Shear wave elastography (SWE) has shown great promise for evaluating the Achilles tendon, though challenges in technique standardization persist due to limited understanding of optimal examination practices. This study aimed to investigate how variables such as ankle positioning, probe frequency, and physical exertion impact Achilles tendon elasticity measurements, as well as assess the intra- and inter-observer reliability of SWE. A total of 37 healthy volunteers participated, with two examiners conducting the SWE assessments. The shear modulus of the Achilles tendon was measured with the ankle in three positions: neutral, maximum dorsiflexion, and maximum plantar flexion, using two different high-frequency probes. After this initial round, participants completed a brief physical exercise, followed by another round of SWE measurements.
The study found that the L18-5 probe positioned 2 cm from the Achilles’ calcaneal insertion, with the ankle in a neutral position, produced the highest intra-class correlation coefficient (ICC) values (ICC = 0.798, 95% CI 0.660–0.880, p < 0.001), suggesting good reliability. In contrast, the lowest reliability was seen with the same probe positioned 1 cm from the insertion during maximum plantar flexion (ICC = 0.422, 95% CI 0.032–0.655, p = 0.019). Differences in elasticity values were observed across ankle positions and probe types, indicating these factors significantly influence the measurement outcomes. However, no substantial elasticity changes were noted after participants performed physical exercise. Based on these results, the study concluded that an ankle position of 10 to 20 degrees in plantar flexion is optimal for SWE assessments of the Achilles tendon. Further studies are needed to develop standardized SWE protocols, especially for precise and reproducible evaluation of Achilles tendon health.
