What is the protocol for ordering an MRI for a suspected pectoralis major tear?

MRI Protocol for Suspected Pectoralis Major Tear

For a suspected pectoralis major tear, MRI without contrast is the most appropriate imaging study to order after initial radiographs.

Diagnostic Approach

1. Initial Evaluation:

   • Begin with standard radiographs of the shoulder/chest to rule out bony avulsion or other osseous abnormalities
   • Proceed to MRI without contrast as the definitive diagnostic test

2. MRI Protocol Specifications:

   • Type: MRI without IV contrast
   • Field of View: Include the entire pectoralis major muscle from origin to insertion
   • Sequences:
     • Axial T1-weighted images (best for chronic injuries)
     • Axial T2-weighted images (most valuable for acute/subacute injuries)
     • Coronal and sagittal T1 and T2-weighted images

Evidence-Based Rationale

MRI is superior to other imaging modalities for pectoralis major tears because:

• MRI provides detailed visualization of the musculotendinous junction and humeral insertion point where tears commonly occur 1, 2
• MRI can accurately determine the location (humeral insertion vs. musculotendinous junction) and grade of injury, which directly impacts treatment decisions 3
• Axial T2-weighted images are particularly valuable for evaluating acute and subacute injuries, while T1-weighted images better delineate chronic injuries 4

Clinical Correlation

The American College of Radiology guidelines support the use of MRI without contrast for evaluation of soft tissue injuries:

• MRI is the preferred modality for evaluating suspected rotator cuff tears and other soft-tissue abnormalities in the shoulder region 5
• MRI provides superior tissue contrast resolution compared to CT for soft tissue injuries 5

Common Pitfalls to Avoid

1. Relying solely on clinical examination: Clinical impression often overestimates the severity, location, and grade of pectoralis major tears 3

2. Ordering CT instead of MRI: CT is inferior to MRI for direct visualization of muscle rupture 4

3. Using contrast unnecessarily: IV contrast does not typically improve evaluation of muscle tears 5

4. Inadequate imaging field: Ensure the entire pectoralis major muscle is included in the field of view

By following this protocol, you'll obtain the most accurate diagnostic information to guide appropriate treatment decisions for patients with suspected pectoralis major tears.