Chronic Shoulder Instability

The shoulder is the joint with the greatest range of motion in our bodies. The shoulder allows for movements such as throwing a baseball or reaching up over our heads to style hair. If an injury is significant enough to cause a dislocation, a separation of the arm bone from the shoulder socket, the shoulder may be susceptible to future dislocations and chronic shoulder instability. Some cases of chronic instability are not caused by a single injury but rather by constant overuse of the shoulder—for example, athletes who do a lot of overhead throwing, like baseball pitchers.

Anatomy

The bones that make up the shoulder are the upper end of the arm bone (humerus), the shoulder blade (scapula), and the collarbone (clavicle). Some would describe this joint as a ball and socket type of joint, but in reality, it is more like a ball sitting on a golf tee, meaning that there is a very small surface area of bone contact. The stability of the shoulder joint relies heavily on the soft tissues around the bones, including muscles, tendons, ligaments, capsule, and labrum, that keep the arm centered with the shoulder blade. The collarbone or clavicle is another structure in the shoulder region that attaches to the shoulder blade at the front of the shoulder; this joint is called the acromioclavicular joint (AC joint).

Shoulder Instability

When the humeral head is not centered in the socket, this causes the joint to be unstable. This may arise from a traumatic injury where the humerus is forced away from the scapula. A full separation of the ball and socket joint is called a dislocation. A dislocation can cause damage to the bones and surrounding soft tissues, including labral tears, bone loss, and impaction fractures. Instability may also be caused by chronic overuse of the shoulder. The joint may also be partially separated but not entirely, called a subluxation. Ligaments, tendons, and muscles can become loose or torn. In many situations, these injuries may heal without surgery. However, repeat or long-term problems with dislocations or subluxation may benefit from surgical repair. Chronic issues with instability may lead to arthritis as well.

Symptoms include pain with shoulder movement, the feeling of the shoulder slipping out of place, repeated dislocations, and shoulder weakness.

Evaluation

Physical examination: Along with obtaining information about the nature of the injury and/or symptoms, a medical practitioner may examine the shoulder to check for range of motion, apply pressure to various areas of the shoulder to see if this causes pain or feelings of instability, check nerve function in the muscles and skin of the arm/hand. Special tests may be performed to evaluate for specific conditions of the shoulder, like the ones mentioned above.

Imaging

Based on the history of the shoulder symptoms and the practitioner’s physical examination, imaging can be beneficial in identifying the key cause of the shoulder complaint. X-rays are very effective in evaluating and monitoring the healing of fractures and dislocations, and they may also aid in assessing the degree of arthritis.

A CT scan may give finer detail regarding fractures and bony abnormalities of the shoulder.

MRI is best for evaluating soft tissue injuries like rotator cuff or labral tears. In some cases, contrast may be injected into the joint to allow for better visualization of structures.

Treatment

Rest and Activity Modification: Taking a break from activities that stress the shoulder can help decrease inflammation and symptoms. Goals will focus on avoiding activities that aggravate symptoms.

Anti-Inflammatory Medications: These oral medications are usually found over the counter and are designed to decrease inflammation and control pain.

Exercises/Physical Therapy: This may dramatically reduce symptoms and help the patient regain strength as the patient heals their injury. Goals will focus on strengthening and shoulder control. It is important to note that consistency with physical therapy, usually for at least 4-6 weeks, or more, is the most beneficial.

Surgery: Surgery may be needed for repeated dislocations or if symptoms do not improve with the treatment mentioned above. Surgery will repair torn ligaments and labrum and tighten up the shoulder capsule. In most cases, this may be done arthroscopically using small incisions and cameras to look inside the shoulder joint. If a repair cannot be done arthroscopically, it may be done in an open fashion, meaning with a larger, direct incision.