This narrative review examines the limited and varied interpretation of what constitutes evidence in evidence based chiropractic practice. The authors report a bias towards only one of the three evidential The majority of spinal motion studies appear to focus on the anterior vertebral motor unit. This paper discusses the vertebral subluxation (VS) element of segmental dysfunction within a facet’s centrode in relation to mechanical articular fixation along the path of instantaneous axes of motion. In effect, there would be three segmental axes of motion, one through the vertebral body, and two within each zygapophyseal joint. Discussion is offered here on the loss of facet joint motion identified as a vertebral fixation as being but one of a complex of factors comprising a vertebral subluxation (VS). It is appreciated that a change in segmental motion such as a vertebral fixation would affect all axes. It is generally accepted that mechanically, a vertebra may be fully fixated (locking), partially fixated, or subject to aberrant (erratic) motion. There is also a classification of a hypermobile subluxation – a condition not addressed in this dissertation. In essence, a VS may comprise varying degrees of dysfunction, displacement and somatosensory activation. It is seen here as a more complex consideration than just a minor mechanical disturbance. Lineal displacement and rotation may vary considerably depending on the spinal region. Somato-autonomic stimulation may be initiated by activated somatosensory sensations such as nociceptors, mechanoreceptors and proprioceptors. As noted by the World Health Organisation (WHO) definition, there are three main elements in the chiropractic model of a vertebral subluxation. This discussion is presented to explore the pathophysiological fixation element of the dysfunction in the segmental subluxation. It may be regarded as a relatively common form of dysfunction attended by chiropractors and others. The fixation has been adopted elsewhere under such synonyms as blockage, dysfunction, locking and blockade. Theories regarding the biological mechanism of a fixation are discussed and our preferred hypothesis of negative pressure (suction or adhesiveness) resulting in contraction of the articulating surfaces.
Author keywords: Vertebral subluxation - Facet fixation - Segmental fixation - Vertebral subluxation complex (VSC)
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