Abstract:[Objective] To compare the efficacy of ulna osteotomy with and without internal fixation for old Monteggia fractures in chil- dren. [Methods] From July 2018 to July 2020, a total of 79 children underwent ulnar osteotomy and open radiocapitellar reduction com- bined plaster cast fixation for old Monteggia fractures. According to preoperative doctor-patient communication, 42 children had osteotomy site fixed with internal implant (fixation group) , while the other 37 had osteotomy performed only without internal fixation (the non-fixation group). The perioperative, follow-up and imaging data of the two groups were compared. [Results] All patients had the operations complet- ed successfully. The non-fixation group proved significantly superior to the fixation group in terms of operation time, incision length, times of fluoroscopy, incision healing and hospital stay (P<0.05) . All the patients were followed up for more than 12 months. The non-fixation group resumed full weight-bearing activity significantly earlier than the fixation group (P<0.05) . Th range of motions (ROMs) , including pronation, supination, elbow flexion and extension, as well as Mayo elbow score significantly increased over time in both groups (P<0.05) , however, there were no statistically significant differences in abovesaid items between the two groups at any corresponding time points (P> 0.05) . Radiographically, the alignments in term of radiocapitellar line (RCL) and extent of radiocapitellar congruence (RCC) significantly improved in both groups over time (P<0.05) , which in the non-fixation group was significantly superior to those in the fixation group at the latest follow-up (P<0.05) . In addition, the non-fixation group got bony healing of the osteotomy site on images significantly earlier than the fixation group (P<0.05) . [Conclusion] The clinical outcomes of ulna osteotomy without internal fixation are considerably better than those with internal fixation in the surgical treatment of old Monteggia fractures in children.