Sonoelastography of the distal third of the Achilles tendon in asymptomatic volunteers: correlation with anthropometric data, ultrasound findings and reproducibility of the method

Evaluating prospectively elastosonographyc (EUS) findings of distal third of Achilles tendon in asymptomatic volunteers and correlating with subject characteristics and ultrasound (US) findings and, subsequently, calculating reproducibility of method.

70 consecutives Achilles tendons were examined with US and EUS in 35 asymptomatic volunteers. Mean age 42.3 years (±7.6), 22 were female (mean age 41 ± 8.7) and 13 were male (mean age 42.5 ± 11.4). Information about population was collected (anthropometric data, sport activity, taken therapy and associated conditions/pathologies).

Statistically significant correlation was found between BMI and EUS findings (p = 0.007) and between EUS aspect and US diagnosis (p = 0.039) both to the right tendon. Possible influence of smoking (p = 0.063 to right) and associated conditions (p = 0. 059 to left), has been found. The multivariate analysis showed that EUS results are correlated only with BMI (high BMI corresponds to the best EUS results), independently from smoke and associated conditions on right side. No correlations have emerged for the left tendon. The 22.8 % of the volunteers took on chronic therapies, none statistically significant correlation. In the past, 80 % of subjects played sports (7.4 % agonistic and 92.6 % non-agonistic). The 22.9 % of volunteers played sporadic or no activity. The 60 % of volunteers has played sports that may lead overload of the Achilles tendon. The 61.5 % of subjects with BMI ≥ 25 was active little or nothing; 63.6 % of the subjects with BMI < 25 is playing sports. US examination showed 57.1 % normal tendons and 42.9 % tendinosic. Rate of tendinosic tendons was similar in both left and right (40 and 45.7 %, respectively). Statistically significant correlation was found between EUS aspect and US diagnosis on the right tendon but not on the left Correlation between thickness and EUS aspect was calculated: no correlation was found. Interoperator correlation was excellent (k = 0.89 for left tendon and k = 0.91 for right tendon).

The EUS is an interesting and useful technique, characterised by a high reproducibility. Its results are related to BMI and US appearance of the tendon, and they are probably influenced by the smoke and associated conditions. However, the flexed ankle position, needed to properly examine the distal third by US, alters the elasticity of the tendon and causes false negative results to EUS. Then, for the EUS study of the distal third, it would be appropriate the relaxed position, with a gel pad to optimise the probe adhesion.