Plantar flexion with inversion shows highest elastic modulus of calcaneofibular ligament using ultrasound share wave elastography.

Purpose: The functional role of the calcaneofibular ligament (CFL) is still controversial. We aimed to investigate the anatomical features of the CFL on sonography and the elastic modulus of the CFL in different ankle positions using ultrasound shear-wave elastography (SWE).

Methods: In 14 cadaveric ankles, the angle of the CFL with respect to the long axis of the fibula was measured in the following ankle positions: neutral (N), 30° plantar flexion (PF), and 20° dorsiflexion (DF). In addition, in 24 ankles of healthy adult volunteers, the elastic modulus of the CFL was evaluated with ultrasound SWE in the following ankle positions: neutral (N), 30° plantar flexion with inversion (PI), 30° plantar flexion with eversion (PE), 20° dorsiflexion with inversion (DI), and 20° dorsiflexion with eversion (DE).

Results: The mean angle of the CFL in N, PF, and DF positions was 139.9° ± 12.7°, 121.3° ± 14.1°, and 158.6° ± 13.1°, respectively. The angle of the CFL in N was significantly greater than that in PF and smaller than that in DF (P < 0.0001, both). The mean elastic modulus of the CFL in the N, PI, PE, DI, and DE positions was: 63.6 ± 50.8, 148.0 ± 39.4, 75.8 ± 40.6, 88.1 ± 31.6, and 61.7 ± 29.4 kPa, respectively. The elastic modulus in PI was significantly higher than in other positions, while the values obtained in DI and DE were also significantly different (P < 0.001, both).

Conclusions: The angle of the CFL increased with DF. Moreover, ultrasound SWE showed that the CFL was tensed and likely to be injured in the PI position.