What is the most accurate test to diagnose a hip labrum tear?

Diagnostic Testing for Hip Labral Tears

MR arthrography (magnetic resonance imaging with intra-articular gadolinium injection) is the gold standard test for diagnosing hip labral tears, with the American College of Radiology rating it 9/9 (usually appropriate) for this indication. 1, 2

Initial Diagnostic Approach

Start with plain radiographs to rule out fractures, dysplasia, femoroacetabular impingement, and degenerative changes before proceeding to advanced imaging. 3, 2 This is standard practice despite limited scientific evidence supporting this dogma. 3

The most consistent physical examination finding is a positive anterior impingement test (FADIR test), which has 100% specificity and 59% sensitivity for labral tears. 2, 4 If this test is positive, it reliably indicates a labral tear is present. 4

Definitive Imaging: MR Arthrography vs Standard MRI

MR Arthrography Performance

• Sensitivity: 71-95% for detecting labral tears 5, 6
• Specificity: 84-85% 6
• Positive predictive value: 90-93% 5, 6
• Direct intra-articular injection of dilute gadolinium solution provides superior visualization by distending the joint and outlining labral defects 3, 1

Standard MRI Limitations

• Sensitivity: Only 30-80%, meaning it misses 20-70% of actual tears 7
• Rated only 6/9 (may be appropriate) by the American College of Radiology 1
• Cannot adequately distinguish the labrum from adjacent structures without joint distension 7
• One study showed conventional MRI with large field of view detected only 8% of labral tears confirmed at arthroscopy 8

A critical pitfall: A negative standard MRI should NOT exclude labral tear if clinical suspicion remains high based on symptoms and physical examination. 7 You must proceed to MR arthrography for definitive evaluation. 1, 7

Alternative Diagnostic Options

Ultrasound

• Sensitivity: 94% compared to MR arthrography in one study 4
• Can reliably diagnose most anterior acetabular labral tears 3, 4
• Useful if impingement test is negative but clinical suspicion persists 4
• User-dependent and best for superficial structures 3

CT Arthrography

• Rated 7/9 (usually appropriate) by the American College of Radiology 1
• Alternative when MRI is contraindicated 1, 2

Diagnostic Intra-articular Injection

• Injection of anesthetic with or without corticosteroid can be both diagnostic and therapeutic 3, 1
• Pain relief after injection confirms intra-articular source 3, 7
• Should be image-guided 3

Clinical Algorithm

1. Obtain plain radiographs first in all cases to evaluate for structural abnormalities 3, 2
2. Perform FADIR impingement test: If positive (100% specificity), labral tear is highly likely 2, 4
3. If clinical suspicion is high, proceed directly to MR arthrography rather than standard MRI 1, 2, 7
4. If MR arthrography is contraindicated, consider CT arthrography 1 or ultrasound 4
5. If imaging is negative but symptoms persist, consider diagnostic intra-articular anesthetic injection 1, 7

The key caveat: Do not rely on standard non-contrast MRI to rule out labral tears. Its poor sensitivity means many tears will be missed, and you should proceed directly to MR arthrography when labral pathology is suspected. 7, 8, 6