Sidelined by a Dislocated Shoulder
The shoulder is the most mobile and least stable joint in the body. Its
ability to move in many directions makes it prone to dislocation, and in younger
people, sports injuries are a common reason. Throwing or reaching for a ball
puts the shoulder at risk because there is little that stabilizes the shoulder
Shoulder dislocation facts
- The shoulder joints are the most commonly dislocated joints in the body.
- Approximately 25% of shoulder dislocations have associated fractures.
- Closed reduction, without the need for surgery, is the most common initial treatment. Medications may be required for sedation to help relax the muscles surrounding the shoulder and facilitate the reduction.
- Immobilization with a sling is important to decrease the risk of a repeat dislocation. First dislocations are immobilized in an external rotation position. Recurrent dislocations may be immobilized in a regular sling.
- Early follow-up is important to decide when to begin allowing shoulder motion.
- Total time of immobilization varies, and balance needs to exist between shoulder stability and loss of motion and function from prolonged immobilization.
- Recurrent shoulder dislocations may be an indication for surgery to repair and tighten torn tissues.
- Uncomplicated rehabilitation and healing will allow return to normal function in 12-16 weeks.
What is dislocation of the shoulder? What causes a shoulder dislocation?
The shoulder joint is the most mobile joint in the body and allows the arm to move in many directions. This ability to move makes the joint inherently unstable and also makes the shoulder the most often dislocated joint in the body.
In the shoulder joint, the head of the humerus (upper arm bone) sits in the glenoid fossa, an extension of the scapula, or shoulder blade. Because the glenoid fossa (fossa = shallow depression) is so shallow, other structures within and surrounding the shoulder joint are needed to maintain its stability. Within the joint, the labrum (a fibrous ring of cartilage) extends from the glenoid fossa and provides a deeper receptacle for the humeral head. The capsule tissue that surrounds the joint also helps maintain stability. The rotator cuff muscles and the tendons that move the shoulder provide a significant amount of protection and stability for the shoulder joint.
Dislocations of the shoulder occur when the head of the humerus is forcibly removed from its socket in the glenoid fossa. It's possible to dislocate the shoulder in many different directions, and a dislocated shoulder is described by the location where the humeral head ends up after it has been dislocated. Ninety-five percent or more of shoulder dislocations are anterior dislocations, meaning that the humeral head has been moved to a position in front of the joint. Posterior dislocations are those in which the humeral head has moved backward toward the shoulder blade. Other rare types of dislocations include luxatio erecta, an inferior dislocation below the joint, and intrathoracic, in which the humeral head gets stuck between the ribs.
Picture of the shoulder joint
Dislocations in younger people tend to arise from trauma and are often associated with sports (football, basketball, and volleyball) or falls. Older patients are prone to dislocations because of gradual weakening of the ligaments and cartilage that supports the shoulder. Even in these cases, however, there still needs to be some force applied to the shoulder joint to make it dislocate.
Anterior dislocations often occur when the shoulder is in a vulnerable position. A common example is when the arm is held over the head with the elbow bent, and a force is applied that pushes the elbow backward and levers the humeral head out of the glenoid fossa. This scenario can occur with throwing a ball or hitting a volleyball. Anterior dislocations also occur during falls on an outstretched hand. An anterior dislocation involves external rotation of the shoulder; that is, the shoulder rotates away from the body.
Posterior dislocations are uncommon and are often associated with specific injuries like lightning strikes, electrical injuries, and seizures. On occasion, this type of dislocation can occur with minimal injury in the elderly, and because X-rays may not easily show a posterior dislocation, the diagnosis is often missed should the patient present for evaluation of shoulder pain and/or decreased range of motion of the shoulder joint.
A shoulder separation is a totally different injury and does not involve the gleno-humeral shoulder joint. Instead, the acromio-clavicular joint is involved. This is where the clavicle (collarbone) and acromion (part of the shoulder blade) come together in the front of the shoulder. A direct blow laterally, often from falling directly onto the outside part of the shoulder, damages the joint, the cartilage inside, and the numerous ligaments that maintain stability. While there may be pain and swelling at the end of the collarbone, the patient usually is able to somewhat move the shoulder itself.
Medically Reviewed by a Doctor on 6/6/2016