Prosthetic disc for intervertebral insertion
A prosthetic disc for insertion between adjacent vertebrae includes a core having upper and lower curved surfaces, upper and lower plates, and peripheral restraining structure on at least one of the upper plate, the lower plate and the core. Each plate has an outer surface which engages a vertebra and an inner curved surface which slides over the curved surface of the core. The peripheral restraining structure serves to hold the core against a curved surface of at least one of the plates during sliding movement of the plates over the core.
1. A prosthetic disc for insertion between adjacent vertebrae, the prosthetic disc comprising:
upper and lower plates having outer surfaces locatable against the respective vertebrae, inner surfaces, and two or more restraining structures on an inner surface of at least one of the plates, wherein at least one of the inner surfaces of the upper and lower plates is a curved inner surface; and
a mobile core removable disposed between the inner surfaces of the upper and lower plates, the core arranged to slide and translate with respect to one or more of the upper or lower plates when the prosthetic disc is implanted, wherein the mobile core has a circumference;
wherein the two or more restraining structures on at least one of the plates are projections spaced apart about the circumference of the core and discrete from one another to hold the core captive between the plates.
2. The prosthetic disc as in claim 1 , wherein each restraining structure of the two or more restraining structure comprises a flange extending from a periphery of the upper or lower plate.
3. The prosthetic disc as in claim 1 , wherein the inner surfaces of both the upper and lower plates are concave.
4. The prosthetic disc as in claim 1 , further including at least one fin extending from each of the outer surfaces of the plates.
5. The prosthetic disc as in claim 1 , wherein the mobile core has at least one convexly curved surface having a radius of curvature which matches a curvature of the curved inner surface.
6. The prosthetic disc as in claim 1 , wherein the mobile core has a width greater than a height.
7. The prosthetic disc as in claim 1 , wherein the two or more restraining structures surround the core.
8. The prosthetic disc as in claim 1 , wherein the mobile core comprises an annular structure, and the two or more restraining structures are configured to engage the annular structure to hold the core captive between the plates during sliding movement of the plate over the core.
9. The prosthetic disc as in claim 8 , wherein the annular structure comprise a single, continuous groove.
10. The prosthetic disc as in claim 8 , wherein the annular structure comprise two or more recesses, wherein the recesses are discrete and spaced apart circumferentially.
11. The prosthetic disc as in claim 10 , wherein each projection has a single corresponding recess in the core.
12. The prosthetic disc as in claim 1 , wherein at least one restraining structure is located on the upper plate.
13. The prosthetic disc as in claim 1 , wherein at least one restraining structure is located on the lower plate.
14. The prosthetic disc as in claim 1 , wherein at least one restraining structure is located on the upper plate and at least one restraining structure is located on the lower plate.
15. A prosthetic disc as in claim 1 , wherein the mobile core is removable from between the inner surfaces of the upper and lower plates by lifting the mobile core out of the restraining structure on the at least one plate.
16. A prosthetic disc as in claim 1 , wherein the projections are pins or pegs.