Trends in incidence of subtrochanteric fragility fractures and bisphosphonate use among the US elderly, 1996-2007

Abstract

Increasing numbers of atypical hip fractures have been reported among patients with bisphosphonate use. However, the nature and extent of the problem are unknown despite recent investigations. To analyze national trends in hip fractures and medication use in the elderly US population, we respectively used the Nationwide Inpatient Sample (NIS) and the Medical Expenditure Panel Survey (MEPS) from 1996 to 2007. In NIS, subtrochanteric fragility fractures were compared with typical hip fractures in femoral neck and intertrochanteric regions. Between 1996 and 2007, age-adjusted rates for typical hip fractures decreased by 31.6% among women (from 1020.5 to 697.4 per 100,000 population) and 20.5% among men (from 424.9 to 337.6 per 100,000 population). In contrast, overall trends in age-adjusted rates for subtrochanteric fragility fractures remained unchanged among men (p = .34) but increased 20.4% among women from 28.4 (95% confidence interval [CI] 27.7-29.1) in 1999 to 34.2 (95% CI 33.4-34.9) per 100,000 population in 2007. The annual percentage increase was 2.1% (95% CI 1.3-2.8, p < .001) based on joinpoint regression analysis. In MEPS, bisphosphonate use increased predominantly in women (from 3.5% in 1996 to 16.6% in 2007) compared with men (2.3% in 2007). In the context of declining typical hip fractures among the US elderly, we observed small but significant increases in the incidence of subtrochanteric fragility fractures from 1999 among postmenopausal women. Using age-adjusted rates, we estimated that for every 100 or so reduction in typical femoral neck or intertrochanteric fractures, there was an increase of one subtrochanteric fragility fracture.

Fig. 1

National estimate of subtrochanteric and typical hip fractures in patients aged 65 and older. Data are based on Nationwide Inpatient Samples. Error bars indicate standard deviation.

Fig. 2

Age-adjusted rates of subtrochanteric and typical hip fractures in elderly patients aged 65 and older. Data are based on Nationwide Inpatient Samples. Error bars indicate 95% confidence interval. Two separate regression lines were drawn through joinpoints based on the best model fit.

Fig. 3

Age-standardized proportion of subtrochanteric hip fractures among all hip fractures and prevalence of bisphosphonate use. Data are based on Nationwide Inpatient Samples for proportions and Medical Expenditure Panel Survey for the medication use. Error bars indicate 95% confidence interval. Percentage changes were normalized in women for the temporal correlation between the bisphosphonate use and subtrochanteric hip fractures.