Background: The aim of this study was to introduce a novel intraoperative lateral ankle dislocation approach during surgical treatment for patients with unstable trimalleolar fractures involving posterior ankle comminuted fractures and compare its effects and safety with those with conventional approach. Methods: From June 2006 to June 2014, 69 patients diagnosed as unstable trimalleolar fractures involving posterior ankle comminuted fracture were included in this study. The patients were divided into intraoperative dislocating ankle group (experimental group) and conventional treatment group (control group) according to surgical modalities. The following parameters including rate of primary healing, healing time, incidence of talus necrosis, incidence of posttraumatic arthritis, functional outcomes according to Baird-Jackson classification system, and any possible complications in two groups were recorded and compared. Results: There were no significant differences regarding the rate of primary healing, healing time and the rate of talus necrosis in two groups (P > 0.05). The incidence of post-traumatic arthritis in experimental and control group were 0 and 24.24% (P = 0.0006), respectively. The rate of excellent and good outcomes were achieved in 91.67% in experimental group and 72.73% in control group (P = 0.038), respectively. Conclusions: The findings suggest that the intraoperative ankle dislocation approach appears to be a promising surgical option for unstable trimalleolar fractures involving posterior ankle comminuted fracture because it can provide better functional outcomes and lower incidence of post-traumatic arthritis while not compromising primary healing and healing time.