What are the differential diagnoses and treatment options for a patient presenting with symptoms of a rotator cuff injury?

Differential Diagnoses for Rotator Cuff Injury

When evaluating a patient with suspected rotator cuff injury, the primary differential diagnoses include glenohumeral instability, labral tears (including SLAP lesions), acromioclavicular joint pathology, adhesive capsulitis, proximal humerus fractures, and in younger throwing athletes, Little Leaguer shoulder and secondary impingement from scapular dyskinesis. 1

Key Differential Diagnoses

Fractures and Bony Pathology

• Proximal humerus fractures occur in up to 40% of cases presenting with shoulder pain after trauma, particularly in bimodal age distribution (young patients with high-energy trauma and older patients with low-energy falls) 1
• Clavicle and scapula fractures must be excluded as they commonly present with similar pain patterns 1
• Little Leaguer shoulder (proximal humeral physeal stress injury) occurs in skeletally immature pitchers aged 11 to early teenage years, representing a Salter-Harris type I injury from torsional overload 1

Labral and Capsular Pathology

• SLAP (Superior Labral Anterior-to-Posterior) tears are common in throwing athletes and can mimic rotator cuff symptoms 1
• Bankart lesions and other labroligamentous injuries occur with glenohumeral instability 1
• Glenohumeral instability presents with atraumatic microinstability in skeletally immature throwers and weak rotator cuff muscles 1, 2

Acromioclavicular Joint Pathology

• AC joint separations are frequently underreported as patients may not seek immediate treatment for low-grade injuries 1
• AC joint pathology can coexist with rotator cuff tears and must be differentiated 1

Impingement Syndromes

• Secondary impingement from scapular dyskinesis (poor coordination of scapular upward rotation and posterior tilting during arm elevation) contributes to rotator cuff-like symptoms 1, 2
• Subacromial and internal impingement are particularly common in throwing athletes 3

Neurovascular Complications

• Axillary artery injury should be considered with proximal humeral fractures, shoulder dislocations, or scapula/rib fractures, especially with vascular compromise on examination 1
• Neuropathic pain from brachial plexus or peripheral nerve injury (axillary, suprascapular, radial, ulnar, median) can occur after trauma 1

Diagnostic Algorithm

Initial Evaluation

• Plain radiographs are mandatory as the first imaging study, including AP views in internal and external rotation plus axillary or scapula-Y view to assess for fractures, dislocations, and bone loss 1, 2
• Radiographs must be performed upright as malalignment can be underrepresented on supine films 1

Advanced Imaging Selection

For suspected soft-tissue injury with normal radiographs:

• MRI is the optimal modality with 98% sensitivity and 79% specificity for any rotator cuff tears, and 94% sensitivity and 93% specificity for full-thickness tears 2, 4
• MR arthrography is preferred when partial-thickness tears or labral pathology are suspected, offering superior detection of partial-thickness articular surface tears and SLAP lesions compared to conventional MRI 1, 2
• Ultrasound is equivalent to MRI for full-thickness tears (92% sensitivity, 93% specificity) but has variable performance for partial-thickness tears with operator-dependent interpretation 1, 2, 4
• CT arthrography is reserved for MRI contraindications, with similar performance to MR arthrography for full-thickness tears but significantly poorer performance for partial-thickness tears 1, 2

For fracture characterization:

• CT is superior to radiography for delineating complex fracture patterns and has better interobserver agreement than radiographs for grading humeral head fractures 1

For vascular compromise:

• CT angiography is the preferred examination when physical examination suggests arterial injury 1

Treatment Considerations

Conservative Management

• Most soft-tissue injuries including labral tears and rotator cuff tears can undergo conservative management initially with NSAIDs, corticosteroid injections, and functional rehabilitation 1, 3
• Complete rest from throwing for minimum 6 weeks after diagnosis, followed by 6 weeks of strengthening (total 3 months rest) is recommended for Little Leaguer shoulder 1
• Rehabilitation must emphasize rotator cuff, periscapular muscles, and core strengthening with capsular flexibility exercises 1, 3

Surgical Indications

• Full-thickness rotator cuff tears in most patients should undergo surgical repair as soon as possible, with better outcomes when repaired within 4 months of injury 5
• Unstable or significantly displaced fractures and joint instability require acute surgical treatment 1
• Partial-thickness tears may be managed nonoperatively with physical therapy, NSAIDs, and injections 5

Critical Pitfalls to Avoid

• Noncontrast CT cannot assess rotator cuff pathology in the acute setting and should not be used for soft-tissue evaluation 1, 2
• FDG-PET/CT and bone scans are not routinely used for rotator cuff tears as they cannot describe tear extent or degree of atrophy 1, 2
• Ultrasound has variable interobserver agreement for partial-thickness tears, making it less reliable than MRI for this indication 1, 2
• Failure to obtain axillary or scapula-Y views can result in missed glenohumeral and AC dislocations that appear normal on AP views alone 1
• In youth throwers, undersurface tears from overuse are more common than primary impingement, requiring different treatment approaches 1, 2
• Delayed rotator cuff repair up to 4 months has not shown adverse outcomes, so immediate soft-tissue diagnosis in the setting of proximal humerus fracture may not be required 1