Friday, July 1, 2011

FDA Warning: Atypical Femur Fractures Seen In Fosamax Recipients

As a result of ongoing investigations regarding Fosamax and the use of bisphosphonates (BPs) to treat osteoporosis, the FDA has announced that the risk of atypical fractures of the thigh will be added to the Warnings and Precautions section of all labels of BP drugs. Specifically, these atypical fractures are known as subtrochanteric and diaphyseal femur fractures. Recent studies strongly suggest there is a causal link between people who take BPs and the increased risk of these atypical fractures. Furthermore, not only are people who take BPs put in greater risk of fracture, these particular types of fracture are especially more dangerous than the more common femur fractures. Additionally, the use of BPs results in longer and more complicated healing of the bone.

What is a subtrochanteric and diaphyseal femur fracture?

Aytpical subtrochanteric femur fracture is a fracture occurring on the shaft of the femur immediately below the lesser trochanter. That is, right below the hip joint. These fractures are not common, rather they account for only 7% to 10% of all “hip/femoral diaphyseal fractures.”Furthermore, given the unique nature of this fracture, special implants are required in order for the fracture to heal, and they are also more susceptible to malunion or nonunion. Additionally, those affected are liable to suffer long term effects. One study indicated that after 2 years, about 50% of persons who suffered a subtrochanteric fracture did not recuperate their pre-fracture walking abilities and faced difficulties performing routine activities. A total of 71% could not live in the same conditions as they lived previously. 

A diaphyseal fracture on the other hand, is a fracture that occurs on the main or midsection of the femur. These of course are one of the more common fractures. What is significant however is that these fractures are more typically associated with high trauma incidents, whereas people taking BPs have incurred these fractures as a result of little to no trauma.

In general there are also other features seen in people taking BPs that make these particular subtrochanteric and diaphyseal fractures atypical. First, the fractures are transverse, that is a straight break perpendicular to the shaft of the femur, or it is a straight angled break.  Second, the breaks are clean, in that the bones are not crushed or splintered as you would expect from high trauma breaks. Third, incomplete fractures tend to occur on the lateral side of the femur. Finally, more minor features include fractures in patients whose bones show evidence of an increase in the thickness of the femurs wall, delayed healing, and patients also report that weeks prior to the fracture they experienced symptoms such as dullness and aching in their groin or thigh.  

What’s the cause?

The evidence of BP causing unusual femur fractures, has certainly convinced the FDA to prompt these new warning label requirements. Studies are showing that BPs do increase bone density and strength, that is after all exactly what they prescribed to do. That increased strength and density however is achieved by reducing bone turnover. This means essentially instead of “out with the old, in with the new,” as is the case for normal bone “remodeling,” it is more like, “keeping the old, and piling on the new.” The problem however is that bones naturally incur cracks and micro-damage, which is in turn naturally repaired by the body through the process of remodeling. Absent remodeling which is suppressed by the BPs, micro-damage begins to accumulate. Over time, the end result is a thicker, much denser bone, albeit one that is less structurally sound, thus the increased risk of these atypical fractures.

In the short run, it may be that using BPs to combat osteoporosis is an effective treatment. However, for those patients unaware of the risks associated with BPs, like those who have been affected by Fosamax, evidence indicates that whether a person should undergo long term treatment requires a careful assessment of the risks versus its benefits. For this reason the FDA specifically recommends that health care professionals reevaluate a patients need to continue BP therapy, especially for those who have been treated with BPs over five years. c

Chris Hellums can be contacted at


[1] US Food and Drug Admin. FDA Drug Safety Commc’n: Safety Update for Osteoporosis Drugs, Bisphosphonates, and Atypical Fractures (2010).
[2] Shane E, Burr D. Ebeling PR, et al. Atypical Subtrochanteric and Diaphyseal Femoral Fractures: Report of a Task Force of the American Society for Bone and Mineral Research. 25 J. Bone Miner. Res. 2267 (2010).

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