CT for Osteomyelitis: With Contrast is Preferred When CT is Necessary
When CT is used for suspected osteomyelitis, CT with intravenous contrast is preferred over CT without contrast, though MRI remains the superior imaging modality and CT should only be used when MRI is contraindicated or unavailable. 1, 2
Primary Recommendation: MRI First, CT Second
- MRI without and with IV contrast is the gold standard imaging modality for osteomyelitis with sensitivity of 82-100% and specificity of 75-96%, far superior to CT. 2, 3
- Plain radiographs should always be obtained first, but have limited sensitivity for early osteomyelitis. 1, 2, 3
- CT should only be considered when MRI is contraindicated (pacemakers, certain implants, claustrophobia) or when extensive metal artifact from hardware makes MRI non-diagnostic. 1
When CT is Used: Contrast vs. Non-Contrast
CT with IV contrast (rating 6-7) is preferred over CT without contrast (rating 5-6) across multiple clinical scenarios:
For Suspected Osteomyelitis with Cellulitis/Wound
- CT with IV contrast receives a rating of 7 ("usually appropriate") when MRI is contraindicated. 1
- CT without IV contrast receives a lower rating of 5 ("may be appropriate"). 1
- Contrast significantly improves evaluation of associated soft tissue infections and abscess formation, which commonly accompany osteomyelitis. 2
For Hardware-Associated Infection
- CT with IV contrast (rating 7) is the preferred alternative when metal hardware causes extensive MRI artifact. 1
- CT without IV contrast receives only a rating of 5 in this scenario. 1
- Contrast helps evaluate hardware complications and developing osteolysis around implants. 2
For Draining Sinus Tracts
- Both CT with contrast and CT without contrast receive equal ratings of 6 ("may be appropriate") when MRI cannot be performed. 1
- However, contrast provides better soft tissue detail for tracking sinus tract extent. 2
Why Contrast Matters in CT
- IV contrast does not improve detection of acute osteomyelitis itself, but significantly enhances evaluation of soft tissue involvement, abscess formation, and extent of infection. 2
- Contrast helps identify sequestrum (dead bone fragments) in chronic osteomyelitis by showing the surrounding inflammatory tissue. 2
- Soft tissue abscesses and phlegmon are better delineated with contrast, which impacts surgical planning. 2
Important Caveats
CT Limitations
- CT has lower sensitivity than MRI for detecting early bone marrow changes in acute osteomyelitis. 2, 4, 5
- CT is most useful for characterizing osseous changes in chronic osteomyelitis, particularly sequestrum detection. 2
- Radiation exposure is a significant concern, especially in pediatric patients where MRI is strongly preferred. 2
When to Avoid Contrast
- For foreign body detection, CT without contrast (rating 7) is preferred over CT with contrast (rating 6) because contrast may obscure identification of the foreign body. 1
- When contrast is contraindicated (renal insufficiency, severe contrast allergy), CT without contrast is acceptable though less optimal. 2
CT Without and With Contrast is NOT Recommended
- CT without and with contrast (dual-phase) receives a rating of only 1 ("usually not appropriate") for osteomyelitis evaluation across all clinical scenarios. 1
- The additional radiation exposure and time are not justified by any diagnostic benefit. 1
Clinical Algorithm
Start with plain radiographs to exclude alternative diagnoses and assess for chronic changes. 1, 2, 3
Proceed to MRI without and with IV contrast if osteomyelitis is suspected and radiographs are normal or inconclusive. 2, 3
Use CT with IV contrast only if:
Exception: Use CT without contrast when evaluating for radiopaque foreign bodies. 1
Consider nuclear medicine studies (labeled leukocyte scan with sulfur colloid) if both MRI and CT are inadequate, particularly with extensive hardware. 1