Magnetic resonance findings in chronic osteomyelitis fistula

INTRODUCTION: Osteomyelitis is a common inflammatory process caused by an infection which is usually from gram-positive germs. Acute, subacute and chronic forms can be distinguished both clinically and radiographically, each of them presenting different patterns but which are not always easy to recognize. Besides clinical-laboratory data, imaging methods are also useful to make the diagnosis; in chronic forms, MRI has higher sensitivity in recognizing the active foci and the presence of sinus tracts than the other techniques. MATERIAL AND METHODS: We examined nine patients with suspected chronic osteomyelitis with a sinus tract, all of them submitted to radiographic and MR examinations. MRI was performed with a .5 T magnet using a surface coil for joint studies; T1-weighted SE (TR 300-500, TE 20), T2-weighted GE (TR 500-700, TE 20, FA 35 degrees) and FIR sequences with fat suppression (TR 3000, TE 20, TI 100) were performed on the axial, sagittal and coronal planes. Three patients underwent CT too. RESULTS: Radiography showed the osteostructural changes as osteolytic and osteosclerotic areas. CT depicted not only the changes seen radiographically, but also increased bone marrow density. MRI demonstrated active foci of bone marrow appearing as low-intensity areas in T1, with increased intensity in T2 GE and fat-suppressed FIR images; it also depicted the sinus tracts as areas of decreased signal on T1 and of increased signal on FIR images. CONCLUSIONS: Based on our experience and in agreement with the literature data, we believe that MRI is more useful to diagnose the active foci of bone marrow and the sinus tracts in chronic osteomyelitis, especially with T1-weighted SE and fat-suppressed FIR sequences.