What is the preferred imaging modality, MRI (Magnetic Resonance Imaging) or US (Ultrasound), for diagnosing a biceps tear?

Biceps Tear Diagnosis: MRI vs Ultrasound

Both MRI and ultrasound are effective for diagnosing biceps tendon tears, but MRI is the superior imaging modality with higher overall accuracy (80.6% vs 51.6%), particularly for distinguishing between partial and complete tears. 1, 2

Imaging Algorithm

First-Line Imaging

• Plain radiographs should be obtained initially to exclude fractures and bony abnormalities before proceeding to advanced imaging 1, 3

Definitive Imaging Choice

For Distal Biceps Tendon Tears:

• MRI without contrast is the preferred modality with 86.4% accuracy for complete tears compared to ultrasound's 45.5% accuracy 1, 2
• MRI demonstrates superior sensitivity (76%) and specificity (50%) compared to ultrasound for all biceps tendon pathology 1
• The FABS view (flexion-abduction-supination) should be specifically requested for optimal distal biceps visualization on MRI 1, 3

For Proximal Long Head of Biceps Tendon (LHBT) Tears:

• MRI is strongly preferred because proximal biceps lesions are hidden under the acromion, making ultrasound assessment difficult 4
• MRI shows high specificity (93-99%) for complete LHBT tears, though sensitivity is more variable (55.9-90%) 5
• For partial tears/tendinosis of the LHBT, MRI has moderate sensitivity (67.8%) and specificity (75.9%), making diagnosis challenging even with MRI 5

Performance Characteristics by Tear Type

Complete Tears:

• MRI: 92.4% sensitivity, 100% specificity for distal biceps 6, 7
• Ultrasound: 95% sensitivity, 71% specificity, 91% accuracy 6
• Both modalities perform well, with ultrasound performing "similar to slightly better" than MRI for complete distal biceps tears 6

Partial Tears:

• MRI: 59.1% sensitivity, 100% specificity for distal biceps 6, 7
• MRI: 66.7% accuracy for partial distal biceps tears 2
• Ultrasound has significantly lower accuracy for partial tears 1, 3
• This is where MRI's superiority becomes most clinically relevant 1, 2

When to Consider Ultrasound

Ultrasound can be used as an alternative when:

• MRI is contraindicated (pacemakers, severe claustrophobia, metallic implants) 1, 3
• As a screening tool in older patients with suspected complete tears where clinical suspicion is high 6
• Cost considerations are paramount and complete tear is strongly suspected clinically 2

However, maintain a low threshold for proceeding to MRI if ultrasound is noncontributory 6

Critical Pitfalls to Avoid

• Do not rely solely on ultrasound when distinguishing partial from complete tears is clinically important for surgical planning 1, 3
• Do not use MR arthrography for biceps tendon tears—it adds no additional diagnostic information compared to noncontrast MRI 6
• Do not miss associated pathology: MRI better demonstrates concomitant rotator cuff tears, labral pathology, and ligamentous injuries that may influence treatment 6, 4
• Ultrasound has poor penetration through bone and cannot adequately assess proximal biceps pathology under the acromion 6, 4

Surgical Planning Considerations

MRI facilitates superior surgical planning by:

• Accurately differentiating partial from complete tears (critical for operative decision-making) 1, 3
• Identifying associated soft tissue injuries including rotator cuff tears and UCL injuries 6
• Demonstrating the extent of tendon retraction in complete tears 7