Precision and repeatability analysis of Optotrak Certus as a tool for gait analysis

In both scientific and clinical investigations, the precision and repeatability of instruments are demanded; however, precision of motion analysis systems has been reported in the literature rarely and studies are generally not comparable. This study introduces a new method of determining precision and repeatability of Optotrak Certus, a motion analysis tool for gait analysis using a three dimensional (3D) robot. Using 3D robot as reference of standard for distance, the angle and velocity measurement, the accuracy and precision of the Optotrak Certus in terms of angle, distance between markers were quantitated. The standard deviation (SD) and the coefficient of variation (CV) provide a measure of precision whereas the coefficient of multiple correlation (CMC) provides a measure of repeatability. Experimental results containing CMC, CV and SD values for variation of angle, volume, circular movement and speed were demonstrated to analyze the repeatability; hence the repeatability was satisfactory. Angle and distance between markers showed good agreement between measurements, and comparable measures of precision are reported as well as CMC and CV values. The investigation is ethical and practical in measurement analysis in terms of precision and repeatability.