Definition: An atypical femur fracture is an unusual break in the shaft of the thigh bone that happens with little or no trauma. Bisphosphonate labels such as Fosamax and Reclast list it as a warning. It can affect both legs and often follows weeks to months of dull, aching thigh pain.
The Fosamax label (section 5.5) says low-trauma fractures of the thigh bone shaft have been reported, sometimes on both sides. Many people had dull, aching thigh pain for weeks to months before the break. The label says new thigh or groin pain should be checked for a fracture, and that pausing the bisphosphonate is considered.
The Reclast label lists unusual thigh fractures among its warnings too. The Prolia label says the long-term effect of the drug on bone is not known and may contribute to atypical fractures.
The warning sign is slow and easy to dismiss. A note in your log when thigh or groin pain starts, next to your dose history, gives your prescriber the timeline the label asks them to check. The start date matters too: the Fosamax label says the best length of use has not been set, so total time on the drug is part of the conversation. This is a different warning from osteonecrosis of the jaw.
Read more on Dose Track: Fosamax side effects · Reclast side effects · Prolia side effects