Bilateral atypical femoral diaphyseal fractures in a patient treated with alendronate sodium

Antiresorptive agents have been used as primary or first-line therapy in managing patients with osteoporosis. Bisphosphonates in particular are used widely to reduce bone resorption, increase bone mineral density, improve bone quality and therefore reduce fracture risk. However, prolonged use of bisphosphonates may cause over-suppression of bone resorption, leading on to accumulation of micro-damage in bone. This in turn might lead on to atypical femoral fractures. A patient treated with alendronate sodium for 8 years, and presenting with bilateral atypical femoral diaphyseal fractures is reported. X-rays of both femurs showed typical horizontal fracture line involving the thick lateral cortex with short oblique fracture pattern over the medial cortex. This fracture pattern was further confirmed with intra-operative examination of the fracture ends. Histopathological examination of the endocortical fragment removed from the proximal fracture end showed absence of osteoclasts and osteoblasts. Bone mineral density with dual energy X-ray absorptiometry (DXA) scan showed osteopenia over the femoral neck. Blood investigations did not show significant abnormalities. Bone turnover marker levels were not reliable, as presence of fracture might have altered the marker levels. Both femoral fractures united well. The patient reported here had complete pictures on X-ray examination, intra-operative findings, histopathological examination, DXA, as well as blood test results. Complete data should be collected from patients treated with alendronate sodium presenting with atypical femoral fractures to show any link between the use of alendronate sodium with atypical fracture of femur.