Evidence of Spinal Fracture Spots Women Needing Osteoporosis Treatment

By John Gever
PITTSBURGH, Dec. 18 -- A simple X-ray, or dual energy X-ray absorptiometry, may give an older woman a 15-year window to avoid the dreaded "dowager's hump," researchers here said.Evidence of a vertebral fracture in older women, even in the face of normal bone-mineral density, is the key to triggering the need for therapy to avoid more spine fractures later, Jane A. Cauley, Dr.P.H., of the University of Pittsburgh, and colleagues reported in the Dec. 19 issue of the Journal of the American Medical Association.
Women at a mean age of 68.8 with a documented previous vertebral fracture had a 41.4% rate of new vertebral fractures during the next 15 years, the investigators found in the prospective Study of Osteoporotic Fractures. This compared with a 14.2% rate among women without such evidence.
Pointing out that only about one-third of vertebral fractures are clinically identified, "case-finding strategies should be developed to identify women with a high likelihood of having a prevalent vertebral fracture," said the Pittsburgh group.
One-quarter of women with documented fractures and normal bone-mineral density had new fractures, compared with 9% of those with normal bone-mineral density and no prevalent fractures at baseline.
"Our results support the recommendation that older women with a prevalent vertebral fracture should be treated for osteoporosis irrespective of bone-mineral density," Dr. Cauley's group wrote. "Treatment of women with prevalent asymptomatic vertebral fractures with bisphosphonates and selective estrogen receptor modulators has been shown to decrease fracture incidence."
The finding may help women avoid "dowager's hump" by identifying those at high risk of vertebral fractures and beginning anti-osteoporosis treatment early, Dr. Cauley and colleagues said.
"Women don't have to end up with dowager's hump, the hallmark of osteoporosis," they said. "A simple and noninvasive bone density test can help identify those at risk."
The Pittsburgh group said it is developing a risk model to help physicians better identify women at increased risk for silent spine fracture and who may benefit from anti-osteoporosis treatment.
"Use of dual energy X-ray absorptiometry to measure vertebral morphometry may be more cost-effective to improve fracture risk stratification and identify women with prevalent vertebral fractures who have a high absolute risk of fracture and may be more likely to benefit from pharmacological therapy," the investigators wrote.
The findings emerged from data on 2,680 women who had baseline bone-mineral density measurements and spinal X-rays as well as clinic visits, with spinal x-rays a mean of 14.9 years later.
Low bone-mineral density at baseline also strongly predicted new vertebral fractures.
Dr. Cauley's group found a multivariable adjusted 111% increase (OR: 2.11, 95% CI: 1.84 to 2.43) in the probability of a new fracture during the follow-up period for each standard deviation decrease in lumbar spine bone-mineral density. Smaller but still significant increases in fracture probability were seen with low bone-mineral density at other locations including the calcaneus, distal radius, total hip and femoral neck.
However, X-ray evidence of previous spinal fracture at baseline magnified the risk attached to low bone-mineral density.
Among those with total hip bone-mineral density T-scores more than 2.5 points below normal and a prevalent vertebral fracture at baseline, 56% sustained at least one new fracture during follow-up. Those with low bone-mineral density and no prevalent fractures at baseline had only a 28% incidence of new fractures.
A similar difference was seen in women with baseline hip bone-mineral density of -2.5 to -1.0. About 16% of those without prevalent vertebral fractures at baseline versus 42% of those with previous fractures were found to have sustained new fractures at the follow-up exam.
The researchers noted that most fractures occur in women who do not have osteoporosis according to bone-mineral density scores.
An algorithm developed from the European Prospective Osteoporosis Study included age, height loss, weight, and a history of fracture and identified those individuals who were more likely to have a documented vertebral fracture by X-ray with moderate accuracy.
The authors noted several limitations of the study. "We studied the highest risk demographic group for vertebral fracture (i.e., older white women) but our results may not be generalizable to women of other ethnicities or to men."
"Although a high rate of survivors participated in the clinic visit, the women who returned for the eighth clinic examination were healthier at baseline than those who did not," they wrote. "Thus, we may have underestimated the absolute risk of vertebral fractures."
The study was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Institute on Aging.
Dr. Cauley reported financial relationships with Merck, Eli Lilly, Pfizer, and Novartis. Other co-authors reported relationships with Amgen, GlaxoSmithKline, Procter & Gamble, Roche, Wyeth, Zelos, and Aventis.

Primary source: JAMASource reference:Cauley J, et al "Long-term risk of incident vertebral fractures" JAMA 2007; 298: 2761-67.