Ten years ago, I knew I was right. I remember being taught how to perform a few basic spinal manipulations of the cervical, thoracic, and lumbar spine. I remember trying to palpate spinous processes, counting each level, checking, rechecking, making sure I was in the spot I was aiming for. I remember being told my palpation skills would improve over time. I remember being taught that it was important to be as specific as possible, targeting the “dysfunctional” segment. I kept having a nagging feeling that what I was being taught wasn’t quite true. I slowly became skeptical of the claim that manual therapy, and specifically, spinal manipulations, would require particular technical procedures, and could result in specific biomechanical and therapeutic effects.
And it turned out I was right.
A 2023 meta-analysis on Spinal Manipulative Therapy confirmed this, and it felt so very good. After reading the study, I had a growing sense of righteousness; my skepticism was justified, my objections were well-founded. It can be very satisfying to read a study that confirms something you were pretty sure about. I do wonder what some of my orthopedic teachers from physical therapy school would think of this study. Would it change their minds? Would it change how they taught these techniques? Would it change what they would say to patients? Or would they just dig in to their positions, and double down on the claims made? I always try to critically evaluate my own beliefs, but it can be hard to change your mind when a study goes against something you believed in.
In Sorensen et.al., the authors found ten randomized, controlled trials that compared targeted vs non-targeted Spinal Manipulative Therapy. They found that both groups did equally well when considering pain and disability. So what does this mean in practice? A study like this, for me, has two implications, one specific, one general. In reference to the actual results, we should probably reconsider our theoretical model of how SMT “works,” as well as change our explanations to our patients. But more generally, it highlights the importance of basing our beliefs and the practices we employ as physical therapists on methodologically sound research.
We all have a psychological and cognitive bias that causes us to amplify things that confirm our prior beliefs, and discount or disregard things that challenge them. Confirmation bias can shape how we think, and as physical therapists we need to take this into account when we are looking at physical therapy research. We ought to be conscious of this when we are reading research and thinking about our closely-held beliefs. We need to pay special attention to the science when it goes against our beliefs; when our own biases are challenged, we need to be more rigorous.
I experienced the flipside of confirmation bias after reading a study on Pain Neuroscience Education by Martinez-Calderon et.al. I have written a few blog posts about the emerging neuroscience of pain and its therapeutic implications. I bought Explain Pain, Therapeutic Neuroscience Education, and Why Do I Hurt? I have found these concepts generally useful for many patients in the clinic. But according to Martinez-Calderon and others, after eight systematic reviews, thirty meta-analyses and decades of research, we still can’t say anything clinically definitive in regards to pain science. The authors cite methodological concerns limiting the robustness of the recommendations we can make, but shouldn’t we have found something by now if there was something there? Maybe it is less effective than we thought? Of course, by its nature the conclusions of science are provisional. They are subject to change in the future, if something better comes out. But reading this study was majorly disappointing. I wish there was a different conclusion, more solid results, definitive, practical clinical implications. But no.
My experience reading these two studies highlights the problem with relying on clinical experience and intuition when making clinical decisions and employing different practices. We ought to defer to what the science tells us, and scale our confidence in our beliefs in accordance with the data. The entire field of biostatistics is dedicated to systematically and rigorously obtaining, analyzing, and interpreting quantitative evidence in medical research. We ignore it at our own peril.
“Mathematics, rightly viewed, possesses not only truth, but supreme beauty cold and austere, like that of sculpture, without appeal to any part of our weaker nature, without the gorgeous trappings of painting or music, yet sublimely pure, and capable of a stern perfection such as only the greatest art can show. The true spirit of delight, the exaltation, the sense of being more than Man, which is the touchstone of the highest excellence, is to be found in mathematics as surely as in poetry.” -Bertrand Russell, The Study Of Mathematics
References
- Martinez-Calderon, J., Ho, E. K.-Y., Ferreira, P. H., Garcia-Muñoz, C., Villar-Alises, O., & Matias-Soto, J. (2023). A call for improving research on pain neuroscience education and chronic pain: An overview of systematic reviews. Journal of Orthopaedic &; Sports Physical Therapy, 53(6), 353–368. https://doi.org/10.2519/jospt.2023.11833
- Sørensen, P. W., Nim, C. G., Poulsen, E., & Juhl, C. B. (2023). Spinal manipulative therapy for nonspecific low back pain: Does targeting a specific vertebral level make a difference?: A systematic review with meta-analysis. Journal of Orthopaedic &; Sports Physical Therapy, 53(9), 529–539. https://doi.org/10.2519/jospt.2023.11962
Physical Therapy Evidence 