Objectives: Injury to the tibiofibular syndesmosis is a common complication of ankle fractures. Currently, it is challenging to determine the stability of the tibiofibular joint caused by ankle fractures during surgery. This study aims to establish a standardized method for dynamically evaluating the stability of the inferior tibiofibular joint under intraoperative ultrasound and assess its utility in surgery, thereby assisting in determining the necessity for fixation of the inferior tibiofibular joint after fracture reduction and fixation. Methods: The stability of the inferior tibiofibular joint was assessed using an intraoperative ultrasonic external rotation stress test, with a torque set at 7.2 N.m. The measured parameters included the width of the inferior tibiofibular space in neutral (N) and external rotation (E) positions, stretch ratio (E/N), and injured/healthy side stretch ratio (I/H). Patients with Weber B or C type ankle fractures were selected as participants. Results: For the case with Weber C fracture, the N measurement was 4.22 mm after fracture fixation, while E measured 5.77 mm and E/N ratio was 1.37, which were larger than those on the healthy side (N: 4.17, E: 4.50, E/N:1.08), with an I/H ratio of 1.27. Intraoperative X-ray revealed instability of the inferior tibiofibular joint. After inserting a tibiofibular screw, the N measurement was 4.20 mm, while the E measurement recorded 4.32 mm, resulting in an E/N ratio of 1.03 and an I/H ratio of 0.95, indicating improved joint stability. For the Weber B fracture case, the N measurement was 3.55 mm after fracture fixation, while E measured 3.98 mm and the E/N ratio was 1.12, slightly lower than those on the healthy side (N: 3.94, E: 4.47, E/N: 1.13), with an I/H ratio of 0.99. The intraoperative X-ray revealed stability of the inferior tibiofibular joint. Therefore, no further fixation was performed on it. Conclusion: Standardized intraoperative ultrasound stress test allows for real-time, dynamic assessment of the stability of the inferior tibiofibular joint after ankle fracture reduction and fixation, which can help guide the fixation of the inferior tibiofibular joint, thereby reducing the risk of postoperative traumatic arthritis.
