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Radial head subluxation is also referred to as a nursemaid's elbow, pulled elbow, or annular ligament displacement. It usually occurs primarily in children 1 - 4 years old (peak 2 -3 years), but has been reported both younger and older. Girls have a higher incidence as does the left arm over the right.
The most common cause of the subluxation is from sudden traction placed on the distal radius causing the annular ligament to slip over the head of the radius and trapping it in the radiohumeral joint. This occurs most frequently when axial traction is placed on a pronated forearm as when an adult pulls a child quickly by one arm or is swung by the arm. Although this is the classic story it is only present 50 percent of the time.
As the child develops the annular ligament becomes thicker and is much less likely to be displaced causing the subluxation (around 5 years of age).
A child with a radial head subluxation will usually hold their affected arm close to their body with the elbow slightly flexed and their forearm pronated. The child often will not complain of pain in the arm unless an attempt is made to move the elbow. Often there is no elbow pain, even with passive range of motion, although some children will have pain on the lateral aspect of the radial head. Almost always there is pain with supination of the forearm.
Radial head subluxation is a clinical diagnosis that does not require x-rays. However, fractures and other dislocations can sometimes have similar presentations. X-rays should be obtained only if the history and physical exam are not consistent with the diagnosis.
Both hyperpronation and supination/flexion have been shown to be effective methods of reduction. There have been several studies and a metaanalysis looking at the likelihood of reduction. Pronation resulted in statistically significantly less failure than supination (21/177 versus 47/181, risk ratio 0.45; 95% confidence interval 0.28 to 0.73). In addition, the studies pointed towards decreased pain with hyperpronation.
Most patients are able to tolerate the procedure without analgesia or sedation. However, it is important to tell the caregivers ahead of time that although brief, there is a small amount of pain associated with the procedure.
Patients who have had one radial head subluxation are more likely to have another event if they sustain a similar mechanism (27 – 39 percent). Usually by four or five years of age the annular ligaments strengthens and the likelihood of the subluxation become much less.
If after several attempts reduction is still elusive, the provider should obtain x-rays of the arm for potential fractures. If the x-rays are normal and the child still refuses to use the arm they should have the arm slinged and a referral should be made to an orthopedist. Of note, there are no long-term sequelae that have been reported for unreduced subluxations.