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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: The Influence of Microstructure on the Mechanical Behaviours of Tendons

Author: TOORANI, Shima

Year: 2010

Supervisor(s): Hazel Screen, Julia Shelton

This study contrasts the functionally opposing, superior digital flexor (SDFT) and common digital extensor (CDET) tendons. Histology and transmission electron microscopy were used to identify significant differences in the crimp morphology and fibril arrangement of the two tendon types, whilst standard assays highlighted differences in GAG and water content. Quasi-static and viscoelastic tests were performed to determine the biomechanical response to various loading regimes and evaluate how these parameters varied between the two different tendons.

This study attempts to correlate the significant differences in mechanical properties of these tendons to compositional and structural differences. The organisation of collagen fibrils largely governs the ability of a tendon to have the appropriate strength and stiffness, allowing it to withstand stresses induced by the attached muscle. It was demonstrated that highly stressed SDFT tendons were made up of more tightly packed collagen fibrils, with greater elastic modulus to better transmit the tensile loads. In contrast, CDET tendons showed more pronounced viscoelastic behaviour, such as greater stress-relaxation response, allowing for more intricate movements. The differences in relaxation response of the two tendons made it difficult to accurately predict their behaviour using mathematical modelling. This suggests that viscoelastic relaxation of tendons is highly complex and cannot easily be captured, both between two different tendons and in the same tendon at different strain rates.

Current approaches in the design of tendon replacement scaffolds focus predominantly upon the mechanical strength and viscoelasticity should be considered in the material design in order to provide a better suited replacement, which better reflects the specific functional requirements of the site.