Mild prevalent and incident vertebral fractures are risk factors for new fractures

This prospective four-year study indicates that post-menopausal osteoporotic women with mild prevalent and incident vertebral fractures have an increased risk of incident fractures.

Mild vertebral fractures are under diagnosed as there is disagreement about their clinical significance. Our aim was to assess the risk of subsequent fractures induced by both prevalent and incident mild vertebral fractures in osteoporotic post-menopausal women.

Three thousand three hundred and fifty-eight patients, aged 74 ± 6 years, with post-menopausal osteoporosis included in the placebo groups of two clinical trials of strontium ranelate were followed for 4 years. A Cox regression model adjusted on age, body mass index and bone mineral density was used to calculate the relative risk (RR) of fracture in subjects with only mild fractures as compared to patients without fracture, and to patients with at least one grade ≥ 2 fracture. These calculations were made for prevalent and then incident fractures.

The RR of vertebral fracture in 4 years was 1.8 (1.3–2.4) p < 0.001, and 2.7 (2.3–3.3) p < 0.001 for patients having only mild vertebral fractures and at least one grade ≥ 2 fracture at baseline respectively. The RR of vertebral fracture in the 3rd and 4th years of follow-up was 1.7 (1.1–2.6) p = 0.01, and 1.9 (1.3–2.6) p < 0.001 for patients having during the first 2 years incident mild fractures only, and for patients having at least one grade ≥ 2 incident fracture respectively. The RR of non-vertebral fracture in 4 years was 1.3 (0.9–1.9) p = 0.15 and 1.7 (1.4–2.1) p < 0.001 for patients having only mild or at least one grade ≥ 2 vertebral fracture at baseline respectively. For patients aged more than 70 years, these RR were 1.45 (0.99–2.11) (p = 0.06), and 1.72 (1.36–2.18) p < 0.001 respectively. The RR of non-vertebral fracture in the 3rd and 4th years was 1.68 (1.36–2.09) p < 0.001 for patients having at least one grade ≥ 2 incident fracture during the 2 first years of follow-up.

Mild vertebral fractures are a risk factor for subsequent vertebral and non-vertebral fracture in postmenopausal women with osteoporosis; 1 out of 4 patients with an incident mild vertebral fracture in 2 years will fracture again within the 2 next years.