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

MRI is Superior to Ultrasound for Diagnosing Biceps Tendon Tears

MRI without contrast is the preferred imaging modality for diagnosing biceps tendon tears, with significantly higher accuracy (86.4%) compared to ultrasound (45.5%) for complete distal biceps tears. 1, 2, 3

Initial Imaging Approach

• Plain radiographs should be obtained first to exclude associated fractures or other bony abnormalities before proceeding to advanced imaging 1, 2, 4
• After negative or non-diagnostic radiographs, proceed directly to MRI for suspected biceps tendon pathology 1, 2

MRI Performance Characteristics

For complete distal biceps tears:

• Sensitivity: 100% 5
• Specificity: 82.8% 5
• Overall accuracy: 86.4% 1, 3
• MRI demonstrates 100% agreement with surgical findings 6

For partial biceps tears:

• Sensitivity: 59.1% 5
• Specificity: 100% 5
• Accuracy: 66.7% 3
• Critical limitation: MRI significantly underreports high-grade partial tears (>50%), with sensitivity of only 44% for these injuries 7

Optimal MRI technique:

• Use the FABS (flexion-abduction-supination) view for best visualization of the distal biceps tendon 1, 2, 4
• Axial images are more valuable than sagittal images for accurately grading the severity of injury 6
• MRI has high inter- and intraobserver reliability with sensitivity of 92.4% and specificity of 100% for detecting distal biceps ruptures overall 8, 5

Ultrasound Performance Characteristics

For complete distal biceps tears:

• Sensitivity: 62.5% 3
• Specificity: 20.0% 3
• Overall accuracy: 45.5% 1, 3

For partial tears:

• Accuracy: 66.7% (equivalent to MRI) 3
• However, ultrasound has substantial limitations in detecting partial tearing and tendinopathy 1, 2

When ultrasound may be considered:

• Ultrasound performs similar to or slightly better than MRI specifically for differentiating complete versus partial distal biceps tears, with reported 95% sensitivity, 71% specificity, and 91% accuracy 8
• Use only when MRI is contraindicated (e.g., pacemaker, severe claustrophobia, metallic implants) 1, 2
• More cost-effective than MRI but at the expense of diagnostic accuracy 3
• Recent advanced techniques (sonoelastography, superb microvascular imaging) show improved performance but are not yet standard practice 8

Critical Pitfalls to Avoid

Do not rely solely on ultrasound for diagnosis as it has significantly lower accuracy compared to MRI, particularly for complete tears 1, 2, 4

Be aware that MRI commonly misses high-grade partial tears (>50%), especially in patients with insidious onset of symptoms rather than acute traumatic injury 7

MRI is less likely to detect high-grade tears in atraumatic presentations (27% detection rate) compared to traumatic onset (55% detection rate), despite similar injury severity at surgery 7

The time from symptom onset to imaging does not affect MRI accuracy, so delayed imaging is not problematic 7

Additional Diagnostic Considerations

• MRI has the added benefit of demonstrating associated soft tissue injuries including rotator cuff tears, pulley lesions, and SLAP lesions 1
• MR arthrography does not add additional diagnostic value compared to non-contrast MRI for biceps tendon tears 8
• MR arthrography may be considered when distinction between full-thickness and partial-thickness tears remains unclear after standard MRI 1

Clinical Algorithm

1. Obtain plain radiographs first 1, 2, 4
2. Proceed to MRI without contrast using FABS view 1, 2, 4
3. If MRI is contraindicated, use ultrasound as second-line alternative 1, 2
4. If clinical suspicion remains high despite negative or equivocal MRI (particularly in insidious onset cases), consider surgical exploration as MRI sensitivity for high-grade partial tears is only 44% 7