Objective To evaluate the precision and effectiveness of inferior tibiofibular syndesmosis reduction guided by ana-tomic land marks during open reduction and internal fixation of ankle fracture complicated with lower tibiofibular union injury.Methods A total of 26 cases of ankle fractures with inferior tibiofibular syndesmosis separation treated with open reduction and internal fixation from June 2018 to July 2021 were included.The joint face of inferior tibiofibular sundesmosis was visible at the ankle articular surface during operation,and anatomical reduction of lower tibiofibular union bone anatomical marks(ar-ticular surface of lower tibiofibular union and articular surface of fibular bone)was confirmed and 1 or 2 inferior tibiofibular screws were inserted.The screw was placed in the 3rd cortex and then partially withdrawn outside the 3rd cortex,and the screw was completely placed at the lower tibiofibular union under continuous freehand pressure.The accuracy and effectiveness of the combined lower tibiofibular reduction were evaluated by CT after operation.Results All 26 cases were followed up for 18 to 36 months(mean 26.5 months).Postoperative X-ray showed normal ankle mortise,good alignment of the ankle fracture,and in-ternal fixation in place.Postoperative CT scans of the ankle joint confirmed that the inferior tibiofibular joint was facing well.The healing of fractureof ankle joint was osseous,and the fracture healing time was 3-6 months,with an average of 4.6 months.One year after surgery,the Baird-Jackson score of ankle joint function ranged from 85 to 100,with an average of 94.5 points.Among them,16 cases were excellent,4 cases were good and 1 case was fair.Conclusion Open reduction and internal fixation of ankle fracture is effective and reliable to accurately restore the lower tibiofibular union with reference to the anatomical marks of the articular surface of tibia and the articular surface of fibula.