Intervertebral disc having translation

• US 20040002761A1
• Filed: 06/19/2003
• Published: 01/01/2004
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Depuy Synthes Products Incorporated (Johnson & Johnson)
• Original Assignee: Depuy Acromed Incorporated (Johnson & Johnson)
• Inventors: Rogers, Christopher, Fatyol, Patrick, Lionetto, Mark, Dooris, Andrew, Hawkins, J. Riley, Naughton, Ronald J.
• Granted Patent: US 7,517,363 B2
• Time in Patent Office: Days
• US Class Current: 623/17.13
• CPC Class Codes: A61F 2/08 Muscles; Tendons; Ligaments sutures A61B17/04
• CPC Class Codes: A61F 2/30724 Spacers for centering an implant in a bone cavity, e.g. in a cement-receiving cavity
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/442 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 2/4425 made of articulated components
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/3008 radio-opaque, e.g. radio-opaque markers
• CPC Class Codes: A61F 2002/30092 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30224 cylindrical
• CPC Class Codes: A61F 2002/30232 Half-cylinders
• CPC Class Codes: A61F 2002/30245 Partial spheres
• CPC Class Codes: A61F 2002/30253 ellipsoidal or ovoid
• CPC Class Codes: A61F 2002/30327 differing in diameter
• CPC Class Codes: A61F 2002/30369 Limited lateral translation of the protrusion within a larger recess
• CPC Class Codes: A61F 2002/30383 made by laterally inserting a protrusion, e.g. a rib into a complementarily-shaped groove
• CPC Class Codes: A61F 2002/30387 Dovetail connection
• CPC Class Codes: A61F 2002/304 with additional means for limiting said sliding
• CPC Class Codes: A61F 2002/30433 : using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30462 : retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2002/30481 : using a locking clip
• CPC Class Codes: A61F 2002/30495 : using a locking ring
• CPC Class Codes: A61F 2002/305 : Snap connection
• CPC Class Codes: A61F 2002/30515 : using a locking wedge or block
• CPC Class Codes: A61F 2002/30528 : Means for limiting said movement
• CPC Class Codes: A61F 2002/30563 : having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30565 : having spring elements
• CPC Class Codes: A61F 2002/30566 : Helical springs
• CPC Class Codes: A61F 2002/30578 : having apertures, e.g. for receiving fixation screws
• CPC Class Codes: A61F 2002/30604 : modular
• CPC Class Codes: A61F 2002/30649 : Ball-and-socket joints
• CPC Class Codes: A61F 2002/30662 : with rotation-limiting means
• CPC Class Codes: A61F 2002/30733 : Inserts placed into an endoprosthetic cavity, e.g. for modifying a material property
• CPC Class Codes: A61F 2002/3082 : Grooves
• CPC Class Codes: A61F 2002/30838 : Microstructures
• 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 2002/30878 : with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/30883 : dovetail-shaped
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/30939 : Means for modifying the geometry of articulating surfaces, e.g. for compensating excessive clearance caused by wear
• CPC Class Codes: A61F 2002/443 : having two transversal endplates and at least one intermediate component
• CPC Class Codes: A61F 2210/0004 : bioabsorbable
• CPC Class Codes: A61F 2210/0014 : using shape memory or superelastic materials, e.g. nitinol
• 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 2220/0075 : sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0071 : spherical
• CPC Class Codes: A61F 2230/0076 : ellipsoidal or ovoid
• CPC Class Codes: A61F 2250/0039 : differing in diameter
• CPC Class Codes: A61F 2250/0098 : radio-opaque, e.g. radio-opaque markers
• 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 2310/00203 : containing alumina or aluminium oxide
• CPC Class Codes: A61F 2310/00239 : containing zirconia or zirconium oxide ZrO2
• CPC Class Codes: A61F 2310/0058 : Coating made of diamond or of diamond-like carbon DLC
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

This invention relates to an intervertebral motion disc having two motion surfaces and an open channel.

Claims

1. A prosthetic vertebral endplate comprising:

i) an outer surface adapted to mate with a vertebral body,

ii) an inner surface having a first opening thereon,

iii) a body portion connecting the inner and outer surfaces and defining a sidewall comprising a second opening thereon, and

iv) an articulation surface suitable for supporting articulation motion,

wherein the first and second openings communicate to form a channel having a first open end.

2. The endplate of claim 1 wherein the articulation surface is disposed within the channel.

3. The endplate of claim 1 wherein the sidewall has an anterior portion, and the channel has a bottom surface extending smoothly to the anterior portion of the sidewall.

4. The endplate of claim 1 wherein the channel has a bottom surface having a lip extending therefrom towards the inner surface.

5. The endplate of claim 4 wherein the lip is disposed substantially near the sidewall.

6. The endplate of claim 4 wherein the lip has a height that is no more than 80% of the height of the channel.

7. The endplate of claim 1 wherein the articulation surface is disposed upon the inner surface.

8. The endplate of claim 1 wherein the sidewall further comprises a third opening thereon, wherein the first and third openings communicate to form a second open end in the channel.

9. The endplate of claim 1 wherein the articulation surface is substantially flat.

10. The endplate of claim 1 wherein the articulation surface is slightly hemicylindrical.

11. The endplate of claim 10 wherein the slightly hemicylindrical articulation surface has an anterior-posterior curve.

12. The endplate of claim 10 wherein the slightly hemicylindrical articulation surface has a medial-lateral curve.

13. The endplate of claim 1 wherein the articulation surface is slightly hemispherical.

14. The endplate of claim 1 wherein the articulation surface is slightly curved.

15. The endplate of claim 1 wherein the sidewall has an anterior portion and a posterior portion, and the open end of the channel opens upon the anterior portion of the sidewall.

16. The endplate of claim 1 wherein the articulation surface is slightly concave.

17. The endplate of claim 1 wherein the articulation surface is slightly convex.

18. The endplate of claim 1 wherein the articulation surface has a surface roughness Ra of no more than 10 nm.

19. The endplate of claim 1 wherein the sidewall has an anterior portion and a posterior portion, and the channel runs in a substantially anterior-posterior direction.

20. The endplate of claim 1 wherein channel has an anterior surface and a raised posterior articulation surface.

21. An intervertebral motion disc comprising:

a) a prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a vertebral body,

ii) an inner surface having a first opening thereon,

iii) a body portion connecting the inner and outer surfaces and defining a sidewall comprising a second opening thereon, and

iv) a first articulation surface suitable for supporting articulation motion,

wherein the first and second openings communicate to form a channel having a first open end, and

b) a core member having a first articulation surface suitable for supporting articulation motion,

wherein the core member is disposed within the channel and oriented therein to produce a first articulation interface between the first articulation surface of the first endplate and the first articulation surface of the core member.

22. The disc of claim 21 wherein the articulation interface is a conforming interface.

23. The disc of claim 21 wherein the core member has a lip and the channel has a sidewall having an undercut shaped for receiving the lip.

24. The disc of claim 21 wherein the first articulation surface of the core is disposed within the channel to produce a first articulation interface within the channel.

25. The disc of claim 24 wherein the first articulation surface of the core is disposed only within the channel.

26. The disc of claim 21 wherein the core has a projection shaped to be received in the channel, and the first articulation surface of the core is disposed upon the inner surface.

27. The disc of claim 21 wherein the first articulation surface is disposed upon the inner surface.

28. The disc of claim 21 wherein the sidewall has an anterior and a posterior portion, and wherein the core and the channel are adapted to provide a range of anterior-posterior A-P motion and a range of medial-lateral M-L motion, wherein the range of A-P motion is between 1.5 and 8 times the range of M-L motion.

29. The disc of claim 21 wherein the core and the channel are adapted to provide substantially only A-P motion.

30. The disc of claim 21 wherein the articulation interface forms a hemicylindrical interface.

31. The disc of claim 30 wherein the hemicylindrical interface has a linear dimension and a curved dimension, and the linear dimension is disposed in the A-P direction, and the curved dimension is disposed in the M-L direction.

32. The disc of claim 30 wherein the hemicylindrical interface has a linear dimension and a curved dimension, and the linear dimension is disposed in the M-L direction and the curved dimension is disposed in the A-P direction.

33. The disc of claim 21 wherein the articulation interface has a length and the core member has a diameter, and the length of the articulation interface is between 10% and 50% of the diameter of the core.

34. The disc of claim 21 wherein the channel has a width and the core member has a diameter, and the width of the channel is between 5% and 20% greater than the diameter of the core.

35. The disc of claim 21 further comprising:

c) means for retaining the core member within the channel.

36. The disc of claim 35 wherein the means for retaining the core member comprises a third component.

37. The disc of claim 36 wherein the third component is a tab shaped for insertion into the channel, and wherein the tab is disposed within the channel.

38. The disc of claim 37 wherein the tab comprises a body portion and deformable arms extending from the body portion.

39. The disc of claim 38 wherein each deformable arm comprises a wing extending therefrom.

40. The disc of claim 39 wherein the channel has a sidewall defining a first width and the wings define a wingspan, and wherein the wingspan exceeds the first width of the channel.

41. The disc of claim 40 wherein the sidewall further comprises opposing socket extending therein, and the wings are shaped to be received within the sockets.

42. The disc of claim 37 wherein the core member has an anterior portion having a shape, the tab comprises a posterior portion having a shape, and the shape of the anterior portion of the core member substantially conforms to the shape of the posterior portion of the tab.

43. The disc of claim 37 wherein the tab is fastened to the endplate by a fastener.

44. The disc of claim 37 wherein the tab is disposed within the channel so as to allow the core member to move within the channel in an anterior-posterior A-P direction.

45. The disc of claim 37 wherein the tab is disposed within the channel so as to prevent the core member from moving within the channel in an anterior-posterior A-P direction.

46. The disc of claim 37 wherein the tab has a body portion and an attachment portion extending from the body portion, wherein the attachment portion is shaped to attach to a vertebra.

47. The disc of claim 35 wherein the means comprises a pin and a slot associated with the core and prosthetic vertebral endplate.

48. The disc of claim 47 wherein the pin projects from the channel and the slot is disposed upon the core member.

49. The disc of claim 48 wherein the pin has a length and a width and the length is greater than the width.

50. The disc of claim 47 wherein the pin projects from the core member and the slot is disposed within the channel.

51. The disc of claim 35 wherein the means comprises a third component comprising a flexible material and is shaped to be inserted into the channel from the direction of the inner surface of the endplate housing the channel.

52. The disc of claim 35 wherein the means comprises a locking tab comprising first and second arms, the endplate further comprises first and second lateral wall portions comprising first and second respective recesses, wherein the first arm is shaped to be secured to the endplate in the the first recess, and the second arm is shaped to be secured to the endplate in the second recess.

53. A prosthetic vertebral endplate comprising:

i) an outer surface having a peripheral portion and an interior portion, the peripheral portion being adapted to mate with a vertebral body, and

ii) an inner surface comprising an opening forming a channel defining a channel depth,

wherein the peripheral portions of the inner and outer surfaces define a peripheral depth, and

wherein the channel depth is at least 80% of the peripheral depth.

54. The endplate of claim 53 wherein the channel depth is at least as great as the peripheral depth.

55. The endplate of claim 53 wherein the interior portion of the outer surface is adapted to mate with the vertebral body.

56. A prosthetic vertebral endplate comprising:

i) an outer surface having;

a) a peripheral portion adapted to mate with a vertebral body, and

b) an interior portion forming a keel having a width,

ii) an inner surface comprising an opening forming a channel having a width,

wherein the keel width is greater than the channel width.

57. An intervertebral motion disc comprising:

a) a first motion segment comprising;

i) an outer surface adapted to mate with a first vertebral body,

ii) an inner surface comprising a first articulation surface,

iii) a front and a back wall between the inner and outer surfaces, and

iv) a pair of slots formed in the first motion segment, each slot running substantially from the front wall and opening onto the front wall,

b) a second motion segment comprising;

i) an outer surface adapted to mate with a second vertebral body,

ii) an inner surface comprising a first articulation surface, and

wherein the articulation surfaces are adapted to produce an articulation interface.

58. The disc of claim 57 wherein the second motion segment comprises:

a prosthetic vertebral endplate comprising the outer surface, and

a core member comprising the first articulation surface.

59. The disc of claim 58 wherein the core member further comprises a second articulation surface, and the prosthetic vertebral endplate further comprises an articulation surface adapted to form a second articulation interface with the second articulation surface.

60. The disc of claim 57 wherein the second motion segment further comprises:

iii) a front and a back wall between the inner and outer surfaces, and

iv) a pair of slots formed in the segment, each slot running substantially from the front wall to the back wall and opening onto the front wall.

61. The disc of claim 57 wherein each slot is oriented in a direction substantially normal to the back wall.

62. The disc of claim 57 wherein each slot is oriented at a substantial angle to the back wall.

63. The disc of claim 57 wherein the slots are oriented substantially parallel to each other.

64. The disc of claim 57 further comprising:

v) a first and second sidewalls formed between the inner and outer surfaces, wherein a first slot is formed in the first sidewall and a second slot is formed in the second sidewall.

65. The disc of claim 57 wherein the inner surface comprises a raised inner portion having first and second raised sidewalls, wherein the first slot is formed in the first raised sidewall and the second slot is formed in the second raised sidewall.

66. A method of implanting an intervertebral motion disc, comprising the sequential steps of:

inserting into a disc space a partial motion disc comprising;

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a first vertebral body, and

ii) an inner surface comprising a first motion surface,

b) a second prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a second vertebral body,

ii) an inner surface comprising an opening forming a channel comprising opposing side walls, a first open end and a second motion surface, and

inserting into the open end of the channel a core member comprising;

i) a first surface adapted for motion with the first motion surface, and

ii) a second surface adapted for motion with the second motion surface,

wherein the core member is disposed within the channel and oriented therein to provide a first motion with the first motion surface and a second motion with the second motion surface.

67. The method of claim 66 wherein step a) comprises the sequential substeps of:

i) inserting the first prosthetic vertebral endplate, and

ii) inserting the second prosthetic vertebral endplate

68. The method of claim 67 wherein the first and second endplates are inserted substantially simultaneously.

69. The method of claim 68 further comprising the step of:

c) inserting into the open end of the channel a tab to prevent expulsion of the core member from the channel.

70. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a first vertebral body, and

ii) an inner surface comprising a first articulation surface comprising a non-ceramic material

b) a core member comprising;

i) a first articulation surface comprising a ceramic, and

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface.

71. The disc of claim 70 wherein the non-ceramic material is selected from the group consisting of a metal, a polymer, and a composite comprising carbon fiber.

72. The disc of claim 70 wherein the non-ceramic material is a metal.

73. The disc of claim 72 wherein the metal is a Ti alloy.

74. The disc of claim 72 wherein the metal is an alloy comprising Cr and Co.

75. The disc of claim 74 wherein the alloy further comprises Mo.

76. The disc of claim 72 wherein the metal is stainless steel.

77. The disc of claim 70 wherein the non-ceramic material is a polymer.

78. The disc of claim 70 wherein the non-ceramic material is a composite comprising carbon fiber.

79. The disc of claim 70 wherein the ceramic is a polycrystalline sintered ceramic.

80. The disc of claim 79 wherein the ceramic comprises at least 50 vol % alumina.

81. The disc of claim 80 wherein the alumina is characterized by a grain size of less than 3 um.

82. The disc of claim 80 wherein the alumina is characterized by a grain size of less than 1 um.

83. The disc of claim 80 wherein the ceramic is formed by a seeded gel process.

84. The disc of claim 80 wherein the ceramic comprises at least 50 vol % zirconia.

85. The disc of claim 80 wherein the zirconia is characterized by a grain size of less than 1 um.

86. The disc of claim 79 wherein the ceramic comprises at least 50 vol % of a mixture of alumina and zirconia.

87. The disc of claim 86 wherein the mixture comprises between 10 wt % and 30 wt % alumina.

88. The disc of claim 86 wherein the mixture comprises between 70 wt % and 90 wt % alumina.

89. The disc of claim 70 further comprising:

c) a second prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a second vertebral body, and

ii) an inner surface comprising a first articulation surface comprising a non-ceramic material.

90. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising a first articulation surface comprising a composite comprising carbon fiber,

b) a core member comprising;

i) a first articulation surface comprising a metal, and

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface.

91. The disc of claim 90 wherein the metal is a Ti alloy.

92. The disc of claim 90 wherein the metal is an alloy comprising Cr and Co.

93. The disc of claim 92 wherein the alloy further comprises Mo.

94. The disc of claim 90 wherein the metal is stainless steel.

95. The disc of claim 90 wherein the composite further comprises a polymer.

96. The disc of claim 95 wherein the polymer is a PAEK selected from the group consisting of PEEK, PEKK and PEK.

97. The disc of claim 96 wherein the PAEK is PEEK.

98. The disc of claim 90 wherein the carbon fiber comprises between 1 and 60% of the composite.

99. The disc of claim 90 wherein the carbon fiber comprises between 10 and 50% of the composite.

100. The disc of claim 90 wherein the carbon fiber comprises between 20 and 40% of the composite.

101. The disc of claim 90 wherein the carbon fiber comprises between 25 and 35% of the composite.

102. The disc of claim 90 wherein the carbon fiber is present in the composite as a continuous fiber.

103. The disc of claim 90 wherein the carbon fiber is present in the composite as a chopped fiber.

104. The disc of claim 103 wherein the chopped fiber has a median length of between 1 and 12 mm.

105. The disc of claim 90 wherein the composite further comprises a polymer, and the polymer and carbon fiber are homogeneously mixed throughout the composite.

106. The disc of claim 90 wherein the composite further comprises a polymer, and the polymer and carbon fiber are provided in laminated form within the composite.

107. A core member for articulation between first and second prosthetic vertebral endplates, comprising:

i) a first portion having a first articulation surface adapted for articulation with a first articulation surface of the first prosthetic vertebral endplate,

ii) a second portion having a second articulation surface adapted for articulation with a first articulation surface of the second prosthetic vertebral endplate, and

iii) a spring portion disposed between the first and second portions.

108. The core member of claim 107 wherein the first portion has a inner surface, the second portion has an inner surface, the spring portion comprises first and second ends, wherein the first end of the spring is connected to the inner surface of the first portion, and wherein the second end of the spring is connected to the inner surface of the second portion.

109. The core member of claim 107 wherein the spring portion comprises a surface having at least one recess therein.

110. The core member of claim 109 wherein the at least one recess is a helical recess.

111. The core member of claim 109 wherein the at least one recess comprises a plurality of discrete recesses.

112. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising a first articulation surface, and

b) a core member comprising a stiff component and a shock absorbing component having a spring constant of between 500 N/mm and 1000 N/mm, and comprising;

i) a first articulation surface,

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface.

113. The disc of claim 112 wherein the the shock absorbing component has a thickness of between about 1 mm and 5 mm.

114. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body,

ii) an inner surface comprising a first articulation surface, and

iii) a body portion therebetween comprising carbon fiber, and

b) a core member comprising;

i) a first articulation surface,

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface.

115. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body,

ii) an inner surface comprising an inner portion and a peripheral portion,

wherein at least one of the portions comprises a first articulation surface, and

b) a second prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a second vertebral body,

ii) an inner surface comprising an inner portion and a peripheral portion,

wherein at least one of the portions comprises a first articulation surface, and

c) a core member comprising;

i) a first articulation surface adapted for articulation with the first articulation surface of the first endplate, and

ii) a second articulation surface adapted for articulation with the first articulation surface of the second endplate,

d) means for limiting the translation motion of the core member,

wherein the core member is disposed between the endplates and oriented therein to produce a first articulation interface between the first articulation surface of the first endplate and the first articulation surface of the core member, and a second articulation interface between the first articulation surface of the second endplate and the second articulation surface of the core member, and a distance between the peripheral portions of the first and second endplates, and

wherein the distance between the peripheral portions is greater than the height of the core member.

116. An intervertebral motion disc comprising:

a) a first motion segment comprising;

i) an outer surface adapted to mate with a first vertebral body,

ii) an inner surface comprising a motion surface, and

iii) a body portion therebetween having an anterior portion and a posterior portion, and

b) a second motion segment comprising;

i) an outer surface adapted to mate with a second vertebral body,

ii) an inner surface comprising a motion surface, and

iii) a body portion therebetween having an anterior portion and a posterior portion, and

c) a ligament having a first end and a second end,

wherein the motion surfaces are adapted to form a motion interface, and

wherein the first end of the ligament is connected to the anterior portion of the first motion segment and the second end of the ligament is connected to the anterior portion of the second motion segment.

117. The disc of claim 116 wherein the ligament comprises a biocompatible flexible material.

118. The disc of claim 116 wherein the biocompatible flexible material is a polyester fiber weave.

119. The disc of claim 116 wherein the biocompatible flexible material is an elastic material.

120. The disc of claim 116 wherein the biocompatible flexible material is a polyvinyl material.

121. The disc of claim 116 wherein the biocompatible flexible material is a biological material capable of forming a scaffold for natural regeneration of a resected ligament.

122. An intervertebral spacer, comprising:

a) a first motion segment comprising;

i) an outer surface adapted to mate with a first vertebral body,

ii) an inner surface comprising a motion surface, and

iii) a body portion therebetween having an anterior portion and a posterior portion, and

b) a second motion segment comprising;

i) an outer surface adapted to mate with a second vertebral body,

ii) an inner surface comprising a motion surface, and

iii) a body portion therebetween having an anterior portion and a posterior portion, and

c) a spacing component having a first surface and an opposing second surface,

wherein the motion surfaces are adapted to form a motion interface, and

wherein the spacing component is disposed between the inner surfaces of the motion segments to substantially prevent motion at the motion interface.

123. The spacer of claim 122 wherein the spacing component is substantially U-shaped.

124. The spacer of claim 122 wherein the substantially U-shaped spacing component has first and second end portions disposed substantially parallel to each other.

125. The spacer of claim 124 wherein the first end of the spacing component is oriented substantially in the anterior-posterior direction.

126. The spacer of claim 124 wherein the first end of the spacing component is oriented at a substantial angle from the anterior-posterior direction.

127. The spacer of claim 122 wherein the spacing component is adapted to be inserted from the posterior direction.

128. The spacer of claim 122 wherein the spacing component comprises first and second independent bodies.

129. The spacer of claim 122 wherein the spacing component is adapted to be inserted from the anterior direction.

130. The spacer of claim 122 wherein the spacing component comprises a biologic enhancement selected from the group consisting of osteoinductive materials, osteoconductive materials, and osteogenic materials.

131. The spacer of claim 122 wherein the spacing component comprises stem cells.

132. An intervertebral motion disc comprising:

a) an upper prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with an upper vertebral body,

ii) an inner surface having a first articulation surface,

b) a lower prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a lower vertebral body, and

ii) an inner surface having a first articulation surface,

c) a core member comprising;

i) an upper articulation surface adapted for articulation with the first articulation surface of the upper endplate and having a radius, and

ii) a lower articulation surface adapted for articulation with the first articulation surface of the lower endplate and having a radius,

wherein the core member is disposed between the endplates and oriented therein to produce an upper articulation interface between the first articulation surface of the upper endplate and the upper articulation surface of the core member, and a lower articulation interface between the first articulation surface of the lower endplate and the lower articulation surface of the core member,

wherein the radius of the upper articulation surface of the core member is greater than the radius of the lower articulation surface of the core member.

133. The disc of claim 132 wherein the upper articulation interface forms a curved, non-spherical interface, and the lower articulation interface forms a spherical interface.

134. The disc of claim 133 wherein the upper articulation interface forms a cylindrical interface.

135. The disc of claim 132 wherein at least one interface is a conforming interface.

136. The disc of claim 132 wherein each interface is a conforming interface.

137. The disc of claim 132 wherein the upper articulation surface of the core member is convex, and the lower articulation surface of the core member is concave.

138. The disc of claim 132 wherein the upper articulation surface of the core member is concave, and the lower articulation surface of the core member is convex.

139. The disc of claim 132 wherein the radius of the upper articulation surface of the core member is at least 10 times greater than the radius of the lower articulation surface of the core member.

140. The disc of claim 132 wherein the radius of the upper articulation surface of the core member is between about 40 mm and about 100 mm, and the radius of the lower articulation surface of the core member is between about 10 mm and about 30 mm.

141. The disc of claim 132 wherein the radius of the upper articulation surface of the core member is between about 40 mm and about 80 mm

142. The disc of claim 132 wherein the radius of the upper articulation surface of the core member is at least 2 times greater than the radius of lower articulation surface.

143. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a first vertebral body,

ii) an inner surface having a first articulation surface,

b) a second prosthetic vertebral endplate comprising;

i) an outer surface adapted to mate with a second vertebral body, and

ii) an inner surface having a first articulation surface,

c) a core member comprising;

i) a first articulation surface adapted for articulation with the first articulation surface of the first endplate, and

ii) a second articulation surface adapted for articulation with the first articulation surface of the second endplate,

wherein the core member is disposed between the endplates and oriented therein to produce a first articulation interface between the first articulation surface of the first endplate and the first articulation surface of the core member, and a second articulation interface between the first articulation surface of the second endplate and the second articulation surface of the core member,

wherein the first articulation surface of the core member is spherical and the second articulation surface of the core member is curved and non-spherical.

144. The disc of claim 143 wherein the second articulation surface of the core member is cylindrical.

145. The disc of claim 143 wherein at least one interface is a conforming interface.

146. The disc of claim 143 wherein each interface is a conforming interface.

147. The disc of claim 143 wherein the first articulation surface of the core member is convex, and the second articulation surface of the core member is concave.

148. The disc of claim 143 wherein the first articulation surface of the core member is concave, and the second articulation surface of the core member is convex.

149. The disc of claim 143 wherein the first articulation surface of the core member is convex, and the second articulation surface of the core member is convex.

150. The disc of claim 143 wherein the first articulation surface of the core member is concave, and the second articulation surface of the core member is concave.

151. The disc of claim 143 wherein the radius of the first articulation surface of the core member is at least 3 times greater than the radius of the lower articulation surface of the core member.

152. A core member for articulation between first and second prosthetic vertebral endplates, comprising:

i) a first articulation surface adapted for articulation with a first articulation surface of the first prosthetic vertebral endplate,

ii) a second articulation surface adapted for articulation with the first articulation surface of the second prosthetic vertebral endplate,

wherein the first articulation surface is a portion of a sphere and the second articulation surface is a portion of a curved, non-spherical shape.

153. The core member of claim 152 wherein the curved non-spherical shape is a cylinder.

154. The disc of claim 152 wherein the first articulation surface of the core member is convex, and the second articulation surface of the core member is concave.

155. The disc of claim 152 wherein the first articulation surface of the core member is concave, and the second articulation surface of the core member is convex.

156. The disc of claim 152 wherein the first articulation surface of the core member is convex, and the second articulation surface of the core member is convex.

157. The disc of claim 152 wherein the first articulation surface of the core member is concave, and the second articulation surface of the core member is concave.

158. The disc of claim 152 wherein the radius of the first articulation surface of the core member is at least 3 times greater than the radius of the lower articulation surface of the core member.

159. A prosthetic vertebral endplate, comprising:

i) an outer surface adapted to mate with a first vertebral body to define a first attachment plane substantially parallel to the vertebral body endplate, and

ii) an inner surface comprising a substantially flat motion surface,

wherein the substantially flat motion surface and the first attachment plane define an angle α

.

160. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising a first articulation surface, and

b) a core member comprising;

i) a first articulation surface,

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface having a range of anterior-posterior A-P motion and a range of medial-lateral M-L motion,

wherein the range of A-P motion is between 1.5 and 50 times greater than the range of M-L motion.

161. The disc of claim 160 wherein the range of A-P motion is between 1.5 and 8 times greater than the range of M-L motion.

162. The disc of claim 160 wherein the range of A-P motion is between 4 and 8 times greater than the range of M-L motion.

163. The disc of claim 160 wherein the range of A-P motion is between 5 and 7 times greater than the range of M-L motion.

164. The disc of claim 160 wherein the range of A-P motion is between 5.5 and 6.5 times greater than the range of M-L motion.

165. The disc of claim 160 wherein the range of A-P motion is between 2 and 5 mm, and the range of M-L motion is between 0.25 mm and 2 mm.

166. The disc of claim 160 wherein the range of A-P motion is between 3 and 4 mm, and the range of M-L motion is between 0.25 mm and 1 mm.

167. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising;

a first articulation surface, and

a raised portion extending from the inner surface substantially adjacent the first articulation surface and having first and second ends, and

b) a removable tab having first and second ends,

wherein the tab is attached to the endplate and oriented so that the first end of the raised portion is substantially adjacent the first end of the tab, and the second end of the raised portion is substantially adjacent the second end of the tab to form an enclosure which substantially encloses the first articulation surface.

168. The disc of claim 167 further comprising:

c) a core member comprising a first articulation surface,

wherein the core member is disposed within the enclosure and oriented so that the first articulation surface of the core member and the first articulation surface of the first endplate form a first articulation interface.

169. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising a first articulation surface, and

iii) an elongated rail extending from the inner surface,

b) a core member comprising;

i) a first articulation surface, and

ii) an elongated slot for receiving the rail,

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface, and

the elongated rail is received in the elongated slot.

170. The disc of claim 169 wherein the rail comprises a plurality of pins.

171. An intervertebral motion disc comprising:

a) a first prosthetic vertebral endplate comprising;

i) an outer surface adapted to be attached to a first vertebral body, and

ii) an inner surface comprising a first articulation surface comprising a first metal having grains oriented in a first direction,

b) a core member comprising;

i) a first articulation surface comprising a metal having grains oriented in a second direction, and

wherein the first articulation surface of the core member and the first articulation surface of the first endplate are adapted to form a first articulation interface, and

wherein the first and second directions of grain orientation are not parallel.

172. The disc of claim 171 wherein the first direction is substantially perpendicular to the second direction.