Atypical ulnar fracture induced by chronic mechanical overload in the absence of antiresorptive therapy: A case report

Atypical ulnar fractures are rare and typically associated with prolonged antiresorptive therapy. We report an 84-year-old female with severe osteoporosis who presented with a transverse proximal ulnar fracture after minor trauma. The patient had no history of long-term antiresorptive therapy and had received only a single denosumab injection 3 years prior. The patient habitually bore weight through the forearms during ambulation. Imaging demonstrated a transverse fracture with cortical thickening and sclerotic margins, consistent with an atypical pattern. Histopathological examination revealed dead bone fragments with the absence of osteocytes, indicating locally suppressed bone turnover. The patient underwent curettage, rigid plate fixation, and allogeneic cancellous bone grafting, with radiographic union achieved at 7 weeks. This case demonstrates that chronic mechanical loading on osteoporotic bone can contribute to the development of atypical ulnar fracture, even in the absence of prolonged antiresorptive therapy.