Ultrastructure of the human interspinous ligament and ligamentum flavum. A preliminary study

The ultrastructure of ligamenta flava (LF) and interspinous ligaments (ISL) obtained from four patients who underwent surgery for vertebral fracture (control group) and five patients operated for disc herniation was studied. The fine structure of LF was composed of elastic and elaunin fibers. Small diameter collagen fibrils were found between the elastic system fibers. The ISL was constituted predominantly of collagen fibrils. Elastic fibers were seen in the most ventral part of the ligament. In ISL and LF of the control group, the cells were fibroblastic-like cells. Chondrocytes were present only near their attachment sites. The proteoglycans were demonstrated between the collagen fibrils, and they appeared to form a regular interfibrillar linking. In ligaments obtained from patients with disc herniation, several modifications were found. The fibroblasts transformed into chondrocytic cells, which were surrounded by a pericellular matrix rich in proteoglycan filaments. A few cells that had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement also were evidenced. The proteoglycan filaments were randomly oriented to the collagen fibrils.