Objective:To explore the effects of residual rotational deformity after supracondylar fractures of the humerus on the surgical efficacy in children.Methods:From January 2020 to December 2021, 453 patients with Gardland type Ⅲ supracondylar humeral fracture were treated with closed reduction and percutaneous pinning at Department of Pediatric Orthopedics, The Second Hospital of Fuzhou. They were assigned into 2 groups according to the quality of reduction. In the group of residual rotational deformity of 69 cases (group A), there were 44 boys and 25 girls, with an age of (6.3±2.9) years. The Baumann angle was maintained at 65° to 80° on the anteroposterior view of intraoperative fluoroscopy and the anterior humeral line passed through the anterior 1/3 of the capitellum on the lateral view with a normal carrying angle (from 4° to 23°). In the anatomical reduction group of 384 patients (group B), there were 242 boys and 142 girls, with an age of (5.9±2.7) years. The anteroposterior view and the lateral view of intraoperative fluoroscopy showed anatomical reduction of the fracture ends. The fluoroscopy frequency, operation time, intraoperative carrying angle, the carrying angle at 6 months after operation and the Flynn score at 6 months after operation were recorded and compared between the 2 groups.Results:There was no significant difference in gender, age, side or fixation time between the 2 groups before operation, showing they were comparable ( P>0.05). All patients were followed up for (6.3±2.9) months after operation. The median intraoperative fluoroscopy frequency was 6 (4, 6) times in group A, significantly lower than that in group B [8(6, 8)], and the median operation time was 20 (20, 25) min in group A, significantly shorter than that in group B [30(25, 30) min] ( P<0.05). There was no significant difference between group A and group B in the intraoperative rying angle (19.7°±2.7° versus 20.2°±2.8°) or in the carrying angle at 6 months after operation (17.4°±2.7° versus 17.6°±2.7°) ( P>0.05). By the Flynn scoring for the elbow joint at 6 months after operation, group A had 28 excellent cases, 30 good cases, 9 moderate cases, and 2 poor cases, yielding an excellent and good rate of 84.1%(58/69); group B had 241 excellent cases, 104 good cases, 34 moderate cases, and 5 poor cases, yielding an excellent and good rate of 89.8%(345/384). There was no statistically significant difference between the 2 groups ( P>0.05). No cubitus varus, delayed union, non-union, compartment syndrome, or iatrogenic ulnar nerve injury was observed in either group at postoperative 6-month follow-up. Conclusions:A certain degree of residual rotational deformity is acceptable after supracondylar fracture of the humerus in children, because it may have a little significant effect on the postoperative outcomes but may reduce fluoroscopy frequency and shorten operation time.