Operative versus non-operative treatment of posterior malleolus fragment in trimalleolar fracture: a retrospective cohort study

Introduction: The treatment of Posterior Malleolus (PM) fracture in trimalleolar surgery is still controversial. Fixation of PM is determined according to joint congruency and posterior fragment size. When the ratio of posterior fragment is less than 25% of anteroposterior dimension of the articular surface, conservative treatment is suggested in the literature. The aim of this study was to evaluate the functional and radiological outcomes of the patients with trimalleolar fracture that had either PM fixation or not when the PM ratio is less than 25%. Materials and methods: Archives of 73 patients that had trimalleolar surgery in our hospital between 2010 and 2014 were evaluated retrospectively. Inclusion criteria’s were as follow: being over 18 y old, PM fractures measuring less than 25% of the joint surface in the lateral ankle x-ray, having preoperative ankle Computer Tomography (CT) , both medial and lateral malleolar fixation, with at least 2 y of follow-up. Exclusion criteria’s were as follow: pathologic fractures, metabolic disorders, ipsilateral fracture, fracture history in the same ankle, incongruous talocrural angle, medial and superior talo tibial incongruity in the postoperative early x-rays. Haraguchi classification, PM size and ratio, use of transsyndesmotic screw, American Orthopaedic Foot and Ankle Society (AOFAS) anklehind foot scores were evaluated. Kolmogorov-Smirnov was used to evaluate the distribution of the variables and Mann-Whitney U-test was used for statistical analysis. Results: Among the patients who had PM fixation and without fixation, there was no statistically significant difference in their AOFAS score. Conclusions: There was no significant functional difference found in trimalleolar fracture when PM fraction ratio is smaller than 25% in comparison of PM fixation, however, the decreased need of transsyndesmosis fixation needs to be taken into consideration.