Preliminary research conducted at the University of Calvary in Alberta, Canada suggests that chiropractic adjustments place far less strain on the vertebral artery than critics of chiropractic have speculated.

The researchers used a specialized ultrasound technique to measure strains in the human vertebral artery (VA) within the cervical transverse foramina of a cadaver. Measurements were taken during cervical spine range of motion testing, vertebrobasilar insufficiency testing and chiropractic adjustments.

Strain to the VA was lower during the adjustment than during passive range of motion rotation testing. These results were consisted for 2 chiropractors each repeating the adjustments and testing 3 times.

The study’s authors explain that “elongation and shortening of adjacent VA segments were observed simultaneously and could not be explained with a simple model of neck movement. We hypothesized that they were caused by variations in the location and stiffness of the VA fascial attachments to the vertebral foramina and by coupled movements of the cervical vertebrae.”

“Although general conclusions should not be drawn from these preliminary results, the findings of this study suggest that textbook mechanics of the VA may not hold, that VA strains may not be predictable from neck movements alone, and that fascial connections within the transverse foramina and coupled vertebra movements may play a crucial role in VA mechanics during neck manipulation,” explain the researchers. “Furthermore, the engineering strains during cervical spinal manipulations were lower than those obtained during range of motion testing, suggesting that neck manipulations impart stretches on the VA that are well within the normal physiologic range of neck motion”


JMPT – May 2010;33:273-78.

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