Asymptomatic vertebral fractures are common in the elderly, however their impact on clinical fracture risk has not been fully elucidated.
Data from 4442 women and 1755 men aged 50+ participating in the Canadian Multicentre Osteoporosis Study were analysed. Lateral thoracic and lumbar spine radiographs (T4-L4) at baseline were assessed using the Genant method (Grade 1 defined as vertebral height reduction 20 - 25%, Grade 2 26 - 40%, Grade 3 >40%).
At baseline, 13.8% of women and 14.5% of men had at least one asymptomatic vertebral fracture. For women, 6.6% had maximum Genant grade 1 fracture, 4.8% grade 2 and 2.4% grade 3. For men, 8.6% had maximum grade 1, 4.3% grade 2, and 1.5% grade 3. Incidence of clinical fracture was 24.9 per 1000 person years (95% CI 24.3-25.6) for women and 14.8 per 1000 person years (95% CI 13.9-15.8) for men.
Number of baseline asymptomatic vertebral fractures increased risk of incident clinical fracture for men and women after adjusting for age, body mass index, bone mineral density, prior clinical fracture and falls. The adjusted hazard of clinical fracture for each additional baseline vertebral fracture was 1.12 (95% CI 1.08-1.18) for women and 1.15 (95% CI 1.03-1.28) for men.
Genant grade 1 vertebral fractures did not increase risk of subsequent fracture for either sex after adjustment for other risk factors. However, compared to women with no vertebral fracture, higher Genant grade was associated with increased fracture risk [1.39 (95% CI 1.10-1.76) for grade 2, and 2.40 (95% CI 1.83-3.17) for grade 3]. For men, fracture risk was similar for Genant grade 2 [1.86 (95% CI 1.20-2.87)]. There were insufficient grade 3 fractures in men for analysis.
This study demonstrates that asymptomatic vertebral fracture number and severity (Genant grade>2) are associated with increased fracture risk, highlighting their clinical importance.