Background:In treatment of ankle fracture,intraoperative stress tests are used to assess the syndesmotic injury and instability.However,the optimized timing of the strees test should be applied whether in pre-or post-bony fixation during operation is seldom be reported in previous studies.The different strategies on stress test timing would exhibit opposite results within a type ofpronation-extemal rotation (PER) fractures with supracollicular medial malleolar (SMM) fractures.This study was designed to assess the 3-year functional outcomes of the special PER fractures with or without a syndesmotic transfixation based on the results of two different intraoperative stress test strategies.Methods:This retrospective cohort study included 61 PER injury-Weber C ankle fractures combined with SMM fractures who were treated in Beijing Jishuitan Hospital between 2013 and 2014 and followed up for 3 years.Stress test was performed twice intraoperatively.A positive intraoperative stress test before bony fixation and a negative intraoperative stress test after bony fixation were found in these included patients.Twenty-nine patients (Group 1) were treated without a supplemental syndesmotic screw fixation,according to the negative intraoperative stress test after bony fixation,while 32 patients (Group 2) were treated with an additional syndesmotic screw fixation based on the positive intraoperative stress test before bony fixation.The American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale and Visual Analog Scale (VAS) for pain scores were the main measurements of outcome.The statistical index of demographic data,fracture morphologic data,time interval of follow-up,AOFAS and VAS were recorded and assessed by SPSS 21.0 software through Fisher exact tests and oneway analysis of variance.The associations between the main outcomes and influential factors were evaluated by linear regression models.Results:We observed no difference in the distribution of age,sex,presence of associated posterior malleolus (PM),fracture dislocation,and fixation of associated PM between two treatment groups.With the numbers available,no statistically significant association could be detected with regard to the AOFAS (Group 1 vs.Group 2,96.72 ± 6.20 vs.94.63 ± 8.26,F =1.24,P =0.27) and VAS (Group 1 vs.Group 2,1.47 ± 2.14 vs.0.72 ± 1.49,F=2.44,P =0.12) in association with two strategies.Conclusions:The present study indicates no difference to the use of the syndesmotic screw in terms of the functional outcome between syndesmosis transfixation and no-fixation patients among PER-Weber C ankle fracture patients with SMM fracture after 3-year follow-up.More attention should be paid to pre-and post-bony-fixation intraoperative stress tests and the morphology of medial malleoli fractures in ankle fractures.