Objective: confluent T1 hypointense marrow signal is widely accepted to represent
osteomyelitis on MRI. Some authors have suggested that non-confluent bone marrow signal abnormality should be considered early
osteomyelitis. The purpose of this study was to address this issue by comparing the rate of
osteomyelitis and
amputation based on T1 marrow signal characteristics. Materials and methods: a total of 112 patients who underwent MRI of the foot for the evaluation of possible
osteomyelitis were included. Patients were assigned to confluent T1 hypointense, reticulated T1 hypointense, and normal bone marrow signal groups. Results: patients with confluent T1 hypointense signal on MRI had significantly higher rates of
osteomyelitis and
amputation at 2 and 14 months post-MRI than the reticulated T1 hypointense group ( p < 0.001 ). Six patients had normal T1 signal, 16.7 % of whom had
osteomyelitis and underwent
amputation by 2 months post-MRI. Of 61 patients with reticulated T1 hypointense signal, 19.7 % had a diagnosis of
osteomyelitis at 2 months post-MRI and 30.8 % had a diagnosis of
osteomyelitis at 14 months post-MRI; moreover, 14.8 % and 31.5 % underwent
amputation by 2 and 14 months post-MRI, respectively. Of 45 patients with confluent T1 hypointense signal, 73.3 % of patients had
osteomyelitis at 2 months post-MRI and 82.5 % had
osteomyelitis at 14 months post-MRI. In this group, 66.7 % underwent
amputation by 2 months post-MRI and 77.8 % underwent
amputation by 14 months post-MRI. Conclusions: over half of the patients with suspected pedal
osteomyelitis who had reticulated or normal T1 bone marrow signal on MRI healed with conservative measures. Therefore, we recommend terminology such as "
osteitis", "reactive
osteitis", or "nonspecific reactive change" to describe bone marrow
edema-like signal and reticulated hazy T1 hypointense signal without associated confluent T1 hypointensity. Moreover, we recommend that the MRI diagnosis of
osteomyelitis is reserved for confluent T1 hypointense bone signal in the area of concern.