August 2019

Orthotic insoles for people with diabetes at-risk of ulceration

By Ana Martinez-Santos, Stephen Preece, and Christopher J. Nester

This study focused 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 customized 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 customized according to plantar pressure data. Changes in forefoot plantar pressure were investigated when 60 people with diabetes and neuropathy walked in 9 variants of the orthotic insole. These comprised 3 variations in proximal/distal location of the customized metatarsal bar and 3 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 (see Figure). In the flat insole, 61% of participants had 1 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 9 tested. Our results confirm that plantar pressure relief is sensitive to orthotic insole design decisions and individual patient feet.

Source: Ana Martinez-Santos A, Preece S, Nester CJ. Evaluation of orthotic insoles for people with diabetes who are at-risk of first ulceration. J Foot Ankle Res. 2019;12:35. Use is per Creative Commons Attribution License. Full article is available at https://jfootankleres.biomedcentral.com/articles/10.1186/s13047-019-0344-z

Figure. The effect of varying metatarsal bar location (a-d) and materials (e-h) on peak plantar pressures in the four different anatomical regions.
EVA = ethylene vinyl acetate. Po = Poron, Vo = void. Vertical lines = standard deviation. Horizontal lines indicate significant differences (p < .05 after Bonferroni correction)

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