Lumbar Spinal Stenosis Due to a Large Calcified Mass in the Ligamentum Flavum
A 68-year-old male had a 12-month history of right leg pain and intermittent claudication. He developed increasing right lateral thigh and calf pain with walking and squatting. The pain was severe and caused limitation in his daily life; he had difficulty in walking and standing for more than 10 minutes. Motor function of the right extensor hallucis longus revealed weakness, but sensory disturbance was not evident. He had no bowel or bladder dysfunction. Straight-leg-raising tests were negative in both limbs. The patellar and Achilles tendon reflexes were within the normal range and pathological reflexes were not identified. The patient had a history of bronchial asthma, and he had been prescribed nonsteroidal anti-inflammatory drugs and vasodilatory agents for lumbar spinal stenosis.\nAlthough the plain radiographs of flexion and extension in the lumbar spine showed no evidence of instability, a myelogram demonstrated spinal stenosis at the L4/5 level (). A computed tomography scan was performed for analysis of the affected area (), revealing a huge calcified mass on the ligamentum flavum at the right-hand side of the lumbar spinal canal. Magnetic resonance imaging (MRI) revealed compression of the cauda equina at the L4/5 level, the compression mass showed low intensity with T1- and T2-weighted MRI ().\nWe performed a laminotomy at the L4/5 level with resection of the calcified mass from the ligamentum flavum. The mass had compressed the nerve root on the right-hand side at the L5 nerve root of in the foramina of the spinal canal (). The calcified mass in ligamentum flavum is 13 mm long and 8 mm wide (). The macro-specimen, which was dried in air, revealed a white, hard mass () with a chalky appearance. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) of the mass were performed with the Hitachi S-3500N Natural-SEM (Hitachi, Tokyo, Japan) and Horiba EMAX-7000 X-ray microanalyzer (Horiba, Kyoto, Japan) (). Based on EPMA, 2 chemical elements showed peaks-calcium (Ca) and phosphorus (P) (), with all 4 areas () showing the same 2 peaks. Subsequently, fourier-transformed infrared microspectroscopy (FTIR) was performed using JEOL WINSPEC-50 (JEOL, Tokyo, Japan) and IR-MAU (JEOL, Tokyo, Japan), to reveal the chemical structure of the calcified mass (). The FTIR peaks were determined as being approximately 1,033, 1,417, and 1,652 in this material. The peak of approximately 1033 showed mainly calcium triphosphate (Ca3[PO4]2) and calcium phosphate (CaHPO4), referring to our data for pure Ca3(PO4)2. The peaks of approximately 1,417 and 1,652 showed proteins, referring to our data for pure proteins. Collectively, the SEM, EPMA, and FTIR findings suggest that the calcified mass consisted mostly of Ca3(PO4)2 and CaHPO4 intermixed with protein and water (H2O). Histological examination of the elastic fibers and calcified mass was performed with hematoxylin and eosin, elastica Van Gieson, and Azan staining (). The calcified mass was located in the degenerated ligamentum flavum, with a well-delineated margin (). Degeneration of elastic fibers was accompanied by a proliferation of collagen fibers among the elastic fibers (). Loss of elastic fibers was defined as a focal loss of elastic fibers replaced by a cicatricial proliferation of collagen fibers ().