Myxomatous degeneration of the ligamentum flavum of the lumbar spine

Study design: Report of two cases of acute lumbar nerve root compression ca used 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 w ith signs and symptoms suggestive of acute lumbar nerve root compression we re 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 m ade. Continuous sections were prepared from the removed mass lesions. The s ections were stained with hematoxylin and eosin, van Gieson's stain, azan s tain, periodic acid Schiff reaction, Alcian blue stain and yon Kossa's stai n. Results: Histological examination revealed myxomatous degeneration of the l igamentum flavum. No elastic fibers were found at the degeneration site. Di ffuse mucopolysaccharide deposition was found at the degeneration site, how ever, 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 sy mptoms and the findings of a neurological examination were normal. Conclusion: Two cases of myxomatous degeneration of the ligamentum flavum o f the lumbar spine were reported, which have seldom been described as the c ause of acute lumbar nerve root compression.