Abstract:[Objective] To compare clinical outcome of percutaneous anteroposterior lag screw versus open posteroanterior lag screw for fixation of Haraguchi type I posterior malleolar fractures. [Methods] Between January 2013 and June 2017, 49 pa? tients who underwent surgical treatment for posterior malleolar fractures enrolled into this study. Based on orientations of lag screw placed, 24 patients had percutaneous lag screws placed anterior-posteriorly (the AP group) , while the remaining 25 pa? tients had open screw inserted posterior-anteriorly (the PA group) for fixation of posterior malleolar fractures. The periopera? tive, follow-up and radiographic documentations were compared between the two groups. [Results] All patients had surgical pro? cedures performed smoothly. Although no a statistical difference was proved in operation time between the two groups (P>0.05) , the AP group had significantly more frequency of fluoroscopy, significantly shorter fibular incision length, and significantly less intraoperative blood loss than the PA group (P<0.05) . The follow-up period lasted for (17.61±3.85) months on average. There was no a statistically significant difference in time to return to full-weight bearing ambulation between the two group [(88.13± 9.47) days vs (87.84±8.74) days, P>0.05] . As time went the AOFAS score in both group significantly increased (P<0.05) , nev? ertheless no significant differences in AOFAS score were noticed between the two groups at 6, 12 months and the latest follow up (P>0.05) . In addition, there were no statistical differences in ankle ROMs between them at the latest follow up (P>0.05) . Re? garding to radiographic assessment, improper reduction was revealed by postoperative radiographs in 5 / 24 of the AP group, whereas 2/25 of the PA group, despite of no a statistical difference between the two group in fracture healing time (P>0.05) . [Conclusion] Both AP and PA lag screw placements are efficient technique for fixation of posterior malleolar fractures, however, the former might be inferior to latter in fracture reduction and fixation.