The Assessment of Reduction Status Using Radiographic Parameters and Ideal Trans-Fixation Technique for Unstable Syndesmotic Injury with Ankle Fracture

Category: Ankle, Trauma Introduction/Purpose: Anatomical restoration of distal tibiofibular syndesmosis is essential in ankle fractures with syndesmotic injury. However, intraoperative reference line of penetrating angle and evaluation of reduction status remains without consensus. The purpose of this study is to analyze the reduction status of syndesmotic injury using radiographic parameters and to find ideal fixation angle treated with trans-fixation in unstable syndesmotic injury. Methods: Twenty-six patients with ankle fractures with syndesmotic injury that underwent preoperative and postoperative bilateral computed tomography (CT) scans were enrolled. A multi-center study was performed in two tertiary medical centers. All patients were treated with tibiofibular trans-fixation screw or tight rope® fixation. The axial sections of bilateral CT scans were reviewed to measure Fibular Diastasis (FD) and Surface Area of Syndesmosis (SAS) at the level of 1.0 cm above ankle joint. Reduction status was measured by calculating the ratio of postoperative and intact side using radiologic parameters. The trans-fixation angles between the perpendicular line of incisura and distal trans-fixation material was measured. Patients were classified by trans-fixation angle into three groups, as showing 0 -1 degree (A), 1-5 degree (B), 5 or more degree (C) in absolute value. Results: The mean value of reduction status ratio was 1.13 in FD and 1.27 in SAS. The absolute mean value of trans-fixation angle was 4.11°. Trans-fixation angle and reduction status had positive correlation in FD (R = 0.522, p = 0.006) and SAS ratio (R = 0.695, p = 0.000). The absolute mean value of trans-fixation angle in group A, B, C was 0.56° (7 cases), 3.01° (12 cases), and 8.90° (7 cases). The mean value of FD ratio in group A, B, C was 1.01, 1.03 and 1.41. FD and SAS ratio had no difference between group A and B but had significant difference between group A, B and C (p < 0.05). Conclusion: Inappropriate trans-fixation technique had correlated with the loss of reduction after treatment of unstable ankle fracture associated with syndesmotic injury. An angle of 5° from the perpendicular line of the incisura is considered as the ideal trans-fixation angle to maintain the reduction status.