Is an ultrasound (US) or X-ray better for diagnosing a suspected bicep rupture in the arm?

Ultrasound vs X-ray for Biceps Rupture in the Arm

Ultrasound is the appropriate first-line imaging choice for suspected biceps tendon rupture, with MRI being the gold standard if ultrasound results are inconclusive or surgical planning is needed. X-ray has limited utility for soft tissue injuries like biceps ruptures 1, 2.

Diagnostic Imaging Algorithm for Biceps Rupture

1. Initial Assessment:

   • Plain radiographs (X-rays) should be obtained first only to rule out associated fractures or bony abnormalities 2
   • X-rays alone cannot diagnose biceps tendon ruptures as they only visualize bone, not soft tissue

2. Primary Diagnostic Imaging:

   • Ultrasound: Recommended as a practical first-line imaging option
     • Advantages:
       • Non-invasive, readily available, cost-effective
       • Can be performed dynamically to assess tendon integrity
       • Excellent for detecting complete ruptures of distal biceps tendon 1
       • Can identify both complete and partial tears with proper technique 1
     • Limitations:
       • Operator-dependent
       • Lower sensitivity (62.5%) and specificity (20.0%) compared to MRI 2
       • Less reliable for detecting partial tears and tendinopathy 1

3. Advanced Imaging:

   • MRI without contrast: Gold standard for definitive assessment
     • Indicated when:
       • Ultrasound results are inconclusive
       • Surgical intervention is being considered
       • Need to differentiate between partial and complete tears
     • Advantages:
       • Superior sensitivity (76%) and specificity (50%) for biceps tendon tears 1
       • More accurate at correctly identifying the type of distal biceps tendon tear 1
       • Better enables precise surgical planning 2

Clinical Pearls

• Physical examination findings such as a palpable and visible deformity of the distal biceps muscle belly with weakness in flexion and supination are highly suggestive of biceps rupture 3
• The ability to palpate the tendon in the antecubital fossa may indicate partial tearing rather than complete rupture 3
• Point-of-care ultrasound performed by experienced clinicians can expedite diagnosis in the emergency setting 4

Common Pitfalls to Avoid

• Relying solely on X-rays for diagnosis of biceps rupture will miss the injury entirely, as X-rays only visualize bone, not soft tissue
• Failing to distinguish between partial (>50% vs <50%) and complete tears, which impacts treatment decisions 5
• Not considering the medial imaging approach for ultrasound, which has shown substantial interreader agreement and is preferred by radiologists 1
• Delaying diagnosis and appropriate treatment, which may lead to suboptimal outcomes, especially for complete tears where early surgical reattachment is recommended 3

In conclusion, while X-rays should be performed initially to rule out fractures, ultrasound is the appropriate first-line imaging modality for suspected biceps rupture, with MRI reserved for cases requiring definitive assessment or surgical planning.