Rotator cuff tears are one of the most common causes of shoulder pain mostly in older patients.
Prevalence of tear increases with age. Most significant findings are impingement and "arc of pain" sign (pain during descent of abducted arm) 1. Supraspinatus weakness, night pain and weakness of external rotation (seen in infraspinatus tear) may also be present.
Important causes include:
- chronic repetitive
- subacromial impingement
- tendon degeneration
A modification of the original Codman classification (1930) may be used to categorize tears:
- full thickness rotator cuff tear
- complete cuff tear: full thickness as well as full-width tear
- vertical with a connection from joint to bursa, not involving the whole breadth of tendon
partial thickness rotator cuff tear
- bursal surface tear
- articular surface tear
- intratendinous tear / central tears: not in communication with the joint surface or with the bursal surface of the tendon 7; also known as tendon delamination or interstitial tear; if the gap is filled with fluid then it is called cleavage tear of the rotator cuff tendon
Exact features depend on the type of tear. General features include
Typically, these are normal in acute tears with chronic tears showing degenerative-type changes 1:
- may show a decreased acromiohumeral interval
- < 7 mm on true AP shoulder radiograph in chronic tears
- < 2 mm on an 'active abduction' view in acute tears
- may show decreased supraspinatus opacity and decreased bulk due to fatty atrophy in chronic tears
- humeral subluxation superiorly may be seen in chronic tears
- may show features of acromial impingement
- spur formation on the undersurface of acromioclavicular joint
- acromion with an inferolateral tilt seen on outlet view (i.e. modified 'Y' view)
- type III acromion
- secondary degenerative changes: sclerosis, subchondral cysts, osteolysis, and notching/pitting of greater tuberosity
In the hands of a good radiologist, ultrasound may have up to 90% sensitivity and specificity. It can also reveal other mimics like tendinosis, calcific tendinitis, subacromial-subdeltoid bursitis, greater tuberosity fracture, and adhesive capsulitis.
Full-thickness tears extend from bursal to the articular surface, while partial thickness tears are focal defects in the tendon that involve either the bursal or articular surface. Full-thickness appear on ultrasound as hypoechoic/anechoic defects in the tendon. Due to the fluid replacing tendon, cartilage shadow gets accentuated giving a double cortex or cartilage interface sign. Also, due to the defect, overlying peribursal fat dips down into the tendon gap, creating a sagging peribursal fat sign 1.
Direct signs are:
- non-visualization of supraspinatus tendon
- hypoechoic discontinuity in tendon
Indirect signs are:
Secondary associated signs are:
- cortical irregularity of greater tuberosity
- shoulder joint effusion
- fluid along biceps tendon
- fluid in the axillary pouch and posterior recess
Complete tears are easier to diagnose on MRI than full-thickness tear 2 . Hyperintense signal area within the tendon on T2W, fat-suppressed, and GRE sequences, usually matches to fluid signal.
Partial tears are extending to either the bursal or articular surface, and sometimes intrasubstance. Retraction of tendinous fibers from the distal insertion into the greater tuberosity may also be considered partial tear.
Complete tears extend from articular to bursal surface, most commonly in supraspinatus tendon. The presence of tendon defect filled with fluid is the most direct sign of rotator cuff tear. Tendon retraction may also be present, which can be graded using the Patte classification. Indirect signs on MRI are - subdeltoid bursal effusion, medial dislocation of biceps, fluid along biceps tendon, and diffuse loss of peribursal fat planes. Muscle atrophy and fatty replacement is seen in chronic cases and can be graded using the Goutallier classification, or assessed with the tangent sign or scapular ratio 6,9. Chronic tears have degenerative changes at acromioclavicular joint, acromioclavicular joint cysts, as well as intramuscular cysts.
MR arthrography may enhance the detection of rotator cuff tears, especially complete tears.
General imaging differential considerations include:
- calcific tendinitis
- subacromial-subdeltoid bursitis
- greater tuberosity fracture
- adhesive capsulitis
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