Objective To explore the feasibility and early effectiveness of computer-simulated osteotomy based on the health-side combined with guide plate technique in the treatment of cubitus varus deformity in adolescents. Methods The clinical data of 23 patients with cubitus varus deformity who met the selection criteria between June 2019 and February 2023 were retrospectively analyzed. There were 17 males and 6 females, ranging in age from 4 to 16 years with an average of 8.5 years. The time from injury to operation was 1-4 years. The angle of distal humerus rotation was defined by humeral head posterior inclination angle using low radiation dose CT to scan the patient’s upper extremity data at one time, and the preoperative rotation of the distal humerus on the affected side was (33.82±4.39)°. The CT plain scan data were imported into 9yuan3D digital orthopaedic system (V3.34 software) to reconstruct three-dimensional images of both upper extremities. The simulated operation was performed with the healthy upper extremity as the reference, the best osteotomy scheme was planned, overlapped and compared, and the osteotomy guide plate was prepared. The patients were followed up regularly after operation, and the formation of callus in the osteotomy area was observed by X-ray examination. Before and after operation, the carrying angle of both upper extremities (the angle of cubitus valgus was positive, and the angle of cubitus varus was negative) and anteversion angle were measured on X-ray and CT images. At the same time, the flexion and extension range of motion of elbow joint and the external rotation range of motion of upper extremity were measured, and Mayo score was used to evaluate the function of elbow joint. ResultsThe operation time ranged from 34 to 46 minutes, with an average of 39 minutes. All patients were followed up 5-26 months, with a mean of 14.9 months. All the incisions healed by first intention after the operation; 2 patients had nail path irritation symptoms after Kirschner wire fixation, which improved after dressing change; no complication such as breakage and loosening of internal fixators occurred after regular X-ray review. Continuous callus formed at the osteotomy end at 4 weeks after operation, and the osteotomy end healed at 8-12 weeks after operation. At last follow-up, the carrying angle, anteversion angle, external rotation range of motion, and extension and flexion range of motion of the elbow joint of the affected side significantly improved when compared with preoperative ones (P<0.05). Except for the extension range of motion of the healthy elbow joint (P<0.05), there was no significant difference in other indicators between the two sides (P>0.05). At last follow-up, the Mayo elbow score was 85-100, with an average of 99.3; 22 cases were excellent, 1 case was good, and the excellent and good rate was 100%. ConclusionComputer-simulated osteotomy based on health-side combined with guide plate technique for treating cubitus varus deformity in adolescents can achieve precise osteotomy, which has the advantages of short operation time and easy operation, and the short-term effectiveness is satisfactory.