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Shoulder Instability by Debra Wood, RN

Definition

Shoulder instability is a condition in which the upper-end of the humerus (the upper arm bone) slides partially or completely out of the shoulder socket.

Normally, the head of the humerus, moves within the confines of the shoulder socket. Instability occurs when the head slips outside its normal position. The humeral head may move in one or more directions. The disorder is classified by how much this bone moves and by the direction it moves:

Subluxation—The humeral head moves part way out of the shoulder socket.
Dislocation—The humeral head moves completely out of the socket.
Anterior—The humeral head moves toward the front. This is the most common form, which typically occurs in young men. Athletes with great shoulder flexibility are more prone to the disorder. Reinjury is more common in teens and young adults, because they have more elasticity in their shoulder capsule and ligaments. This can lead to later chronic instability.
Posterior—The humeral head moves toward the back. This is often caused by a severe muscle spasm, such as during an electric shock or seizure . It less commonly happens as a consequence of direct trauma, which can lead to later chronic instability.
Multidirectional—This usually occurs in athletes born with very loose joints. Certain sports that require great shoulder range of motion, such as swimming, may lead to multidirectional instability. In some less common instances, patients purposely contract or relax muscles to create an instability episode, which is sometimes associated with psychological problems.

Shoulder Instability

Causes

Shoulder instability often results from an initial acute injury producing a dislocation that, even with healing, leads to stretching of the shoulder capsule and ligaments. This type of injury could be due to a fall, a direct hit, or force applied to the outstretched arm. More rarely, shoulder instability develops slowly without any history of previous injury. In some cases, the shoulder may slip out of place at predictable times, such as when lifting a suitcase or even when shaving.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors for shoulder instability include:

Athletic activity, especially:
- Baseball—pitching
- Football—tackling
- Gymnastics
- Weight-lifting
- Any contact sport
- Volleyball
- Swimming, especially backstroke or butterfly
Congenital collagen disorders, such as:
- Marfan syndrome —a connective tissue condition
- Ehlers-Danlos syndrome —a condition in which patients have loose joints
Family members with shoulder instability

Symptoms

Symptoms may come on suddenly or develop over time. Symptoms may include:

Pain in the shoulder area
Shoulder or arm weakness
Shoulder may feel loose
Shoulder may slip out of place
Numb feeling down the arm

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam. Special attention will be given to your shoulders. Your doctor will determine your range of motion and try to move the humeral head within the socket.

Tests may include:

X-rays —a test that uses radiation to take a picture of structures inside the body, especially bones
MRI scan —a test that uses magnetic waves to make pictures of the inside of the body. The capsule and ligaments of the shoulder can be seen with this study.

Treatment

Therapy will depend on the extent of the injury, the cause, and other factors. Treatment may include:

Rest—Avoid activities that produce pain or stress the joint.
Ice—This helps to control pain, especially after exercise.
Medication—Nonsteroidal anti-inflammatory drugs (NSAIDs) may be given to manage pain. These include:
- Aspirin
- Ibuprofen (Motrin, Advil)
Rehabilitation—This can last several months and may include:
- Physical therapy to strengthen the muscles that control the shoulder joint, particularly the internal rotators of the shoulder
- Specific exercises for certain sports or job activities
- Learning how to modify activities to prevent reinjury
Surgery—Many different procedures may be used to correct shoulder instability. The goal is to fix the cause. The doctor may use an arthroscopic or an open technique. After surgery, the arm is kept from moving for 3-6 weeks, depending upon the procedure.

Prevention

Guidelines to help protect the shoulder from injury include:

Do regular exercise to strengthen the supporting muscles.
Use proper athletic training methods.
Do not increase exercise duration or intensity more than 10% per week.
Modify activities to prevent excessive external rotation and overhead motions of the shoulder.

RESOURCES:

American Academy of Family Physicians http://familydoctor.org
American Academy of Orthopaedic Surgeons http://www.aaos.org

CANADIAN RESOURCES:

Canadian Orthopaedic Association http://www.coa-aco.org/
Canadian Orthopaedic Foundation http://www.canorth.org/

References:

Behrman RE, Kliegman R, Jenson HB. Nelson Textbook of Pediatrics . 16th ed. Philadelphia, PA: WB Saunders Co; 2000.
Canale ST. Campbell's Operative Orthopaedics . 9th ed. Philadelphia, PA: Mosby Inc; 1998.
Conservative management of shoulder injuries. Orthopaedic Clinics of North America . April 2000.
Luime JJ, Verhagen AP, Miedema HS, et al. Does this patient have an instability of the shoulder or a labrum lesion? JAMA . 2004;292:1989-1999.
Mahaffey BL. Smith PA. Shoulder instability in young athletes. Am Fam Physician . 1999;59:2773.
Mulley AG and AH Goroll. Primary Care Medicine: Office Evaluation and Management of the Adult Patient . 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2000.
Rockwood CA, Bucholz RW, Heckman JD, et al. Rockwood and Green's Fractures in Adults . 4th ed. Philadelphia, PA: Lippincott-Raven Publishers; 1996.
Ruddy S, Harris ED Jr, Sledge CB. Kelley's Textbook of Rheumatology . 6th ed. Philadelphia, PA: WB Saunders Co; 2001.

Last reviewed July 2010 by Robert E. Leach, MD

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