Ultrastructure of tendon rupture depends on strain rate and tendon type

Abstract

Previous research has shown that both the mechanics and elongation mechanisms of tendon and ligament vary with strain rate during tensile loading. In this study, we sought to determine if the ultrastructural damage created during tendon rupture also varies with strain rate. A bovine forelimb model was used, allowing two anatomically proximate but physiologically distinct tendons to be studies: the positional common digital extensor tendon, and the energy storing superficial digital flexor tendon. Samples from the two tendon types were ruptured at rates of either 1%/s or 10%/s. Relative to unruptured control samples, changes to collagen fibril structure were assessed using scanning electron microscopy (SEM), and changes to collagen molecule packing were studied using differential scanning calorimetry (DSC). Rupture at 1%/s caused discrete plasticity damage that extended along the length of collagen fibrils in both the extensor and flexor tendons. Consistent with this, DSC showed molecular packing disruption relative to control samples. Both SEM and DSC showed that extensor tendon fibrils sustained more severe damage than the more highly crosslinked flexor tendon fibrils. Increasing strain rate during rupture decreased the level of longitudinal disruption experienced by the collagen fibrils of both tendon types. Disruption to D-banding was no longer seen in the extensor tendon fibrils, and discrete plasticity damage was completely eliminated in the flexor tendon fibrils, indicating a transition to localized point failure. Ultrastructural damage resulting from tendon rupture depends on both strain rate and tendon type. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Travelling through the Natural Hierarchies of Type I Collagen with X-rays: From Tendons of Cattle, Horses, Sheep and Pigs

“…Very different values were registered compared to those found in literature, due to the different preconditioning and strain rates applied in this study from other literature [ 31 ]. Tendons had a viscoelastic behavior for which a strong test parameter dependence exists: an increase in the stress and strain at failure was registered with a strain rate increase [ 32 , 33 ]. Moreover, it should be mentioned that tendon properties are strongly dependent not only on animal type but also on age, sex, site, feeding, living condition and general health status.…”

Advanced glycation end-product cross-linking inhibits biomechanical plasticity and characteristic failure morphology of native tendon

“…Prior studies have shown that the mechanical response of collagen fibrils in tendon to overload depends on both the enzymatic cross-link profile and the loading rate. While the collagen fibrils of tendons that contain less hydrothermally stable enzymatic cross-linking readily undergo discrete plasticity in response to overload (20,27,39), those with more hydrothermally stable cross-linking only undergo discrete plasticity when overloaded at slow loading rates (10). The impact that AGE cross-linking may have on the overload response of tendons with significant levels of trivalent cross-linking, typically seen in high stress tendons such as the human patellar (12) or Achilles (19), remains to be determined.…”

Optical Microscopy and Electron Microscopy for the Morphological Evaluation of Tendons: A Mini Review

“…For SEM, specimens are commonly sputter coated with gold palladium before imaging. For TEM, ultrathin sectioning, staining or contrasting are applied after embedment.…”

“…After preconditioning, the loss of cohesion, integrity, and parallelism of the collagen fibrils was observed in the SEM images with a significant decrease in CIP scores. At higher magnification, Chambers et al . investigated the morphological change after tendon rupture, and the SEM images showed longitudinally distributed discrete kink‐type sites of plastic deformation and frequent loss of D‐banding in the extensor tendons, while the flexor tendons exhibited less damage.…”