Objective:To explore application of the mixed reality (MR) technique in the surgery for complex pilon fractures.Methods:A retrospective analysis was conducted of the 22 patients with pilon fracture of Rüedi-Allg?wer type Ⅲ who had been treated at the Department of Orthopedics, Nanjing Tongren Hospital from May 2018 to October 2020. They were divided into 2 groups according to their treatment procedures. In the MR group of 9 cases, there were 8 males and one female, with an age of (39.2 ± 15.1) years. In addition to calcaneal traction plus open reduction and internal fixation, the MR technique was used to assist doctor-patient communication, preoperative planning, surgical guidance and rehabilitation exercises. In the control group of 13 male cases with an age of (33.7 ± 9.6) years, only conventional calcaneal traction plus open reduction and internal fixation were carried out. The communication efficiency, operation time, intraoperative blood loss, fluoroscopy frequency, fracture reduction, post-operative complications and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score at one year postoperatively were recorded and compared between the 2 groups.Results:There was no significant difference in the general data between the MR group and the control group, showing they were comparable ( P > 0.05). The questionnaire score of patients' surgical awareness [(77.8 ± 19.2) points] in the MR group was significantly higher than that in the control group [(50.0 ± 30.6) points] ( P = 0.017). The fluoroscopy frequency [(7.3 ± 2.6) times] in the MR group was significantly lower than that in the control group [(9.5 ± 2.3) times] ( P = 0.043). No significant differences were observed between the 2 groups in either the operation time [(98.3 ± 14.4) min versus (110.4 ± 20.4) min] or the intraoperative blood loss [(118.9 ± 36.5) mL versus (128.8 ± 35.2) mL] ( P = 0.142, P = 0.527). In the MR group, 8 cases achieved anatomical reduction and one case good reduction; in the control group, 4 cases achieved anatomical reduction, 8 cases good reduction and one case poor reduction. The anatomical reduction in the MR group was significantly better than that in the control group ( P = 0.011). There were one case of delayed wound healing, one case of nonunion, and one case of traumatic osteoarthritis in the MR group while there were 2 cases of delayed wound healing, one case of superficial soft tissue infection, one case of nonunion, and 2 cases of traumatic osteoarthritis in the control group. The average AOFSA ankle-hindfoot score at one year postoperatively in the MR group [(83.8 ± 9.0) points] was significantly higher than that in the control group [(73.3 ± 11.8) points] ( P = 0.035). However, there was no significant difference between the MR group and the control group in the good to excellent rate by the AOFSA ankle-hindfoot score at one year postoperatively (6 excellent cases, one good case, and 2 fair cases in the former versus 6 excellent cases, 2 good cases, 4 fair cases, and one poor case in the latter) ( P = 0.648). Conclusions:In the surgery for complex pilon fractures, MR technique can increase the efficiency of doctor-patient communication, reduce intraoperative fluoroscopy frequency, and improve reduction quality and ankle function, but fails to significantly reduce operation time and intraoperative blood loss.