Ultrasonography Cannot Exclude Osteomyelitis in Diabetic Foot Ulcers: A Cross-Sectional Diagnostic Accuracy Study...

Diabetic foot ulcers (DFUs) can lead to amputation, especially when complicated by osteomyelitis (OM) or soft tissue infection. Although MRI is the standard imaging method, ultrasonography (US) is increasingly used because it is more accessible. This study compared the diagnostic performance of US and MRI in DFU-related infections.

In this descriptive cross-sectional study, consecutive adults with diabetes and suspected diabetic foot infection underwent both US and MRI. One ulcer per patient wasanalysed. US was compared with expert clinical assessment for cellulitis and with MRI for abscess and OM, following IWGDF recommendations. Diagnostic measures were calculated overall and by ulcer severity.

Among 127 patients, most had advanced Wagner grades (3-5) and forefoot ulcers. Cellulitis was clinically present in all cases; MRI and US concordance with the clinical diagnosis was 100.0% and 99.2%, respectively. For abscesses, US showed 100% sensitivity but low specificity, resulting in moderate accuracy. For OM, US had very poor sensitivity (17.9%) despite high specificity, especially in severe ulcers. MRI detected no OM in moderate-grade ulcers.

US showed near-complete concordance with MRI for cellulitis, though this was assessed in a study in which cellulitis was universally present, and US performs poorly for OM and cannot reliably exclude bone infection. It is best used as an initial triage tool, while MRI remains essential when OM is suspected. Because MRI is not a perfect reference standard, the findings reflect diagnostic concordance rather than absolute accuracy and support a tiered imaging approach.