Objective：To explore the mechanism of posterior pilon fracture with different proportion of the medial malleolus involved and evaluate clinical outcomes of anterior-posterior screws fixation.
Methods: Patients admitted to our hospital with diagnosis of tibial posterior Pilon fracture were identified from January 2014 to January 2018. Mechanism from medical history, proportion of the medial malleolus involved (not involved/partial involved /total involved) from axial CT sacn were recorded to figure out the mechanism . Burwell—Charnley radiographic criteria of reduction, American orthopaedic Foot＆Ankle society ankle-hindfoot scale at 12 month follow-up were recorded to evaluate the curative effect of anterior-posterior screws fixation.
Result: Sixty-nine patients were identified in this retrospective study. 43 males and 26 females were included, with mean age 46.9 years old（range, 21-76 years）. Mechanism of the 8 cases with fracture line do not involve midial malleolus but accompanied with die-punch fragment included 4 ground level fall, 2 fall off stairs, 1 sport injury, 1 fall from bike. Mechanism of the 52 cases with midial malleolus partial involved included 14 motor vehicle accident, 14 fall off stairs, 5 sport injury, 3 fall from bike and 16 fall from height. Mechanism of the 9 cases with medial malleolus totally involved included 6 falling from height, 2 falling of stairs and 1 motor vehicle accident. Five patients were treated with the fixation of Anterior-Posterior screws, fracture line of four cases do not involve midial malleolus and the rest one partial involved. The Burwell—Charnley radiographic criteria of reduction were fair in 4 and poor in one on the post-operation X-ray. Three of them got implant failure. The AOFAS ankle-hindfoot scale 12-month post-operation for the rest two patients were 78 and 72.
Conclusion: There is a high risk of implant failure using A-P screws for the treatment of posterior pilon fracture. The mechanism of posterior fracture involve medial malleolus is mainly vertical force .