Subluxation of the radial head is common among preschool children. The peak age is between 1 and 4 years, and it is usually not seen in children older than 7 years. The mechanism of injury is sudden traction on the hand with the elbow extended and the forearm pronated. Anatomically, during forceful traction, some fibers of the annular ligament, which encircles the radial neck, slip and become trapped between the radial head and capitellum. In the child up to age 5, the radial head is about the same size as the neck. After age 7, the size of the radial head is larger than the neck and subluxation does not occur.
Clinically the child sits comfortably with the parent, may even be playful, but does not use the injured arm. The arm is held in slight flexion and pronation. Supination is painful, and any effort to move the arm is resisted, although movement is free. The neurovascular examination is normal.
It is important to elicit the history of traction on the hand; the act may have been unrecognized by the parent or playmate or the history withheld because of a feeling of guilt or fear. Recently, an atypical history has been reported to occur in as many as 49 percent of radial head subluxations. Any child not using an arm that is flexed and pronated and without signs of trauma should be considered to have a radial head subluxation unless the history strongly suggests another diagnosis. Radiographs are unnecessary unless another diagnosis is being considered or if reduction is not accomplished.
Reduction is carried out by firmly placing the thumb over the radial head while the other hand is placed on the wrist. The forearm is fully supinated, and if a "click" is not felt, the elbow is flexed. This maneuver may be repeated if the initial attempt does not reduce the subluxation. Alternatively, the elbow may be extended. Both maneuvers are reported to be equally effective. Reduction as evidenced by a click is highly predictive and will result in relief from pain and, shortly thereafter, use of the affected arm.
After the first subluxation, no immobilization is required. For recurrent subluxations, however, orthopedic referral is needed. The patient's arm should be immobilized in a sling; some recommend a long-arm cast. Teach et al found a recurrence rate of 23.7 percent in either arm and 19.4 percent in the ipsilateral arm. Children 24 months or younger had a relative risk of 2.6 for recurrence when compared to children older than 24 months.
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