Light and electron microscopic morphology of the ligamenta flava in lumbar stenosis.

CLINICAL RELEVANCE. It is still unclear whether, in lumbar stenosis, LP bulge into the spinal canal because they are thickened or they are simply pushed in the bulging position by hypertrophied articular processes. Our study does not clarify this issue, but may contribute to clarify the role of the LF in the compression of the neural structures. The changes that we observed in stenotic patients (fibrosis, chondrometaplasia, calcifications, elastic fibre degeneration) lead to a decrease in elasticity of the ligaments. An elastic tissue has the ability to be deformed under traction and return to its normal size parallel to the decrease of the elastic tension. The LF do not normally bulge into the spinal canal when spine is in the neutral position. when spine is extended, they remain undeformed until such extension occurs that their elastic tension is completely satisfied, after which the LF bulge into the spinal canal. The degree of extension necessary to satisfy the elastic tension of the LF is as smaller as lesser is the elasticity of the tissue. These observations suggest that in stenotic patients the ligaments, due to their reduced elasticity, lay bulge into the spinal canal in the standing position even if they are normal in thickness, and the bulging increases progressively, parallel to the increase of degenerative changes.