MR Arthrogram for HAGL Lesion: Intraarticular Contrast is Required
For diagnosing a humeral avulsion of glenohumeral ligament (HAGL) lesion, direct MR arthrography with intraarticular contrast injection is the preferred imaging technique rather than intravenous contrast. 1
Rationale for Intraarticular Contrast
MR arthrography with direct intraarticular injection of contrast provides several advantages for HAGL lesion diagnosis:
- Superior visualization: Intraarticular contrast distends the joint capsule and outlines the glenohumeral ligaments, particularly the inferior glenohumeral ligament complex where HAGL lesions occur 1, 2
- Improved diagnostic accuracy: Direct MR arthrography has higher sensitivity and specificity for detecting ligamentous injuries compared to non-contrast MRI or indirect MR arthrography 1
- Better delineation: The contrast outlines tears and avulsions, making them more conspicuous 2, 3
Technical Considerations
When performing MR arthrography for suspected HAGL lesion:
- A dilute solution of gadolinium chelate (typically 1:200 dilution) is injected directly into the glenohumeral joint 1
- Fluoroscopic guidance is recommended for accurate needle placement 1
- Comparison of MR images with fluoroscopic images is essential for proper interpretation 1
- The radiocarpal injection is most common, but if there is concern for an ulnar-sided detachment, additional DRUJ injection should be considered 1
Diagnostic Challenges
Despite its advantages, MR arthrography for HAGL lesions has some limitations:
- False positives: Some MRI findings classically associated with HAGL may represent other abnormalities of the inferior glenohumeral ligament complex 4
- Specific features: To distinguish true HAGL lesions from iatrogenic extravasation during contrast injection, look for:
- Anterior band disruption (100% specific for true tears)
- Thickened ligament margins (>3mm)
- Scarred appearance at torn margins 3
Associated Injuries
HAGL lesions rarely occur in isolation. Be vigilant for commonly associated injuries:
- Rotator cuff tears (present in up to 40% of cases) 5, 6
- Bankart lesions 6, 7
- Hill-Sachs lesions 6
- Osteochondral injuries of the humeral head 6
Clinical Implications
Early and accurate diagnosis of HAGL lesions is critical as:
- They occur in approximately 9.3% of cases with anterior shoulder instability 7
- Most HAGL lesions cause recurrent instability and require surgical repair 2
- Arthroscopic or open surgical repair yields excellent outcomes when properly diagnosed 2
In summary, direct MR arthrography with intraarticular contrast is the imaging modality of choice for diagnosing HAGL lesions, providing superior visualization of the glenohumeral ligament complex compared to intravenous contrast techniques.