Intervertebral prosthesis
An intervertebral prosthesis for insertion between adjacent vertebrae includes upper and lower prosthesis plates locatable against respective vertebrae and having opposing, concavely curved recesses therein, and a core located between the plates. The core has opposed, convexly curved surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core. The opposed surfaces of the core and the recesses of the plates have cooperating spherical curvatures. The recess of each plate surrounds a locating peg projecting centrally from the base of the recess and is bounded by an annular rim, such that the annular rims of the plates are arranged to contact one another at a predetermined limit of sliding movement of the plates over the core. The peg locates loosely in an opening located centrally in a curved surface of the core, whereby the plates can slide over the core in all directions while the peg holds the core captive.
1. A system for insertion of an intervertebral prosthesis between adjacent vertebrae, the system comprising:
an intervertebral prosthesis comprising:
a first prosthesis plate having a major surface to engage a first vertebra and a cooperating surface disposed opposite the major surface;
a second prosthesis plate comprising a major surface to engage a second vertebra and a cooperating surface disposed opposite the major surface;
a core located between the first and second plates, wherein the cooperating surfaces of the first and second plates are arranged to cooperate with the core to form an articulate joint;
a peg projecting centrally from the cooperating surface of the first plate; a central opening in the core;
wherein the peg locates loosely in the opening of the core, whereby the plates can slide over the core while the peg holds the core captive;
wherein the cooperating surface of the second plate has no centrally projecting peg;
a first annular rim disposed around the cooperating surface of the first plate, the first rim having an empty groove;
a second annular rim disposed around the cooperating surface of the second plate, the second rim having an empty groove; and
wherein each groove is adapted to facilitate manipulation and holding of the prosthesis with an appropriate instrument while the prosthesis is placed in the intervertebral space; and
an instrument for placing the intervertebral disc, the instrument configured to hold the prosthesis at the grooves of the first and second annular rims.
2. The system according to claim 1 , wherein the cooperating surface of the second plate is spherical and the core has a cooperating spherical surface.
3. The system according to claim 1 , wherein the central opening in the core is a blind recess extending partway through the core.
4. The system according to claim 1 , wherein the first and second prosthesis plates are each formed in one piece and configured to be received entirely within the disc space.
5. The system according to claim 1 , wherein the first and second prosthesis plates include upstanding elongated projections on the major surfaces.
6. The system according to claim 1 , wherein the cooperating surface of the first plate is complementary in shape to a curved surface of the core of the prosthesis.
7. The system according to claim 1 , wherein the peg and the central opening are complementary in shape.
8. The system according to claim 1 , wherein the first plate is an upper plate and the second plate is a lower plate, wherein only the lower plate includes the centrally projecting peg.
9. The system according to claim 1 , wherein the major surfaces comprise machined serrated finishes.
10. The system according to claim 1 , wherein the first and second plates are formed of titanium.
11. The system according to claim 1 , wherein the core is formed of high molecular weight polyethylene.