Osteonecrosis of the Jaw and Bilateral Atypical Femoral Fracture Both Occurring During Treatment for Osteoporosis: A Case Report

Osteonecrosis of the jaw (ONJ) and atypical femoral fracture (AFF) are rare potential adverse effects of bisphosphonates and RANKL antibody therapy. The pathogenic mechanisms of both conditions are known to be independent of each other. Here, we report both conditions sequentially occurring in the same patient. An 81-year-old, obese, diabetic, female was admitted due to hypertensive urgency and persistent jaw pain after tooth extraction. The patient has postmenopausal osteoporosis for fourteen years and was on intermittent, unsupervised treatment with alendronate, denosumab and ibandronate. Upon presentation, the patient was noted with tenderness intraorally of tooth number 35 periapical region. This was associated with elevated erythrocyte sedimentation rate and C-reactive protein. Imaging study showed presence of bony sclerosis which represent a sequestrum in the molar area of the left hemi-mandible. Antibiotic infusion and excision and debridement of left posterior mandible were done. Histopathologic finding was consistent with a diagnosis of osteonecrosis of the jaw. The same patient, upon review, had suffered sequential fracture of both femurs during the eighth and eleventh year of treatment with antiresorptive agents. The fractures were transverse, non-comminuted, at the proximal femoral shaft. Each occurred after a minor trauma and was managed with open reduction and internal fixation. Both fractures were consistent with atypical femoral fractures. ONJ and AFF can occur both in the same patient during prolonged treatment with bisphosphonates and denosumab and may suggest a common pathogenic mechanism.