An apparatus for replacing at least a portion of an intervertebral disc in a
spinal
column includes: a first member having a first vertebral contact surface for engagement
with an endplate of a first vertebral bone in the spinal column, and having a first
articulation surface that is defined at least by a concave arc having a radius
of curvature A about a first axis substantially perpendicular to an anterior-posterior
plane of the spinal column, and by a convex arc having a radius of curvature B
about a first axis substantially perpendicular to a lateral plane of the spinal
column; and a second member having a second vertebral contact surface for engagement
with an endplate of a second vertebral bone in the spinal column, and having a
second articulation surface that is defined at least by a convex arc having a radius
of curvature C about a second axis substantially perpendicular to the anterior-posterior
plane of the spinal column, and by a concave arc having a radius of curvature D
about a second axis substantially perpendicular to the lateral plane of the spinal
column, wherein: an intervertebral disc space is defined substantially between
the first and second endplates of the first and second vertebral bones, and the
radii of curvature of the first and second articulation surfaces are sized such
that the first and second articulation surfaces engage one another when the first
and second members are disposed in the intervertebral disc space to enable the
first and second vertebral bones to articulate in at least one of flexion, extension
and lateral bending.