Ideal Suture Tape Anchor Placement for Anteroinferior Tibiofibular Ligament Augmentation in Isolated Syndesmotic Injury Using Hounsfield Units.

BACKGROUND: Augmentation of the anterior inferior tibiofibular ligament with a sutured tape anchor is commonly performed in surgery for isolated syndesmotic injury. The anchor insertion site is presumed to have good bone quality, as indicated by Hounsfield unit values. However, the Hounsfield unit values at the anterior inferior tibiofibular ligament attachment sites have not been established. PURPOSE: This study aimed to measure the Hounsfield unit values at the superior, middle, and inferior fascicle attachments of the anterior inferior tibiofibular ligament and to identify the optimal anchor insertion site. STUDY DESIGN: Cross-sectional study. METHODS: This study included patients who underwent preoperative computed tomography at our institution between December 2019 and February 2026. After excluding patients with ankle fractures or deformities, 28 patients were enrolled. Three-dimensional computed tomography reconstructions were used to annotate the tibial and fibular attachments of the three anterior inferior tibiofibular ligament fascicles. Hounsfield unit values were measured on axial, coronal, or sagittal images corresponding to these annotations. Comparisons were performed using repeated-measures analysis of variance with Bonferroni correction. RESULTS: The tibial Hounsfield unit values for the superior, middle, and inferior fascicles were 359.5, 430.5, and 509.1, respectively, with the inferior fascicle demonstrating significantly higher values (p < 0.001). On the fibular side, the values were 496.2, 460.7, and 527.7, with a significant difference observed between the middle and inferior fascicles (p = 0.013). CONCLUSION: For isolated syndesmotic injury, the optimal anchor insertion site for anterior inferior tibiofibular ligament augmentation appears to be the attachment of the inferior fascicle. LEVEL OF CLINICAL EVIDENCE: 4.