Evaluation of orthotic insoles for people with diabetes who are at-risk of first ulceration

Abstract

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.

Fig. 1

Design of the metatarsal bar and void and different orthotic insoles used for the study with different cushioning materials

Fig. 2

Pedar insoles sensor array and mask used for the pressure analysis

Fig. 3

The effect of varying metatarsal bar location (a-d) and materials (e-h) on peak plantar pressures in the four different anatomical regions. Po = Poron, Vo = void. Vertical lines = standard deviation. Horizontal lines indicate significant differences (p < 0.05 after Bonferroni correction)

Fig. 4

Comparison of peak pressures between the flat insole and the nine orthotic insole conditions in each of the four different anatomical regions. The three bars in void condition (EVA, Poron, Void) correspond to proximal, middle and distal metatarsal locations from left to right. The horizontal dotted line illustrates the flat insole pressure and * denotes a significant difference (p < 0.05) between an orthotic insole condition and the control insole following Bonferroni correction