A Novel Device to Evaluate the Vibrotactile Threshold

Abstract

This paper presents the initial prototype design of a vibrotactile threshold evaluator for the workplace (VTEW), which is portable and configurable in terms of the probe diameter (2–10 mm), applied frequency (1–500 Hz), angle of probe (0–120 deg), and displacement of probe (1–1500 μm), and is operated with a customizable LABVIEW interface. The vibrotactile threshold is the minimum amplitude of vibration that is perceived at a particular frequency by a subject and is analogous to a hearing test. It can be used to evaluate neuropathy, for instance due to carpal tunnel syndrome or peripheral neuropathy secondary to diabetes. The vibrotactile threshold (VT) at 50 Hz was evaluated using VTEW and an established device, the Vibrotactile Tester (VTT). These results were compared for validation of VTEW. Each subject underwent Phalen’s and Tinel’s test, and the results of these clinical evaluations for carpal tunnel syndrome were used to classify subjects as symptomatic and asymptomatic. The results of the VTEW and the VTT were statistically similar and the age correction developed for both devices from this study were similar to the previously conducted studies. The mean VT values from the VTEW showed an increased VT for symptomatic subjects. The low frequency range of the VTEW was used to evaluate the VT at 4 Hz, and a comparison of VT at 4 Hz and 50 Hz showed a higher sensitivity of subjects to 50 Hz as compared to 4 Hz. The gender effect on VT was also studied and discussed, along with recommendation for further investigation. A novel and highly customizable device for testing the vibrotactile threshold is presented, with results demonstrating identification of symptomatic subjects. This device could be used to regularly test workers at risk for developing carpal tunnel syndrome (e.g. assembly line workers) to monitor for elevations in VT. Other applications include using the low frequency to evaluate peripheral neuropathy.