Bisphosphonate therapy appears to be associated with an increased risk of atypical fractures of the femur, and may be driven by the duration of treatment, according to new research.

Of 477 patients hospitalized at one center, 39 had atypical fractures and 438 had common fractures. Among those with atypical fractures, 82.1% had been taking bisphosphonates compared with just 6.4% of those with common fractures, Raphael P.H. Meier, MD, from University Hospitals of Geneva, and colleagues reported online in the Archives of Internal Medicine.

They also noted that the atypical-fracture group had a longer treatment period on bisphosphonates — including alendronate (Fosamax), risedronate (Actonel), pamidronate (Aredia), and ibandronate (Boniva) — than the classic-fracture group, at a mean of 5.1 years versus 3.3 years (P=0.02).

Nonetheless, compared with a 200-patient fracture-free control group, use of bisphosphonates was associated with a 47% reduction in the risk of common fractures (OR 0.5, 95% CI 0.3 to 0.9), making the absolute risk:benefit ratio of bisphosphonates a positive one, they added.

The current evidence on bisphosphonate use and atypical fractures is conflicting. A recent meta-analysis of randomized trials found no association. But a registry-based study suggested that the risk of atypical fracture was more than doubled when bisphosphonates were taken […]