ARRS 2022 Abstracts

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E1550. Pectoralis Major Muscle and Tendon Tear Evaluation Using Magnetic Resonance Imaging: Clinically Relevant Points Using a Case-Based Approach
Authors
  1. Jennifer Padwal; Stanford University
  2. Christopher Beaulieu; Stanford University
  3. Geoffrey Riley; Stanford University
Background
Pectoralis major tears have recently become more prevalent given the increase in extreme weight-training and high-energy sports. Advanced imaging is necessary to specifically localize and grade pectoralis tears, especially if surgery is being considered. The complex anatomy of the pectoralis muscle and tendon makes imaging and diagnosis of injuries particularly challenging. Full-thickness tendon tears/avulsions often undergo surgery, whereas lesser-grade injuries are usually treated conservatively. As such, it is imperative that radiologists accurately recognize and describe pectoralis myotendinous injuries.

Educational Goals / Teaching Points
Based on this review, attendees will understand the anatomy of the pectoralis major including muscle segments, tendons, innervation, and vasculature. Reviewers will be able to apply an optimized MRI protocol for imaging pectoralis tears and will be able to describe critical findings using surgically relevant grading schemes. Using 15 patient cases, we will review the MRI findings of common pectoralis major injuries, imaging protocols, and relevant report descriptors. Findings on MRI are correlated with each patient’s clinical course and any pertinent surgical findings.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The objectives of exhibit are as follows. 1) Review anatomy of the pectoralis major including:i) origin (clavicular and sternocostal heads); ii) insertion (lateral lip of the intertubercular sulcus of the proximal humerus, with discussion of the ‘newer’ understanding of bilaminar “U” shaped distal pectoralis major tendon); iii) function (internal rotation and adduction of the shoulder, flexion of the extended arm, dynamic stabilization of the shoulder); iv) nervous innervation (medial and lateral pectoral nerves); and v) vascular supply (pectoral artery and vein). 2) Review MRI protocol tips. 3. Review pectoralis injury grading, i.e., Tietjen classification: i) type I injury – muscle contusion or sprain; ii) type II injury – partial tear; and iii) type III – complete tear, which is further subdivided based on location (muscle origin, muscle body, musculotendinous junction, muscle tendon). 4. Review key findings to include in the report: location, acuity, extent of tear, and amount of tendon retraction. 5. Discuss treatment considerations: injury severity and acuity, patient activity level, and operative versus nonoperative management. 6. Review cases with follow-up documentation and take home points.

Conclusion
The outcome of intervention for pectoralis injury can be significantly impacted by prompt diagnosis and treatment. Given the importance of imaging in pectoralis injury, understanding the complex anatomy of the pectoralis muscle and injury classification using MRI is vital for the practicing radiologist to ensure optimal return to function.