Atlantoaxial joint involvement in rheumatoid arthritis: Insights from ¹⁸F-NaF and ¹⁸F-FDG PET

Rheumatoid arthritis (RA) is a leading cause of cervical spine morbidity and neurological dysfunction. Atlantoaxial joint involvement is frequently observed on computed tomography (CT) or magnetic resonance imaging (MRI), yet structural imaging alone cannot visualize inflammatory or osteogenic changes characteristic of active disease. Fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT enables the in-vivo assessment of glucose metabolism while ¹⁸F-sodium fluoride (¹⁸F-NaF) reflects osseous metabolism. In combination, these tracers offer complementary insights that may facilitate detection of RA-related pathophysiology. In this report, we present active bone turnover of the atlantoaxial joint without evidence of inflammation identified on PET/CT in a 59-year-old woman with RA.