To compare the outcomes of the Kocher-Langenbeck reduction and fixation of the posterior structures of the acetabulum between 3D printing technique and conventional technique.Forty-three patients who sustained fractures of the posterior part of the acetabulum were randomly assigned to two groups: 3D printing (G1; n = 20) and conventional technique (G2; n = 23). The surgical time, intra-operative blood loss, differences between pre-and post-operative haemoglobin, universal functional and radiographic scores, and complications were compared between the groups. The minimum follow-up was 18 months.The average operating time (120.75 min) and intra-operative blood loss (244 ml) were lower in G1 than in G2 (125.87 min and 268.7 ml, respectively; p = 0.42, p = 0.1, respectively). The difference between the pre- and post-operative haemoglobin was 1.71 g/dl in G1 and 1.93 g/dl in G2 (p = 0.113). Post-operative complications occurred more frequently in patients in G2 (34.7%) than in patients in G1 (15%), though these differences were also not significant (p = 0.6). The radiographic result was satisfactory in 16 patients (80%) in G1 and 18 patients (78.26%) in G2 (p = 0.5). The clinical result was satisfactory in 15 patients (75%) in G1 and in 17 patients (73.9%) in G2 (p = 0.6).No significant differences were found in terms of surgical time, overall complications, and radiographic or functional outcomes between 3D printing and the conventional technique.