[Spontaneous fissures and fractures of the legs in patients with osteoporosis treated with sodium fluoride].

Thirteen cases of spontaneous fissure or fracture of the lower limbs observed in 8 patients under treatment with sodium fluoride are reported; 7 of these patients were being treated for osteoporosis. The fissures occurred after 20 months of treatment on average and were revealed by pain in the metaphysis with early high radionuclide uptake. Three to 4 weeks later, X-ray films showed a linear bone condensation area, involving in most cases, the tibial metaphysis, the femoral neck and the calcaneum. The prognosis was usually favourable, but 2 patients required surgery for fissure of the femoral neck with rupture of the cortex. Fluor seems to be responsible for the fissures which cannot be avoided by calcium and/or vitamin D intake. The main pathogenic hypotheses are excessive bone resorption, large amounts of poorly mineralized osteoid tissue and architectural abnormalities of the trabeculae. When such fissures occur, fluoride therapy must be discontinued and the limb put at rest, but since this side-effect is rare and usually benign the principle of a treatment that is beneficial in many cases of osteoporosis need not be revised.