Why Do Chiropractic Adjustments Make Popping Sounds? | Podcast Ep. 246

Foreign hello and welcome to the Evidence Based Chiropractor. I am your host, Dr. Jeff Langmaid. And on today's episode we are taking a peek at a really interesting study titled Cavitation Sounds during Cervical Thoracic Spinal Manipulation. This came out in the International Journal of Sports physical therapy in 2017. And this addresses one of the most, I don't know, controversial, confusing, ongoing debated topics that I've seen in chiropractic and that is the noises, the pops, the cracks, cavitations. What's going on? When you deliver the adjustment, which side is making the noise? Why is it making the noise? This study starts to frame some, maybe some answers and maybe starts a few more questions. But I think it's a really important piece of the puzzle for a clinical application because understanding what goes on, what makes the noise, helps you communicate better with patience, which is ultimately what it is all about. 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But for today's episode, we are talking cavitation sounds during cervicothoracic spinal manipulation. So we are analyzing high velocity low amplitude adjustment, hvla. We've seen in literature on this podcast time and time again reductions in pain and disability following an adjustment or manipulation. And cervical thoracic is no exception. Right? Reductions in neck pain. We've seen reductions in even headache with cervical thoracic reductions in shoulder pain. Very important piece of the puzzle. So the question has really been revolved around, well, which side? You know, if you line up on the left hand side on a pedicle, which capsule is making the pops and cracks. And secondly, is it collapse of a bubble or initiation of a bubble? So gas bubble collapse or the cavitation phenomenon is traditionally be accepted as the mechanism for creating the joint cracking sound. However, Greg Kotchuk challenged this hypothesis and proposed that joint cracking is associated with cavity formation within the synovial fluid rather than cavity collapse, which is like mind blowing to think. It's literally the exact opposite. And I think there's a lot of research that can, should and is being done specifically relative to that. Is it the release of a bubble? Is it the formation of a quote unquote bubble? What's going on in that synovial fold that is making the noise? A lot of times we associate these high velocity adjustments with a fast. Right? It's high velocity for a reason. High velocity. So for cervical manipulations, you know, think about the duration of that. Do you have any guesses on what that would be? Well, the duration of a thrusting procedure is 800 to 200 milliseconds. So this is happening super, super, super fast. And that's part of, you know, delivering a high velocity, low amplitude adjustment. So these researchers took, I guess, what you call recording devices. They kind of set up microphones, miniature microphones on each side of the individual. Then they really analyzed the actual wave forms that were occurring with noise, you know, with sound, to determine which happened first, how long did the cavitation last, and what is the thrusting manipulation duration. So a lot of information that they were able to glean from a relatively simple, in theory, you set up some microphones and you listen. But it's a lot more complicated than in practice. So they found that cavitation was significantly more likely to occur on the side contralateral to the short level application. So the first noise, the initial noise, the cavitation, was significantly more likely to happen on the contralateral side. Which also to me is anyways mind blowing. Maybe not to you, but it's mind blowing to me that a lot of the cavitation is happening on the contralateral side. So their points were they found the results indicate that cavitation was significantly more likely to occur on the side contralateral to the short lever application of the manipulative process. In addition, unilateral cavitation sounds were detected 91% of the time, while bilateral cavitation sounds were detected just 8% of the time. So a lot to unpack there, right? It's more likely and significantly more likely to happen on the side contralateral. Yet on the unilateral side, it still was over 90% of the time, but hardly ever, less than 10% of the time was there bilateral cavitation. So just really interesting and things that I would have almost thought the opposite or different if you would have asked me before reading this. So let's talk a little bit more about Dr. Kotchuk's research because they cite it here, I think. Gets really, really interesting. They say Kotchuk et al. Reported a dark intra articular void during MCP distraction. Notably, this dark intra articular void was associated with concurrent sound production. That is the joint cracking was associated in time with cavity formation rather than cavity collapse within the synovial fluid with an average of 1.8 millimeters of joint surface separation. Kotchuk et al. Referred to this process as tribonucleation. That is, when sufficient distraction force overcomes the viscous attraction or adhesive forces between opposing joint surfaces, rapid separation of the articulation occurs with the resulting drop in synovial pressure. Makes sense to me. Allowing dissolved gas to come out of solution to form a bubble cavity, clear space or void within the joint. So a lot of really interesting stuff to dive into right there. Probably spent a whole episode just on that paragraph. But let's talk about a few different things of it. So number one, they found, you know, that one, almost 2 millimeters of joint surface separation. So that's really interesting, right, because when we're able to gap the facets, there's, you know, beneficial, there's benefits to gapping the facets outside of central nervous system, peripheral nervous system, literally, gapping the facets tends to provide pain reduction for a lot of people. Now, in 2 millimeters is nothing to sneeze at. That's a decent amount of motion in, in that area. Now what they're saying is that when that distractive force overcomes the adhesive forces or even just the viscous attraction on a cellular level or elemental level, rapid separation results in a drop in synovial pressure. So I think of this, and this probably isn't exactly in tune with the research, but I almost think of it like decreasing disc pressure, right? This is decreasing synovial pressure, but when that happens, there's essentially a void. And when I start to think about it that way, this makes a lot of sense that when there's a void, something's going to fill that void. So it could be the formation of a bubble, a cavity, or a clear space within the joint. So really opposite. And I've even done a few talks and I've talked about essentially the bursting of the Bubble, so to speak. So it seems to be the exact opposite. So really interesting to think about. Additionally, the fact that the cavitation sounds quite often are happening contralateral also is just sort of mind blowing to me. I always think of it like, you know, you're making the impact on the side that you're approaching where you're delivering that force. But what we see is many times that is happening contralaterally and for that matter, as they say, less than 10% of the time it's happening ipsilaterally. So really, really, really interesting. They also then talk a little bit about the clinical relevance of cavitation sounds, which has been hotly debated for a long time. And they find the cavitation sound is traditionally considered by many therapists, chiropractors and osteopaths to be an important indicator for the successful technical delivery of a high velocity, low amplitude thrust manipulation. However, four previous studies have suggested that the audible pop following HVLA thrust manipulation is not to the clinical outcomes of pain or disability. Nevertheless, these authors investigated the thoracic and level pelvic regions, not the cervical spine or the cervical thoracic junction. So really, again, interesting stuff, probably providing more questions than answers, but it's really interesting to think about the fact that things are happening contralaterally. Whether there's a sound or not may not indicate success. And that's something I think many of us have come to know over time. But they also talk about the fact that specificity seems to be difficult to achieve and come by, let's put it that way. So when you're getting in there, adjusting a joint, and that doesn't mean, let me be very clear about this, it doesn't mean that you should be as specific as possible with your examination and with your delivery of that thrust, but how that is resonating throughout the spine seems to be much more diffuse than specific. And they're saying, especially in the lumbar spine, so cervical spine, you probably can be a little bit more specific, or at least the research shows we are traditionally more specific, whereas in the lumbar spine, exceptionally difficult to gain any real specificity in where you're delivering and how you're delivering that adjustment. Maybe not. You can specify the how, but maybe not exactly which joints are being gapped and which joints are cavitating. So all really important points of the puzzle, right? You know, we talk and, you know, probably the most often many of us have heard about chiropractic is when people talk about cracking their neck or cracking a joint, right? And you see this in, you know, chiropractic is displayed many times on television or in a show or whatever else it may be that it' always relative to the crunch or the crack of what we do. And the fact that we continue to learn more about that starts to become really, really interesting. Number one, contralateral side interesting. Not what I would have thought. But the really meat of this study in my opinion is where they start to talk about how the cavitation sound occurs and that it's really the formation based upon the drop in pressure than it is the destruction based upon an increase in pressure. That's something where I want to give Dr. Kauchuk absolute credit. It seems as though he's been leading the charge in trying to help us understand more about exactly what occurs when we deliver an adjustment. And that's a really important piece of this puzzle over time. One of the challenges, one of the beauties of what we do, but it's also one of the challenges in what we do as chiropractors is that quite often what we do with an adjustment, there's just a lot of separate mechanisms of action. There's a biomechanical component, there is a disc component, there's a central nervous system component, there's a peripheral nervous component. There have been changes in biomarkers in the brain after an adjustment. There's justthere's the reflex, the muscle spindle, I mean, you name it, the list goes on and on and really identifying which of those is the most important. But if they're gonna happen in totality, well, what's the totality of that and what's the benefit? And we see that bottom line is that we see continually that chiropractic care, hvla drives down pain and drives down disability and helps people live a more functional life, a more pain free life and a higher quality of life. When we geek out on all of this research, cavitations, ipsilateral, contralateral, everything else, it really comes down to are you making an impact on the life effect of what's going on in the individuals in your practice? Because as we've talked about many times on this podcast, on and off this podcast, people don't come into your office because they're in pain. People will live in pain for months, years and decades before deciding some do something about it. They decide to do something about it. When they start experiencing a life effect, when they can't do those things that they'd love to do with those people, that they'd love to do those things with that is what ultimately drives somebody into your practice. So understanding the best ways that you can apply your techniques, understanding the background, the research about what it is that you do and how it can impact and benefit, more importantly, benefit the individuals in your community. The clearer you are on that, the more understanding you have and the better you are able to communicate that the more successful practice you will have over time happens time and time again. Hopefully I will say that's why you listen to this podcast, because we can offer at least a little bit of advice of interest and of education regarding the research that's out there and how you can apply it to your practice. And hopefully this week was no exception. So I hope you have a fantastic week in practice and I will talk to you soon.

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