Number and severity of prevalent vertebral fractures and the risk of subsequent vertebral fractures in Japanese women with osteoporosis: results from the minodronate trial

The aim was to evaluate the risk of new vertebral fractures with the increasing number and severity of prevalent vertebral fractures in women who received placebo or minodronate in a post hoc analysis of a 2-year randomized, double-blind, placebo-controlled study. The subjects were women aged 55-80 years old with 1-5 fragility fractures between the T4 and L4 vertebrae and bone mineral density < 80 % of the young adult mean. A total of 704 subjects were randomized to take minodronate 1 mg (n = 359) or placebo (n = 345) once a day for 24 months. In the placebo group, the risk of incident vertebral fractures during the 2-year observational period was significantly related to the number and severity of prevalent vertebral fractures at baseline. The number of prevalent vertebral fractures was an independent risk factor for incident vertebral fracture in multivariate analysis. The relative risk reductions of vertebral fractures by minodronate treatment were 45.2, 61.1, and 64.2 % for patients with 1, 2, and a parts per thousand yen3 prevalent vertebral fractures, respectively, and 87.8, 64.6, and 50.1 % for patients with mild, moderate, and severe prevalent vertebral fractures, respectively. In conclusion, the number of prevalent vertebral fractures is an independent risk factor for incident vertebral fracture and minodronate reduces the fracture risk even in patients at a higher risk for fracture.