Chronic shoulder instability occurs when the head of humerus (upper arm bone) either partially or completely comes out of the shoulder socket repeatedly. There are many different types of shoulder instability, but the most common cause is due to a shoulder dislocation. Once a shoulder has dislocated one time, it is at significantly increased risk for a repeat dislocation.
Causes of shoulder dislocation most commonly include: trauma, seizures and congenital conditions leading to laxity of soft tissues and hypermobility of other joints.
Shoulder Instability Terms
Caused by an event that leads to the head of the humerus (ball) coming out of the front of the socket. This is the most common type of shoulder dislocation.
Caused by an event that leads to the head of the humerus (ball) coming out of the back of the socket. These are rare, and most commonly caused by trauma, seizures or electric shock.
When the head of the humerus (ball) partially comes out of the socket, but does not completely dislocate
This is a deformity in the head of the humerus caused by a dislocation. It often times creates an indentation in the head of the humerus that can lead to further instability events.
Sometimes extensive tearing to the labrum (fibrous cartilage ring surrounding the shoulder joint) that happens after a shoulder dislocation can be a source of instability.
This is a deformity that affects the front and bottom part of the labrum as a result of a shoulder dislocation. The labrum is torn off the socket bone in this part of the shoulder. At times, a small portion of the bone can come off with the labrum.
Acute anterior shoulder dislocation:
The symptoms of an acute shoulder dislocation include visible shoulder deformity with a bony prominence at the front of the shoulder, pain, inability to move the arm, possible swelling, bruising, and/or numbness.
Repeated subluxations and/or dislocations of the shoulder joint. The sensation that the shoulder is going to pop out of place with certain arm movements
Your healthcare provider will evaluate your range of motion, measure strength, and perform special tests to help diagnose the source of your shoulder symptoms. They will use the results of their exam to determine if you need further testing (e.g. x-ray, MRI, CT scan).
Acute Shoulder Dislocation:
If your shoulder has dislocated and did not immediately “pop back into place”, this is an emergency that requires immediate medical attention and you should call 911. Your medical provider will attempt to reduce the shoulder joint to put the arm bone back into the socket. It is important that your shoulder is reduced as soon as possible. Once the shoulder is reduced, you will need to keep your arm in a sling for a few weeks. You may need to go to physical therapy for a few weeks followed by an evaluation with a shoulder specialist to see if you are still having any signs of instability.
Your risk of needing surgery after a first time anterior shoulder dislocation is higher if you are under the age of 30, participate in contact sports or other vigorous physical activity.
Chronic Shoulder Instability:
There are different ways to manage instability based on the severity of your symptoms, the type of instability that you have, and the length of time you have been having symptoms. Treatment often first consists of a period of shoulder immobilization followed by physical therapy to strengthen the muscles surrounding the shoulder joint. If this is not effective, you may need a shoulder stabilization surgery.
Types of Shoulder Stabilization Surgeries
This is an outpatient procedure focused on tightening your shoulder joint to prevent ongoing instability. It is based on your specific symptoms and findings on MRI. It may involve tightening the joint capsule, repairing the labrum, repairing a Bankhart deformity, and or repairing a Hill-Sachs deformity.
Anterior Bone Block with Allograft:
This is an arthroscopic procedure where a piece of donor graft is used to fill the deficit in the socket (glenoid). This procedure is most commonly done when there is significant bone loss in the front of your socket. Bone deficiency in the socket can result from a trauma, recurrent dislocations, or a congenital deformity. Filling the deficit with the bone graft acts to prevent further dislocations.
This is an open surgical procedure involving the transfer of part of your bone (the coracoid) as well as a muscle transfer to fill a bony deficit at the socket (glenoid). This procedure is most commonly done when there is significant bone loss in the front of your socket. Bone deficiency in the socket can result from a trauma, recurrent dislocations, or a congenital deformity. Filling the deficit with the coracoid bone acts to prevent further dislocations.
Open surgery to treat a posterior dislocation with a large reverse Hill-Sachs deformity. Involves the transfer of either a muscle or bone to fill the bony defect and prevent future posterior dislocations.
Ehlers-Danlos Syndrome (EDS):
This is a group of inherited disorders that affects connective tissue and among many other things can cause overly flexible joints. People with EDS are at higher risk of chronic shoulder instability. While each patient with EDS is different, shoulder instability in this population is generally best managed without surgical intervention, if possible. Surgery is an option as a last resort and is performed primarily for pain relief when non-surgical options have failed. Risk of recurrent instability after shoulder surgery in patients who have EDS is very high due to differences in connective tissue.