Gaining Insight into the Deformation of Achilles Tendon Entheses in Mice

Julian Sartori,Sebastian Köhring,Julian Moosmann,Stefan Bruns,Jörg U Hammel

doi:10.1002/adem.202100085

Abstract

Understanding the biomechanics of tendon entheses is fundamental for surgical repair and tissue engineering but also relevant in biomimetics and paleontology. Examinations into the 3D tissue deformation under load are an important element in this process. However, entheses are difficult objects for microcomputed tomography due to extreme differences in X–ray attenuation. Herein, the ex vivo examination of Achilles tendon entheses from mice using a combination of tensile tests and synchrotron radiation‐based microcomputed tomography is reported. Strains and volume changes are compared between the more proximal free tendon and the distal tendon that wraps around the Tuber calcanei. Tomographic datasets of relaxed and deformed entheses are recorded with propagation‐based phase contrast. The tissue structure is rendered in sufficient detail to enable manual tracking of patterns along the tendon, as well as digital volume correlation in a suitable pair of tomographic datasets. The strains are higher in the distal than in the proximal tendon. These results support the existence of a compliant zone near the insertion. Necessary steps to extend the automatic tracking of tissue displacements to all stages of the deformation experiment are discussed.

Highlights

Tomographic datasets of relaxed and deformed entheses are recorded with propagation-based phase contrast
The tissue structure is rendered in sufficient detail to enable manual tracking of patterns along the tendon, as well as digital volume correlation in a suitable pair of tomographic datasets
Results from digital volume correlation (DVC) and visual analysis were compared in one unwatered specimen with regard to the linear strain along the measuring distance used in the visual analysis

Summary

Introduction

Whereas tendons and ligaments transfer tensile loads.[2] These load cases merge at insertions of tendons and ligaments into bone, called entheses. Insertions to the tensile tests and synchrotron radiation-based microcomputed tomography is ends of long bones usually share a characreported. Tomographic datasets of relaxed and deformed entheses are recorded with propagation-based phase contrast. The tissue structure is rendered in sufficient detail to enable manual tracking of patterns along the tendon, as well as digital volume correlation in a suitable pair of tomographic datasets. Higher in the distal than in the proximal tendon. These results support the existence of a compliant zone near the insertion. There is a long record of examinations into the tensile behavior of tendons and ligaments.

Results

Discussion

Conclusion