Patent ID: 6918934

Claim:
An intervertebral spacer device, comprising: first and second plates, said plates being disposed in a spaced apart relationship such that a plate surface of said first plate faces a plate surface of said second plate, the facing surfaces being inner surfaces, and alternative faces of each plate being outer surfaces; and at least one restoring force providing element disposed between the inner surfaces of said first and second plates, and disposed such that a compressive load applied to the outer surfaces of said first and second plates is counteracted by said at least one restoring force providing element said at least one restoring force providing element including at least one slotted belleville washer; wherein said at least one slotted belleville washer has a convex shape when unloaded, and assumes a flatter shape as the slots widen when compressively loaded; and wherein said at least one slotted belleville washer is unloaded when no load is applied to said outer surfaces, and is loaded when said compressive load is applied to said outer surfaces, wherein at least one of said first and second plates comprises a retaining element that maintains a wide end of the at least one belleville washer adjacent the inner surface of the at least one of said first and second plates and wherein the retaining element comprises a retaining wall behind which the wide end of the washer is disposed, and wherein the retaining element further comprises a retaining ring that has the washer disposed between its inner surface and the inner surface of the at least one of said first and second plates.