BACKGROUND: Congenital radioulnar synostosis (CRUS) causes a spectrum of presentations, most commonly a restriction of forearm rotation. Because most of these children are not treated operatively, many are not followed clinically after the diagnosis has been made. This report describes that a subset of the Cleary and Omer type IV synostoses (anterior dislocation of the radial head) can present with a progressive block to elbow flexion that worsens with growth. The location of this synostosis allows the physis of the radial head to grow untethered. The enlarged radial head can impinge upon the capitellum, blocking elbow flexion and snapping on the annular ligament. We propose excision of the radial head as a method of treating the anteriorly dislocated radial head in type IV synostoses. METHODS: We evaluated 4 patients with Cleary and Omer type IV synostoses who presented with an anteriorly dislocated radial head impinging on elbow flexion with snapping of the annular ligament. Each patient was treated with excision of the radial head. RESULTS: In 4 patients excision of the radial head was performed through a lateral Kocher approach. At follow-up, all patients showed relief from their pain and mechanical symptoms, with return of baseline range of motion. One complication which occurred was transient radial nerve neuropraxia. CONCLUSIONS: Although surgery is rarely needed for CRUS, excision of the radial head may be indicated if progressive loss of elbow flexion occurs secondary to impingement of the anteriorly dislocated radial head with the distal humerus in patients with type IV synostosis. We report that excision of the radial head can successfully treat this condition. Patients with type IV CRUS should be educated about the potential for loss of elbow flexion and/or followed until skeletal maturity to evaluate for this potential condition. LEVEL OF EVIDENCE: Case series consistent with level IV evidence; therapeutic study.