title: Thoracic myelopathy caused by ossification of ligamentum flavum of which fluorosis as an etiology factor.
abstract: OBJECTIVE
  To evaluate the clinical feature, operative method and prognosis of thoracic ossification of ligamentum flavum caused by skeletal fluorosis.
  
  
  METHODS
  All the patients with thoracic OLF, who underwent surgical management in the authors' hospital from 1993-2003, were retrospectively studied. The diagnosis of skeletal fluorosis was made by the epidemic history, clinical symptoms, radiographic findings, and urinalysis. En bloc laminectomy decompression of the involved thoracic levels was performed in all cases. Cervical open door decompression or lumbar laminectomy decompression was performed if relevant stenosis existed. The neurological statuses were evaluated with the Japanese Orthopaedic Association (JOA) scoring system preoperatively and at the end point of follow up. Also, the recovery rate was calculated.
  
  
  RESULTS
  23 cases have been enrolled in this study. Imaging study findings showed all the cases have ossification of ligamentum flavum together with ossification of many other ligaments and interosseous membranes, i.e. interosseous membranes of the forearm in 18 of 23 (78.3%), of the leg in 14 of 23 (60.1%) and of the ribs in 11 of 23 (47.8%). Urinalysis showed markedly increased urinary fluoride in 14 of 23 patients (60.9%). All the patients were followed up from 12 months to 9 years and 3 months, with an average of 4 years and 5 months. The JOA score increased significantly at the end of follow up (P = 0.0001). The recovery rate was 51.83 +/- 32.36%. Multiple regression analysis revealed that the preoperative JOA score was an important predictor of surgical outcome (p = 0.0022, r = 0.60628). ANOVA analysis showed that patients with acute onset or too long duration had worse surgical result (P = 0.0003).
  
  
  CONCLUSIONS
  Fluorosis can cause ossification of thoracic ligamentum flavum, as well as other ligaments. En bloc laminectomy decompression was an effective method. Preoperative JOA score was the most important predictor of surgical outcome. Patients with acute onset or too long duration had worse surgical outcome.
authors.affiliation: Spine surgery department, Tianjin hospital, No, 406 Jiefangnan Road, Hexi District, Tianjin City, 300211, People's Republic of China. wangwwb@yahoo.com.cn
authors.forename: Wenbao
authors.initials: W
authors.lastname: Wang
authors.forename: Linghua
authors.initials: L
authors.lastname: Kong
authors.forename: Heyuan
authors.initials: H
authors.lastname: Zhao
authors.forename: Ronghua
authors.initials: R
authors.lastname: Dong
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.forename: Yun
authors.initials: Y
authors.lastname: Lu