Long-term Effects of Using a Novel Orthotic Insole for Tactile Stimulation in Diabetic Peripheral Neuropathy and Follow-up

According to diabetic peripheral neuropathy (DPN), the significant complications include diabetic foot ulceration (DFU), an increase in vibration perception threshold (VPT), a decrease in tactile sensitivity, and lower limb amputation. A vibrating insole is a novel gadget that can help reduce VPT and improve tactile sensibility. This research project aimed to study the effectiveness of using a novel vibrating foot orthosis (VFO) combined with a random 0-100 Hz square wave pulse stimulus and pseudorandom white noise for stimulating tactile sensation in DPN. The remaining effects had also been observed after 30 days of intervention. \*Participation in this research is voluntary. The volunteers who participated in the study had 4 appointments. In the 1st appointment, the volunteers underwent clinical assessment, baseline assessment, vibration perception evaluation, and foot casting for fabricating a foot orthosis. Participants had been informed of all necessary details of the study and learned how to use the VFO safely and correctly. The participants had to use the VFO at home for 60 minutes a day over 30 days. In the 2nd to 4th appointments (the 1st, 15th, and 30th days) participants had to conduct the interventions and posttest assessment at the experimental site. A prosthetist and orthotist (PO) performed the experiment and outcome evaluation. The VFO was comprised of two major components: a vibration generator and a custom-made foot orthosis (CFO). The vibration generator was composed of two signal generator circuits: a random 0-100 Hz square wave pulse stimulus generator circuit and a pseudorandom white noise (PRWN) generator circuit. A random square wave pulse stimulus (0-100 Hz) and PRWN were integrated by using a stochastic resonance (SR) approach to become an integrated stimulus. A vibratory actuator was implanted into the CFO and received the integrated stimulus. When the integrated stimulation signals were delivered to the implanted actuators, the VFO would perform vibration to stimulate across the entire soles of the feet. In the experiments, participants were instructed to abstain from taking any medications that influence the nervous system's upkeep and any vitamins, including vitamin B3, B6, B complex, and no drinking alcohol for 48 hours prior to starting the experiments. Besides, participants have kept up with their regular regimen of other diabetes medications. Before beginning the experiment, participants needed to keep their blood sugar levels stable to avoid hypoglycemia. Participants were randomized into two interventions by a computer-generated program. Intervention 1 was using the VFO combined with the integrated stimulus for tactile stimulation at subthreshold level (90% VPT). Intervention 2 was using the VFO with only 100 Hz frequency vibration. The PO performed the experiments, pretest/baseline evaluation, and posttest assessment. The PO opened the close-sealed envelope to assign the interventions to participants. The PO and a rehabilitation doctor monitored all participants throughout the experiment and the 30-day intervention. VPT values at the 1st metatarsophalangeal joint (MTP), 5th MTP, and calcaneal area were assessed as the outcomes. The posttests were evaluated on the 1st, 15th, and 30th days. VPT assessment was performed by the VSA-3000. In VPT assessment, participants placed their feet on the VSA-3000 pedestal and laid the 1st MTP, 5th MTP, and calcaneus on the tip of the VSA-3000 stylus without pressing. The stylus would raise vibration from zero to a level perceived by participants. When participants detected the vibration, they immediately pressed the stop mouse to halt the vibrating stylus. Then a VPT value was obtained, and the assessment was repeated five times to determine an average VPT value. During the interventions, participants were assigned to take a seat in a backrest chair, and the angle of their knees to the ground was perpendicular. Then, they put their bare feet on the VFO with fastening Velcro straps or sandal shoes. Interventions were performed with a 60-minute period. The PO and doctor would check participants' vibration perception. If they felt any vibration from the VFO, they were obliged to notify the PO or doctor immediately. The interventions would be stopped, and participants would be appointed to reassess their VPT levels, and the PO would set a new subthreshold stimulation level for them in a renewed trial. Participants of Intervention 1 group would ask for voluntarily participating in the follow-up of the remaining effects after completing use of the VFO with integrated stimulus. Importantly, they also had been approved by their physicians before continuing into the follow-up. In the follow-up, participants had to continue to abstain from taking neurological drugs throughout the follow-up period. VPT assessment by the PO would performed every 7 days. The follow-up would end when VPT exceeded baseline. Electrical safety testing and risk management for medical devices were performed in accordance with EN IEC 60601-1, ISO 14971, and the protocol for permission on medical devices in Thailand by the Medical Device Control Division of the Food and Drug Administration of Thailand to ensure that the VFO was safe for use in patients and clinical trials. 0.9 power, a 2-sided significance level of 0.05, 20% dropout were used to calculate the sample size. 64 participants were required for this study.