What type of ultrasound scan (USS) is recommended for a left rotator cuff injury?

Ultrasound Imaging for Left Rotator Cuff Injury

Request a high-resolution musculoskeletal ultrasound of the left shoulder using a high-frequency linear array transducer (7.5-12 MHz) to evaluate the rotator cuff tendons, performed by an operator with specific musculoskeletal ultrasound expertise. 1, 2

Primary Recommendation

Ultrasound is strongly supported as a useful adjunct to clinical examination for identifying rotator cuff tears, with comparable accuracy to MRI for full-thickness tears. 1 The American Academy of Orthopaedic Surgeons provides strong evidence that ultrasonography is effective for diagnosing rotator cuff pathology. 1

Technical Specifications Required

• High-frequency linear array transducer: 7.5-12 MHz probe is essential for adequate soft tissue resolution 3, 4
• Real-time dynamic evaluation: This unique capability allows assessment during active shoulder movement, which static imaging cannot provide 4
• Operator expertise: Performance is highly operator-dependent, requiring specific musculoskeletal ultrasound training 2, 3

Diagnostic Performance

For full-thickness tears:

• Sensitivity >90% for tears ≥0.5 cm 4
• Comparable to MRI for detecting complete rotator cuff tears 1, 2
• Surgeon-performed ultrasound achieves 92-94% sensitivity for full-thickness tears 5

For partial-thickness tears:

• Sensitivity drops to 75-85.7% 5, 4
• Variable interobserver agreement makes this less reliable than MRI 2, 6
• Inferior to MRI for detecting articular-sided partial tears 1

When to Choose MRI Instead

MRI without contrast is preferable when:

• Partial-thickness tears are suspected clinically and ultrasound expertise is unavailable 6
• Other intra-articular pathology (labral tears, cartilage injury) may coexist 6
• Patient has acute pain limiting range of motion needed for adequate ultrasound examination 6
• Assessment of muscle atrophy and fatty infiltration is needed for surgical planning 4
• Tear size estimation and tendon retraction measurement are critical for management decisions 6, 4

Critical Advantages of Ultrasound

• Cost-effective: Far less expensive than MRI while maintaining comparable accuracy for full-thickness tears 4
• Immediate availability: Can be performed in outpatient clinic setting as point-of-care imaging 5
• Dynamic assessment: Real-time evaluation during shoulder movement is unique to ultrasound 4
• Reduced artifacts: Less susceptible to post-surgical hardware artifacts compared to MRI 7
• Guided procedures: Excellent for directing injections and aspirations 1

Important Limitations and Pitfalls

Ultrasound cannot adequately assess:

• Tendon retraction under the acromion in complete tears 4
• Differentiation between simple muscle atrophy and fatty degeneration 4
• Labral pathology and intra-articular structures 1
• Glenohumeral instability and capsular injuries 1

False negatives occur with:

• Partial-thickness tears, especially <1/3 tendon thickness 4
• Focal hyper/hypo-echogenic changes without clear discontinuity 8
• Inadequate operator experience 2, 3

Imaging Protocol Components

The ultrasound examination must systematically evaluate:

• All four rotator cuff tendons (supraspinatus, infraspinatus, subscapularis, teres minor) 2
• Long head of biceps tendon 1, 8
• Subacromial and subdeltoid bursae 4
• Dynamic assessment during active and passive motion 4

Alternative Imaging Hierarchy

If ultrasound is unavailable or inadequate:

1. MRI without contrast is the next appropriate study for soft tissue evaluation 6
2. MR arthrography is reserved for equivocal MRI findings or suspected partial tears 1, 6
3. Plain radiographs (AP, Grashey, axillary views) should always be obtained first to exclude fracture 2