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Shoulder Dislocations & Instability

By Greer E. Noonburg, M.D.

The shoulder is the most mobile joint in the body. It consists of a ball (humeral head) and shallow socket (glenoid). This design enables the shoulder to perform a wide range of activities, however, stability is sacrificed in order to gain additional mobility. Problems with shoulder stability may result from a single injury caused by a fall or develop over time, as in athletes who perform repetitive overhead activities.

The shoulder is subjected to a great variety of stresses and sometimes the forces applied to the joint overcome its ability to keep the humeral head in contact with the glenoid. A dislocation of the shoulder results when the humeral head is completely displaced out of the glenoid. Subluxation occurs when the humeral head is partially dislocated from the glenoid. Repeated shoulder dislocations or subluxations are referred to as instability, resulting from an injury to one or more of the shoulder structures that help maintain joint stability

The labrum is a fibrocartillagenous rim surrounding the glenoid that enlarges its surface area, increasing the stability of the shoulder joint. Most shoulder dislocations (95%) are anterior, in which the head is displaced in front of the glenoid. Labrum tears usually occur this way and are referred to as a Bankart lesion (named after a British orthopedic surgeon who described the injury).

The shoulder capsule and glenohumeral ligaments (which attach to the labrum), help provide shoulder stability at the extremes of motion. Tearing or stretching these structures often lead to chronic instability. Baseball pitchers, gymnasts, and competitive swimmers often sustain these types of injuries due to the repetitive overhead motions they often perform.

An injury to any of the previously mentioned structures can initiate a cascade of events that turn a simple dislocation into an unstable shoulder that interferes with normal daily activities. Other parts of the shoulder that augment stability, such as the rotator cuff, deltoid muscle, and biceps tendon, may also be adversely affected.

Shoulder dislocations may result in anyone who has fallen on an outstretched arm. Athletes participating in contact sports, such as football, soccer, and rugby, are particularly prone to this type of injury. Another prominent group are the “weekend warriors” who fall during recreational sports like skiing and softball. Posterior dislocations (less than 5%) are often associated with electrocutions and seizures. Some people are “loose jointed” and can voluntarily dislocate their shoulders, which may be entertaining at the time but runs the risk of serious long-term damage to the shoulder joint.

When a shoulder dislocation occurs, it should be placed back into its normal position as soon as possible. Traction is placed on the arm as the humeral head is relocated into the glenoid, in a process called closed reduction. There are a variety of methods to closed reduction, which may be performed by on the field by knowledgeable athletic trainers and emergency medical technicians (EMTs), as well as other medical professionals in a clinic or hospital setting.
Once the closed reduction has been successfully performed, the severe shoulder pain caused by the dislocation will be significantly diminished. X-rays are obtained to confirm correct placement of the humeral head into the glenoid. The arm is placed in a sling or shoulder immobilizer for several weeks. Physical therapy is subsequently initiated to help strengthen the shoulder muscles and restore shoulder motion. Post-injury rehabilitation is very important and may prevent subsequent dislocations.

Despite appropriate immobilization and physical therapy, some patients will develop recurrent dislocations or subluxations. Additional tests may be ordered, such as a magnetic resonance image (MRI). The MRI provides detailed information about the bony anatomy and soft tissue stabilizers of the shoulder, including the labrum, glenohumeral ligaments, capsule, as well as other muscles that surround the shoulder joint.

If shoulder instability continues, an orthopedic surgeon will be needed to correct the problem. There have been many techniques reported in the medical literature to correct shoulder instability. One of the earliest was described by Hippocrates, recommended placing a “red hot poker” into the axilla (armpit) to cauterize the inferior capsule. Fortunately, modern surgical techniques have improved considerably since then.

Based on the physical exam and MRI findings, the orthopedic surgeon may elect to perform surgery to correct the instability. Both open repair and arthroscopic techniques have proven successful results. Repair of a labrum tear (Bankart lesion) may be performed either way, usually with special bone anchors that reattach the labrum to the glenoid.

If the shoulder capsule and glenohumeral ligaments are stretched or torn, they will also need to be repaired. The open techniques requires a 3 to 4 inch incision in the anterior part of the shoulder, dividing and reattaching the capsule in a tighter configuration.

Arthroscopic shoulder surgery utilizes small incisions (1/4 to 1/2 inch) in which the surgeon places a small scope into the shoulder joint to examine its many structures. Through additional small incisions, the surgeon will place instruments to repair the labrum (if needed) and tighten the shoulder capsule. There is generally less post-operative discomfort after arthroscopic surgery due to the minimization of soft tissue dissection.

Regardless of the type of shoulder surgery performed, the patient will remain in a sling for several weeks. Physical therapy is usually begun within a week or two of surgery. As the shoulder joint heals, strength and flexibility rehabilitation will be advanced. Patients can generally return to non-contact sports within 3 months and contact sports in 4 months.

Shoulder dislocations primarily occur in young adults, although any age group may be affected. Following closed reduction and physical therapy to improve the patient’s function, continued dislocations or subluxations may still occur. Surgical management utilizing open or arthroscopic techniques will improve the patient’s functional status. Further questions may be answered by your orthopedic surgeon, who can provide specific information regarding your condition.

For more information about shoulder instability or other orthopedic concerns – contact Dr. Noonburg at Chatham Orthopaedics, 4425 Paulsen Street, Savannah, GA 31405,
(912) 355-6615