Rotator Cuff Tear

Diagnosis Definition

• The rotator cuff is a stabilizing group of muscles (teres minor, supraspinatus, infraspinatus, and subscapularis) and tendons which approximate each other along their insertion sites to the humeral head 
• The rotator cuff holds the humerus within the glenoid and allows for arm movement
• Rotator cuff tears can result from aging, trauma, ischemia, repetitive stress, or impingement 
• Impingement most commonly results from compression of the cuff fibers by subacromial bone spurs or degenerative acromioclavicular joint osteophytes
• Tears can be partial (involve only the articular or bursal surface), full thickness (extend from the articular to the bursal surface), or intrasubstance (without articular or bursal extension)
• Supraspinatus tears are most common

Imaging Findings

• Routine shoulder MR sequences include coronal oblique proton density (PD), coronal oblique fat saturated T2 (FST2), sagittal T1, sagittal FST2, and axial fat saturated PD; the protocol is altered if the patient has metallic hardware 
• Tendon tears appear as high signal areas of tendon fiber disruption
• Tears often retract and the extent of retraction on MR can be calculated on coronal images as the distance from the greater tuberosity of the humeral head and the location of the retracted myotendinous junction

KEY IMAGES

Pearls

• Tears are best seen on Fat-Sat T2 sequences
• Tears most commonly occur within 1 cm of the insertion (critical zone)
• There is often focally variant increased signal in the distal supraspinatus tendon insertion on T1 and PD coronal MR images where the tendon has an oblique course as it wraps over the greater tuberosity; this is due to magic angle artifact and can be confused with tendinopathy

References

1. Morag Y, Jacobson JA, Miller B, et al.  MR Imaging of Rotator Cuff Injury: What the Clinician Needs to Know.  RadioGraphics 2006; 26(4):1045-1065