Reducing foot plantar pressure using superelastic nitinol monofilaments as spacer yarns in a novel weft knitted spacer fabric insole

Abstract

Insoles as devices for plantar pressure reduction have developed and undergone many clinical experiments to deliver better performance, helping patients with diabetic foot ulceration. Elastomer foams are used as the base material in commercial diabetic foot insoles. However, their energy absorption capacity degrades because of microclimate in footwear and their shape deform during usage. Therefore insoles with better-cushioning properties and durability are required. In this paper, a novel insole with 3D spacer fabric with superelastic nitinol monofilaments (NiTi) is introduced. The fabricated insole and commercial Plastazote insoles (PLT) are experimentally compared on five healthy persons with measuring plantar pressure right after wearing and 1 month after. The temperature increase is also measured after 15 min of walking. Statistical analysis is used to evaluate insoles performance. Although NiTi and PLT showed a reduction in peak plantar pressure (PPP) right after wearing, after one month, 48.5% and 43.8% reduction in mean PPP for NiTi and 28% and 23.9% for PLT were observed compared to without-insole condition on the right and left foot respectively. NiTi delivered 11.8% and 13.9% PPP increases on right and left foot compared to 61% and 61.8% respectively in PLT after 1 month. Lower temperature increase and homogenous plantar surface pressure distribution were also seen on NiTi. Eventually, the proposed NiTi insole delivered higher cushioning properties, enhanced breathability, more uniform pressure distribution, and superior endurance compared to PLT as a commercial insole. Therefore, it is a promising device for protecting the diabetic foot against pressure, impact and preventing ulceration.