Objective: The objective of this study was to assess the clinical significance of increased fluorine-18-fluorodeoxyglucose (F-FDG) uptake on PET/CT in joints for evaluation of symptomatic osteoarthritis (OA) and prediction of progression.
Patients and methods: In this prospective study, shoulder, hip, and knee joints were imaged in 65 patients undergoing routine F-FDG PET/CT imaging. Patients completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire to assess joint pain, stiffness, and physical function. Standardized uptake values (SUVs) were measured in hip, knee, acromioclavicular (AC), and glenohumeral (GH) joints. Scout PET/CT images were evaluated for OA using the Kellgren and Lawrence (K/L) system. Patients were followed-up for 5 years to determine the progression of OA on the basis of follow-up imaging or surgical intervention.
Results: SUV of knee (r=0.309, P=0.0003), hip (r=0.260, P=0.0027), AC (r=0.186, P=0.0313), and GH (r=0.191, P=0.0271) joints correlated with WOMAC overall scores. Furthermore, SUV of knee (r=0.410, P<0.0001), hip (r=0.203, P=0.0199), and AC (r=0.364, P<0.0001) joints correlated with K/L scores. The area under the receiver operating characteristic curves for SUV were 0.734 (knee), 0.678 (hip), 0.661 (AC), and 0.544 (GH) for symptomatic OA detection based on WOMAC overall z-score greater or equal to 2. Compared with K/L score [hazard ratio (HR)=0.798, P=0.5324], age (HR=0.992, P=0.8978), and WOMAC overall score (HR=1.089, P=0.1265), only SUV (HR=5.653, P=0.0229) was an independent predictor of OA progression in the knees.
Conclusion: F-FDG PET/CT may be helpful with localization of painful abnormalities in the inflamed regions of the joints, which could potentially be used to direct individualized treatment in moderate and severe OA. Furthermore, SUV measurement on F-FDG PET/CT could serve as an inflammation activity index in the knees that may be predictive of outcomes and progression rate of OA.