Position dependent elasticity of the anterior talofibular ligament in healthy young women: an in-vivo shear wave elastography study.

PURPOSE: The anterior talofibular ligament (ATFL) is the primary restraint to ankle inversion, yet quantitative in vivo data on its elastic behavior across functional positions are limited. Shear wave elastography (SWE) provides noninvasive estimates of local elastic parameters (surrogate indices of material stiffness rather than direct measures of structural stiffness). We aimed to characterize ATFL SWE-derived parameters in baseline position and examiner-assisted passive maximal-inversion position.

METHODS

In this cross-sectional study, 50 healthy adult female volunteers (aged 20-39) underwent SWE of the dominant-side ATFL using a high-frequency linear transducer in musculoskeletal mode. Three 1 mm diameter circular regions of interest (proximal, middle, and distal) were assessed in both positions, and ATFL length was measured in each posture. Posture-dependent differences were tested with paired t-tests or Wilcoxon tests as appropriate. Associations between Shear wave velocity (SWV) and demographic variables were explored using Spearman's correlation.

RESULTS

SWV increased significantly from the baseline to examiner-assisted passive maximal-inversion position at all sites (all P < 0.001), rising from 3.21 to 3.45 m/s to 4.04-4.68 m/s. ATFL length increased modestly from 17.0 ± 1.5 mm to 17.4 ± 1.5 mm (P < 0.017). No significant correlations were observed between SWV and age, height, body mass, BMI, or foot length (all P > 0.0017).

CONCLUSIONS

In healthy young women, ATFL SWE-derived elastic parameters increase in an examiner-assisted passive maximal-inversion position, consistent with greater mechanical engagement. These posture-specific reference values support future studies in ankle sprain and chronic ankle instability.