Shoulder Instability and Dislocations

The shoulder is the most mobile joint in the body. Consequently, it is also the most commonly dislocated large joint in the body. There are things you should know if you or someone you care about has dislocated his or her shoulder. For example, the first shoulder dislocation leads to a 20% rate of future arthritis, and each subsequent dislocation increases that risk.

Young patients, 20-25 years old or less at the time of the initial dislocation, especially those engaged in contact sports or who use their arms at or above chest level, have a 90-95% risk of recurrent instability (ie. another dislocation or subluxation/partial dislocation). On the other hand, recurrent instability is uncommon in older patients who first dislocate their shoulder at the age of 40 years or older.

Following a single dislocation in young patients <20-25 years old, especially if they are contact athletes, arthroscopic stabilization decreases the rate of recurrent instability. Following arthroscopic stabilization the rate of recurrent instability is 7-10%, compared to 46-58% for those treated without surgery. A government-sponsored review noted a 68-80% reduction in the risk of recurrent instability in those young patients that had surgery compared to those who didn't. Patients who underwent arthroscopic surgery had significantly better outcomes, better function, less joint damage, were more satisfied, had a better chance to return to sports , had an improved quality of life and even had lower overall treatment costs. Allowing multiple subluxations or dislocations to occur causes additional damage to the shoulder's ligaments, increases the risk of arthritis, and erodes the bone from the humeral head (the 'ball' of the shoulder) and/or the glenoid socket that keeps the shoulder located.

Therefore, arthroscopic stabilization surgery should probably be performed following even a single dislocation in young athletes 25 years old or younger, professional athletes, or in those in whom a recurrent dislocation could be disastrous, such as mountain climbers and construction workers that work at heights. Arthroscopic surgery should also be performed if the shoulder dislocates a 2nd time, or if there is pain due to recurrent subluxations that is not resolved by therapeutic strengthening exercises and acceptable activity limitations. Modern arthroscopic techniques lead to 92-97% good-excellent results, with 91% of high-demand contact athletes returning to sport.

In older patients who have had only a single dislocation and who are not engaged in contact sports, physical therapy to strengthen the muscles about the shoulder may be enough to decrease symptoms and prevent further instability. And while immobilization in a sling or other similar device does not decrease redislocation rates, avoiding bringing the arm up and back (as when throwing a ball) and avoiding sports for six weeks can help decrease re-dislocation rates

The problems created by shoulder dislocations are different for people over 40 years of age. While older patients don’t usually suffer re-dislocations, 54% have their rotator cuffs torn by the dislocation, leading to pain and weakness. Patients over 40 years old who have dislocated their shoulder should have an MRI to diagnose any rotator cuff tear. If the rotator cuff is torn, it should be fixed to maximize function, minimize pain and lower the chance of recurrent instability. This can be done very effectively arthroscopically.

Following multiple dislocations or if a shoulder is left dislocated for a number of hours, bone loss of either the humeral head (ball) or glenoid socket may occur. It should be noted that a CT scan is needed to accurately diagnose bone loss, as MRI notoriously underestimates the degree of bone loss or misses it entirely. If less than approximately 1/5 of the glenoid is eroded, the shoulder may still be treated arthroscopically with good success. However, if >1/5-1/4 of the socket has been eroded away, open surgery with a bone graft taken from another part of the shoulder is needed. While this is open surgery, it is still an outpatient procedure and leads to good or excellent results in 83-95%. If the humeral head (ball) is damaged, unless the bone defect is very large, this can still be treated arthroscopically by repairing part of the rotator cuff into the bony defect.

So, if you or someone you care about has dislocated their shoulder, or has an unstable shoulder, get them evaluated by an orthopaedic shoulder specialist before more damage is done and the risk of future problems increases.