Osteomyelitis is a bacterial or fungal infection of the bone that is more common in children than in adults (Restrepo 2024). It can develop due to hematogenous spread, direct trauma, or after surgery. Long bones, particularly the femur and tibia, are commonly affected due to their rich metaphyseal blood supply, a predisposing factor to bacterial colonization (Restrepo 2024).

Common clinical symptoms include fever, localized pain and tenderness of the affected bone, swelling, and limited range of motion. Infants may show irritability or lethargy, and overall unspecific signs (Restrepo 2024).

Due to its variable presentation, osteomyelitis represents a diagnostic challenge, requiring a combination of clinical evaluation, laboratory tests (e.g., white blood cell count and C-reactive protein), and imaging (Pineda 2009, Wu 2007).

The radiological assessment includes various techniques starting from radiographs as first-line approach. Indeed, X-ray is often used to rule out fractures when the clinical history is not clear more than to diagnose osteomyelitis because it is affected by low sensitivity especially in the early phase. In fact, skeletal changes (e.g., periosteal reaction, lytic and/or sclerotic areas) become evident only after 7–10 days. Ultrasound may provide information regarding the extension of the infection to the soft tissues. Last, MR is considered the gold standard for early diagnosis because of the accurate assessment of bone marrow (Pugmire 2014, Termaat 2005).

Regarding the global assessment, a biopsy is suggested in unclear cases at imaging or when multidrug-resistant pathogens are suspected (Pineda 2009, Wu 2007).

The treatment is based on antibiotics, often administered intravenously in the initial phase. In severe cases, surgical drainage may be necessary (Gornitzky 2020). Early detection and prompt treatment are crucial to prevent complications such as osteonecrosis, sequestra in chronic osteomyelitis and/or growth alterations (Restrepo 2024).

Since the diagnosis of osteomyelitis relies on imaging but in children the clinical symptoms might be misleading mimicking other diseases, we decided to assess the appropriateness of the request for MR imaging in children with suspected osteomyelitis.