What X-ray (radiograph) is recommended for a patient with a severe diabetic foot infection?

Radiographic Recommendations for Severe Diabetic Foot Infections

Plain radiographs (X-rays) of the affected foot are strongly recommended as the initial imaging study for all patients presenting with a severe diabetic foot infection. 1

Initial Imaging Approach

• Plain radiographs should be the first imaging test performed for all patients with a new diabetic foot infection to:
  • Identify bony abnormalities (deformity, destruction)
  • Detect soft tissue gas
  • Identify radio-opaque foreign bodies 1
  • Establish a baseline for future comparison 1

Specific X-ray Views Required:

• Anteroposterior (AP) view
• Medial oblique view
• Lateral projections
• For ankle involvement: AP, mortise, and lateral projections 1
• Ideally, weight-bearing (standing) radiographs should be performed if the patient can bear weight 1
• If weight-bearing is not possible, non-weight-bearing radiographs are an acceptable alternative, though they may not demonstrate malalignments as clearly 1
• Bilateral X-rays should be performed when possible for comparison purposes 1

Advanced Imaging Recommendations

When plain radiographs are negative or inconclusive but clinical suspicion of osteomyelitis remains high:

1. MRI is recommended as the advanced imaging study of choice when:

   • Soft tissue abscess is suspected
   • Diagnosis of osteomyelitis remains uncertain
   • More detailed evaluation of infection extent is needed 1

2. Alternative advanced imaging options when MRI is unavailable or contraindicated:

   • Combination of radionuclide bone scan and labeled white blood cell scan 1
   • WBC scintigraphy with SPECT/CT 1
   • [18F]FDG PET/CT 1

Clinical Scenarios and Imaging Algorithms

Scenario 1: Suspected Osteomyelitis with Positive Probe-to-Bone Test

1. Start with plain X-rays of the foot 1
2. If X-rays are positive with elevated ESR, treat for presumptive osteomyelitis 1
3. If X-rays are negative but clinical suspicion remains high, proceed to MRI or nuclear medicine studies 1

Scenario 2: Suspected Charcot Neuro-osteoarthropathy

1. Start with plain X-rays of the foot 1
2. If X-rays are inconclusive, MRI is the method of choice for diagnosing or excluding Charcot neuro-osteoarthropathy 1
3. If MRI is unavailable, [18F]FDG PET/CT can be used as an alternative 1

Scenario 3: Suspected Superimposed Infection in Charcot Foot

1. Start with plain X-rays of the foot 1
2. If infection is suspected in a patient with Charcot foot, WBC scintigraphy may be more accurate than [18F]FDG PET/CT in differentiating osteomyelitis from Charcot arthropathy 1

Important Clinical Considerations

• The sensitivity and specificity of plain radiographs for osteomyelitis are relatively low, but they remain essential as the initial imaging study 1
• When clinical suspicion for infection remains high despite negative imaging, consider additional imaging modalities 1
• Whenever possible, microbiological or histological assessment should be performed to confirm the diagnosis of osteomyelitis 1
• Bone cultures remain the gold standard for definitive diagnosis of osteomyelitis 2

Common Pitfalls to Avoid

• Relying solely on plain radiographs to exclude osteomyelitis, as early bone infection may not show radiographic changes for 10-14 days
• Failing to obtain proper X-ray views (AP, lateral, and oblique) of the entire foot
• Delaying advanced imaging when clinical suspicion for osteomyelitis remains high despite negative X-rays
• Not considering the possibility of Charcot neuro-osteoarthropathy, which can mimic infection on imaging

By following this evidence-based imaging approach, clinicians can optimize the diagnosis and management of severe diabetic foot infections, potentially reducing morbidity and mortality associated with these serious complications.