How Safe Is Chiropractic? This area is a little technical. I don't want to paraphrase it because it waters it down. Suffice to say feel free to read it.
The most sensational adverse event with a supposed link to chiropractic spinal manipulation
is vertebral artery dissection. Allegations of vertebral artery dissection caused by chiropractic spinal manipulation have appeared in the published literature for decades. However, recent large critical reviews of the topic have appeared in the scientific literature, and they question the causation between cervical spine manipulation and cervical artery dissection. Some of this literature is reviewed below.
In 2008, Dr. David Cassidy and colleagues published the most comprehensive study at that
time pertaining to the risk of vertebral artery dissection as related to chiropractic cervical spine
manipulation. The article was published in the journal Spine, and titled (11):
Risk of Vertebrobasilar Stroke and Chiropractic Care:
Results of a Population‐Based Case‐Control and Case‐Crossover Study
This study included all residents of Ontario, CAN, over a period of 9 years, amounting to
109,020,875 person years of observation. Associations between chiropractic visits and vertebral
artery dissection versus primary care physician (PCP) visits and vertebral artery dissection were
The authors noted:
“We found no evidence of excess risk of vertebral artery stroke associated with chiropractic care.”
“Neck pain and headache are common symptoms of vertebral artery dissection, which commonly precedes vertebral artery stroke.” “The increased risks of vertebral artery stroke associated with chiropractic and primary care physicians visits is likely due to patients with headache and neck pain from vertebral
artery dissection seeking care before their stroke.”
“Because patients with vertebrobasilar artery
dissection commonly present with headache and neck pain, it is possible that patients seek chiropractic care for these symptoms and that the subsequent vertebral artery stroke occurs spontaneously, implying that the association between chiropractic care and vertebral artery stroke is not causal.”
“Our results suggest that the association between chiropractic care and vertebral artery stroke found in previous studies is likely explained by presenting symptoms attributable to vertebral artery dissection.”
In January of 2011, the Journal of Manipulative and Physiological Therapeutics published a
population‐based case series using administrative health care records of all Ontario, CAN, residents
hospitalized with vertebral artery stroke between April 1, 1993, and March 31, 2002, titled (12):
A Population‐based Case‐series of Ontario Patients who Develop a Vertebrobasilar Artery
Stroke After Seeing a Chiropractor
These authors note:
“The current evidence suggests that association between chiropractic care and
vertebrobasilar artery (VBA) stroke is not causal. Rather, recent epidemiological studies
suggest that it is coincidental and reflects the natural history of the disorder.”
“Because neck pain and headaches are symptoms that commonly precede the onset of a
VBA stroke, these patients might seek chiropractic care while their stroke is in evolution.”
Also in January 2011, The Open Neurology Journal published an “open access” editorial by
Drs. Dean Smith and Gregory Cramer, titled (13):
“Spinal Manipulation is Not an Emerging Risk Factor for Stroke Nor is it Major Head/Neck
Trauma. Don't Just Read the Abstract!”
Dean L. Smith is Clinical Faculty, Department of Kinesiology and Health, Miami University,
Oxford, Ohio, and Gregory D. Cramer is Professor and Dean of Research, National University of
Health Sciences, Lombard, Illinois. Their editorial includes:
We would like to address two points in this letter:
1) The current best‐evidence indicates no causal relationship between spinal
manipulation (‘chiropractic maneuver’ in the paper) and vertebrobasilar artery
(VBA) stroke, and,
2) Spinal manipulation or ‘chiropractic maneuvers’ are not major head/neck trauma
as suggested in abstract of this article.
“First, evidence is mounting that the association between spinal manipulation and stroke
is coincidental rather than causal and reflects the natural history of the disorder.”
“The largest population‐based study to date was conducted by Cassidy et al. and included
all vertebrobasilar artery (VBA) strokes in Ontario, Canada over a period of 9 years. The
authors found no evidence of excess risk (i.e. no risk) of VBA stroke associated with
“The prevailing hypothesis is that patients with vertebral artery dissections often have
initial symptoms that cause them to seek care from a chiropractic or medical physician
and the stroke is independent of their visit.”
“The latest scientific evidence questions whether spinal manipulation is a risk factor at all
for cervical artery dissection.”
“Chiropractic spinal manipulations may very well be a demerging risk factor for stroke
since there may not be any risk.”
“The evidence, albeit limited to date, suggests that spinal manipulative treatments
produce stretches of the vertebral artery that are much smaller than those that are
produced during normal everyday movements, and thus they appear harmless.”
“Spinal manipulations delivered by licensed chiropractors do not fulfill the criteria for
major trauma and should not be considered major trauma.”
The biomechanics of cervical spine manipulation and vertebral artery stress is important.
The world leader on this type of biomechanical assessment is Walter Herzog, PhD, from the
University of Calgary, CAN. In 2012, Dr. Herzog and colleagues published a study in the Journal of
Electromyography and Kinesiology titled (14):
Vertebral Artery Strains During High‐speed,
Low Amplitude Cervical Spinal Manipulation
Dr. Herzog notes that spinal manipulative therapy (SMT) is recognized as an effective
treatment modality for many back, neck and musculoskeletal problems. Yet, one of the major issues
of the use of SMT is its safety, especially with regards to neck manipulation and the risk of stroke. It
has been assumed [wrongly as per this study] that the vertebral artery (VA) experiences
considerable stretch during extension and rotation of the neck, which may lead to occlusions and
damage to the VA, predisposing the patient to stroke. Therefore, this study presents the first ever
data on the mechanics between C2/C1 during cervical SMT performed by chiropractic clinicians.
The authors compared the results of human VA strains during high‐speed, low‐amplitude
SMTs administered by qualified chiropractic clinicians and compared them to the strains
encountered during full range of motion (ROM) tests. They used a total of 3,034 segment strains
obtained during SMTs and 2,380 segment strains obtained during full ROM testing, making this is an
extensive study. Dr. Herzog and colleagues conclude:
“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‐
“In summary, the maximal strain values for the ROM testing at each segmental level were
always greater than the corresponding strain values for the SMTs, suggesting that neck
SMTs impose less stretch than turning your head, or extending your neck while looking up
at the sky.”
“Therefore, based on the mechanical tests performed here, one should be able to
conclude that stretching of VA during neck SMTs does not cause any damage of the VAs.”
“The VA is never really strained during spinal manipulative treatments but that the VA is
merely taking up slack as the neck and head are moved during SMT, but that there is no
stress and thus no possibility for microstructural damage.”
“The results from this study demonstrate that average and maximal VA strains during
high‐speed low‐amplitude cervical spinal manipulation are substantially less than the
strains that can be achieved during ROM testing for all vertebral artery segments.”
“We conclude that cervical spinal manipulations, as tested here, are safe from a
mechanical point of view for normal, healthy VA.”
In 2015, a study was published in the journal Chiropractic & Manual Therapies, and titled
Chiropractic Care and the Risk of Vertebrobasilar Stroke:
Results of a Case–control Study in U.S. Commercial
and Medicare Advantage Populations
The main purpose of this study was to replicate the case–control epidemiological design
study published by Cassidy, et al. in 2008 (11), and to investigate the association between
chiropractic care and vertebral artery stroke; and compare it to the association between recent
primary care physician (PCP) care and vertebral artery stroke. The authors assessed commercially
insured and Medicare Advantage (MA) health plan members in the U.S. The data set included
health plan members located in 49 of 50 states (excluded North Dakota) and encompassed national
health plan data for 35,726,224 commercial and 3,188,825 MA members. Hence, this study looked
at approximately 39 million people, making this the largest case–control study to investigate the
association between chiropractic manipulation and vertebral artery stroke. These authors
“There was no association between chiropractic visits and VBA stroke found for the
overall sample, or for samples stratified by age.”
“We found no significant association between exposure to chiropractic care and the risk
of vertebral artery stroke. We conclude that manipulation is an unlikely cause of vertebral
“Our results increase confidence in the findings of a previous study , which concluded
there was no excess risk of vertebral artery stroke associated with chiropractic care
compared to primary care.”
In 2016, a study from the Department of Neurosurgery, Penn State Hershey Medical Center,
and the Department of Neurosurgery, Johns Hopkins University School of Medicine, was published
in the journal Cureus, and titled (16):
Systematic Review and Meta‐analysis of Chiropractic Care
and Cervical Artery Dissection:
No Evidence for Causation
The authors note that case reports and case control studies have suggested an association
between chiropractic neck manipulation and cervical artery dissection (CAD), but a causal
relationship has not been established. These authors evaluated the evidence related to this topic by
performing a systematic review and meta‐analysis of published data on chiropractic manipulation
and cervical artery dissection (CAD). These authors state:
“We found no evidence for a causal link between chiropractic care and CAD. This is a
significant finding because belief in a causal link is not uncommon, and such a belief may
have significant adverse effects such as numerous episodes of litigation.”
“In spite of the very weak data supporting an association between chiropractic neck
manipulation and CAD, and even more modest data supporting a causal association, such
a relationship is assumed by many clinicians. In fact, this idea seems to enjoy the status of
“Excellent peer reviewed publications frequently contain statements asserting a causal
relationship between cervical manipulation and CAD. We suggest that physicians should
exercise caution in ascribing causation to associations in the absence of adequate and
reliable data. Medical history offers many examples of relationships that were initially
falsely assumed to be causal, and the relationship between CAD and chiropractic neck
manipulation may need to be added to this list.”
“There is no convincing evidence to support a causal link, and unfounded belief in
causation may have dire consequences.”
“The quality of the published literature on the relationship between chiropractic
manipulation and CAD is very low. Our analysis shows a small association between
chiropractic neck manipulation and cervical artery dissection. This relationship may be
explained by the high risk of bias and confounding in the available studies, and in
particular by the known association of neck pain with CAD and with chiropractic
“The association between a chiropractor visit and dissection may be explained by”
understanding that “patients with cervical artery dissection more frequently have
headache and neck pain” and understanding that “patients with headache and neck pain
more frequently visit chiropractors.”
“Because (on average) patients with headache and neck pain visit chiropractors more
frequently, and patients with cervical artery dissection more frequently have headache
and neck pain, it appears that those who visit chiropractors have more cervical artery
The data presented here indicates that medical care is incredibly dangerous. The authors estimate that hospital errors kill 251,000 Americans yearly (the 3rd leading cause of yearly US deaths), and hospital non‐error “fallout” kills an additional 106,000 Americans yearly (the 4th ‐6th leading cause of yearly US deaths). These numbers total 357,000 yearly hospital medical deaths. It is reasonable to assume that a similar number of deaths occur outside of the hospital setting (nursing homes, extended care facilities, at home, etc.).
In contrast, chiropractic spinal manipulation, even to the cervical spine, is incredibly safe. In
a typical year there are zero reported deaths linked to chiropractic care, and if one such death is
alleged it tends to make sensational news. Chiropractic students and chiropractors are extensively trained in spinal anatomy and spinal biomechanics. They are also extensively trained in the science and art of spinal adjusting (specific directional manipulation). They are taught to avoid injury risk, and to recognize serious events that are in progress, making the appropriate referral. Even the use of prescription NSAIDs for pain results in the deaths of 16,500 Americans yearly (the 15th leading cause of yearly US deaths). The concern is that in the randomized clinical trial reviewed, chiropractic spinal adjusting was better than five times more effective in alleviating chronic back and neck pain as compared to these drugs, and this was achieved with no side effects. Importantly, the one‐year follow‐up to this study showed the benefits of chiropractic to be stable.(17). Chiro-Trust.org
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Chiro-Trust.orgturpis egestas. Sed commodo suscipit quam ut fermentum.