Pulled elbow (also known as nursemaid's elbow) is a subluxation of the radial head into the annular ligament, which usually spontaneously or easily reduces and rarely demonstrates abnormal radiographic features. If the clinical presentation is atypical, pulled elbow should be distinguished from elbow fractures or radial head dislocations, which is where radiographs can be helpful 7.
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Epidemiology
Pulled elbows are encountered in young children (typically between 6 months and 3 years of age) 1, as a result of pulling on the arm longitudinally, as occurs when yanking a child away from something the parents would rather they not touch, or lifting the child in play (fathers are much more likely to do this ref).
Clinical presentation
Children with a pulled elbow will hold the elbow flexed and the forearm pronated, unwilling to supinate 1.
Pathology
The propensity of young children to develop pulled elbows most likely stems from a generalised ligamentous laxity, which also affects the annular ligament, allows the radial head to sublux into it. In the younger children, this results in no ligamentous damage, whereas in older children partial tears are thought to occur, accounting for the persistence of pain a number of days following reduction 1.
Radiographic features
Plain radiograph
Radiography is unhelpful in making the diagnosis with radiographs mostly appearing normal 6. Inadvertent reduction may occur as the radiographer supinates the elbow to obtain an AP view 1-2.
Ultrasound
Using an anterior, longitudinal view across the radiocapitellar joint, the following findings are sought;
- interposition of the supinator muscle into the joint space 4,5
- appearing to curl over the radial head forming the "hook" or "J" sign
- inability to visualise the annular ligament
- restoration of normal anatomy after reduction 3
Treatment and prognosis
Supination with the elbow flexed almost always results in a reduction, and in infants almost immediate cessation of symptoms. Older children may have a number of days of ongoing discomfort. Only rarely is closed reduction unsuccessful.
A number of patients will have recurrent episodes, however, with growth, these occur less and less frequently 1,2.