A shoulder dislocation occurs when the head of the upper arm bone known as the humerus is displaced from its cup-shaped socket in the shoulder blade. Although this dislocation can occur in several directions, 95-98% of the time the shoulder dislocates anteriorly towards the front of the body.
The shoulder joint is a complex arrangement of bones and soft tissues designed to enable a wide range of arm movement as well as support such demanding actions as lifting, pulling, or pushing. The ability to move in many directions makes the shoulder the most mobile joint in the body. However, this distinction also leaves the shoulder more susceptible to dislocation.
The shoulder joint is a ball-and-socket joint formed between the articulation of the rounded head of the humerus (the upper arm bone) and the glenoid fossa, a shallow cavity in the scapula (shoulder blade). Not being a snug fit, this relationship permits tremendous joint flexibility but does not provide much in the way of stability. The shoulder relies on the surrounding cartilage ligaments, tendons, and muscles for its stability.
Shoulder dislocations are defined by where the head of the humerus ends up after it has been displaced from the glenoid fossa. Anterior dislocations are invariably traumatic and are often associated with contact sports, accidents, or falls. In older individuals an anterior shoulder dislocation is typically the result of trauma from a fall.
The small percentage of cases of posterior shoulder dislocations that occur are almost always associated with circumstances like lightening strikes, electrical injuries, or seizures. However, there are instances where this dislocation may be the result of a direct traumatic blow.
A shoulder dislocation can be accompanied by additional complications including:
Local nerve and artery damage
Associated fractures of the head of the upper arm, collarbone & shoulder blade
Tearing of the muscles, ligaments and tendons that stabilize the joint
An increased risk of recurrent shoulder dislocation
In cases of a shoulder dislocation immediate medical attention is required. Applying ice to the shoulder area will help reduce swelling and alleviate the acute pain. There may be numbness, tingling or weakness in the arm, hand, and fingers. To avoid additional damage, it is important not to move the shoulder or try to force it back into place.
The doctor will take a complete history, examine the shoulder, and order imaging tests to show the dislocation and associated injuries. If this is the first time the shoulder has dislocated and there is no major nerve or tissue damage a closed reduction will be performed. In situations where there have been recurring dislocations or nerve and blood vessel injury has occurred, surgery may be indicated. Either way once the joint is back in position a special splint or sling will be worn for a recommended period of time. A gradual rehabilitation program to restore full strength and function will be prescribed once the pain and swelling have subsided. Recovery time depends on the severity of the dislocation and damage.