An intervertebral implant for implantation between an upper vertebra and a lower vertebra having a central axis. The implant may have a first member with a top surface for contacting at least a portion of the upper vertebra and a bottom surface as well as a second member with a top surface and a bottom surface for contacting at least a portion of the lower vertebra. An elastic spacer may be disposed between the first member and the second member. The bottom surface of the first member and the top surface of the second member may have a first constraint means and the other of the bottom surface of the first member and the top surface of the second member may be provided with a second constraint means, to limit the amount of lateral movement between the first and second members. Additionally, the constraint means may be sized and configured such that a gap with a width greater than zero is provided at least transversely to the central axis between the first and second constraint means in an unloaded state.
