The use of the Zebris motion analysis system for measuring cervical spine movements in vivo.

The cervical spine exhibits the greatest range of motion among the spinal segments due to the complex interaction of its triplanar components of movement. As a result, measurement of movements of the cervical spine and of the various orthoses used in cervical spine injuries has proved difficult with no one method proving satisfactory. This paper uses the Zebris ultrasonic three-dimensional motion analysis system to measure flexion, extension, range of lateral bending, and range of axial rotation in five similar male and five similar female subjects with no history of neck injuries. The subjects were tested unrestrained and in soft and hard collars, as well as in Philadelphia, Miami J, and Minerva orthoses. Results show that the Minerva is the most stable construct for restriction of movement in all planes in both groups. Looking at these results allows ranking of the measured orthoses in order of their three-dimensional stability. Furthermore, by presenting reproducible data incorporating the composite triplanar movements of the cervical spine, thus allowing comparative analysis of the studied orthoses, they propose the Zebris as a reliable, repeatable, and safe method of measurement of cervical spine motion with low intersubject variability.