An AFM study of the nanostructural response of New Zealand white rabbit Achilles tendons to cyclic loading

Abstract

The nanostructural response of New Zealand white rabbit Achilles tendons to a fatigue damage model was assessed quantitatively and qualitatively using the endpoint of dose assessments of each tendon from our previous study. The change in mechanical properties was assessed concurrently with nanostructural change in the same non‐viable intact tendon. Atomic force microscopy was used to study the elongation of D‐periodicities, and the changes were compared both within the same fibril bundle and between fibril bundles. D‐periodicities increased due to both increased strain and increasing numbers of fatigue cycles. Although no significant difference in D‐periodicity lengthening was found between fibril bundles, the lengthening of D‐periodicity correlated strongly with the overall tendon mechanical changes. The accurate quantification of fibril elongation in response to macroscopic applied strain assisted in assessing the complex structure–function relationship in Achilles tendons.

Opposite Effect of Cyclic Loading on the Material Properties of Medial Collateral Ligament at Different Temperatures: An Animal Study

“…Cyclic loading can partially uncoil the triple helix structures of collagen molecules and destroy the crosslinks ( Firminger and Edwards, 2021 ; Al Makhzoomi et al, 2022 ). Therefore, cyclic loading can weaken the fibril bearing capacity of tail tendon with low crosslink density.…”

“…Our explanation focused on the fibril level (i.e., crosslinks and collagen molecules) because fibrillar properties govern the mechanical response at the tissue level ( Su et al, 2008 ; Svensson et al, 2012 ; Svensson et al, 2013 ; Firminger and Edwards, 2021 ). Although many studies have tried to find out the load transfer mechanism from fibril behavior to tissue response, no definite conclusions have been drawn ( Redaelli et al, 2003 ; Robinson et al, 2005 ; Haraldsson et al, 2008 ; Fessel and Snedeker, 2009 ; Henninger et al, 2013 ; Al Makhzoomi et al, 2022 ). Therefore, at this stage, we cannot exclude any possible contribution of inter-fibril load transfer components to the mechanical response of ligaments or tendons, which may be found in the future.…”