INTERVERTEBRAL DISC IMPLANT AND METHOD FOR RESTORING FUNCTION TO A DAMAGED FUNCTIONAL SPINAL UNIT USING SUCH AN INTERVERTEBRAL DISC IMPLANT

摘要

Presented are intervertebral disc implants (20) for the total replacement of an intervertebral disc (3) within the cervical spine, comprising two articulating members (21, 25), where the inferior member (21) on its upper surface is adapted for engaging an upper vertebral body (1) and its lower surface has an convex projection (23), and the inferior member (25) on its lower surface is adapted for engaging a lower vertebral body (4) and its upper surface has an saddle shaped projection (27), which is convex in its longitudinal anterior-posterior profile and which is concave in its transversal lateral profile with the general same diameter as the convex projection (23) of the superior member (21), therefore allowing flexion-extension-motion over a variable center of rotation, and in addition allowing rotation and lateral bending through a second independent center of rotation which is located above the intervertebral disc implant (20) at a distance which is defined by the diameter of the convex projection (23) of the superior member (21), therefore allowing coupled motion for rotation and lateral bending independently from flexion/extension, and therefore more closely replicating the natural kinematics of a cervical disc.