Conservative treatment for a minimum of 6 months is almost universally recommended. Activity modification and physical therapy, with particular focus on dynamic muscular stabilizers of the shoulder, have been shown to result in significant improvement in many patients [12, 32, 53, 54]. Elements of scapular dyskinesia or protraction can be addressed with a periscapular strengthening regimen. For patients with symptoms due to GIRD, the “sleeper stretch” has been shown to be extremely effective in avoiding progression of symptoms or surgery. To perform this stretch, the patient lies on the injured side with the staple stabilized against a wall, the shoulder and elbow each flexed to 90°. The contralateral, nondominant arm applies passive internal rotation force to the wrist [22]. Nevertheless, some patients will not improve with therapy alone. Burkhead et al. showed that only 16 % of patients with traumatic posterior instability improved with therapy, versus nearly 80% resolution in patients with atraumatic instability [8, 53].

Options for operative treatment of posterior instability are divided into two categories, based on the underlying type of lesion causing the instability. Procedures to correct or supplement osseous deficiencies of the glenoid or humerus address engaging reverse Hill-Sachs lesions, excessive glenoid retroversion, glenoid hypoplasia, or posterior glenoid deficiency. The other subgroup is procedures to correct soft tissue injuries of the rotator cuff or posterior capsulolabral complex.

Arthroscopic procedures for posterior instability have become the standard of care in the absence of severe bone deficiency. Surgical techniques address a spectrum of pathology in posteriorly unstable shoulders (Figs. 5.6, 5.7, and 5.8). The authors prefer a lateral decubitus position for arthroscopic labral repair and posterior capsular imbrication. Necessary portals include a high posterolateral portal and two anterior rotator interval portals, one high and one low. The angle of the glenoid makes anchor placement challenging, so placement of the posterior portal as lateral as possible facilitates the correct angle. An accessory portal in the far lateral position for anchor placement is often helpful.

For the repair, the high anterior portal is used for viewing and the lower rotator interval portal, just superior to the subscapularis, is used for shuttling. A large cannula is placed in the posterior portal. In the case of a labral tear, the labrum is mobilized with an arthroscopic elevator analogous to that for anterior labral repair. Anchors are placed in the posterior glenoid rim, sutures retrieved through the anterior portal. Sutures are subsequently shuttled through the soft tissue, a variety of devices are available to perform this. Capsular plication is dependent on the pathology – shoulders with traumatic labral tears can be treated with labral repair only; posterior instability resulting from laxity requires a more substantial imbrication of the posterior capsule. Posterior instability always has an inferior component, so a few plication sutures through the inferior and sometimes anteroinferior capsule are performed.

Postoperatively, patients should be immobilized with the arm in neutral rotation after posterior instability surgery to keep the tension off the posterior repair. Four weeks of immobilization is usually sufficient with elbow, wrist, and hand motion during this early recovery; however, this is adjusted for patients with atraumatic etiology. The authors generally avoid internal rotation for at least 6 weeks.

Mclaughlin presented a technique to prevent the edges of a reverse Hill-Sachs lesion from engaging on the posterior glenoid rim by limiting maximal internal rotation. The subscapularis tendon is detached from the lesser tuberosity and retracted medially and then reattached into the defect with sutures [1]. The Neer modification of the McLaughlin procedure transfers the subscapularis tendon with the lesser tuberosity still attached via an osteotomy [8, 17, 55, 56]. Iliac crest bone graft has been used to fill small lesions of <25 % of the humeral articular surface, as well as allograft osteochondral bone plugs for larger defects of up to 40–50% of the articular surface [8, 17, 56–58]. Recently, a more common variant on this procedure for reverse Hill-Sachs is a reverse remplissage, which can be done arthroscopically [59]. The subscapularis muscle is sutured into the defect with suture anchors without detaching it from the lesser tuberosity. Duey et al. also described a technique to arthroscopically imbricate the middle glenohumeral ligament into the defect [60].

The deficient or retroverted glenoid can be corrected with a bone block procedure or a posterior glenoid neck opening wedge osteotomy [61–64]. A posterior bone block procedure was performed in the lateral position via an open, posterior deltoid-splitting approach, transferring a bicortical graft from posterior iliac crest to an extra-articular position on the posterior glenoid; unlike an anterior bone block, the capsule is intentionally left to interpose between the humeral head and the bone block [65]. Postoperatively, patients are able to regain full external rotation and return to sports at their prior level [64–66]. Millet et al. descried a technique to reconstruct posterior glenoid deficiency with a distal tibial osteoarticular allograft with good outcomes in two patients [67]. A systematic review of bone block procedures confirmed that bone grafting was a reliable procedure since significant improvement in outcomes scores was regularly reported. However, long-term studies showed a clear deterioration in outcomes over time, and the majority of studies reported high frequency of radiographic graft lysis, humeral head osteonecrosis, and advanced osteoarthritis [68].

Lafosse et al. [69] described a posterior bone block procedure analogous to the anterior arthroscopic Latarjet, and this may be appropriate in experienced hands.

Mauro et al. recently examined the effect of glenoid version and width on outcomes following arthroscopic posterior stabilization. In 118 MRAs on athletes with recurrent posterior unidirectional instability, patients with wider and more retroverted glenoid (mean glenoid version 10.8°, mean glenoid width 28.9 mm) had better mean preoperative pain and ASES than those with narrower and more anteverted glenoids. Postoperatively, the wider glenoids continued to have better pain and ASES scores and decreased risk of failure. No correlation was seen between chondral and labral width or version with any pre- or postoperative outcome measured. Thirteen patients who failed capsulolabral repair had 3.0 mm smaller labral width and 3° less labral retroversion, but no bony version differences [70].

In a large study of 200 shoulders (183 patients), Bradley et al. demonstrated excellent outcomes in athletes with unidirectional posterior instability. All patients underwent arthroscopic posterior capsulolabral repair with anchored or anchorless repair. At 36 months, mean ASES score improved 40 points, to 85.1. Stability, pain, and function scores were also improved. Sixty-four percent returned to their prior level of play, but 10 % were unable to return to their sport due to their shoulder injury. Twelve patients were failures by the ASES criteria of score <60, and 14 had a stability score >5; seven patients were failures by both scoring rubrics [71].

Arner et al. [72] showed excellent results of arthroscopic posterior capsulolabral repair in American football players with unidirectional posterior instability. In a group of 56 athletes, 93% returned to play, with 79% returning to the same level of competition at a mean of 44.7 months postoperatively. Significant improvements were seen in pain and ASES scores and 96% were satisfied. No patient was re-dislocated and no revision procedures were required. Baseball players have also shown excellent outcomes. Wanich et al. treated a series of baseball players with posterior labral tears of the lead shoulder. Eleven of 12 treated with surgery returned to previous level of play at 5.9 months postoperatively, and all patients regained full preoperative internal and external range of motion [73]. Wrestlers are also able to return to high levels of participation following arthroscopic posterior capsulolabral complex repair and do so without recurrence over the ensuring season [74].

In a comparison of overhead throwing athletes and non-throwing athletes who underwent capsulolabral repair, McClincy et al. showed no statistical differences in ASES scores, stability, strength, or range of motion at 37 months postoperatively. However, only 60% of throwers were able to return to preoperative level of play. Surgical repair that included discrete suture anchor placement showed a tenfold increase in likelihood of returning to play when compared with anchorless repairs. No variation between repair constructs was seen in return of non-throwing athletes. Additionally, true pitchers had worse return to play rates (50%) when compared with other types of throwers [75].

Pediatric athletes also have excellent results following arthroscopic repair when nonoperative treatment fails. In 25 cases under 18 years of age with unidirectional posterior instability, 92% of shoulders were stable at final follow-up, with two recurrent instability episodes. Equivalent level of play was achieved in 67 %. Outcomes were improved in males, contact athletes, and those with history of traumatic injury as cause of instability [76].

Voluntary dislocators commonly do poorly with surgical interventions [77, 78], and rehabilitation only is encouraged for a more prolonged period than the 6 months recommended for other patient groups. In a series of patients with multidirectional instability and ability to voluntarily dislocate posteriorly, DASH scores improved significantly at all time points with a three-phase rehabilitation program. Therapy focused on correction of abnormal muscle patterns, restoration of correct scapular kinetics, and strengthening [79].