Variability of Doctors Delivering Two Hand High Velocity Manual Forces to Thoracic Spine of a Mannequin

M.R. Gudavalli (USA)


Biomechanics, Chiropractic Manipulation, Mannequin, The Spine, Loads


The objective of this study was to characterize the force time profiles of posterior-to-anterior thoracic high velocity low-amplitude spinal manipulations (HVLA SM) using two hand of different chiropractors performed on a mannequin several times over a week. A bioengineered mannequin with artificial discs, muscles, ligaments, and skin was developed as a research and teaching tool to train students and new clinicians. Three experienced clinicians performed posterior-to-anterior thoracic two hand contact HVLA SM on the mannequin at three levels (upper, middle, and lower thoracic regions). Each doctor delivered six spinal manipulations over the course of 1 week. The doctors were blinded to the other two doctors’ thrusts and also the results of the study. Force-time histories were measured with a three-dimensional force transducer placed under the doctor’s hand and recorded using Motion Monitor software. Using MathCAD software, we extracted the biomechanical characteristics: magnitude of peak load, magnitude of preload, duration of the thrust, duration of the manipulation, and rate of loading. Results were analyzed for the differences between doctors, differences between the thoracic levels, and the consistency over the six sessions delivered over a week. We observed differences in the biomechanical characteristics between the three doctors. Variability as observed by the coefficient of variations demonstrated 4 10 percent on durations, 13-17 % on rate of loading, 15 21% on preload values, 10-14% on peak load magnitudes, and very high variability on the shear forces.

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