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 Definition A shoulder dislocation is when the top part of the arm bone (humeral head) slips out of its socket (glenoid).

Diagram and X-ray of a Normal Shoulder
Details Forward (anterior) dislocations are most common. When this occurs the anterior inferior labrum (a piece of cartilage that stabilizes the shoulder) frequently is torn. This is known as a Bankart lesion. A dent in the humerus bone known as a Hill-Sachs lesion may accompany the Bankart lesion in severe dislocations.

Shoulder dislocations can also occur backward (posterior) and downward (inferior). Repeated dislocations and multidirectional shoulder instability are also possible.
Causes Falling is the most common cause of a new shoulder dislocation. A dislocation can also occur when the arm is forcibly moved into an awkward position during a violent action such as tackling in football. If a dislocation or partial dislocation (medically known as a subluxation) occurs with only minor force, recurrent or multidirectional instability must be considered.
Diagnosis A shoulder dislocation is diagnosed when a patient presents with a history of a fall with subsequent pain around the shoulder. Typically, a visible deformity is seen in front of the shoulder. The patient will also not be willing to move the arm due to pain. X-rays are used to confirm the dislocation and rule out any fracture around the shoulder.

X-rays of Normal and Dislocated Shoulders

Occasionally, an MRI is needed to further access any damage that may have occured when the shoulder dislocated. The MRI can determine if a tear of the anterior inferior labrum has occured. The tear can be associated with a small bony fragment of the shoulder socket (Glenoid).

Think of the shoulder joint as a golf ball and tee. When it dislocates the front part of the tee breaks and then the ball falls off the tee.

MRI of anterior inferior labral tear/Bankart Lesion
Treatment Nonoperative: For first time dislocations, a sling and activity restriction is used for several weeks. A supervised physical therapy program is also crucial to prevent repeated dislocations. The therapy is directed at strengthening the muscles around the shoulder and upper back that help stabilize the shoulder in its socket.

Operative: For young patients, there is a high risk of recurrent dislocation. For these patients with repeated dislocations, surgery may be indicated. The surgery involves repairing and tightening the structures within the shoulder that were damaged during the dislocation. The most common procedure is an open reconstruction.

Arthroscopic (minimally invasive) reconstruction techniques, however, are evolving regarding the treatment of shoulder dislocations. Application of these techniques such as thermal stabilization and arthroscopic repair are becoming more popular and effective.

Arthroscopic Bankart Repair Pictures and Animation

Arthroscopic Thermal Shrinkage of a Lax Shoulder Joint

Maintaining excellent strength and stability of the shoulder and upper back muscles may help prevent some dislocations.