Reliability and validity of 3Space Isotrak in the measurement of metacarpophalangeal joint range

Abstract

This study examined the accuracy and precision of the 3Space Isotrak in the measurement of known angles on a model and of metacarpophalangeal (MCP) joint range in the hand. In the first part of the study, system accuracy and precision were determined. The mean difference (error) between the angles calculated by the Isotrak and those measured by a standard protractor was less than 2 degrees. The standard deviation (S.D.) for precision was less than 0.5 degrees. Validity and reliability of the 3Space Isotrak was then verified using subject measures. Angles measured by the Isotrak were compared with radiographic measurements of the same angles in fi ve healthy subjects. The intra-class correlation coefficient (ICC [2,1]), was. 93 which demonstrates a good agreement between the two systems. A test-retest protocol was established to study the reproducibility of the Isotrak while measuring MCP joint angles. Seven healthy subjects and four subjects with rheumatoid arthritis were tested on two different days within a week. The ICC values for all the angles measured were more than. 77 indicating a good agreement between the two measurements.