Spontaneous bilateral femoral neck fractures in a young male adult: a case report and literature review

Background: Simultaneous bilateral femoral neck fracture is a very rare condition, even in osteoporotic elderly individuals. We report an atypical case of a young male adult who developed simultaneous bilateral femoral neck fractures without previous trauma or overuse. Case presentation: A 33-year-old man presented with discomfort in the bilateral groin, which had started 2 weeks previously. Bilateral femoral neck fractures were observed on a radiograph, and in addition, a fracture line was seen at the right subchondral region of the acetabulum using magnetic resonance imaging (MRI). Although the patient had no obvious risk factors associated with bone fragility, his bone mineral density measured using dual X-ray absorptiometry indicated severe osteoporosis (lumber spine: T score - 3.4 standard deviation [SD]; femoral neck: T score - 2.8 SD). Serum 25-hydroxyvitamin D level was deficient (19 ng/mL), which was considered to be partly due to non-sunlight exposure for 3 years owing to social withdrawal. Bilateral osteosynthesis was performed, considering his young age, although more than 2 weeks had passed since the onset of the fracture. Bone union and non-occurrence of osteonecrosis of the femoral head were confirmed via radiography and MRI 8 months after the surgery. Conclusions: Our case suggests that simultaneous non-traumatic bilateral femoral neck fractures can occur in healthy young men.