Lumbar Spinal Stenosis: How Is It Classified?

Gregory D. Schroeder, MD; Mark F. Kurd, MD; Alexander R. Vaccaro, MD, PhD, MBA


J Am Acad Orthop Surg. 2016;24(12):843-852. 

In This Article

Anatomy and Etiology

Spinal stenosis most commonly occurs at L4–5, with up to 91% of patients having neural compression at this level.[6] It is most often the result of a degenerative process, which begins in the intervertebral disk as the number of viable cells, water, and proteoglycan content decrease in the nucleus pulposus. As the nucleolus pulposus degenerates, disk height diminishes, and there is buckling and bulging of the anulus fibrosus.[8] These changes lessen the ability of the anterior column of the spine to absorb stress, leading to an abnormal transfer of force to the posterior elements. The increased stress through the facets results in facet joint hypertrophy, osteophyte formation, and ligamentum flavum buckling and hypertrophy.[8] The combination of these changes leads to a narrowing of the spinal canal and compression of the neural elements.