CALCIUM CRYSTAL DEPOSITION IN THE LIGAMENTUM-FLAVUM OF THE LUMBAR SPINE

Objective. To investigate the histological and immunohistochemical pro perties of the lumbar ligamentum flavum with calcium crystal depositio n. Methods. We examined the histological characteristics of the ligame ntum flavum of the lumbar spine containing calcium deposits, obtained from 16 surgical cases with symptomatic lumbar spinal stenosis. Sectio ns of the ligaments were also immunostained for elastase, chymotrypsin and S-100 protein, and examined by energy dispensive X-ray microanaly sis and scanning electron microscopy. The results were compared with t hose of ligaments without calcium deposits. Results. The elastic fibre s of ligaments with calcium deposits showed marked degeneration (irreg ular arrangement and fragmentation of the fibre bundles) and nodular g ranulomatous lesions. Calcium crystal deposits were present in this ar ea and in the nodular granulomatous areas. The calcified areas were su rrounded by neutrophils and new small blood vessels. Immunostaining fo r elastase and chymotrypsin was positive in these areas, and S-100 pro tein-containing chondrocytes were detected around and within the calci fied areas. Calcium pyrophosphate dihydrate crystals were identified i n the calcified areas in all patients.Conclusion. Nodular degeneration of the elastic fibres of the ligament is probably caused by the actio n of proteolytic enzymes. Degeneration results in small granulomatous areas that form the nidus for calcium crystal deposition. Accumulated neutrophils, and S-100 protein-containing chondrocytes appear to preci pitate the deposition of calcium crystals in the granulomatous lesions of the degenerated lumbar ligamentum flavum.