Patent ID: 8182536

Claim:
An intervertebral implant for implantation between an upper vertebra and a lower vertebra, the intervertebral implant having a central axis and comprising: a first member with a top surface for contacting at least a portion of the upper vertebra and a bottom surface, the first member having a peripheral edge; a second member with a top surface and a bottom surface for contacting at least a portion of the lower vertebra, the second member having a peripheral edge; an elastomeric material disposed between said bottom surface of said first member and said top surface of said second member, the elastomeric material is a single continuous material extending from and between the peripheral edges of the first and second members and the bottom surface of the first member and the top surface of the second member; wherein one of said bottom surface of said first member and said top surface of said second member is provided with first constraint means and the other of said bottom surface of said first member and said top surface of said second member is provided with second constraint means, said first and second constraint means being sized and configured to limit the amount of lateral movement between said first and second members; wherein said first and second constraint means are sized and configured such that a gap with a width greater than zero is provided at least transversely to said central axis between said first and second constraint means in an unloaded state; wherein said first constraint means is configured as a central pin, said central pin having a width and a convex tip for permitting a tilting motion between said first and second members; and wherein the second constraint means comprises two separate curved concave protrusions surrounding the first constraint means, the two separate concave protrusions defining two opposite openings, the openings being smaller than the width of the central pin, wherein the two opposite openings allow relative movement of the first and second members in the antero-posterior direction to differ from the amount of relative movement in the lateral direction.