**4. Type of associated pathology**

30 Modern Arthroscopy

depth of the concavity. Because the size of the glenoid is limited compared with the humeral head, even a relatively small bone loss may reduce considerably the surface area for articulation and consequently compromise stability. A bone loss that exceeds 20% of the glenoid surface is considered critical for the recurrence of instability (Burkhart & De Beer,

The labrum is a fibrocartilaginous structure attached to the glenoid rim. It functions to increase the anteroposterior and superoinferior depth of the glenoid and the surface contact area for the humeral head. Specifically, it increases the concavity of the glenoid up to 9mm in the superior-inferior direction and the anteroposterior depth to 5mm (Howell et al, 1988). Labral resection reduces resistance to translation by 20% (Lippitt & Matsen, 1993). The labrum also provides an attachment site for the glenohumeral ligaments. Two types of labral attachments to the glenoid have been described. The first, around the periphery through a fibrocartilaginous transition zone, which creates mobility along the central border similar to the knee meniscus. The second is securely attached both peripherally and centrally. The anteroinferior attachment of the labrum to the glenoid is normally tight. On the contrary, the superior attachment inserts directly into the biceps tendon distal to the insertion on the supraglenoid tubercle, it is loose and anatomically variant. Isolated lesions of the superior labrum do not result in instability. However, if the biceps insertion is also destabilized,

The glenohumeral capsuloligamentous system provides a restraint to excessive translation in varying positions of the joint. In particular, the anterior band of the inferior glenohumeral ligament (AIGHL) attaches to the anteroinferior labrum and primarily resists anteroinferior

The rotator cuff compresses the humeral head into the glenoid throughout the range of motion. An association between undersurface rotator cuff tears and instability has been described (Jobe & Bradley, 1989). The rotator interval (RI), between the leading edge of the supraspinatus and the superior edge of the subscapularis, has also been implicated in glenohumeral instability. Closure of a large defect in the RI has been shown to decrease inferior instability. There may be an inverse relationship between the size of the RI and the superior glenohumeral ligament (SGHL) contributing to the instability (Nobuhara & Ikeda,

The natural history of anterior shoulder instability has been studied extensively and recurrence has been correlated with a younger age at the time of first dislocation. In a large cohort of 255 patients with primary traumatic anterior dislocation, who were treated with a sling for 4 weeks, there was a 55% incidence of an additional episode of instability within 2 years of the initial traumatic dislocation. Furthermore, 66% of the patients had an episode of instability within 5 years (Robinson et al, 2006). In another study, 324 shoulders were followed for at least 10 years after primary anterior dislocation. Ninety-four percent of the patients younger than 20 years had a recurrence compared with 14% of those older than 40 years. The patients without shoulder immobilization had a 70% recurrence rate that decreased to 26% to 46% when immobilized for 1 to 3 weeks (Rowe, 1956). These findings suggest that younger patients with primary anterior dislocations have a significantly higher rate of recurrence. The effectiveness of rehabilitation is still in debate. In a study evaluating the effect of rehabilitation, 115 patients with traumatic and atraumatic recurrent shoulder subluxation,

2000; Tauber et al, 2004).

1987).

significant translation occurs (Pagnani et al, 1995).

**3. Natural history of anterior instability** 

translation in the abducted externally rotated shoulder position.

A **Bankart lesion** is the commonest sequel of an anterior dislocation and the main cause of instability. It is defined as a labral complex avulsion from the scapular periosteum. It usually includes some degree of capsular stretch and injury. When the lesion involves a fracture of the antero-inferior glenoid rim in addition to the soft tissue avulsion it is referred to as **bony Bankart** (Fig 1).

Fig. 1. A three-dimensional reconstruction CT-image demonstrating a bony-Bankart lesion.

**Humeral avulsion of glenohumeral ligaments (HAGL)** occurs when the capsuloligamentous structures are avulsed and torn off the humeral head and not the glenoid. An external rotation force in addition to hyperabduction commonly results in this lesion in contrast to a hyperabduction and impaction force that may produce a Bankart lesion (Matsen et al, 2006). The incidence of HAGL lesions after a traumatic dislocation has been reported at 39% (Bokor et al, 1999). A bony HAGL lesion occurs when the glenohumeral ligament is avulsed along with a bone fragment of the humeral head (Oberlander et al, 1996).

Arthroscopic Treatment of Recurrent Anterior Glenohumeral Instability 33

Fig. 3. A transverse plane CT image demonstrating a large Hill-Sachs lesion of the humeral

Type 1 Fraying of the anterosuperior labrum Type 2 Superior labrum-biceps complex

intact biceps anchor Type 4 Bucket-handle tear of the labrum with detachment of the biceps complex Type 5 Bankart lesion continues superiorly and

detachment from glenoid rim Type 3 Bucket-handle tear of the labrum with an

Type 6 Unstable flap tear of the labrum with an unstable biceps complex insertion

Type 7 Labrum-biceps complex separation

ligament

Table 1. Maffet classification of SLAP lesions (modified Snyder).

Fig. 4. A type II SLAP lesion as seen during arthroscopy.

includes separation of the biceps complex

extending beneath the middle glenohumeral

head.

**Anterior labral periosteal sleeve avulsion (ALPSA)** is a soft-tissue or bony Bankart lesion that has healed in a medially displaced position on the glenoid rim and therefore, does not restrain adequately the anterior translation of the humeral head (Fig 2). In this case, the avulsed periosteum has not raptured, causing medial and inferior displacement of the labroligamentous structures (Neviaser, 1993).

Fig. 2. An ALPSA lesion as seen from the anterosuperior arthroscopic portal. The labrum and periosteum have been avulsed and displaced medially.

A **Perthes lesion** is an incomplete avulsion without displacement of the antero-inferior labrum with a medially striped but intact periosteum.

**Glenoid labral articular disruption (GLAD) lesion** occurs when there is a defect in the articular cartilage of the anteroinferior glenoid in addition to the labral tear. The torn labrum I usually not fully detached from the glenoid and therefore, the predominant symptom is this case is not instability but pain.

A **Hill-Sachs lesion** is an impression fracture at the posterosuperior aspect of the humeral head that results from its impact on the glenoid rim when the humeral head dislocates anteriorly (Fig 3). They occur at 47 to 80% of anterior dislocations and in almost all cases of recurrent instability. If the posterolateral humeral head engages the anterior glenoid when abducted and externally rotated the Hill-Sachs lesion is defined as engaging (Burkhart & De Beer, 2000). The size and location of the defect mainly determine the likelihood of engagement. Although usually insignificant, in patients with glenoid bone loss a Hill-Sachs lesion can become more significant and engage the glenoid with much less force and anterior translation than those without glenoid bone loss.

A **superior labrum anterior posterior (SLAP)** lesion includes a spectrum of pathologic conditions of the superior labrum that may extend to the biceps root (Fig 4). Classification of these lesions was extended by Maffet et al to include 7 subtypes (Table 1). Type II tears are the commonest in most large series. On average, 40% of patients with Bankart lesions have an additional type II SLAP lesion (Hantes et al, 2009). SLAP lesions have been associated with glenohumeral stability. Forty-three percent of patients with SLAP lesions were found to have increased humeral head translation on examination under anesthesia (Maffet et al, 1995).

**Anterior labral periosteal sleeve avulsion (ALPSA)** is a soft-tissue or bony Bankart lesion that has healed in a medially displaced position on the glenoid rim and therefore, does not restrain adequately the anterior translation of the humeral head (Fig 2). In this case, the avulsed periosteum has not raptured, causing medial and inferior displacement of the

Fig. 2. An ALPSA lesion as seen from the anterosuperior arthroscopic portal. The labrum

A **Perthes lesion** is an incomplete avulsion without displacement of the antero-inferior

**Glenoid labral articular disruption (GLAD) lesion** occurs when there is a defect in the articular cartilage of the anteroinferior glenoid in addition to the labral tear. The torn labrum I usually not fully detached from the glenoid and therefore, the predominant symptom is

A **Hill-Sachs lesion** is an impression fracture at the posterosuperior aspect of the humeral head that results from its impact on the glenoid rim when the humeral head dislocates anteriorly (Fig 3). They occur at 47 to 80% of anterior dislocations and in almost all cases of recurrent instability. If the posterolateral humeral head engages the anterior glenoid when abducted and externally rotated the Hill-Sachs lesion is defined as engaging (Burkhart & De Beer, 2000). The size and location of the defect mainly determine the likelihood of engagement. Although usually insignificant, in patients with glenoid bone loss a Hill-Sachs lesion can become more significant and engage the glenoid with much less force and

A **superior labrum anterior posterior (SLAP)** lesion includes a spectrum of pathologic conditions of the superior labrum that may extend to the biceps root (Fig 4). Classification of these lesions was extended by Maffet et al to include 7 subtypes (Table 1). Type II tears are the commonest in most large series. On average, 40% of patients with Bankart lesions have an additional type II SLAP lesion (Hantes et al, 2009). SLAP lesions have been associated with glenohumeral stability. Forty-three percent of patients with SLAP lesions were found to have increased humeral head translation on examination under anesthesia (Maffet et al,

and periosteum have been avulsed and displaced medially.

labrum with a medially striped but intact periosteum.

anterior translation than those without glenoid bone loss.

this case is not instability but pain.

1995).

labroligamentous structures (Neviaser, 1993).

Fig. 3. A transverse plane CT image demonstrating a large Hill-Sachs lesion of the humeral head.


Table 1. Maffet classification of SLAP lesions (modified Snyder).

Fig. 4. A type II SLAP lesion as seen during arthroscopy.

Arthroscopic Treatment of Recurrent Anterior Glenohumeral Instability 35

external rotation it is highly likely that there exists an engaging hill-Sachs lesion or osseous glenoid defect. Similarly, patients with engaging Hill-Sachs lesions report episodes of

Routine radiographic imaging of the shoulder should include a true anteroposterior, axillary and scapular-Y views. Hill-Sachs lesions can be best appreciated on the anteroposterior view in internal rotation and the notch view (Hall et al, 1959). Avulsion fractures and glenoid bone deficiencies can be visualized with the Velpeau or West point axillary views (Rokous et

Advanced imaging has offered an improved ability to evaluate soft tissue lesions as well as glenohumeral deficiencies following shoulder dislocation. MRI has become the gold standard in evaluating glenohumeral instability demonstrating a high accuracy for detecting labral tears using noncontrast, enhanced imaging techniques (Ng et al, 2009). MR arthrography, however, has been found to present the highest sensitivity in detecting labral pathology compared with plain MRI and CT arthrography (Chandnani et al, 1993). It also achieved the best visualization of the inferior glenohumeral ligament and labrum. Both MRI and MR arthrography can also be helpful in evaluating bone loss. However, recently volume-rendering three-dimensional CT scans have offered a highly accurate method of measuring glenoid deficiencies and Hill-Sachs lesions. The humeral head can be digitally subtracted to allow for preoperative measurement of the inferior glenoid surface and the percentage of bone missing (Fig 5). Glenoid bone defects occur along a line parallel to its long axis. The inferior two thirds of the glenoid have been described as a well-conserved circle and the amount of bone missing is assessed in respect to surface area loss of the circle. Glenoid bone loss of between 6 to 8 mm of the anteroposterior diameter corresponds to 20- 25% of the surface of the inferior glenoid. In a similar fashion, the extent and morphology of

Fig. 5. Volume-rendering 3D reconstructed image of a cadaveric shoulder before (left image) and after (right image) artificially creating a glenoid bone defect. The surface area of the

instability in the midrange of shoulder abduction and external rotation.

a Hill-Sachs lesion can be evaluated to assess the degree of engagement.

inferior glenoid is being measured.

**5.3 Imaging** 

al, 1972).
