Errors in precise examiner head placement during cervical range-of-motion measurements

Objective: To quantify errors associated with examiner-assisted neutral head placement in cervical range of motion measurements in normal subjects and to investigate the influence of these errors on range of motion measurements. Design: Repeated-measures design with cervical range of motion and errors in placement measured in 20 volunteers with no symptoms with the OSI CA-6000. Methods: Examiner placement of head position was achieved with inclinometers and triangulation. Subjects estimated pain experienced during measurements with numeric pain scales. Angular data around 3 axes were analyzed with descriptive statistics. Possible correlations between errors and other variables were investigated. Results: Drift, defined as displacement from original head positioning at first data acquisition and before initiation of motion, was negligible (+/-0.8 degrees). Standard errors in neutral head placement ranged from 1.0 degrees in axial rotation to 3.2 degrees in flexion/extension. Within-trial variability of neutral position did not correlate with between-trial differences in ranges of motion. Conclusion: Head position errors were not the primary sources of variability for between-trial measurements of cervical range of motion. The largest errors were in flexion/extension, and least, in axial rotation. Neutral position errors up to approximately 5 degrees for lateral bending, 3 degrees for rotation, and 9 degrees for flexion and extension fall within 95% CI and are the recommended lower limits for significant changes in clinical settings.