Superior Labral AnteroPosterior Lesions (Synder 1990)
Tears are clasically located at biceps anchor
Begin posteriorly and extend anteriorly
Commonly occur at 12 O clock position
Superior labrum is loosely attached, more mobile and meniscal in appearance
Inferior labrum is firmly continuous with articular cartilage
Superior and anterosuperior labrum have diminished vascularity relative to the inferior labrum, hence more prone for degeneration
Superior portion of glenoid labrum serves as anchor for biceps tendon and provides stability
Impingement or rotator cuff tears can be caused by unstable biceps insertion, seen in SLAP lesions
Mechanism:
Compression force to shoulder, usually after fall onto an outstretched arm
traction on arm, due to sudden pull or repetitive overhead use, as in baseball pitchers, swimmers, tennis and volleyball players.
Clinical features:
Pain at the top of shoulder
Clicking, catchinganf pain on overhead activities
Anterior slide test
O'Brien test
Crank test
Classification & MR appearances:
Begin posteriorly and extend anteriorly, terminating before or at midglenoid notch
FS coronal oblique T1-weighted sequence provides highest sensitivity. Axials and sagittal help
SLAP I: degenerative fraying of free edge of superior glenoid labrum. High signal in superior labrum with irregular shape, stable biceps anchor. Non-surgical
SLAP II:most common type. Avulsion of labral–bicipital complex (superior labrum + biceps anchor) from superior glenoid. Detachment and inferior displacement of triangular superior labrum. Line of high signal across base of hyperintense labrum to periphery; biceps tendon shows normal signal and shape and attaches to the avulsed labrum. Gd tracks laterally
SLAP III: bucket-handle tears with preserved biceps anchor. line of high signal across base of hyperintense labrum extending beyond equator (undisplaced bucket-handle tear). Deficient superior labrum and the biceps tendon is followed to supraglenoid tubercle.
SLAP IV: bucket-handle tears with extension into biceps tendon. line of high signal across the base of normally hypointense labrum to periphery; extending beyond equator with deficient superior labrum + hyperintensity and splitting of the fibers of biceps tendon
SLAP V: anteroinferior Bankart lesion extending upward to include separation of the biceps tendon
SLAP VI: unstable radial or flap tears associated with separation of biceps anchor
SLAP VII: extension of SLAP lesion beneath middle glenohumeral ligament
False positives:
Sublabral foramen = sublabral hole = superior sublabral recess = Physiological detatchment of anterosuperior labrum. Located more anteriorly than SLAP lesion. Does not usually extend below the level of coracoid process. May be subdivided into 1. less than 2mm, 2. between 2-5mm and 3. more than 5mm. Extends medially (SLAP extends laterally) on coronal imaging. Tend to be better defined. Foramen is typically seen between 1-3 O clock postion
Meniscoid-type superior labrum - may be misinterpreted as type II SLAP lesion
Buford complex - deficient anterosuperior labrum with thickened or band like middle glenohumeral ligament. Can simulate detached anterior labrum
Ultrasound in Labral lesions:
Anterior labral tear:
Enlarged (more than 2mm) hypoechoic zone at base of labrum
Truncated shape or absence of labrum
Abnormal labral motility on dynamic scanning
References:
1. Waldt et al. Diagnostic Performance of MR Arthrography in the Assessment of Superior Labral Anteroposterior Lesions of the Shoulder . AJR 2004; 182:1271-1278
2. Bencardino JT et al. Superior Labrum Anterior- Posterior Lesions: Diagnosis with MR Arthrography of the Shoulder. Radiology. 2000;214:267-271
3. Connel DA et al. Noncontrast Magnetic Resonance Imaging of Superior Labral Lesions . The American Journal of Sports Medicine 27:208-213 (1999)
4. Robinson G et al. Normal anatomy and common labral lesions at MR arthrography of the shoulder. Clin Rad 61 (805-821)
