What is the best type of MRI (Magnetic Resonance Imaging) to evaluate the shoulder for a pectoralis tendon injury?

Best MRI Type for Pectoralis Tendon Injury

For evaluating pectoralis tendon injury, standard MRI without contrast is the appropriate initial imaging modality, though dedicated pectoralis-specific MRI sequences (not routine shoulder MRI) are preferred for complete assessment of injury location and severity.

Important Clinical Context

The pectoralis major tendon is not an intra-articular structure and therefore does not benefit from MR arthrography, which is specifically designed for intra-articular pathology like labral tears and partial rotator cuff tears 1. The guidelines provided focus on shoulder joint pathology (rotator cuff, labrum, glenohumeral ligament), not pectoralis major injuries, which occur anterior to the shoulder joint 1.

Recommended Imaging Approach

Standard MRI Without Contrast

• MRI without contrast is the gold standard for soft tissue injuries including pectoralis major tendon pathology 2
• Provides excellent visualization of the pectoralis tendon at all potential injury sites: humeral insertion (most common), myotendinous junction, intra-tendinous, and intramuscular locations 2
• Accurately identifies tear location and severity, which is critical for determining operative versus non-operative management 3, 2
• MRI findings correlate perfectly or near-perfectly with intraoperative findings in pectoralis major injuries 3

High-Resolution Ultrasound as Alternative

• Ultrasound is a valuable alternative when performed by experienced operators for evaluating pectoralis major injuries 2
• Particularly useful for dynamic assessment and can guide clinical management 2
• More operator-dependent than MRI but avoids invasive procedures and contrast administration 2

Key Imaging Features to Identify

The "Smoke Sign" on Routine Shoulder MRI

• If routine shoulder MRI is performed first, look for feathery soft tissue edema lateral or anterior to the short head biceps/coracobrachialis on fluid-sensitive sequences 4
• This sign has 100% sensitivity for humeral avulsions and complete tendon tears, 50% sensitivity for myotendinous junction injuries 4
• Detection of this sign should prompt dedicated pectoralis major imaging to confirm and fully characterize the injury 4

Critical Management Implications

Surgical Indications Require Accurate Imaging

• Operative management is recommended for:

  • Tears at the humeral insertion (most common) 2
  • Complete intra-tendinous tears 2
  • Myotendinous junction tears with severe cosmetic/functional deformity 2
  • Sternal head/posterior lamina tears 2

• Non-operative management may be appropriate for:

  • Intramuscular injuries 4, 2
  • Partial myotendinous junction injuries without significant deformity 2

Common Pitfalls to Avoid

• Do not order MR arthrography for suspected pectoralis major injury—it adds unnecessary invasiveness without diagnostic benefit since this is an extra-articular structure 1
• Routine shoulder MRI protocols may miss pectoralis injuries if sequences are not optimized for anterior chest wall structures 4
• Always evaluate the pectoralis major when reviewing shoulder MRI in athletes, particularly weight-lifters, as injuries can be overlooked 4, 3
• The inferior sternal head fibers are most commonly torn, so ensure imaging sequences adequately visualize this region 2