Patent ID: 7582115

Claim:
An intervertebral prosthesis, comprising: a first prosthetic end plate ( 20 ) and a second prosthetic end plate ( 30 ), as well as a prosthetic core ( 10 ) located between the first prosthetic end plate ( 20 ) and the second prosthetic end plate ( 30 ), wherein the first prosthetic end plate ( 20 ) has a hemispherical shaped recess ( 21 ) with a radius (R 3 ), in which a hemispherical segment ( 11 ) of the prosthetic core ( 10 ) is seated, wherein the second prosthetic end plate ( 30 ) has an essentially planar recess ( 31 ), in which an essentially flat segment ( 15 ) of the prosthetic core ( 10 ) sits, which transitions to the hemispherical segment ( 11 ), the essentially planar recess ( 31 ) narrowing conically inward to form an essentially planar recess overhang; wherein the essentially planar recess ( 31 ), having an outer wall ( 33 ), exhibits an essentially round cross-section with a diameter (d 1 ), wherein the essentially flat segment ( 15 ) exhibits an essentially round cross-section with a diameter (d 2 ), wherein the diameter (d 2 ) of the essentially flat segment ( 15 ) is smaller than the diameter (dl) of the essentially planar recess ( 31 ), a circumferential groove ( 18 ) located on the prosthetic core ( 10 ) where the essentially flat segment ( 15 ) transitions to the hemispherical segment ( 11 ) such that the hemispherical segment ( 11 ) forms a hemispherical segment overhang; wherein the essentially flat segment ( 15 ) has an outer surface ( 16 ) that corresponds to the outer wall ( 33 ) and narrows conically inward, narrowing from the seating of the essentially flat segment ( 15 ) in the essentially planar recess ( 31 ) towards the hemispherical segment ( 11 ); and wherein the essentially planar recess overhang inserts in the groove ( 18 ) and the hemispherical segment overhang projects over the essentially planar recess overhang to prevent dislodgment of the prosthetic core ( 10 ) when the prosthetic core ( 10 ) is slid to one side of the essentially planar recess ( 31 ).