Intervertebral prosthetic disc with metallic core
A prosthetic disc for insertion between adjacent vertebrae includes a core having upper and lower curved surfaces and upper and lower plates. At least one of the curved surfaces of the core is metallic, and in some embodiments the entire core is metallic. Each plate has an outer surface which engages a vertebra and a metallic inner curved surface which is shaped to slide over one of the curved surfaces of the core. In some embodiments, the center of rotation of the core is free to move relative to the upper and lower metallic plates. In some embodiments, one or more channels extend across one or both of the curved surfaces of the core for allowing passage of bodily fluid to promote lubrication between the core and at least one of the plates.
1. A method for implanting an intervertebral disc prosthesis between adjacent vertebrae, the method comprising:
implanting an upper plate against a lower surface of an upper vertebral body;
implanting a lower plate against an upper surface of a lower vertebral body;
disposing a core between the upper and lower plates, the core having bearing surfaces, wherein disposing the core between the plates comprises passing a peripheral structure on the core through a projecting structure on at least one of the plates, and wherein the peripheral structure has a diameter smaller than the diameter of the projecting structure so that the peripheral structure will pass through the projecting structure to restrain peripheral movement of the core; and
allowing the core to float with a mobile center of rotation between the upper and lower plates.
2. A method as in claim 1 , wherein implanting each of the plates comprises sliding a fin on each plate into a corresponding groove formed in its respective vertebral body.
3. A method as in claim 1 , further comprising restraining peripheral movement of the core with the projecting structure on the at least one of the plates and no projecting structure on the other of the at least one plates.
4. A method as in claim 1 , wherein the core has a height between the upper and lower bearing surfaces and a width, and wherein a core maximum height is smaller than the core width.
5. A prosthetic disc for insertion between adjacent vertebrae, the prosthetic disc comprising:
a core having upper and lower bearing surfaces;
first and second plates, each plate having an outer surface which engages a vertebra and an inner bearing surface which slides and translates over the corresponding bearing surface of the core, wherein a center of rotation of the core is free to move relative to the upper and lower plates;
a peripheral restraining structure having a diameter and being located at an outer edge of the bearing surface of the first plate and integrally formed with the first plate, the peripheral restraining structure comprising an inwardly directed flange which forms an overhang; and
wherein the core has a peripheral structure with a diameter smaller than the diameter of the restraining structure which extends into the overhang during sliding motion of the plates over the core.
6. A prosthetic disc as in claim 5 , wherein the flange extends continuously around a lateral circumference of the core.
7. A prosthetic disc as in claim 5 , wherein at least one of the bearing surfaces is spherical.
8. A prosthetic disc as in claim 5 , wherein the peripheral restraining structure defines a stop structure to limit relative inclination of the plates during sliding movement of the plates over the core.
9. A prosthetic disc as in claim 5 , wherein the peripheral restraining structure comprises a U-shaped peripheral flange.
10. A prosthetic disc as in claim 5 , wherein no peripheral restraining is located on the second plate.
11. A method for insertion of a prosthetic disc between adjacent vertebrae, the method comprising:
providing a prosthetic disc comprising:
a mobile core having upper and lower bearing surfaces;
first and second plates, each plate having an outer surface which engages a vertebra and an inner bearing surface which slides and translates over the corresponding bearing surface of the core, wherein a center of rotation of the core is free to move relative to the upper and lower plates; and
a peripheral restraining structure 9 configured to hold the core against the bearing surface of at least one of the plates during sliding movement of the plates over the core, the peripheral restraining structure comprising a peripheral structure extending over at least a portion of the periphery of the core and a projecting structure on one of the first and second plates, which projecting structure engages and retains the peripheral structure, wherein a diameter of the peripheral structure of the core is smaller than a diameter of the projecting structure of the plate;
inserting the core between the first and second plates; and
inserting the prosthetic disc between adjacent vertebrae.
12. The method as in claim 11 , wherein the peripheral restraining structure is on an upper one of the first and second plates.
13. The method as in claim 11 , wherein the peripheral restraining structure is on a lower one of the first and second plates.
14. The method as in claim 11 , wherein the upper and lower bearing surfaces of the core are curved surfaces.
15. The method as in claim 14 , wherein the curved surfaces are spherical.
16. The method as in claim 11 , wherein the projecting structure of the peripheral restraining structure is located on one of the first and second plates and not on the other of the first and second plates.
17. The method as in claim 11 , wherein the core and the plates comprise the same material.
18. The method as in claim 11 , wherein the restraining structure is adapted to contact an opposing plate to limit relative inclination of the plates during sliding movement of the plates over the core.
19. The method as in claim 11 , wherein the core is a rigid core.
20. A method for insertion of a prosthetic disc between adjacent vertebrae, the method comprising:
providing a prosthetic disc comprising:
a core having upper and lower bearing surfaces; and
first and second plates, each plate having an outer surface which engages a vertebra and an inner bearing surface which slides and translates over the corresponding bearing surface of the core, wherein a center of rotation of the core is free to move relative to the upper and lower plates; and
a peripheral restraining structure located at an outer edge of the bearing surface of the first plate and integrally formed with the first plate, the peripheral restraining structure comprising an inwardly directed flange which forms an overhang;
inserting the prosthetic disc between adjacent vertebrae, wherein a peripheral structure of the core extends into the overhang during sliding motion of the plates over the core, wherein a diameter of the peripheral structure of the core is smaller than a diameter of the flange of the plate.
21. The method as in claim 20 , wherein the projecting structure of the peripheral restraining structure is located on one of the first and second plates and not on the other of the first and second plates.
22. The method as in claim 20 , wherein the restraining structure is adapted to contact an opposing plate to limit relative inclination of the plates during sliding movement of the plates over the core.
23. The method as in claim 20 , wherein the core is a rigid core.