From the Guidelines
MRI without contrast can be used to diagnose osteomyelitis, although contrast-enhanced MRI is generally preferred for optimal evaluation. Non-contrast MRI can detect bone marrow edema, cortical destruction, soft tissue changes, and abscess formation associated with bone infection, with sensitivity ranging from 75-90% for osteomyelitis 1. The use of fluid-sensitive sequences, such as T2-weighted and STIR sequences, can demonstrate increased signal intensity due to inflammatory changes, while T1-weighted images show decreased signal intensity in infected areas.
Key Considerations
- The diagnosis of osteomyelitis can be challenging, especially in patients with underlying conditions such as sickle cell disease, where marrow infarction and osteomyelitis may present similarly 1.
- The presence of reactive bone marrow edema from non-infectious pathologies, such as trauma, previous foot surgery, or Charcot neuroarthropathy, can lower the specificity and positive predictive value of MRI findings 1.
- In selected patients, newer techniques such as MR angiography, dynamic contrast-enhanced MRI, or neurography may better distinguish Charcot arthropathy from osteomyelitis 1.
Diagnostic Approach
- MRI is widely regarded as sensitive and specific in the diagnosis of acute osteomyelitis, with sensitivity reportedly 82% to 100% and specificity 75% to 96% 1.
- The accuracy of MRI findings can be improved by using the results of a second read by an expert musculoskeletal radiologist 1.
- When osteomyelitis is suspected, physicians should communicate this concern to radiologists to ensure appropriate protocols are used, even when contrast cannot be administered.
- In patients with a contraindication to MRI, clinicians may choose other imaging techniques, such as FDG-PET/CT, HMPAO-labelled leucocyte scintigraphy, or 99mTc labelled Ubiquicidin (UBI) SPECT/CT 1.
From the Research
Diagnostic Accuracy of MRI without Contrast for Osteomyelitis
- The diagnostic accuracy of MRI without contrast for osteomyelitis has been evaluated in several studies 2, 3, 4, 5, 6.
- A systematic review found that MRI without gadolinium-based contrast has a 92% sensitivity, 89% specificity, and 96% overall diagnostic accuracy for diagnosing osteomyelitis in the appendicular skeleton 2.
- Another study found that MRI without contrast has a high sensitivity and specificity for detecting osteomyelitis, with a sensitivity of 100% and a specificity of 49.2% using STIR sequences, which increased to 79.7% and 83.1% when combined with T1 SE images and contrast-enhanced images, respectively 6.
- The use of MRI without contrast is recommended as the next most appropriate study after radiographs for routine cases of suspected non-spinal osteomyelitis 2.
Comparison with Contrast-Enhanced MRI
- A study compared the diagnostic accuracy of MRI with and without gadolinium-based contrast for osteomyelitis and found that there was no added diagnostic value of gadolinium contrast for the diagnosis of osteomyelitis in the appendicular skeleton 2.
- Another study found that the sensitivity and specificity of MRI with contrast were 90% and 80%, respectively, while the sensitivity and specificity of MRI without contrast were not reported 4.
Clinical Risk Indicators and MRI Findings
- Clinical risk indicators such as diabetes, and MRI findings such as confluent signal on T1-weighted images and cortical erosion, have been identified as independent risk factors for osteomyelitis 4.
- The presence of these risk factors and MRI findings can increase the suspicion of osteomyelitis and guide further diagnostic and therapeutic management.