Predicting osteomyelitis in patients whose initial MRI demonstrated bone marrow edema without corresponding T1 signal marrow replacement.

We endeavored to determine which characteristics of diabetic ulcers portend the strongest risk for osteomyelitis in patients whose initial T1-weighted imaging was normal. By determining which features have a greater risk for osteomyelitis, clinicians can treat patients more aggressively to reduce the sequela of inadequately treated osteomyelitis.We performed a retrospective analysis of MR imaging from 60 pedal ulcers with suspected osteomyelitis. Ulcer dimensions and depth were measured. Ratios of marrow ROI/joint fluid ROI on T2/STIR sequences were obtained. Progression to osteomyelitis on subsequent MRI was characterized by loss of normal marrow signal on T1-weighted images. Statistical analysis was performed with a two-sample t test and Cox proportional hazard model. A p value < 0.05 was used as the threshold for statistical significance.

Sixty MR exams were identified. Thirty-four progressed to osteomyelitis. Marrow ROI/joint fluid ratios averaged 65% in the osteomyelitis group, and 45% in the non-osteomyelitis group, p < 0.001. ROI ratios > 53% had a 6.5-fold increased risk of osteomyelitis, p < 0.001. Proximity to bone averaged 6 mm in the osteomyelitis group and 9 mm in the non-osteomyelitis group, p = 0.02. Ulcer size averaged 4 cm² in the osteomyelitis group versus 2.4 cm² in the non-osteomyelitis group, p = 0.07. Ulcers greater than 3 cm² has a 2-fold increase in the risk of osteomyelitis, p = 0.04.

Increasing bone marrow ROI signal/joint fluid ratios on T2/STIR images were the strongest risk factors for developing osteomyelitis, while ulcer size and depth are weaker predictors.