Management of Failed Instability Surgery: How to Get It Right the Next Time

Traumatic anterior shoulder dislocations are the most frequent type of joint dislocation and affect approximately 1.7% of the general population. The literature supports the consideration of primary stabilization in high-risk patients because of reported recurrences as high as 80% to 90% with nonoperative treatment regimens. Successful stabilization of anterior glenohumeral instability relies on not only good surgical techniques but also careful patient selection. Failure rates after open and arthroscopic stabilization have been reported to range from 2% to 8% and 4% to 13%, respectively. Recurrent shoulder instability leads to increased morbidity to the patient, increased pain, decreased activity level, prolonged time away from work and sports, and a general decrease in quality of life. This article reviews the potential pitfalls in anterior shoulder stabilization and discusses appropriate methods of addressing them in revision surgery.

Pathoanatomy

The stability of the glenohumeral joint relies on the balance maintained by its static and dynamic stabilizers. Dynamic components include the rotator cuff muscles, and the critical static components include the glenolabral complex and capsuloligamentous structures. The labrum increases the surface area and depth of the glenoid socket by as much as 50%, thereby improving osseous conformity. Detachment of the anteroinferior labrum with its attached inferior glenohumeral ligament complex denotes the classic Bankart lesion and is the most common pathologic finding associated with anterior shoulder instability. With recurrent episodes of instability, elongation of the anteroinferior and inferior capsule has been shown to occur, further adding to the underlying pathology of this clinical entity.

In addition to soft tissue injury, recurrent instability can facilitate progressive bony injury. Sugaya and colleagues identified an osseous Bankart lesion in 50% of patients with traumatic anterior shoulder instability. Although most of these fragments were less than 10.6% of the glenoid fossa, they also noted that an additional 40% of patients showed blunting on oblique radiographs, suggestive of mild erosion. Griffith and colleagues reported similar results, with a 41% incidence of glenoid bone loss in first-time anterior shoulder dislocators. This condition increased to 86% in recurrent dislocators, and the severity of the bone defect significantly correlated to the number of dislocations.

The clinical applicability of these findings was characterized by Itoi and colleagues, who elucidated the minimum sized defect that led to clinical instability after a Bankart repair. In a cadaveric study they showed that after a Bankart repair, the capsular structures maintained stability of the joint up to a 21% (6.8 mm) anteroinferior glenoid defect. With bony defects greater than 21%, the shoulder showed persistent instability with internal rotation, and experienced limited external rotation after Bankart repair ( Fig. 1 ).

Increasing anteroinferior glenoid bone loss has been associated also with increased contact pressures. Greis and colleagues showed in a cadaveric study that a 30% glenoid bone defect led to a 41% decreased articular contact area of the entire glenoid and a 100% increase in mean contact pressures. These findings may have implications in the development of postoperative arthritis, and potentially support the findings of Buscayret and colleagues that the presence of osseous glenoid rim lesions is a risk factor in the development of arthritis, and that the development of postoperative arthritis correlates with an increased number of preoperative dislocations.

In patients with anterior shoulder instability, bony lesions are not limited to the glenoid but frequently also affect the humeral head. The classic Hill-Sachs lesion, in which the posterolateral aspect of the anteriorly dislocated head impacts the anterior glenoid rim, occurs in up to 90% of primary dislocators, 100% of patients with recurrent instability, and 40% of patients with recurrent anterior shoulder subluxations ( Fig. 2 ). Although lesions involve less than 20% of the articular surface and are considered clinically insignificant, those larger than 20% to 30% may be relevant contributors to recurrent instability.