Jared Powell:
Today's guest is Dr. John. John is an orthopedic surgeon and researcher based in Nashville, Tennessee. John has had a decorated career, both as a practicing shoulder surgeon and academic, and has produced dozens of influential research papers, especially in the field of rotator cuff pathology. Thus, the cornerstone topic of this podcast episode is the rotator cuff tear, which is something you will most likely see almost every week in your clinical practice.
Jared Powell:
It is well known that I have been on record challenging the effectiveness of shoulder surgery for managing rotator cuff tear tears for many years. But what does a shoulder surgeon think? Does a specialist shoulder physio and shoulder orthopedic surgeon converge on a singular truth regarding the best practice management of rotator cuff tears? Or are we from two different worlds? You'll have to listen to find out. We have a wide ranging conversation about the etiology of rotator cuff tears, including modifiable and non-modifiable risk factors, the natural history of rotator cuff tears. What predicts the outcomes of physiotherapy for managing individuals with rotator cuff tears? And what is the ultimate role of surgery for managing rotator cuFFT test?. Without any further delay, I bring to you my conversation with Dr. John Kuhn. Dr. John Kuhn, welcome to the show. Thank
John Kuhn:
You. It's happy to be here. This
Jared Powell:
Is good. This is a, this is a treat for me, John. I was just telling you that I've been reading your work for a, for a long, long, long, long time, and it's a real privilege to be able to sit down and chat for an hour or so about a topic that seems to be near and dear to both of our heart, which is out of rotator cuff tears and rotator cuff disease and rotator cuff pathology, whatever you want to call it. But before we get into the, to the academic intellectual stuff, can you please tell me and and the listeners about who you are, what you like to do, both professionally and personally? Sure.
John Kuhn:
Well, of course I'm an orthopedic surgeon and I work at Vanderbilt University Medical Center that's in Nashville, Tennessee, a home of country music. And I, I run a group of shoulder surgeons from around the country called the Moon Shoulder Group. And that's where most of this research comes from. I know we'll talk about that in a little bit, but for recreation I guess my biggest passion would be fly fishing. We have a cabin in the Appalachian Mountains and I can literally walk out the door of my cabin and have my feet in the water and start fishing right away. And I was just there this past weekend, so it was terrific. Our, our weather in October is fall here in the United States, and we have beautiful leaves that change and the sky is blue and the weather, the weather's not too warm, and it's cool at night, it's perfect time. So that's my real passion is to be fly fishing in in October. Sounds
Jared Powell:
Idyllic. I do hear that fall is, is one of the, the better seasons over there in the US where you get that beautiful weather. So it's nice to hear that that's, that's your experience as well, Dr. John, can you tell me a little bit about this moon shoulder group, which is, has produced some really wonderful research over the years. How long have you been running that for and what's been your experience doing that?
John Kuhn:
Sure. So I have to acknowledge my partner at Vanderbilt, Dr. Kurt Spindler, he started a multicenter orthopedic outcomes network, which is what Moon stands for, to study ACL Tears. And it's, his, his work is very famous in the ACL world. And when I joined him at Vanderbilt, wanted to do the same thing. So I basically took his knee surgeons and found their shoulder surgeons at the same institutions. And we met and started to collaborate and started to do research. So we, we started the moon shoulder group 20 years ago now in 2004. And we wanted to study shoulder things, of course, 'cause we're all shoulder surgeons. We picked rotator cuff disease, honestly, because we thought it was most fundable. We thought it could be get funding through workers' compensation grant sources through aging grant sources. There's a lot of different opportunities for funding rotator cuff disease.
John Kuhn:
If you wanted to study instability in the athlete, there's not as much opportunity to get funding for that. But rotator cuff disease, we thought there'd be opportunities for funding. So we decided to study that. And we spent about two years collaborating and aligning our practices. So, like, for example, we all sat around the table and said, what is the best physical therapy program to use after surgery? Well, there's not a lot of great data. So when there's not a lot of great data, we developed consensus and we said, everybody in our group is gonna do it this way. And we did the same thing for getting imaging, for getting MRI scans. We're all gonna do things the same way. We looked at how do we classify rotator cuff disease, both on the MRI and during surgery, we did a lot of preliminary work. It took us about two years to do all this before we ever entered a patient into the database.
John Kuhn:
And what's interesting is, you know, one of the things we couldn't agree on, and there wasn't much literature to help us, was who needed surgery and who didn't. There's a couple systematic reviews in the literature, but they really weren't that helpful. And when I, we sat around the table with all my colleagues, we all had different ideas about who needed surgery for their rotator cuff disease and who didn't. And what's interesting is if you look at the prevalence of rotator cuff surgery in the United States, different states have different levels of rotator cuff surgery. So, and they vary as much as tenfold one state to another. So it's pretty clear that surgeons really didn't know who needed surgery and who didn't. So we decided to do a study where we took everybody with a rotator cuff tear, it was atraumatic and they had symptoms and put them all through the best physical therapy program we could find. And so we did a systematic review looking at the level one studies that showed physical therapy was helpful for any kind of rotator cuff disease. And we extracted the details about those physical therapy protocols and jelled them into one protocol. And then we decided to send everybody we saw with an atraumatic symptomatic full thickness rotator cuff tear through that therapy protocol. And that was our first study which is actually quite surprising to us how it turned out. Yeah.
Jared Powell:
So let's go straight there if we don't mind. How did it turn out?
John Kuhn:
Yeah, so, you know, we're surgeons and, and honestly most of us were taught that these all needed to be operated on. It was almost like an open tibia fracture. If you had the disorder, you needed surgery. And so we thought that maybe 15% of the people would get better with therapy. And we expected it would be the older person who lives in the nursing home and that plays bingo. That person probably doesn't need surgery, but everybody else we thought would need to have an operation. So we did the study. We sent over 400 patients from around the United States through this physical therapy program. You know, everybody in the United States has different insurance. So some people only had so many therapy visits. So we had it established that they could move to a home therapy program whenever the therapist thought it was reasonable.
John Kuhn:
And we, what we did is we sent everybody through therapy, had them come back and see us at six weeks to check their progress. If they were making no progress and really anywhere along our, our treatment timeline, they could drop out and have surgery anytime. But if they were making progress at six weeks, we said, let's go another six weeks. And so we'd go for a total of 12 weeks of physical therapy. And what we found, much to our surprise at the time, was that the therapy was highly effective. It worked for about 75% of the people, and they did well and they didn't want to have surgery, which was quite surprising to us. We did not expect that at all.
Jared Powell:
So, yeah. And so this was published in 2013, roughly? Is that, is that right John?
John Kuhn:
Yes. I think that's, there's a few papers that I would talk to your listeners about is our protocol, which is in the literature as well. That was a systematic review. And the protocol is there. It's also on our website if anybody wants it, we have a website called Moon shoulder.com, and they, all of our therapy protocols can be downloaded on that website. We published the physical therapy data after we followed patients for two years. We published a paper called The Effectiveness of Physical Therapy in Treating Rotator Cuff Disease. And that was a two year follow up paper. And we actually just published our 10 year follow up. Mm. Just this past year. Yeah,
Jared Powell:
Yeah. I just read that 10 year follow up one and shared it on social media. Do you mind just giving us a quick little revealer on how that turned out? 10 years later? Did everyone go on and need rotator cuff surgery or did they do okay with non-operative treatment?
John Kuhn:
Yeah, so, you know, at two years the numbers were about 75% of people did well with physical therapy. And we actually collected data to try to identify what was the predictors of surgery, who needed surgery. That's probably what we were after. And in that two year data, we had another study predictors of surgery. And what we found was the thing that drove surgery early was the patient's expectations regarding physical therapy. If they didn't think therapy would work, it wasn't gonna work. If they did think therapy would work, it would work. Mm-Hmm. And by far, that drove surgery in the early, you know, in the first six months of this study, there were some other things that were statistically significant. Activity level, for example, is one, but really what drove early surgery was the patient expectations, which is another thing that was completely surprising to us. Yeah.
Jared Powell:
I wanna linger on that point for a moment, if that's okay. As a surgeon, John, and I don't want to generalize surgeons here in Australia, orthopedic surgeons don't have the best reputation of being totally cognizant and aware of psychological factors influencing outcomes of their surgeries. Perhaps being a little bit harsh, there's good and bad of course, in every single profession. How did you interpret or or deal with those findings that low expectations of of physical therapy was a key driver of needing surgery versus the anatomic features of the rotator cuff?
John Kuhn:
Remind me to get back to the anatomic features. Yeah. Because that's what, but you know, as, as orthopedists, we tend to work from the head down. We don't discern ourselves at all with anything above the chin. And, you know, we do cervical spine surgery all the way down to the toes, but we don't do anything with the brain. And to have that drive surgery was a amazing to us. You know, we, we also knew that people who had instability that were volitional, they wanted their shoulders to come out, did poorly. There was some evidence of that really. Orthopedics historically never really looked at those concepts. Since that time, you know, since our, our work came out 20 years ago, a lot of other things have come out showing that our outcomes are heavily dependent on the patient's and grit. They call it their ability to accept change their mental health status. These things all predict outcomes for just about every orthopedic surgery there is. So it's something we can't really ignore. We really have to, if you wanna have good outcomes, you need to be thinking about these things and address 'em.
Jared Powell:
Yeah, no, I totally agree. Let's, before I forget, let's get back to the anatomic features of the rotator cuff. Yeah.
John Kuhn:
So interestingly, so, you know, we didn't expect the outcome that we saw. We didn't think that people would get better with therapy, but they did. And I remember my ideas come to me best in the morning and I was getting ready for work one morning. I just was running through, how can this be true? How can this be true? And then I started to think about the prevalence of rotator cuff disease and doing some math in my head. And you know, if you look at studies where they go into a population, a small town in Japan or in Korea, and they scan everybody in that town, when you do that, you realize that about 22 to 23% of people in a population have rotator cuff tears. And if you apply that to the US population, that means there's 26 million rotator cuff tears out there in the population in the United States.
John Kuhn:
And we operate on 500,000 per year. That's a very robust estimate. It may be less than that, but if you do the math, that means we're operating on about two to 3% of all the rotator cuff tears that are out there. And suddenly it made sense why physical therapy would work. There's a huge cohort of people who don't even come to your office that have rotator cuff tears, full thickness, complete rotator cuff tears, and they don't come in to see you. And that's the majority of people with rotator cuff tears by far. We do see a small subset in our offices and they have pain and they have disability, which we can talk to in a little bit. But most people don't have problems with their rotator cuff tear. They're out there leading their lives in their sixties and seventies and not having an issue.
John Kuhn:
So it made sense why physical therapy would take someone who's symptomatic and make them asymptomatic. The other thing to point out is that we surgeons have a bias. We assume that the broken anatomy is responsible for the symptoms, and then we feel that if we fix the anatomy, the symptoms will go away. That's a surgeon's bias. Physical therapists look at the world completely differently. They look at the world, oh look, you have scapular dyskinesis. That's where your pain's coming from. Oh look, you have a tight posterior capsule with an internal rotation deficit. That's where your pain is coming from because you guys can address those things, right? So, you know, as surgeons, we focus on the anatomy. And so what we did is we did a couple of other studies to look and see does the anatomy predict anything? Mm-Hmm. We looked at our patients and tried to correlate pain with the severity of the rotator cuff disease.
John Kuhn:
No correlation at all. We thought, okay, well what about activity level? We would expect people with larger tears to be less active. No correlation at all. Alright, what about duration of symptoms? Right? If you have a larger tear, you should have had symptoms for a longer period of time, no correlation at all. So every time we looked at the anatomy, it didn't correlate with the symptoms at all. Which again, as a surgeon, it makes me have to think differently because the anatomy, the thing that we see on the MRI for most people is probably not causing their symptoms.
Jared Powell:
Yeah. John, when I first read this work over a decade ago now, or roughly a decade ago when these studies came out in the mid 2010s, it really just changed my whole worldview. And so I want to thank you for publishing these studies because I was dead set certain, sorry, that's an Australian term that, you know, the anatomic features of the rotator cuff tear were the main drivers of, of shoulder pain. And that surgery was the gold standard treatment. You had to correct that defect, otherwise the tear will get worse over time and pain will go on, so on and so forth. It was this, this negative sequ that, you know, that hacked to be corrected sooner than later. And you really challenge that. I wanna ask you how, as a surgeon, how your work has been received amongst your surgical colleagues. Because a lot of what you promulgate and preach and publish about in the literature, perceptibly challenges a lot of orthopedic surgeries, specifically relating to the rotator cuff and this structuralist paradigm that orthopedists see the world within. So have you been embraced? Have you been shunned? Is it a bit of both amongst your colleagues?
John Kuhn:
I don't think shunned. There's something called confirmation bias, right? Mm-Hmm. So you carry a set of beliefs and when you see evidence in front of you, if the evidence supports your beliefs, you tend to believe it. If it doesn't support your beliefs, you tend to reject it. And that's called confirmation bias. And I think we all carry that, and I think surgeons carry that. And I remember when I first presented this data and first started publishing it, I was asked to debate whether or not a rotator cuff tear needed to be fixed. And the moderator of the debate was Gary Gartzman, who we used to be the president of the American shoulder and elbow surgeons very well known shoulder surgeon in Texas. And he presented a case of a 63-year-old gentleman with a two centimeter tear, a traumatic symptomatic. And I had to take on the, you should do therapy for this.
John Kuhn:
And then someone else had to take on the, you should do surgery for this. And so we had the debate, I gave all the evidence that I had, and then the other guy gave his evidence about surgery. And then Gary Gartzman said, well, this was my shoulder and I did therapy and I'm fine. So in, in our world, I think that helped launch things and it, and, and it was hard for people to accept. I think people are more accepting now. They still have concerns. And I, frankly, I still had concerns. You know, we published this at two years. At that point we didn't know what happens at 10 years. And so we, we recently published that paper, which hopefully will convince people that therapy is more durable than they think. Because we were worried, you know, here we have a whole cohort of people that we treated with therapy and at two years they're doing fine. But what would they look like in 10 years? And should they have had surgery, we don't know. But we, we know now at least for 10 year follow-up. They tend to do well.
Jared Powell:
Okay, that's good. So I'm just gonna summarize that quickly. So you did a prospective study in a cohort of 450 patients. They underwent non-operative treatment for rotator cuff, a full thickness rotator cuff tear. What size was that? Was that just any size or up to two centimeters or three centimeters?
John Kuhn:
We did any size, but they were all atraumatic.
Jared Powell:
Yep. Beautiful. And that two year follow up, 75% roughly did very well with non-operative treatment. 25% chose to undergo surgery. Is that right? Yeah.
John Kuhn:
And again, the thing that drove that early surgery was the patient's expectations, correct.
Jared Powell:
And not the anatomic features of the cuff tear and then at 10 years follow up similar numbers.
John Kuhn:
Yeah. So what's interesting is 10 years is a long time, and this is an older population, so about 9% of the cohort died of unrelated causes. One patient had a reverse arthroplasty and still 70% of the people were doing well. And we looked at their patient reported outcomes and they really did not decline over the 10 year period. Hmm. You know, we, if we expect tears to enlarge, if you look at the natural history studies, and there's about four in the literature, including some done by my colleagues at Wash u in, in St. Louis, rotator cuff tears do enlarge in about half of the people who have them. And our concern was, okay, we have this cohort of 450 patients. If we follow 'em for 10 years, and half of them have enlargement of their tears, are they gonna decompensate? Are their patient reported outcomes gonna do poorly?
John Kuhn:
Well, at the end of 10 years, we still had about 70% of people that never had surgery. So, you know, the, the curve was pretty steep at first and those are the people that didn't think therapy would work. And then the curve was fairly gradual over the 10 year period of people dropping out and having surgery. And what showed up later, you know, the early surgery was driven by patient expectations, but the later surgery was driven by workers' compensation and activity level. And interestingly, smaller tears were statistically more likely to have surgery than larger tears. Which was kind of interesting as well. Those came out to be the statistically significant features that drove surgery. It really had nothing to do with the anatomy, as you mentioned, the size of the tear and nothing about the anatomy predicted surgery. What's interesting though is the patient reported outcomes did not change over the 10 year period.
John Kuhn:
And which means that progression may not be that important for most people. That flies in the face of what everybody thinks. A lot of surgeons in the US would say, we need to operate on this and fix it so it doesn't progress. So you don't end up with a reverse arthroplasty. Well, I like to tell people we had one reverse arthroplasty in our entire cohort over 10 years. That's 0.2%. And we had 9.8% people die over the course of the cohort. So you can tell your patients in the clinic, they're 45 times more likely going to die than need a reverse arthroplasty. I don't think many surgeons will say that, but , that's the truth. Yeah,
Jared Powell:
That's, that's hilarious. I can see that happening in orthopedic consulting rooms all over the world tomorrow. Thanks, John. I wanna chat about, let's go straight to the progression of the rotator cuff tear and the natural history of rotator cuff tear and pathology and the role of surgery and possibly changing that or stopping that. Let's have this conversation 'cause it's really important. So you alluded to a moment ago that you know, roughly one in every two people's rotator cuff tear will progress over time given, you know, it's usually five years or, or 10 years or something like that. The assumption or belief is that smaller tears are more stable and that larger tears are more unstable and are more likely to progress over time. I'll get your response to that in a second. So is all of that stuff true? And you know, if it is true or false, what's the role of surgery in intervening, say in a 40-year-old individual who presents with a non-traumatic one centimeter full thickness rotator cuff tear, should that individual undergo surgery to stop the natural progression of that rotator cuff tear down the line? And as you said, will they end up, you know, with some sort of rotator cuff arthropathy and they're gonna need a reverse total shot replacement?
John Kuhn:
Yeah, so that's a very interesting question. I don't know, I have a good answer for you. Okay, so we know that in natural history studies about half of rotator cuff tears will progress, right? So again, if you look at the United States, we have 22, I think it was 26.2 million people we estimate have rotator cuff tears. That means half of those people, 13 million will progress. We still only operate on 500,000 rotator cuffs per year in the United States, which would be about 5% of that 13 million. So for most people, progression doesn't lead to trouble. I think the issue is the rate of progression, right? So if it progresses very slowly, the tes miner can get larger, you can develop better scapular mechanics and you can compensate. The subscap will get larger, they'll hypertrophy and you can compensate for this slowly progressing rotator cuff tear. But in our clinics, we see people that are disabled that have massive tears, pseudo paralysis, giant tears when they're young and have a lot of issues.
John Kuhn:
And that's, that's who we see in clinic. And so how do you, how do you resolve that? How do you consider that? And the way I've come to to think about it is this, I think the majority of people have what I call an incidental rotator cuff tear. They'll come into your office with shoulder pain, no history of trauma. They've got an MRI and the MRI shows a full thickness rotator cuff tear. And for 70% plus you'll put 'em into physical therapy and they'll get better and they'll be fine. And that's because the tear really wasn't the issue. And they had other issues that physical therapy can address like a tight posterior capsule with internal rotation deficit, scapular dyskinesis, things like that. But I do think there's a small subset of people who are genetically predisposed to have rapidly progressive rotator cuff disease.
John Kuhn:
And if you look at features that predict progression, there's a lot of things in the literature, but the odds ratios for first degree relative are huge. They're like four, 4.3 or something like that. So I think there's a small subset of people who have this genetic predisposition to have rotator cuff disease. They're more likely to have more rapid progression, which will lead to more symptoms. Progression is statistically associated with symptoms. Rapid progression is associated with worse symptoms. US Mayer demonstrated that. So I think there's a, like I said, a small subset of people who are genetically predisposed to their rotator cuffs wearing out rapidly. And I call those consequential rotator cuff tears as opposed to the incidental rotator cuff tear. That's who we see in clinic. Not everybody we see with shoulder pain falls into that category. I think most people we see with shoulder pain would get better with physical therapy.
John Kuhn:
Maybe it's 70% would get better with therapy, but there's still the 30% in our clinic that have a problem. And sadly, I'm not convinced that fixing that surgically changes the natural history. It might, you know, there is some evidence to suggest that it might, but there's also evidence to suggest that it won't. And we do know that well, fixed rotator cuff tears can fail in about 25% of people. That's, those are the people I worry about because it's a genetic, biological problem that the best sutures in the best anchors in the world is not gonna address. And I think at some point we're gonna have to have a genetic test and we'll know the genes. People are looking at this right now. We'll know the genes where you'll do a blood test or spit into a cup and you'll know, oh, you have this profile.
John Kuhn:
You're at high risk for having a consequential rotator cuff tear. We have to figure out what to do. And so your question about the 40-year-old with a full thickness rotator cuff tear, I would worry that 40-year-old is actually in that group of consequential rotator cuff tears. The, the prevalence of rotator cuff disease in people in their forties is very small. And so I think that if you see somebody with already developing a full thickness tear in their forties, they may be in that category and you can fix it and you might be able to change the curve. But I think ultimately their tear will fall apart again. And so one of the things I've been doing, which I have no evidence to support this, is level five evidence, is if I see somebody who's young and has a big tear, that's the person I even might augment the repair with some graft tissue because their own collagen is not very good.
John Kuhn:
And if I use a sheet of donor collagen, I won't mention any makers, but they make dermal collagen or other collagen products, I might be able to change their natural history better than if I just fix the rotator cuff. So I, you know, it's, it that still remains a problem for us. And we s we in, you know, in the world of shoulder surgery, we talk about what do we do with these massive tears? Well, you could do tendon transfers, you could do grafts, you could do partial repairs. You know, there's a million things we can do, which means we haven't figured out the right thing. And that's, those are the people that create trouble for us. Those are the people that are consequential rotator cuff tears. Fortunately, that's a very small subset of all the people with rotator cuff tears.
Jared Powell:
So I wanna talk about, so it's commonly believed that if you have a rotator cuff repair, that that tear should remain intact or it often remains intact. Then if it, if it doesn't remain intact, then that person will have a recurrence of shoulder pain. What's, what's your opinion on that? I, I've seen a lot of patients over time who have become quite obsessive about the integrity of their rotator cuff repair after surgery. And they think that they've re torn it, you know, within six to 12 weeks after and become very fearful and kinesio phobic and have these catastrophic thoughts. And they're going out and getting MRIs every other day, every other week. This is a true story 'cause they're obsessed with the integrity of the rotator cuff repair. And that's perfectly fine. I'm not, not blaming the patient there, that's probably what they've been told. But how tight is the relationship between a re tear of a rotator cuff repair and a recurrence of shoulder pain?
John Kuhn:
Well, that's a great question. And it's also interesting. It also suggests that the anatomy's not that important. There have been at least eight studies where they have looked at people at one year and gotten MRIs on all their repairs and looked at their patient reported outcomes, comparing people whose repairs remained intact to the people whose repairs fail. And they've been written up in one systematic review and one meta-analysis. One of my old fellows, Mike Kazam, was the senior author on the meta-analysis. And what they showed was the patient reported outcomes are the same. If you look at people whose repairs stayed intact and compare them to people whose repairs failed, the patient reported outcomes are the same. If you measure strength, strength will be better if the repair is intact. But if you're talking about pain function, the A SES score, any other score, it's the same.
John Kuhn:
And so again, it would suggest that for most people, the anatomy is not the issue. You repair their tendon, but then you put 'em into physical therapy after that repair. The repair failed. But the patients are doing great and that's the therapy that got them better. It wasn't the repair, the repair failed. So that's most people, and again, I think those are the incidental rotator cuff tears. There are some people we fix and they have symptoms afterward. It's not a lot of people, but it's some. And those are the consequential rotator cuff tears. And because they're progressing rapidly, I think. So those are still a challenge for us. It's like, okay, I fixed it once, it didn't work. What am I gonna do differently? Am I gonna throw graft on it? Am I gonna do a tendon transfer? Am I gonna do something different? And again, I don't know what the right answer is.
John Kuhn:
There's, there's probably seven different approaches to that patient and features like what does the patient expect? What are their expectations? What's their activity level, what's their function? For me, you know, long story short, I tend not to operate on people for pain. I can usually get their pain better with physical therapy, but it's, if it's a functional issue, that's a different story. And so for me, if they're weak or if it's a barber who can't raise up his arms and cut hair, those are functional problems. Those are people I'm much more likely to operate on.
Jared Powell:
I like that. We're gonna come back to that in the moment. You know, the ideal patient who you would consider operating on. I wanna linger for a moment, and I'm sorry to linger on this, but I think it's important on the rotator cuff tear progression. In one of your recent papers, and I'll link it in the show notes, you did a two by two analysis on the relationship between rotator cuff tear progression and the experience of shoulder pain. And you found that it was a likelihood ratio of about 1.7. Do you want to just explain that and sort of how trivial that likelihood ratio actually is?
John Kuhn:
Yeah, so you know, this is, this again comes from my colleagues at Washington University in St. Louis who've done amazing work. And they did a study where they looked at patients who had progression of their rotator cuff tears and correlated that with symptoms. And they did find a statistically significant association between progression of the rotator cuff disease and pain. But I took their data and I put it in two by two table. And the problem is, you have some people that progress and have no pain and you have some people that have pain with no progression. So you can't really use pain as a predictor of who's progressing and who's not. And the likelihood ratio is, as you mentioned, is 1.75, which changes the probability only a little bit. If someone who has a known cuff tear comes in and they say, I pain, it doesn't really change the probability that their cuff tear is progressing much.
John Kuhn:
So again, the symptoms are not robustly connected to the anatomy and what's going on with the anatomy. I would mention one thing, and again, this is something that's come to me fairly recently when we do these studies and we have, you know, all these patients, the problem is there's two groups of patients and there's so many people that have incidental cuff tears that it dilutes out the bad actors. And so in a study like that, it's like, well, you know, I'm not surprised that anatomy doesn't correlate because probably three quarters of the patients in your study had incidental rotator cuff tears. But it's that, how do we separate those out? 'cause What we really should be studying is the consequential people, the people that have cuff tears that are gonna progress and be bad actors because the other people I think we could do therapy and ignore. So I think that's gonna be the next step in, in our approach is to figure out who is who. And that will really help us a lot with our research and with our treatment.
Jared Powell:
If we just linger on this incidental cuff tear, do you have any advice, John, on what we should say to patients if they ask a question, will my rotator cuff tear progress over time? Will going to the gym make my rotator cuff tear progress quicker? Is my occupation making it progress quicker? Et cetera, et cetera, et cetera. Do you have any little bits of wisdom that you could tell us to pass on to our patients? 'cause It's a tricky question. You know, you can't predict the future on an n equals one level, but on average, what would you say? Well,
John Kuhn:
You, you talk about occupation, heavy labor is associated with progression. And that's pretty clear probably going to the gym and working out heavy is like heavy labor probably may be associated with progression. The way I would answer that patient, I would say about half of the tears progress for most people they don't even know it's progressing. Again, there's 13 million Americans out there with rotator cuff tears that are progressing and they're not coming into my office. Most of 'em are doing fine in our moon data. 10 years, the patient reported outcomes did not change, but we would expect that about half of those patients would've had progression of the rotator cuff disease. So for most people it's not gonna be a problem. But if your progression is happening more rapidly, then you might have more symptoms from that. And you may be one of these people that has a consequential rotator cuff tear and that could certainly lead to trouble in the long run.
John Kuhn:
We can fix that. We might be able to pro change the natural history, at least delay it. And it may do well. I don't know, but I, I don't think I would say that it definitely would change the natural history and you'll be fine the rest of your life. I think I, what I would say is I could repair it. If we get it to heal, you'll do great because you might be one of those people with a consequential rotator cuff tear. My repair may not heal, the tissue just may not be good and it may fail as time goes on. We just don't know how to predict who is who
Jared Powell:
Would you tell someone who is a regular gym goer or plays tennis or surfs or swims to stop that activity outta fear of progression of rotator cuff tear sizes?
John Kuhn:
I would not. I mean, people have to enjoy their lives and, you know, if he's a a surfer, he might get attacked by a shark tomorrow. You never know. So no, I would not restrain people's activities. Now the one exception might be, you know, people we see that take anabolic steroids that are powerlifters that are just damaging their body in multiple areas. They can, they'll have rotator cuff tears, pec ruptures, biceps ruptures. That's the person I might say, Hey, this is not good for you. But even those guys won't change. So I, I wouldn't change their activity, but I would just make them aware that they are, they may be putting their shoulder at risk,
Jared Powell:
Educate and inform and they can make the choice. Can I ask you quickly about partial thickness tears, John, what's your, I mean, I know the data pretty well. I think that there's a, not really a relationship between a partial thickness tear and the experience of shoulder pain on average. What's your thoughts on that and whether, you know, the rate of those changing to a full thickness tear over time? Do you ever intervene in a partial thickness tear or do you just think it's a, typically a sign of aging or something like that?
John Kuhn:
I think in the last five years I've operated on one partial thickness tear. It's interesting. So most partial thickness tears are a consequence of aging. You know, rotator cuff disease is a consequence of aging. It's very, they're very common in people in their forties. It might progress to being a full thickness tear in their fifties or sixties. And again, there's 26 million Americans in whom they have full thickness tears. They probably were partial tears, you know, 10 or 15 years before that. The other point I would make is I, we published, I published a paper that's in the Journal of Shoulder and Elbow Surgery called Adaptive Pathology. And it argues that in throwing athletes like baseball pitchers in the United States, the partial tear allows them to perform to play baseball. You have to get your arm into extremes of external rotation. It's very different than cricket bowling.
John Kuhn:
It's more like javelin throw the speed of the ball in a major league baseball pitcher correlates with the amount of external rotation they're able to achieve when they're in the windup, the capsule of the shoulder fails, which allows them to get into that external rotation. And we know that if we repair that anatomically, that pitcher will never be the same. They'll never pitch at the same level. So I, I make the argument that some of these partial tears are adaptive and allow them to play the sport that they wanna play, particularly in throwing sports. So again, I'm not a big fan of surgery for partial tears. I don't think it does anything. It's very, like I said, I, I can hardly remember the last partial tear that I operated on. Yeah. I don't know what else to tell you. There are people that operate a lot on partial tears. There are people that are putting graft material in partial tears trying to change the natural history. There are people doing all kinds of things, but in my hands, I just can't remember the last time I operated on a partial tear.
Jared Powell:
Yeah, good. No, that's what I thought. You know, those, you mentioned that baseball sort of stats and that's really fascinating. I think I've seen a bunch of studies where they take a bunch of baseball players and MRI their shoulder and like 70 to 80% of them have a partial thickness tear or tendinopathy or some sort of labral alteration or something. And they've got full strength, no pain, full function. And that's, you know, they're not just okay strength, that's top level elite athlete who can throw a projectile at a hundred and something kilometers per hour. It's crazy. Yes.
John Kuhn:
Yeah. And again, the, the argument I made in this paper is that that pathology is not pathology at all. It's an adaptation that allows them to throw. Totally.
Jared Powell:
Yeah. Good. Okay, perfect. I just wanted to, to ask the question about the partial thickness tear because a lot of the time they are overlooked in the literature actually, there's not a lot of advice on what to do with them. So I wanna talk about, you alluded to a moment ago the, not the ideal patient but somebody who you would consider operating on. So are there things that you look for, obviously you mentioned incidental versus consequential rotator cuff tear. That's probably something that you would consider. What about age, size of tear, location of tear, mechanism of injury do you operate? Would you be more inclined to operate on traumatic versus non-traumatic rotator cuff tear? Do you screen, I'm sure you do patient expectations, so on and so forth.
John Kuhn:
Yeah, so I, for me, the indications for surgery are this, they primarily relate to function, right? So a traumatic rotator cuff tear generally will have significant pain and poor function. And most traumatic rotator cuff tears are high energy injury. We're talking about the real traumatic cuff a VI think those need to be fixed and need to be fixed relatively quickly before the normal muscle starts to atrophy to get the best outcome. There are some patients that have acute on chronic rotator cuff tears. So they had a preexisting rotator cuff tear, had a relatively mild injury, a fall from a standing height, had more pain and lost function. It's hard for us to know how much of their tear on their MRI is new and how much of it is old. We're trying to correlate that hopefully with machine learning to give us some idea about your tear is enlarged 2% or 6% or 10%.
John Kuhn:
And we're starting to look at that. Now what I'll do is I'll have somebody try therapy for three or four weeks and have them come back and see me. And if pain is significantly better and their function is returning, then they're gonna do fine with non-operative treatment. If they're not a whole lot different after two or three weeks or four weeks of physical therapy, I'll sign those people up for surgery. 'cause That's how I predict if they're tear enlarged significantly and they've lost function and then there's the chronic tears that have no history of trauma. And for those people it's function that drives me to do surgery. Like I mentioned, for the most part, I can get their pain better with physical therapy and we can talk about the biceps a little bit, but I can get their pain better with physical therapy for the most part. And if not, there's no clock ticking. I can try therapy and if it doesn't work, then we do surgery. But if they've lost function, the therapists are very, very good at doing what they do. But if somebody has significant weakness, even if you strengthen the Terrys minor as much as you can strengthen it, you're probably not gonna gain a whole lot of function out of that. So, you know, if if somebody has functional loss, I'm more inclined to recommend surgery for that patient.
Jared Powell:
Yep, that makes sense. John, I wanna ask you about the etiology of a rotator cuff tear. And we've talked about age a number of times and we can accept, I think that that is the, the number one predictor of, of developing a rotator cuff tear. If you live into your eighties, there's a pretty strong chance that you're gonna develop a rotator cuff tear. What are some other causes out there that are associated with the development of a rotator cuff tear? Can we say with confidence that it's a multifactorial pathology with many things influencing it? Or do you think there's a singular cause out there that we're still hunting that we can find and ultimately intervene incorrect?
John Kuhn:
Well, I think that's a good question. There are a lot of things that have been correlated with the presence of a rotator cuff tear. There's a million things heavy labor is is one that has fairly high odds ratios, a genetic predisposition. So a first degree relative is very strong. A second degree relative is strong. Third degree relative, not so much. So that's a big feature. Smoking, hyperlipidemia some people have looked at vitamin D levels. There's, there's a basically a million things that people have looked at and they probably all have some influence on developing a rotator cuff tear. But for me, the, the family history is probably the strongest predictor.
Jared Powell:
What's your thoughts on shoulder impingement? Subacromial impingement causing rotator cuff tears? Obviously Charles near in the seventies said that 95% of rotator cuff chair tears were due to attrition of the rotator cuff underneath the acromion. I think we've changed our tune on that over time. Been some strong RCTs come out sort of challenging the notion of of shoulder impingement. What's your thoughts and opinions and hypothesis around that? Yeah,
John Kuhn:
You know, I'd like to tell the story. When I was a resident, I thought I knew what impingement was and then I went off to do my fellowship with Rich Hawkins. And when I finished my fellowship, I had no idea what impingement was. So I got dumber after my fellowship. you know, near described is a concept trying to describe how the pathology occurs. And I do think there are some people whose rotator cuffs impinge on the acromion. And you can look at the acromion arthroscopically and see that there's fraying and it's worn and there's, and that happens. But the question is why does it do that? And the answer is probably more related to three things. A tight posterior capsule, which will change the mechanics of the shoulder and cause the humeral head to rotate up and impinge scapular dyskinesis. So the acromion then drifts down and becomes a feature that could impinge and rotator cuff strength.
John Kuhn:
The external rotator and rotator subscap tears an infraspinatus, which if they're weak, the humeral head may sit up higher. Those are all things, physical therapy will get better. And you know, near, if you really read his work carefully, he would make people do therapy a year before he'd offer 'em a decompression. Again, I think, I don't really know how to describe impingement. You know, if I bring your arm up like this and pinch it, it's gonna hurt. Is that impingement? I don't know what is causing that pain. I don't know. But if I see that you have a type posterior capsule and see that you have scapular dyskinesis and I do the scapula assist test described by kler and their patient's impingement, pain goes away. Well that patient's gonna get better with therapy. And that doing that test in the clinic helps confirm that therapy's gonna take care of it.
John Kuhn:
So I like to do that test in the clinic. So does impingement cause rotator cuff tears? You know, a lot of partial tears start on the articular side and I can't understand how an acromion can cause that. So I don't know. It's definitely, as you've mentioned, it's definitely a process of aging. The older you are, the more likely you are to have a rotator cuff tear. And so I, I don't think of it as impingement. I, you know, I don't know. It's a good question. I guess if you're exposed to sun, you might get more wrinkles and you can think about wrinkles as a process of aging. So maybe there's something to it, but I don't know. Yeah,
Jared Powell:
No, no, that's good. 'cause There is uncertainty around it. So I don't think, I wasn't looking for the, for the final solution, I just wanted your thoughts on it. And I think there is a, a ton of uncertainty about the role of subacromial impingement, shoulder impingement syndrome, whatever you want to call it in its sal role in generating a rotator cuff tear, I think. And then the other question we have to, to ask John is also, you know, what's the role of a subacromial decompression surgery in treating someone with, you know, a hypothesized a shoulder impingement syndrome if they've got a positive Hawkins Kennedy, and, you know, we've got those placebo controlled trials that have come out challenging the role of that over the last five years, which is interesting. Which leads me on to my next thought about, John. Are you aware of the placebo controlled trials that are underway comparing rotator cuff repair with a sham surgery in, in those with a full thickness rotator cuff tear? And, and what do you make of them?
John Kuhn:
I think that's a really difficult study to do. Yeah, I mean, my moon group collaborated with a, a number of other surgeons and something we call the ARC trial. We actually finished collecting patients, but we did a randomized trial comparing physical therapy to surgery for rotator cuff tears. And there have been a few out of Europe as well, but this is a fairly large one. But to do a sham surgery, you know, if I'm a patient, I would not sign up for that. I mean, I just wouldn't look, why would you sign up to have somebody put a scope in there and not do anything? So I think if that trial gets done, congratulations to the scientists because I don't think in the United States we could do that trial. I don't think patients would agree to sign up for it. Yeah,
Jared Powell:
Yeah. There's two underway at the moment. There's one in Australia and one in in Scandinavia. They're always out of Scandinavia, these placebo controlled trials. And Ian Harris, the surgeon from Australia is leading the one here down under, and it's gonna be interesting to see. Yeah, I'm with you. If, if I was in pain, I had a radiologically confirmed full thickness rotator cuff tear, I'm not sure I would consent to perhaps being in a placebo sham group.
John Kuhn:
Yeah, I think he, I think he's gonna have trouble enrolling people, but he, maybe the Australians are willing to do be Guinea pigs. I don't know, in the United States it would never fly.
Jared Powell:
Interesting. Do you have any, any very preliminary thoughts on, on how the data may turn out? What would be in your hypothesis though? Well,
John Kuhn:
It depends what outcome measures they're using, right? So if they're looking at something that has a phenomenon for strength or has a measure for strength, then surgery will be favored, right? Mm-Hmm. So the constant scores weighted about 25% strength. They're supposed to take a fish scale and measure strength. So if they're using the constant scores or patient reported outcome measures, it may show a benefit for surgery. If they're using the visual analog scale, the A SES score, the WAR score from Canada, any other score that doesn't actually measure strength, they probably will be the same.
Jared Powell:
Yeah, I think from memory, and I just looked at it this morning, they're using the shoulder pain and disability index, they don't think has a strength function in there. So Yeah. Interesting.
John Kuhn:
Yeah, it does not, so I, I would pick that the, they're not gonna show a difference, but again, if they use something that measured strength, it would favor surgery. You know, moose Meyer's studies are like that. He's done randomized trials. He does have data that would favor surgery, but he uses the constant score, which measures strength and the other thing, and, and he's a great researcher and I, I think his work has really helped us a lot, but a third of his patients had work on their biceps if they had surgery. And you can't do that in the non-surgical group. And so that may influence the outcomes as well.
Jared Powell:
Sure. Yeah, those mosmeyer studies are, are really good. He's got the 10 year follow up, doesn't he, versus rotator cuff repair versus non-operative treatment. I'd advise anyone listening to go and read. I think he's got a one year follow up, a five year follow up and a 10 year follow up, which was really fascinating to watch. And I think at 10 years it really did favor the surgical group, didn't it?
John Kuhn:
It did. And again, that's the data that might suggest that you might change the natural history of the disease by doing the surgery, but we just don't
Jared Powell:
Know. Yeah. Also confounded by the biceps work too. I wanna ask your thoughts on injections, John, quickly, I know I'm taking a lot of your time here. Can we mention briefly corticosteroid injections, whether you use them, what's their role? What about PRP? What about stem cells? Anything else here? Any other potion that you like to inject to help people?
John Kuhn:
Yeah, so the way I think about corticosteroids is that it is a catalyst for therapy, right? So the steroid effect is not gonna last. It's gonna settle the shoulder down and make it feel better for a few weeks. But if you go in there and measure how much steroid is left, after two or three weeks, it's all gone. Right? We have something in the United States you may have it in Australia called a balloon arthroplasty, where they actually put a dissolvable balloon in the shoulder between the acromion and the humeral head. It's it's polyglycolic acid or something that dissolves after about six weeks. That's a catalyst for physical therapy. Those patients seem to do well, and I think if you can take away their pain, they're gonna be better at doing their physical therapy. Right. So I, I look at an injection as a catalyst.
John Kuhn:
If somebody's struggling in therapy, I'll try an injection. I don't think it's a cure for the problem. But I do think it's a, I do use it as a catalyst. PRP is interesting. There is some data with repairs that suggests that PRP may actually help heal repairs better for smaller or medium sized terrors. And the data's good data. So I'm not opposed to people using PRP for repairs. I really don't think it does anything if you're treating it non-operatively. I have strong feelings about stem cells and my feelings are this, we would like to take a pleura potential cell and make that grow new tendon and make it grow new cartilage or make it grow whatever the patient needs. But we don't know how to do that. And so what I tell, you know, in the United States, they're not FDA approved. There are people administering them, they're charging a lot of money to do it.
John Kuhn:
But I tell people it's like if you wanted to build a house and you have a lot and you had a dump truck with all the two by fours and, and sheet rock and nails and screws and shingles, and you just dumped it on the lot and you hope a house gets built, that's what's happening when you inject stem cells into an area. It's just, we're not able to figure out how to make it turn into a house yet. And so I'll tell patients that in clinic, I, I'll tell 'em, don't waste your money because we're not there yet with stem cells someday we may be, we may be able to figure out how to make the cells do what we want them to do, but right now you're just dumping building materials on a lot and it's just not building a house yet.
Jared Powell:
Yeah. Great. That's a great analogy. I've heard another analogy where it's like trying to bake a cake and you just dump all the ingredients into a bowl and just hope it comes together to make a beautiful cake. There's a, there's a fair bit more involved. Okay. Can I ask you about corticosteroids? Are you less inclined to use the mini younger patient given the data on the deleterious effects of a corticosteroid injection on tendon health? Or you're not too concerned? What's your thoughts on that? Well,
John Kuhn:
If the, if the injection is actually in its space, I'm not concerned. Right. So most of the data, the data that showed corticosteroids to have a deleterious effect on tendons, they were injecting it into the tendon material, which I think is not a good practice. You know, and, and judiciously if you do two or three, maybe four injections per year, I don't think you're doing a lot of damage to the tendon. But I wouldn't do more than that.
Jared Powell:
Cool. Are you working on anything interesting right now? I know you've probably a busy man and got, got tons going on. Can you, can you give, give any little previews as to what we should expect?
John Kuhn:
Well, you know, the randomized trial, we've just finished collecting our, enrolling our last patient, just the ARC trial. Well this, yeah, so this is a randomized trial. We call it the ARC A RC ARC trial. And it is comparing non-operative treatment with surgery for rotator cuff tears. And we have over 200 patients enrolled and we've stopped enrollment. And so in about two years we should have some data to report and then we're gonna follow those patients for a long time as well. And the other thing that's really exciting is one of my former fellows, Carolyn Hetrick, is taking our moon group, you know, our moon group, the way I think about it is we've created this great research enterprise and it's a tool and let's use this tool to look at other things. So she took it and ran with it, looking at patients who have had instability surgery, and we've got over 1500 patients who have had surgery for instability. And now we have two year follow-up on those patients. You're gonna see a lot of papers coming out from our moon group on shoulder instability surgery results, which is kind of interesting. I don't wanna spill the beans, but there's some surprisingly bad results with, with instability surgery.
Jared Powell:
Wow. I can't wait. Is this for just primary anterior dislocations or multi-directional or all of the above?
John Kuhn:
We have all the above. Most of our cohort, as you might imagine, are anterior instability patients, but we have over 300 patients with posterior instability and we're gonna get some really good data outta those patients as well.
Jared Powell:
Right. I think that's gonna be so interesting. That's it really. The, the shoulder instability patient in physio practice and in surgical practice is really challenging, especially the multi-directional and posterior instability patients. That's gonna be fabulous work. Where can people find you, John, are you on social media at all? I know we can find your work through the Moon Shoulder Group website. Yeah,
John Kuhn:
I'm not, I don't really, I'm old. I don't really participate much in social media. I'll be participating more this January I take over as the editor in chief of the Journal of Shoulder and Elbow Surgery. So I will be out there a little bit more. In fact, I may be doing some podcasts for some of our, our research that gets published. So that'll be interesting. Hey, I would say if you're interested in the work, our website is moon shoulder.com. We have all of our rehab protocols there. We have our research there and the contact information of people all over the United States who are part of our group.
Jared Powell:
That's awesome. Yeah, I would strongly advise everybody listening to go and check out that website. The, it is a treasure trove full of goodness, and you've really done some great work over the last 20 odd years. So I would like to thank you for all that work that you do and you will continue to do. It's been really helpful for a lot of people out there. So, cheers mate.
John Kuhn:
Thanks, Jared. Thanks
Jared Powell:
So much for coming on and hopefully we can chat again. I'm gonna get you back on the show in two years, John, and we're gonna talk about the results of the ARC trial, if that's okay, because I think that's gonna be fascinating.
John Kuhn:
I'd be happy to do that. Thanks.
Jared Powell:
Cheers, mate. Bye-Bye. Thank you for listening to this episode of the Shoulder Physio Podcast with Dr. John. If you want more information about today's episode, check out our show [email protected]. If you liked what you heard today, don't forget to follow or subscribe on your podcast player of choice and leave a rating or review. It really does help the show reach more people. Thanks for listening. I'll chat to you soon. The Shoulder Physio Podcast would like to acknowledge that this episode was recorded from the lands of the Ang people. I also acknowledge the traditional custodians of the lands on which each of you are living, learning, and working from every day. I pay my respects to elders past, present, and emerging, and celebrate the diversity of Aboriginal and Torres Strait Islander peoples and their ongoing cultures and connections to the lands and waters of Australia.
