| Foot ulcer is a common complication of diabetes mellitus and the predisposing factors are multifactorial. The morphological change in plantar skin, foot swelling and changes in the properties of plantar soft tissues may increase the risk of foot ulceration in people with diabetes. In order to develop strategies to prevent or manage diabetic ulcers, it is vital to obtain a better understanding of the underlying pathophysiology of diabetic ulcers. Also, a precise and quantitative method for evaluating the healing of ulcers is essential for making appropriate treatment decisions and monitoring the efficacy of the treatments. An optical coherence tomography (OCT)-based air-jet indentation system is a novel non-contact method that has been recently developed for characterizing the biomechanical properties of soft tissues in a non-contact way. It can potentially be used for assessing the properties of wound tissues in vivo..;This thesis consists of four inter-related studies. They are: (I) The epidermal thickness and biomechanical properties of plantar tissues in the diabetic foot; (II) The association between skin blood flow and oedema on epidermal thickness in the diabetic foot; (III) A novel non-contact method to assess the biomechanical properties of wound tissue in humans; (IV) In vivo and in vitro approaches to studying the biomechanical properties of healing wounds in rat skin.;Overall, the present thesis demonstrated that the newly developed OCT-based air-jet indentation system is a reliable tool for characterizing the stiffness of soft tissues around the wound in a non-contact way in vivo. The epidermal plantar skin became thinner and the plantar soft tissues stiffened for people with diabetes, particularly for those with neuropathy or ulceration, the epidermal plantar skin became thinner and the plantar soft tissues stiffened. In addition, subepidermal oedema was demonstrated in people with diabetic neuropathy and ulceration, which may partly contribute to a reduction in epidermal thickness at the pulp of the big toe. All of these changes may subsequently lead to the breaking down of skin in the diabetic foot. This implies that diabetes-associated changes in the biomechanical properties of plantar skin, plantar soft tissues, and foot swelling are potential risk factors of foot ulceration in people with diabetes. |
