Incidence of vertebral fractures (VFs) over 4 years. Thirty VFs of 298 patients were observed for a total of 852 person-years over the study period. (A) The incidence of VFs was 4.7% at 2 years and 13.6% at 4 years. (B) This resulted in a total of 30 fractures, most commonly at vertebra L1: 24 VFs were Genant grade 1 and 6 VFs were grade 2. Error bars represent the mean (SD).