5. Utility of F-18 FDG Imaging for Diagnosing the Infected Joint Replacement

Area of Science:

• Nuclear Medicine
• Diagnostic Imaging
• Orthopedic Surgery

Background:

• Infection of joint replacements is a significant complication.
• Early and accurate diagnosis is crucial for effective treatment.
• Fluorodeoxyglucose (FDG) positron emission tomography (PET) is a potential imaging modality for infection detection.

Purpose of the Study:

• To prospectively evaluate the diagnostic utility of FDG PET for infected joint replacements.
• To determine the sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of FDG PET in this context.

Main Methods:

• A prospective study involving 26 patients with 31 joint replacements (hips and knees).
• Patients received 150 MBq of FDG intravenously, with imaging performed one hour later using a Hybrid PET system.
• Infection was diagnosed based on increased peri-prosthetic FDG uptake compared to adjacent tissues.

Main Results:

• Of 31 prostheses, 11 were infected.
• FDG PET demonstrated 100% sensitivity, 55% specificity, and 71% accuracy.
• The NPV was 100%, indicating no false negatives, but the PPV was only 55%.

Conclusions:

• FDG PET imaging is highly sensitive for detecting infected joint replacements but lacks specificity.
• Its primary role is as a screening test, not a definitive diagnostic tool.
• FDG PET is not recommended for monitoring treatment response due to a high rate of false-positive results after successful eradication of infection.