Injuries of the superior labrum–biceps complex (SLBC) have been recognized as a cause of shoulder pain since they were first described by Andrews and colleagues1 in 1985. Superior labrum anterior to posterior (SLAP) tears are relatively uncommon injuries of the shoulder, and their true incidence is difficult to establish. However, recently there has been a significant increase in the reported incidence and operative treatment of SLAP tears.2 SLAP tears can occur in isolation, but they are commonly seen in association with other shoulder lesions, including rotator cuff tear, Bankart lesion, glenohumeral arthritis, acromioclavicular joint pathology, and subacromial impingement.
Although SLAP tears are well described and classified,3-6 our understanding of symptomatic SLAP tears and of their contribution to glenohumeral instability is limited. Diagnosing a SLAP tear on the basis of history and physical examination is a clinical challenge. Pain is the most common presentation of SLAP tears, though localization and characterization of pain are variable and nonspecific.7 The mechanism of injury is helpful in acute presentation (traction injury; fall on outstretched, abducted arm), but an overhead athlete may present with no distinct mechanism other than chronic, repetitive use of the shoulder.8-11 Numerous provocative physical examination tests have been used to assist in the diagnosis of SLAP tear, yet there is no consensus regarding the ideal physical examination test, with high sensitivity, specificity, and accuracy.12-14 Magnetic resonance arthrography, the gold standard imaging modality, is highly sensitive and specific (>95%) for diagnosing SLAP tears.
SLAP tear management is based on lesion type and severity, age, functional demands, and presence of coexisting intra-articular lesions. Management options include nonoperative treatment, débridement or repair of SLBC, biceps tenotomy, and biceps tenodesis.15-19
In this 5-point review, we present an evidence-based analysis of the role of the SLBC in glenohumeral stability and the role of biceps tenodesis in the management of SLAP tears.
1. Role of SLBC in stability of glenohumeral joint
The anatomy of the SLBC has been well described,20,21 and there is consensus that SLBC pathology can be a source of shoulder pain. The superior labrum is relatively more mobile than the rest of the glenoid labrum, and it provides attachment to the long head of the biceps tendon (LHBT) and the superior glenohumeral and middle glenohumeral ligaments.
The functional role of the SLBC in glenohumeral stability and its contribution to the pathogenesis of shoulder instability are not clearly defined. Our understanding of SLBC function is largely derived from simulated cadaveric experiments of SLAP tears. Controlled laboratory studies with simulated type II SLAP tears in cadavers have shown significantly increased glenohumeral translation in the anterior-posterior and superior-inferior directions, suggesting a role of the superior labrum in maintaining glenohumeral stability.22-26 Interestingly, there is conflicting evidence regarding restoration of normal glenohumeral translation in cadaveric shoulders after repair of simulated SLAP lesions in the presence or absence of simulated anterior capsular laxity.22,25-27 However, it is important to understand the limitations of cadaveric experiments in order to appreciate and truly comprehend the results of these experiments. There are inconsistencies in the size of simulated type II SLAP lesions in different studies, which can affect the degree of glenohumeral translation and the results of repair.23-25,28 The amount of glenohumeral translation noticed after simulated SLAP tears in cadavers, though statistically significant, is small in amplitude, and its relevance may not translate to a clinically significant level. The impact of dynamic components of stability (eg, rotator cuff muscles), capsular stretch, and other in vivo variables that affect glenohumeral stability are unaccounted for during cadaveric experiments.
LHBT is a recognized cause of shoulder pain, but its contribution to shoulder stability is a point of continued debate. According to one school of thought, LHBT is a vestigial structure that can be sacrificed without any loss of stability. Another school of thought holds that LHBT is an important active stabilizer of the glenohumeral joint. Cadaveric studies have demonstrated that loading the LHBT decreases glenohumeral translation and rotational range of motion, especially in lower and mid ranges of abduction.23,29,30 Furthermore, LHBT contributes to anterior glenohumeral stability by resisting torsional forces in the abducted and externally rotated shoulder and reducing stress on the inferior glenohumeral ligaments.31-33 Strauss and colleagues22 recently found that simulated anterior and posterior type II SLAP lesions in cadaveric shoulders increased glenohumeral translation in all planes, and biceps tenodesis did not further worsen this abnormal glenohumeral translation. Furthermore, repair of posterior SLAP lesions along with biceps tenodesis restored abnormal glenohumeral translation with no significant difference from the baseline in any plane of motion. Again, the limitations of cadaveric studies should be considered when interpreting these results and applying them clinically.