Degenerative spondylolisthesis is the abnormal translation of one vertebral body relative to an adjacent vertebral body. It is often more simply referred to as a “slip.”
Degenerative spondylolisthesis can be further categorized as follows.
Ventral translation of one vertebral body relative to an adjacent vertebral body (on lateral/sagittal imaging)
Dorsal translation of one vertebral body relative to an adjacent vertebral body (on lateral/sagittal imaging)
Lateral translation of one vertebral body relative to an adjacent vertebral body (on AP/coronal imaging)
This abnormal translation can contribute to central canal and foraminal stenosis with compression of neural structures.
Patients may present with neurogenic claudication or focal radiculopathies and sensorimotor deficits.Degenerative spondylolisthesis can also contribute to the development of scoliosis and kyphosis, which can manifest with back pain.
The cause of degenerative spondylolisthesis is usually multifactorial due to a combination of disc degeneration and facet arthropathy. When there is a concomitant defect in the pars coupled with a slip, this is referred to as spondylolysis.
There are different grades of spondylolisthesis defined by the percentage of slip relative to the anteroposterior length of the adjacent vertebral body.
More information on the different grades of spondylolisthesis is given in the Spondylolisthesis section of the Spine deformities module in the AO Surgery Reference.
The degree of slippage can be exacerbated when patients are standing or by dynamic movement.
Comparison of supine to standing imaging or flexion-extension x-rays can suggest a degree of instability in patients with degenerative spondylolisthesis.
Dynamic instability is confirmed when there is translation greater than 3mm of the posterior vertebral body line of one vertebra to an adjacent one.
These patients will be best treated with stabilization/fusion.