Spondylo is the root word for several terms describing different conditions of the spine seen on MRI, and because of this overlap it may give rise to confusion. Let’s start with some definitions.
Spondylosis is a general term referring to a usually diffuse degenerative and age related process involving facet arthropathy and hypertrophy, hypertrophic vertebral changes, and ligamentous changes including lengthening and buckling. This latter process produces apparent ligamentous thickening which is sometimes inaccurately referred to as ligamentous hypertrophy. Spondylosis is manifested somewhat differently in the cervical spine than in the lumbar spine. In the cervical spine stresses are primarily rotational and to a lesserextent axial loading and spondylosis is seen in ligaments, uncovertebral(uncinate) hypertrophy and spondylotic ridges AKA disc-osteophyte complex. The disc osteophyte complex is a protruding ridge composed of chronically bulging disc encased with bony hypertrophy and granulation or scar tissue and is different from a focal or pure disc herniation, which are less common in the cervical spine. In the lumbar regions, stressors are primarily related to axial loading (weight), and spondylosis results in ligamentous and facet changes as well as marginal osteophytes. Discogenic changes in the lumbar spine range from broad based symmetric disc bulging to focal disc protrusions or extrusions.
Spondylolisthesis refers to a change in position of one vertebral body with relation to another, usually anterolisthesis. Spondylolisthesis comes in three flavors: degenerative, postoperative, and spondylolytic. Degenerative spondylolisthesis occurs when the vertebral body has slipped forward on the vertebra below as a result of degenerative processes and spondylosis and usually results in varying degrees of both canal and foraminal stenosis.
Spondylolysis is a term used to indicate either fracture or congenital defect in the Pars Interarticularis which is a small bony segment leading to and supporting the articular facet in the posterior elements. When there is a pars defect or fracture, the vertebral body may slip forward (spondylolisthesis)while the posterior column may remain fixed or slip backwards slightly. This results in canal widening with foraminal narrowing.
Postoperative spondylolisthesis occurs when laminectomy has been performed and, similar to pars defect or fracture, results in canal widening with or without foraminal narrowing.