OBJECTIVE: The purpose of this study was to measure the relative movements of vertebrae during manipulative thrusts to unembalmed post-rigor mortis human cadavers.

SETTING: The investigation was conducted in the gross anatomy laboratory at the University of Calgary.

SUBJECTS: Two 77-yr-old, unembalmed, post-rigor mortis, male cadavers were used.

INTERVENTIONS: The movements of vertebrae were investigated by using high-speed cinematography to record the movements of bone pins threaded into T10, T11 and T12 during spinal manipulative therapy to unembalmed post-rigor human cadavers. A single clinician delivered a series of posterior-to-anterior (p-to-a) thrusts to the right transverse process of either T10, T11 or T12, using a reinforced hypothenar contact. Relative p-to-a and lateral translations, as well as axial and sagittal rotations, in T10-T11 and T11-T12 were calculated. Corresponding p-to-a forces exerted by the clinician onto the cadaver were recorded using a pressure pad.

MAIN RESULTS: Significant relative movements were measured primarily between the targeted and immediately adjacent vertebrae during the thrusts. Vertebral pairs remained slightly 'hyper-extended' after the rapid thrusts to T11, when the p-to-a forces returned to preload levels.

CONCLUSIONS: These findings may be useful for the understanding of the deformation behavior of the vertebral column during therapeutic manipulation. A fully three-dimensional analysis of all six degrees of freedom, using a larger number of unembalmed cadavers, would be useful in clarifying the relationship between the externally applied forces and the observed relative movement patterns of the vertebrae.

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