Introduction:
The rotator cuff comprises four muscles and their tendons that stabilize the shoulder and facilitate movement:
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Tears may be partial or full-thickness, and imaging plays a crucial role in diagnosis, classification, and pre-surgical planning.
Imaging Modalities:
1. Plain Radiograph:
- Initial modality
- May show:
- High-riding humeral head (suggesting chronic tear)
- Greater tuberosity irregularities
- Acromial spurs (impingement)
- Superior migration (in massive cuff tears)
2. Ultrasound (USG):
- Dynamic, cost-effective
- High sensitivity in experienced hands
- Findings:
- Discontinuity of tendon fibers
- Focal hypoechoic defects
- Fluid in subacromial-subdeltoid bursa
- Retraction of tendon
- Can assess dynamic impingement
3. MRI:
- Gold standard
- Provides excellent soft-tissue detail
- Useful sequences:
- T2-weighted fat-sat / PD fat-sat (sagittal, coronal, axial)
- T1-weighted images (for fatty atrophy)
MRI Features of Rotator Cuff Tear:
A. Supraspinatus Tear (most common):
Partial Thickness Tear:
- Increased signal intensity not extending through full tendon
- May involve:
- Bursal surface (more common)
- Articular surface
- Intrasubstance
Full Thickness Tear:
- Fluid signal traversing full tendon thickness on T2
- Retraction of tendon
- Bare greater tuberosity
- Discontinuity of fibers
- Associated signs:
- Muscle atrophy
- Fatty infiltration (Goutallier grade)
- Joint effusion
- Bursal fluid
B. Subscapularis Tear:
- Axial and sagittal best
- Disruption of normal tendon course
- Subluxation of long head of biceps tendon (often associated)
C. Infraspinatus & Teres Minor Tear:
- Seen in larger or massive tears
- Posterior cuff atrophy on sagittal images
Grading of Tear (MRI):
| Type | Description |
|---|---|
| Partial Thickness | <100% thickness involved |
| Full Thickness | Full tendon discontinuity |
| Complete Tear | Tendon retracted from insertion |
| Massive Tear | Involving ≥2 tendons or ≥5 cm retraction |
Other Important MRI Signs:
- Magic angle effect: May mimic tear, especially in supraspinatus — use appropriate angulation and fat-sat
- Goutallier classification: Assesses fatty degeneration (T1 sagittal)
- Tangent sign: For muscle atrophy (supraspinatus)
MR Arthrography:
- Especially useful for partial-thickness tears and labral injuries
- Increased sensitivity in intra-articular and small tears
CT Arthrography:
- Useful when MRI contraindicated
- Detects full-thickness tears, retraction, and atrophy
Conclusion:
MRI is the preferred modality for evaluating rotator cuff tears, providing accurate assessment of tear type, location, retraction, and associated changes like atrophy or fatty infiltration. Ultrasound and radiographs also play valuable roles in diagnosis and follow-up.
