What is High-grade Spondylolisthesis?

Spondylolisthesis is when one vertebra slips forward over the vertebra below it. High-grade spondylolisthesis is when the vertebra has slipped forward significantly. Spondylolisthesis is given a grade based on how far forward the vertebra has slipped. This grade is important in determining treatment options.

• Grade I is a less than 25% slip
• Grade II is a 25-49% slip
• Grade III is a 50-74% slip
• Grade IV is a 75-99% slip
• Grade V is for a vertebra that has fallen off the vertebra below it (This extreme case of spondylolisthesis is called spondyloptosis.)

High-grade spondylolisthesis is Grade III or above. Almost all high-grade spondylolisthesis patients have a component of congenital dysplasia at L5 and S1 (L5 is the last vertebra in the lumbar spine; S1 is the sacrum, the region of the spine directly below the lumbar region). Congenital means "present at birth," and dyplasia is an abnormality in development. Congenital dysplasia affects L5 and S1 in a few ways: it makes the posterior elements of the vertebrae thin, small, and atrophic (likely to waste away). It is extremely uncommon to develop high-grade spondylolisthesis if there is not a component of this congenital dysplasia.

Patients with degenerative spondylolisthesis (a slip caused by the effects of aging on the spine) or patients with isthmic spondylolisthesis (a slip caused by a defect in the pars interarticularis, a particular region of your vertebra) can have a high-grade spondylolisthesis if the vertebra has slipped forward far enough. High-grade spondylolisthesis can cause spinal stenosis, nerve compression, and progressive back and leg pain.