title: Validation protocol for assessing the upper cervical spine kinematics and helical axis: An in vivo preliminary analysis for axial rotation, modeling, and motion representation.
abstract: BACKGROUND
  The function of the upper cervical spine (UCS) is essential in the kinematics of the whole cervical spine. Specific motion patterns are described at the UCS during head motions to compensate coupled motions occurring at the lower cervical segments.
  
  
  OBJECTIVE
  First, two methods for computing in vitro UCS discrete motions were compared to assess three-dimensional (3D) kinematics. Secondly, the same protocol was applied to assess the feasibility of the procedure for in vivo settings. Also, this study attempts to expose the use of anatomical modeling for motion representation including helical axis.
  
  
  METHODS
  UCS motions were assessed to verify the validity of in vitro 3D kinematics and to present an in vivo procedure for evaluating axial rotation.
  
  
  METHODS
  In vitro kinematics was sampled using a digitizing technique and computed tomography (CT) for assessing 3D motions during flexion extension and axial rotation. To evaluate the feasibility of this protocol in vivo, one asymptomatic volunteer performed an MRI kinematics evaluation of the UCS for axial rotation. Data processing allowed integrating data into UCS 3D models for motion representation, discrete joint behavior, and motion helical axis determination.
  
  
  RESULTS
  Good agreement was observed between the methods with angular displacement differences ranging from 1° to 1.5°. Helical axis data were comparable between both methods with axis orientation differences ranging from 3° to 6°. In vivo assessment of axial rotation showed coherent kinematics data compared to previous studies. Helical axis data were found to be similar between in vitro and in vivo evaluation.
  
  
  CONCLUSIONS
  The present protocol confirms agreement of methods and exposes its feasibility to investigate in vivo UCS kinematics. Moreover, combining motion analysis, helical axis representation, and anatomical modeling, constitutes an innovative development to provide new insights for understanding motion behaviors of the UCS.
authors.affiliation: Laboratory of Functional Anatomy, Department of Physiotherapy and Rehabilitation, Faculty of Motor Sciences, Free University of Brussels, Brussels, Belgium ; Research Unit of Osteopathy, Department of Osteopathic Sciences, Faculty of Motor Sciences, Free University of Brussels, Brussels, Belgium.
authors.forename: Pierre-Michel
authors.initials: PM
authors.lastname: Dugailly
authors.affiliation: Laboratory of Anatomy, Biomechanics and Organogenesis, Department of Anatomy, Faculty of Medicine, Free University of Brussels, Brussels, Belgium.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Sobczak
authors.affiliation: Laboratory of Anatomy, Biomechanics and Organogenesis, Department of Anatomy, Faculty of Medicine, Free University of Brussels, Brussels, Belgium.
authors.forename: Alphonse
authors.initials: A
authors.lastname: Lubansu
authors.affiliation: Laboratory of Functional Anatomy, Department of Physiotherapy and Rehabilitation, Faculty of Motor Sciences, Free University of Brussels, Brussels, Belgium ; Laboratory of Anatomy, Biomechanics and Organogenesis, Department of Anatomy, Faculty of Medicine, Free University of Brussels, Brussels, Belgium.
authors.forename: Marcel
authors.initials: M
authors.lastname: Rooze
authors.affiliation: Laboratory of Anatomy, Biomechanics and Organogenesis, Department of Anatomy, Faculty of Medicine, Free University of Brussels, Brussels, Belgium.
authors.forename: Sergevan Sint
authors.initials: SS
authors.lastname: Jan
authors.affiliation: Laboratory of Functional Anatomy, Department of Physiotherapy and Rehabilitation, Faculty of Motor Sciences, Free University of Brussels, Brussels, Belgium ; Laboratory of Anatomy, Biomechanics and Organogenesis, Department of Anatomy, Faculty of Medicine, Free University of Brussels, Brussels, Belgium.
authors.forename: Véronique
authors.initials: V
authors.lastname: Feipel
keywords: Helical axis; in vivo kinematics; modeling; motion representation; upper cervical spine; validation