| dc.description.abstract | Achilles tendinopathy is the most common lower limb tendinopathy, with increasing yearly prevalence. Nonetheless, there remains poor understanding of disease aetiology, and challenges associated with contextualising diagnosis to inform treatment. Imaging highlights that structural changes do not correlate with functional changes. The aim of this thesis is to establish an ultrasound-based imaging method to detect the slip planes, and subsequently to quantify local strain distribution in human free Achilles tendon. A systematic review was conducted to determine state-of-the-art in detecting non uniformity in tendon deformation during functional use and synthesise current best understanding of how non-uniformity varies between individuals, with injury and with ageing. Outcomes identified that no previous studies have looked at slip-planes in tendon, to define sub-tendon boundaries and explore independent loading of each head of triceps surae muscles and resulting tendon deformation behaviour. The thesis subsequently focused on developed a method to address this gap, adapting and optimising an automated algorithm known as slip-elastography (previously developed to investigate slippery boundary of cancerous tissue) to detect and quantifying non-uniform tendon strains and identify slip boundaries. Ultrasound radiofrequency data of the AT was collected while participants performed movement tasks and analysed retrospectively along with electromyography and torque data. Data demonstrated that the deep layer of the AT displaced further than the superficial layer during movement. However, knee position was shown not to influence tendon displacement profile during EL and CL. The technique provided data on lateral shear strains throughout the tendon, as a route to detecting intra-tendon slip-planes. Tendon shear strain was highest during EL, with shear strain significantly dependent on loading type only, with no effect of knee ankle or muscle activity during EL, CL or MVIC. Data indicates that the extent of non-uniformity could be controlled with different exercises, offering a possible future route towards optimising treatment. However, these are not yet detected robustly enough for clinical applicability, challenged by limited resolution and the 3D nature of movements in the AT. Future work needs to improved resolution with higher frequency data acquisition to address these limitations and develop rehabilitation mechanism and injury prediction tools. | en_US |
