Atypical Femur Fractures Explained

According to Girgis et al., Whilst bisphosphonates are an established modality in the treatment of osteoporosis, there have been increasing concerns regarding the risk of an unusual form of femur fracture amongst patients receiving bisphosphonates for prolonged periods.These fractures referred to as ‘atypical’, have been characterized by a number of clinical and radiographic features that distinguish them from ‘typical’ osteoporotic fractures.

These types of fractures occur while taking a bisphosphonate or after one has finished it; and the fracture happens without any injury where the bone breaks while standing, in the upper thigh, and then the patient falls.

Image of atypical femur fracture



Bisphosphonates are highly effective in the treatment of osteoporosis, however there remains a population of patients who sustain these types of femur fractures due to prolonged use of bisphosphonates of approximately three to five years.

What is an atypical femur fracture (AFF) and how does it differ from a hip fracture?

This type of fracture occurs in one of the bodies’ strongest bones, the femoral shaft, which is located in the thigh. These fractures occur just below the femoral neck—location of most hip fractures—and some characteristics are bone thickening, prodromal pain and the location, which is in the top 2/3 of the femur bone.

What causes a femur fracture?

Femur fractures can occur from a major trauma, like an automobile accident, or in this case, from a minor movement from prolonged use of bisphosphonates for more than 3 years.

What are the symptoms of an atypical fractured femur?

Some common symptoms are: pain in the femur for 1-2 months, stress fracture with little trauma, presenting in the top 2/3 of the femur, groin pain and long term use of bisphosphonates (Fosamax®, Actonel®, Atelvia®, Reclast® Aredia® and Boniva®).

How is an AFF diagnosed?

Typical x-rays don’t normally show a stress fracture of the femur, so an MRI or CT scan needs to be performed if the fracture doesn’t show up on an x-ray. The fracture must be from a low energy trauma where the bone breaks before a fall, in most cases. If a nuclear medicine test shows this type of fracture, then you will have a diagnosis of AFF.

How is it treated?

If a fracture of this kind happens to a patient taking a bisphosphonate, a surgeon will do a procedure where rods and screws are used to stabilize the bone that’s fractured. These fractures can be hard to heal and in some cases an exchange nailing procedure must be done. In many cases, when one femur fractures it is highly likely that the other femur will fracture as well, so the doctor has to monitor this.

How long does this type of fracture take to heal?

Each patient is different when it comes to healing, so it may take upwards of a year to recover. If there is a problem with healing your doctor may suggest using Forteo, a genetically engineered form of parathyroid hormone, to assist in healing and laying down new bone. Forteo is a daily subcutaneous injection, normally used for a limit of two years, but in this case it can be used for a lesser amount of time or until the femur heals.

If you suspect that you have a fracture of this kind, see your doctor or a specialist as soon as possible. You will need to follow through on testing to reach a diagnosis, and be sure to tell your doctor if you have pain in both upper thighs and or groin area.


Black, et al ASBMR (2009) Rare Atypical Subtrochanteric Fractures. Accessed 4-10-15 from

Pam is a patient educator and digital health writer who has worked for Remedy Health Media on their osteoporosis web site since 2008. Pam is also a group leader and moderator with the National Osteoporosis Foundation Inspire online community.

Pam Flores
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Pam Flores

Pam wrote for HealthCentral as a patient expert for Osteoporosis.