Improving the design of the curved rocker shoe for people with diabetes

Jonathan D Chapman

PhD Thesis 2014

AbstractIntroductionFoot ulceration and re-ulceration are a serious problem in people with diabetes as the outcome can be lower limb amputation, reducing quality of life and increasing mortality. The pathogenesis of foot ulceration is multifactorial with neuropathy, alterations in foot structure, callus formation and increased plantar foot pressure. The most effective intervention for reducing plantar pressure is the curved rocker outsole. To date this design has been prescribed from clinical intuition rather than scientific evidence. Therefore the studies within this thesis aimed to improve our understanding of how to best to design, and also prescribe, a rocker sole.
MethodsEthical approval was obtained from the University of Salford and the NHS. Study 1 investigated the independent effect of varying the three outsole design features (apex angle, apex position and rocker angle) on plantar pressure in 24 people with diabetes and healthy participants. In-shoe pressure data was collected using Pedar-x and analysed using Matlab. Study 2 investigated the effect of varying apex position in combination with rocker angle, in 87 people with diabetes, and aimed to establish how many people would receive sufficient offloading when wearing a pre-defined rocker design. Study 3 investigated a new method of prescribing a rocker sole using artificial neural networks with an input of gait variables on 78 people with diabetes. Gait data was collected using Vicon and analysed using Visual-3D and Matlab.
ResultsThe results of Study 1 suggested that fixing apex angle at 95° would be a suitable compromise to offload the high risk areas (medial forefoot). It also suggested that apex position and rocker angle needed more investigation. Therefore, in Study 2 the combined effect of two rocker angles and four apex positions were investigated. Despite some inter- subject variability, this study showed that over 60% of participants received sufficient offloading when walking in a mean optimal design. Furthermore, over 60% of people received sufficient offloading with the smaller rocker angle of 15°. The results in Study 3showed there was low accuracy when predicting an individual optimal shoe using gait variables as inputs (34-49%).
ConclusionsThis project has shown it is possible to significantly reduce plantar pressures in people with diabetes with a well-designed rocker shoe (95° apex angle, individual apex position and 15° rocker angle). This finding paves the way for future clinical trials which could provide robust clinical evidence for the use of rocker shoes.
Source: http://usir.salford.ac.uk/31862/1/PhD_Thesis_Jonathan_D_Chapman_2014.pdf

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