Toroid-shaped spinal disc

An intervertebral implant comprising:

• a first component having a first articulating surface, the first articulating surface being generally convex;
• a second component defining an aperture and having a second articulating surface and a first bone engaging portion for engaging a first vertebra, the second articulating surface being generally concave and articulable with the first articulating surface for retaining motion between the first vertebra and a second vertebra;
• and
• a third component coupled to the first component opposite the first articulating surface, the third component defining a second bone engaging portion for engaging the second vertebra,
• wherein the second articulating surface has a larger radius of curvature than the first articulating surface such that a portion of the first articulating surface extends into the aperture of the second component.

An intervertebral implant comprising:

• a first component having a first articulating surface, the first articulating surface being generally convex;
• a second component in the shape of a toroid defining an aperture and having a second articulating surface, the second articulating surface being generally concave and articulable with the first articulating surface for retaining motion between a first vertebra and a second vertebra;
• a third component coupled to the first component opposite the first articulating surface, the third component defining a first bone engaging portion for engaging a first vertebra;
• and
• a fourth component coupled to the second component opposite the second articulating surface so as to be disposed about a periphery of the aperture, the fourth component defining a second bone engaging portion,
• wherein the second articulating surface has a larger radius of curvature than the first articulating surface such that a portion of the first articulating surface extends into the aperture of the second component.