ObjectiveTo investigate the effectiveness of fixation the posterior malleolus or not to treat different Haraguchi’s classification of posterior malleolus fractures.MethodsThe clinical data of 86 trimalleolar fracture patients who were admitted between January 2015 and September 2019 and met the selection criteria were retrospectively reviewed. There were 29 males and 57 females; the age ranged from 26 to 82 years with a mean age of 55.2 years. According to Haraguchi’s classification, 38 patients were in type Ⅰ group, 30 patients in type Ⅱ group, and 18 patients in type Ⅲ group. There was no significant difference in the general data such as gender, age, and fracture location among the 3 groups (P>0.05). The fixation of the posterior malleolus was performed in 23, 21, and 5 patients in type Ⅰ, Ⅱ, and Ⅲ groups, respectively. The operation time, fracture healing time, full weight-bearing time, postoperative joint flatness, and joint degeneration degree of the patients in each group were recorded and compared. The American Orthopedic Foot and Ankle Society (AOFAS) ankle and hindfoot score was used to evaluate ankle function, including pain, quality of daily life, joint range of motion, and joint stability. The AOFAS scores were compared between fixation and non-fixation groups in each group.ResultsThe procedure was successfully completed by all patients in each group, and there was no significant difference in operation time (F=3.677, P=0.159). All patients were followed up 12-36 months with a mean time of 16.8 months. At last follow-up, 6 patients were found to have suboptimal ankle planarity, including 2 patients (5.3%) in the type Ⅰ group and 4 patients (13.3%) in the type Ⅱ group, with no significant difference between groups (χ2=6.566, P=0.161). The ankle joints of all the patients in each group showed mild degeneration; the fractures all healed well and no delayed union or nonunion occurred. There was no significant difference in the fracture healing time and full weight-bearing time between groups (P>0.05). No complications such as incision infection, fracture displacement, or plate screw loosening and fracture occurred during follow-up. At last follow-up, the total scores and pain scores of the AOFAS scores in the type Ⅱ group were significantly lower than those in the type Ⅰand Ⅲ groups (P<0.05), there was no significant difference between groups in the scores for the quality of daily life, joint range of motion, and joint stability between groups (P>0.05). There was no significant difference in any of the scores between the unfixed and fixed groups, except for the pain and quality of daily life scores, which were significantly lower (P<0.05) in the unfixed group of type Ⅱ group than the fixed group.ConclusionHaraguchi type Ⅱ posterior malleolus fractures have a worse prognosis than types Ⅰ and Ⅲ fractures, especially in terms of postoperative pain, which can be significantly improved by fixing the posterior malleolus; the presence or absence of posterior malleolus fixation in types Ⅰ and Ⅲ has less influence on prognosis.