Variations in two-point discrimination as a function of terminal probes

A study was designed to investigate the role of terminal probes as determinates of two-point discrimination in the normal hand. A Vernier caliper was modified to allow an exchange of probes with different diameters and with different terminal shapes. These terminal devices included flat, sharp, and rounded probe tips of various diameters. There was variability in normal subjects for different end probes and our results indicated that spherical probes give the largest variation in two-point discrimination while pointed end probes provide the least variation. Variations of up to two millimeters can occur between large and small diameter probes. This study quantitatively supports the contention that different terminal devices will produce different recruitment of the sensory end organs in the hand, and strongly suggests the need for standardization of condition in assessment of sensory recovery.