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 by a plurality of concave arcs each having
a respective radius of curvature about a corresponding axis substantially perpendicular
to an anterior-posterior plane of the spinal column, and a plurality of convex
arcs each having a respective radius of curvature about a corresponding 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 by a plurality of convex arcs each having a radius of curvature about
a corresponding axis substantially perpendicular to the anterior-posterior plane
of the spinal column, and a plurality of concave arcs each having a radius of curvature
about a corresponding 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.