Intra and extramedullary fat globules as an MRI marker for osteomyelitis

Abstract

Magnetic resonance imaging (MRI) findings of acute osteomyelitis vary from non-specific bone marrow edema to more reliable signs such as bone destruction, periosteal reaction, and sequestrum. In some cases, imaging features could overlap with other conditions such as trauma and bone tumors. Intra and extramedullary fat globules are a helpful MRI marker for osteomyelitis, as shown in the following case report. We report the MRI findings of a 15-year-old young man with distal femur osteomyelitis, associated with intra and extramedullary fat globules.We present the MRI features of the case and emphasize the importance of noting additional signs of osteomyelitis to make a precise diagnosis.

Letter to the Editor: Imaging update on musculoskeletal infections

“…The increasing intramedullary pressure leads to a rupture of the osseous cortex and expulsion of medullary fat into the adjacent soft tissues. 4,5 This sign is usually seen in aggressive acute osteomyelitis resulting in extrusion of medullary fat as opposed to a subacute, slowly progressive process. 4 Although some authors have considered the fat globules sign to be pathognomonic for acute osteomyelitis, 3 actually, it can also be seen in medullary infarction, trauma, bone sarcomas after treatment with chemotherapy and/or radiotherapy, and Gaucher disease.…”

“…However, in the correct clinical context it can play an important role in diagnosis of acute osteomyelitis and in the differential diagnosis with bone tumors. 4,5 Therefore, the visualization of the intramedullary and/or extramedullary fat globules sign on MRI is an important feature of acute osteomyelitis, which can be used in the differentiation from other bone diseases.…”