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Vertebral artery atherosclerosis: a risk factor in the use of manipulative therapy?
1Faculty of Health and Social Care, University of the West of England, Bristol, UK. Jeanette.Mitchell@uwe.ac.uk
Background And Purpose:
Vertebrobasilar insufficiency, a direct result of compromised blood flow in the vertebrobasilar circulation, may be caused by stretching and/or compression of the vertebral arteries, particularly if superimposed on underlying atherosclerosis of the vessels. This is an important consideration when using manipulative therapy techniques. The aim of the present study was to investigate the incidence of atherosclerosis and to calculate the relative associated decrease in blood flow in the third and fourth parts of the vertebral artery, in a sample of the adult population.
Method:
A laboratory-based experimental investigation was used to study 362 vertebral arteries from embalmed adult cadavers that were routinely processed for light microscopic study. The incidence of each grade of atherosclerosis in the vessels was recorded. Atherosclerosis was classified as grades 0-5, where Grade 0 represented no atherosclerosis and Grade 5 a fully developed plaque occluding more than 75% of the vessel lumen. From mean measurements of 188 of these arteries, the estimated decrease in luminal cross-sectional area and the relative decrease in blood flow in the atherosclerotic vessels were calculated.
Results:
The highest incidence of atherosclerosis found was Grade 3 (third part of the vertebral artery (VA3): 42.0%; fourth part of the vertebral artery (VA4): 35.2%). An estimated decrease in artery luminal cross-sectional area to 6.2% of normal in Grade 5 atherosclerosis was found. Because blood flow is proportional to the fourth power of the vessel radius, relative decreases in blood flow in grades 1-5 atherosclerosis from 100% to 0% (with critical closing pressure in vessels), respectively, are likely to occur.
Conclusions:
These data suggest that, as significant numbers of the sample showed marked (Grade 3+) atherosclerosis, concomitant with decreased blood flow in the vertebral arteries, this population is at risk for developing vertebrobasilar insufficiency. Because other Western populations may be similarly at risk, particular care should be taken when considering the use of rotational manipulative therapy techniques in treatments of the cervical spine.