Plantar tissue stress in people with diabetes A biomechanical and behavioural perspective on foot ulceration

Every moment of the day that we walk or stand, our feet are loaded. This continuous or repetitive foot loading can significantly affect our feet. Understanding how different factors contribute to the loading of the foot is important, especially in vulnerable people with foot problems. Diabetes-related foot ulcers - a common and burdensome complication of diabetes – typically develop from excessive mechanical stress on insensate plantar tissue, caused by peripheral neuropathy. Although this mechanical pathway is recognized as the most common cause of plantar foot ulceration, the exact role of plantar tissue stress remains unclear. The plantar tissue of the feet in people with diabetes bears an amount of mechanical stress that depends on various biomechanical and behavioural factors, such as plantar pressure, shear stress, the amount of weight-bearing activity and whether footwear is worn or not. Only a few prospective studies have focused on plantar tissue stress in people with diabetes at high risk of ulceration. Therefore, several unanswered questions remain, such as whether walking speed and type of weight-bearing activities influence people’s plantar tissue stress? What impact does adherence to footwear have on one’s plantar tissue stress? Does a person’s gait pattern affect plantar tissue stress? How can we best measure plantar tissue stress? And how is plantar tissue stress related to the development of foot ulcers in people with diabetes mellitus? In this thesis, these questions are investigated to better understand the association between plantar tissue stress and foot ulceration in people with diabetes at high risk.