Muscle palpation with controlled finger pressure: new equipment for the study of tender myofascial tissues.

While manual palpation is the most important method for evaluation of tender myofascial tissues, it lacks reliability. Therefore, we have developed an instrument, called a 'palpometer', which allows the measurement of pressure exerted during palpation. The palpometer consists of a thin pressure-sensitive plastic device attached to the palpating finger, and of a scale recording the pressure applied to the device. Known forces were applied to the pressure sensitive device under various experimental conditions and the corresponding values were read on the palpometer scale. Then 14 observers, blinded to the palpometer scale, palpated the temporal muscle on the same subject twice, with an interval of 1 week. A highly significant correlation was found between palpometer recordings and forces applied to the pressure-sensitive device (P < 0.0001). Exerted force at a given palpometer value varied 3.1% within and 7.2% between 2 observers. During palpation of the temporal muscle pressure intensities within the 14 observers did not differ significantly from week to week (P = 0.68). Between the 14 observers pressure intensities varied considerably with a range of 73.5-196 arbitrary units. Thus, a reliable instrument for measuring pressure intensities during palpation of myofascial tissue has been developed. The large variation in palpation pressures between observers indicates that palpation of tender myofascial tissue may be considerably improved by use of the palpometer. This instrument will be indispensable in research studies employing palpation and in the training of physicians to diagnose myofascial pain disorders.