# Combined use of 18 F-FDG PET/CT and MRI for evaluating infection status and clinical outcomes before reimplantation in two-stage revision arthroplasty

## TL;DR

This study shows that combining PET/CT and MRI scans improves accuracy in predicting infection recurrence before reimplantation surgery for joint infections.

## Contribution

The study demonstrates that combining 18F-FDG PET/CT and MRI improves diagnostic accuracy for infection status in revision arthroplasty.

## Key findings

- 18F-FDG PET/CT results significantly correlated with clinical outcomes (p = 0.017).
- MRI findings also showed a significant association with clinical outcomes (p = 0.009).
- Combining PET/CT and MRI achieved 100% sensitivity and 100% negative predictive value.

## Abstract

Two stage revision arthroplasty (TSRA) is the standard treatment for periprosthetic joint infections (PJI); however, the utility of imaging in determining infection status before reimplantation remains unclear. The aim of this study was to evaluate whether pre-reimplantation 18 F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and magnetic resonance imaging (MRI) findings are associated with the risk of recurrent infection after second-stage revision arthroplasty.

A total of 47 patients (26 women and 21 men) diagnosed with PJI according to the 2011 Musculoskeletal Infection Society (MSIS) criteria and treated with TSRA were retrospectively included in the study. A total of 26 hip and 21 knee PJI cases were evaluated. 18F-FDG PET/CT and MRI scans were obtained before reimplantation, and the images were interpreted by a radiologist and a nuclear medicine specialist blinded to the patient’s clinical outcomes. 18F-FDG PET/CT and MRI findings were compared with postoperative infection outcomes.

After reimplantation, no infection was observed in 33 patients, whereas 14 patients experienced infection recurrence requiring surgical intervention. 18F-FDG PET/CT alone identified 31 patients as infected and 16 as non-infected. 18F-FDG PET/CT results significantly correlated with clinical outcomes (p = 0.017). MRI alone identified 20 patients as infected and 27 as non-infected. A statistically significant association was observed between MRI findings and clinical outcomes (p = 0.009). When 18F-FDG PET/CT and MRI findings were combined, diagnostic accuracy improved, yielding a sensitivity of 100% and negative predictive value (NPV) of 100%.

A negative 18F-FDG PET/CT and MRI scan can provide an important reference point, strongly suggesting infection eradication and supporting a decision to proceed with the second stage of reimplantation surgery.