BACKGROUND: Practitioners of Manual Medicine usually use High-Velocity Low-Amplitude (HVLA) thrust to manage different types of musculoskeletal disorders affecting the spine. Although different effects on the body system have been shown (mechanical effects, neurophysiological effects on the axial muscles as well as on the peripheral muscles and on sensitivity), it is still quite controversial whereas this practice is safe or not on the cervical spine. The greatest debate on this subject is if the use of cervical spine manipulation has higher risk of vital structure injury than real benefits for the patients. On one hand there are several studies that show possible vertebral artery involvement, however, on the other hand, there is extensive research that shows the limited impact on vital structures during HVLA technique.
METHODS: A Zebris CMS20 ultrasound-based motion tracking system was adopted to analyse the complex multidimensional kinematics of 20 fresh specimens’ upper cervical spine. Two therapists performed 3 consecutive HVLA thrusts on each specimen. The kinematic of the centre of the bone embedded reference frame and the displacement of the centre of the facet joints were analysed.
RESULTS: Considering the translation of the centre of the reference frame during the entire manoeuvre, a mean medio-lateral translation of 7.5 mm (SD 10.6), a caudo-cranial translation of 5.1 mm (SD 4.0), a postero-anterior translation of 9.4 mm (SD 8.1) and a Norm of 14.9 mm (SD 12.0) were reported. Considering the displacement of the facet joints the descriptive statistics showed a mean Norm displacement during the thrust of 0.5 mm (SD 0.5). The maximum displacement, representing the overall facet movement from neutral to end-range position, indicated a Norm value of 6.0 mm (SD 3.4). Heterogeneous displacement directions were found during the thrust. Intra and inter-rater reliability reached an insufficient reproducibility level.
The kinematic analysis based on the centre of rotation has shown unreliable results. These unrealistic amounts of translations come from a methodological issue related to the representation of motion analysis that has affected the outputs. More reliable methods as the FHA, displacement of two related points and the contact area approach should be adopted.
Moreover, our in-vitro research showed that the displacement of C1 relative to C2 facet joints induced with a combined motion HVLA thrust is unintentional, unpredictable and not reproducible. However it seems not to be able to endanger vital structure on the Spinal Cord and the Vertebral Artery as the displacement induced is not clinically relevant.

Further research to analyse the movement of C1-C2 facet joints during mobilisation into rotation, lateral bending and flexion-extension may be useful to understand the kinematic of the cervical spine during axial manual techniques. Understanding possible relationship between morphology and kinematic movement will be another interesting topic to explore.


ConferenceCombined 10th Annual Academy Science Board Conference and 7th bi-annual Academy Conference of the International Academy of Manual/Musculoskeletal Medicine, Brussels, Belgium, 6-7 November 2015


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