Patent ID: 7001433

Claim:
A spinal artificial disc device for being implanted between adjacent upper and lower vertebrae spaced apart in an axial direction, the artificial disc device comprising: upper and lower arcuate central bearing surface portions having a configuration generally extending in the axial direction for projecting toward and slidingly engaging against respective facing vertebral surfaces of the upper and lower vertebrae; upper and lower outer bearing surface portions generally extending in a radial direction outward from corresponding upper and lower central bearing surface portions such that the upper and lower outer bearing surface portions project along the vertebral surfaces, the upper and lower central bearing surface portions being spaced in the axial direction by a greater distance than the outer bearing surface portions are spaced in the axial direction, the central and outer bearing surface portions sharing compressive loads on the vertebral surfaces for minimizing vertebral subsidence about the axially extending central bearing surface portions; and junctures between the axially extending upper and lower central bearing surface portions and the radially extending corresponding upper and lower outer bearing surface portions, wherein the central bearing surface portions are formed on a central ball bearing having an outer spherical surface, and the outer bearing surface portions are formed on an outer annular bearing, the outer annular bearing including an inner side surface facing the outer spherical surface of the central ball bearing and being configured to allow relative rotation between the central ball bearing and the outer annular bearing.