Normal kinematics of the neck: the interplay between the cervical and thoracic spines.

The movement coordination between the cervical and thoracic spine was examined in 34 asymptomatic participants (24 female and 10 male). Three-dimensional electromagnetic motion sensors were attached to the skin overlying the head, T1, T6, and T12 spinous processes to measure the angular displacement of the cervical, upper thoracic, and lower thoracic spine during active neck movements. These displacement measurements were found to have excellent reliability, with intraclass correlation coefficient ranging from 0.899 to 0.993. The angular displacement-time curves of the cervical and upper thoracic spine were also highly repeatable, with coefficient of multiple determinations ranging from 0.900 to 0.967. Both the cervical and thoracic spines were found to contribute to active neck motion, the greatest contribution being from the cervical region in all movement directions. The inter-regional movement coordination between the cervical spine and upper thoracic spine in all three planes of movement was found to be high, as determined by cross-correlation analysis of the movements of the regions. The current results suggest that the motion of the thoracic spine, in particular the upper thoracic spine, contributes to neck mobility, and that the upper thoracic spine should be included during clinical examination of neck dysfunction.