Superior labrum anterior-to-posterior (SLAP) lesions

Tears of the superior labrum were first reported by Andrews in 1984. The term Superior Labrum Anterior and Posterior (SLAP) was coined by Snyder in 1990 to describe injuries of the superior labrum and biceps anchor. It may be associated with rotator cuff tears and other labral lesions. In those under 40 years, SLAP lesions are associated with shoulder instability and Bankart lesions and in those over 40 years of age, they are associated with rotator cuff tears. It may be due to acute trauma or chronic repetitive trauma.

Anatomy

The superior part of glenoid is covered by hyaline cartilage and the superior part of labrum is attached to its rim. Superior labrum is a triangular structure composed of fibrocartilage. About 73% of patients normally have a sublabral recess separating the labrum from the glenoid rim and it should not be confused with a SLAP tear. The tendon of long head of biceps inserts directly into the superior labrum and the supraglenoid tubercle.

The function of superior labrum is not clearly understood. Along with contraction of long head of biceps, It also is thought to counter the proximal migration of humeral head produced by contraction of short head of biceps

Three normal variants may be confused with SLAP tears.
1, Sublabral foramen – 3-12%
2, Sublabral foramen with cord like middle glenohumeral ligament (MGHL)- 9%
3, Cord like MGHL with completely absent anterosuperior labrum (Buford complex)- 1.5%

Pathomechanics

The mechanism of injury is unknown, it may either be due to acute trauma or chronic repetitive trauma. Three mechanisms have been proposed. According to Andrews, a pull-off mechanism or the tensile force on the superior labrum generated by eccentric contraction the biceps tendon during overhead activity is the mechanism of injury. According to Snyder, compression loading when the arm is abducted and flexed is the cause. Burkhart proposed a a peel-off mechanism when the arm is rotated when the shoulder is in maximum abduction and external rotation, such as during the late cocking phase of throwing is the cause. Another mechanism is that the lesion may be secondary to shoulder instability.

Classification

Snyder classification

I- Fraying and degeneration of the superior labrum with intact biceps attachment
II- Bucket handle tear of superior labrum and biceps anchor. Most common type – 55%
III- Bucket handle tear of superior labrum with intact biceps labrum- 9%
IV- bucket handle tear of superior labrum that extends into the biceps tendon- o10%.
Type I is typically associated with rotator cuff tears and type III and IV with traumatic shoulder instability.

Maffet added four more types

V- Tear of anteroinferior labrum that extends into the superior labrum
V- Biceps tendon avulsion with associated unstable flap tear of labrum.
VII- Biceps and superior labral tear extends beneath the middle glenohumeral ligament.

Recently Nord and Ryu has added 3 more types

VIII- Superior labral tear with extension to posterior labrum
IX- Superior labral tear with the tear extending to the entire labrum
X- Superior labral tear with a reverse Bankart lesion
Morgan subclassified type II into A- Anterior B- Posterior and C- Combined.

Clinical features

History should be taken carefully to identify the mechanism of injury. Patients present with vague shoulder pain. There may be associated snapping which gets aggravated by overhead activities. If tear extends to the anterior labrum there may be associated instability. Nocturnal exacerbation is seen in presence of associated rotator cuff lesions. Patient should be asked about the precipitating traumatic event. Functional limitation should be assessed by asking about the ability to perform overhead activities and throwing. Many tests have been described for the diagnosis.

Numerous tests are available, but they are of 2 types; active tests which try to recreate the torsional traction force that caused the injury or passive tests that exert compressive stress on the labrum. O’Brien test is an active test and crank test is a passive test.

O’Brien’s test (Active compression test)

Patient position- Standing.

Examiner position – By the side with one hand on shoulder and other hand on the distal forearm.

Joint position- Forward flexion of shoulder to 90, adduction of 10-15, fully internally rotated. Elbow straight. Thumb pointing down.

Procedure- Elevate against resistance. Repeat with shoulder in external rotation.

Interpretation – Pain in internal rotated position and absence of pain in external rotation suggestive of SLAP lesion. Ask about the location of pain, if it is over the acromioclavicular joint then the test is negative.
Sensitivity- 90%
Specificity- 98%

Crank test(Compression rotation test)

Patient position – Supine

Joint position- Shoulder in 160 abduction, 30 forward flexion. Elbow flexed

Procedure- Stabilise scapula with one hand, grasp the elbow with the other hand. Axially load and rotate externally and internally.

Interpretation- Pain and reproduction of patient’s symptoms indicate labral pathology

Reliability – 91% sensitive, 93% specific, 94% positive predictive value, 90% negative predictive value.

Resisted supination external rotation test

Patient position- Supine.

Joint position- Shoulder 90 abducted, elbow 70 flexed, forearm semipronated.

Procedure- Externally rotate the shoulder and ask the patient to supinate the forearm against resistance.

Interpretation- Pain indicative of SLAP lesion.

Anterior slide test

Patient position – Standing.

Joint position – Hand on hips with thumb pointing posteriorly.

Procedure – Apply forward and axial pressure over the elbow and ask the patient to resist.

Interpretation – Pain indicate superior labral pathology.

Reliability – 78% sensitive and 90% sensitive for type II SLAP lesion.

Diagnosis

MR arthrogram is the most reliable method to confirm the diagnosis. Contrast extending into the substance of superior labrum is suggestive of SLAP lesion. Arthroscopy is the gold standard for diagnosis. But differentiation from normal variants may be difficult. Fraying of labrum, associated synovitis, abnormal laxity of labrum of >5mm, associated chondral lesions of glenoid or humeral head superiorly often help in confirming the diagnosis.

Treatment

A complete arthroscopic examination of the shoulder is performed through the posterosuperior and anterosuperior portals. Look for widened rotator interval, drive-through sign, labral lesions, Bankart lesions, rotator cuff tears and impaction fracture of humeral head. Probe the biceps anchor and superior labrum looking for laxity, detachment, and fraying.

The portals used depend on the type of SLAP tear identified. The treatment in young patients may be debridement, SLAP repair or biceps tenodesis and in the older patients by biceps tenotomy. pThe technique of repair depends on the type of tear. For the commonest type II tear posterosuperior, high rotator interval and midlateral portals are used. First mobilise the biceps- labral complex. Then prepare the bony bed for reattachment till bleeding bone is exposed. SLAP Lesions can be reattached using suture anchors, trans-glenoid sutures or staples. Torn biceps and superior labrum is commonly reattached using one-anchor-2-suture technique or two-anchor technique.

Type III tears are treated by debridement of the bucket handle portion. Type IV tears treated by debridement or repair of bucket handle labral tear and biceps tendon tenodesis or tenotomy. Type V tears are treated by reattachment of SLAP tears and Bankart lesion using suture anchors. Type VI tears are treated by debridement of flap tear and reattachment similar to type II tears. Type VII tears are treated by repair of superior labrum like in type II and repair of MGHL. Type VIII are treated by repair of superior labrum similar to type II and reattachment of posterior labrum.

Postoperatively limb is immobilised in an arm pouch for 3 weeks. Physiotherapy started in the 4th week with advice to avoid movements beyond 90 degree abduction, 70 degree adduction and 0 degree external rotation till the 7th week after which no movement restriction is necessary.

Outcome

Excellent results are reported in 15-30%, ‘good to excellent’ results in 40-94% after SLAP repair. The best candidates for repair of SLAP lesions is young patients with type II lesions, acute trauma, positive clinical tests and MR arthrogram and intact biceps anchor.

References

Andrews JR, Carson WG. The arthroscopic treatment of glenoid labrum tears in the throwing athlete.Orthop Trans.1984;8:44

Snyder SJ, Karzel RP, Del Pizzo W, Ferkel RD, Friedman MJ. SLAP lesions of the shoulder. Arthroscopy. 1990;6:274-279

Maffet MW, Gartsman GM, Moseley B. Superior labrum-biceps tendon complex lesions of the shoulder.Am J Sports Med. 1995;23:93-98.

Morgan CD, Burkhart SS, Palmeri M, Gillespie M. Type II SLAP lesions: three subtypes and their relationships to superior instability and rotator cuff tears.Arthroscopy. 1998;14:553-565.

Scott E Powell, Keith D Nord, Richard KN Ryu: The diagnosis, classification and treatment of SLAP lesions. Oper Tech Sports Med 12: 99-110, 2004

Joseph P. Burns, Michael Bahk, Stephen J. Snyder: Superior labral tears : reapir versus biceps tenodesis. J Shoulder Elbow Surg (2011)20,S2-S8

O’Brien SJ, Pagnani MJ, Fealy S, et al: The active compression test: A new and effective test for diagnosing labral tears and acromio-clavicular joint abnormality. Am J Sports Med 26: 610–613, 1998

Parentis MA, Mohr KJ, ElAttrache NS: Disorders of the superior labrum: Review and treatment guidelines. Clin Orthop 400: 77–87, 2002.

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