Let’s Talk Spinal Manipulation (Thrust, Grade 5, or whatever else you wanna call it)…

Spinal manipulation is an intervention we commonly employ as Physical Therapists.   We have several names for it (because of inter-professional turf wars) and loads of RCTs (supposedly) supporting its use.   In addition, there are loads of continuing education courses and certifications, each claiming to teach you (more) effective ways to manipulate the spine.  For gosh sakes,  I get a new pamphlet every other day.  But in all of this hype, what do we truly know about the effects of spinal manipulation?  Can we truly design one more RCT to measure its effectiveness if we barely know the potential physiological mechanisms behind its effectiveness(ok I stole this idea from Jim Meadows at the AAOMPT conference this year, but it is just so good)?  Should we simply employ a rule, when we don’t understand the process?  I am not sure…but lets dig a bit deeper.  Let’s attempt to understand the complexity of spinal manipulation.
Basic Anatomy/Physiology/and other good stuff:
I would like to discuss all of the potential anatomy and physiology which could be affected with a spinal manipulation.  For this, I am going to use a description of spinal manipulation as described by Flynn et al in the derivation of a lumbar CPR.1  I don’t want to pick on them, this is simply a widely read study amongst PTs, and the description is of a very basic spinal manipulation many of us employ.  In the study, they state:

At the first session, the therapist performed a spinalmanipulation technique with the patient supine. The therapist stood opposite the side to be manipulated. The patient was passively side-bent away from the therapist. The therapist passively rotated the patient and then delivered a quick posterior and inferior thrust through the anterior superior iliac spine.

Now Let’s Think: The human body has layers upon layers of tissue.  For whatever reason, when many of us learn “spinal” manipulation, there is a HUGE emphasis on what happens at the level of the spine.  But in the case above, what other organs may be affected?  For example, where’s the love for the skin?  The skin is our largest organ, comprised of layers of ectodermal tissue.  It gets “twisted” and “stretched” during a “spinal” manipulation.  So could we change the name to “skin manipulation”?
The skin is comprised of the epidermis, dermis, papillary region, reticular region and subcutaneous layers.   The epidermis is the outer layer, which protects the body.  It is our bodies armor.   Some of us decorate it.


  Random thought about the epidermis: I remember my anatomy professor once discussing the ridiculousness of body creams which claim to “penetrate” deep into the body, when they likely don’t even make it past this barrier.
Anyways, this layer is actually subdivided into a bunch more “stratum” layers which have individual roles.
Once you get past all of the epidermal layers, you reach the dermis.  This part of the skin makes it “elastic” and “strong”. It is also comprised of a ton of little nerve endings which help us sense stimuli.
These nerve endings, also known as mechanoreceptors, do several things:
Pacinian corpuscles: sense vibration and pressure
Meissners corpuscles: sense light touch (they have the lowest threshold in sensing stimuli)
Merkel’s discs: provide touch and pressure information to the brain
Ruffini Corpuscles: kinesthetic sense
So regressing back to the description given for a spinal manipulation, the authors stated, “The patient was passively side-bent away from the therapist. The therapist passively rotated the patient and then delivered a quick posterior and inferior thrust through the anterior superior iliac spine.”  This darn well sounds like the skin was “stretched”.  It also sounds like the skin was touched.  It sounds like the above nerve fibers were stimulated.   Could they be the reason why spinal manipulation appears to work (note: while it does appear spinal manipulation is effective, it is likely just as effective as non-thrusting techniques.2 Maybe this is why…)?
Anyways, let’s say the variable of the skin is non-existent in spinal manipulation (far-fetched but let’s say it happens).  The next layer of tissue are subcutaneous (ie. beneath the skin).  Unlike skin, which is “ectodermal” in origin, this layer of tissue originates from “mesoderm”.   Its main use: fat storage.  It keeps you warm.   But within this layer (which the fascia crew loves) are more nerves and free-nerve endings.  But let’s say these aren’t stimulated either…
Once we get past all of this good stuff, we have layers of muscular tissue that receives and transmits afferent and efferent information from the nervous system.   The “afferent leg” takes sensory information from the level of the muscle, all the way up to the command center (ie. the brain).   This information is generally from proprioceptors and muscle spindles, conveying the degree of stretch/length of the muscle, as well as where it is in space.  So when considering spinal manipulation, do you think position sense is potentially altered during a “spinal” manipulation?  How about muscle length?
So if we can also ignore the effects of muscle, we arrive to the bones, which many have fought long and hard to defend as holding the key to answering the mechanism questions.   Many argue alignment and/or faulty mechanics, while some talk about disc integrity and fluid… but wait a minute… what about all of the other “stuff” I just described above?  Do the bones/disc move in isolation?
Now that we have overwhelmed ourselves with all of the internal variables to consider, we must also be cognoscente and account for the potential of external influences over effects.  We must consider all of the noise.  We must consider the clinical environment, therapeutic alliance and prosody of our speech.  We must consider everything.
I hate to say this , but spinal manipulation doesn’t impress me any more than our other manual techniques.  This is coming from someone who has completed a manual certification and an AAOMPT fellowship.  I know how to manipulate.  But I am very doubtful it is more effective than lower grade mobilizations (unless the patient is convinced it will be—which then acts likely as a placebo).
As we begin to critically examine what is happening within the things we do, we will begin to understand the complexity of the human experience and likely find that all these inputs, simply work the same way.
What are your thoughts?
1. Flynn T, Fritz J, et al. A clinical prediction rule for classifying patients with low back pain who demonstrate short-term improvement with spinal manipulation. Spine 2002; 27: 2835-2843.
2.Cook CE, et al., Can a within/between-session change in pain during reassessment predict outcome using a manual therapy intervention in patients with mechanical low back pain?, Manual Therapy (2012), doi:10.1016/j.math.2012.02.020

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  • I think you nailed it pretty well Joe. Manipulation is simply a skill we learned, at great financial cost for many of us, which exist mainly to give credence to the segmental dysfunction biomechanical rationnal. Once that rationnal is gone, manipulation sort of looses most of its meaning and becomes just like any other manual intervention. Yet, for some patients it could be more effective as a treatment modality because some patients might still be on board with the segmental dysfunction rationnals. Understandably so, given the plethora of professionnals still using the manipulation in this fashion and explaining the patient’s pain (to the pt) in such a manner.
    Thus, thrusts are still there for a while. Too many of us PT and our fellow pathes and practors need this to endure to give a sense of necessity to our services. Given that the structural cause for back pain is so entrenched in our collective system of belief just as it is for the patients, it is not hard to sell this modality and have a highly positive expectation. And with the ritual surrounding its application you have a recipe for placebo success.
    But, lets go on and fund (waste?) some more research on its mechanism so we know exactly how it “works”. In the end, Nothing will really change. I mean, people still buy homeopathic medicine despite the obvious…

    Frédéric Wellens, pht January 5, 2014 11:16 am Reply
  • Manual therapy by any other name……at least the PT is touching, examining and working with pt. Much PT done is dertimined before the pt even gets to the PT clinic.

    Bruce Wilk January 5, 2014 12:13 pm Reply
  • Awesome post, I would additionally submit, that passive movement is actually takes active participation on the part of the patient. The patient must suppress its own reflexive tendency to maintain the position that it is in. If you take any segment of the body and perturb it you get a stretch reflex. This stretch reflex is the bodies tendency to maintain whatever static position it is in. Therefore, the manual therapist must successfully create a context that allows for this cortical induced inhibition of lower centers. This is no small thing. So what appears as ostensibly passive to the treating therapist is actually an incredibly active process on the part of the patient.

    ericpt January 5, 2014 1:59 pm Reply
  • Good article. How specific a manual technique is from a physiological perspective is more often less evidence based than the treatment outcome. In the clinic the total care of practioner and the expectation of patient is relevant for the treatment result.

    David Aston January 5, 2014 5:38 pm Reply
  • Reblogged this on Chiroresearcher and commented:
    Interesting thoughts on the effects that spinal manipulation might have on skin and muscle. Good point that many often think only of the vertebrae regarding the mechanism of manipulation, however there must be a mediating effect of changes in the soft tissues for joint motion to be changed, yes? (Assuming that manipulation actually achieves joint motion changes – I’m trying to find this out. Results very soon!)

    Jonathan Branney January 6, 2014 6:50 am Reply
  • During my career, I have been to various CE courses. These have included Sahrmann, Gary Gray, McKenzie, and several different manual therapy based courses. The different methods taught in each course are often in opposition to one another. Some have been quite hands on and others have been quite hands off. The one thing that all of them had in common was a “Guru”. The Guru is that one individual whose name is forever tied to the method and who has been the main proponent of the method. The most common characteristic of a guru seems to be charisma. The guru is very personable and confident. They truly believe in the value of what they are teaching and have the ability to make others believe as well. It makes me wonder if the personal interaction between the clinician and the client is more important than anything else you do with them.

    Mike Terrell January 6, 2014 9:53 am Reply
  • There is at least one thing stretching the skin, or focus on the muscle in stretching or training, doesn’t have, but that a focus on placing forces on the spine does have.
    That is the increased perception that a certain movement or excessive external force is possible and the spinal colum will not fall apart. Showing the spine is actually a robust structure, rather then a weak house of cards that will collapse if a unanticipated external force comes upon it.
    However if there is obvious risk on adverse effects, the therapist should take that into consideration. The question then becomes: “why not to employ manips?”
    If the same bennificial effect for other techniques is expected, a rational approach that takes patient preferences, clinical state and circumstances and best available evidence in consideration. (Hicks and Jones Clinical reasonning in the health professions 3rd edition). For the best available evidence part, stretching of the skin is poorly described in epidemiological research literature. It is even worse described what factors indicate response to treatment, or what factors are relevant to assess and how to assess. We should also take in acount that there are no trials whatshowever comparing manipulations vs. skin, or muscle stretching. The effect of muscle energy stretching (METS) does not appear to be better (rather worse), however they do sort an effect, are less known to have adverse effects, METS however are, like the chicago roll manipulation technique easy to employ and rely on a logical, but not fully proven rationale. But then again we do not know how to predict the effect, from an epidemiological point of view.
    In the herefore described model by Higgs and Jones, rationality goes beyond epidemiological evidence. Clinical prediction rules, based on stepwise regression might just be the same as letting the computer deside what clothes are most important to wear, based on the way we commonly look (also see Andy Field: http://www.youtube.com/watch?v=LZtPDgoskfI ) But it might just be a little mathematical clue, in wheter or not to apply manips. It is to be used wisely in the light of previously mentiond EBP model (Hicks and Jones), in which decission making is more then just knowing where to find RCT’s and epidemiological studies.

    BobV January 6, 2014 5:05 pm Reply
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  • I have an opinion, but one research study shows that a ‘sham manipulation’ (one that involved set up, but no thrust) was less effective at improving patient outcomes that a HVLAT. This would suggest that something is happening. Construct validity tells us it happens at the joint since there is a cavitation.
    Is there a placebo? A bias? An equipoise? Probably. But show me the res$earch.

    Steve February 20, 2014 7:11 am Reply
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  • So we got PT’s here discussing about spinal manipulations…. :X

    SSS May 18, 2014 1:32 am Reply
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