SLAP Lesions and Instability

By David R. Diduch, MS, MD

Slap (superior labrum anterior to posterior) lesions involve injuries to the superior labrum with varying degrees of avulsion of the long head of the biceps attachment. SLAP lesions can be difficult to diagnose, difficult to treat, and difficult to determine in importance. A commonly accepted classification system includes 4 types. Type I lesions involve degenerative fraying of the superior labrum, which may be a normal consequence of aging. Simple arthroscopic debridement is sufficient for what may be a diagnosis that is overdone. Type III lesions involve a bucket handle tear of the labrum that mechanically catches while the biceps anchor is preserved. Simple debridement of the impinging labrum is sufficient. Lesions that compromise the biceps anchor, including Type II and Type IV lesions, are most important clinically and the focus of this review.

SLAP lesions generally occur by either traction or compression.1 Compression injuries can involve a fall onto an outstretched, partially abducted arm. Traction injuries may occur from a sudden longitudinal pull on the arm, such as a water skiing injury or trying to catch oneself from a fall. In addition, overhead throwing athletes can create or worsen a superior labral detachment through torsion on the biceps anchor that has been termed the "peel-back mechanism."2 When the arm is brought into the cocking phase for throwing, the biceps anchor is torqued and the labrum can be "peeled-back" over the glenoid rim.

The diagnosis is frequently both difficult and delayed. The most common physical findings are pain with forward elevation (Neer maneuver) and palpable popping or snapping with shoulder motion, or pain in the same abducted, externally rotated position that is provocative for anterior stability.1 Additional tests that may be helpful may include the Speed test and O’Brien test for the anterior variant of Type II lesions, and posterior pain on the Jobe relocation test for posterior Type II variants.3 More often than not, however, the examiner has just a suggestion of biceps involvement prompting an MRI. The sensitivity of the MRI may be enhanced by the use of intra-articular contrast. The diagnosis is never certain until diagnostic arthroscopy is performed. Even then, the anatomic variability encountered at arthroscopy can make the diagnosis difficult.

What to do with SLAP lesions hinges upon what problems they cause. It is important to understand that the entire labrum and biceps anchor attachment circling the glenoid work together to preserve shoulder stability. Unlike Bankart lesions anteriorly that result in full dislocations, detachment of the labrum superiorly never manifests in gross instability because the acromion prevents upward dislocation. Instead, the subtle increased laxity results in abnormal translation in the shoulder that can be manifested as tension overload on the rotator cuff. Articular-sided partial thickness cuff tears should alert the surgeon to the possibility of subtle instability. Going straight to an acromioplasty may not improve the patient’s symptoms or solve the underlying problem. This is especially true in throwing athletes or young patients that present with partial thickness cuff tears. Indeed, Morgan and colleagues demonstrated that there were lesions specific to partial thickness cuff tears associated with SLAP lesions.3 More posterior SLAP lesions resulted in slightly posterior partial thickness cuff tears, while anterior variants of Type II SLAPs resulted in more anterior cuff tears. The recent addition to the shoulder alphabet soup, SLAC (superior labrum anterior cuff), also demonstrates this concept.

Unless one is addressing an acute SLAP lesion, there is at least a 70% chance there will be other significant pathological conditions in the shoulder (40% rotator cuff tears, 20% associated labral pathology).1 The surgeon should not confuse the normal anatomic variants found in the anterior superior labrum from 1 o’clock to 3 o’clock with pathologic conditions. The sublabral hole or the absent labrum in this area often associated with a thickened middle glenohumeral ligament (Buford complex) have been noted in 12-18% of shoulders.4 An interesting finding in a recent study by Ilahi was that those patients with a Buford complex or sublabral foramen were at a 5- to 7-fold greater risk than other patients to have a SLAP lesion.4 Because many patients with a Buford complex or sublabral foramen also had absent superior glenohumeral ligaments, it has been suggested that a deficient anterior superior labrum puts more stress on the biceps attachment, thereby putting it at risk to avulse with trauma or repetitive throwing. However, the sublabral foramen should never be reattached as it is in itself not pathologic, and attachment where it has never been could restrict external rotation.

If the surgeon appreciates the importance of the biceps attachment and the circle concept of the labrum, it will aid in determining the proper treatment for the patient. A good exam under anesthesia and looking for a "drive-through sign" at arthroscopy may alert the surgeon to occult instability. If the diagnosis is correct, fixing the SLAP lesion will correct the problem.

Fixation choices for SLAP lesions involve absorbable tacks or suture anchors. A common problem with absorbable PLA tacks is fragmentation of the head with loose body symptoms necessitating a second arthroscopy. This is obviously not desirable. More rapidly absorbing PGA tacks can be used but require strict immobilization until healing occurs at 6-8 weeks. Particulate synovitis has been described as these break down. Suture anchors offer the ability to tension the repair while avoiding intraarticular debris. Both absorbable and metal anchors have been used with good success. The tricks are in passing the suture and working under the acromion. More posterior lesions may be accessed with a posterolateral "Port of Wilmington."2 Superior and anterior SLAPs are best accessed through an anterior superior portal with a separate anterior working portal for shuttling suture. The Bioknotless anchor (Mitek Worldwide, Norwood, Mass) offers the added benefits of an absorbable implant without the need to tie knots in a difficult location.

Once the biceps anchor is effectively secured, any "drive-through sign" should be eliminated and excess tension on the cuff relieved. Simple debridement of a partial thickness cuff tear should suffice unless a surgeon has some other evidence of outlet impingement. If further subtle instability exists, suture plication of the rotator interval or limited thermal capsulorraphy (stripes only, never paint) can be performed to better balance the shoulder.

References

1. Mileski RA, Snyder SJ. Superior labral lesions in the shoulder: Pathoanatomy and surgical management. J Am Acad Orthop Surg. 1998;6:121-131.

2. Burkhart SS, Morgan CD. The peel-back mechanism: Its role in producing and extending posterior type II SLAP lesions and its effect on SLAP repair rehabilitation. Arthroscopy. 1998;14(6):637-640.

3. Morgan, CD, et al. Type II SLAP lesions: Three subtypes and their relationships to superior instability and rotator cuff tears. Arthroscopy. 1998;14(6):553-565.

4. Ilahi OA, Labbe MR, Cosculluela P. Variants of the anterosuperior glenoid labrum and associated pathology. Arthroscopy. 2002;18(8):882-886.