What imaging is required to diagnose a pectoralis major (pec major) or biceps tendon tear?

Imaging for Pectoralis Major or Biceps Tendon Tear

Ultrasound should be used as first-line imaging for suspected pectoralis major or biceps tendon tears, followed by MRI without contrast when ultrasound is inconclusive or surgery is being considered. 1

Diagnostic Imaging Algorithm

Initial Imaging

1. Plain Radiographs (X-rays)

   • First-line imaging for all acute arm pain
   • Helps exclude fractures, dislocations, and bony abnormalities
   • Can identify joint effusions and avulsion fractures at tendon attachment sites 1

2. Ultrasound

   • Recommended first-line specific imaging for suspected tendon rupture
   • Advantages:
     • Non-invasive and readily available
     • Cost-effective
     • High diagnostic accuracy (sensitivity 95%, specificity 71% for complete vs. partial tears) 1
   • Particularly useful for real-time dynamic assessment of tendon integrity

Advanced Imaging

1. MRI without contrast
   • Indicated when:
     • Ultrasound is inconclusive
     • Surgery is being considered
     • Need for detailed assessment of associated injuries 1
   • Superior for:
     • Definitive assessment of tear location and extent
     • More accurate identification of tear type
     • Better visualization of associated injuries
   • Diagnostic accuracy: sensitivity 76%, specificity 50% 1
   • Axial MR images are particularly valuable for accurate grading of distal biceps tendon injuries 2

Key Imaging Findings

Pectoralis Major Tears

• MRI can accurately detect and grade tears involving the pectoralis major muscle and tendon 3
• Important findings:
  • Location of tear (myotendinous junction vs. enthesis/humeral insertion)
  • Extent of tear (partial vs. complete)
  • Associated injuries 3, 4
• Ancillary findings that suggest more severe tears:
  • Anterior biceps tendon displacement >4.5mm (86% sensitivity, 75% specificity for full-thickness tears)
  • Presence of peri-bicipital hematoma (strongest predictor of full-thickness complete tears) 5

Biceps Tendon Tears

• MRI evaluation should include:
  • Axial images of the distal biceps insertion (critical for accurate grading) 2
  • Assessment of tear location (distal insertion vs. proximal long head)
  • Evaluation for entrapment or displacement 6
• Ultrasound can effectively visualize the tendon and assess for discontinuity or retraction 1, 4

Clinical Pearls and Pitfalls

• Diagnostic Pitfall: Ruptured long head of biceps tendon can sometimes mimic a pectoralis major rupture, especially when there is entrapment of the distal segment under the pectoralis major insertion 6

• Imaging Impact: MRI findings can significantly alter treatment plans. In one study, MRI findings led to changes in clinical treatment plans in 38% of patients with suspected distal biceps tendon injury 2

• Radiation Consideration: When using X-rays, particularly in pediatric patients, the lowest dose protocols should be employed due to radiation exposure risks 1

• Timing Consideration: Early and accurate imaging is crucial as delayed diagnosis may lead to suboptimal outcomes, especially for complete tears where early surgical reattachment is recommended 1