Shoulder and Elbow

Chronic Shoulder Instability

Anatomy

The shoulder is a complex, ball-and-socket joint that rotates through a greater range of motion than any other joint in the body. The shoulder is made up of: the upper arm bone (humerus), shoulder blade (scapula), and collarbone (clavicle). The ball, or head of the upper arm, fits into a shallow socket (glenoid) in the shoulder blade. The ends of these bones, where they touch, are covered with articular cartilage, a smooth substance that protects the bones and enables them to move easily. The glenoid is ringed by the labrum, a strong, fibrous cartilage that forms a gasket around the socket, adding stability and cushioning the joint.

The shoulder joint is surrounded by bands of tissue, called ligaments, to form a capsule that holds the joint together. The undersurface of the shoulder capsule is lined by the synovium, a thin membrane that produces synovial fluid to lubricate the cartilage and eliminate friction. Four tendons surround the shoulder capsule and help keep the arm bone centered in the shoulder socket. This thick tendon material, called the rotator cuff, covers the head of the humerus and attaches it to your shoulder blade. Between the rotator cuff and the bone on top of your shoulder (acromion), a lubricating sac (bursa) helps the rotator cuff tendons glide smoothly during movement.

Normally, these components work together in harmony, but when disrupted by disease or injury the result can be pain, muscle weakness and reduced function.

Description

Although the enables you to lift your arm, turn or rotate it in many directions, and reach above your head, this greater range of motion also results in less stability. Shoulder instability occurs when the head of the upper arm bone is forced out of the shoulder socket due to sudden injury or overuse. In a partial shoulder dislocation (called a subluxation), the ball of the upper arm only comes partially out of the socket, but in a complete dislocation the ball comes all the way out of the socket.

Once a shoulder has dislocated, or the shoulder's ligaments, tendons and muscles become loose or torn, that shoulder is vulnerable to repeated dislocations. Chronic shoulder instability is the persistent inability of these tissues to keep the arm centered in the shoulder socket, so the shoulder is loose and slips out of place repeatedly.

Causes

There are three common ways that a shoulder can become unstable.

• Shoulder dislocation—Severe injury, or trauma, is often the cause of an initial shoulder dislocation. When the head of the humerus dislocates, the socket bone (glenoid) and the ligaments in the front of the shoulder are frequently injured. The torn ligament in the front of the shoulder is commonly called a Bankart lesion. A severe first dislocation can lead to continued dislocations, giving out, or a feeling of instability.
• Repetitive strain—Some patients with shoulder instability have never had a dislocation. Most of these patients have looser ligaments in their shoulders, which may be their normal anatomy or the result of repetitive overhead motion. Repetitive, overhead motion or work, as occurs during certain jobs, or sports, such as swimming, tennis and volleyball, can stretch out the shoulder ligaments. These looser ligaments make it more difficult to maintain shoulder stability, especially when challenged by repetitive or stressful activities. This can result in a painful, unstable shoulder.
• Multidirectional Instability—In a small minority of patients, the shoulder can become unstable without a history of injury or repetitive strain. In such patients, the shoulder may feel loose or dislocate in multiple directions (out the front, back or bottom of the shoulder). This is called multidirectional instability. These patients have naturally loose ligaments throughout the body and may be double-jointed.

Symptoms

Common symptoms of chronic shoulder instability include: pain caused by shoulder injury, repeated shoulder dislocations, repeated instances of the shoulder giving out, or a persistent sensation of the shoulder feeling loose, slipping in and out of the joint, or just "hanging there."

Diagnosis

During an examination of your shoulder, your doctor may check for general looseness in your ligaments and perform specific tests to assess instability in your shoulder. Imaging tests may be needed to help your doctor confirm your diagnosis and identify any additional problems.

• X-rays—Injuries to the bones that make up your shoulder joint will be revealed in an X-ray image.
• Magnetic resonance imaging (MRI)—By creating better images of soft tissues, an MRI may help your doctor identify injuries to the ligaments and tendons surrounding your shoulder joint.
• MR arthrogram—To better visualize the labrum cartilage, a dye can be injected into the shoulder prior to doing an MRI. If shoulder instability is suspected, then an MR arthrogram should be performed instead of a plain MRI.

Nonsurgical Treatment

Chronic shoulder instability is often first treated with nonsurgical options. Your doctor will develop a treatment plan to relieve your symptoms. It may take several months of nonsurgical treatment before you can tell how well it is working. Nonsurgical treatment typically includes:

• Activity modification—Certain lifestyle changes will be required, such as avoiding all activities that aggravate your symptoms.
• Nonsteroidal anti-inflammatory medication—Drugs like aspirin and ibuprofen will help to reduce your pain and swelling.
• Physical therapy—Your therapist will design a home exercise program that will help you strengthen your shoulder muscles and improve shoulder control for increased stability.

Surgery

If nonsurgical options do not relieve the pain and instability, surgical repair may be necessary to enable the torn or stretched ligaments to hold the shoulder joint in place. For some patients, shoulder arthroscopy (minimally invasive surgery) may be appropriate, while others may require traditional open surgery. Your orthopaedic surgeon will discuss the options with you and recommend the procedure that meets your individual health needs.

Rehabilitation

It is important that you follow your doctor's treatment plan carefully. After surgery, your shoulder may be immobilized with a sling for several weeks, depending on your condition. Once your orthopaedic surgeon has removed the sling, you will be given specific program of physical therapy to help you improve the range of motion in your shoulder and prevent scarring. As the ligament heals, exercises to strengthen your shoulder will be gradually added. Rehabilitation plays a vital role in getting you back to your daily activities. The process may seem slow, but your commitment to physical therapy is key to experiencing a successful outcome.