Patent ID: 7208014

Claim:
An intervertebral spacer device comprising: first and second plate members, each having first and second plate surfaces thereof, said plate members being disposed in a spaced apart relationship such that said first plate surfaces oppose one another, and said second plate surfaces face in opposite directions; and a convex element by which said first and second plate members are coupled to one another, by said convex element being mounted to said second plate member and maintained against said first plate member, and being disposed such that at least a portion of a load applied to said second plate surfaces is transmitted to said convex element, said mounting of said convex element to said second plate member establishing a center of rotation between said first and second plate surfaces about which said first and second plate members rotate relative to one another, said mounting of said convex element to said second plate member and said maintenance of said convex element against said first plate member together preventing said first and second plate members from becoming uncoupled from one another under a load applied to said first and second plate surfaces; wherein said convex element is maintained against said first plate member by a retaining wall and a retaining ring, the retaining wall being on the first plate member and circumferentially surrounding a wide end of said convex element, the retaining ring extending from the retaining wall such that at least a portion of the wide end of said convex element is disposed between said first plate member and the retaining ring, such that said convex element is held against said first plate member by the retaining ring and the retaining wall, and wherein the retaining wall and the retaining ring define a substantially enclosed area over said first plate surface of said first plate member and wherein upon implantation of said assembled spacer device said convex element is movable relative to said first plate member within the enclosed area.