ObjectiveTo explore the effectiveness of modified Ilizarov semi-ring external fixator combined with an ulnar osteotomy lengthening in the treatment of old dislocation of the radial head in children. MethodsA retrospective analysis was made on the data of 14 patients with old dislocation of the radial head treated by the modified Ilizarov semi-ring external fixator combined with ulnar osteotomy lengthening between March 2012 and January 2015. The age ranged from 2 to 13 years (mean, 7.2 years), including 12 boys and 2 girls. There was 1 case of congential dislocation of the radial head and 13 cases of old Monteggia fracture. According to the Bado's classification, dislocation was rated as grade Ⅰ in 12 cases and grade Ⅲ in 2 cases. The elbow flexion-extension and forearm pronation and supination were compared between at pre- and post-operation; Mackay evaluation standard of elbow joint function was used to evaluate the effectiveness. ResultsThe operation time ranged from 50 to 65 minutes (mean, 58 minutes). All patients were followed up 6-33 months (mean, 21 months). No complication of infection, myositis ossificans, or redislocation occurred. X-ray film showed bony healing at ulnar osteotomy site within 82-114 days (mean, 90 days). The elbow flexion-extension and forearm pronation and supination were significantly improved at postoperation when compared with preoperation (P<0.05). The results of Mackay function assessment were excellent in 12 cases and good in 2 cases. ConclusionThe modified Ilizarov semi-ring external fixator combined with an ulnar osteotomy lengthening has the advantages of small incision, easy removal of fixator, satisfactory reduction, and no nonunion at ulnar osteotomy site in the treatment of old dislocation of the radial head, but the long-term effectiveness still needs to be followed up.