Typical Hip Fractures Decline as Atypical Hip Fractures Increase

October 25, 2010 (Toronto, Canada) — Between 1996 and 2007, the number of typical hip fractures in people older than 65 years has declined considerably in the United States, whereas the number of atypical hip fractures has increased, according to a study presented here at the American Society for Bone and Mineral Research 2010 Annual Meeting.

The findings, which are particularly strong among women, come from an analysis of 2 databases — the Medical Expenditure Panel Survey, which encompassed some 372,000 respondents, and the Nationwide Inpatient Sample, which included a total of 619,044 hospitalizations for surgery for either a typical hip fracture or an atypical hip fracture.

The results were presented by John Zhong Wang, PhD, MPH, from the Intramural Research Program of the National Institute of Arthritis, Musculoskeletal and Skin Diseases at the National Institutes of Health, Bethesda, Maryland.

"I am a statistician, and not a clinician. These trends just leapt out at me when I started to examine them," Dr. Wang told Medscape Medical News. "I actually had just come from an infectious disease background so I had no prior knowledge, but after my supervisor told me about this weird phenomenon of atypical fractures with Fosamax [Merck] and breaking bones, the trend was so clear. I figured that if I saw it, I should report it."

Dr. Wang noted that during this time, the annual national estimate for typical hip fractures decreased by almost 13%, from 263,623 to 229,942. Women saw the greatest reduction in typical hip fractures. Their age-adjusted rates decreased by 31.6%, from 1020.5 to 697.4 fractures per 100,000 individuals.

Men also had a decrease in typical hip fractures, although this was less than for women. Their age-adjusted rates decreased by 20.5%, going from 424.9 to 337.6 fractures per 100,000 individuals.

However, during this time, national estimates for atypical hip fractures increased 31.2%, from 8273 to 10,853.

A closer look showed that trends in age-adjusted rates for atypical hip fractures did not change among men, but increased 20.4% among women, going from 28.4 (95% confidence interval [CI], 27.7 - 29.1) fractures per 100,000 in 1999 to 34.2 (95% CI, 33.4 - 34.9) fractures per 100,000 in 2007, or an increase of roughly 2% each year (95% CI, 1.3 - 2.8; P < .001).

At the same time, the prevalence of bisphosphonate use increased, especially among women. In 1996, 3.5% of women 65 years or older were taking bisphosphonates; in 2007, this percentage had risen to 16.6%. In contrast, only 2.3% of men were taking bisphosphonates in 2007.

In an interview with Medscape Medical News after his talk, Dr. Wang said he was simply showing a correlational analysis. "People should not take home the message that the trend for more atypical fractures is definitely one caused by bisphosphonates. However, I wouldn't be surprised if, as men start using these drugs more...they will also have more atypical fractures. But you can only say what the data tells you."

The fact that the typical hip fracture rate is going down so dramatically is probably a result of the use of antiresorptive agents, he added. "There was a 30% drop in hip fracture in women and a 20% drop in men, so people could say this was due to educational efforts at fall prevention and protection. But the fact that we see a greater drop in women means that pharmaceutical preventive treatment is probably responsible."

"This is a database study, and there are limitations with that," John Eisman, MD, director of osteoporosis and bone biology research at the Garvan Institute, Sydney, Australia, commented to Medscape Medical News. "The actual x-rays were not examined, for instance. But the data show very clearly that there has been a very definite decrease in the number of hospital discharges of women and men with hip fractures. The number of atypical fractures in women did increase, but that number was very small."

Dr. Eisman added that with almost any medical treatment, there is a potential for harm. "Some people who get treated with insulin injections for diabetes will get low blood sugar attacks, but the trade-off is that if they don't take insulin, they may actually die from their diabetes. Hip fractures are a very nasty condition where people are 2 to 3 times more likely to die over the next little while compared to other people of the same age who do not have a hip fracture. Osteoporosis and these fractures are a lethal condition, and for that reason, even if there are some potential side effects, you need to balance the 2."

Bo Abrahamsen, MD, PhD, professor of medicine, Gentofte Hospital and University of Southern Denmark, Hellerup, Denmark, told Medscape Medical News that the study results tie in with what is currently known.

"This is useful information. The atypical fractures only go up by 1 for each 100 typical hip fractures that go down. We don't know what is causing this exactly, because this paper cannot tell us, but just comparing these numbers is very reassuring and ties in well with what we know from other sources. I think that is informative," he said.

Dr. Wang, Dr. Eisman, and Dr. Abrahamsen have disclosed no relevant financial relationships.

American Society for Bone and Mineral Research 2010 Annual Meeting: Abstract 1029. Presented October 16, 2010.