Molecular alterations of human lumbar yellow ligament related to the process of intervertebral disk degeneration and stenosis.

Purpose: The objective of this study was to analyze the layers of yellow ligament in lumbar canal stenosis and disk herniation.

Methods: Eighteen ligaments were harvested from patients with lumbar spinal canal stenosis. Twenty-nine normal samples from lumbar spine disk herniation patients served as control. All surgical procedures were the same. Ligaments were stained in hematoxylin and eosin; picrosirius-hematoxylin for collagen; Weigert's resorcin-fuchsin for elaunin, oxytalan and elastic fibers; and transmission electron microscopy. Immunohistochemistry was performed for Il-6; Il-10; and CD-31, PGP9.5. Results are described in means and standard error (mean ± SE), and all analyses adopted the significance level of P < 0.05.

Results: Spinal stenosis ligaments were 2.5 × thicker. Control superficial ligaments presented a large number of thick, compact collagen fibers and a significant amount of oxytalan and mature elastic fibers. The deep layer presented a large number of mature elastic fibers. In the stenosis group, collagen was thinner and compacted in both layers. There was no difference in the interleukin profile among groups. The deep portion of the stenosis group presented a higher number of vessels and nerves.

Conclusion: Two layers compose the elastic system of the normal ligamentum flavum, where the deep portion is mainly responsible for its elasticity (elaunin fibers), while its resistance depends on the concentration of oxytalan fibers, which are more present in the superficial layer. Ligamentum flavum in the stenosis samples presents more mononuclear infiltrate and more degraded elastic fibers with a higher number of vessels in its deep portion. These slides can be retrieved under Electronic Supplementary Material.