Effect of a carbon reinforcement for maximizing shoe outsole bending stiffness on plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration

BackgroundDifferent shoe design features can reduce peak plantar pressure to help prevent foot ulcers in people with diabetes. A carbon reinforcement of the shoe outsole to maximize bending stiffness is commonly applied in footwear practice, but its effect has not been studied to date.Research questionWhat is the effect of a carbon shoe-outsole reinforcement on peak plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration?MethodsIn 24 high-risk people with diabetes, in-shoe regional peak pressures were measured during walking at a comfortable speed in two different shoe conditions: an extra-depth diabetes-specific shoe with a non-reinforced outsole and the same type of shoe with a 3-mm-thick full-length carbon reinforcement of the outsole. The same custom-made insole was worn in both shoe conditions. Walking comfort was assessed using a Visual Analogue Scale (0–10, 10 being highest possible comfort).ResultsSignificantly lower metatarsal head peak pressures (by a median 10–22 kPa) were found with the reinforced shoe compared to the non-reinforced shoe (p < .001). In >83% of cases with the reinforced shoe and >71% with the non-reinforced shoe metatarsal head peak pressures were <200 kPa. At the hindfoot, peak pressures were significantly higher (by a median 24 kPa) with the reinforced shoe (p = .001). No significant shoe effects were found for the toes. No significant shoe effects were found for walking comfort: median 6.1 for the reinforced shoe versus 5.6 for the non-reinforced shoe.SignificanceAdding a full-length carbon reinforcement to the outsole of a diabetes-specific shoe significantly reduces peak pressures at the metatarsal heads, where ulcers often occur, in high-risk people with diabetes, and this does not occur at the expense of patient-perceived walking comfort.