What is the best imaging modality for evaluating the pectoralis major (pec major) tendon and muscles?

Imaging for Pectoralis Major Tendon and Muscle Evaluation

MRI without contrast is the imaging modality of choice for evaluating pectoralis major tendon and muscle injuries, providing superior accuracy in distinguishing complete tears requiring surgery from partial injuries that can be managed conservatively. 1, 2, 3

Initial Imaging Approach

• Radiographs are not useful for evaluating pectoralis major soft tissue injuries, as they cannot visualize muscle or tendon pathology 4
• Proceed directly to MRI when pectoralis major injury is clinically suspected based on mechanism (typically weightlifting/bench pressing) and physical examination findings 1, 2

MRI as the Gold Standard

Diagnostic Accuracy

• MRI demonstrates 100% sensitivity for complete (Grade 3) tears at both the sternal and clavicular heads in acute injuries 5
• MRI shows 93% sensitivity for tendon-bone junction tears at the sternal head and 90% at the clavicular head 5
• Surgical correlation confirms MRI accuracy in detecting and grading pectoralis major tears, with agreement in all cases in multiple studies 1, 2

Critical MRI Findings to Assess

• Absence of visible tendon at the humeral insertion (sensitivity 82-100%, specificity 100%) is the most reliable primary sign of tendon avulsion requiring surgery 6
• Soft tissue edema contacting the anterior humeral cortex (sensitivity 64-91%, specificity 67-100%) is a useful secondary sign distinguishing tendon avulsion from myotendinous injury 6
• Location of injury: tendon-bone junction (humeral insertion) versus myotendinous junction versus intramuscular 1, 2, 3
• Degree of tearing: complete (Grade 3) versus partial (Grade 2) 2, 5
• Amount of tendon retraction when present 1, 2
• Which head is involved: sternal head (most common), clavicular head, or both 1, 2
• Acute versus chronic: acute tears show hemorrhage and edema, chronic tears show fibrosis and scarring 1

MRI Technical Specifications

• Use thin (3-4 mm) axial sections as the primary imaging plane 2
• Combine T1-weighted or proton density sequences for anatomical delineation with fluid-sensitive sequences (T2-weighted with fat suppression or STIR) for detecting edema and hemorrhage 2
• Intravenous contrast is not necessary for diagnosis 7

Ultrasound as an Alternative

• High-resolution ultrasound can accurately diagnose pectoralis major injuries and has value in guiding clinical and surgical management 3
• Ultrasound is operator-dependent and may be less comprehensive than MRI for evaluating deep structures and associated pathology 4, 7
• Consider ultrasound when MRI is contraindicated or unavailable, particularly in experienced hands 7, 3

CT Has No Role

• CT has virtually no usefulness in diagnosing pectoralis major muscle and tendon injuries, as it is inferior for soft tissue evaluation 4
• CT should not be used for this indication 4

Clinical Decision-Making Based on MRI

Surgical Indications (Based on MRI Findings)

• Complete tears at the humeral insertion (tendon-bone junction) require surgical repair 1, 2, 3
• Myotendinous junction tears with severe retraction causing significant cosmetic or functional deformity warrant surgery 3
• Complete intra-tendinous tears (mid-tendon substance) are now considered surgical candidates 3
• Complete tears at the sternal head/posterior lamina may require operative management 3

Conservative Management (Based on MRI Findings)

• Partial tears at the myotendinous junction without significant retraction can be managed non-operatively 1, 2
• Intramuscular injuries typically heal with conservative treatment 2

Important Caveats

• MRI accuracy decreases for chronic tears compared to acute injuries, though it remains the best available imaging modality 5
• The retracted tendon stump and epicenter of edema are not reliable findings for distinguishing tendon avulsion from myotendinous injury 6
• Focus MRI interpretation on the humeral insertion and presence/absence of tendon at this location for the most accurate surgical planning 6
• Acute injuries (within weeks) are easier to characterize than chronic injuries due to clearer tissue planes and more obvious hemorrhage/edema 1, 5