A labral tear occurs in less than 10% of cases, but in most cases, the back of the shoulder is simply stretched out. In many cases rehabilitation can restore a tolerable situation and surgery can be avoided, but when frequent episodes of slipping out the back interfere with activities, either arthroscopic plication or traditional open surgery are options.
In both cases, the goal is to tighten the back, and in some cases the front as well--to diminish capsular volume. One risk of surgery is loss of internal rotation and forward flexion, although most of the time functional range returns by 6 months.
The arthroscopic option is attractive because it allows a full assessment inside the joint--in some cases other pathology/laxity can be addressed at the same time, and more easily than if surgery had been performed "open". It does not burn any bridges, so if recurrent instability develops, an open procedure can always be performed. Posterior instability, however, has a higher recurrence rate than anterior, when performed through the scope or open--around 20%. When profound posterior laxity is found--and when it appears to be multidirectional--open surgery may allow a more effective tightening.
In summary, while posterior instability is less likely to require surgical intervention than anterior instability, both arthroscopic and open techniques can provide favorable outcome in 80% of cases.
