Published: March 2013

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Osteoporosis Treatments and Atypical Femur Fracture

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Prescriber Update 34(1):5-6
March 2013

In November 2009, Medsafe highlighted an association between alendronate and low-energy femoral shaft fracture¹.

Since then, similar cases have been published involving other bisphosphonates as well as denosumab (Prolia). Denosumab is a new treatment for osteoporosis that is approved but not currently available in New Zealand. Information on this risk is included in the data sheets for Fosamax (alendronate), Zometa (zolendronate) and Pamisol (pamidronate).

To date there has been no confirmed association between strontium, teriparatide, raloxifene or hormone replacement therapy and atypical fractures of the femur.

Features associated with subtrochanteric and diaphyseal fractures include²:

• minimal to no trauma
• transverse fracture line on radiography
• prodromal pain
• unilateral cortical beaking and bilateral thickened diaphyseal cortices on radiography
• poor fracture healing.

The Centre for Adverse Reactions Monitoring (CARM) has received two reports of fractures describing some of the features outlined above. In both cases, the patient was taking alendronate.

Atypical subtrochanteric fractures are rare, less than 0.1% of total fractures in a New Zealand study³. For a population of 10,000 patients at high risk of fracture, bisphosphonate treatment might be expected to prevent 108 hip fractures (and around 750 other fractures) per year and result in three subtrochanteric fractures². Therefore, the benefit risk ratio for bisphosphonate treatment remains favourable.

In patients with atypical femoral fractures, bisphosphonate treatment should be considered as a possible cause. Interruption of bisphosphonate therapy may be necessary for fracture healing. Re-treatment should be considered if bone density again begins to fall and after a discussion of the benefits and risks with the patient.

References

1. Medsafe. 2009. Alendronate — risk of low-energy femoral shaft fracture. Prescriber Update 30(4): 25.
2. Rizzoli R, Akesson K, Bouxsein M, et al. 2011. Subtrochanteric fractures after long-term treatment with bisphosphonates: a European Society on Clinical and Economic Aspects of Osteoporosis and Osteoarthritis, and International Osteoporosis Foundation Working Group Report. Osteoporosis International 22(2): 373-390.
3. Warren C, Gilchrist N, Coates M, et al. 2012. Atypical subtrochanteric fractures, bisphosphonates, blinded radiological review. ANZ Journal of Surgery 82: 908-912.