Imaging for Recurrent Shoulder Dislocation
Start with plain radiographs (AP views in internal and external rotation plus axillary or scapula-Y view), then proceed directly to MRI shoulder without IV contrast as your primary advanced imaging study for evaluating recurrent shoulder instability. 1
Initial Imaging: Plain Radiographs
Begin with standard shoulder radiography including at least three views: anteroposterior projections in internal and external rotation, plus an axillary or scapula-Y view 1, 2. The axillary view is critical—glenohumeral dislocations can be completely missed on AP views alone 2. Perform these upright when possible, as supine imaging can underrepresent shoulder malalignment 2. Consider adding a Bernageau view to assess glenoid or humeral head bone loss 2.
Advanced Imaging: MRI Without Contrast
For recurrent shoulder dislocation or instability, MRI shoulder without IV contrast is the usually appropriate next imaging study 1. This represents updated 2025 guidance that differs from older recommendations.
Why MRI Without Contrast Works Well:
- In the subacute/chronic recurrent instability setting, there is typically sufficient residual joint effusion or hemarthrosis from repeated trauma to provide adequate visualization of labral and soft tissue structures without requiring arthrography 1
- MRI effectively assesses both bone loss (glenoid and Hill-Sachs lesions) and soft tissue pathology (labral tears, rotator cuff injuries, glenohumeral ligament damage) 2
- Recent evidence confirms MRI provides CT-equivalent measurements of critical bony parameters including glenoid version, glenoid concavity, and bony shoulder stability ratio 3, 4
- MRI correctly classifies 89% of on-track lesions and 76% of off-track lesions compared to CT 4
When to Consider MR Arthrography
MR arthrography may be appropriate for detailed evaluation of labral pathology in the subacute or chronic setting when the glenohumeral joint effusion is too small to provide sufficient joint distention 1. MR arthrography has historically been considered the reference standard for:
- Superior labral anterior-to-posterior (SLAP) tears
- Anterior labral injuries
- Partial-thickness rotator cuff tears
- Glenohumeral ligament injuries 2
However, the 2025 ACR guidelines now recognize that in recurrent instability, the invasive nature of arthrography may not be necessary given adequate visualization on standard MRI 1.
When to Use CT
CT shoulder without IV contrast may be appropriate for patients in whom MRI assessment of bone loss is limited 1. Consider CT specifically when:
- MRI is contraindicated (pacemakers, certain implants)
- You need highly detailed assessment of complex fracture patterns
- Precise quantification of glenoid bone loss is critical for surgical planning
- 3D reconstruction is needed for preoperative templating
Recent systematic review evidence shows 3D-CT is the most reliable and accurate modality for measuring glenoid track width 5, though standard MRI performs nearly as well for most clinical decisions 3, 4.
CT Arthrography as Alternative
CT arthrography is usually appropriate only when MRI is contraindicated 1. It performs comparably to MR arthrography for Bankart lesions, Hill-Sachs lesions, and full-thickness rotator cuff tears, but is inferior for partial-thickness tears 2.
Critical Pathology to Assess
Your imaging must evaluate:
- Labral tears (especially anterior-inferior Bankart lesions)
- Glenoid bone loss (>13.5% increases recurrence risk significantly)
- Hill-Sachs lesions and whether they are on-track or off-track
- Rotator cuff integrity (especially in patients >40 years, who have higher rates of associated cuff tears) 2
- Glenohumeral ligament injuries
- Capsular pathology
Common Pitfalls to Avoid
- Don't skip the axillary view on plain films—this is where dislocations are actually confirmed 2
- Don't assume you need arthrography—the 2025 guidelines recognize that recurrent instability typically provides natural contrast from residual effusion 1
- Don't rely on 2D-MRI alone for borderline bone loss—if measurements are indeterminate and surgical planning depends on precise quantification, add CT 4, 5
- Don't order ultrasound—it has no role in evaluating instability-related labral or bony pathology 2
Age-Specific Considerations
- Younger patients (<40 years): Focus on labral and ligamentous injuries, which drive recurrence
- Older patients (>40 years): Ensure thorough rotator cuff assessment, as cuff tears are common with dislocation in this age group 2
The algorithmic approach is straightforward: radiographs first → MRI without contrast second → add CT only if bone loss assessment is limited on MRI or MRI is contraindicated 1.