An intervertebral disc prosthesis comprises a superior endplate, an
inferior endplate, and an intermediate core positioned between the
endplates. The core comprises a central disc portion and a radial flange.
The central disc portion of the core is defined by a superior bearing
surface and inferior bearing surface. The radial flange of the core
includes a first portion that extends radially outward from the central
disc portion of the core. The radial flange also includes a second
portion that extends axially from the first portion of the flange. The
second portion of the flange extends a substantially greater distance
toward the inferior endplate than toward the superior endplate. In one
embodiment, the second portion of the flange extends completely to the
inferior endplate and engages the inferior endplate when the inferior
endplate is in a neutral position relative to the core.