Superior labral anterior posterior tear

Superior labral anterior posterior (SLAPtears are injuries of the glenoid labrum, and can often be confused with a sublabral sulcus on MRI. 

Pathology

SLAP tears involve the superior glenoid labrum, where the long head of biceps tendon inserts. Unlike Bankart lesions and ALPSA lesions, they are uncommonly (20%) associated with shoulder instability 5.

Aetiology

In the acute setting they are most frequently seen in falls onto an out-stretched arm or in throwing sports-people.

Classification

Many types have been described (at least nine), although how relevant these are to management is debatable. When first described, four types of SLAP existed, which highlight the most important features:

  • type I: fraying of the superior labrum
  • type II: detachment of the superior labrum and biceps anchor from the underlying superior glenoid
  • type III: bucket handle tear of the superior labrum without extension into the long head of biceps tendon
  • type IV: bucket handle tear of the superior labrum with extension into the long head of biceps tendon

Radiographic features

MR arthrogram

The investigation of choice is MR arthrogram, which is variably reported as having accuracies of 75-90%, although distinguishing between subtypes can be difficult 2.

High signal (fluid on T2WI or arthrographic contrast on T1WI) is seen extending into the superior labrum, and tracking into the labrum and sometimes into the biceps tendon is the characteristic finding.

Treatment and prognosis

  • type I tears are usually asymptomatic and do not require treatment
  • type II tears require surgical reattachment
  • type III tears usually require resection of the bucket handle tear 2

Differential diagnosis

  • sublabral sulcus: tears of the labrum can appear similar to a normal sublabral sulcus or normal glenoid articular hyaline cartilage which extends beneath the labrum; the following features help distinguish a tear from the latter two 1-2
    • high T2 signal or contrast curves laterally
    • high signal width within labrum > 2 mm
    • high signal or contrast extends posterior to biceps anchor 
    • double Oreo sign
  • sublabral foramen: SLAP tear type II, in which the labrum is avulsed from the underlying glenoid can look similar to a sublabral foramen (a variant of normal), but can be distinguished from the latter by observing high signal extending between the glenoid and labrum posterior to the attachment of the biceps tendon

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