Threaded frusto-conical interbody spinal fusion implants

• US 7,534,254 B1
• Filed: 06/07/1995
• Issued: 05/19/2009
• Est. Priority Date: 06/13/1988
• Status: Expired due to Fees

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Inventors: Michelson, Gary Karlin
• Primary Examiner(s): Brown; Michael A.
• Application Number:
  US08/480,908
• Time in Patent Office: 5,095 Days
• Field of Search: 606 60- 61, 606 72- 79, 606/246, 623/16, 623/17, 623/16.11, 623/17.11
• US Class Current: 606/246
• 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 17/3468 for implanting or removing devices, e.g. prostheses, implants, seeds, wires devices for implanting seeds A61M37/0069
• CPC Class Codes: A61B 17/8875 Screwdrivers, spanners or wrenches
• 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 2/4637 for connecting or disconnecting two parts of a prosthesis
• 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 2002/30861 : having threads of increasing or decreasing height
• 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 2002/4627 : 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 2002/4649 : 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 2310/00293 : 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
• 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

Abstract

The present invention is directed to a variety of interbody spinal fusion implants having at least a partially frusto-conical configuration. An external thread is employed to increase implant stability and implant surface area, and for the purpose of advancing the spinal fusion implant into the fusion site. 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.

Claims

1. An interbody spinal fusion implant for insertion across a disc space between adjacent vertebral bodies of a human spine, said implant comprising a body having an insertion end, a trailing end, a length between said ends, and an outer surface including a thread for engaging said implant to the adjacent vertebral bodies, the outer locus of said thread forming a substantially frusto-conical configuration along at least a portion of the length of said implant nearer said trailing end than said insertion end.

2. The implant of claim 1 in which said body has a substantially frusto-conical configuration along a sufficient portion of said implant 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.

3. The implant of claim 1 in which said body has a substantially cylindrical configuration.

4. The spinal fusion implant of claim 1 in which said trailing end is larger than said insertion end.

5. The spinal fusion implant of claim 1 in which said insertion end is larger than said trailing end.

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

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

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

9. The spinal fusion implant of claim 1 in which said body has a plurality of openings for retaining fusion promoting material.

10. The spinal fusion implant of claim 1 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being variable along the length of said implant.

11. The spinal fusion implant of claim 1 in which said thread has a thread height measured from said body which is variable along the length of said implant.

12. The spinal fusion implant of claim 1 in which said thread beyond said insertion end has a thread height measured from said body which is substantially constant along the length of said implant.

13. The spinal fusion implant of claim 1 in which said body comprises a porous material.

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

15. The spinal fusion implant of claim 14 in which said internal chamber is capable of containing fusion promoting material.

16. The spinal fusion implant of claim 14 in which said body includes a wall surrounding said internal chamber.

17. The spinal fusion implant of claim 16 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

18. The spinal fusion implant of claim 14 in which said body has means for closing said accessing means.

19. The spinal fusion implant of claim 15 in which said body has means 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 body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

23. The spinal fusion implant of claim 22 in which said thread has a thread height measured from said body which is greatest at said truncated side.

94. The spinal fusion implant of claim 22 in which said thread is continuous over at least a portion of said truncated side.

95. The spinal fusion implant of claim 1 in which said thread has a height measured from said body that is larger at said trailing end than at said insertion end.

96. The spinal fusion implant of claim 1 in which said body has a plurality of openings passing therethrough so as to allow bone to grow from adjacent vertebral body to adjacent vertebral body and through said implant.

97. The spinal fusion implant of claim 22 in which said body has a second truncated side forming a planar surface parallel to said central axis and opposite to said one truncated side.

121. The spinal fusion implant of claim 1 in which said implant is made of a material that is stronger than bone.

125. The spinal fusion implant of claim 1 in which said body has a length in the range of 10-32 mm.

130. The spinal fusion implant of claim 1 having a diameter at said insertion end in the range of 8-22 mm.

135. The spinal fusion implant of claim 1 having a diameter at said trailing end in the range of 10-24 mm.

144. The spinal fusion implant of claim 1 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being substantially uniform throughout at least a portion of said implant.

147. The spinal fusion implant of claim 1, further in combination with a fusion promoting substance.

148. The spinal fusion implant of claim 147, wherein said fusion promoting substance is bone morphogenetic protein.

149. The spinal fusion implant of claim 147, wherein said fusion promoting substance includes hydroxyapatite.

150. The spinal fusion implant of claim 147, wherein said fusion promoting substance includes hydroxyapatite tricalcium phosphate.

151. The spinal fusion implant of claim 147, wherein said fusion promoting substance is bone.

24. An interbody spinal fusion implant for insertion across 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 a thread for engaging said implant to the adjacent vertebral bodies of the spine, the locus of said thread forming a substantially cylindrical configuration.

25. The spinal fusion implant of claim 24 in which said trailing end is larger than said insertion end.

26. The spinal fusion implant of claim 24 in which said insertion end is larger than said trailing end.

27. The spinal fusion implant of claim 24 in which said implant comprises a bone ingrowth material.

28. The spinal fusion implant of claim 24 in which said implant comprises a fusion promoting material.

29. The spinal fusion implant of claim 24 in which said implant is at least in part bioabsorbable.

30. The spinal fusion implant of claim 24 in which said body has a plurality of openings for retaining fusion promoting material.

31. The spinal fusion implant of claim 24 in which said thread beyond said insertion end has a thread radius measured from the longitudinal central axis of said implant, said thread radius being substantially uniform throughout the length of said implant.

32. The spinal fusion implant of claim 24 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being variable along at least a portion of said implant.

33. The spinal fusion implant of claim 24 in which said thread has a thread height measured from said body which is variable along the length of said implant.

34. The spinal fusion implant of claim 24 in which said thread has a thread height measured from said body which is substantially constant along at least a portion of said implant.

35. The spinal fusion implant of claim 24 in which said body comprises a porous material.

36. The spinal fusion implant of claim 24 in which said body has an internal chamber and means for accessing said internal chamber.

37. The spinal fusion implant of claim 36 in which said internal chamber is capable of containing fusion promoting material.

38. The spinal fusion implant of claim 36 in which said body includes a wall surrounding said internal chamber.

39. The spinal fusion implant of claim 38 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

40. The spinal fusion implant of claim 36 in which said body has means for closing said accessing means.

41. The spinal fusion implant of claim 24 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

42. The spinal fusion implant of claim 24 in which at least a portion of said outer surface comprises wells having at least partial walls.

43. The spinal fusion implant of claim 24 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.

44. The spinal fusion implant of claim 24 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

45. The spinal fusion implant of claim 44 in which said thread has a thread height measured from said body which is greatest at said truncated side.

91. The spinal fusion implant of claim 24 in which said implant has an upper and lower portion for engaging the bone of the adjacent vertebral bodies, said upper and lower portions comprising a plurality of macroscopic openings.

98. The spinal fusion implant of claim 24 in which said thread has a height measured from said body that is larger at said trailing end than at said insertion end.

99. The spinal fusion implant of claim 24 in which said body has a plurality of openings passing therethrough so as to allow bone to grow from adjacent vertebral body to adjacent vertebral body and through said implant.

100. The spinal fusion implant of claim 44 in which said body has a second truncated side forming a planar surface parallel to said central axis and opposite to said one truncated side.

122. The spinal fusion implant of claim 24 in which said implant is made of a material that is stronger than bone.

126. The spinal fusion implant of claim 24 in which said body has a length in the range of 10-32 mm.

131. The spinal fusion implant of claim 24 having a diameter at said insertion end in the range of 8-22 mm.

136. The spinal fusion implant of claim 24 having a diameter at said trailing end in the range of 10-24 mm.

145. The spinal fusion implant of claim 24 in which said body has a substantially frusto-conical configuration.

146. The spinal fusion implant of claim 24 in which said body has at least in part a cylindrical configuration.

152. The spinal fusion implant of claim 24, further in combination with a fusion promoting substance.

153. The spinal fusion implant of claim 152, wherein said fusion promoting substance is bone morphogenetic protein.

154. The spinal fusion implant of claim 152, wherein said fusion promoting substance includes hydroxyapatite.

155. The spinal fusion implant of claim 152, wherein said fusion promoting substance includes hydroxyapatite tricalcium phosphate.

156. The spinal fusion implant of claim 152, wherein said fusion promoting substance is bone.

46. An interbody spinal fusion implant for insertion across a disc space between adjacent vertebral bodies of a human spine, said implant comprising a body having a substantially cylindrical configuration, a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis, said body having an insertion end, a trailing end, and an outer surface including a thread for engaging said implant to the adjacent vertebral bodies of the spine, the locus of said thread forming a substantially cylindrical configuration.

47. The spinal fusion implant of claim 46 in which said implant comprises a bone ingrowth material.

48. The spinal fusion implant of claim 46 in which said implant comprises a fusion promoting material.

49. The spinal fusion implant of claim 46 in which said implant is at least in part bioabsorbable.

50. The spinal fusion implant of claim 46 having a plurality of openings capable retaining fusion promoting material.

51. The spinal fusion implant of claim 46 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being substantially uniform for at least a portion of said implant.

52. The spinal fusion implant of claim 46 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being variable along at least a portion of said implant.

53. The spinal fusion implant of claim 46 in which said thread has a thread height measured from said body which is variable along at least a portion of said implant.

54. The spinal fusion implant of claim 46 in which said thread has a thread height measured from said body which is substantially constant along the length of said implant.

55. The spinal fusion implant of claim 46 body comprises a porous material.

56. The spinal fusion implant of claim 46 in which said body has an internal chamber and means for accessing said internal chamber.

57. The spinal fusion implant of claim 56 in which said internal chamber is capable of containing fusion promoting material.

58. The spinal fusion implant of claim 56 in which said includes a wall surrounding said internal chamber.

59. The spinal fusion implant of claim 56 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

60. The spinal fusion implant of claim 56 in which said implant has means for closing said accessing means.

61. The spinal fusion implant of claim 46 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

62. The spinal fusion implant of claim 46 in which at least a portion of said outer surface comprises wells having at least partial walls.

63. The spinal fusion implant of claim 46 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.

64. The spinal fusion implant of claim 46 in which said body has a second truncated side forming a planar surface parallel to said central axis and opposite to said one truncated side.

65. The spinal fusion implant of claim 64 in which said thread has a thread height measured from said body which is greatest at at least one of said truncated sides.

90. The spinal fusion implant of claim 46 in which said thread has a thread height measured from said body which is greatest at said truncated side.

92. The spinal fusion implant of claim 46 in which said implant has an upper and lower portion for engaging the bone of the adjacent vertebral bodies, said upper and lower portions comprising a plurality of macroscopic openings.

101. The spinal fusion implant of claim 46 in which said body has a plurality of openings passing therethrough so as to allow bone to grow from adjacent vertebral body to adjacent vertebral body and through said implant.

123. The spinal fusion implant of claim 46 in which said implant is made of a material that is stronger than bone.

127. The spinal fusion implant of claim 46 in which said body has a length in the range of 10-32 mm.

132. The spinal fusion implant of claim 46 having a diameter at said insertion end in the range of 8-22 mm.

137. The spinal fusion implant of claim 46 having a diameter at said trailing end in the range of 10-24 mm.

157. The spinal fusion implant of claim 46, further in combination with a fusion promoting substance.

158. The spinal fusion implant of claim 157, wherein said fusion promoting substance is bone morphogenetic protein.

159. The spinal fusion implant of claim 157, wherein said fusion promoting substance includes hydroxyapatite.

160. The spinal fusion implant of claim 157, wherein said fusion promoting substance includes hydroxyapatite tricalcium phosphate.

161. The spinal fusion implant of claim 157, wherein said fusion promoting substance is bone.

66. An interbody spinal fusion implant for insertion across a disc space between two adjacent vertebral bodies, 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 a thread for engaging said implant to the adjacent vertebral bodies of the spine, said implant being made of a material appropriate for human implantation.

67. The implant of claim 66 in which the outer locus of said thread forms a substantially cylindrical configuration.

68. The spinal fusion implant of claim 66 in which said insertion end is larger than said trailing end.

69. The spinal fusion implant of claim 68 in which said insertion end comprises a tapered leading portion.

70. The spinal fusion implant of claim 66 in which said trailing end is larger than said insertion end.

71. The spinal fusion implant of claim 66 in which said implant comprises a bone ingrowth material.

72. The spinal fusion implant of claim 66 in which said implant comprises a fusion promoting material.

73. The spinal fusion implant of claim 66 in which said implant is at least in part bioabsorbable.

74. The spinal fusion implant of claim 66 in which said body has a plurality of openings for retaining fusion promoting material.

75. The spinal fusion implant of claim 66 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being substantially uniform throughout the length of said implant.

76. The spinal fusion implant of claim 66 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being variable along the length of said implant.

77. The spinal fusion implant of claim 66 in which said thread has a thread height measured from said body which is variable along the length of said implant.

78. The spinal fusion implant of claim 66 in which said thread has a thread height measured from said body which is substantially constant along the length of said implant.

79. The spinal fusion implant of claim 66 in which said body comprises a porous material.

80. The spinal fusion implant of claim 66 in which said body has an internal chamber and an access opening for accessing said internal chamber.

81. The spinal fusion implant of claim 80 in which said internal chamber is capable of retaining fusion promoting material.

82. The spinal fusion implant of claim 80 in which said body includes a wall surrounding said internal chamber.

83. The spinal fusion implant of claim 82 in which said wall has a plurality of openings passing therethrough in communication with said internal chamber.

84. The spinal fusion implant of claim 80 in which said body has means for closing said accessing means.

85. The spinal fusion implant of claim 66 in which one of said ends includes an engagement means for engaging instrumentation for the insertion of said implant.

86. The spinal fusion implant of claim 66 in which at least a portion of said outer surface comprises wells having at least partial walls.

87. The spinal fusion implant of claim 66 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.

88. The spinal fusion implant of claim 66 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

89. The spinal fusion implant of claim 88 in which said thread has a thread height which when measured from said body is at its greatest on said truncated side.

93. The spinal fusion implant of claim 66 in which said implant has an upper and lower portion for engaging the bone of the adjacent vertebral bodies, said upper and lower portions comprising a plurality of macroscopic openings.

102. The spinal fusion implant of claim 66 in which said thread has a height measured from said body that is larger at said trailing end than at said insertion end.

103. The spinal fusion implant of claim 66 in which said body has a plurality of openings passing therethrough so as to allow bone to grow from adjacent vertebral body to adjacent vertebral body and through said implant.

104. The spinal fusion implant of claim 88 in which said body has a second truncated side forming a planar surface parallel to said central axis and opposite to said one truncated side.

124. The spinal fusion implant of claim 66 in which said implant is made of a material that is stronger than bone.

128. The spinal fusion implant of claim 66 in which said body has a length in the range of 10-32 mm.

133. The spinal fusion implant of claim 66 having a diameter at said insertion end in the range of 8-22 mm.

138. The spinal fusion implant of claim 66 having a diameter at said trailing end in the range of 10-24 mm.

162. The spinal fusion implant of claim 66, further in combination with a fusion promoting substance.

163. The spinal fusion implant of claim 162, wherein said fusion promoting substances is bone morphogenetic protein.

164. The spinal fusion implant of claim 162, wherein said fusion promoting substance includes hydroxyapatite.

165. The spinal fusion implant of claim 162, wherein said fusion promoting substance includes hydroxyapatite tricalcium phosphate.

166. The spinal fusion implant of claim 162, wherein said fusion promoting substance is bone.

105. An interbody spinal fusion implant for insertion across a disc space between adjacent vertebral bodies of a human spine, said implant comprising:

a body having an outer surface, an insertion end, a trailing end, and a length between said insertion end and said trailing end, said body having transversely opposed arcuate portions oriented toward the adjacent vertebral bodies, said arcuate portions being in a diverging relationship to one another along a sufficient portion of the length of said body adapted to contact the adjacent vertebral bodies sufficient to maintain angulation of the vertebral bodies relative to one another, said outer surface comprising a thread for engaging said implant to the adjacent vertebral bodies of the spine.

106. The spinal fusion implant of claim 105 in which said trailing end is larger than said insertion end.

107. The spinal fusion implant of claim 105 in which said insertion end is larger than said trailing end.

108. The spinal fusion implant of claim 105 in which said body has a plurality of openings for retaining fusion promoting material.

109. The spinal fusion implant of claim 105 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being substantially uniform throughout at least a portion of said implant.

110. The spinal fusion implant of claim 105 in which said thread has a thread radius measured from the longitudinal central axis of said implant, said thread radius being variable along the length of said implant.

111. The spinal fusion implant of claim 105 in which said thread has a thread height measured from said body which is variable along the length of said implant.

112. The spinal fusion implant of claim 105 in which said body has an internal chamber and means for accessing said internal chamber.

113. The spinal fusion implant of claim 112 in which said body has means for closing said accessing means.

114. The spinal fusion implant of claim 105 in which at least a portion of said outer surface comprises wells having at least partial walls.

115. The spinal fusion implant of claim 105 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.

116. The spinal fusion implant of claim 105 in which said body has a longitudinal central axis and at least one truncated side forming a planar surface parallel to said central axis.

117. The spinal fusion implant of claim 105 in which said arcuate portions are along the entire length of said body.

118. The spinal fusion implant of claim 105 in which the outer locus of the thread forms a substantially cylindrical configuration.

119. The spinal fusion implant of claim 105 in which the outer locus of the thread forms a substantially frusto-conical configuration.

120. The spinal fusion implant of claim 105 in which said implant is made of a material that is stronger than bone.

129. The spinal fusion implant of claim 105 in which said length is in the range of 10-32 mm.

134. The spinal fusion implant of claim 105 having a diameter at said insertion end in the range of 8-22 mm.

139. The spinal fusion implant of claim 105 having a diameter at said trailing end in the range of 10-24 mm.

142. The spinal fusion implant of claim 116 in which said body has a second truncated side forming a planar surface parallel to said central axis and opposite to said one truncated side.

143. The spinal fusion implant of claim 105 in which said body has a plurality of openings passing therethrough so as to allow bone to grow from adjacent vertebral body to adjacent vertebral body and through said implant.

167. The spinal fusion implant of claim 105, further in combination with a fusion promoting substance.

168. The spinal fusion implant of claim 167, wherein said fusion promoting substance is bone morphogenetic protein.

169. The spinal fusion implant of claim 167, wherein said fusion promoting substance includes hydroxyapatite.

170. The spinal fusion implant of claim 167, wherein said fusion promoting substance includes hydroxyapatite tricalcium phosphate.

171. The spinal fusion implant of claim 167, wherein said fusion promoting substance is bone.

140. A fusion device for facilitating arthrodesis in the disc space between adjacent vertebrae, comprising:

an elongated body having a length, a first diameter at a first end and a larger second diameter at a second end opposite said first end, said first and second diameters sized to be greater than the space between the adjacent vertebrae;

said body having an outer surface that is substantially continuously tapered from said first end to said second end with external threads defined on said outer surface and extending substantially entirely along said length of said body.

141. The fusion device according to claim 140, wherein said body is formed of a porous biocompatible material to permit bone tissue ingrowth into the device.

172. A fusion device for facilitating arthrodesis in the disc space between adjacent vertebrae, comprising:

an elongated body having a length and an outer surface extending along said length, said outer surface including a pair of oppositely disposed arcuate portions and a pair of substantially flat portions extending between said pair of arcuate portions, said pair of arcuate portions defining external threads extending substantially entirely along said length of said body, said pair of substantially flat portions extending along a substantial portion of said length of said body, said pair of substantially flat portions terminating adjacent a first end of said elongated body, said external threads defining at least one circumferentially continuous thread extending along a majority of the length of said elongated body.

173. The fusion device according to claim 172, wherein said pair of opposite arcuate portions defines an outer dimension adjacent a first end of said elongated body, said outer dimension being adapted for engagement within a lesser dimension of the disc space.

174. The fusion device according to claim 172, wherein said elongated body defines a hollow interior.

175. A fusion device for facilitating arthrodesis in the disc space between adjacent vertebrae, comprising:

an elongated body having a length and an outer surface extending along said length, said outer surface including a pair of oppositely disposed arcuate portions and a pair of substantially flat portions extending between said pair of arcuate portions, said pair of arcuate portions defining an external thread extending substantially entirely along said length of said body, said pair of substantially flat portions extending along a substantial portion of said length of said body, said substantially flat portions being interrupted by said thread, said elongated body defining a hollow interior, said pair of arcuate portions each defining at least one opening extending therethrough in communication with said hollow interior.

176. The fusion device according to claim 175, further comprising a bone growth inducing material disposed within said hollow interior.

177. The fusion device according to claim 175, wherein said pair of substantially flat portions are disposed generally opposite one another.

178. The fusion device according to claim 175, wherein said pair of substantially flat portions are substantially parallel to one another.

179. The fusion device according to claim 175, wherein said openings defined by said pair of arcuate portions are disposed generally opposite one another.

180. The fusion device according to claim 175, wherein said pair of arcuate portions are tapered along a substantial portion of said length of said elongated body.

181. The fusion device according to claim 175, further comprising an insertion instrument adapted to implant the fusion device within the disc space between the adjacent vertebrae.

182. An 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, said implant comprising:

a body having a leading end for insertion first into the disc space, a trailing end opposite said leading end, a central longitudinal axis therebetween, and a length along the central longitudinal axis, said body having opposed arcuate portions between said leading and trailing ends adapted to be placed within the implantation space oriented toward the adjacent vertebral bodies, respectively, said opposed arcuate portions 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 body having at least one truncated side along at least a portion of the central longitudinal axis between said opposed arcuate portions and between said leading and trailing ends; and

a thread along at least a portion of the length of said body adapted to engage said implant to the adjacent vertebral bodies, said thread having a thread height measured from said body which is greatest at said at least one truncated side, said at least one truncated side having a truncated portion between said thread and said leading end.

183. An 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, said implant comprising:

a body having a leading end for insertion first into the disc space, a trailing end opposite said leading end, a mid-longitudinal axis through said leading and trailing ends, and opposed arcuate portions between said leading and trailing ends adapted to be placed within the implantation space oriented toward the adjacent vertebral bodies, respectively, said opposed arcuate portions 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; and

a thread adapted to engage said implant to the adjacent vertebral bodies, said thread having a thread height measured from said body, said thread height being variable along more than one turn of said thread about the mid-longitudinal axis of said body.