Semmes-Weinstein Monofilaments: Influence of Temperature, Humidity, and Age

Purpose: To determine whether the buckling force of Semmes-Weinstein monofilaments is influenced by changes in temperature, humidity, and aging. Methods: We tested 16 Semmes-Weinstein monofflaments from North Coast Medical, varying in age from new to 12 years old. From each kit, we used the 2.83/0.07g, 3.61/0.4g, 4.31/2g, and 4.56/4g filaments. Four observers tested the filaments under temperature/humidity conditions of 26 C/33%, 26 C/80%, 37 C/33%, and 37 C/80%. Results: Air temperature and humidity both significantly influence buckling force. At 26 C/33% the buckling force varies by an average of 2% from the standard data supplied by the manufacturer, whereas in the other 3 conditions (26 C/80%, 37 C/33%, and 37 C/80%), the buckling force can decrease by as much as 39%. Effect of age was small and not clinically relevant. Conclusions: The significant changes in buckling force of the Semmes-Weinstein monofilaments in different temperature and humidity conditions might lead to a potential misinterpretation by the examiner regarding the level of peripheral nerve function loss. This could lead to incorrect diagnosis and treatment