A pilot study of a plantar sensory evaluation system for early screening of diabetic neuropathy in a weight-bearing position

The purpose of this study is to develop smart equipment to quantify plantar tactile sensibility for the early diagnosis and tracking of peripheral neuropathy caused by diabetes mellitus. In this paper, we offer a new testing system that is composed of a plantar tactile stimulation platform with a small moving contactor to stretch the skin tangentially, a response switch for each tactile stimulus, a motor control box, and a personal computer (PC) for psychophysical data processing. This quantitative sensory testing system has detailed measurements available and is easy to use compared with the conventional testing devices, such as von Frey monofilaments, pin-prick testing devices, and current perception threshold testers. When using our testing system in a weight-bearing position, we observed that the plantar tactile thresholds for the tangential stretching stimulus on the plantar surface of the foot ranged from approximately 10 um to 30 um for healthy subjects. However, the threshold for a subject with diabetes was nearly three times higher than that for healthy subjects. The significant difference between these values suggests that the plantar sensory evaluation system using the lateral skin stretch stimulation can be used for early diagnosis, for the accurate staging of diabetic neuropathy, and for evaluating its progression noninvasively in a clinic and at home.