Superior labrum anterior to posterior (SLAP) lesion commonly presents in overhead athletes and results from the detachment of the superior aspect of the glenoid labrum. Of the overhead sports, the excessive external rotation or the anteroinferior maneuver of the shoulder required in the late cocking and the deceleration phase of a baseball player’s pitch is thought to be the principal cause of SLAP lesion-induced pain. SLAP lesions, initially described by Andrew, now have an increased repertoire of variations reported since. Radiological tests such as magnetic resonance arthrography and several physical examinations are used to diagnose SLAP lesions; however, a diagnostic SLAP test that is set apart from the rest in terms of sensitivity or specificity does not exist as of yet. Diagnostic accuracy of SLAP lesions may be enhanced by combining various diagnostic examination techniques. When diagnosing SLAP lesions, a differential diagnosis of SLAP lesions from the normal, anatomic variations of the superior labrum must be made. Generally, when a SLAP lesion is diagnosed, conservative methods such as rehabilitation is first employed before attempting an arthroscopic repair using suture anchors.
Keywords: Shoulder; Labrum; Superior labrum anterior to posterior; Overhead athlete
Superior labrum anterior to posterior lesions in overhead athletes
Jin-Young Park
1, Hyoung-Weon Cho
2, Seung-Hyub Jeon
3, Kyung-Soo Oh
21Neon Orthopaedic Surgery, Global Center for Shoulder, Elbow & Sports, 2Department of Orthopedic Surgery, Konkuk University School of Medicine, 3Department of Orthopedics, Seoul Red Cross Hospital, Seoul, Korea
Copyright © 2015 Korean Arthroscopy Society and Korean Orthopedic Society for Sports Medicine. All rights reserved.
CC This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/
by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received April 7, 2015; Revised May 6, 2015; Accepted May 6, 2015
Correspondence to: Kyung-Soo Oh, Department of Orthopedic Surgery, Konkuk University Medical Center, 120-1 Neungdong-ro, Gwangjin-gu, Seoul 143-729, Korea. Tel: +82-2-2030-7360, Fax: +82-2-2030-7369, E-mail: [email protected]
Arthroscopy and Orthopedic Sports Medicine
AOSM
INTRODUCTION
With the increased popularity and commercialization of sports, the number of athletes engaged in overhead sports such as baseball, tennis, and swimming has increased;
the number of shoulder-related injuries has increased accordingly. In 1985, Andrews et al. [1] noted a correlation between the occurrence of a certain shoulder lesion the superior labrum-biceps tendon complex lesion in overhead throwers. But it was Snyder et al. [2] in 1990 who first introduced the term superior labrum anterior to posterior (SLAP) lesion and classified them into 4 types.
Later Burkhart et al. and Morgan et al. [3–5] proposed a slightly different classification system that classified SLAP lesions more broadly into 3 types: the anterior SLAP lesion, the superior SLAP lesion, and the anterior- superior combined lesion. Maffet et al. [6] expanded this
classification, emphasizing the role of shoulder instability in SLAP lesions, to 6 types.
Abundant literature supports the correlation of SLAP lesions in overhead throwing athletes. Overhead activity places abnormal, repetitive burden on the shoulder, and this persistent burden over time disrupts shoulder ligaments, muscles, and bone structures and limits range of motion (ROM) of the shoulder [7–9].
It is thought that damage to the labrum, the glenoid ligament, mainly brings about pain and limited motion seen in these patients [10]. Our understanding of the anatomic structures involved in SLAP lesions and their pathophysiology has increased with developments in magnetic resonance imaging (MRI) and arthroscopic techniques, which has improved diagnostic precision and treatment of SLAP lesions [11].
ANATOMY OF THE LABRUM
The glenohumeral joint is one of the most dynamic structures in our body requiring the cooperation of several structures to maintain the stability of this joint: articular capsule, muscles, tendons, bone structures, and the labrum [12]. The labrum is a fibrocartilagenous ring structure that is attached to the edges of the glenoid. Histologically, the labrum consists of smooth fibrous cartilage and connective elastin fibers which attach the labrum to the glenoid rim and to its surrounding tissue, respectively [11]. Vascular supply to the labrum comes from the suprascapular arteries, circumflex scapular branch of the subscapular arteries, and the circumflex humeral arteries. These arterial vessels feed through the glenoid rim from the articular capsular and periosteum but do not reach the labrum enter; consequently, the posteroinferior labrum receives more abundant blood supply than the superior and anterosuperior labrum [11,13].
Anatomically, the base of the triangular labrum lies at the glenoid rim. The cross-sectional labrum is the shape of a knee meniscus with its free edge away from the articular surface and its base forming a continuum with the articular surface [14,15]. Sometimes the superior labrum may extend over the joint and even cover the superior articular cartilage so that it originates more medially than the glenoid rim. The long head of biceps tendon originates from the superior labrum, follows the humeral bicipital groove, and runs towards the distal end. This superior labrum-biceps tendon connection may occur completely from the posterior labrum, or predominantly from the posterior labrum, or equally from the anterior and the posterior labrum; although most superior labrum- biceps tendon complexes are made predominantly from the posterior labrum [16,17].
The labrum functions to increase the depth of the glenoid fossa up to twice its size, to increase the surface area between the glenoid and the humeral head by up to one- quarter greater, and to absorb shock received by the joint.
Thereby, the glenoid labrum contributes to the stability of the glenohumeral joint [10,14,18]. In several studies, the long head of biceps tendons in patients with injuries of the rotator cuff or the glenohumeral ligaments, have been shown to play a big role in maintaining joint stability [19–21]. Common anatomical variations of the glenoid labrum that confuse diagnosis of SLAP lesions exist. For example, in 73% of normal shoulders, below the superior labrum-biceps tendon complex lies a sublabral recess
detected as a contrast media-filled region during magnetic resonance (MR) arthrogram interpretation; this sublabral recess can often lead to a false diagnosis of a labral tear [11,12,22]. Other common anatomical variations of the glenoid labrum are the Buford complex and the sublabral foramen (or sublabral hole). The Buford complex was first coined by Williams et al. [23] in 1994 and described as a
“cord-like” middle glenohumeral ligament conjoined to the anterosuperior labrum. The middle glenohumeral ligament originates from the superior labrum at the base of the long head of biceps tendon but is characterized by an absence of the labrum between the 12 and the 3 o’clock position on the glenoid (of a right shoulder); thus, the thick line representing this middle glenohumeral ligament, a normal variation, could be mistakenly taken as a pathological lesion by an inexperienced surgeon.
If inappropriate surgical actions are taken unnecessary pain or limitations in motion during shoulder abduction or external rotation may follow [12,15]. The sublabral foramen, another normal variation that must not be consumed with a SLAP lesion, refers to a small hole between the glenoid rim and labrum or underneath the long head of biceps tendon origin. In general, the hole appears just above the 3 o’clock position on the glenoid rim [12,24].
CLASSIFICATION
The most widely used classification system for SLAP lesions is Snyder’s classification that has identified 4 types of lesions [2,11]. Type 1 SLAP lesions were described as partial degeneration and wear of the superior labrum that occur mostly in middle-aged patients. But the shoulder remains stable in these patients because of the superior labrum remains strongly attached to the glenoid; as such, patients with type 1 SLAP lesions remain mostly asymptomatic. Type 2 SLAP lesions show a detachment of the superior labrum from the glenoid resulting in an unstable superior labrum-biceps tendon complex. Type 2 SLAP lesions were the commonest of all types being found in 41% of SLAP lesions assessed by Snyder et al.’s studies [2]. The lesions are of degenerative nature in type 2 SLAP lesions as that of type 1, but unlike type 1 the labrum is completely detached from the glenoid, which inevitably leads to the displacement of the superior labrum-biceps tendon complex when the shoulder moves. Further, it is important to differentiate between a displaced biceps- labrum anchor with the sublabral recess seen in a meni-
scus-type labrum [25]. Burkhart et al. and Morgan et al.
[3–5] introduced three distinct sub-groups of type 2 SLAP lesions: anterosuperior lesion, posterosuperior lesion, and combined anterior and posterior lesions.
As the base of the biceps is twisted, the torsional force travels from the biceps tendon base anteriorly (horizon- tally) and posteriorly (vertically) to the superior labrum, directly causing the labrum and the posterosuperior glenoid to separate. Not only can this cause a labral tear, but also the peeling of the labrum posteriorly—leading to the “peel-back” phenomenon.
Type 3 SLAP lesions are characterized by a bucket-handle tear of the labrum with intact long head of biceps tendon insertion. But sizable tears may displace the superior labrum intra-articularly and lead to symptoms. Type 4 SLAP lesions are like type 3 lesions but the bucket-handle tear of the superior labrum extends to the long head of biceps tendon and the long head of biceps tendon is partially torn;
part of the labrum is displaced and the remaining portion remains attached to the insertion principally keeps the structure functional. When Maffet et al. [6] realized that only 62% of all patients were classifiable into one of Snyder’s 4 classification types, they expanded their current classification system to include a total of 10 types (an additional 6 types were added): type 5 SLAP lesions are characterized by Bankart lesions on the superior labrum;
type 6 SLAP lesions are described as flap tears that goes across the biceps-labrum border; type 7 SLAP lesions are indicated by SLAP lesions that extend to involve the middle glenohumeral ligament; type 8 SLAP lesions involve type 2 SLAP lesions that has extended posteriorly to the 6 o’clock position of the posterior labrum; type 9 SLAP lesions are complete tears of the labrum from the glenoid rim; and finally, type 10 SLAP lesions involve a co-presentation of superior labral tear with a reverse Bankart lesion [25]. Thus, the surgical treatment is very much dependent on these concomitant pathologies; for instance, as types 5, 6, and 7 SLAP lesions are related to shoulder instability SLAP lesions must be treated and flap tears, if present, must be removed. Conversely, as types 8, 9, and 10 SLAP lesions involve labral detachment, treatment should focus on re-attachment of the labrum and the removal the flap tears, if present.
PATHOPHYSIOLOGY
The etiological basis of SLAP lesions can be roughly divided into two: a single trauma or repetitive micro-
traumatic injuries. A single trauma-induced SLAP lesions occurring by a single event leads to crepitation, mechanical defects such as catching or locking, and acute pain of the shoulder. Typically, forceful torsion in the anteroinferior direction or excessive abduction of the shoulder is the causes of the trauma [26]. Repetitive microtraumatic injuries-induced SLAP lesions are more common than trauma-induced ones in persons involved in overhead activity. The overhead motion demands a complex coordination of a combination of muscles for the efficient transmission of torsional energy from the legs to the torso, and from the torso to the upper extremities [27]. Wilk et al. [9] have reported that for this to occur efficiently, a fine balance between achieving the maximal external rotation through a flexible articular capsule whilst at the same time achieving sufficient stability that prevents shoulder dislocation when executing a wide ROM; this phenomenon is called the “thrower’s paradox.”
Past studies have reported various etiologies of SLAP lesions, and they often occur as a result of multiple factors [26]. In the early literature of SLAP lesions, it was reported that SLAP pathology occur during the follow- through phase of an overhead throw when the eccentric activity of the biceps brachii is high [1,10]. Conversely, another study has shown that the biceps brachii is at its peak activity at the deceleration phase of an overhead throw [28]. Not only has Digiovine et al. [29] reported that the contraction of the biceps brachii is only 44% of its maximal capacity during the follow-through phrase, but Kuhn et al. [30] also reported that the biceps-labrum complex tears occur during the late cocking phase rather than during deceleration phase; thus, proposing that neither the follow-through nor the deceleration phase is when the pathological event occurs. Two mechanisms for the SLAP pathology have been hypothesized: 1) Injury from repetitive, rotatory motions which cause excessive anterior to posterior traction of the labrum as the long head of biceps tendon twists [3]. 2) A “peel-back”
mechanism during which the humeral head and the long head of biceps tendon is pushed posteriorly when the shoulder is placed in abduction and in maximal external rotation. This movement, when repeated, produces a torsional force at the base of the biceps which causes a
“peel-back” of the biceps-labrum anchor, and thereby a SLAP lesion [3].
During pitching, another lesion that acts as a source of pain is the internal impingement of the shoulder, which is arthroscopically distinct from impingement syndromes
that lead to a lesion of the subacromial space. Internal impingement occurs when the sub-rotator cuff becomes stuck between the labrum and the humeral head during the late cocking phase of an overhead throw. Of note, SLAP lesions may facilitate the progression internal im- pingement; for example, Morgan et al. [4] reported that SLAP lesions with tractioned biceps induce internal im- pingement and that chronic type 2 SLAP lesions leads to increased posterosuperior instability and, thereby, injury to the lower rotator cuff.
When overhead athletes experience posteroinferior capsular contracture, excessive external rotation of the shoulder occurs and causes the anteroposterior cable to become imbalanced and the humeral head to displace in the posterosuperior direction. This places a torsional peel- back force on the biceps-labrum complex, which could induce a labral tear. As described, numerous etiologies of SLAP lesions have been reported; however, the likelihood of these etiologies acting in singularity is small. As single pathological, etiological events they are unlikely to explain not only the causes of SLAP lesions but also the related pathological findings that occur during a throwing motion [31].
HISTORY AND PHYSICAL EXAMINATION
The clinical diagnosis of SLAP lesions is difficult because of the atypical medical history and high rates of false positives from physical and radiological tests such as MR arthrographic imaging [10]. These false positives are contributed by the fact that in athletes most, rather than having a singular, discrete injury, have multiple injuries in various parts of the shoulder at the same time. As shoulder lesions of different origin may share similar clinical features, it is important to take accurate, detailed medical history and physical examination.
Athletes with SLAP lesions present with anterior shoulder pain and have difficulty performing forward elevation of the arms, leading to deceleration of arms [31–33]. During cocking phase of an overhead throw, patients with SLAP lesions often experience crepitation [33]. They often have co-pathologies such as partial tears of the rotator cuff, labral-capsular injuries, biceps brachii injuries, internal impingement, etc. Symptoms of SLAP lesions are night pain, muscle weakening, and instability [34]. In Mileski and Snyder’s study [35], they found that 29% of patients presenting with SLAP lesions had co-rotator cuff partial tears and 22% had co-Bankart lesions. Kim et al. [21]
found that type 2 SLAP lesions was most associated with other pathological lesions, the younger the patient the greater the instability, and lastly, in elderly patients, rotator cuff tears were often combined.
In overhead athletes with shoulder pain, physical examination to measure the ROM of the glenohumeral joint should be made. In supine position and scapula fastened, the external and internal rotations of the shoulder should be measured with the lateral shoulders in adduction and at 90o in abduction. Most athletes involved in overhead activity will show increased external rotation and decreased internal rotation of the affected shoulder [31]. Burkhart et al. [3] were first to term the condition, when compared to the contralateral arm, the internal rotation of the shoulder was at least 20o reduced as the “glenohumeral internal rotation deficit” or “GIRD”.
Even though the mechanisms behind this phenomena are unclear, many studies suggest a capsular or bone deformity-based mechanism [3,4,36]. Other physical examinations include the full can/empty can tests for rotator cuff strengths, the load shift test, the apprehension relocation test, the sulcus sign, and the jerk test for ante- rior instability [31].
For the diagnosis of superior labrum injuries speci- fically, physical examinations such as O’Brien active com- pression test, anterior slide test, compression rotation test, resisted supination external rotation test, Speed test, crank test, biceps load test II, and the major shear tests are used [37–40]. These physical examinations have high sensitivity but lack specificity, and none have been singled out over the rest for its accuracy to diagnose SLAP lesions [39,40]. Further, many studies on the sensitivity and specificity of these tests show mixed results. However, if in combination with strong clinical indications for SLAP lesions, results of physical examinations not only aid SLAP diagnosis but also help make a detailed analysis of the patient conditions and devise surgical plans. In sum, a detailed understanding of the patient’s medical history and physical examinations are important for the diagnosis and treatment of SLAP lesions.
IMAGING TECHNIQUES FOR SLAP LESIONS
MRI, especially MR arthrography, is the most effective tool for diagnosing SLAP lesions; MR arthrography shows a sensitivity and specificity of over 90% in the diagnosis of SLAP pathology [32]. X-rays can detect whether or not a lesion is there or not but not specifically that of a SLAP
lesion. Of the MR arthrograms, it is the coronal oblique view showing the space between the glenoid and labrum highlighted by contrast media that indicates a SLAP lesion (Fig. 1). And the presence of a ganglion cyst at the posterosuperior labrum is strongly indicative of SLAP pathology. However, MR arthrography has its pitfalls in that it often leads to false positive diagnosis. Especially, the Buford complex and the sublabral foramen, which are anatomic variations that commonly occur at the anterosuperior labrum-biceps tendon anchor, must be differentially diagnosed. Many overhead athletes find that they have SLAP lesions through MRI tests, but given that this does not necessarily mean they are symptomatic clinical signs should also be taken into account during diagnosis [10].
TREATMENT OF SLAP LESIONS
The mode of treatment for SLAP lesions remains con- troversial. At the early stages of SLAP lesions, i.e., those with unstable biceps-labrum complexes such as type 2 or type 4 SLAP lesions, it has been shown that surgical repair is more effective than simple excision. But with recent changes in perspective of SLAP lesions as more of a degenerative lesion brought about by age and labor, the decision to adopt surgical methods in non-athletes older than 40 is become more obscure. Degenerative changes cause above-average labral movement, which means a repair may not be effective in those under 40 years of
age as it does not address the underlying cause; as such, SLAP lesions in over 40s is often left unrepaired. Recently, a comparative study on type 2 SLAP lesions found that although most patients showed a good clinical outcome after surgery, when the outcomes of athletes were compared to those of non-athletes, athletes showed a less promising outcome after surgical treatment [41].
Studies on the conservative treatment of SLAP lesions are rarer than those of surgical treatment. Edwards et al.
[42] who conservatively treated their sample of athlete patients with SLAP lesions found that 49% of patients exhibited resolution of pain and a successful, functional outcome, but only 67% of these athletes were able to achieve pre-injury level of overhead ability and return to play.
One of the important considerations for the treatment of SLAP lesions is to decide on the mode and time of intervention. With athletes especially, the time consumed by conservative treatment is unrealistic and a prolonged period of treatment, whether due to a long treatment period or rehabilitation period, may greatly influence how smooth or successful the athlete’s transition back to sports is. Asides clinical decisions, sports season, for younger athletes, their education, or being scouted are factors that make cessation of activity an extremely unfavorable option; thus, the individual situation of the patients cannot be overlooked in the decision making process.
NON-SURGICAL TREATMENTS
As with other lesions of the shoulder, conservative treat- ments can be considered in advance of any surgical treat ments for SLAP lesions. If symptoms are trivial and pro gression of the lesion is of early stages, conservative treatment, such as rest, physiotherapy, and rehabilitation, may be the more appropriate measure that can avoid triggering unnecessary pain and pathology. For example, symptoms or pain induced by posteroinferior capsular contracture is known to effectively resolve by conservative means [5,43].
An example of conservative treatment is a method called “sleeper stretch” where the patient lies on one side, or sidelying, with the elbow and shoulder joints in 90o of flexion; the shoulder is manually rotated internally to pro- mote upper body cross exercise. Sleeper stretch is effective for the treatment of posteroinferior capsular contracture [5,44]. Importantly, conservative treatment must achieve stability of the scapula and the structures surrounding Fig. 1. Magnetic resonance arthrogram shows the presence of contrast
medium in the place of a superior labrum anterior to posterior lesion (arrow).
the rotator cuff prior to the athlete’s return to play, and must be executed in a controlled manner so that muscle exercises are performed without inducing pain [3,45].
In patients whose symptoms persist, Wilk et al. [9]
imple mented a rehabilitation program of 4 levels aimed at strengthening the dynamic stability of the rotator cuff muscles and the stability of the upper extre mities. Other conservative methods that supplement rehabi litation and physiotherapy are NSAID admini stration, which reduce inflammation, adrenocor tico steroid hormone injection therapy, cold pack, etc. [46]. Despite such efforts, around 10% of athletes, especially those who have had long symptomatic periods, with severe GIRD, or with co- type 2 SLAP lesions, can still remain non-responsive to treatment [3].
SURGICAL TREATMENTS
Depending on patients’ circumstances or if they are non- re sponsiveness to conservative treatments, surgical treat- ment of the shoulder be considered. For the arthroscopic method, a common surgical intervention of SLAP lesion, neither the “gold standard” position of the patient nor the portal position is set. Thus, it is largely dependent on the surgeon’s discretion and experience. In general, however, the lateral decubitus or the beach chair position is chosen, and the anterior, the anterolateral or trans-tendon portal, or the posterior portal are traditionally used (Fig. 2).
Under general anesthesia, the patient is assessed through
physical examination after which surgery is performed.
During arthroscopic repair of SLAP lesions, one of the most important considerations is the differentiation of SLAP lesions with its anatomic variants such as the Buford complex or the sublabral foramen. If mistaken as a pathology, inappropriate treatment may lead to avoidable complications [12,15].
The approach for surgical repair differs depending on the type of SLAP lesion. Debridement is sufficient for type 1 SLAP lesions, a suture anchor attaches the labrum back to the glenoid in type 2 SLAP lesions, whereas the choice of treatment largely depends on the size and stability of the lesions for type 3 and 4 SLAP lesions; if small and stable, the lesion is excised, and if large and unstable, it is repaired [15].
Arthroscopic examination of the labrum requires inser- tion of a probe, which induces at least a 5-mm displace- ment of the labrum. An arthroscopic observation of granulation tissue is indicative of SLAP pathology (Fig. 3).
An example of a process commonly employed to repair SLAP lesions is as follows: 1) soft tissue is removed using a shaver from the superior glenoid rim, 2) after which a burr is used to induced bleeding at the bone surface (Fig. 4), and 3) then the repair is performed following the glenoid rim (Fig. 5) [47]. When suture anchors are used, they are inserted at a 45º angle from the articular surface [10]. Cadaveric studies by Lehtinen et al. [48] have shown that most bone stock can be attained from the uppermost superior glenoid rim. During surgical interventions in
Fig. 2. Photograph of surgical field shows arthroscopic portals with the patient in the lateral decubitus position (A, anterior portal; AL, anterolateral portal; P, posterior portal).
Fig. 3. Observation of the superior labrum anterior to posterior lesion using a probe that was inserted through an anterior portal (G, glenoid;
SL, superior labrum).
athletes, unlike non-athletes, it is essential to avoid excess strain during repair and to achieve the best outcome with the minimum of repair, so athletes can swiftly return to play and achieve pre-injury level of overhead abilities [15].
Unsurprisingly, as SLAP lesions are known to have multiple etiologies, Jobe [49] founds that slap lesions rather than being present alone, are often found in combination with pathologies in posterosuperior labrum, rotator cuff, greater tuberosity, inferior glenohumeral ligament complex, and posterosuperior glenoid. Thus, taking heed of and appropriate surgical or conservative action on co- pathologies in the surrounding structural elements are important for a better prognosis.
CONCLUSION
Repetitive microtraumatic injuries to SLAP eventually lead to the tear of the superior labrum-biceps complex and to SLAP lesions. When making the diagnosis, it is important to observe indications for SLAP lesions from both imaging results, such as MR arthrography, and clinical symptoms
[10]. Developments in surgical tools and fixation devices and increased understanding in anatomical structures have led to surgical repair of SLAP lesions as being the gold standard of treatment. However, with respect to the surgical treatment of overhead athletes, such as baseball players, age and level of activity are factors that must be takin in account. Even though numerous reports of patients with pre-injury levels of overhead throwing abilities after surgical repair exemplifies its effectiveness, currently, many reports criticize that some of the known, supposedly beneficial prognostic factors for a successful surgical outcome are over-rated or over-estimated. Thus, all indications and contraindications should be carefully considered before making a decision for surgical inter- vention [50].
CONFLICT OF INTEREST
No potential conflict of interest relevant to this article was reported.
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