Intervertebral disc having translation

1. 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 first 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, and

b) a tab shaped for insertion into the channel, wherein the tab is disposed within the channel and comprises a body portion and deformable arms extending from the body portion,

wherein each deformable arm comprises a wing extending therefrom,

wherein the body portion of the endplate further comprises second and third sidewalls defining a first width and the wings define a wingspan, and wherein the wingspan exceeds the first width of the channel, and

wherein each of the second and third sidewall of the endplate further comprises a socket extending therein, thereby defining opposing sockets, and

wherein the wings are shaped to be received within the opposing sockets.

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

3. The end plate 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, and

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

wherein the means for retaining the core member within the channel comprises a tab shaped for insertion into the channel, wherein the tab is disposed within the channel,

wherein the tab comprises a body portion and deformable arms extending from the body portion,

wherein each deformable arm comprises a wing extending therefrom,

wherein the body portion of the endplate further comprises second and third sidewalls defining a first width and the wings define a wingspan, and wherein the wingspan exceeds the first width of the channel, and

wherein each of the second and third sidewall of the endplate further comprises a socket extending therein, thereby defining opposing sockets, and

wherein the wings are shaped to be received within the opposing sockets.

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 1000 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 2% greater than the diameter of the core.

35. The disc of claim 21 wherein the means comprises a pin and a slot associated with the core and prosthetic vertebral endplate.

36. The disc of claim 35 wherein the pin projects from the channel and the slot is disposed upon the core member.

37. The disc of claim 36 wherein the pin has a length and a width and the length is greater than the width.

38. The disc of claim 35 wherein the pin projects from the core member and the slot is disposed within the channel.

39. 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,

wherein the means for limiting the translation motion of the core member comprises a tab shaped for insertion into the channel, wherein the tab is disposed within the channel,

wherein the tab comprises a body portion and deformable arms extending from the body portion,

wherein each deformable arm comprises a wing extending therefrom,

wherein the body portion of the endplate further comprises second and third sidewalls defining a first width and the wings define a wingspan, and wherein the wingspan exceeds the first width of the channel, and

wherein each of the second and third sidewall of the endplate further comprises a socket extending therein, thereby defining opposing sockets, and

wherein the wings are shaped to be received within the opposing sockets.

40. 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,

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,

d) means for limiting a 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,

wherein the first articulation interface has 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,

wherein the means for limiting the translation motion of the core member comprises a tab shaped for insertion into the channel, wherein the tab is disposed within the channel,

wherein the tab comprises a body portion and deformable arms extending from the body portion,

wherein each deformable arm comprises a wing extending therefrom,

wherein the body portion of the endplate further comprises second and third sidewalls defining a first width and the wings define a wingspan, and wherein the wingspan exceeds the first width of the channel, and

wherein each of the second and third sidewall of the endplate further comprises a socket extending therein, thereby defining opposing sockets, and

wherein the wings are shaped to be received within the opposing sockets.

41. The disc of claim 40 wherein the range of A-P motion is between 1.5 and 8 times greater than the range of M-L motion.

42. The disc of claim 40 wherein the range of A-P motion is between 4 and 8 times greater than the range of M-L motion.

43. The disc of claim 40 wherein the range of A-P motion is between 5 and 7 times greater than the range of M-L motion.

44. The disc of claim 40 wherein the range of A-P motion is between 5.5 and 6.5 times greater than the range of M-L motion.

45. The disc of claim 40 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.

46. The disc of claim 40 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.