Lotte C. A. van der Broeck (Maastricht / NL), Anna J. L. Lodewijks (Maastricht / NL), Cristina Mitea (Maastricht / NL), Daan Loeffen (Maastricht / NL), Martijn Poeze (Maastricht / NL), Shan S. Qiu Shao (Maastricht / NL), Jan Geurts (Maastricht / NL), Taco J. Blokhuis (Maastricht / NL)
Introduction. The diagnosis of low-grade infection in post-traumatic long bone non-unions poses challenges due to the absence of clinical signs. This study aimed to assess the diagnostic accuracy of 18F-FDG PET-CT scans for low-grade infection in post-traumatic long bone non-unions.
Material & Methods. A retrospective study included adult patients with a long bone non-union, suspected of infection. All patients underwent 18F-FDG PET-CT scans as the index test before surgical intervention, with peri-operative cultures obtained during surgery serving as the reference standard. Semiquantitative analyses were performed on the standardized uptake value (SUV) measurements obtained from the PET-CT scans. Diagnostic accuracy measures including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Receiver operating characteristic (ROC) curve analysis was employed to evaluate the discriminatory ability of SUV measurements.
Results. The study included 51 18F-FDG PET-CT scans and cultures from 50 patients with long bone non-unions. The diagnostic accuracy was found to be 0.67 (95% CI 0.44 - 0.87). The PPV and NPV were calculated as 0.79 (95% CI 0.53 - 1.00) and 0.52 (95% CI 0.30 - 0.73), respectively. Quantitative analyses of SUV measurements demonstrate a moderate to low level of accuracy, with all areas under the curve (AUC) values < 0.75 and ROC curves showing a trajectory fairly parallel to the diagonal line.
Conclusion. The findings of this study indicate that the 18F-FDG PET-CT has moderate diagnostic accuracy in detecting low-grade infections in posttraumatic long bone non-unions. A careful interpretation of the scan results is warranted, possibly including the quantitative analysis on tracer uptake as an adjunct. Nevertheless, the diagnostic accuracy in this condition is not as good as in early-onset FRI cases, and this should be taken into account when treating these challenging cases.
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