title: The interfascicular matrix enables fascicle sliding and recovery in tendon, and behaves more elastically in energy storing tendons.
abstract: While the predominant function of all tendons is to transfer force from muscle to bone and position the limbs, some tendons additionally function as energy stores, reducing the cost of locomotion. Energy storing tendons experience extremely high strains and need to be able to recoil efficiently for maximum energy storage and return. In the equine forelimb, the energy storing superficial digital flexor tendon (SDFT) has much higher failure strains than the positional common digital extensor tendon (CDET). However, we have previously shown that this is not due to differences in the properties of the SDFT and CDET fascicles (the largest tendon subunits). Instead, there is a greater capacity for interfascicular sliding in the SDFT which facilitates the greater extensions in this particular tendon (Thorpe et al., 2012). In the current study, we exposed fascicles and interfascicular matrix (IFM) from the SDFT and CDET to cyclic loading followed by a test to failure. The results show that IFM mechanical behaviour is not a result of irreversible deformation, but the IFM is able to withstand cyclic loading, and is more elastic in the SDFT than in the CDET. We also assessed the effect of ageing on IFM properties, demonstrating that the IFM is less able to resist repetitive loading as it ages, becoming stiffer with increasing age in the SDFT. These results provide further indications that the IFM is important for efficient function in energy storing tendons, and age-related alterations to the IFM may compromise function and predispose older tendons to injury.
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS UK. Electronic address: c.thorpe@qmul.ac.uk.
authors.forename: Chavaunne T
authors.initials: CT
authors.lastname: Thorpe
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS UK.
authors.forename: Marta S C
authors.initials: MSC
authors.lastname: Godinho
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Riley
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore HA7 4LP, UK.
authors.forename: Helen L
authors.initials: HL
authors.lastname: Birch
authors.affiliation: Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst Campus, Neston CH64 7TE, UK.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Clegg
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS UK.
authors.forename: Hazel R C
authors.initials: HRC
authors.lastname: Screen
mesh_terms: D000375:Aging; D000818:Animals; D004548:Elasticity; D004734:Energy Metabolism; D005552:Forelimb; D006736:Horses; D008422:Materials Testing; D013710:Tendons / Q000378:metabolism*
keywords: Endotenon; Fascicle; Fatigue; Mechanics; Structure-function; Viscoelastic