Osteoporosis: radiographic detection of fluoride-induced extra-axial bone formation.

New bone formation in the peripheral skeleton was detected radiographically in 67% (22/33) of patients studied for new periarticular pain among 72 patients with osteoporosis being treated with fluoride, 66-88 mg/d, for 6 or more months. Changes included periosteal and endosteal new bone formation as well as trabecular thickening and were localized in areas of high mechanical stress. Sufficient mineral deposition for radiographic detection required 6 or more months of fluoride treatment. Radiologists must differentiate fluoride-induced new bone formation from other-processes, such as fractures and tumor, and elicit information on fluoride intake in suspicious cases.