Disc space narrowing as a new risk factor for vertebral fracture: the OFELY study.

Objective: In a previous cross-sectional analysis, we found a positive association between disc space narrowing (DSN) and vertebral fracture. The aim of the present study was to analyze prospectively the risk of vertebral and nonvertebral fractures in women with spine osteoarthritis (OA).

Methods: Using radiographs, spine OA was evaluated in 634 postmenopausal women from the OFELY (Os des Femmes de Lyon) cohort (mean+/-SD age 61.2+/-9 years). Prevalence and severity of spine OA were assessed by scoring osteophytes and DSN. Incidental clinical fractures were prospectively registered during annual followup, and vertebral fractures were evaluated by radiography every 4 years.

Results: During an 11-year followup, fractures occurred in 121 women, including 42 with vertebral fractures. No association was found between osteophytes and the risk of fracture. In contrast, DSN was associated with an increased risk of vertebral fractures but not of nonvertebral fractures. After adjusting for confounding variables, the presence of DSN was associated with a marked increased risk of vertebral fractures, with an odds ratio of 6.59 (95% confidence interval 1.36-31.9). In addition, 95% of incident vertebral fractures were located above the disc with the most severe narrowing.

Conclusion: This longitudinal study shows that, despite a higher bone mineral density (BMD), women with spine OA do not have a reduced risk of fracture and that DSN is significantly associated with vertebral fracture risk. The location of DSN and of incident vertebral fractures suggests that disc degeneration impairs the biomechanics of the above spine, which leads to the increased risk of vertebral fractures, independent of BMD. We suggest that DSN is a newly identified risk factor for vertebral fracture that should be taken into consideration when assessing vertebral fracture risk in postmenopausal women.