What is Shoulder Instability?

Shoulder instability is a condition in which the ball of the shoulder joint (humeral head) either partially or completely comes out of the shoulder socket (glenoid). A shoulder dislocation usually occurs as a result of a high energy fall while playing sports.  Most commonly, the humeral head dislocates anteriorly off the front of the shoulder socket. Typically, people report falling on an outstretched hand, and in the course of bracing one’s fall, the arm forced out away from the body resulting in a dislocation.  In this way, there is sudden abduction and external rotation of the shoulder joint (glenohumeral joint).  When the shoulder dislocates, there is usually a pop, severe pain, and one knows immediately that there shoulder is out of place. With an anterior dislocation, there is a fullness in the front of the shoulder. This is actually the humeral head sitting out in front of the socket. Most people with a first time dislocation are unable to get the ball back in the socket themselves, and they have to go to the ER to have it put back in place. Dr. Cunningham is a shoulder surgeon who specializes in the treatment of shoulder instability for patients in Vail, Summit County, Aspen and Denver, CO.

What Structures are Injured After a Shoulder Dislocation?

When a shoulder dislocates, the labrum typically tears away from the glenoid (socket). The labrum is a “gasket” type of cartilage which is attached around the entire edge of the glenoid. The shoulder joint allows for the largest range of motion of any joint in the body. It does so because the glenoid is a shallow socket and shoulder stability is provided primarily by the labrum and attached ligaments. By comparison, the hip joint has a deep bony socket and stability is provided primarily by the bone.

With an anterior shoulder dislocation, the labrum tears off the front of the socket. The back of the humeral head also gets impacted on the front side of the socket, causing an impaction fracture called a Hill Sachs defect in the humeral head. In some cases, the edge of the bone socket may even chip or fracture (bony Bankart fracture). In someone who has repeated dislocations, over time the humeral head slowly wears away the cartilage and bone from the front edge of the socket, causing the shoulder to be even more unstable as more bone is lost from the edge of the socket. The shoulder joint is like a golf ball on a golf tee.  The ball is held in place due to the concavity of the golf tee and surrounding ligaments, but if you crack the edge of the golf tee, the shoulder becomes even more unstable as bony congruency is critical to stability.

Unfortunately, a labral tear or a bony Bankart fracture will not heal in the correct position. Therefore, if you have sustained one dislocation, you are at higher risk of having yet another dislocation in the future, especially if you are young, male and play contact sports. With each additional dislocation, more damage can occur to the labrum, ligaments and bone. There is also a correlation with the number of shoulder dislocations and the development of future shoulder arthritis. It can get to the point where people even start to dislocate their shoulder simply putting on a shirt or while sleeping. These patients often come to surgery to stabilize their shoulder.

How is Shoulder Instability Diagnosed?

In the office, a good history is obtained to understand what happened to cause the shoulder to dislocate or subluxate (partially dislocate). A physical exam is also performed, checking the shoulder’s range of motion and strength. There may be numbness around the shoulder from a nerve being stretched when the shoulder popped out.

Xrays will be obtained to determine if the humeral head is centered in the socket after the shoulder has been put back in place (reduced). Xrays show if there is a chip fracture off the front of the socket, and help assess the approximate size of the Hill Sachs defect, or impression fracture in the back of the humeral head. An MRI will be ordered if surgery is being considered to delineate where how large a labral tear there is and if there is other associated damage. In cases of suspected glenoid socket bone loss, a CT scan may be ordered, as a CT shows the bone better than an MRI.

How is Shoulder Instability Treated?

After a shoulder dislocation is reduced or the shoulder joint is put back in place, patients are placed in a sling for comfort. Patients can come out of the sling and start gentle range of motion exercises. Physical therapy is prescribed to help slowly restore shoulder range of motion and strength. Most patients achieve full range of motion and strength following a shoulder dislocation in 4 weeks.

Patients at highest risk of having a future shoulder dislocation are young (less than 20 years of age), male, and participate in contact sports (ie. football, rugby). Older patients (over 50 years of age) are at fairly low risk of having a future shoulder dislocation. However, older patients who have suffered a shoulder dislocation often have an associated tear of their rotator cuff, which if not diagnosed can cause ongoing pain and weakness.

Who is a Candidate for Shoulder Instability Surgery?

The treatment of young patients who have suffered a first time shoulder dislocation is controversial. Some Orthopedic shoulder doctors recommend a trial of nonsurgical management consisting of rest, a sling, and physical therapy. Others recommend immediate surgery to repair the damaged labrum arguing that there is a very high likelihood that a young person will have more dislocations and do further damage to their labrum and bone, and that this should be avoided by surgically fixing the injury.

Older patients are not at high risk of recurrent dislocations after a first time dislocation, but they often tear their rotator cuff. For this reason, it is important that an MRI be obtained to check for a rotator cuff tear. If there is a rotator cuff tear, then surgery is recommended to repair it as the tear will worsen with time.

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What is Done in Surgery to Treat Shoulder Instability?

Surgery to repair a shoulder that continues to dislocate is usually done arthroscopically through 3 small incisions less than  ½” each. A camera is inserted into the shoulder and the torn labrum is pulled back up to the edge of the socket where it belongs and repaired there using small but strong surgical implants and suture (stitching) material. Any stretched out shoulder ligaments are tightened in surgery at the same time. Occasionally, one of the rotator cuff tendons (infraspinatus) is sewn into the Hill Sachs impaction fracture in the back of the humeral head in addition to help further stabilize the shoulder. This is called a Remplissage procedure. Associated fractured pieces off of the socket can also be fixed arthroscopically.

What is the Recovery After Shoulder Instability Surgery?

Following surgery, patients go home the same day. They are placed in a sling for 4 weeks. Physical therapy is started soon after surgery. Gentle range of motion exercises are begun after surgery but range of motion is limited such that patients do not stretch out the tissues that were tightened and repaired in surgery. Gentle strengthening is also started. Most patients are pain-free and have full strength and full motion and are back to most sports in approximately 4 months. Dr. Cunningham is a shoulder surgeon who specializes in the treatment of shoulder instability for patients in Vail, Summit County, Aspen and Denver, CO.

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