Endocrine Abstracts

Introduction: Bisphosphonates are the most commonly used drugs for the treatment of osteoporosis and have been shown to improve bone mineral density and reduce fractures. However, approximately a decade ago, atypical femoral shaft fractures were found to be a rare complication of bisphosphonate treatment. Atypical Femoral Fractures (AFF) represent fractures located between the lesser trochanter and the supracondylar flare of a femur. An increasing pool of evidence supports their association with the prolonged use of bisphosphonates, even though a direct correlation has not been proven yet. In this report, we describe a patient who developed atypical femoral fractures after prolonged use of bisphosphonates.

Case: A 42-year-old man was referred to our out-patient clinic after operation for bilateral femoral fractures by orthopedists. The patient had the history of mild trauma. Her medical case history revealed that, for the past 6 years, he had received 70 mg/week alendronate as treatment for osteoporosis. Plain radiographs showed a transverse fracture in the bilateral femur, and cortical thickening was observed at the fracture site. His bone mineral densities (BMD) at the baseline dual-energy X-ray absorptiometry (DEXA) scan were as follows; femoral neck: 0.76 g/cm² (T score −1.2), femoral total: 0.79 g/cm² (T Score −1.6), and lumbar total: 0.70 g/cm²(T Score −3.7). Blood tests indicated that his serum calcium, phosphate, and alkaline phosphatase levels were in the normal ranges. Any reason for secondary osteoporosis was not determined. The patient was diagnosed as bilateral atypical femoral fractures. The patient discontinued his alendronate regimen. The patient was treated with teriparatide 30 μg/day for osteoporosis for 18 months. After this treatment, lumbar total T-score was reduced to −2.9 (0.77 g/cm²).

Conclusion: Bisphosphonates are one of the most widely prescribed drugs for the treatment osteoporosis and the reduction of fracture risk. In this report, we presented a patient with atypical fractures associated with long-term bisphosphonate treatment. The correlation between the long-term bisphosphonate use and atypical fractures has not been conclusively established. However, the drug holiday is suggested to reduce the risk of atypical fracture after prolonged bisphosphonates use. This case confirmed that teriparatide had a rapid bone anabolic effect on unhealed atypical fractures associated with chronic bisphosphonate use.