What MRI sequences should be ordered for a pectoralis major evaluation?

MRI Protocol for Pectoralis Major Evaluation

For optimal evaluation of pectoralis major injuries, a dedicated MRI protocol should include high-resolution T1-weighted, T2-weighted with fat suppression, and STIR sequences in multiple planes, with particular attention to axial images through the musculotendinous junction and humeral insertion.

Recommended MRI Protocol

Core Sequences:

• T1-weighted sequences:

  • Axial plane (primary plane for evaluation)
  • Sagittal plane
  • Coronal plane
  • Purpose: Anatomical delineation and visualization of chronic injuries 1

• T2-weighted sequences with fat suppression:

  • Axial plane (most valuable for acute/subacute injuries)
  • Sagittal plane
  • Coronal plane
  • Purpose: Detection of edema, hemorrhage, and fluid collections 2, 1

• STIR (Short Tau Inversion Recovery) sequences:

  • Axial plane
  • Purpose: Enhanced visualization of edema and inflammation 1

Technical Considerations:

• Thin slice thickness (3-4 mm) for optimal detail 1
• Field of view should include the entire pectoralis muscle from origin to insertion
• Patient positioning: Supine with arm at side in neutral position
• Imaging should be performed at 1.5T or 3T (1.5T may be preferred if metal is present to reduce artifact) 3

Anatomical Focus Areas

The MRI should specifically evaluate:

1. Humeral insertion site - Most common location for tears 4
2. Musculotendinous junction - Second most common injury site 5
3. Muscle belly - To assess for intramuscular tears or hematomas
4. Sternal and clavicular heads - Both components should be assessed separately 5

Clinical Relevance

MRI findings directly impact treatment decisions:

• Complete tears at the humeral insertion typically require surgical repair
• Partial tears may be managed conservatively
• The degree of tendon retraction influences surgical planning 5

Common Pitfalls to Avoid

1. Inadequate coverage: Ensure the entire pectoralis major muscle and tendon are included in the field of view
2. Suboptimal sequences: Axial T2-weighted images with fat suppression are crucial for acute injuries, while T1-weighted images are better for chronic injuries 2
3. Misinterpretation of normal anatomy: The complex insertion of the pectoralis major can be misinterpreted as pathology
4. Missing associated injuries: Evaluate for concomitant injuries to the long head of biceps tendon and anterior labrum

MRI is the gold standard imaging modality for pectoralis major injuries 6, providing superior soft tissue contrast and multiplanar capabilities that allow accurate assessment of tear location, extent, and chronicity to guide appropriate management.