Vibrometry testing for carpal tunnel syndrome: a longitudinal study of daily variations.

The method of limits procedure was used to obtain 84 120Hz vibration thresholds, over a 3-month period, on four age-matched women with different levels of carpal tunnel syndrome (CTS). Each woman used a keyboard for 4 hours a day during work. Testing was conducted in a room with a temperature of 28 degrees C +/- 2 degrees C after 20 minutes acclimation. Results indicate vibration thresholds vary significantly from day to day and also demonstrate how a single vibrometry measure may falsely identify the participant's true CTS condition. Specifically, a single measure could account for a negative CTS determinations in affected wrists or positive CTS determinations in healthy wrists. Subsequent analysis revealed menses related fluid retention and day of the week increase the vibration thresholds. Analyzing the levels of fluid retention by day of the week indicates a compounding effect of the personal and occupational risk factors.