Bilateral Atypical Femur Fracture in a Patient Under Bisphosphonate Treatment

Introduction Typical characteristics of osteoporosis include low bone mass with microarchitectural disruption and skeletal fragility, with increased risk of vertebral and nonvertebral fracture (1). Bisphosphonates suppress osteoclast activity, resulting in the inhibition of bone resorption. The beneficial effects of bisphosphonates on prevention of vertebral and nonvertebral osteoporotic fractures and increase in bone mineral density have been substantiated by several clinical trial data (2-4). Despite the beneficial effects of bisphosphonates, a meta-analysis of six cohorts and five case-control studies reported an increased risk of atypical fracture in bisphosphonate users (5). Vitamin D deficiency is a co-determinant causing fractures, which is a common issue, especially in the elderly population. Clinical studies indicate an association between vitamin D deficiency, osteoporosis, and increased risk of fractures due to falls (6-9). We present here the case of a 79-year-old woman who has been on bisphosphonate treatment for eight years (alendronate for five years, ibandronate for three years). She had bilateral femur diaphyseal fractures occurring within an interval of few months. Laboratory results indicated vitamin D deficiency. We also attempted to investigate the association of atypical femur fractures with the long-term use of bisphosphonate and with vitamin D deficiency.