Posterior shoulder dislocation occurs when the top of the upper arm bone, known as the humerus, moves backward out of its socket. This causes pain, muscle spasms, and a limited range of motion.
The shoulder accounts for
In this article, we will discuss what posterior shoulder dislocations are, their symptoms, causes, and treatment.
A posterior shoulder dislocation, or glenohumeral dislocation, happens when the head of the humerus moves backward out of its socket.
The shoulder girdle houses the ball-and-socket joint of the shoulder. The glenoid bone forms an
Where a posterior dislocation pushes the humerus backward, toward the shoulder blade, an anterior dislocation pushes the head of the bone forward, toward the chest.
The table below summarizes some of the differences between each condition:
|Anterior dislocation||Posterior dislocation|
|Location||Front of shoulder joint||Back of shoulder joint|
|Causes||A blow to the back of the arm with the arm rotated away from the body and extended||A blow to the front of the shoulder or violent muscle contractions|
|Treatment||Tends to be easier to put back into place||Tends to be harder to put back into place, in comparison to anterior dislocations|
|Complications||Common, occurring in ||Higher risk of certain fractures and injuries to the labrum or rotator cuff|
The symptoms of a posterior shoulder dislocation
- severe pain
- muscle spasms
- a limited range of motion
Injuries that push the humerus backward, or muscle contractions that have the same effect, can cause a posterior shoulder dislocation. This can include many types of blows or twists, but some common causes include:
- blunt force to the front of the shoulder, such as during a car collision
- falling on an outstretched hand
- electric shock
A posterior shoulder dislocation can be difficult to diagnose. Doctors may not feel enough displacement of the humerus to warrant a diagnosis, or they may see that the person can still move the joint and conclude that they do not have a dislocation.
Therefore, doctors should maintain a
For any shoulder injury, a doctor takes a person’s history, including:
- which arm is dominant
- site and intensity of the pain
- when the injury happened
- factors that aggravate and alleviate the injury
- whether the pain radiates
- how the injury occurred
- range of movement in the arm
If they suspect dislocation, doctors may order X-rays, or they
Treating a shoulder dislocation involves putting the bone back into its place. This can be very painful, so a person may receive lidocaine or bupivacaine injections first to help with managing their pain.
Putting a dislocated bone back into place is known as a reduction, as it involves reducing the space between the dislocated bones of a joint. Doctors may use one of
The procedure is successful when the person experiences a “clunk” as the shoulder goes back into place. This relieves their pain, and the person can place the palm of the affected arm on the opposite shoulder.
After reduction, doctors will perform more scans to check for any signs of injury, such as fractures or soft tissue damage. If there are none, a person will be able to go home, but they will need to wear a sling to immobilize the arm for
If a person receives a delayed diagnosis, their dislocated shoulder may be “locked” into place, making it harder to treat. If this is the case, or there is other damage to the joint and surrounding tissue, a doctor may suggest other treatments, such as:
- surgical reconstruction of the joint
- tendon transfer surgery, which can treat problems with muscles and tendons
- hemiarthroplasty, which involves replacing the head of the humerus with a metal ball
- total shoulder arthroplasty, which replaces both the ball and the socket of the shoulder
There are several potential complications of a posterior shoulder dislocation, including:
- Soft tissue injuries: Shoulder dislocation can damage the tendons and muscles in or around the joint. This may result in injuries that require additional treatment, such as a rotator cuff tear.
- Joint instability: Once a person dislocates their shoulder, it is more prone to dislocating again in the future. Posterior shoulder dislocations reoccur in
- Fractures: An injury that causes dislocation may also cause bone fractures of the humerus, glenoid, and other bones around the shoulder joint. Some fractures, such as reverse Hill-Sachs deformities, have links to long recovery times and a higher likelihood of reoccurrence.
- Unsuccessful reduction: Reductions are not always successful. Some people may need surgery to correct the dislocation.
- Nerve damage: The brachial plexus includes the nerves that send impulses from the spinal cord to the shoulder, arm, and hand. Injury of the brachial plexus is a
rare, but potentially severe, complication of a shoulder dislocation. Axillary nerve injuries are also possible, but they are not usuallyserious. A person often recovers without intervention.
Older people are more susceptible to soft tissue injury and joint instability following a shoulder dislocation. Repeated dislocations can also lead to degenerative changes in the joint.
Posterior shoulder dislocations occur when force or muscle contractions push the shoulder backward, dislodging the upper arm bone out of its socket. The vast majority of shoulder dislocations are anterior, with only
The symptoms of a posterior shoulder dislocation include severe pain and muscle spasms, but it can be a hard condition to diagnose. Treatment includes putting the shoulder back into place. In cases where the shoulder has become locked or there are other forms of damage, a person may require surgery.