Patent ID: 8236055

Claim:
An intervertebral prosthesis comprising: a) an interbody disc having upper and lower surfaces for engaging the faces of adjacent vertebral bodies between which a natural disc has been partially or wholly removed, an exterior wall and one or more generally vertically oriented continuous or discontinuous bone channels of limited cross-sectional area to enable bone to form and fuse into one or more continuous or discontinuous struts between the vertebral bodies; b) the disc having a stiffness sufficient to support the vertebral bodies in their natural spaced relationship while allowing limited motion and being flexible enough when subjected to a predetermined load to alter the distance between the vertebrae engaging surfaces and transfer sufficient energy to the bone strut(s) to create one or more conditions of nonunion joints or pseudoarthrosis at locations along the strut(s); and c) the disc being further arranged to limit the movement thereof to an amount which is sustainable by the disc without resulting in fatigue failure during an anticipated life span, wherein the stiffness of the disc is within the range of about 50 to 4000 N/mm, wherein the total cross-sectional area of the bone channel(s) is about 35% or less of the total area of one of the disc vertebral body engaging faces, wherein the disc includes upper and lower rings separated by a partial ring joined to the upper and lower rings by a bridged portion defining a serpentine slot extending between the rings and an inner tubular appendage supported by one or both of the upper and lower rings, the appendage defining the bone channel(s), the disc further including cooperating means located on the upper and lower rings to limit the axial travel of the disc, the serpentine slot accommodating the infusion of soft tissue therein, wherein the tubular appendage comprises one or more downwardly extending tubular posts carried by the upper ring and cooperating upwardly extending nipple(s) carried by the lower ring, the post(s) and nipple(s) providing the means to limit the axial travel of the disc.