Grading Fractures on Foot and Ankle X-rays and MRI Scans in the Active Charcot Foot in Diabetes: How Strong Is the Agreement Between Modalities?

OBJECTIVE To compare X-ray and MRI as diagnostic tests of active Charcot neuro-osteoarthropathy (CNO) in diabetes. RESEARCH DESIGN AND METHODS X-rays and MRI scans of 48 participants were rated for severity of fracture (0 = no fracture, 1 = fracture, 2 = collapse/fragmentation), and for absence/presence of bone marrow edema (BME) on MRI and absence/presence of bone injury on X-ray. The agreement between modalities was assessed with tests for symmetry, marginal homogeneity, and κ-coefficients. RESULTS X-ray underscored MRI in grading fractures in the metatarsals (P = 0.05) and tarsals (P < 0.001) and reported as normal 79% of the bones with BME. The agreement between X-ray and MRI for grading severity of fracture was moderate to substantial (κ = 0.53; P < 0.001) and for detecting bone injury, slight to fair (κ = 0.17; P < 0.001). CONCLUSIONS The significant underperformance of X-ray in the assessment of the hot, swollen foot in diabetes should be considered when confirming or refuting the diagnosis of active CNO.