Objective • This study was to analyze and compare the clinical efficacy of open reduction and internal fixation through posterolateral and the posterior medial approach to treat Haraguchi Type II posterior malleolar fracture. Methods • The clinical data of 91 patients with trimalleolar fractures sent to our hospital from January 2018 to January 2020 were analyzed. All of the patients were the result of traumatic injuries, such as sprains or car accidents. All patients were treated with open reduction and internal fixation and divided into control group and observation group according to different surgical approaches. Forty-five cases were treated with the posterolateral approach(control group) and forty-six cases treated with the posteriormedial approach(observation group) . The operation status of the two groups (operating time, intraoperative blood loss, postoperative drainage, and hospital stay), postoperative status (visual analogue scale (VAS) before the operation, 1d, 3d and 7d after operation), the score of patient’s American orthopedic foot and ankle society (AOFAS) at the time of discharge, fracture healing time and full weight-bearing time), efficacy and safety were recorded. Results • All cases underwent surgery, with no significant difference in the time from fracture to surgery between the control and observation groups (P > .05). Compared to the control group, the operating time, intraoperative blood loss, postoperative drainage, and hospital stay in the observation group were significantly reduced (P < .05). One day after the operation, no significant difference was shown in VAS between 2 groups (P > .05), while AOFAS score in the observation group was significantly increased (P < .05). Three and 7 days after the operation, VAS, fracture healing time, and full weight-bearing time were significantly decreased in both groups (P < .05). In the control group, the cases with excellent, good, fair, and poor efficacy were 26, 8, 5, 6, with an acceptable rate of 86.67% (39/45). In the observation group, the cases with excellent, good, fair, and poor efficacy were 29, 10, 5, and 2, with an acceptable rate of 95.65% (44/46). There was no significant difference in efficacy between the 2 groups (P > .05). During the follow-up time of 12~27 months (the median time of 18.5 months), all patients showed first-stage grade A healing, and osseous union with good fixation position and no fracture, deformation, loosening or prolapse, and no sural nerve injury or incision infection occurred. Conclusion • Both the posterolateral approach and posterior medial approach open reduction and internal fixation can be used to treat Haraguchi type II posterior malleolus fractures, with good efficacy and safety. The posterior medial approach showed faster recovery and less damage than the posterolateral approach. Overall, the posterolateral approach is more dominant in the treatment of Haraguchi Type II posterior malleolar fracture. [ABSTRACT FROM AUTHOR]