Atypical Femoral Fractures during Prolonged Use of Bisphosphonates: Short-Term Responses to Strontium Ranelate and Teriparatide

CONTEXT: Atypical femoral fractures have rarely been reported in women taking bisphosphonates, but this is still a controversial issue. Data are derived mainly from observation studies because a post hoc analysis from a randomized clinical trial did not find any such association. OBJECTIVE: The aim of this study was to report three cases of what are considered atypical femoral fractures and their responses to the use of strontium ranelate and teriparatide. PATIENTS: We studied three postmenopausal women with a diagnosis of osteoporosis who suffered fractures of the subtrochanteric region and femoral diaphysis with no major trauma while on long-term use of bisphosphonates. RESULTS: All the major features of atypical femoral fractures highlighted in the Task Force Report of the American Society for Bone and Mineral Research were present in the three cases. They had had unconsolidated fractures for approximately 1 yr before being referred to our center. After 3 months on strontium ranelate 2 g/d, serum osteocalcin and serum β-carboxyterminal telopeptide had increased in case 1 by 125 and 100%, respectively, and in case 2 by 50 and 22%, respectively, with total closure of the fracture. In case 3, after 1 month on teriparatide 20 μg/d, a radiographic closure of the fracture was achieved, and 3 months later serum osteocalcin and serum β-carboxyterminal telopeptide had increased by 300 and 22%, respectively. CONCLUSION: Our finding showed that both teriparatide and strontium ranelate had a rapid bone anabolic effect on unhealed atypical fractures associated with chronic bisphosphonate use.