A Pilot Study of a Tactile Measurement System Using Lateral Skin Stretch on Foot Plantar Surface

The purpose of this study is to develop smart equipment to quantify plantar tactile sensibility for early diagnosis and tracking of peripheral neuropathy caused by diabetes mellitus. In this paper, we present new testing equipment composed of a plantar tactile stimulation platform with a moving contactor to stretch the skin tangentially, a response switch for each tactile stimulus, a motor control box, and a personal computer for psychophysical data processing. This testing equipment offers more precise measurements and is easy to use compared to conventional testing tools such as von Frey monofilaments, pin-prick testing devices, and current perception threshold testers. Using our testing equipment, we showed that the plantar tactile threshold for the tangential stretching stimulus on the first metatarsal head of the feet ranges from approximately 10 to 60 μ m for subjects without diabetic foot problems. Meanwhile, the plantar tactile threshold of some subjects suspected of having diminished protective sensation by the Semmens-Weinstein monofilament testing is approximately 100 μ m or more. These preliminary results suggest that our testing equipment based on the plantar sensation elicited by lateral stretching of skin has the potential for quantitative diagnosis in subjects suspected of suffering from neuropathy, and for monitoring changes over time to sustain quality of life.