LAUSR

In the treatment of metastatic bone tumors, bone-modifying agents (BMA) including bisphosphonates and denosumab is known to reduce the frequency of skeletal-related event including severe bone-related pain, hypercalcemia, spinal cord compression, or pathological fracture (1-3). Whereas, atypical femoral fracture (AFF) has been reported as an adverse event following the treatments with BMA. AFF is known to be a kind of stress fracture, and it usually shows typical imaging findings and clinical symptoms. Diagnosing AFF in the hyperacute phase by imaging modalities is challenging, but it is essential for preventing symptomatic fracture. We describe herein a patient with AFF without characteristic plain radiographic findings. However, his magnetic resonance imaging (MRI) showed a signal change at the lateral periosteum of proximal femoral diaphysis a few days before the symptomatic fracture, and the signal change was considered to be a significant MRI finding in the hyperacute phase of AFF.