Intra-spinal new bone formation and spinal cord compression in familial hypophosphataemic vitamin D resistant...

Four patients with familial hypophosphataemic vitamin D resistant osteomalacia and spinal cord compression are reported. Three of these patients were treated by decompressive laminectomy and each made a good recovery. At surgery new bone formation in the ligamentum flavum and thickening of laminae were found to be responsible for the canal stenosis and cord compression. Two of these four patients, and 10 others were examined by computed tomography to determine the incidence, site and extent of any intra-spinal new bone formation. Facet joint hypertrophy and thickened laminae were observed at some level in all the patients, but much the most important cause of spinal canal stenosis was new bone formation in the ligamentum flavum, in the mid and lower thoracic spine, occurring at several, but mainly contiguous vertebral levels. Severe spinal canal stenosis was found in eight of the 12 patients scanned. No obvious relation was found between the presence of intra-spinal new bone formation and the clinical severity of the disease or the presence of extra-skeletal ossification in para-spinal and other sites. Computed tomography offers a simple, non-invasive technique for identifying those patients at risk of cord compression from new bone formation.