Bisphosphonate
use may have a paradoxical effect of adversely affecting bone
architecture, thereby raising risk for atypical femoral fractures. In
this retrospective Swiss case-control study, researchers explored this
relation using data from a single trauma center that captured 95% of all
femoral fractures in Geneva. Between 1999 and 2009, 477 patients with
subtrochanteric or femoral shaft fractures were identified; 39 had
atypical fractures (defined as a transverse or short oblique fracture
rather than a typical oblique intertrochanteric or shaft fracture).
Of those 39 patients with atypical fractures, 82.1% were using
bisphosphonates, compared with 6.4% of those with classic femoral
fractures (odds ratio, 67) and 11.5% in a control group without fracture
(OR, 35). Adjustment for age, sex, and use of vitamin D,
corticosteroids, and proton-pump inhibitors did not change the odds
ratio for atypical versus classic fracture. Risk also rose with longer
duration of bisphosphonate use; for example, the odds ratio for atypical
fracture compared to classic fracture was 117 with 5 to 9 years of use
and 176 for longer than 9 years.
Comment: Bisphosphonate use appears to confer a large
relative, albeit very small absolute, risk for atypical femoral
fracture, particularly when used for 5 years or more. Concern about
atypical fractures and other adverse effects has prompted some experts
to recommend discontinuation of bisphosphonates in low-risk patients
after several years, but this decision requires a detailed discussion of
the risks and benefits –– particularly about balancing an elevated risk
for vertebral fractures (after stopping the drug) against the small
absolute risk for atypical femoral fractures (if the drug is continued).
— Thomas L. Schwenk, MD
Published in Journal Watch General Medicine June 7, 2012
