A Novel Approach to Describe Cervical Kinematics

Barbero, Marco and Cattrysse, Erik and Clijsen, Ron and Cescon, Corrado (2013) A Novel Approach to Describe Cervical Kinematics. In: 3° Congresso Nazionale SIF, 24-25 Maggio 2013, Napoli.

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BACKGROUND AND AIM The helical axis approach can provide a comprehensive three-dimensional description of joint motion. An instantaneous helical axis (IHA) changes its spatial position and orientation during movement and the infinitesimal spatial motion of a joint segment is expressed as the combination of a translation along this axis and a rotation around it. An analysis of the IHA behavior during movements has an important potential application in the description and differentiation of functional and dysfunctional joint movements. Currently most studies exploring the clinical application the IHA produce excellent qualitative results, but quantitative results are often lacking. The aim of this study is to provide a representation of the IHA as a function of the angular velocity allowing a further quantitative analysis. MATERIALS AND METHODS Cervical kinematics was registered a non-invasive electromagnetic device (Polhemus-G4). One sensor was positioned on the subjects’ forehead and one on the chest. The subject was asked to perform a series of head rotations at a natural spontaneous speed. The intersections of the IHA with a standardized coronal plane were computed and analyzed with the convex hull technique using different thresholds for angular velocity. RESULTS The IHA behavior and their intersections with the coronal plane during repeated active rotations is displayed with a three-dimensional visualization (Fig.1A). Intersections of IHA with the coronal plan are shown in figure 1B. Convex hull areas on the coronal plane according to different angular velocity threshold are shown in figure 1C. DISCUSSION A variability of IHA during rotation can be observed. As expected, at lower angular velocities the IHA are spread in a larger area because of the noise of the sensors has a larger impact on their computation. Nevertheless, at higher velocity, most of the IHA intercept the coronal plane in a restricted area and the convex hull is minimal. CONCLUSIONS The IHA behavior is more stable at higher angular velocity. Any quantity analysis of the IHA should consider a proper angular velocity threshold. The IHA behavior assessed with the convex hull technique shows an interesting potential for clinical application. A reliability investigation on a larger sample is required. KEYWORDS: Cervical spine, head movements, kinematics, instantaneous helical axis. ACKNOWLEDGEMENT Thim van der Laan Foundation for funding the study.

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