MRI Shoulder Without IV Contrast
For suspected glenohumeral osteomyelitis, order an MRI of the shoulder without IV contrast 1. This is the most accurate imaging modality for detecting acute osteomyelitis, with high sensitivity and specificity for identifying bone marrow signal changes and associated soft tissue complications.
Imaging Algorithm
Start with plain radiographs of the shoulder as the initial study 2. While radiographs are usually the first step for any shoulder pathology, they are often normal or nonspecific in early osteomyelitis.
When radiographs are normal or nonspecific and osteomyelitis is suspected, proceed directly to MRI shoulder without IV contrast 1. This provides:
- Excellent detection of marrow signal abnormalities characteristic of acute osteomyelitis
- Superior soft tissue evaluation including abscess formation, fistulas, and adjacent muscle involvement 1
- High diagnostic accuracy without requiring gadolinium contrast for osteomyelitis diagnosis 1
Key MRI Findings to Identify
Look for these specific features on MRI:
- Confluent high signal intensity on T2-weighted images in the bone marrow (present in essentially all cases) 3
- Confluent low signal intensity on T1-weighted images (present in 96% of cases) 3
- Multiple foci of marrow involvement with irregular contours 3
- Osteochondral erosion at the glenohumeral joint 4
- Associated soft tissue findings: synovitis, bursitis, muscle edema, or abscess formation 4
Critical Clinical Point
Osteomyelitis on MRI is the strongest predictor of treatment failure and recurrent septic arthritis 4. In a multivariable analysis controlling for clinical and laboratory parameters, osteomyelitis on preoperative MRI was the only significant predictor of recurrent septic shoulder arthritis (p = 0.02), making accurate MRI diagnosis crucial for prognosis and treatment planning.
Contrast Administration
IV gadolinium contrast is NOT necessary for diagnosing peripheral osteomyelitis 1. While contrast may improve evaluation of soft tissue infections like abscesses, it does not improve the diagnosis of osteomyelitis itself. The noncontrast sequences are sufficient for identifying the characteristic marrow signal abnormalities.
Common Pitfall
Do not order MRI with and without contrast or MR arthrography for suspected osteomyelitis—these add no diagnostic value and increase cost and scan time 1. The ACR Appropriateness Criteria specifically note no relevant literature supporting their use for infection evaluation 2.
Alternative Imaging (When MRI Contraindicated)
If MRI is contraindicated, consider 3-phase bone scan or FDG-PET/CT, though these have lower specificity (45% for bone scan) 1. CT has limited sensitivity for acute osteomyelitis and is primarily useful for chronic disease with sequestrum formation 1.