What's the Diagnosis - Case 39

History 60 year old woman with right hip pain and limp.

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Findings Both cases show subtle areas of periosteal reaction, cortical thickening, and/or endosteal reaction on the radiographs and on the CT images of the second case. On the flow and pool studies, no increased radiotracer uptake is identified. However, on the delayed images a focal, round to ovoid area of increased radiotracer uptake is seen within the proximal femora corresponding to the areas of periosteal/endosteal reaction.

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Diagnosis: Bisphosphonate Associated Subtrochanteric Stress Fractures Bisphosphonate treatment has become a mainstay in the treatment of osteoporosis.

More recently PTH analogs have also gained increasing favor. Bisphosphonates work by inhibiting osteoclast activity and inducing apoptosis so that bone is not resorbed. Although extremely useful in patients with osteoporosis to help prevent fractures, adverse reactions do occur. The most well known is avascular necrosis of the jaw which is associated with high dose intravenous treatment in the cancer patient.

In the orthopedic community, bisphosphonate treament has been associated withsubtrochanteric stress fractures and frank, complete fractures. It is postulated that microfractures occur and because of the decreased bone turnover from the bisphosphonate treatment, healing can not occur and these atypical fractures subsequently propagate. There occurrence is however markedly decreased compared to hip fractures and the benefit of treatment is thought to outweigh the risks. That being said, these fractures are difficult to treat and can require subsequent surgery.

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Resources

• Shane E (May 2010). “Evolving data about subtrochanteric fractures and bisphosphonates”. N. Engl. J. Med. 362 (19): 1825–7. May 2010

• Lenart BA, Lorich DG, Lane JM. Atypical Fractures of the Femoral Diaphysis in Postmenopausal Women Taking Alendronate. N Engl J Med 358:1304, March 20, 2008 Correspondence.

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