A significant clinical problem is fracture-related infection (FRI), which frequently arises following fractures or surgical operations that specifically impact the lower limbs. FRI is still difficult to diagnose, especially in chronic patients that frequently exhibit a wide range of unusual clinical symptoms. Even if a consensus has been presented by the AO international expert group, there are still no reliable and consistent diagnostic techniques, particularly when contrasted with the recognized standards for periprosthetic joint infections (PJIs).
By determining ideal maximum standardized uptake value (SUVmax) thresholds and examining sub-group-specific diagnostic performance, this study seeks to assess the diagnostic accuracy of 18F-FDG PET/CT for refractory FRIs in the lower limbs.
A total of 429 PET/CT images from a tertiary orthopaedic center conducted between November 2016 and October 2021 were included in this retrospective analysis. Included were patients with probable refractory FRI, which is defined as an infection that has persisted after at least 2 previous therapies.
Microbiological cultures, histological examination, intraoperative results, and follow-up data were all included in the reference standard. Receiver operating characteristic curve analysis was used to compute diagnostic performance parameters, such as sensitivity, specificity, and area under the curve (AUC). The patients were classified in sub-group analyses according to the time since prior surgery and the clinical presentation.
AUC for PET/CT was 0.84, indicating strong diagnostic performance. With a sensitivity of 70.7% and specificity of 85.6%, the ideal SUVmax threshold was 4.75. According to subgroup studies, customized thresholds increased diagnosis accuracy; at a threshold of 5.05., the "No signs + Early phase" group had the best accuracy (87.5%) and specificity (89.4%).
By separating infection from leftover metabolic activity, a more stringent cut-off of 3.95 in the "No signs + Over phase" group, on the other hand, reduced overdiagnosis. Given the difficulties in identifying chronic infections, the "Over phase" group had the highest false-positive rate (42.4%) and the best specificity (90.1%) at a cut-off of 4.65. These results highlight how SUVmax thresholds vary depending on the clinical context.
Overall, 18F-FDG With stratified SUVmax criteria that improve diagnosis accuracy dependent on the period since prior surgery and symptom manifestation, PET/CT is a dependable diagnostic tool for refractory FRI. By enhancing infection control and lowering recurrence rates, PET/CT proves to be cost-effective over the long run, even with its high initial cost.
Source:
Cai, W., Lu, Y., Ren, Z., Zhang, Y., Cheng, P., Chen, X., Han, P., & Xu, Z. (2025). Real-world experience of the role of 18F-fluorodeoxyglucose positron emission tomography/CT refractory fracture-related infection on lower limbs : a retrospective diagnostic study: A retrospective diagnostic study. The Bone & Joint Journal, 107-B(8), 846–856. https://doi.org/10.1302/0301-620X.107B8.BJJ-2024-1158.R2
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