Influence of cranio-cervical posture on three-dimensional motion of the cervical spine.

Although a consistent pattern of ipsilateral movement coupling between cervical spine rotation and lateral flexion has been widely described, variability in these movement patterns has not been reported. In 30 asymptomatic subjects, the ranges of primary and coupled movements were determined in the neutral posture, and in the extremes of cervical spine protraction and retraction. All measurements were performed using the SpinT three-dimensional goniometer for which excellent intra-tester reliability was demonstrated for both primary (ICC(3,1) 0.93-0.98) and coupled (ICC(3,1) 0.76-0.98) movements. The ranges of primary and coupled movements changed significantly when movement was initiated from the end-range postures (P < 0.001). In the neutral posture, approximately 70% of subjects demonstrated an ipsilateral pattern of coupled movement. During cervical rotation, the dominant coupling pattern seen in neutral was no longer retained in retraction, while the protracted posture had a greater influence on the coupled movements accompanying primary lateral flexion. The concept of a stereotypical pattern of cervical spine movement coupling is not supported by these results. The posture in which movements are initiated appears to have a significant influence on the three-dimensional kinematics of the cervical spine.