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Mechanical properties of the equine superficial digital flexor tendon relate to specific collagen cross‐link levels
Author(s) -
THORPE C. T.,
STARK R. J. F.,
GOODSHIP A. E.,
BIRCH H. L.
Publication year - 2010
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.2010.00175.x
Subject(s) - tendon , link (geometry) , cross link , medicine , anatomy , materials science , computer science , composite material , computer network , polymer
Summary Reasons for performing study: Damage to the flexor tendons, particularly the superficial digital flexor tendon (SDFT), is one of the most common musculoskeletal injuries sustained by horses competing in all disciplines. Our previous work has shown that SDFTs from different individuals show a wide variation in mechanical strengths; this is important clinically as it may relate to predisposition to injury. The high mechanical strength of tendon relies on the correct orientation of collagen molecules within fibrils and stabilisation by the formation of chemical cross‐links between collagen molecules. It is not known whether the variation in SDFT mechanical properties between individuals relates to differences in collagen cross‐link levels. Hypothesis: Enzyme‐derived, intermolecular cross‐linking of tendon collagen correlates with mechanical properties of the SDFT. Methods: SDFTs were collected from 38 horses and mechanically tested to failure. Structural and material properties were calculated from the load/deformation plot and cross‐sectional area for each tendon. Following mechanical testing, pyrrolic cross‐link levels were measured using a spectrophotometric assay for Ehrlich's reactivity and pyridinoline levels were quantified by HPLC. Cross‐link levels were correlated with mechanical properties and statistical significance tested using a Pearson's correlation test. Results: Pyrrole cross‐link levels showed a significant positive correlation with ultimate stress (P = 0.004), yield stress (P = 0.003) and elastic modulus (P = 0.018) of the tendons, despite being a minor cross‐link in these tendons. There was no significant correlation of mechanical properties with either hydroxylysyl‐ or lysyl‐pyridinoline levels. Conclusions: Given the low absolute levels of pyrrole, we suggest that the correlation with high mechanical strength is through an indirect mechanism. Understanding the nature of the relationships between pyrrole cross‐links, other matrix characteristics and tendon material properties may allow development of strategies to identify horses at risk from tendon injury and be of value in informing training practices.