Intervertebral prosthetic disc
A prosthetic disc for insertion between adjacent vertebrae includes upper and lower plates, a core disposed between the plates, and at least one projection extending from at least one of the upper and lower curved surfaces of the core into at least one recess of one of the inner surfaces of the plates. The recess is oversize with respect to the projection to allow sliding movement of the plate over the core while retaining the core between the plates during such sliding movement. The projection(s) may include a rod extending through an axial hole in the core, multiple surface features of the core, or the like.
1. An intervertebral prosthetic disc for insertion between adjacent vertebrae, the disc comprising:
first and second plates having outer surfaces locatable against the respective vertebrae and inner, bearing surfaces;
a core between the plates, the core having upper and lower bearing surfaces complementary in shape to the inner, bearing surfaces of the plates to allow the plates to slide over the core; and
a flexible tie member extending laterally through the core and having ends outside the core which are engaged with the first plate to retain the core between the plates when the plates slide over the core.
2. A prosthetic disc as in claim 1 , wherein the flexible tie member extends through a lateral passage through the core and includes ends engaged with at least one of the first and second plates.
3. A prosthetic disc as in claim 1 , wherein the flexible tie member comprises a flexible cable or cord.
4. An intervertebral prosthetic disc for insertion between adjacent vertebrae, the disc comprising:
first and second plates each having inner surfaces and outer surfaces locatable against the respective vertebrae;
a core located between the inner surfaces of the plates, the core allowing the plates to articulate with respect to one another; and
an elongated flexible tie member engaged with the inner surface of the first plate to retain the core between the plates when the plates articulate with respect to one another, wherein the elongate flexible tie member goes into openings in the inner surface of the first plate.
5. A prosthetic disc as in claim 4 , wherein the elongated flexible tie member is a flexible cable or cord.
6. A prosthetic disc as in claim 4 , wherein the elongated flexible tie member extends through a lateral passage through the core.
7. A prosthetic disc as in claim 4 , wherein the elongated flexible tie member enters passages in the first plate.
8. A prosthetic disc as in claim 7 , wherein the elongated flexible tie member comprises ends which are anchored in the passages.
9. A prosthetic disc as in claim 4 , wherein the elongated flexible tie member holds the core captive during movement of the plates in flexion, extension, and translation.
10. A prosthetic disc as in claim 9 , wherein the elongated flexible tie member allows rotational movements of the plates relative to the core.
11. A prosthetic disc as in claim 4 , wherein the elongated flexible tie member allows rotational movements of the plates relative to the core.
12. A prosthetic disc as in claim 4 , wherein the core comprises a polymer.
13. A prosthetic disc as in claim 4 , wherein the first and second plates comprise titanium.
14. A prosthetic disc as in claim 13 , wherein the outer surfaces of the first and second plates comprise titanium plasma spray coating.
15. A prosthetic disc as in claim 4 , wherein the core is solid unitary core.
16. A prosthetic disc as in claim 4 , further comprising at least one fin extending from the outer surfaces of the plates.
17. A prosthetic disc as in claim 16 , wherein each fin is oriented in a straight line in an anterior-posterior direction.
18. A prosthetic disc as in claim 4 , wherein the outer surfaces of the plates are textured to enhance attachment of the plates to the vertebrae.
19. A prosthetic disc as in claim 18 , wherein the outer surfaces further comprise a plasma sprayed titanium.
20. A method of retaining a core in an intervertebral prosthetic disc, the method comprising:
providing first and second plates each having inner surfaces and outer surfaces locatable against respective vertebrae;
locating a core between the inner surfaces of the plates;
allowing the plates to articulate with respect to one another and with respect to the core; and
retaining the core between the plates with an elongated flexible tie member engaged with the inner surface of the first plate, wherein the elongate flexible tie member goes into openings in the inner surface of the first plate.
21. A method as in claim 20 , wherein the elongated flexible tie member is a flexible cable or cord.
22. A method as in claim 20 , wherein the elongated flexible tie member extends through a lateral passage through the core.
23. A method as in claim 20 , wherein the elongated flexible tie member enters passages in the first plate.
24. A method as in claim 23 , wherein the elongated flexible tie member comprises ends which are anchored in the passages.
25. A method as in claim 20 , wherein the elongated flexible tie member holds the core captive during movement of the plates in flexion, extension, and translation.
26. A method as in claim 20 , wherein the elongated flexible tie member allows rotational movements of the plates relative to the core.
27. A method as in claim 20 , wherein the core comprises a polymer.
28. A method as in claim 20 , wherein the first and second plates comprise titanium.
29. A method as in claim 28 , wherein the outer surfaces of the first and second lower plates comprise titanium plasma spray coating.
30. A method as in claim 20 , wherein the core is solid unitary core.
31. A method as in claim 20 , further comprising at least one fin extending from the outer surfaces of the plates.
32. A method as in claim 31 , wherein each fin is oriented in a straight line in an anterior-posterior direction.
33. A method as in claim 20 , wherein the outer surfaces of the upper and lower plates are textured to enhance attachment of the plates to the vertebrae.
34. A method as in claim 33 , wherein the outer surfaces are plasma spray coated with titanium.