Redesigning diabetic foot risk assessment for amputation prevention in low-resource settings: Development of a purely mechanical plantar pressure evaluation device

Abstract

As global diabetes rates skyrocket, diabetic foot complications constitute a massive and rapidly growing global health problem, causing one million lower-extremity amputations every year. These amputations are typically preceded by largely preventable diabetic foot ulcers (DFUs). However, 80% of the world’s more than half a billion diabetics now live in low- and middle-income countries, where many healthcare settings lack the resources to implement recommended diabetic foot risk assessment and risk-based DFU prevention practices. Thus, the objective of this thesis was to redesign diabetic foot risk assessment specifically for low-resource settings in order to enable more efficient resource allocation for amputation prevention.

To this end, a novel, low-cost, purely mechanical plantar pressure evaluation device was designed. The device consists of a grid of plastic bistable compliant mechanisms whose geometries can be tuned to generate a desired pressure threshold at which one part moves to a second stable position. The grid therefore presents a visual series of binary outputs in response to applied pressure. By having diabetic patients step on the device, non-specialist healthcare providers can easily assess patients' plantar pressures, which are known to be predictive of future DFU. A prototype was used to solicit feedback from 20 healthcare providers in Kenya. A design iteration was conducted based on their feedback, and an updated prototype was fabricated. The ability of this prototype to detect high plantar pressures was tested in a study with 41 healthy subjects. The prototype demonstrated a specificity of 100% and a sensitivity of 25.6%, though sensitivity reached 60% for heavier subjects. Sensitivity could likely be significantly improved by lowering the device's profile and increasing the sensing area. Strained health systems may then be able to use this device to allocate scarce healthcare resources more efficiently to prevent costly DFUs and amputations.