A comparison of pisiform and thumb grips in stiffness assessment

Abstract

Background and Purpose. The purpose of this study was to determine whether two versions of the posteroanterior (PA) pressure test provide similar stiffness information. Subjects. Twenty subjects were asked to judge the magnitude of five stiffness stimuli provided by a mechanical device. Methods. Subjects were required to rate the stiffness magnitude on a five-point scale using both the thumb-grip and pisiform-grip versions of the PA pressure test. Using signal detection theory methods, measures of both a subject's ability to discriminate between the stiffness stimuli and a subject's bias in perceived stiffness magnitude due to the testing method were obtained. These values were compared using analysis of trend within an analysis of variance framework. Results. The two methods of performing the PA central pressure had similar stimulus discriminability. With the thumb-grip method, however, a substantial bias occurred, making the mechanical stimuli appear to be stiffer than when the pisiform grip was used. Conclusion and Discussion. The method of performing the PA central pressure test affects the perceived magnitude of stiffness stimuli. This result suggests that the two versions of this clinical test should not be used interchangeably.