Treatment Strategy for Posterior Malleolar Fractures: Different Operative Strategies Are Needed for Each Morphological Type

<b>Background:</b> The operative indication for posterior malleolar fracture (PMF) remains controversial. This study aimed to assess the midterm outcomes of PMF treatment for developing a treatment strategy for each morphological type. <b>Methods:</b> In this retrospective analysis, patients undergoing operative treatment for an unstable ankle fracture involving PMF were included after at least 3 years of follow-up. PMFs were classified by fracture morphology according to the Haraguchi classification. This study divided the entire cohort into three independent populations based on the types of PMF. For each population, patients were further categorized into two groups depending on whether PMF was surgically fixed or not, and comparisons were made between these two groups. Demographic data, functional and radiographical outcomes were compared between two groups in each of the three populations. <b>Results:</b> With a total of 472 patients, the mean patient age was 45.8 years, and the mean follow-up was 51 months. For type 1 fracture, a total of 237 cases were found. Quality of reduction by CT (QRC) was mostly good in both groups (83.6% vs. 83.3% in the non-fixation vs. fixation group, respectively, <i>p</i> = 0.269). Functional and radiological outcomes between both groups showed no significant difference. For type 2 PMFs, a total of 199 cases were found, and QRC was significantly different between the two groups (good grade, 5.4% vs. 60.7% in the non-fixation vs. fixation group, respectively, <i>p</i> < 0.001). The radiological and clinical outcomes of the PMF fixation group were statistically superior to those of the non-fixation group (both <i>p</i> < 0.001). For type 3 fractures, a total of 36 cases were found. In all the cases in this group, surgical fixation of PMF was not performed. Only the syndesmosis instability was analyzed as a viable factor to be considered for achieving favorable surgical outcomes. PMF fixation group showed significantly more postoperative complications (24.4% vs. 40.4%, non-fixation vs. fixation, respectively, <i>p</i> < 0.001). Major complications in the fixation group were deep wound infection (6.8%), superficial peroneal nerve injury (6.8%), and hallux flexion deficit (5.0%). <b>Conclusions:</b> Different treatment strategies seem to be required for each PMF morphological subtype. Further studies with more detailed designs for each PMFs are warranted for more clinically related results that are helpful for making practical surgical decisions.