MRI Indications in Chronic Osteomyelitis

Initial Evaluation

The American College of Radiology recommends plain radiographs as the first imaging modality in suspected chronic osteomyelitis, but they have limited sensitivity in early disease and should not be the sole imaging modality 1, 4
Radiographic findings in chronic osteomyelitis include bone sclerosis and areas of destruction, but these changes may take weeks to develop 1, 2

MRI should be requested when radiographs are negative or inconclusive but clinical suspicion remains high 2, 3
The presence of a draining sinus tract is highly suggestive of underlying chronic osteomyelitis and MRI is superior for detecting the connection between the sinus tract and bone involvement 3, 5
MRI is indicated to evaluate the extent of bone and soft tissue involvement before surgical intervention 2, 4
MRI is useful when planning debridement to accurately define the margins of infected bone 3, 6
MRI can differentiate between soft tissue infection and bone involvement when clinical assessment is unclear 4

MRI has high sensitivity and specificity for chronic osteomyelitis, with superior ability to detect soft tissue and marrow edema 1, 2
MRI can accurately detect alterations in tissue perfusion 2, 3
MRI can identify cortical erosions with high interobserver agreement 2, 4
MRI can detect the presence of abscesses and fistulae 3, 5

In the post-surgical or post-traumatic setting, MRI remains sensitive but interpretation is more challenging due to marrow signal heterogeneity from prior trauma or surgery 1, 2
The presence of hardware can limit MRI evaluation, though modern sequences can reduce these artifacts 3, 7

In cases where MRI is contraindicated or unavailable, CT can be considered as it shows cortical thickening, destruction, and fistulae, though it is less sensitive than MRI 1, 3
FDG-PET may be particularly useful when hardware is present, with reported sensitivity of 94% and specificity of 87% in chronic post-traumatic osteomyelitis 3, 7
Bone scintigraphy has reasonable sensitivity (82%) but poor specificity (25%) in chronic osteomyelitis 3

Initial plain radiographs should be performed for all patients 1, 4
If radiographs are negative but clinical suspicion persists, proceed to MRI 2, 4
If MRI is inconclusive or contraindicated, consider CT or nuclear medicine studies 3, 7
When diagnosis remains uncertain after imaging, bone biopsy should be considered for definitive diagnosis 6, 7

Relying solely on radiographs for diagnosis, as they may be normal in early disease 1, 4
Misinterpreting post-surgical or post-traumatic changes as infection on MRI 1, 2
Failing to obtain contrast-enhanced MRI when evaluating soft tissue involvement 2, 4