title: Three-dimensional analysis of cervical spine segmental motion in rotation.
abstract: BACKGROUND
  The movements of the cervical spine during head rotation are too complicated to measure using conventional radiography or computed tomography (CT) techniques. In this study, we measure three-dimensional segmental motion of cervical spine rotation in vivo using a non-invasive measurement technique.
  
  
  METHODS
  Sixteen healthy volunteers underwent three-dimensional CT of the cervical spine during head rotation. Occiput (Oc) - T1 reconstructions were created of volunteers in each of 3 positions: supine and maximum left and right rotations of the head with respect to the bosom. Segmental motions were calculated using Euler angles and volume merge methods in three major planes.
  
  
  RESULTS
  Mean maximum axial rotation of the cervical spine to one side was 1.6° to 38.5° at each level. Coupled lateral bending opposite to lateral bending was observed in the upper cervical levels, while in the subaxial cervical levels, it was observed in the same direction as axial rotation. Coupled extension was observed in the cervical levels of C5-T1, while coupled flexion was observed in the cervical levels of Oc-C5.
  
  
  CONCLUSIONS
  The three-dimensional cervical segmental motions in rotation were accurately measured with the non-invasive measure. These findings will be helpful as the basis for understanding cervical spine movement in rotation and abnormal conditions. The presented data also provide baseline segmental motions for the design of prostheses for the cervical spine.
authors.affiliation: Department of Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Zhao
authors.forename: Zi-Xiang
authors.initials: ZX
authors.lastname: Wu
authors.forename: Bao-Jun
authors.initials: BJ
authors.lastname: Han
authors.forename: Ya-Bo
authors.initials: YB
authors.lastname: Yan
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Lei
keywords: cervical spine; coupled motion; in vivo; rotation; segmental motion