Patent ID: 8142505

Claim:
An apparatus for replacing at least a portion of an intervertebral disc in a spinal column between endplates of a first vertebral body and a second vertebral body of a spinal column, the apparatus comprising: (a) a first member having a first vertebral contact surface for engagement with the first vertebral body endplate, and having a first articulation surface; and (b) a second member having a second vertebral contact surface for engagement with the second vertebral body endplate, and having a second articulation surface, wherein an intervertebral spacing is defined as the axial component of a line extending between a centroid of said first vertebral contact surface and a centroid of said second vertebral contact surface, and wherein said first articulation surface and said second articulation surface form at least part of an articulation arrangement configured such that, when loaded with compressive axial force: (i) said first and second vertebral contact surfaces are supported against the compressive force to ensure a predefined minimum intervertebral spacing; (ii) said second member is displaceable relative to said first member in motion corresponding to axial rotation, anterior-flexion and posterior extension, and lateral bending, each of said motions having a corresponding range of motion; and (iii) said intervertebral spacing increases as a smooth function of angular displacement from a neutral position over at least part of said range of motion in each direction for each of said axial rotation, anterior-flexion and posterior extension, and lateral flexion, thereby providing non-impact motion attenuation.