Objective:This study aimed to investigate the impact on nonunion of the extent of comminution and postoperative displacement in patients surgically treated for subtrochanteric fractures.Methods:From 2008 to 2013, 44 patients with subtrochanteric fractures underwent surgery and follow-up. Retrospective data collection showed that it had 32 male and 12 female. Their mean age was 45 years. The case distribution according to Seinsheimer classification was as follows: IIA,8; IIB, 5; IIC, 7; IIIA, 8; IIIB, 3; IV, 9; and V, 4. Cephalomedullary nails were used in 28 cases; ordinary nails, in 9; and plates, in 7. After surgery, the fractures were evaluated for displacement on anteroposterior (AP) and lateral radiography.Results:Of the 44 patients, 37 achieved union from primary surgery at a mean time of 8.4 months. Five cases did not show union within the follow-up period. Two cases of nail breakage were diagnosed as non-union. Among the non-union cases, two were Seinsheimer classification IIIA; 3, IV; and 2, V. Displacement was observed on the lateral and A Pradiographs of 4 cases, on only the lateral radiographs of two cases, and in neither radiograph of one case. The risk of non-union was approximately 15.4 and 24.2 times higher when displacement was observed on the AP (95% confidence interval [CI]: 1.33–176.82) and lateral images (95% CI: 1.76–335.67), respectively.Conclusion:When displacement occurred after surgical treatment for subtrochanteric fractures, the risk of nonunion increased owing to the difficulty achieving stable fixation.