Technical Feasibility of Custom-Fabricated Auxetic Foam Insoles for Plantar Pressure Redistribution: An Exploratory Pilot and Bootstrap Resampling Investigation

Peripheral neuropathy degrades gait mechanics, elevating peak plantar pressures (PPP) and tissue ulceration risks. This exploratory pilot study evaluates custom orthotics using thermo-mechanically synthesized re-entrant auxetic foam insoles with targeted dome-shaped inserts. Bilateral dynamic gait analysis was conducted across a heterogeneous cohort (N = 9) utilizing a P-Walk 600 pressure plate and a MARVUE 2D motion capture system inside standardized footwear. To address small-sample limits, a non-parametric bootstrap resampling analysis (B = 1000) was executed. Native auxetic foam demonstrated high internal consistency ((σ*) = 12.063 kPa, Consistency Rank = 1), showing a strong numerical propensity to restrict load distribution variability compared to factory-installed over-the-counter (OTC) memory foam controls. While initial cell-adaptation cycles were observed, custom insoles reduced PPP by up to 62.2% in systemic polyneuropathies, shifting signatures beneath the exploratory clinical safety target (<200 kPa) in 55% of simulated cases. Conversely, customization triggered an adverse volumetric crowding effect in focal mononeuropathies, suggesting un-customized native auxetic foam as the preferred structural configuration for this specific cohort to avoid premature cell densification. Re-entrant cellular structures accommodate heterogeneous pathomechanics, offering an exploratory pathway for patient-specific orthotic optimization.