Myxomatous degeneration of the ligamentum flavum of the lumbar spine

Abstract

Study design: Report of two cases of acute lumbar nerve root compression caused by myxomatous degeneration of the ligamentum flavum. Objective: To report a rare cause of acute lumbar nerve root compression. Setting: Orthopaedic department, Osaka, Japan. Summary of background data: Two patients, both 50-year-old men presenting with signs and symptoms suggestive of acute lumbar nerve root compression were found to have a ligamentum flavum mass. The masses were removed and the patients regained normal function postoperatively. Methods: To reveal the nature of the mass, histopathological studies were made. Continuous sections were prepared from the removed mass lesions. The sections were stained with hematoxylin and eosin, van Gieson's stain, azan stain, periodic acid Schiff reaction, Alcian blue stain and von Kossa's stain. Results: Histological examination revealed myxomatous degeneration of the ligamentum flavum. No elastic fibers were found at the degeneration site. Diffuse mucopolysaccharide deposition was found at the degeneration site, however, no cyst was found. Collagen fibers were not increased. Hypertrophy or ossification of the ligamentum flavum was not recognized in the sections. At a follow-up examination over 2 years later, the patients were free of symptoms and the findings of a neurological examination were normal. Conclusion: Two cases of myxomatous degeneration of the ligamentum flavum of the lumbar spine were reported, which have seldom been described as the cause of acute lumbar nerve root compression.