Diagnostic performance comparison of conventional radiography to magnetic resonance imaging for suspected osteomyelitis of the extremities: a multi-reader study

Objective: To determine whether MRI provides improved diagnostic accuracy compared to radiography for the diagnosis of extremity osteomyelitis (OM) with multi-reader analysis. Methods: In this cross-sectional study, three musculoskeletal fellowship-trained expert radiologists evaluated cases of suspected OM in two rounds—first using radiographs (XR), then with conventional MRI. Radiologic features consistent with OM were recorded. Each reader recorded individual findings on both modalities and rendered a binary diagnosis along with certainty of final diagnosis on a confidence scale of 1–5. This was compared with the pathology-proven diagnosis of OM to determine diagnostic performance. Intraclass correlation (ICC) and Conger’s Kappa were used for statistics. Results: XR and MRIs of 213 pathology proven cases (51.5 years ± 14.0 years, mean ± St.Dev.) were included in this study, with 79 tested positive for OM and 98 were positive for a soft tissue abscess, with 78 patients being negative for both. In total, 139 were males and 74 females with bones of interest in the upper and lower extremities in 29 and 184 cases, respectively. MRI showed significantly higher sensitivity and negative predictive value than XR (p < 0.001 for both metrics). Conger’s Kappa for OM diagnosis were 0.62 and 0.74 on XR and MRI, respectively. Reader confidence improved slightly from 4.54 to 4.57 when MRI was used. Conclusions: MRI is a diagnostically more effective imaging modality than XR for finding extremity osteomyelitis with better inter-reader reliability. Clinical relevance statement: This study validates the diagnosis of OM with MRI over XR but adds novelty because it is the largest study of its kind with a clear reference standard to guide clinician decision making. Key Points: • Radiography is the first-line imaging modality for musculoskeletal pathology but MRI can add value for infections. • MRI shows greater sensitivity for the diagnosis of osteomyelitis of the extremities than radiography. • This improved diagnostic accuracy makes MRI a better imaging modality for patients with suspected osteomyelitis.