US Patent 7022138 Spinal interbody fusion device and method

A disc replacement spinal interbody fusion device is provided having a central sleeve with oppositely left and right-hand threaded axial bores with different diameters. Circumferential threaded apertures are located on the sleeve and open into the sleeve bores. The device has two opposing plates which are oval-shaped and centrally, axially bored. Each plate has a perpendicular shaft with an axial bore which communicates with the plate bore. In situ, axial loading of the spinal column upon the fusion device creates a bending moment manifested by a flexing action of the plates to generate opposing axial directional forces which replicate the physiological function of shock absorption, load bearing and load transmission.