Methods: Ligamenta flava obtained from nine patients with lumbar disc herniation and ten patients with lumbar stenosis were studied at histologic, histochemical, and ultrastructural levels. Lumbar ligamenta flava removed from six patients who underwent surgeries for thoracolumbar fractures were used as controls.
Results: Ligamenta flava from control subjects consisted of large elastic fibers, thin bundles of collagen fibers, and few spindle-shaped fibroblasts. In proximity to the laminal insertion, the ligaments had fibrocartilagineous features. In the control subjects who were age 50 or older, the cells decreased in number and areas that had fewer and thinner elastic fibers and a more abundant collagen component were visible occasionally. In patients with disc herniation, the ligaments had similar morphologic features to those of the controls of similar ages. The ligamenta flava from patients with lumbar stenosis showed areas of fibrosis in which the cells were often represented by actively synthesizing fibroblasts and areas of chondroid metaplasia. Degenerating elastic fibers were seen occasionally, while calcified areas were observed often.
Conclusions: Ligamenta flava undergo slight fibrotic and chondrometaplastic changes with aging. No peculiar changes occur in patients with disc herniation. In spinal stenosis, fibrotic changes, chondroid metaplasia, and calcification reduce the elasticity of the ligaments, which may thus bulge into the spinal canal in the standing position even if they are normal in thickness.