Spinal osteoarthritis is a risk of vertebral fractures in postmenopausal women.

Recent studies have revealed that despite high bone mineral density (BMD), osteoarthritis (OA) is a risk factor for osteoporotic fractures. However, the relationship between spinal OA and vertebral fractures has not yet been fully investigated. This longitudinal analysis used a subset of ongoing cohort study consist with Japanese postmenopausal women. The prevalence of spinal OA was determined using Kellgren-Lawrence grading method. The incidence of vertebral fractures were determined by semiquantitative analysis of spinal X-ray films. The relationship between the presence of spinal OA and incidence of vertebral fractures was evaluated using the Cox regression analysis. In total, 1480 women were followed up for 8.1 ± 6.4 years. Among them, 923 were diagnosed with spinal OA, and incident vertebral fractures were observed in 473 participants. After adjusting for confounding variables, the spinal OA (≥ grade 2) was a significant predictor of incident vertebral fractures (hazard ratio, 1.52; 95% confidence interval: 1.19-1.93, p = 0.001). Using ROC analysis, the thresholds of lumbar BMD for incident vertebral fractures were 0.952 g/cm2 for patients with spinal OA and 0.753 g/cm2 for patients without spinal OA. The presence of spinal OA is a risk factor for incident vertebral fractures despite high lumbar BMD.