MD, PhD, FMedSci, FRSB, FRCP, FRCPEd.

Some people will probably think that I am obsessed with writing about the risk of chiropractic. True, I have published quite a bit on this subject, both in the peer-reviewed literature as well as on this blog – but not because I am obsessed; on this blog, I will re-visit the topic every time a relevant new piece of evidence becomes available because it is indisputably such an important subject. Writing about it might prevent harm.

So far, we know for sure that mild to moderate as well as serious complications, including deaths, do occur after chiropractic spinal manipulations, particularly those of the upper spine.  What we cannot say with absolute certainty is whether they are caused by the treatment or whether they happened coincidentally. Our knowledge in this area relies mostly on case-reports and surveys which, by their very nature, do not allow causal inferences. Therefore chiropractors have, in the past, been able to argue that a causal link remains unproven.

A brand-new blinded parallel group RCT might fill this gap in our knowledge and might reject or establish the notion of causality once and for all. The authors’ objective was to establish the frequency and severity of adverse effects from short term usual chiropractic treatment of the spine when compared to a sham treatment group. They thus conducted the first ever RCT  with the specific aim to examine the occurrence of adverse events resulting from chiropractic treatment. It was conducted across 12 chiropractic clinics in Perth, Western Australia. The participants comprised 183 adults, aged 20-85, with spinal pain. Ninety two participants received individualized care consistent with the chiropractors’ usual treatment approach; 91 participants received a sham intervention. Each participant received two treatment sessions.

Completed adverse questionnaires were returned by 94.5% of the participants after the first appointment and 91.3% after the second appointment. Thirty three per cent of the sham group and 42% of the usual care group reported at least one adverse event. Common adverse events were increased pain (sham 29%; usual care 36%), muscle stiffness (sham 29%; usual care 37%), headache (sham 17%; usual care 9%). The relative risk was not significant for either adverse event occurrence (RR = 1.24 95% CI 0.85 to 1.81); occurrence of severe adverse events (RR = 1.9; 95% CI 0.98 to 3.99); adverse event onset (RR = 0.16; 95% CI 0.02 to 1.34); or adverse event duration (RR = 1.13; 95% CI 0.59 to 2.18). No serious adverse events were reported.

The authors concluded that a substantial proportion of adverse events following chiropractic treatment may result from natural history variation and non-specific effects.

If we want to assess causality of effects, we have no better option than to conduct an RCT. It is the study design that can give us certainty, or at least near certainty – that is, if the RCT is rigorous and well-made. So, does this study reject or confirm causality? The disappointing truth is that it does neither.

Adverse events were clearly more frequent with real as compared to sham-treatment. Yet the difference failed to be statistically significant. Why? There are at least two possibilities: either there was no true difference and the numerically different percentages are a mere fluke; or there was a true difference but the sample size was too small to prove it.

My money is on the second option. The number of patients was, in my view, way too small for demonstrating differences in frequencies of adverse effects. This applies to the adverse effects noted, but also, and more importantly, to the ones not noted.

The authors state that no serious adverse effects were observed. With less that 200 patients participating, it would have been most amazing to see a case of arterial dissection or stroke. From all we currently know, such events are quite rare and occur perhaps in one of 10 000 patients or even less often. This means that one would require a trial of several hundred thousand patients to note just a few of such events, and an RCT with several million patients to see a difference between real and sham treatment. It seems likely that such an undertaking will never be affordable.

So, what does this new study tell us? In my view, it is strong evidence to suggest a causal kink between chiropractic treatment and mild to moderate adverse effects. I dose not prove it, but merely suggests it – yet I am fairly sure that chiropractors, once again, will not agree with me.

33 Responses to Evidence for a causal link between chiropractic treatment and adverse effects

  • Thanks for being so clear with the bold writing. I could not miss that time. Cheers.

  • In the development of conventional medicines RCTs are universally acknowledged to be inadequate for fully assessing safety. Hence post-marketing surveillance is always required. For this reason you are quite right that this study would have virtually no chance of detecting very serious adverse events such as cerebral artery dissection. I am not sure what we can infer regarding the non-significant excess of less serious AEs in this study, and the potential for life threatening ones. My view is that, with the benefits of chiropractic so minimal, and confined to low back pain, the risk can’t be justified.

    • Les Rose wrote: “My view is that, with the benefits of chiropractic so minimal, and confined to low back pain, the risk can’t be justified.”

      I think that’s the bottom line. In support of it, it’s worth remembering that although chiropractic adverse event reporting systems are apparently non-existent in the U.S. due to a loophole, and in the UK the Chiropractic Patient Incident Report and Learning System (CPIRLS) is hugely under-utilised, reports of deaths after chiropractic treatment are still “about three times the number of deaths from trovafloxacin, an excellent antibiotic abandoned in the U.S. as too dangerous”…
      http://www.sciencebasedmedicine.org/compare-and-contrast/

      • Hey Blue Wode….why not use your real name????…….funny how you so casually pull out a figure of “three times” without a shred of evidence. You do realise that the number of adverse reactions and deaths due to persons taking NASAIDS for musculoskeletal pain FAR exceed any risk a Chiro puts patients through.

        You must be a Physio….probably a struggling one at that.

        • …and did you know that NASIDs actually do work?
          so their risk/benefit balance might be positive when used properly.
          do you think the same applies to chiro SMT? and if yes, can you show me the evidence, please?

          • David Sparavec wrote: “…funny how you so casually pull out a figure of “three times” without a shred of evidence.”

            Didn’t you read the link I provided? It said:

            Quote:
            “…published recently was Deaths after chiropractic: a review of published cases.
            Twenty six fatalities were published in the medical literature and many more might have remained unpublished. The alleged pathology usually was a vascular accident involving the dissection of a vertebral artery. That is about three times the number of deaths from trovafloxacin, an excellent antibiotic that we abandoned in the U.S. as too dangerous.”
            http://www.sciencebasedmedicine.org/compare-and-contrast/

            I’m sure the author of that piece, Mark Crislip, would be happy to provide you with any data you request.

            David Sparavec wrote: “You do realise that the number of adverse reactions and deaths due to persons taking NASAIDS for musculoskeletal pain FAR exceed any risk a Chiro puts patients through.”

            A poor argument. For a true comparison of NSAIDs v. chiropractic spinal manipulation one would have to take into account the list of factors itemised at the end of the first section in this link:
            http://www.chirobase.org/18CND/03/03-03.html

            In essence, NSAIDs work (so have a favourable risk/benefit ratio); they are used by a vastly greater population; they carry Patient Information Leaflets (which patients may choose not follow, and thus experience adverse events); and they are subject to post-marketing surveillance. By comparison, chiropractic may not work beyond non-specific effects, is used by a tiny percentage of the population, fails greatly when it comes to informed consent procedures, and doesn’t have any reliable adverse events monitoring in place.

        • David Sparavec said:

          Hey Blue Wode….why not use your real name????

          Why? What difference does it make what name he uses?

  • Man Ther. 2010 Aug;15(4):355-63. doi: 10.1016/j.math.2009.12.006. Epub 2010 Jan 22.
    Adverse events and manual therapy: a systematic review.
    Carnes D, Mars TS, Mullinger B, Froud R, Underwood M.
    Source

    Barts and The London School of Medicine and Dentistry, Centre for Health Sciences, 2 Newark St, London E1 2AT, UK. d.carnes@qmul.ac.uk
    Abstract
    OBJECTIVE:

    To explore the incidence and risk of adverse events with manual therapies.
    METHOD:

    The main health electronic databases, plus those specific to allied medicine and manual therapy, were searched. Our inclusion criteria were: manual therapies only; administered by regulated therapists; a clearly described intervention; adverse events reported. We performed a meta-analysis using incident estimates of proportions and random effects models.
    RESULTS:

    Eight prospective cohort studies and 31 manual therapy RCTs were accepted. The incidence estimate of proportions for minor or moderate transient adverse events after manual therapy was approximately 41% (CI 95% 17-68%) in the cohort studies and 22% (CI 95% 11.1-36.2%) in the RCTs; for major adverse events approximately 0.13%. The pooled relative risk (RR) for experiencing adverse events with exercise, or with sham/passive/control interventions compared to manual therapy was similar, but for drug therapies greater (RR 0.05, CI 95% 0.01-0.20) and less with usual care (RR 1.91, CI 95% 1.39-2.64).
    CONCLUSIONS:

    The risk of major adverse events with manual therapy is low, but around half manual therapy patients may experience minor to moderate adverse events after treatment. The relative risk of adverse events appears greater with drug therapy but less with usual care.

    • From the study cited by Bob about the incidence and risk of adverse events with manual therapies:

      Quote
      “…classifying manual therapies was difficult because they are often complex multiple interventions and to truly ascribe causality was impossible in this study.”
      http://www.osteopathy.org.uk/uploads/adverse_events_and_manual_therapy_article.pdf

      With regard to chiropractic (the topic of this post – not manual therapies), when you balance its little demonstrable benefit against the fact that there are no reliable reporting systems in place to record adverse events following treatment, and that reports of life-threatening complications seem to be increasing (e.g. according to the U.S. National Practitioner Data Bank, between September 1, 1990 and January 29, 2012, a total of 5,796 chiropractic medical malpractice reports were filed with common reasons for the lawsuits being strokes as well as other injuries), I can’t see how chiropractic can be recommended for any condition.

      • @ Blue wode

        Chiropractic is a manual therapy, so it is relevant to the topic of the post. My interpretation of the Carnes et al study is that adverse events are common to all manual therapies (chiropractic, osteopathy, physiotherapy, massage therapy etc.) Considering none of these therapies are any better than each other for the treatment of musculoskeletal conditions, i would say the conclusion could be that no one should have these forms of treatment – would you agree / disagree and why?
        The article also points out that across all manual therapies there are poor reporting processes for adverse events when doing clinical research.
        The following article highlights the issues around adverse event reporting, which i think can be applied to all professions that use manual therapies.

        http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CGgQFjAI&url=http%3A%2F%2Fwww.jospt.org%2Fmembers%2Fgetfile.asp%3Fid%3D4870&ei=_EnNUerrIMKw0QXF4YDICw&usg=AFQjCNEzVC-nkqRBt4tnO70Zmgn5OEb80Q&sig2=r9Zb4DrMDvzB_6zVlsoF3w

        Can you point me towards a reliable adverse event reporting system for each of the professions.

        Finally, in the following statement made by yourself :

        “that reports of life-threatening complications seem to be increasing (e.g. according to the U.S. National Practitioner Data Bank, between September 1, 1990 and January 29, 2012, a total of 5,796 chiropractic medical malpractice reports were filed with common reasons for the lawsuits being strokes as well as other injuries)”

        What is the rate of increase? How does that compare to other professions who use manual therapies?

        All the best : )

        • if it is true that they are all similarly [in]effective, the logical conclusion is to avoid chiro which is associated with more AEs than the other and use massage/physio which is at the other end of this spectrum.

          • Bob wrote: “Considering none of these therapies are any better than each other for the treatment of musculoskeletal conditions, i would say the conclusion could be that no one should have these forms of treatment – would you agree / disagree and why?”

            If someone chooses one of these forms of treatment (assuming they have been fully informed about it), then chiropractic should be the one they avoid due to it not only having the highest number of adverse events, but also because it is mired in subluxation-based quackery.

            Bob wrote: “Can you point me towards a reliable adverse event reporting system for each of the professions.”

            No, but going by reports in the medical literature, chiropractic is the worst of all the manual therapies when it comes to severe complications.

            Bob wrote: “ Finally, in the following statement made by yourself : “that reports of life-threatening complications seem to be increasing (e.g. according to the U.S. National Practitioner Data Bank, between September 1, 1990 and January 29, 2012, a total of 5,796 chiropractic medical malpractice reports were filed with common reasons for the lawsuits being strokes as well as other injuries)” What is the rate of increase?”

            I have no idea, but, as I said, reports of life-threatening complications following chiropractic interventions *seem* to be increasing. For example, take the 5,796 U.S. chiropractic medical malpractice reports between 1990 and 2012 in which common reasons for the lawsuits were strokes (as well as other injuries), and compare them with the (mainly) medical literature reports between 1934 to 2001:
            http://web.archive.org/web/20060924185308/http://www.chirovictims.org.uk/images/Detailed%20database%20high%20neck%20manipulation%20reports.doc

            The chiropractic adverse event reports in the above link (relating to neck manipulation only) number c.160.

            That, to me, indicates that adverse events do seem to be rising. Also, as far as I can see, the complications associated with chiropractors in that link comprise around 50% of all the practitioners described – something which appears to be somewhat compatible with Fig.2 in this 1999 paper:
            http://ptjournal.apta.org/content/79/1/50.full

            Fig.1 is also interesting.

  • Very funny Ed. One moment you are “scientific”, then next moment you extrapolate from rubbish to whatever point you are trying to promote.

    Also, if VB dissections due to mobs/manips were “1 in 10,000 patients or less”, my PI insurance would be 10 times what it is right now. Have you done the maths on how many cervical spine mobs/manips are done on an annual basis. I have….in Australia at least. I`m sure that if your “guestimate” figure was even remotely correct, some insurance actuary would have picked it up by now and capitalised on it. And yes Ed, the actuaries use all resources known…including Cochrane.

    • oh dear; here is the old chestnut again!
      first, I did not say that the incidence was 1 in 10 000.
      second, insurance claims and incidence are not remotely the same – ever heard of a phenomenon called UNDER-REPORTING?
      [if you call me ed, can I call you DA?]

      • @ Edzard

        You are correct in stating that you did not say that the incidence was 1 in 10 000. What you did write was “From all we currently know, such events (stroke or arterial dissection) are quite rare and occur perhaps in one of 10 000 patients or even less often”

        What is the incidence rate for this? Is it possible that it is greater than one in 10,000 patients too?

        • I think there are no reliable incidence figures because of under-reporting and other problems. estimates range from 1:10 00 to 1: 3ooo ooo.

  • When the title of your blog post says “strong evidence” I expect to read about strong evidence, not a statistically inconclusive study. You should probably reserve phrases like “strong evidence” for when more persuasive studies come in. I do not mean to rubbish your claims, and I have no connection with chiropractic; I’m just saying that you run a risk of coming across as stretching your opinions beyond the evidence.

  • Edzard,

    Chiropractic is ineffective treatment for any condition but causing much harm in any condition. Is Chiropractic like syanide pill? Poison? Did I get it right? Very evidence based darling.

    Walter
    M.D., D.O., P.T.

    • Walter Lee said:

      Chiropractic is ineffective treatment for any condition but causing much harm in any condition.

      The first part of your sentence is pretty much correct, but I don’t know where you got the rest from.

      Is Chiropractic like syanide [sic] pill? Poison? Did I get it right?

      No, you didn’t.

      If you have good evidence to the contrary, please feel free to present it.

  • An interesting article on this topic:

    http://www.medscape.com/viewarticle/809688

    “Hufnagel et al.:

    … analyzed the clinical course and neuroradiological findings of ten patients aged 27–46 years, with ischemic stroke secondary to vertebral artery dissection (VAD; n = 8) or internal carotid artery dissection (CAD; n = 2), all following chiropractic manipulation of the cervical spine.[30]

    However, none of the ten cases above described by Hufnagel, had a chiropractor perform the SMT. That is, seven cases had the SMT from an orthopaedic specialist and three from a physiotherapist.”

    It should always be taken into consideration WHO is doing the SMT. Although the orthopaedic specialists and physios were said to be using “chiropractic manipulation”, their training in SMT is paltry compared the Chiropractor, who’s training takes years and who may use it as his/her primary treatment modality.

  • To add to my above comment:

    It’s an old argument, but any tool/device/therapy in the hands of a practitioner poorly trained to use it, may be more dangerous/carry higher risks. Can you imagine a Chiropractor attempting a knee reconstruction?

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