The mechanism of acute elbow flexion contracture in children with congenital proximal radioulnar synostosis.

We have evaluated and treated 3 cases of acute onset elbow flexion contracture in children ranging in age from 6 to 13 years, with type-IV (Cleary and Omer) congenital proximal radioulnar synostosis. All were resolved by manipulative traction under general anesthesia during which an audible elbow "snap" was noted. Two of the cases required surgical treatment of a deformed radial head with good results after a 2 to 4-year follow-up. Our clinical radiographic and intraoperative evidence suggests that the acute onset fixed-flexion contracture results from an anterosuperiorly overgrown dislocated radial head becoming trapped under hypertrophied annular ligament-type tissue after elbow hyperflexion. Excision of the dislocated radial head after release from its entrapment was effective in 2 of the 3 patients in this report, and should be considered.