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 method of making assembling a prosthetic disc with a mobile core, the method comprising:
providing a first plate having a first surface configured to engage a vertebra and an opposite bearing surface;
providing a second plate having a first surface configured to engage a vertebra and an opposite bearing surface;
providing a rigid mobile core, the core having first and second bearing surfaces configured to cooperate with the bearing surfaces of the first and second plates to allow the first and second plates to slide and translate over the core when implanted between adjacent spinal vertebrae and a lateral edge between the first and second bearing surfaces;
further providing on said rigid mobile core, two or more recesses circumferentially spaced apart about the periphery of the core; and
further providing on said first plate two or more pegs, each peg opposing one of the two or more circumferentially spaced recesses, wherein the two or more circumferentially spaced recesses extend in a direction radially inward from the lateral edge of the core toward a center portion of the core; and
assembling the mobile core between the first and second plates to form an assembled configuration for implantation between adjacent spinal vertebrae in which the core is retained between the first and second plates with the two or more pegs received in the spaced apart recesses.
2. A method as in claim 1 , wherein the pegs are configured to extend into the recesses during sliding motion of the plates over the core.
3. A method as in claim 1 , wherein the second bearing surface of the core is spherical.
4. A method as in claim 3 , wherein the bearing surface of the second plate is a concave spherical surface which matches a curvature of the spherical surface of the core.
5. A method as in claim 1 , wherein both of the first and second bearing surfaces of the core are spherical.
6. A method as in claim 1 , wherein the core has a substantially circular perimeter.
7. A method as in claim 1 , wherein the core is symmetrical about a central, equatorial plane which bisects the core laterally.
8. A method as in claim 1 , wherein the lateral edge is a continuous lateral edge.
9. A method as in claim 1 , wherein cooperation between the recesses and the pegs ensures that the core is held captive between the plates upon implantation between adjacent spinal vertebrae.
10. A method as in claim 1 , wherein the assembled configuration allows anterior, posterior and lateral motion of the core with respect to the first plate.
11. A method as in claim 1 , wherein the assembled configuration allows anterior, posterior and lateral motion of the core with respect to the second plate.
12. A method as in claim 1 , wherein the two or more recesses are surrounded by recess surfaces of the core and wherein assembling the first and second plates and the mobile core comprises passing outwardly facing portions of the recesses surfaces of the core through opposing inwardly facing surfaces of the two or more pegs on the first plate to restrain peripheral movement of the core.
13. A method as in claim 1 , wherein the two or more pegs are configured to retain the core in the assembled configuration for implantation between adjacent spinal vertebrae but allow the core to slide within a limit defined by the two or more recesses when implanted between adjacent spinal vertebrae.
14. A method as in claim 1 , wherein the two or more pegs are configured to retain the core in the assembled configuration while allowing lateral translation of the core and preventing the core from extending laterally beyond the plates when the assembled prosthetic disc is implanted between adjacent spinal vertebrae.