Individual variation in Achilles tendon morphology and geometry changes susceptibility to injury

• Published in: eLife Vol. 10
• Main Authors: Yin, Nai-Hao, Fromme, Paul, McCarthy, Ian, Birch, Helen L
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 16.02.2021; eLife Sciences Publications, Ltd
• Subjects: Achilles tendon; Achilles Tendon - anatomy & histology; Achilles Tendon - diagnostic imaging; Achilles Tendon - physiology; Adult; Age; Age Factors; Aged; Aged, 80 and over; Biomechanical Phenomena; Computational and Systems Biology; Computer Simulation; Female; Geometry; Human mechanics; Humans; Injuries; injury; Interfaces; Male; Mechanical properties; mechanical property; Medicine; Middle Aged; Morphology; Movement; Muscles; Rehabilitation; Tendons; Ultrasonic imaging; Ultrasonography; computational biology; systems biology; Achilles tendon; mechanical property; medicine; injury; human
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.63204

The unique structure of the Achilles tendon, combining three smaller sub-tendons, enhances movement efficiency by allowing individual control from connected muscles. This requires compliant interfaces between sub-tendons, but compliance decreases with age and may account for increased injury frequency. Current understanding of sub-tendon sliding and its role in the whole Achilles tendon function is limited. Here we show changing the degree of sliding greatly affects the tendon mechanical behaviour. Our in vitro testing discovered distinct sub-tendon mechanical properties in keeping with their mechanical demands. In silico study based on measured properties, subject-specific tendon geometry, and modified sliding capacity demonstrated age-related displacement reduction similar to our in vivo ultrasonography measurements. Peak stress magnitude and distribution within the whole Achilles tendon are affected by individual tendon geometries, the sliding capacity between sub-tendons, and different muscle loading conditions. These results suggest clinical possibilities to identify patients at risk and design personalised rehabilitation protocols.