Do Bisphosphonates Cause Atypical Femoral Fractures?

Several uncontrolled case series have described atypical subtrochanteric or femoral shaft fractures after long-term bisphosphonate therapy; the presumed mechanism is oversuppression of bone turnover (JW Gen Med Dec 15 2009). However, those reports do not establish causality. Now, researchers have examined whether an excess of such fractures occurred in three previously published randomized trials of bisphosphonate therapy for osteoporosis. The analysis was supported by the makers of alendronate and zoledronic acid.

The trials included about 7800 bisphosphonate recipients and 7500 placebo recipients: 3900 patients received zoledronic acid for 3 years, 3200 patients received alendronate for 4 years, and 660 patients received alendronate for 10…