Ultrasonographic Assessment Of Achilles Tendon Properties During A One-leg Jump

Abstract

The prevalence of Achilles tendinopathy increases with age and is accompanied by altered tendon properties resulting in a mechanically weaker tendon. Age-related changes in tendon properties could also be shown, as children demonstrate more compliant tendinous structure compared to asymptomatic adults. However, studies investigating Achilles tendon (AT) properties are restricted to in-vitro and isometric conditions, limiting understanding of the tendon response during functional task. PURPOSE: To investigate AT compliance during one-leg jump with respect to age and pathology. METHODS: Ten children (C), ten asymptomatic adults (A) and ten tendinopathic patients (T) were included in the study. Ultrasound imaging was used to assess AT length (ATL), cross-sectional area (CSA) and thickness during rest. AT elongation from rest to maximal jump peak during a one-leg jump on a force plate was sonographically assessed. Force was defined as the maximum value 100ms before flight phase (<30N). AT compliance was calculated by dividing tendon elongation by force. Regarding age, results were compared between C and A. Concerning pathology; results were compared between A and T. One-way ANOVA followed by Bonferroni post-hoc correction tests(α=0.05) were used. RESULTS: AT thickness (C=4.6±0.9 mm, A=4.9±0.5 mm, T=6.9±1.4 mm, p=0.001) and CSA (C=59±18 mm2, A=58±13 mm2, T=83±24 mm2, p=0.021) were statistically significant thicker in T than A and C. AT elongation (C=27±3 mm, A=21±4 mm, T=25±5 mm, p=0.004) and AT compliance [mm/N]) (C=0.026±0.006 mm/N, A=0.017±0.005 mm/N, T=0.019±0.004 mm/N, p=0.001) were found to be statistically significant higher in C compared to A. In contrast, no statistically significant difference between groups were found for ATL (C=219±17 mm, A=217±24 mm, T= 220±24 mm, p≥0.05) and force (C=1068±208 N, A=1287±225 N, T=1389±288 N, p≥0.05). CONCLUSION: During one-leg jumps, tendon responds differently in regards to age, with children having the most compliant AT. The higher compliancy found might be considered as a protective factor against load-related injuries in healthy tendons, as prevalence of Achilles tendinopathy is low in children. Moreover, despite a tendency of altered AT response in tendinopathic patients no significant differences were found compared to asymptomatic adults.