Mechanical Yield of the Lumbar Annulus: A Possible Contributor to Instability

Mechanical yield of soft tissues occurs due to deformation beyond the elastic limit and is characterized by an irreversible decreased stiffness. Annular fiber yield may lead to decreased segmental stability, resulting in disc prolapse and potentially subsequent degenerative spondylolisthesis. Yield properties of the lumbar annulus have not been well defined in literature and the contribution of yielded fibers on segmental stability remains undefined.