The Sauvé-Kapandji procedure (SK), which combines distal radioulnar joint arthrodesis with creation of an ulnar pseudarthrosis, achieves good outcomes with few complications for patients with distal radioulnar joint instability or arthritis. The authors describe a case of atypical fracture of the radial diaphysis that occurred in a 79-year-old woman with rheumatoid arthritis who had undergone SK 18 years earlier. The patient had taken alendronate for osteoporosis for 13 years but had discontinued treatment 2 years before onset of symptoms. Retrospective review of serial radiographs revealed focal cortical thickening at the fracture site beginning 18 months before the onset of prodromal pain and becoming more evident over time. The patient underwent surgical repair of the fracture, which had occurred at the attachment of the pronator teres. Histopathological examination of bone excised from the fracture site and from the iliac graft used for fracture repair revealed markedly fewer trabecular osteoblasts than normal and no osteoclasts, indicating severe suppression of bone turnover. It is important to evaluate the radial diaphysis on radiographs taken after SK for early signs of atypical fracture, especially in patients with rheumatoid arthritis and a history of bisphosphonate use. Given the patient's history of bisphosphonate use and the similar radiographic appearance to atypical femoral fractures, the authors applied the term atypical radial fracture to this case. [Orthopedics. 2023;46(5):e317-e320.].