Understanding "Acetabular Labrum Within Normal Limits on Non-Arthrographic MRI"
This statement means the radiologist did not identify an obvious labral tear on your standard MRI, but this finding has significant limitations and does NOT reliably exclude a labral tear as the cause of your hip pain. 1
Critical Limitation of Non-Arthrographic MRI
Standard MRI without intra-articular contrast has substantially reduced accuracy for detecting labral tears compared to MR arthrography (direct injection of contrast into the joint). The ACR Appropriateness Criteria clearly establish that:
- MR arthrography is superior to non-contrast MRI for evaluating labral tears in the overall published data 1
- Non-contrast MRI has a sensitivity of only 30-80% for detecting labral tears (meaning it misses 20-70% of tears that are actually present) 2, 3, 4
- MR arthrography has 90-95% sensitivity and 88-91% accuracy for labral tears 3, 4
What This Means for Your Clinical Situation
If you have persistent hip pain with clinical findings suggestive of a labral tear (such as a positive FADIR/impingement test), a "normal" non-arthrographic MRI should NOT be considered definitive. 1, 5
Next Steps Based on Clinical Suspicion:
- If labral tear remains clinically suspected: Proceed to MR arthrography (rated 9/9 "usually appropriate" by ACR) for definitive evaluation 1, 5
- Alternative diagnostic/therapeutic option: Consider a diagnostic intra-articular anesthetic injection - if this temporarily relieves your pain, it confirms an intra-articular source (such as labral tear) even if imaging appears normal 1
- High-resolution 3 Tesla MRI may improve visualization in some cases, though arthrography remains the gold standard 1
Why Non-Arthrographic MRI Misses Labral Tears
The technical limitations include 1, 6:
- Thick overlying soft tissues decrease spatial and contrast resolution
- Inability to distinguish the labrum from adjacent subchondral bone, articular cartilage, and joint capsule without contrast
- No joint distension - arthrography separates structures and outlines abnormalities that are otherwise invisible
Important Clinical Caveat
Some investigators have reported satisfactory results detecting labral tears with high-resolution non-contrast MRI at 1.5T or 3T 1, 2, with one study showing 94-95% sensitivity for labral tears using optimized protocols 2. However, this requires specialized protocols and experienced musculoskeletal radiologists - and even then, MR arthrography remains more reliable overall 1.
Bottom Line for Clinical Decision-Making
Do not let a "normal" non-arthrographic MRI dissuade you from pursuing MR arthrography if clinical suspicion for labral tear remains high based on your symptoms and physical examination findings. 1, 5 The diagnosis should integrate clinical examination, imaging findings, and patient symptoms - never rely on imaging alone 7.