Development of a Finite Element Model of the Achilles Tendon: Evaluating Local Displacement Estimation
R.D. Beinema (TU Delft - Mechanical Engineering)
Eline van der Kruk (TU Delft - Biomechatronics & Human-Machine Control)
Nazlı Tümer (TU Delft - Biomaterials & Tissue Biomechanics)
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Abstract
Achilles tendinopathy (AT) is a common Achilles tendon injury, yet its exact cause and the factors influencing progression of individuals remain unclear. Strain distribution is indicated to play a significant role in the progression, possibly linked to the twist of the subtendons. Pizzolato et al. (2020) proposed an integrated framework for studying Achilles tendon mechanics, including a finite element (FE) model estimating local displacements in the Achilles tendon. However, before im- plementing this in AT research, further testing and validation is necessary. Therefore, to make a start for future improvements, this study aims to build a foundational FE model of the Achilles tendon, verify it with in vivo local displacement data and assess the sensitivity to subtendon twist. 3D ultrasound and X-rays of the ankle provided the geometry and the moment arm of the Achilles tendon, respectively. By minimizing the error between the tendon’s elongation during contraction and the FE model prediction, the material properties were optimized. Local displacements in the sagittal and coronal plane were computed using estimated forces from in vivo studies. Simulated subtendon twists (11◦, 37◦, 65◦) examined the effect of the amount of twist on the displacement. Comparing the FE estimated local displacements to in vivo data indicated that additional substructure details are needed to accurately calculate the displacement behavior. Modifying fiber twist angles altered the uniformity of the displacements in the FE model. Therefore, further development of the FE model of the Achilles tendon is recommended before incorporating it into an Achilles tendon mechanics study.