A child exhibits a slight flexion and full pronation of the right arm after being swung in circles. What diagnosis is likely?

In the scenario described, the child's presentation of slight flexion and full pronation of the right arm, particularly after being swung in circles, is consistent with nursemaid's elbow, also known as radial head subluxation. This injury commonly occurs in young children and usually results from a sudden pulling or twisting motion on the arm, which can easily happen when a child is swung around by their arms.

In nursemaid's elbow, the radial head slips out of its normal position at the elbow joint. This often leads to a characteristic posture in which the child holds the affected arm slightly flexed and in a pronated position (palm facing down). The child typically refuses to use the affected arm and may show signs of discomfort. The mechanism of injury aligns well with swinging actions, which can create a forceful distraction on the arm.

The other potential diagnoses, such as a fractured arm, radial head fracture, or shoulder dislocation, are less likely given this specific clinical presentation and history. A fractured arm would likely present with more significant pain, swelling, or deformity. A radial head fracture typically would require a more direct trauma to the elbow rather than a twisting or swinging motion. Shoulder dislocation would present with more severe pain and limitations in shoulder