Reproducibility of global three-dimensional motion during manual atlanto-axial rotation mobilization: an in vitro study

Reproducibility of global three-dimensional motion during manual atlanto-axial rotation mobilization: an in vitro study
Erik Cattrysse1, Steven Provyn1, Patrick Kool2, Jan Pieter Clarys1, Peter Van Roy1
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Department of Experimental Anatomy and 2Department of Applied Mechanics, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Belgium The reproducibility of thethree-dimensional (3D) kinematic aspects of motion coupling patterns during manual mobilizing techniques is still a debatable matter. The present in vitro study analysed segmental 3D motion of the atlanto-axial joint during manual axial rotation mobilization. Twenty fresh frozen human cervical specimens were studied in a test–retest situation with two examiners. The specimens were manually mobilizedusing three different techniques: (1) a regional mobilization technique of the cervical spine; (2) a segmental mobilization technique of the atlas with manual fixation of the axis; and (3) a segmental mobilization of the atlas on the axis applying a locking technique. Segmental atlanto-axial kinematics was registered with a Zebris CMS-20 ultrasound-based tracking system. The Euclidian norm was usedas a representation of overall 3D motion. The results indicated good reproducibility (mean intraclass correlation coefficient, ICC: 0.87). Intraobserver reproducibility was slightly higher (mean ICC: 0.91; range: 0.76–0.99) than interobserver reproducibility (mean ICC: 0.85; range: 0.56–0.98) (P , 0.05). The total range of motion expressed as the Euclidean norm of 3D motion components was aparameter with good reproducibility in the study of segmental kinematics of manual atlanto-axial mobilization. Although previous studies have demonstrated poor inter-rater reliability of manual examination and mobilization of segmental motion components, the results of the present study shed a new and more positive light on the reproducibility of techniques for manual mobilization of the upper cervicalspine.

Keywords: Atlas, Axial rotation, Axis, Euclidean norm, In vitro, Manual mobilization, Reliability reproducibility

Very few studies have examined the kinematics of spinal manipulative therapy. Some authors have focused on the global range of motion of the cervical spine during high-velocity thrust techniques.1–3 Even the reproducibility of the clinical manual examination andmobilization of joints in general and of the spine in particular is a much debated subject, and substantial evidence is rather sparse and exemplary. Some authors found strong variability between the ratings of cervical intervertebral mobility among examiners, whereas others have indicated that the combination of several regional and segmental examination techniques can lead to an adequate and reproducibledifferentiation between patients and controls.4–8 In recent publications, investigators have sometimes still relied on two-dimensional methods of spinal motion analysis. It is generally accepted that a threedimensional (3D) approach offers a far more realistic
Correspondence to: Erik Cattrysse, Department of Experimental Anatomy, Faculty of Physical Education and Physiotherapy, Vrije UniversiteitBrussel, Brussels, Belgium. Email: ecattrys@vub.ac.be

representation.9 However, the use of surface markers seems to be a major barrier for in vivo 3D segmental motion evaluation by video-analysis due to uncontrollable (skin) artifacts.10 Although offering a unique situation for investigating 3D segmental movements in vivo, the use of Kirschner pins or other percutaneous instrumentationrequires invasive procedures and is seldom approved by ethical committees. To combine a 3D kinematics approach with a segmental motion analysis, most authors have proposed in vitro laboratory set-ups.11–13 Although these studies have used well- controlled moments of force to induce movements and have even attempted to simulate manual mobilizing techniques, thus eliciting the possible specific effects of...