Purpose: The purpose of this study is to describe the usefulness of 18F-FDG PET/CT scanning in the diagnosis and follow-up of stage 0 Charcot foot (CNO) and CNO outcomes when therapeutic options are driven by this image modality.
Patients and methods: We selected 25 out of 40 diabetic patients with an acute CNO, without any bone involvement at x-ray (stage 0 CNO). Diagnostic criteria were inflammatory clinical signs of the affected foot and skin temperature difference greater than 2°C compared with the contralateral foot (ΔT). All patients underwent x-ray, MRI, and 18F-FDG PET/CT scanning (expressed as standardized uptake value, SUVmax) at baseline (T0). All patients underwent another 18F-FDG PET/CT within 1 month after ΔT was less than 2°C [clinical recovery (T1)] and again every 3 months until SUVmax was less than 2 [final recovery (T2)]; at this time, MRI confirmed the end of the inflammatory condition.
Results: T0 ΔT was 3.04 ± 1.65°C. All patients showed T0 SUVmax of the affected foot higher than the contralateral one (3.83 ± 1.087 vs. 1.24 ± 0.3; P < 0.001). At clinical recovery (T1), defined by ΔT below 2°C, the inflammatory signs were no longer present (T0 vs. T1 ΔT = 3.04 ± 1.65 vs. 0.9 ± 0.55°C; P < 0.0001). At T1, SUVmax was unchanged from T0 (3.80 ± 1.69 vs. 3.83 ± 1.09; P = ns). At final recovery (T2), ΔT was 0.74 ± 0.29°C (similar to T1 ΔT), while the SUVmax dropped from T1 to T2 (3.8 ± 1.69 vs. 1.72 ± 0.52; P < 0.0001). Standard therapy was total contact cast and removable cast walker until T2 (15.12 ± 5.45 mo). No patient developed foot bone fractures nor had relapses during follow-up (21.75 ± 16.7 mo).
Discussion: PET/CT scan allows the quantification of the inflammatory process; therefore, it may drive clinical decisions in the management of acute CNO better than clinical criteria. None of our patients developed foot bone fractures or had relapses during follow-up driven by PET/CT scan.