Pathology and pathogenesis of lumbar spondylosis and stenosis.

Study of autopsy specimens of the lumbar spine makes it possible to construct a spectrum of pathologic change. Progressive degenerative changes in the posterior joints lead to marked destruction and instability. Similar changes in the disc result in herniation, internal disruption, and resorption. Combined changes in posterior joint and disc sometimes produce entrapment of a spinal nerve in the lateral recess, central stenosis at one level, or both of these conditions. Changes at one level often lead, over a period of years, to multilevel spondylosis and/or stenosis. Developmental stenosis is an enhancing factor in the presence of a small herniation or moderate degenerative stenosis. Lesions such as major trauma, spondylolisthesis, those following spinal fusion, Paget's disease, and fluorosis, on occasion act directly to produce central or lateral stenosis.