Prosthetic intervertebral discs, systems including such prosthetic
intervertebral discs, and methods for using the same are described. The
subject prosthetic discs include upper and lower endplates separated by a
compressible core member. The subject prosthetic discs exhibit stiffness
in the vertical direction, torsional stiffness, bending stiffness in the
saggital plane, and bending stiffness in the front plane, where the
degree of these features can be controlled independently by adjusting the
components, construction, and other features of the discs.