Strontium ranelate: a physiological approach for an improved bone quality.

In vitro studies have suggested that strontium ranelate enhances osteoblastic cell replication leading to an increase in bone-forming activity. Simultaneously, strontium ranelate dose dependently decreases osteoclastic activity. In vivo studies indicate that strontium ranelate decreases bone resorption and maintains a high bone formation and prevents bone loss. This positive uncoupling between bone formation and bone resorption results in bone gain and improvement in bone geometry and microarchitecture in growing animals. In intact female rats, a 2-year period of exposure to strontium ranelate significantly increased bone mechanical properties of vertebrae and midshaft femur. All the determinants of bone strength were positively influenced by the treatment like bone mass, dimension, microarchitecture, and intrinsic bone tissue quality. The increment in bone mechanical properties was characterized by an increase in maximal load but also by a dramatic improvement in energy to failure, which was essentially due to an increment in plastic energy. Such modifications observed with strontium ranelate treatment are in good agreement with the improvement in intrinsic bone quality. These results strongly suggest that new bone formed following strontium ranelate treatment is able to withstand greater deformation before fracture. Furthermore, treatment with strontium ranelate prevents the deleterious effect of ovariectomy on bone strength. In this model, a 1-year period of exposure to strontium ranelate significantly prevents alteration of bone mechanical properties of vertebrae in association with a partial preservation of the trabecular microarchitecture: a dose-dependent effect on the bone volume/trabecular volume ratio and trabecular number and thickness.