MR Arthrography for Suspected Hip Labral Tears
What is MR Arthrography?
MR arthrography is a specialized MRI technique involving direct intra-articular injection of dilute gadolinium contrast (1:200 gadolinium chelate in saline) into the hip joint, which has been established as the gold standard imaging modality for diagnosing acetabular labral tears. 1, 2, 3
The technique works by distending the joint capsule and creating high contrast between the articular surfaces and the injected contrast agent, allowing superior visualization of defects in the labrum, articular cartilage, and joint capsule. 1
Diagnostic Performance
Superior Accuracy for Labral Tears
- MR arthrography demonstrates 92-100% sensitivity for detecting labral tears, vastly superior to conventional MRI (8-25% sensitivity with large field of view, 85% with optimal technique). 4, 5
- Overall published data confirms MR arthrography is superior to both CT arthrography and noncontrast MRI for evaluating labral tears. 1
- The American College of Radiology rates direct MR arthrography as 9/9 (usually appropriate) for suspected labral tears, compared to only 6/9 for standard MRI without arthrography. 2, 3
Diagnostic Criteria on MR Arthrography
Labral tears are diagnosed when imaging demonstrates: 6, 7
- Contrast material tracking at the acetabular-labral junction
- Intrasubstance contrast extension within the labrum
- Labral blunting, absence, or displacement
- Irregular labral remnants or paralabral cysts
Clinical Algorithm for Use
When to Order MR Arthrography
After obtaining initial radiographs (which should always be first), proceed to MR arthrography when: 1
- Radiographs are negative, equivocal, or nondiagnostic AND
- Clinical suspicion for labral tear exists (positive FADIR test, mechanical symptoms, hip pain in young active adults) AND
- Definitive diagnosis is needed to guide surgical decision-making
Alternative Imaging Options
While MR arthrography remains the gold standard, consider these alternatives: 1
- High-resolution 3 Tesla MRI without arthrography may provide adequate labral visualization in some cases, potentially obviating the need for intra-articular contrast 1
- CT arthrography (rated 7/9 by ACR) is an alternative if MRI is contraindicated, though it shows inferior sensitivity for labral tears (15% in one study) 2, 8
- Indirect MR arthrography (IV gadolinium with exercise allowing synovial diffusion into joint) is faster and easier but suffers from less consistent joint enhancement and inability to distend the capsule 1, 5
Additional Diagnostic Benefits
Beyond labral tear detection, MR arthrography provides: 1
- Effective assessment of acetabular cartilage delamination 1
- Visualization of associated femoroacetabular impingement (FAI) features 1
- Detection of capsular defects and intra-articular loose bodies 7
Important Caveats
Common pitfalls to avoid: 9
- Never diagnose labral tears based on imaging alone—always integrate clinical examination, patient symptoms, and imaging findings 9
- Incidental labral tears and chondral pathology are common in asymptomatic individuals 9
- A simultaneous intra-articular injection of anesthetic and steroid during the arthrography procedure provides both diagnostic confirmation (pain relief suggests intra-articular source) and therapeutic benefit 1
Technical Considerations
For optimal results: 4