Is osteomyelitis (infection of the bone) present in the left foot, as indicated by X-ray (radiograph)?

From the Guidelines

X-ray of the left foot is recommended as the initial imaging study to evaluate for osteomyelitis, despite its limitations in early detection, due to its widespread availability and low cost. The procedure involves taking multiple radiographic views of the foot while the patient remains still. X-rays can show bone destruction, periosteal reaction, or soft tissue changes that may suggest infection, but these findings typically appear 10-14 days after infection onset 1. Negative X-ray results don't definitively rule out early osteomyelitis.

Key Considerations

• The timing of the imaging greatly influences its usefulness, as longer-standing cases are far more likely to show bony abnormalities on plain radiographs than those present for less than 2–3 weeks 1.
• If clinical suspicion remains high despite negative X-rays, additional imaging such as MRI (which offers better sensitivity for early infection), bone scan, or CT may be necessary 1.
• X-ray serves as a reasonable first-line imaging study due to its availability, low cost, and ability to assess for other conditions like fractures or arthritis that might mimic infection symptoms.
• Patients should inform the technologist about any possibility of pregnancy before the procedure.

Alternative Imaging Options

• MRI has been the most commonly ordered advanced imaging technique to diagnose DFO, with moderate costs and wide availability in high-income countries 1.
• MRI gives a good overview of the anatomy of soft tissues as well as bones and joints, which can be of aid for detecting pre-operatively any purulent collections or the extent of bone involvement.
• Other imaging techniques, such as FDG-PET/CT, HMPAO-labelled leucocyte scintigraphy, or 99mTc labelled Ubiquicidin (UBI) SPECT/CT, may be considered in patients with a contraindication to MRI or when the diagnosis remains in doubt 1.

From the Research

Diagnostic Approach for Osteomyelitis

• The initial imaging procedure for diagnosing osteomyelitis is radiography, but its sensitivity is low in the early stages of the disease 2, 3.
• Magnetic resonance imaging (MRI) has a higher sensitivity for detecting areas of bone necrosis in advanced stages 2, 3.
• MRI findings, such as bone marrow edema, T2-weighted image hyperintensity, T1-weighted image confluent signal, and cortical erosion, are indicative of osteomyelitis 4.
• The sensitivity and specificity of MRI for diagnosing osteomyelitis are 90% and 80%, respectively 4.

Imaging Tests for Osteomyelitis

• MRI, positron emission tomography (PET), and single-photon emission computed tomography (SPECT) have high diagnostic accuracy for osteomyelitis 5.
• The diagnostic accuracy of MRI, PET, and SPECT does not appear to vary with the potential cause of osteomyelitis or with the body part scanned 5.
• Radiography, computed tomography, and scintigraphy have generally inferior diagnostic accuracy compared to MRI, PET, and SPECT 5.

Laboratory Tests for Osteomyelitis

• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are routinely ordered inflammatory biomarkers for evaluating foot infection 6.
• Optimal cutoff values for ESR and CRP to diagnose osteomyelitis in patients with diabetes-related foot infections are 60 mm/h and 7.9 mg/dL, respectively 6.
• An ESR threshold of 60 mm/h demonstrates a sensitivity of 74% and specificity of 56% for osteomyelitis, while a CRP threshold of 7.9 mg/dL has a sensitivity of 49% and specificity of 80% 6.