SHOULDER DISLOCATIONS AND INSTABILITY
Instability of the shoulder in patients under 40 results in a situation where the shoulder is loose, and possibly dislocates. Shoulder instability presents as a spectrum of issues. Instability can occur because you stretched your ligaments slowly over time (overhead sports), or instability (dislocation) can occur after a single traumatic episode which has resulted in a ligament tear. Shoulder instability can also be described in terms of its chronicity; acute vs chronic, or direction of the instability; anterior instability, posterior instability and mult-directional instability.
By far the most common form of shoulder instability is the traumatic, anterior form. This typically involves a collision on the ball field or a fall on an outstretched arm. The shoulder dislocates, and on many occassions, a trip to your local ER is needed to reduce the shoulder or put it back into place.
What happended to allow your shoulder to dislocate?
In most traumatic dislocations, the labrum or the ligaments on the front of the shoulder tear and allow the ball of the shoulder joint to jump over the edge of the socket and remain in that position until reduced.
In cases where the ligament has stretched over time, the ligaments are simply not able to prevent the shoulder from dislocating. They are not torn, they are simply not tight enough.
In patients over the age of 50, a common cause of instability is a massive rotator cuff tear. This typically follows trauma, but instead of tearing the ligaments in the shoulder, all the supporting muscles tear and the shoulder slides out of place.
What are the major issues to consider?
In traumatic dislocations there is a risk of nerve or vessel inury. These are relatively rare, but it can cause temporary numbness or tingling in the arm. This occurs because the top of the humerus will hit the nerves in front of the shoulder when it dislocates.
By far the most significant issue in shoulder instability is recurrence... or re-dislocation. The younger you are when you dislocate, the higher the risk of recurrence. Some studies have shown the recurrence rate can be as high as 50-75% in patients under 21 years of age.
How are shoulder dislocations treated?
There is recent literature to support the use of a sling for a few weeks following an acute anterior dislocation. The kicker is, the arm must be externally or outwardly rotated with a special pillow or brace. This theoretically puts the torn ligaments in a better position for healing.
Patients with chronic or multidirectional instability will generally not benefit from the use of a sling.
When is surgery necessary or indicated?
In patients with traumatic instability, surgery is indicated in cases where recurrence is documented and a labral tear, or a ligament tear is present. The number of recurrent dislocations can influence the success rate of the surgery. Everytime your shoulder redislocates, you are stretching the ligaments further.
In patients with atraumatic or multi-directional instability, surgery is only indicated after documented failure of a proper physical therapy program. Many patients in this group will not require surgery.
In older patients whose instability is due to a massive rotator cuff tear, urgent surgery is indicated to maximize chances for a successful the repair since the rotator cuff will retract and undergo degenerative changes with time.
What are the risks of surgery?
The risks of surgery, in general, include the risk of infection, recurrent instability (no surgery is 100% successful), nerve injuries, stiffness, and loss of motion.