Safety of Anchor Placement in Anterior Talofibular Ligament Repair: A Virtual Three-Dimensional Bone Model Study in Adults

Objective To analyze the optimal position, safe angle, risk of fibular fossa penetration, and effective intraosseous fixation length for fibular-sided anchor placement during anterior talofibular ligament (ATFL) repair using virtual three-dimensional (3D) bone models. Methods We retrospectively enrolled 100 adults (59 males, 41 females) who underwent ankle CT and generated virtual 3D bone reconstructions. The ATFL fibular footprint center was defined as the anchor insertion point. A simulated 3.0 mm-diameter tunnel measured: (1) vertical distance from the insertion point to the fibular tip horizontal plane (h), (2) maximum angle (θ) in the sagittal plane avoiding fibular fossa penetration, and (3) effective tunnel length at 60°, 45°, and 30° parallel to the fibular sagittal plane and along the lateral malleolar ridge. Results Mean h was 5.36 ± 1.29 mm, and mean θ was 67.48 ± 8.05°. Effective tunnel lengths increased as insertion angle decreased. In the sagittal plane, effective lengths at 60°, 45°, and 30° were 17.99 ± 3.67, 22.09 ± 2.32, and 26.74 ± 2.75 mm, respectively; values along the lateral malleolar ridge were 17.58 ± 2.01, 19.62 ± 2.20, and 23.96 ± 2.84 mm. Fibular fossa penetration (11.0%) occurred only during 60° insertion parallel to the sagittal plane. Males exhibited significantly greater h values and effective tunnel lengths than females (P < 0.001); θ did not differ between sexes (P = 0.632). Conclusion The optimal fibular-sided anchor insertion point is located approximately 5.4 mm proximal to the fibular tip. Insertion parallel to the fibular sagittal plane at 30°–45° balances safety and intraosseous fixation length. When a larger insertion angle is necessitated, insertion along the lateral malleolar ridge direction may be a safer alternative. Anchor length selection should account for sex differences, with lengths not exceeding 20 mm for males and 18 mm for females.