Artificial Intervertebral Disc Replacement to Provide Dynamic Stability to the Lumbar Spine: A Finite Element Study.

Currently, intervertebral disc prostheses that are designed to restore mobility to a vertebral segment are possible for the lumbar spine. The ball-and-socket joint is a constrained design, wherein the rotational axis of the intervertebral joint is forced to pass through the center of the spherical surfaces that form the joint. One advantage of ball-and-socket joints versus unconstrained designs includes better shear stability, which results in sufficient flexibility.