Biplanar ultrasound investigation of in vivo Achilles tendon displacement non-uniformity

Abstract

The Achilles tendon is a common tendon for the medial and lateral gastrocnemius and soleus muscles. Non‐uniform Achilles tendon regional displacements have been observed in vivo which may result from non‐uniform muscle loading and intratendinous shearing. However, prior observations are limited to the sagittal plane. This study investigated Achilles tendon tissue displacement patterns during isometric plantarflexor contractions in the coronal and sagittal planes. Fourteen subjects (5 female, 9 male, 26 ± 3 year) performed maximal isometric plantarflexor contractions with the knee in full extension and flexed to 110°. An ultrasound transducer positioned over the free Achilles tendon collected beam formed radio frequency (RF) data at 70 frames/s. Localized tissue displacements were analyzed using a speckle tracking algorithm. We observed non‐uniform Achilles tendon tissue displacements in both imaging planes. Knee joint posture had no significant effect on tissue displacement patterns in either imaging plane. The non‐uniform Achilles tendon tissue displacements during loading may arise from the anatomical organization of the sub‐tendons associated with the three heads of the triceps surae. The biplanar investigation suggests that greatest displacements are localized to tissue likely to belong to soleus subtendon. This study adds novel information with possible implications for muscle coordination, function, and muscle‐tendon injury mechanisms.

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

“…Non-uniform displacement within the Achilles tendon has been widely demonstrated under various static ( Arndt et al, 2012 ; Bogaerts et al, 2017 ; Stenroth et al, 2019 ) and dynamic ( Chernak Slane and Thelen, 2014 ; Franz et al, 2015 ; Franz and Thelen, 2015 ; Slane and Thelen, 2015 ) loading conditions. This non-uniformity decreases as people age ( Clark and Franz, 2020 ; Franz and Thelen, 2015 ; Slane and Thelen, 2015 ) and after repair of a ruptured tendon ( Beyer et al, 2018 ; Fröberg et al, 2017 ).…”

Non‐uniform displacement within ruptured Achilles tendon during isometric contraction

“…The fascicles originating from different TS muscles exert differential forces and strains on each sub‐tendon 12,14 and are likely to cause non‐uniformities between fascicles arising from different muscle heads 12,14 . In several studies, the anterior (deep) tendon has been reported to displace more than the posterior (superficial) tendon 15‐18 . Furthermore, the different degrees of torsion among the population would lead to distinct non‐uniform displacement patterns within the AT for each group.…”

An equine tendon model for studying intra-tendinous shear in tendons that have more than one muscle contribution

“…Individual control of sub-tendons creates non-uniform displacements within the Achilles tendon, and this non-uniformity has been observed in both passive [21-23] and dynamic [16, 24] movements. Furthermore, this displacement non-uniformity between the sub-tendons shows an age-related and disease-related decline [17, 25, 26].…”