The Distal Fascicle of the Anterior Inferior Tibiofibular Ligament (AITFL-df) as a Reliable Landmark for Fibular Tunnel Positioning in Anterior Talofibular Ligament Reconstruction

Background: Lateral ankle sprain commonly leads to chronic lateral ankle instability, often requiring ATFL reconstruction. Accurate fibular tunnel placement is essential but may be challenging when the fibular obscure tubercle (FOT) is unclear. The distal fascicle of the anterior inferior tibiofibular ligament (AITFL-df) may provide a reliable alternative landmark. Methods: In this retrospective radiographic cohort study, we reviewed patients with chronic lateral ankle instability who underwent anatomic ATFL reconstruction between January 2020 and December 2024. Patients were allocated to 2 groups according to the landmark used intraoperatively for fibular tunnel positioning: the AITFL-df–guided group (tunnel centered 7 mm distal to the AITFL-df) and the FOT-guided group (tunnel centered at the FOT). The evaluation metric was the accuracy and consistency of the fibular tunnel position, quantified as the fibular tunnel ratio on postoperative 3-dimensional computed tomography (3D-CT). Subgroup analysis was performed according to FOT visibility on preoperative 3D-CT. Results: A total of 124 patients were included (61 in the AITFL-df–guided group, 63 in the FOT-guided group). The intra- and interobserver reliability for measuring the fibular tunnel ratio was excellent (intraclass correlation coefficients > 0.87). The mean fibular tunnel ratio was comparable between the AITFL-df and FOT groups (0.45 ± 0.05 vs 0.46 ± 0.10, P = .207). However, the AITFL-df group showed significantly lower variance in tunnel position ( P < .001). Subgroup analysis showed similar AITFL-df positioning irrespective of FOT visibility ( P = .902 for variance), whereas FOT-guided positioning varied significantly when the FOT was unclear ( P = .037 for mean, P = .022 for variance). In FOT− cases, AITFL-df–guided positioning was superior in both mean tunnel ratio and variance. Conclusion: The AITFL-df may serve as a reliable anatomical landmark for fibular tunnel positioning in graft-based ATFL reconstruction. Compared with the FOT, it was associated with greater positioning consistency, particularly when the FOT was unclear. Level of Evidence: Level III, retrospective cohort study.