MR imaging in sports-related glenohumeral instability
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Sports-related shoulder pain and injuries represent a common problem. In this context, glenohumeral instability is currently believed to play a central role either as a recognized or as an unrecognized condition. Shoulder instabilities can roughly be divided into traumatic, atraumatic, and microtraumatic glenohumeral instabilities. In athletes, atraumatic and microtraumatic instabilities can lead to secondary impingement syndromes and chronic damage to intraarticular structures. Magnetic resonance (MR) arthrography is superior to conventional MR imaging in the diagnosis of labro-ligamentous injuries, intrinsic impingement, and SLAP (superior labral anteroposterior) lesions, and thus represents the most informative imaging modality in the overall assessment of glenohumeral instability. This article reviews the imaging criteria for the detection and classification of instability-related injuries in athletes with special emphasis on the influence of MR findings on therapeutic decisions.
KeywordsShoulder MR Shoulder dislocation Shoulder injuries Magnetic resonance MR arthrography
In the last decade, understanding of the biomechanics and pathophysiology of the athletic shoulder has significantly improved. Especially in overhead athletes and throwers several pathologic mechanisms have been identified which could not be explained by the traditional concepts of instability and impingement. With an expanded definition, glenohumeral instability is now believed to play the crucial role in the etiology of the painful athletic shoulder. Instability related to sports is not infrequently unrecognized and initiates a vicious circle of secondary impingement, muscular dysfunction, and damage to intraarticular structures that can be devastating and may end the athlete’s career [1, 2, 3, 4, 5].
Mnemonics for classification of glenohumeral instability
Inferior capsular shift
(Rotator) Interval closure
Pattern of Lesions
Rotator cuff lesions
Rotator cuff lesions
Large capsular volume
Rotator cuff lesions
Acute trauma (dislocation)
Magnetic resonance (MR) imaging plays an important role in the diagnostic work-up of the painful athletic shoulder and with advanced techniques has in many instances already replaced diagnostic arthroscopy. This article discusses the role of MR imaging and MR arthrography in the context of the most common forms of sports-related glenohumeral instability and presents the typical MR arthrographic appearance of their corresponding intraarticular lesions and patterns of injury.
The non-enhanced MR imaging protocol performed after acute shoulder dislocation includes a coronal oblique T1-weighted SE sequence, coronal oblique and transverse intermediate weighted TSE sequences with fat-saturation, and a sagittal oblique T2-weighted TSE sequence with the same geometric parameters as mentioned above.
Traumatic glenohumeral instability
Traumatic glenohumeral instability is typically initiated by a specific traumatic event, followed by other episodes of dislocation or subluxation with a unidirectional pattern [2, 7]. In the vast majority of athletes traumatic instability occurs in an anteroinferior direction when a sudden force overwhelms the anterior capsular structures while the athlete’s arm is in an abducted, externally rotated, and extended position . The resulting combination of injuries represents the source of chronic instability, particularly those involving the inferior glenohumeral ligament (IGHL), which, according to the current opinion, is the most important passive stabilizer of the shoulder joint. The IGHL is formed by an anterior and a posterior band, which represent condensations of the capsule running from the inferior labrum to the humeral neck. The anteroinferior labrum and the anterior band of the IGHL together form the anteroinferior labro-ligamentous complex. The labrum is thought to serve more as an insertion site for the IGHL than to provide stability to the glenohumeral joint by deepening the glenoid fossa [13, 14, 15]. Although generally common in sports, this type of instability is rarely observed in throwers or overhead athletes, but, if present, can cause secondary damage to the rotator cuff and the superior and posterior labrum .
The high diagnostic accuracy of MR arthrography in the detection of labro-ligamentous lesions has been demonstrated in several studies. MR arthrography identifies labral tears with a sensitivity of 88–96% and a specificity of 91–98% [14, 16, 17, 18, 19]. For the detection of lesions of the superior, middle, and inferior glenohumeral ligaments, Chandnani and co-workers reported sensitivities and specificities of 88–100% . The sensitivities and specificities of unenhanced MR imaging for the diagnosis of labro-ligamentous injuries vary widely in the literature. Although a direct comparison with MR arthrography has not yet been performed in a larger series, we regard the role of standard MR imaging in the diagnostic work-up of shoulder instability as questionable, particularly with a view to chronic cases and the depiction of associated pathology [7, 9, 14, 21, 22]. The advantages of MR arthrography are obvious and result from capsular distension with separation of anatomic structures and improved delineation of tears following entrance of contrast media [8, 9]. MR arthrography thereby allows more confident distinction of pathologic conditions from the common anatomic variations of labral morphology as well as from congenital variants of the glenohumeral ligaments and the labro-ligamentous unit, such as the Buford complex [7, 9, 14, 23, 24, 25, 26]. Furthermore, the imaging appearance of Bankart variant lesions has been described only with MR arthrography [7, 14, 27, 28].
Few studies have directly compared MR arthrography and computed tomography (CT) arthrography in the diagnosis of labro-ligamentous injuries. The results suggest that, with the exception of bony changes, CT arthrography is less sensitive than MR arthrography [5, 16]. However, CT arthrography with the use of new multidetector techniques has not yet been fully evaluated in the shoulder. First results indicate that due to its capability of isotropic data acquisition it will probably perform equivalent to MR arthrography [8, 26].
Bony Bankart lesion
The GLAD (glenolabral articular disruption) lesion (Fig. 2e), as described by Neviaser is a superficial tear of the anteroinferior labrum in combination with an articular cartilage lesion of the anterior inferior quadrant of the glenoid. The injury is thought to result from glenohumeral impaction while the arm is abducted and externally rotated. Persistent anterior shoulder pain after a fall onto an outstretched arm is the most common clinical presentation, and arthroscopic debridement has been proposed as the treatment of choice .
The Hill-Sachs defect represents a compression injury of the posterolateral humeral head which develops during anteroinferior dislocation as the relatively large and soft humeral head impacts against the comparatively small and hard bony glenoid . The incidence of the lesion at arthroscopy varies considerably from 47 to 100% among different series of patients with first-time traumatic dislocations [31, 32, 44]. The depth and size of a Hill-Sachs lesion, ranging from shallow chondral defects to deep osteochondral impaction fractures, is thought to reflect the tightness of the joint capsule . In athletes with hyperlaxity at the time of the first shoulder dislocation, the humeral injury therefore typically is small or absent. Osteochondral Hill-Sachs defects that involve less than one third of the circumference of the humeral head are usually regarded as prognostically irrelevant. Larger lesions, especially if oriented with their long axis parallel to the glenoid, can engage the anterior corner of the glenoid in abduction and external rotation and thus lead to repeated subluxations or redislocations (“engaging” Hill-Sachs defect) .
Atraumatic glenohumeral instability
Atraumatic glenohumeral instability is typically multidirectional and usually evident in individuals with congenital hypermobility syndrome. The diagnosis is predominantly based on the clinical examination, which uncovers bilateral affection of the shoulders in association with generalized hyperlaxity of ligaments and joints [1, 2, 35, 46]. The increased baseline laxity of the shoulder seen in athletes with generalized hypermobility is advantageous for several types of sports, but at the same time harbors a high risk of long-term injury with damage of intra- and periarticular structures [1, 2]. If conservative management fails, multidirectional instability is usually treated surgically by inferior capsular shift and closure of the rotator interval .
Microtraumatic glenohumeral instability
Microtraumatic glenohumeral instability is thought to result from chronic traumatization of the capsular structures in throwers and overhead athletes, such as tennis players, swimmers, and handball players. In contrast to atraumatic glenohumeral instability, microinstability is typically seen unilaterally only in the dominant shoulder of the athlete. Whereas repetitive abduction and external rotation cause microtrauma of the anterior capsule and thus can provoke anterior instability, repetitive overhead activity with abduction, flexion, and internal rotation might give rise to posterior microinstability as a result of injury to the posterior labro-ligamentous elements [4, 7, 9, 35, 46].
Structural abnormalities consecutive to microtraumatic glenohumeral instability can be depicted by MR arthrography and include laxity of the anterior or posterior capsule, labral injuries ranging from degeneration and fraying to tearing and detachment, SLAP (superior labral anteroposterior) lesions, and tears of the rotator cuff caused by secondary impingement .
Posterosuperior glenoid impingement (PSI)
PSI is a form of internal impingement which represents a common problem in throwers and overhead athletes, presenting with acute or chronic posterior shoulder pain [4, 5, 47, 48]. The basic observation was reported by Walch, who described impingement between the articular side of the supraspinatus tendon and the posterosuperior edge of the glenoid evident in abduction and external rotation . In throwers and overhead athletes, PSI can lead to a typical pattern of injuries, the so-called “kissing lesions”, which includes corresponding lesions of the undersurface of the rotator cuff, the posterosuperior labrum, the greater tuberosity, and the superior bony glenoid [47, 48, 50, 51, 52]. The development of PSI has been attributed to chronic injury (repetitive stretching) of the anterior capsular structures, particularly the IGHL, with consecutive anterior microinstability, which causes anterior subluxation of the humeral head in abduction and external rotation during overhead movements, and thus allows excessive contact between the rotator cuff and the posterosuperior glenoid [47, 48]. However, this theory is not generally accepted. Other authors described a contracture of the posteroinferior capsule and a posterior SLAP lesion as the essential lesions for the development of PSI in throwers . Although the basic mechanism is still subject to discussion, the high coincidence of PSI and SLAP lesions is undoubted. Furthermore, there is apparently a huge overlap of clinical symptoms in athletes with SLAP lesions, PSI, or both. It is important to stress that contact between the undersurface of the rotator cuff and the posterosuperior glenoid, as seen on arthroscopy, is not pathologic per se. Posterosuperior glenoid impingement should only be diagnosed if this contact is associated with clinical symptoms and corresponding lesions of the involved anatomic structures [2, 13, 51, 52]. Conservative treatment is usually suited in athletes with minor structural abnormalities, whereas surgical debridement and repair (eventually in combination with capsular plication) are indicated in the presence of relevant rotator cuff and labral lesions.
- Type 1:
degenerative fraying of the superior labrum;
- Type 2:
avulsion of the superior labrum and biceps anchor from the glenoid;
- Type 3:
bucket-handle tear of the superior labrum with preserved biceps anchor;
- Type 4:
bucket-handle tear of the superior labrum involving the long head of biceps tendon .
This classification has been expanded with several further types of lesions, which mainly represent combinations of the most common form, the SLAP type 2 lesion, with other injuries of the labrum, medial glenohumeral ligament, or rotator cuff. However, only the Snyder classifications have found wide acceptance, and most institutions categorize these injuries as type 1–4 with or without asscociated lesions. Whereas type 1 and 2 lesions are typically caused by repetitive torsion of the biceps anchor (the so-called “peelback mechanism”) in throwers and overhead athletes, types 3 and 4 lesions are thought to occurr more often after a fall onto an outstretched arm or onto a flexed elbow [3, 55, 56]. Furthermore, type 2 lesions are frequently observed in athletes with traumatic anterior shoulder instability, where they develop in association with lesions of the anteroinferior labro-ligamentous complex (most often a classic Bankart lesion). In these cases, the labro-ligamentous avulsion can be considered as the main lesion, with the SLAP lesion being an associated injury . Surgical treatment is indicated in all types of SLAP lesions except type 1 lesions which are usually of no clinical relevance. Since type 2 and 4 lesions impair the stabilizing function of the biceps insertion and therefore can provoke glenohumeral instability, secondary impingement, and rotator cuff lesions, they are commonly treated by refixation. Type 3 bucket-handle tears are usually not surgically reattached but treated by simple debridement [55, 56].
MR arthrography has proved to be superior to conventional MR imaging with regard to the identification of SLAP lesions and has been shown to be reliable in assessment of the stability of the biceps anchor and the detection of associated injuries [55, 57, 58, 59]. However, its ability to correctly classify the different types of lesions is limited .
Sports-related glenohumeral instability is a complex and in many aspects still controversial subject. MR imaging can play an important role in evaluation of the athlete’s shoulder if it aims at providing essential information for therapeutic decisions at eye level with diagnostic arthroscopy. Therefore, the radiologist should be familiar with the mechanisms and classification of injuries as well as the advantages and limitations of his examination techniques. At present, MR arthrography represents the best evaluated and most informative imaging technique for the assessment of shoulder pathology in many aspects and thus, appears to be most valuable for the diagnostic work-up of glenohumeral instability and unclear shoulder pain in athletes.
We thank Darko Leko for assistance in preparation of schematic drawings.
- 6.Matsen FA, Lippit SB, Sidles JA, Harryman DT (1994) Practical evaluation and management of the shoulder. Saunders, Philadelphia, pp 59–109Google Scholar
- 26.Waldt S, Metz S, Burkart A, Mueller D, Bruegel M, Rummeny EJ, Woertler K (2006) Variants of the superior labrum and labor-bicipital complex: a comparative study in shoulder specimen using MR arthrography, multi-slice CT arthrography, and anatomic dissection. Eur Radiol 16:451–458PubMedCrossRefGoogle Scholar
- 29.Bankart ASB (1938) The pathology and treatment of recurrent dislocation of the shoulder. Br J Surg 26:23–39Google Scholar
- 36.Perthes G (1906) Über Operationen mit habitueller Schulterluxation. Deutsch Z Chir 85:199–227, [Article in German]Google Scholar
- 43.Lintner SA, Speer KP (1997) Traumatic anterior glenohumeral instability: the role of arthroscopy. J Acad Orthop Surg 5:233–239Google Scholar
- 51.Kaplan LD, McMahon PJ, Towers J, Irrgang JJ, Rodowsky MW (2004) Internal impingement on magnetic resonance imaging and arthroscopic evaluation. Arthroscopy 7:701–704Google Scholar