Comparison of the Semmes-Weinstein monofilaments with the Pressure-Specifying Sensory Device

Measuring human sensibility remains a challenge, with the primary limitation being the instrumentation traditionally available. The Pressure-Specifying Sensory Device (PSD) permits quantitation of the human pressure perception threshold by means of transducers that couple two rounded prongs to a personal computer. If just one prong is perceived in constant contact with the skin, the cutaneous pressure threshold is directly obtained, scaling along a continuum from .05 to 100 g/mm2 (readout on computer monitor). This measurement is analogous to that obtained with the series of Semmes-Weinstein monofilaments (SWM) (readout in logarithmic marking on nylon rod). The present study evaluated twenty normal volunteers and ten nerve-impaired patients with both the PSD and the SWM. There was a poor correlation between the measurement offeree (r = 0.21) and pressure (r = 0.29) obtained with the PSD and the SWM. This study reaffirms the value of measuring pressure perception threshold during the sensibility evaluation, while calling attention to selection of instrumentation for obtaining this measurement.