Gaining Insight into the Deformation of Achilles Tendon Entheses in Mice

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.

Full-field strain distribution in hierarchical electrospun nanofibrous Poly-L(lactic) acid and Collagen based scaffolds for tendon and ligament tissue regeneration: a multiscale study

“…Conversely, the EHS membrane had lower number of nanofibers in the range of 0°−12° (6.8% ± 1.2% of the total) compared with the ones in the range of 81°−90° (16.1% ± 1.24% of the total). This analysis confirmed the morphological biomimicry of the bundles with the T/L fascicles and of the membranes with the epitenon/epiligament [2,43,44]. were aligned with the axis of the scaffold, while an angle of 90° means that the nanofibers were perpendicular to the scaffold.…”

“…8D) in correspondence of their maximum sliding (εDmax = 10.75±1.30%). The DVC full-field strain distribution of SB and EHS produced a strain behavior similar to that experienced in the natural T/L tissue counterpart by using DVC [43], DIC [26,28,57,58] and finite element models [59]. The progressive stretching and reorganization of internal collagen fibrils/fascicles of T/L during physiological activities is responsible for the nonlinear behavior of their stress/strain curves.…”

Full-field strain distribution in hierarchical electrospun nanofibrous poly-L(lactic) acid/collagen scaffolds for tendon and ligament regeneration: A multiscale study

“…The lower levels of failure strain for EHS were due to the folding procedure to obtain them. These failure strains were higher than those of natural fascicles and T/L [ 3 , 43 ], but can provide a safety factor in case of partial damage of scaffolds, with a relevant work absorption ( Fig. 3 P), preventing a premature implant failure.…”

“…Focusing on the T/L tissue instead, due to the high resolution and contrast required, microCT studies were performed mostly in static conditions by dehydrating samples, using contrast agents, or eventually performing phase-contrast synchrotron x-ray images [ [37] , [38] , [39] , [40] , [41] , [42] ]. To the authors’ knowledge, only one study has been carried out so far using DVC to study strain distributions in the rat enthesis [ 43 ]. Conversely, DVC analyses on electrospun materials and scaffolds are completely unexplored so far, due to the concomitant need of high resolution and the low x-ray absorption of polymeric fibrous materials.…”

Digital Volume Correlation for large deformations of soft tissues: Pipeline and proof of concept for the application to breast ex vivo deformations

“…Recently, DVC was applied to study the spine [27,28]. Several works used DVC to map strain fields for arteries [29], tendons [30], intervertebral disks [31,32], tissue interfaces with prosthetics [33] or even the mitral valve [34]. Optical coherence elastography/tomography techniques (e.g., for the identification of elastic properties) based on DVC with 3D infinitesimal strain measurements were performed ex vivo on mesoscopic (i.e., millimetric regions of interest) human [35] and chicken [36] breast tissues.…”