Q: I injured my shoulder playing touch football. It popped out of the socket but went right back in. The orthopedic surgeon I saw thinks it will be okay but there is a risk or it popping out again. If it went back in okay, and I don't stress it, will it stay there?

A: There are many possible reasons why a shoulder dislocation might occur more than once. We call this recurrent shoulder dislocations. One of the main reasons is if there's been damage to the stabilizing features of the shoulder. One of these important anatomic features is called the labrum.

The labrum is a fibrous rim of cartilage around the shoulder socket. It gives the socket more depth and better holding power around the head of the humerus. A tear in the labrum or a pulling away of the tendon with a piece of the labrum can disrupt the natural stability of the shoulder joint.

When this happens, the natural healing process is for the torn structures to pull away from the joint and reattach further down from the original insertion point. The capsule and its associated ligaments get stretched out. The joint widens and then any stress or load on the joint that overpowers this new alignment of soft tissues can pull it right out again.

Some people with one shoulder dislocation do seem to be at increased risk for a second (recurrent) dislocation. For example, there is evidence to show that young age, male sex, and long delay between injury and surgery are the main risk factors for recurrent shoulder dislocations. Other studies have suggested the number of preoperative dislocations as being another possible risk factor for future dislocations. Participation in contact sports may be a risk factor as well.

For those individuals who have surgery to repair the damage, recurrent shoulder dislocation remains a possibility. In fact, studies show up to one-third of patients experience another shoulder dislocation after surgery. In a recent study from the Netherlands, two factors showed up as possible risk factors but without statistical significance. These included using less than three suture anchors and the presence of damage to the labrum.

In the group who had a shoulder redislocation after surgery, two-thirds had been repaired with only two suture anchors. None of the other reported risk factors were found to be influential in this study. The results confirm what surgeons know now that they didn't know 10 years ago: two (or less) suture anchors simply aren’t enough to hold the shoulder. The need for at least three suture anchors is confirmed by the results of this study.

Two other comments of interest were made by the authors. First, as might be expected, patients who do not redislocate have better shoulder function compared with those who do experience a redislocation. And second, redislocation doesn't always occur right away. More than half in this study didn't happen until at least two years had passed since the surgery. Continued study is needed to better understand this second phenomenon.

Reference: Just A. van der Linde, MD, et al. Long-Term Results After Arthroscopic Shoulder Stabilization Using Suture Anchors. An 8- to 10-Year Follow-up. In The American Journal of Sports Medicine. November 2011. Vol. 39. No. 11. Pp. 2396-2403.