[Study of the microscopic structure of the posterior ligaments of the lumbar spine].

Biopsies of supraspinous ligaments (SSL), interspinous ligaments (ISL) and ligamenta flava (LF), removed at operation from 12 patients aged from 17 to 77 years, were examined by light microscopy, scanning electron microscopy and transmission electron microscopy. The structure of normal ligaments was first established, and then a comparison between normal and pathological ligaments was made. It was found that the SSL and ISL were composed of collagen, while the LF contained predominantly elastic fibres. In normal ligaments, a helical arrangement of the collagen fibrils was found. The fascicles were characterized by a regular waviness. Proteoglycan filaments were demonstrated in the three types of ligaments, forming a regular interfibrillar linking between adjacent collagen fibrils. Degenerative changes were found in most of the ligaments obtained from patients with disc herniation. On light microscopy, metaplasia into fibrocartilage and calcification was commonly seen. Ultrastructurally, the flattened fibroblasts were replaced by chondrocytic cells, and an accumulation of proteoglycans with a random arrangement and a cellular necrosis was encountered. The relevance of these degenerative changes to the mechanical properties and to low back pain is discussed.