When the joint surfaces of an elbow are separated, the elbow is dislocated. Elbow dislocations can be complete or partial, and usually occur after a trauma, such as a fall or accident. In a complete dislocation, the joint surfaces are completely separated. In a partial dislocation, the joint surfaces are only partly separated. A partial dislocation is also called a subluxation.
Three bones come together to make up the elbow joint. The humerus is the bone in the upper arm. Two bones from the forearm (the radius and the ulna) form the lower part of the elbow. Each of these bones has a very distinct shape.
Ligaments connected to the bones keep the elbow joint together and the bones in proper alignment.
The elbow is both a hinge joint and a ball and socket joint. As muscles contract and relax, two unique motions occur at the elbow.
Injuries and dislocations to the elbow can affect either of these motions.
Elbow dislocations are not common. Elbow dislocations typically occur when a person falls onto an outstretched hand. When the hand hits the ground, the force is sent to the elbow. Usually, there is a turning motion in this force. This can drive and rotate the elbow out of its socket. Elbow dislocations can also happen in car accidents when the passengers reach forward to brace for impact. The force that is sent through the arm can dislocate the elbow, just as in a fall.
The elbow is stable because of the combined stabilizing effects of bone surfaces, ligaments, and muscles. When an elbow dislocates, any or all of these structures can be injured to different degrees.
A simple dislocation does not have any major bone injury.
A complex dislocation can have severe bone and ligament injuries.
In the most severe dislocations, the blood vessels and nerves that travel across the elbow may be injured. If this happens, there is a risk of losing the arm.
Some people are born with greater laxity or looseness in their ligaments. These people are at greater risk for dislocating their elbows. Some people are born with an ulna bone that has a shallow groove for the elbow hinge joint. They have a slightly higher risk for dislocation.
A complete elbow dislocation is extremely painful and very obvious. The arm will look deformed and may have an odd twist at the elbow.
A partial elbow dislocation or subluxation can be harder to detect. Typically, it happens after an accident. Because the elbow is only partially dislocated, the bones can spontaneously relocate and the joint may appear fairly normal. The elbow will usually move fairly well, but there may be pain. There may be bruising on the inside and outside of the elbow where ligaments may have been stretched or torn. Partial dislocations can continue to recur over time if the ligaments never heal.
During the physical examination, your doctor will examine your arm, checking for tenderness, swelling, and deformity. He or she will evaluate the skin and circulation to the arm. Pulses at the wrist will be checked. If the artery is injured at the time of dislocation, the hand will be cool to touch and may have a white or purple hue. This is caused by the lack of warm blood reaching the hand.
It is also important to check the nerve supply to the hand. If nerves have been injured during the dislocation, some or all of the hand may be numb and not able to move.
An x-ray is necessary to determine if there is a bone injury. X-rays can also help show the direction of the dislocation.
X-rays are the best way to confirm that the elbow is dislocated. If bone detail is difficult to identify on an x-ray, a computed tomography (CT) scan may be done. If it is important to evaluate the ligaments, a magnetic resonance image (MRI) can be helpful, however, it is rarely required.
First, however, the doctor will set the elbow, without waiting for the CT scan or MRI. These studies are usually taken after the dislocated elbow has been put back in place.