Thoracic Ossification of Ligamentum Flavum Caused By Skeletal Fluorosis: Breaking the Etiopathological Barrier -Answer to the Crippling Disease of the Society

Background: Thoracic ossification of ligamentum flavum (OLF) caused by skeletal fluorosis is rare [1]. Only six patients had been reported in the English literature. This study is the second study to the best of our knowledge in literature. Aims and Objectives: To evaluate the causation of ossification of ligamentum flavum due to fluorosis in accordance with reports from the first clinical series of this disease. Exact etiopathogenesis of thoracic ossification of yellow ligament is not known and causation due to fluorosis is rare, so this study was hypothesized [2]. Materials and Methods: This is a prospective study of patients with thoracic OLF due to skeletal fluorosis who underwent surgical management at the NIMS hospital between 2017 and 2018. A total of 16 cases were enrolled, (56.25%), 9 males and 7 (43.75%) females, age ranging from 37 to 62 years (mean 50.5 years). Imaging showed OLF together with ossification of interosseous membranes, including interosseous membranes of the forearm (14/16 patients 87.5%).Urinalysis showed a markedly high urinary fluoride level in 15 of 16 patients (93.75%).Ossified ligamentum flavum sent for estimation of fluoride levels in 16 patients showed high fluoride level in the bone ash prepared from the oyl in 15 patients and other structures sent as control were ,spinous process ,interspinous ligaments didn’t show any fluoride deposition. Results: Out of 16 patient 15 patient had fluoride levels more than 6000mg/kg, 7 patient had values between 6,000 – 7,000 mg/kg, 5 patient had values between 7,500 – 9,000 mg/kg and 3 patients had values > 8400 mg/kg. Controls were sent as spinous processes had normal fluoride level between 500-1000 mg/kg and interspinous ligaments sent showed no fluoride levels. Out of 16 patients 9 patients had multiple level dorsal OYL both contiguous and non-contiguous, contiguous in 4 patients and non – contiguous in 5 patients.7 patients had single level dorsal OYL. Most common segment involved in OYL is T9 and D10 level in 14 patients. Sato classification 6 were Type A, 5 were Type B, 3 were Type C, 2 were Type D Conclusion: This is the largest series of ossification of dorsal yellow ligament due to fluorosis. And consideration of fluorosis as one of the important etiological cause for OYL to be kept in mind and all patients with OYL to be screened for Fluorosis and this would also help as a preventive measure for the people around the surroundings of the affected person and would help the society from a crippling disability.