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

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.

Repeated-measures design with cervical range of motion and errors in placement measured in 20 volunteers with no symptoms with the OSI CA-6000.

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.

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.

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.