Objective: This study focussed on pressure relieving orthotic insoles designed for retail footwear and people with diabetes and at risk of first forefoot ulceration. The aim was to investigate whether the pressure relieving effects of a customised metatarsal bar and forefoot cushioning are sensitive to bar location and shape, and material choice.
Research design and methods: Patient-specific foot shape was used to design an orthotic insole, with metatarsal bar location and shape customised according to plantar pressure data. Changes in forefoot plantar pressure were investigated when 60 people with diabetes and neuropathy walked in nine variants of the orthotic insole. These comprised three variations in proximal/distal location of the customised metatarsal bar and three different metatarsal head offloading materials.
Results & conclusions: The most frequent reductions in pressure occurred when the anterior edge of the metatarsal bar was placed at 77% of the peak pressure values, and its effects were independent of the choice of EVA or Poron offloading material. In the flat insole, 61% of participants had one or more metatarsal head areas with pressure above the 200 KPa, reducing to 58% when adopting generic orthotic design rules and 51% when using the best orthotic insole of the nine tested. Our results confirm that plantar pressure relief is sensitive to orthotic insole design decisions and individual patient feet.
Keywords: CAD/CAM; Diabetic foot; Orthotic; Prevention; Ulcer.