Shear Wave Tensiometry in the Evaluation of Achilles Tendon Loading: A Cross-Sectional Study on Conservatively Treated Tendons After Rupture.

PURPOSE: The aim of this study was to quantify differences in the shear wave speed (SWS) between a conservatively treated Achilles tendon (AT) after rupture and the unaffected contralateral tendon.

METHODS

Twenty-nine participants who received conservative treatment following Achilles tendon rupture (ATR) were enrolled. Measurements were taken during a single follow-up visit, which occurred between 1 and 7 years after the rupture. Tendon load was assessed using a shear wave tensiometer comprising a set of four accelerometers attached to the tendon. Stiffness, thickness, and cross-sectional area (CSA) were also assessed using MyotonPRO and ultrasound imaging.

RESULTS

No significant differences in SWS were found between the affected AT and the unaffected side when analyzing the entire group (p > 0.05). However, significant differences between sides were observed at 3.5 Nm and 7 Nm (p = 0.001 and p = 0.020) for participants that experienced a lesion of the mid tendon. Higher plantar flexor strength was found for the unaffected side (320 ± 99.5 Nm) compared to the affected side (261 ± 80 Nm; p = 0.001). Thickness and CSA in the proximal and distal part of the tendon were significantly higher in the affected tendon compared to the unaffected side (p < 0.001).

CONCLUSION

There is no difference in SWS values between the affected and the unaffected AT in the longer term after the rupture. However, differences in SWS were detected at specific contraction levels in participants with a mid-tendon lesion. Moreover, tendon thickness and the cross-sectional area, as well as plantar flexor strength, remain different between the affected and the unaffected AT.