Abstract
Some activities of daily living require that the head be kept level during axial rotation of the cervical spine (Kinematically Constrained Axial Rotation). One such activity is looking over one's shoulder when walking or driving. The kinematic constraint of keeping the head level during axial rotation means that the segmental axis of rotation may not be aligned with the global axis of rotation of the cervical spine. Most of the literature on cervical spine axial rotation is based on experiments where the segmental axis of rotation is aligned with the global axis of rotation (Traditional Axial Rotation). There are only a few clinical and biomechanical studies that have examined kinematically constrained cervical axial rotation. We performed a series of biomechanical experiments in which we tested cervical spines in traditional and kinematically constrained axial rotation. The resulting primary and coupled motions of the segments showed that kinematically constrained axial rotation is distinct from traditional axial rotation. Our findings and the findings of other kinematically constrained axial rotation studies will be compared and contrasted with data from traditional axial rotation studies.
