From the Guidelines
The best way to diagnose osteomyelitis is through a combination of MRI imaging and bone biopsy, as MRI is the most accurate imaging study for defining bone infection, with high sensitivity and specificity for detecting bone infection, as noted in the 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections 1. When considering osteomyelitis, obtaining plain radiographs of the foot is recommended as they are widely available and relatively inexpensive, but it may take weeks after the onset of bone disease for osteomyelitis to become evident on plain radiographs. MRI is the preferred imaging modality due to its ability to visualize bone marrow edema, soft tissue involvement, and abscess formation early in the disease process. A bone biopsy with culture remains the gold standard for definitive diagnosis, allowing identification of the causative organism and guiding appropriate antibiotic therapy, as stated in the 2004 diagnosis and treatment of diabetic foot infections study 2. Additional imaging options include plain radiographs, CT scans, and nuclear medicine studies like bone scans or white blood cell scans, which can be helpful when MRI is contraindicated. Laboratory tests such as elevated inflammatory markers (ESR, CRP) and blood cultures support the diagnosis but are not specific, as mentioned in the 2016 IWGDF guidance on the diagnosis and management of foot infections in persons with diabetes 3. For suspected osteomyelitis, prompt evaluation with MRI followed by bone biopsy when feasible provides the most accurate diagnosis, enabling targeted treatment with appropriate antibiotics, which typically requires 4-6 weeks of therapy. Some key points to consider when diagnosing osteomyelitis include:
- MRI is the most accurate imaging study for defining bone infection
- Bone biopsy with culture is the gold standard for definitive diagnosis
- Plain radiographs can be used as an initial imaging study, but may not show changes until weeks after the onset of bone disease
- Laboratory tests such as elevated inflammatory markers and blood cultures can support the diagnosis, but are not specific
- Prompt evaluation with MRI and bone biopsy when feasible provides the most accurate diagnosis and enables targeted treatment with appropriate antibiotics.
From the Research
Imaging Modalities for Osteomyelitis
The best way to see osteomyelitis involves the use of various imaging modalities, including:
- Radiography: Although its sensitivity is low in the early stages of the disease, it is typically the first imaging procedure used 4, 5
- Magnetic Resonance Imaging (MRI): Has a higher sensitivity for detecting areas of bone necrosis in advanced stages, both with and without contrast material 4, 6, 5
- Computed Tomography (CT): Can be useful for detecting early osseous erosion and documenting the presence of sequestra 7
- Positron Emission Tomography (PET): Highly accurate for evaluating chronic osteomyelitis and differentiating it from soft tissue infection 6, 7
- Single-Photon Emission Computed Tomography (SPECT): Also highly accurate for evaluating chronic osteomyelitis 6, 7
- Technetium-99m hexamethylpropyleneamine oxime white blood cell scintigraphy: Has higher diagnostic accuracy, similar to PET or MRI 6
- Ultrasound: A noninvasive method for evaluating involved soft tissues and cortical bone, and may provide guidance for diagnostic or therapeutic aspiration, drainage, or tissue biopsy 7
Diagnostic Accuracy
The diagnostic accuracy of these imaging modalities varies, with:
- MRI, PET, and SPECT having high diagnostic accuracy 6
- Scintigraphy, CT, and radiography having generally inferior diagnostic accuracy 6
- No clear reason to prefer one test over another in terms of diagnostic accuracy, although MRI may be preferable due to its wider availability and lack of ionizing radiation 6
Clinical Considerations
It is essential to consider the clinical context and patient factors when choosing an imaging modality, including: