Biomechanical evaluation of the anterior talo-fibular and calcaneo-fibular ligaments using shear wave elastography in young healthy adults.

BACKGROUND: The objective of this study was to evaluate the stiffness of the anterior talo-fibular ligament (ATFL) and calcaneo-fibular ligament (CFL) using shear wave elastography (SWE) with the ankle in the neutral position and in varus, in young healthy adult volunteers. We also evaluated the reliability and reproducibility of the SWE measurements. HYPOTHESIS: The stiffness of both ligaments increases with increasing ankle varus. SWE may be a reliable tool for evaluating the lateral collateral ligament complex of the ankle. MATERIAL AND METHODS: We used SWE to evaluate both ankles of each of 20 healthy volunteers (10 females and 10 males). For each test, the foot was placed on a hinged plate and tested in the neutral position and in 15° and 30° of varus. Stiffness was evaluated based on shear wave velocity (SWV). RESULTS: Stiffness of both the ATFL and CFL was minimal in the neutral position (2.06m/s and 3.43m/s, respectively). Stiffness increased significantly for both ligaments in 15° of varus (2.48m/s and 4.11m/s, respectively; p<0.0001) and was greatest in 30° of varus (3.15m/s and 4.57m/s, respectively; p<0.0001). ATFL stiffness was greater in males than in females in 15° (p=0.04) and 30° (p=0.02) of varus. For the CFL, in contrast, stiffness was not different between males and females. Stiffness of the ATFL and CFL was not associated with age, dominant side, height, or foot morphology. No correlations were found between stiffness of the two ligaments in any of the positions. Repeating each measurement three times produced excellent concordance for both ligaments in all three positions. CONCLUSION: The ATFL and CFL are the main lateral stabilisers of the ankle, and each exerts a specific function. Their stiffness increases with the degree of varus. This study describes a protocol for evaluating ATFL and CFL density by SWE, which is a reliable and reproducible technique that provides a normal range. LEVEL OF EVIDENCE: IV.