What imaging study should be ordered for a patient with a suspected rotator cuff injury?

Imaging for Suspected Rotator Cuff Injury

Order plain radiographs first (AP views in internal and external rotation plus axillary or scapular Y view), followed by MRI shoulder without IV contrast as the definitive imaging study for suspected rotator cuff tears. 1, 2

Initial Imaging: Plain Radiographs (Always First)

• Obtain AP views in internal and external rotation plus axillary or scapular Y view to exclude fractures (proximal humerus, clavicle, scapula), dislocations, and osseous pathology before proceeding to advanced imaging 1, 2
• Proximal humerus fractures occur in up to 40% of trauma cases presenting with shoulder pain, making radiographs mandatory 2
• Failure to obtain axillary or scapular Y views can result in missed glenohumeral and AC dislocations that appear normal on AP views alone 2

Definitive Imaging: MRI Without IV Contrast

MRI shoulder without IV contrast is the optimal imaging modality for evaluating suspected rotator cuff tears, as it is "generally considered the best modality for adequately assessing most soft tissue injuries, including labroligamentous, cartilage, and rotator cuff pathology" 1, 2

Why MRI Without Contrast is Superior

• High diagnostic accuracy: 98% sensitivity and 79% specificity for any rotator cuff tears; 94% sensitivity and 93% specificity for full-thickness tears 2
• Post-traumatic joint effusion enhances visualization: In acute trauma, the presence of joint effusion provides natural distention that enhances soft tissue visualization on non-contrast MRI, making it preferable to MR arthrography 1, 2
• Evaluates concurrent pathology: MRI assesses tear size, tendon retraction, muscle atrophy, fatty infiltration, and identifies coexisting labral tears or cartilage injury that ultrasound cannot detect 2, 3
• Standard intravenous gadolinium contrast provides no additional diagnostic benefit for rotator cuff evaluation and unnecessarily exposes patients to contrast-related risks 2

Alternative: Ultrasound (Operator-Dependent)

Ultrasound may be considered as a first-line study only if performed by an experienced musculoskeletal sonographer, but has significant limitations:

When Ultrasound is Acceptable

• High accuracy for full-thickness tears: Sensitivity 86.7-90%, specificity 93-100%, comparable to MRI 3, 4, 5
• Cost-effective and immediately available alternative when MRI access is limited 3
• Useful for guiding injections and aspirations 3

Critical Limitations of Ultrasound

• Poor sensitivity for partial-thickness tears: Only 12.5-50% sensitivity compared to 50-89.7% for MRI, with variable interobserver agreement making it unreliable 3, 6, 5
• Cannot assess labral pathology, glenohumeral instability, capsular injuries, or intra-articular structures 3
• Highly operator-dependent: Performance varies significantly based on sonographer expertise 3, 7
• Limited by acute pain restricting range of motion and large body habitus 1
• A negative ultrasound is less trustworthy than a positive one, requiring MRI follow-up to avoid false-negatives 6, 5

When to Use MR Arthrography

MR arthrography should be reserved for specific scenarios, not as initial imaging:

• When conventional MRI is equivocal for partial-thickness tears, particularly articular surface tears where MR arthrography shows increased sensitivity 1, 2
• For detailed evaluation of labral pathology when this is the primary concern alongside rotator cuff assessment 1, 2
• In subacute or chronic presentations where glenohumeral joint effusion is too small to provide adequate joint distention 2
• Do not use in acute trauma with post-traumatic effusion present, as the joint is already distended, negating the advantage of arthrography 2

What NOT to Order

• CT shoulder: Cannot assess rotator cuff pathology or soft tissue injuries; reserved only for evaluating complex fracture patterns 1, 2
• MRI with standard IV contrast (non-arthrographic): Provides no additional diagnostic benefit for rotator cuff evaluation 1, 2
• FDG-PET/CT or bone scans: Not routinely used for rotator cuff tears as they cannot describe tear extent or degree of atrophy 2

Critical Pitfalls to Avoid

• Do not proceed directly to orthopedic referral without advanced imaging: MRI is essential to confirm diagnosis, characterize tear extent and quality of remaining tendon, and guide appropriate treatment planning 2
• Avoid gadolinium-based contrast agents in dialysis-dependent patients or those with severe renal dysfunction (GFR <30 mL/min/1.73 m²) due to nephrogenic systemic fibrosis risk 2
• If ultrasound is negative but clinical suspicion remains high, obtain MRI: The combined sensitivity of US and MRI (92.7%) is sufficient to avoid false-negative diagnosis 5