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Issue 12

Table of Contents

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Needling point location used in sham acupuncture for chronic nonspecific low back pain, a systematic review and meta-analysis

Dr. Cody Misuraca PT, DPT

Key takeaways
  • Sham-controlled randomized trials can give us insight into the mechanisms behind how certain interventions work
  • Narratives regarding mechanism of action for interventions should be influenced by existing sham-controlled research
  • Sham-controlled studies that find a positive effect for the studied intervention in the presence of a non-convincing sham should be given less weight
  • Interventions that have been shown to be no more effective than convincing sham can still be used, but caution should be taken in making claims about specificity of the intervention

 

The concept of the “placebo effect” in randomized controlled trials (RCTs) has been intriguing to me for years. In short, the “placebo effect” is a positive effect observed in a treatment group that is given a sham intervention while being compared to a group being given the “true” intervention of study.

The use of a sham intervention in a placebo group is an important piece of determining whether a given intervention’s observed benefit is due to something specific or unique to it, or some other non-specific effect related to receiving what appears to be treatment. There are a lot of variables that can contribute to the observed effect of an intervention, including “identifiable health care paraphernalia and settings, emotional and cognitive engagement with clinicians, empathic and intimate witnessing, and the laying on of hands”¹.

Additionally, natural history (the natural course of a given health condition when left untreated, especially those that tend to improve on their own in time) and regression to the mean (a statistical concept that describes the tendency for a variable to move back toward the average following an extreme value) can play a role in the observed improvement in a condition when treatment for it is sought.

In the context of physical therapy practice, developing an understanding of the extent to which a given intervention’s effects are specific or nonspecific is important because it allows us to be more accurate with our narratives.A narrative is the explanation we provide regarding “how” or “why” an intervention has the effect that it does, and the narratives we use can have an impact on our patient’s beliefs about their bodies.

If a given intervention has been shown in well-designed sham control trials to be no better than the sham despite the intervention being applied in a precise manner with the intent of intervening on a specific “dysfunction” in the body, then we should have far less certainty in the narrative that the intervention has the effect that it does because it’s impacting said “dysfunction.”

Supplying the narrative that a given intervention works because it’s addressing this “dysfunction” can develop and support the patient’s belief that they do, in fact, have a “dysfunctional” body. This is especially problematic when existing research demonstrates non-specific effects for the intervention, suggesting that it does not work by specifically acting on some “dysfunction” in the first place.It’s important to note that in any study comparing an intervention of interest to a sham, the sham intervention needs to appear similar enough to the intervention being studied so that the participant receiving the intervention is not “unblinded,” or made aware that what they are receiving isn’t the real deal.

Ideally, all RCTs utilizing a sham intervention would conduct a post-treatment analysis of which treatment the participants thought they received, but this has yet to become a standard practice. Bearing that in mind, I think it’s interesting to observe how realistic sham interventions appear in relation to the observed effect in sham-controlled studies.

Enter this month’s research article, “Needling Point Location Used in Sham Acupuncture for Chronic Nonspecific Low Back Pain,” published in September of 2023². While acupuncture is not an intervention that physical therapists can provide, this systematic review and network meta-analysis serves as a good case study on the interplay between observed effect and how convincing a sham is compared to the reference intervention.

This review included 10 RCTs with a total of 4,379 participants experiencing chronic low back pain lasting greater than 3 months. The review primarily looked at the difference in effect between acupuncture and two types of sham, which they identified as Sham Acupuncture Therapy verum (SATV, or when the alternative was applied to the same points as the acupuncture) and Sham Acupuncture Therapy sham (SATS, or when the alternative was applied to different points as the acupuncture). It’s worth mentioning that in some cases the sham interventions included superficial as opposed to deep needling, and in other cases either blunt needle devices or toothpicks were used. Ultimately, they found that when SATV was used, the effects on pain and function were indistinguishable from acupuncture, while the acupuncture outperforms SATS for both pain and function.

Put in simpler terms, when sham acupuncture was performed at the same site as the actual acupuncture, the same beneficial effect was observed, while sham acupuncture performed at a different site from the actual acupuncture was not as effective. It’s worth noting that a separate systematic review and meta-analysis found that the most-commonly used acupuncture sites for low back pain are BL23, GV3, BL20, BL40, and BL25³, which are nearly all local to the lower back (BL40 is the only exception, being on the posterior knee). This suggests a disparity in how realistic a SATV vs SATS sham would appear to be, with the SATV sham most-likely being applied in the region of pain.

Interestingly, the authors postulated that this outcome could have been due to some other physiologic effect related to stimulating the acupoint, and that SATV should not serve as a true control. As a naturally skeptical person, I am hesitant to accept this conclusion based on the assumption that acupoints are a discretely identifiable structure that have a reliable effect when stimulated. Indeed, the current body of literature on acupoints has been unable to definitely determine whether acupoints exist as distinct entities, or whether they hold any clinical relevance⁴.

Given that, I am more inclined to view the data from this review as evidence that a more-convincing sham performed in the same location as the reference intervention is more likely to show an effect that a less-convincing sham performed at a different location than what would be expected. On the topic of the relationship of how convincing a sham is as it relates to the observed effect, there are similar examples of this for interventions that are currently utilized in PT practice.

For instance, a systematic review and meta-analysis on the effectiveness and adequacy of blinding in dry needling trials found that when blinding was performed adequately, no difference was found between active and sham dry needling in the short or long-term for pain, while studies with inadequate blinding of sham dry needling consistently showed favorable effects on pain for active dry needling⁵.

If there is good reason to think that participants in a sham intervention group were un-blinded, then a positive observed effect for the reference intervention should not be surprising, or regarded as a true effect on its own. There are similar instances of the relationship between convincingness of the sham and the degree of effect observed for the reference intervention in studies on kinesiotape. Below are several examples of the sham vs reference taping intervention and the observed treatment effect, pulled from existing studies on kinesiotape:

(+) effect for kinesiotape⁶

No difference found⁷

(+) effect for kinesiotape⁸

No difference found⁹

(+) effect for kinesiotape¹⁰

This is not an exhaustive list of all sham trials ever performed on kinesiotape, but it does illustrate the tendency for a positive effect to be observed for the reference intervention when the sham intervention is not particularly convincing, while a more thorough replication of the reference intervention tends to result in no observable difference in effect.

If the reference intervention being studied indeed has a specific effect related to its precise application, then a positive effect should be observed when the sham intervention is applied in the “right” place but in the “wrong” way. This is an important concept to bear in mind when reading placebo or sham-controlled trials; ideally, studies of this kind would have a built-in post hoc assessment of whether the participants remained blinded to their group assignment, but in the absence of that it is worth comparing the sham intervention to the reference intervention to see if it carries face validity.

If the sham intervention appears unlikely to be a convincing replication of the reference intervention, then it’s probably worth proceeding with some degree of skepticism in the presence of a positive effect observed for the reference intervention. At the end of the day, I do not think that interventions such as acupuncture, dry needling, and kinesiotape are completely useless for managing pain. Indeed, all of the studies I cited above did find a positive effect on people’s symptoms, and it’s completely normal for people to just want to feel better, mechanisms be damned. I do, however, think that our explanations for “how” or “why” these interventions work should bear in mind the existing research that demonstrates non-superiority relative to sham.

It’s OK to want to use interventions that make people feel better, but ideally our narratives surrounding these interventions would focus less on “dysfunctions,” hopefully minimizing a negative trajectory of beliefs about one’s own body.

References:

 

Cody Misuraca is a physical therapist and strength coach in Seattle, WA. He works as a sports physical therapist for a community hospital system and also owns Waypoint Strength and Performance LLC, which offers strength coaching services. The views and opinions expressed in this review are those of the writer and do not necessarily reflect the views or positions of any institutions he is associated with.