Background: Segmental manual spinal mobilization techniques are used to restrict the effects of interventions to one spinal segment. It is, however, not known whether it is possible to generate such a localization of effects. Segmental motion in the cervical spine was previously studied by applying pure moments of force on cadaver specimens. So far, no studies have been performed on the segmental three-dimensional (3D)-kinematic aspects of cervical manual flexion-extension mobilization.
Methods: 3D-aspects of manual flexion-extension motion in the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Segmental bony reference points were registered using a 3D-digitizing stylus to define bone-embedded coordinate frames. Six spinal specimens--five embalmed and one fresh--were analysed in this study. Segmental motions were analysed in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of flexion-extension mobility. The 3D-kinematic analysis of two different segmental mobilization techniques--manual fixation of C1 versus locking of the inferior cervical spine--is presented.
Results: A significant reduction (P<0.05) of the associated axial rotation and lateral bending motions was observed during the manual fixation technique without influencing the main motion component of flexion-extension. The locking technique did not significantly influence the movements on the mobilized atlanto-occipital segment, but reduced all movement components in the atlanto-axial joint.
Interpretations: The results suggest that, for manual segmental flexion-extension mobilization of the upper cervical spine, manual fixation or locking might be chosen in different situations according to the desired effects.