinal fusion implant of claim 77 in which said internal chamber is adapted to contain fusion promoting material.

79. The spinal fusion implant of claim 77 in which said body includes a wall surrounding said internal chamber.

80. The spinal fusion implant of claim 79 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

81. The spinal fusion implant of claim 77 in which said body has a cap for closing said accessing means.

82. The spinal fusion implant of claim 70 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

83. The spinal fusion implant of claim 70 in which at least a portion of said outer surface comprises wells having at least partial walls.

84. The spinal fusion implant of claim 70 in which said implant is configured to be placed in close proximity in a side by side alignment to a second spinal fusion implant, said first and second implants when placed together having a combined overall width that is less than the sum of the individual maximum diameters of each of said first and second implants.

85. The spinal fusion implant of claim 70, wherein said implant is made of a material that is stronger than bone.

86. The spinal fusion implant of claim 70, in combination with a fusion promoting material.

87. The spinal fusion implant of claim 70, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

88. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between two adjacent vertebral bodies of a human spine, the implant comprising a body having a substantially frusto-conical configuration along a sufficient portion of said body that is adapted to contact the adjacent vertebral bodies when implanted in the spine so as to maintain an angulation of the adjacent vertebral bodies relative to one another, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said body having an insertion end, a trailing end being larger than said insertion end, and an outer surface including bone engaging projections for engaging said implant to the adjacent vertebral bodies, said bone engaging projections having a forward portion oriented toward said insertion end and being ramped to facilitate linear insertion of said implant into the disc space and having a rearward portion oriented toward said trailing end adapted to resist expulsion of said implant in a direction opposite to the direction of insertion, said implant being made of a material appropriate for human implantation.

89. The spinal fusion implant of claim 88 in which said insertion end is tapered.

90. The spinal fusion implant of claim 88 in which said implant comprises a bone ingrowth material.

91. The spinal fusion implant of claim 88 in which said implant comprises a fusion promoting material.

92. The spinal fusion implant of claim 88 in which said implant is at least in part bioabsorbable.

93. The spinal fusion implant of claim 88 in which said body includes a plurality of openings adapted to retain fusion promoting material.

94. The spinal fusion implant of claim 88 in which said bone engaging projections include said outer surface being at least in part porous.

95. The spinal fusion implant of claim 88 in which said bone engaging projections comprise a mesh-like material having a plurality of interstices adapted to receive fusion promoting material.

96. The spinal fusion implant of claim 88 in which said bone engaging projections include 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 outer surface of said implant.

97. The spinal fusion implant of claim 96 in which said surface roughenings include a plurality of ratchetings.

98. The spinal fusion implant of claim 88 in which said implant has an internal chamber and means for accessing said internal chamber.

99. The spinal fusion implant of claim 98 in which said internal chamber is configured to contain fusion promoting material.

100. The spinal fusion implant of claim 98 in which said body includes a wall surrounding said internal chamber.

101. The spinal fusion implant of claim 100 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

102. The spinal fusion implant of claim 98 in which said body has a cap for closing said accessing means.

103. The spinal fusion implant of claim 88 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

104. The spinal fusion implant of claim 88 in which at least a portion of said outer surface comprises wells having at least partial walls.

105. The spinal fusion implant of claim 88 in which said implant is configured to be placed in close proximity in a side by side alignment to a second spinal fusion implant, said first and second implants when placed together having a combined overall width that is less than the sum of the individual maximum diameters of each of said first and second implants.

106. The spinal fusion implant of claim 88 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

107. The spinal fusion implant of claim 88, wherein said implant is made of a material that is stronger than bone.

108. The spinal fusion implant of claim 88, in combination with a fusion promoting material.

109. The spinal fusion implant of claim 108, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

110. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between adjacent vertebral bodies of a human spine, the implant comprising a body having an insertion end, a trailing end being larger than said insertion end, a length between said ends, and an outer surface including bone engaging projections for engaging said implant to adjacent vertebral bodies of the spine, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, the outer locus of said bone engaging projections forming a substantially frusto-conical configuration along at least a portion of said bone engaging projections that is adapted to contact the adjacent vertebral bodies when implanted in the spine, said substantially frusto-conical configuration being along at least a portion of the length of said implant nearer said trailing end than said insertion end, said bone engaging projections having a forward portion oriented toward said insertion end and being ramped to facilitate linear insertion of said implant in the disc space, said implant being made of a material appropriate for human implantation.

111. The spinal fusion implant of claim 110 in which said body has a substantially frusto-conical configuration along a portion of said outer surface oriented toward said adjacent vertebral bodies.

112. The spinal fusion implant of claim 110 in which said body has a substantially cylindrical configuration along a portion of said outer surface oriented toward said adjacent vertebral bodies.

113. The spinal fusion implant of claim 110 in which said bone engaging projections comprise a mesh-like material having a plurality of interstices adapted to receive fusion promoting material.

114. The spinal fusion implant of claim 110 in which said bone engaging projections include 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 outer surface of said implant.

115. The spinal fusion implant of claim 110 in which said body includes a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

116. The spinal fusion implant of claim 110, wherein said implant is made of a material that is stronger than bone.

117. The spinal fusion implant of claim 110, in combination with a fusion promoting material.

118. The spinal fusion implant of claim 110, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

119. A spinal fusion implant for insertion across the surgically corrected height of a disc space between adjacent vertebral bodies of a human spine, said implant comprising a mid-longitudinal axis and a body having a distal end adapted for insertion first into the disc space, a proximal end opposite thereto, upper and lower surfaces adapted to contact the adjacent vertebral bodies adjacent that disc space, and an outer locus larger than the space between two adjacent vertebral bodies to be fused, said body being formed of a mesh-like material other than bone capable of supporting two adjacent vertebral bodies in a spaced apart relationship to each other, said mesh-like material having a plurality of interstices adapted to receive fusion promoting material and for engaging said implant to said adjacent vertebral bodies of the spine, said interstices being along at least a portion of said outer locus of said body, within at least a portion of an interior of said body, and along at least a portion of a proximal-most portion of said proximal end, said body being adapted to permit the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said implant being made of a material appropriate for human implantation.

120. The spinal fusion implant of claim 119 including a plurality of openings in the outer locus of said implant.

121. The spinal fusion implant of claim 119 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 outer surface of said implant.

122. The spinal fusion implant of claim 119 in which said body includes a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

123. The spinal fusion implant of claim 119 in which said mesh-like material comprises a metal.

124. The spinal fusion implant of claim 119, wherein said body has a hollow interior in communication with at least a portion of said interstices.

125. The spinal fusion implant of claim 119, in combination with a fusion promoting material.

126. The spinal fusion implant of claim 125, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

127. The spinal fusion implant of claim 119, wherein said body is adapted to permit the growth of bone along at least a portion of the length of the mid-longitudinal axis of said implant.

128. The spinal fusion implant of claim 119, wherein said upper and lower surfaces are at least in part arcuate in a direction transverse to the mid-longitudinal axis of said implant.

129. The spinal fusion implant of claim 119, wherein said upper and lower surfaces are in angular relationship to one another.

130. The spinal fusion implant of claim 119, wherein said outer locus of said body has a substantially frusto-conical configuration along a sufficient portion of said body that is adapted to contact the adjacent vertebral bodies when implanted in the spine so as to maintain an angulation of the adjacent vertebral bodies relative to one another.

131. The spinal fusion implant of claim 119, wherein said implant has a maximum width that is less than one-half the width of the disc space into which said implant is adapted to be inserted.

132. The spinal fusion implant of claim 119, wherein said mesh-like material comprises strands.

133. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between two adjacent vertebral bodies of a human spine, the implant comprising a body having an insertion end, a trailing end, a length between said ends, and upper and lower arcuate portions adapted to contact the adjacent vertebral bodies when implanted in the spine, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant;

and

bone engaging projections for engaging said implant to the adjacent vertebral bodies, said bone engaging projections extending from at least a portion of said upper and lower arcuate portions, said bone engaging projections having a maximum height as measured from each of said arcuate portions that increases from one of said ends to the other of said ends along at least a portion of the length of said body.

134. The spinal fusion implant of claim 133 in which said bone engaging projections include second arcuate portions oriented toward the adjacent vertebral bodies.

135. The spinal fusion implant of claim 133, wherein said bone engaging projections comprise a mesh-like material having a plurality of interstices adapted to receive fusion promoting material.

136. The spinal fusion implant of claim 133, wherein said bone engaging projections include 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 outer surface of said implant.

137. The spinal fusion implant of claim 136 in which said surface roughenings include a plurality of ratchetings.

138. The spinal fusion implant of claim 137, wherein said ratchets are configured to facilitate insertion of said implant between the adjacent vertebral bodies while resisting movement of said implant in a direction opposite to the direction of insertion.

139. The spinal fusion implant of claim 137, wherein at least one of said ratchets includes an opening configured to permit bone growth therethrough.

140. The spinal fusion implant of claim 133, wherein said implant is made of a material that is stronger than bone.

141. The spinal fusion implant of claim 133, in combination with a fusion promoting material.

142. The spinal fusion implant of claim 141, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

143. The spinal fusion implant of claim 133, wherein said body includes two opposed sides between said upper and lower arcuate portions, said sides being planar along at least a portion of the length.

144. The spinal fusion implant of claim 143, wherein said sides include at least one opening.

145. The spinal fusion implant of claim 143, wherein said sides are parallel to the central longitudinal axis of said body.

146. The spinal fusion implant of claim 143, wherein said sides have a width therebetween that is less than the height between said upper and lower arcuate portions of said body.

147. The spinal fusion implant of claim 133, wherein the height between said upper and lower arcuate portions is constant along at least a portion of the length of said body.

148. The spinal fusion implant of claim 133, wherein said upper and lower arcuate portions form at least a portion of a cylinder.

149. The spinal fusion implant of claim 133, wherein the height between said upper and lower arcuate portions increases from one of said ends to the other of said ends along at least a portion of the length of said body.

150. The spinal fusion implant of claim 133, wherein said upper and lower arcuate portions are angled relative to one another.

151. The spinal fusion implant of claim 133, wherein said body has a width that is less than the height between said upper and lower arcuate portions.

152. The spinal fusion implant of claim 133, wherein said body includes at least one truncated side between said upper and lower arcuate portions.

153. The spinal fusion implant of claim 133, wherein said body includes at least one side between said upper and lower arcuate portions that is adapted for side-by-side placement with a second implant within at least a portion of the same disc space.

154. The spinal fusion implant of claim 133, wherein said bone engaging projections have a radius as measured from the central longitudinal axis of said body, the radius of said bone engaging projections increasing from one of said ends to the other of said ends along at least a portion of the length of said body.

155. The spinal fusion implant of claim 133, wherein said bone engaging projections have as an outer locus forming a generally frustoconical configuration along at least a portion of the length of said body.

156. The spinal fusion implant of claim 133, wherein said bone engaging projections have a radius as measured from the central longitudinal axis of said body, the radius of said bone engaging projections being substantially constant from one of said ends to the other of said ends along at least a portion of the length of said body.

157. The spinal fusion implant of claim 133, wherein said bone engaging projections have an outer locus forming a generally cylindrical configuration along at least a portion of the length of said body.

158. The spinal fusion implant of claim 133, wherein the maximum height of said bone engaging projections is between 0.25 to 2.0 mm.

159. The spinal fusion implant of claim 133, further comprising a hollow.

160. The spinal fusion implant of claim 159, wherein said hollow forms a chamber in communication with said openings, said chamber having an access opening for loading said chamber with fusion promoting substances.

161. The spinal fusion implant of claim 133, wherein said implant is at least in part bioabsorbable.

162. A non-threaded interbody spinal fusion implant for insertion across the surgically corrected height of a disc space between two adjacent vertebral bodies of a human spine, the implant comprising:

a body having a insertion end, a trailing end, a length between said ends, an outer surface, and bone engaging projections extending from said outer surface for engaging said implant to the adjacent vertebral bodies, said bone engaging projections having arcuate portions adapted to contact the adjacent vertebral bodies when implanted in the spine, said bone engaging projections having a distance between said arcuate portions and said outer surface of said body that increases from one of said ends to the other of said ends along at least a portion of the length of said body so as to maintain an angulation of the adjacent vertebral bodies relative to one another, said body having at least two openings in communication with one another for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.

163. The spinal fusion implant of claim 162 in which said bone engaging projections comprise a mesh-like material having a plurality of interstices adapted to receive fusion promoting material.

164. The spinal fusion implant of claim 162 in which said bone engaging projections include 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 outer surface of said implant.

165. The spinal fusion implant of claim 164 in which said surface roughenings include a plurality of ratchetings.

166. The spinal fusion implant of claim 164 in which said surface roughenings include knurling.

167. The spinal fusion implant of claim 162, wherein said implant is made of a material that is stronger than bone.

168. The spinal fusion implant of claim 162, in combination with a fusion promoting material.

169. The spinal fusion implant of claim 168, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

170. The spinal fusion implant of claim 162, wherein said body includes two opposed sides between said upper and lower arcuate portions, said sides being planar along at least a portion of the length.

171. The spinal fusion implant of claim 170, wherein said sides include at least one opening.

172. The spinal fusion implant of claim 170, wherein said sides are parallel to the central longitudinal axis of said body.

173. The spinal fusion implant of claim 170, wherein said sides have a width therebetween that is less than the height between said upper and lower arcuate portions of said body.

174. The spinal fusion implant of claim 162, wherein said bone engaging projections have a radius as measured from the central longitudinal axis of said body, the radius of said bone engaging projections increasing from one of said ends to the other of said ends along at least a portion of the length of said body.

175. The spinal fusion implant of claim 162, wherein said bone engaging projections have as an outer locus forming a generally frustoconical configuration along at least a portion of the length of said body.

176. The spinal fusion implant of claim 162, wherein said bone engaging projections have a radius as measured from the central longitudinal axis of said body, the radius of said bone engaging projections being substantially constant from one of said ends to the other of said ends along at least a portion of the length of said body.

177. The spinal fusion implant of claim 162, wherein said bone engaging projections have an outer locus forming a generally cylindrical configuration along at least a portion of the length of said body.

178. The spinal fusion implant of claim 162, wherein the maximum height of said bone engaging projections is between 0.25 to 2.0 mm.

179. The spinal fusion implant of claim 162, further comprising a hollow.

180. The spinal fusion implant of claim 179, wherein said hollow forms a chamber in communication with said openings, said chamber having an access opening for loading said chamber with fusion promoting substances.

181. The spinal fusion implant of claim 162, wherein said implant is at least in part bioabsorbable.

182. A spinal fusion implant for insertion across the surgically corrected height of a disc space between adjacent vertebral bodies of a human spine, said implant comprising a body having a distal end adapted for insertion first into the disc space, a proximal end opposite thereto, upper and lower surfaces adapted to contact the adjacent vertebral bodies adjacent that disc space, and an outer locus larger than the space between two adjacent vertebral bodies to be fused, said body being formed of a cancellous material other than bone capable of supporting two adjacent vertebral bodies in a spaced apart relationship to each other, said cancellous material having a plurality of interstices for holding fusion promoting material and for permitting the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant, said proximal end having a proximal-most portion formed of said cancellous material, said implant being made of a material appropriate for human implantation.

183. The spinal fusion implant of claim 182 including a plurality of openings in the exterior surface of said implant.

184. The spinal fusion implant of claim 182 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 outer surface of said implant.

185. The spinal fusion implant of claim 182 in which said body includes a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

186. The spinal fusion implant of claim 182, in combination with a fusion promoting material.

187. The spinal fusion implant of claim 186, wherein said fusion promoting material includes at least one of bone, bone morphogenetic protein, hydroxyapatite, hydroxyapatite compounds, and osteogenic proteins.

188. The spinal fusion implant of claim 182, wherein said upper and lower surfaces are at least in part arcuate in a direction transverse to the mid-longitudinal axis of said implant.

189. The spinal fusion implant of claim 182, wherein said upper and lower surfaces are in angular relationship to one another.

190. The spinal fusion implant of claim 182, wherein said outer locus of said body has a substantially frusto-conical configuration along a sufficient portion of said body that is adapted to contact the adjacent vertebral bodies when implanted in the spine so as to maintain an angulation of the adjacent vertebral bodies relative to one another.

191. The spinal fusion implant of claim 182, wherein said implant has a maximum width that is less than one-half the width of the disc space into which said implant is adapted to be inserted.