Lumbar spinal stenosis due to a large calcified mass in the ligamentum flavum

We describe a rare case of lumbar spinal stenosis due to a large calcified mass in the ligamentum flavum. This patient presented with a 12-month history of severe right leg pain and intermittent claudication. A computed tomography scan was performed, revealing a large calcified mass on the ligamentum flavum at the right-hand side of the lumbar spinal canal. We performed a laminotomy at the L4/5 level with resection of the calcified mass from the ligamentum flavum. The findings of various analyses suggested that the calcified mass consisted mostly of Ca3(PO4)2 and calcium phosphate intermixed with protein and water. The calcified mass in the ligamentum flavum was causing lumbar spinal stenosis. Surgical decompression by resection of the mass was effective in this patient. The calcified material was composed mainly of elements derived from calcium phosphate. Degenerative changes in the ligamentum flavum of the lumbar spine may have been involved in the production of this calcified mass.