Jan. 5, 2005

ACC Sports Sciences Main Page

Scott C. Montgomery, M.D.
David R. Diduch, M.D.
University of Virginia Sports Medicine

The shoulder is an inherently unstable joint. If a hip joint is a ball in a cup, then the shoulder joint is a ball on a golf tee; it can easily fall off. This allows both the large functional range of motion needed to perform a free-style stroke and the potential to slip off the tee. Instability can result in a dislocation if the shoulder is knocked all of the way out of the joint or a subluxation if it moves part of the way out of the joint. There are two main types of shoulder instability -- traumatic and atraumatic. Traumatic instability involves an initial event in which the shoulder pops out of place (dislocation), usually requiring someone else to put it back in place. While traumatic instability is more common in contact athletes such as football and lacrosse, atraumatic instability is common in sports that emphasize repetitive activities, such as swimming, and more often results in subluxation. As the name suggests, this type of instability does not result from a single injury to the shoulder but rather a stressful activity repeated many times resulting, over time, in micro-trauma to the shoulder which causes the symptoms and ultimate reduction in peak athletic performance.

Who gets shoulder instability?
The shoulder is a common source of injury in both elite level and recreational swimmers. A recent study showed that there was greater shoulder laxity in elite swimmers than in recreational swimmers due to a combination of acquired and inherent factors.

Diagnosis
As always, history and physical examination are the most important pieces for information gathering with any injured athlete. Competitive swimmers who train for longer periods of time, swimmers with poor stroke mechanics, or those who rapidly increase their training schedule are most at risk for instability. They complain of shoulder pain, which is worse after strenuous exercise.

Physical exam findings help diagnose instability. Many swimmers have generalized hyperlaxity (double jointed). This in itself does not predict shoulder pain, but implies atraumatic instability. In fact, it might be a big reason why a swimmer can perform at an elite level in the first place. The most common criteria physicians use for judging lax joints in the body looks at bending the thumb to the forearm, elbow hyperextension, and the shoulder sulcus. Laxity only becomes a problem when it causes pain and does not allow the athlete to continue to function at a high level.

Specific exam findings can aid the diagnosis. An apprehension test is performed with the patient on her back, with her arm abducted and externally rotated. The patient feels pain and an uncomfortable feeling that their shoulder might slide out of its socket. This apprehensive feeling is often relieved with pressure on the front of the humerus with the arm in the same position. This relocates the shoulder in its socket and relieves the uncomfortable feeling and quite often the pain.

Imaging
Although instability is typically a diagnosis made with history and physical examination, physicians will often order an x-ray or a magnetic resonance image (MRI) to look closer at the anatomy and rule out any additional injury. The MRI examination will often include contrast or "dye" placed into the shoulder joint with an injection to help see the shoulder structures better. On MRI, a swimmer with atraumatic instability will often have irritated tissue in the capsule of her shoulder or some rotator cuff tendonitis. Quite often, the MRI is read as normal. In traumatic instability, when the shoulder goes out of socket, the soft tissue portion of the socket called the "labrum" is usually detached. This detachment is called a Bankhart lesion and can be seen on MRI.

Non-operative therapy (rehab)
The main treatment for athletes with atraumatic shoulder instability is physical therapy. The capsule of the shoulder is like a balloon holding the ball on the golf tee. If the balloon is loose, the next layer out is the rotator cuff. Athletes and their trainers should focus on general rotator cuff muscle strengthening, as this can often overcome a loose capsule and can keep the shoulder stabilized. They will also include balanced anterior and posterior capsule stretching and periscapular strengthening and conditioning. If there is a more predominant direction to the instability (anterior-inferior or posterior), then specific rehabilitation programs should be designed to strengthen the muscles protecting the shoulder in the offending position. In traumatic instability, the edge of the balloon is pulled off of the golf tee and surgery is often required as cuff strengthening alone will not help the torn labrum heal correctly.

Surgery
If a prolonged course of rehabilitation (often 6-9 months) fails to relieve the symptomatic atraumatic instability, then there are surgical options.

"The whole point of surgery is to tighten up and repair the structures around the shoulder."

Traditionally, all surgery for shoulder instability was done by making an incision (called open surgery) and repairing or tightening up the offending structures. The "gold standard" procedure for an athlete with symptomatic anterior or anterior-inferior instability is the inferior capsular shift.

The "gold standard" procedure for an athlete with symptomatic posterior instability is the posterior capsular shift. Recently, advances in arthroscopic surgery have allowed physicians to treat symptomatic shoulder instability entirely through the scope. Both anterior and posterior capsular laxities, which are often causes of the atraumatic instability, can be addressed with an arthroscopic capsular shift using plication sutures. In traumatic instability, the Bankhart lesion can be seen and repaired directly to the edge of the socket. Various suture anchor systems and suture passers allow accurate reattachment of the capsule. Current arthroscopic methods achieve results that compare favorably with open methods while preserving motion and resulting in much less operative pain. Whether open or through a scope, the whole point of surgery is to tighten up and repair the structures around the shoulder to help better keep it balanced on the golf tee.

Return to the pool
Swimmers are ready to return to the pool when they have good range of motion and strength and have completed their rehab program with their therapist. Healing time for the labral or Bankhart reattachment is 3 - 5 months. Although shoulder instability is a common and sometimes painful condition for swimmers, most can return to competition again.

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