Update on MRI findings of osteomyelitis of long bones in the adult population.

OBJECTIVES

To evaluate the usefulness of new and established MRI signs of osteomyelitis in long bones in adults.

METHODS

All patient records over a 9-year period with clinical or MRI suspicion for osteomyelitis were retrospectively reviewed, using strict criteria for proof of infection. Two musculoskeletal radiologists independently reviewed the MRIs of proven osteomyelitis.

RESULTS

Out of 45 MRIs of confirmed osteomyelitis, 2 MRIs (4%) did not show confluent low-signal intensity on T1-weighted images, but all showed confluent high-signal intensity on T2-weighted images. Central hypoenhancing regions of marrow without abscess formation were found in 15-18/35 (43-51%) cases where gadolinium was given. We often found multiple foci of marrow replacement in the same bone. The areas of marrow involvement often had an irregular contour. Penumbra sign, marrow fat globules, and sequestra were uncommon.

CONCLUSION

Multiple foci of bone marrow signal abnormalities, an irregular contour of marrow abnormality, and central marrow hypoenhancement without abscess are common signs of osteomyelitis of long bones in adults. Confluent low T1-signal intensity is not always present.