Natural history and risk factors for adjacent vertebral fractures in the fracture intervention trial.
STUDY DESIGN
Retrospective analysis of prospectively collected follow-up data for 2.9 years.


OBJECTIVE
To determine the natural history of subsequent morphometric fracture rates at adjacent levels (one level above or below a previous known baseline fracture) in a large patient database.


SUMMARY OF BACKGROUND DATA
The long-term risk and risk factors for adjacent-level vertebral fractures in patients with osteoporosis are unknown.


METHODS
The fracture intervention trial is a large randomized, placebo-controlled trial of alendronate treatment for osteoporosis. Data from both bisphosphonate-treated and bisphosphonate-naive patients (N = 1950, vertebral fracture arm) was analyzed to detect incident morphometric fracture rates.


RESULTS
During a mean follow-up of 2.9 years, 3.4% of patients in the alendronate group and 7.4% in the placebo group experienced adjacent-level vertebral fractures. The annual rate of adjacent-level vertebral fractures was 1.2% in the alendronate group, and 2.5% in the placebo group (overall, 1.8% per year in both groups combined). As expected, the thoracolumbar region (defined as T11, T12, and L1) seemed to be the most prone to new adjacent-level fractures. Among females with baseline prevalent fractures at the thoracolumbar junction, who subsequently experienced at least one new fracture anywhere along the spine (N = 124), 40.3% had a new adjacent-level fracture in this region. Older age at randomization, lower bone mineral density, inactivity, and placebo therapy were significantly associated with the development of adjacent-level fractures in univariate analysis (P ≤ 0.05). Multivariate analysis indicated decreased odds of adjacent-level fractures with bisphosphonate therapy and higher bone mineral density, and increased odds with older age at randomization (P ≤ 0.05).


CONCLUSION
New vertebral fractures adjacent to prevalent fractures occurred relatively infrequently in this treatment trial of alendronate in females with osteoporosis, and were more common with older age at randomization, lower bone mineral density and placebo treatment.