Comments on: Vertebral artery strains during high-speed, low amplitude cervical spinal manipulation.

By: Adam M Schotzko

Adam M Schotzko — Tue, 11 Dec 2012 17:04:57 +0000

Good article to hand to anybody that says chiropractors cause strokes. I will be using this in the practice. Thanks!

By: Troy Holder, D.C.

Troy Holder, D.C. — Fri, 30 Nov 2012 16:49:27 +0000

Whoops, my bad. Thanks John!

Still great data and definitely more insightful for future studies as well. Gotta love the progress we’ve made in research.

By: John

John — Thu, 29 Nov 2012 17:13:48 +0000

It looks as if they used data from the original experiment in 2002 and also from a more comprehensive study in 2010. Both studies were performed on cadavers.

As you can see in the following excerpt from the 2012 study, forces during manipulation are significantly less than those found during range of motion testing.

“An example of raw data of VA length changes for a full flexion range of motion test and a diversified lateral/rotational SMT from the same subject illustrates many typically observed results:

(i) The length change of the VA during SMT is much smaller than that observed during the range of motion testing;

(ii) the length of the VA throughout the entire SMT is smaller than the length in the neutral head and neck position (about 15.4 mm – as seen at the very beginning of the range of motion test which started at the neutral length); and

(iii) the rate of change in VA length (given by the slope of the distance-time traces), is similar for the SMT and range of motion testing, even though the range of motion testing was performed very slowly (a full cycle took approximately 4s, while the displayed SMT took 150 ms).”

By: Frank M. Painter, D.C.

Frank M. Painter, D.C. — Sat, 24 Nov 2012 21:40:06 +0000

Hi Dr. Holder Actually, John posted this particular abstract. It is derivative of Herzog's original 2 articles, the first one (the pre-publication announcement) is the one I posted just before John's post: http://www.chiro.org/wordpress/?p=13220 Their testing suggests that SMT generates only 26% of the strain associated with normal rotation to end-point, and is "an order of magnitude" (or 1 thousand percent less) less than the strain associated with failure of the artery.

This is their seminal article: Internal Forces Sustained by the Vertebral Artery During Spinal Manipulative Therapy J Manipulative Physiol Ther 2002 (Oct); 25 (8): 504–510

By: Troy Holder, D.C.

Troy Holder, D.C. — Sat, 24 Nov 2012 18:07:10 +0000

“VA strains obtained during SMT are significantly smaller than those obtained during diagnostic and range of motion testing, and are much smaller than failure strains. We conclude from this work that cervical SMT performed by trained clinicians does not appear to place undue strain on VA, and thus does not seem to be a factor in vertebro-basilar injuries.”

Well, I think that pretty much says it. Adjustments are no more strain on the VA than diagnostic and range of motion testing! This study is fantastic and will be a great addition to the other studies we already have supporting a lack of causitive evidence for CMT causing VA dissections and stroke. Don’t get me wrong, the risk is obviously still there. Anytime you put a force into someone’s body you can still cause harm, just as you can cause good. However, studies like this really strengthen your voice when talking with others about the risks of CMT (or lack thereof).

Thanks for the post Dr. Painter!