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 assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a core with at least one curved surface;
movably coupling a the core with a first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein each of the at least one curved surface surfaces of the core comprises a metal, wherein coupling the core with the first metallic endplate comprises:
heating the first endplate sufficiently to cause it to expand;
contacting a portion of the core with the expanded endplate; and
allowing the first endplate to cool, thus contracting to form the interference fit around the portion of the core; and
contacting the core with a second metallic endplate.
2. A method as in claim 1 , wherein coupling the core with the first metallic endplate comprises:
heating the first endplate sufficiently to cause it to expand;
contacting a portion of the core with the expanded endplate; and
allowing the first endplate to cool, thus contracting to form the interference fit around the portion of the core.
3. A method as in claim 1 , wherein coupling the core with the first endplate comprises forming the endplate around the core.
4. A method as in claim 1 , wherein coupling the core with the first endplate comprises engaging a peripheral protrusion of the core with a peripheral restraining structure of the first endplate.
5. A method as in claim 1 , for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a core with at least one curved surface;
movably coupling the core with a first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein each of the at least one curved surfaces of the core comprises a metal, wherein coupling the core with the first endplate comprises screwing the core into the first endplate via complementary threads on the core and the first endplate; and
contacting the core with a second metallic endplate.
6. A method for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a first metallic endplate having a first bearing surface;
movably coupling a core with the first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein a bearing surface of the core corresponds to a shape of the first bearing surface, wherein the core has circumferentially spaced recesses and at least one of the first or second plates has a plurality of pins or pegs opposing corresponding recesses of the core; and
contacting the core with a second metallic endplate.
7. A method as in claim 6 , for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a first metallic endplate having a first bearing surface;
movably coupling a core with the first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein a bearing surface of the core corresponds to a shape of the first bearing surface, wherein coupling the core with the first metallic endplate comprises:
heating the first endplate sufficiently to cause it to expand;
contacting a portion of the core with the expanded endplate; and
allowing the first endplate to cool, thus contracting to form the interference fit around the portion of the core; and
contacting the core with a second metallic endplate.
8. A method as in claim 6 , wherein coupling the core with the first endplate comprises forming the endplate around the core.
9. A method as in claim 6 15, wherein coupling the core with the first endplate comprises engaging a peripheral protrusion of the core with a the projecting restraining structure of the first endplate, wherein the projecting restraining structure engages and retains the peripheral protrusion.
10. A method as in claim 6 , for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a first metallic endplate having a first bearing surface;
movably coupling a core with the first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein a bearing surface of the core corresponds to a shape of the first bearing surface, wherein coupling the core with the first endplate comprises screwing the core into the first endplate via complementary threads on the core and the first endplate; and
contacting the core with a second metallic endplate.
11. A method for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a first metallic endplate having a first bearing surface;
movably coupling a core with the first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein a bearing surface of the core corresponds to a shape of the first bearing surface, wherein coupling the core with the first metallic endplate comprises passing outwardly facing surfaces of a peripheral structure on the core through opposing inwardly facing surfaces of a projecting structure on at least one of the first or second metallic plates, and wherein a distance between the outwardly facing surfaces of the peripheral structure on the core is less than a distance between the opposing inwardly facing surfaces of the projecting structure so that the peripheral structure on the core will pass through the projecting structure to restrain peripheral movement of the core; and
contacting the core with a second metallic endplate.
12. A method as in claim 11, wherein the interference fit retains the core against the first bearing surface of the first metallic plate but allows the core to slide freely within a limit defined by the projecting structure.
13. A method as in claim 11, wherein the projecting structure comprises a pin or peg projecting from at least one of the first or second metallic plates.
14. A method as in claim 11, wherein:
the projecting structure projects from the first or second plate by a distance;
the bearing surface of the core that corresponds to the shape of the first bearing surface of the first metallic plate is a first core bearing surface;
the core further comprises a second core bearing surface configured to engage the second metallic plate; and
a central region of the first core bearing surface is separated from a central region of the second core bearing surface by a core thickness greater than the distance that the projecting structure projects from the first or second metallic plate.
15. A method for assembling a prosthetic disc for insertion between adjacent vertebrae, the method comprising:
providing a first metallic endplate having a first bearing surface;
movably coupling a core with the first metallic endplate to form an interference fit between the core and the first metallic endplate, wherein a bearing surface of the core corresponds to a shape of the first bearing surface, wherein the interference fit retains the core against the first bearing surface of the first metallic plate but allows the core to slide freely within a limit defined by a projecting structure; and
contacting the core with a second metallic endplate.
16. A method as in claim 15, wherein the projecting structure comprises a pin or peg projecting from at least one of the first or second metallic plates.