Classification and pathomorphology of lumbar stenosis.

A classification system based on pathologic anatomy distinguishing between three types of lumbar stenosis is reported: stenosis of the spinal canal, isolated stenosis of the nerve root canal, and stenosis of the intervertebral foramen. Each type of stenosis is classified as primary, secondary, combined or mixed. Pathomorphological pictures which may represent the vertebral bodies, the neural arch and the discoligamentous structures in the various forms of stenosis, among which degenerative spondylolisthesis, are examined. Finally, the authors describe the pathologic modifications occurring in the nervous structures as the possible consequence of a lumbar stenosis.