The Science of Chiropractic

A Look at the Mechanism of Healing


I have talked extensively about the importance of not just objectifying the chiropractic subluxation but also proving that we had an effect.  We know that there are both mechanical and neurological consequences to the chiropractic adjustment and for the research to encompass both aspects requires an in depth and consistent investigation.  I want to introduce you to some of the more advanced research related to the chiropractic adjustment particularly on the cause and effect. 

In a VERY RECENT 2017 study, Haavik et al stated, “We have yet to fully understand the neuro- physiological mechanisms responsible for such clinical improvements after spinal manipulation of any kind. It is of interest to us whether chiropractic care can induce changes in various aspects of central nervous system (CNS) functioning, including alterations in reflex excitability, sensory processing, and motor control.” [pg 127] What the authors are talking about is related to the adjustments effects on the Central Nervous System (CNS), which is a much more complex process than its mechanical influence. The objectification of the CNS effect is the purpose of this study. 

The authors continued, “Previous research has indicated that healthy individuals have smaller central MU SEP amplitudes (ie, SEP amplitudes following MU) compared with the M + U amplitudes (ie, SEP amplitude calculated as the arithmetic sum of the individual median and ulnar such as Hunting- ton’s increased central SEP ratios have been observed. The increased SEP ratios suggest that these individuals receive distorted and excessive (ie, not spatially filtered) afferent input from their affected limb or limbs, which may potentially cause their motor system to transform these afferent inputs into abnormal “unhealthy” motor outputs. Sensorimotor disturbances are also known to persist beyond acute episodes of pain such sensorimotor disturbances are thought to play a defining role in the clinical picture and chronicity of different chronic pain hypothesized that patients with chronic pain may also have increased central dual SEP ratios.” [pg 128]

The authors reported, “Six subjects (1 woman and 5 men), aged 24 to 50 (mean age, 36.2 ± 12.8 years) with a history of chronic recurring neck or upper limb symptoms (ie, N3 months in duration and severe enough for the subject to have sought previous treatment for this symptom).” [pg 128] Although this was a relatively small study, we will see in the results that the findings suggest further research using larger patient populations.

One of the things that impressed me the most in this study was how the treatment plans were developed.  We would all agree that the spine is a complex genetically structured system that is constantly compensating and adapting to our physical environment.  Historically research has been focused on the ‘treatment side” of chiropractic not diagnosis.  Prior research looked at an “effective dose” of chiropractic rather than identifying and objectifying the lesion being corrected.  Never in research, up to now, have I seen the treatment plan be organized as a “treat what you find” approach.  Since each of our spines is unique, I personally believe we need to continue to structure chiropractic research in this manner.  The authors commented, “The chiropractic care plan was pragmatic and generally consisted of 2 to 3 visits per week for the first 2 to 3 weeks. Frequency was reduced based on clinical findings and patient symptomatology. By the end of the 12-week period, participants were seen once or twice a week. No requirements were placed on the treating chiropractor, other than including chiropractic adjustment or manipulation during treatment; thus, the care plan was designed in conjunction with patient preferences and was based on the patients’ history, symptoms, wishes, and time availability as well as the clinician’s clinical experience and knowledge.” [pg 130]

In conclusion, the paper had reported,

·   The results of this study suggest that 12 weeks of chiropractic care may improve gating of peripheral afferent input to the brain, thus improving impaired SMI [Sensory motor integration] in cortical motor areas and improving processing of motor programs.

·   A few of the chronic pain patients in this study exhibited abnormal gating of proprioceptive afferent input prior to chiropractic care (their medial and ulnar N30 amplitudes were larger than their medial + ulnar amplitudes), which were reversed after the 12 weeks of chiropractic care (noting that the current study design cannot prove causation).

·  The P22-N30 complex dual SEP ratio appears to be a measure that could be used alongside clinical measures in future clinical trials to document neurophysiological changes that accompany treatment of chronic pain.

·   This study supports previous research that suggests that altered sensory processing and motor control may be implicated in the development of chronic neck pain.   [Page 136]


This type of research is to be used to provide the scientific basis for what we do with the understanding that the medical community outside of spine surgery will have little interest in understanding spine care at this level. It is a good example of how we really just need a working knowledge of complex healthcare topics in order to be able to recognize the condition and refer to the proper professional, when it comes to spine, that is what the primary care community is looking for.  So in the end, study as much as you can so you understand your craft, but when it comes to MDs and to patients, keep it simple! 



1.     Haavik, H., Niazi, I. K., Holt, K., & Murphy, B. (2017). Effects of 12 Weeks of Chiropractic Care on Central Integration of Dual Somatosensory Input in Chronic Pain Patients: A Preliminary Study. Journal of manipulative and physiological therapeutics40(3), 127-138.


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