Shoulder dislocations are a common injury in sports. Whether you take a header off of a mountain bicycle or are trying to make an arm tackle in football, the shoulder can become dislocated.
The shoulder joint is comprised of the humerus (arm bone) and the scapula (shoulder blade). The shoulder joint, or glenohumeral (G-H) joint is very mobile, this accounts for its instability. The shoulder can be thought of as a golf ball (the head of the humerus) sitting on a golf tee (glenoid fossa or socket of the scapula). The shoulder has a structure to assist with stability, it is the glenoid labrum. The labrum is an extension of the ligaments of the G-H joint that forms a rim of cartilage around the glenoid to give the golf tee a deeper socket.
As seen in the photo, the most common dislocation is anterior. The arrow points to the head of the humerus. It has been moved out of the socket forward and toward the middle of the body. Ninety-seven percent of dislocations are anterior while only 3% are posterior.
Dislocation can occur from numerous causes, most often the shoulder is placed in abduction and external rotation. Since this is the most common mechanism of dislocation, the physician test for a recurrent dislocations is to place the patient in this position. The picture shows the shoulder apprehension test. A positive test manifests itself by pain and fear of another dislocation by the patient. Also, the physician may feel the head of the humerus slide forward during the test.
A G-H dislocation should only be reduced (put back) by a trained medical professional. Proper reduction must be done to avoid damage to nerves, arteries, or veins that are located around the shoulder joint. The nerves are especially vulnerable to damage with a dislocation or during reduction. As last the graphic shows, nerve damage can occur following dislocation due to a stretch injury.
When the glenoid dislocates, it is very common for there to be damage to the articular surface. Basically, while either dislocating or during relocation, the head of the humerus strikes the bony rim of the glenoid. This results in a Hill-Sachs lesion. X-rays are necessary after a dislocation to determine if this lesion is present. Treatment of a shoulder dislocation with a Hill-Sachs Lesion is more conservative to prevent further damage to the articular surface of the humerus. This dent can lead to premature arthritis of the shoulder if not treated properly.
Another common complication of a shoulder dislocation is a labrum or cartilage tear. The labrum is an extension of the glenohumeral ligaments which are stretched during a dislocation. If the force is severe enough, the cartilagenous rim may be pulled loose from the glenoid. The resulting labrum tear usually requires surgery to repair. As in the knee the cartilage does not have a very good blood supply, this results in the slow or non-healing of the cartilage.
One type of cartilage tear is the SLAP lesion. This injury was covered in a previous edition of The Athletic Advisor. This injury is usually due to repeated trauma, and not a traumatic dislocation. Keep in mind that athletes who participate in overhead activities (baseball, softball, weightlifting, and swimming) generally have genetically loose shoulders. Due to this repeated “minor slipping” of the G-H joint may lead to a SLAP lesion.
More commonly a traumatic dislocation results in a Bankhart tear of the labrum. Since the humerus slides anteriorly, the tear in the cartilage will be on the anterior of the glenoid. The location of the tear will allow the humerus to dislocate more easily. The MRI shows a tear in the glenoid labrum. The area near the red arrow is the location of the tear. The triangular area of white is the labrum, the small area in the middle is the tear of the labrum. This must be surgically reattached to prevent further dislocations.
Shoulder dislocations, when treated properly, will heal with very little complications. First time dislocations, particularly in the young athlete, need to be treated appropriately to prevent a “loose shoulder.”
Studies have shown that if a first time dislocation, with out labral tears, will heal in 6 to 8 weeks with out residual laxity. The key to optimal recovery is early immobilization of the shoulder for 4 to 6 weeks. This is followed by 6 to 8 weeks of graduated rehabilitation exercises to strengthen the rotator cuff and other shoulder muscles.
If the first time dislocation is allowed to return to participation too early, the shoulder ligaments will not be allowed to heal properly. This can result in a loose shoulder, dislocating with less and less force each time. Each subsequent dislocation can result in joint surface damage. Also, the more times a joint is dislocated, the more difficult a surgical reconstruction can be.
Shoulders that dislocate due to genetically loose ligaments may suffer the same long-term damage as an inappropriately treated first time dislocation. These individuals may or may not benefit from surgical reconstruction. Each person’s results are different in response to the surgery. In some cases the tightened ligaments loosen back to normal length.
©2000 - 2009 David Edell
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Last Update for AthleticAdvisor.com: 10/24/2009 12:09:35 AM