[00:00:00] Welcome everyone to our first BJJ podcast of 2023. I'm Andrew Duckworth and a warm welcome back to you all from your team here at The Bone & Joint Journal. We hope you've all had a lovely and restful festive period with family and friends, and we wish you all the best for the year ahead. As always, we'd like to start by thanking all of you for your continued comments and support for our podcast series and all its knowledge translation work, as well as a big thanks to our many authors and colleagues who take part.
Our podcast continues to focus on papers published each month here at the BJJ, as well as our accompanying special edition podcast series, which will be scattered throughout the year. So today I have the pleasure to welcome back Professor Matt Abdel from the Mayo Clinic in Rochester to discuss their paper entitled, 'Spinal versus general anaesthesia in contemporary primary total knee arthroplasties', which was published in the November, 2022 edition of the BJJ.
Welcome back, Matt. It is absolutely great to have you with us today. Thank you so much for taking the time. Yeah. Thanks for having me Andrew. Thanks for welcoming back and happy New year to you, to your family, and to all of our listeners at the journal. Thank you, Matt. That's great. It's great to have you back.
So moving onto your paper, Matt. The, you know, the aim of this study was to investigate and compare some [00:01:00] outcomes including pain control, length of stay, and complications associated with spinal versus general anaesthesia and primary TKAs from a, you know, as we know, a single high volume academic centre.
So, Matt, as a background of the study for our listeners, can you give us a brief overview of the, of the state, of the current literature in on this topic and what maybe caused you to look at this particular question in the study. Yeah, it's a really good question, Andrew. And so I would say right now in contemporary hip and knee arthroplasty, there's a lot of debate on general anaesthesia versus neuraxial, particularly spinal anaesthesia for primary and revision hip and knee arthroplasty.
And you'd say, why is that the case? Couple of things. Number one, Covid. The real reason I started thinking about this paper was when we were shutting down, there was some data early indicating that general anaesthesia was gonna be worse for the anaesthetist when taking care of covid positive patients.
So we thought if they could keep their mask on, we could do surgeries with a spinal, could we mitigate that risk? So then I started thinking about looking at our data, number one. Number two, there's debate in [00:02:00] North America, it's very popular now to do same day or outpatient total joints. And whether that's an academic medical centre or a free standing ASC, there are pros and cons to both general anaesthesia and spinal anaesthesia.
And so these two things were coming at the same time, both this desire to have same day outpatient surgery for the a s surgery for the ASC, and contemporary practice as well as the covid pandemic. And I said, what's our experience at the Mayo Clinic with general anaesthesia? Versus spinal anaesthesia.
And I picked a clean group. I said primary total knee replacements. That's really nice overview, Matt. Like you say it's interesting what sort of prompts you to look at these questions. Yeah. And Covid has done that with a few things like this. And actually it's amazing the number of relatively simple questions in
many ways, we just we don't know the answer to or we haven't looked at. It's interesting, isn't it? Yeah, it's interesting and you know, I thought about it for both, you know, hip and knee. And most of us still utilize it to keep his position for the hip, in which the anaesthesiologist has more concern if they need to intubate with the spinal.
And so [00:03:00] for a knee, almost all of us do it with the patient supine. And so our anaesthesiologist, as you could see in the study, were very, very keen on doing spinal anaesthesias in a recent period of time, even in our revision practice, knowing that the patient's supine, if they needed to intubate, they could safely.
Yeah. And so this was our first attempt to say, how do these patients fair with very objective outcomes, though we looked at. Absolutely, absolutely. And we'll come onto that. And just before we do, come onto the, the, the detail of the study about, you sort of alluded to it there, what, what do you feel is the, the, the current trend across the US and has that, has that changed?
Do you know where, where do you think people are at the moment in terms of their favoured anaesthesia? It's a great question, Andrew. I would say just 3, 4, 5 years ago that it was split. General anaesthesia, the patient has no motor block. They can get up, walk away, they can get a neuro exam right away, and that's the way to go.
And then there was a subset of us saying, 'Hey, spinal anaesthesia's the way to go'. It's better for the cardiopulmonary system. They had Le, Le need less oral morphine equivalents. They have less nausea [00:04:00] and vomiting. Less urinary tension, less pulmonary issues. And I would say over the last three to five years, that pendulum has started to swing.
I would've said it was 50/50 about five years ago, I'd say it was probably 60/40 in favour of spinal a couple years ago, and now I'd say, I surmise it's probably 70 to 75% of us prefer some sort of spinal anaesthesia. That's really interesting. That's really interesting and and we'll come onto that trend in with results from the paper as well in more detail.
So if we do move on to the, the study itself and the design, this was a retrospective view of patients undergoing primary TKAs. And you took a period from 2000 to 2016, you using the Mayo Clinic Institutional Total Joint Registry. Obviously primary TKAs were included, but you excluded any TKAs performed for neoplastic causes.
And so during this study period, there were 17,690 primary TKAs in just over 13,000 patients with a GA used in JU about 52% of cases. And a spinal in 48% of cases. So Matt, maybe just for our listeners, and maybe if they're not familiar with the, the [00:05:00] Mayo Clinic studies, can you as a brief overview of the baseline data, it sort of has that's available in the joint registry?
Yeah, the joint registry is impressive. So at Mayo Clinic since 1969, we've captured every primary revision hip and knee arthroplasty done at the institution. We follow patients preoperative three months postoperative, one year postoperative. Two years, postoperative, five years and every five years thereafter until revision, reoperation or death.
Wow. And within that, we get all the demographic data that you'd want on the patient. We get all of the surgical and anaesthetic data that you'd want on the patient, including operative time, tourniquet time, drain use, all of those medications used in the perioperative period, and then the standard orthopaedic outcomes.
Yeah, we. Any revision, any reoperation, any complication, and that includes things like postoperative nausea and vomiting, oral morphine equivalent usage, very important features when you're talking about spinal anaesthesia versus general anaesthesia. We also have things like altered mental [00:06:00] status, delirium or dementia, exasperations, ICU admissions, and so all of those factors were very helpful with our registry when putting up these two very
contemporary techniques of spinal versus general anaesthesia. Ab absolutely. No, that's, that's really impressive. The amount of data and the completeness of data that the, your registry collects and, and you've sort of alluded to it already, but what were the specific outcome measures you looked at for this study and, and how did they sort of, how were they sort of analyzed?
Yeah. So a couple of things. I should take a step back and say that you hit it right at the end. The analysis was the key here. Yeah. Because there is a bias, that maybe you're sicker, more frail patients get general anaesthesia or maybe surgeons that surmise the case would take longer, said, Hey, give 'em a general anaesthesia
versus spinal. So we did an inverse probability treated weighted model, which accounts for all these variables, including things like index diagnosis, the actual operative time, the actual tourniquet time. So we accounted for many of those factors as possible to take out that [00:07:00] surgeon bias, to take that, take out that anaesthesiology bias.
And what we were interested in with factors that you and I as clinicians are interested in. Did they use more or less oral morphine equivalent? Was there pain better, worse, controlled? Were they in the hospital longer or shorter? Did they have more or less altered mental status and post-operative nausea and vomiting.
What were the ICU admissions in the groups and what were the 30 and 90 day readmission rates for orthopaedic or non-orthopaedic reasons? And so that's, those are all the factors we looked at. And the data was, in my mind, quite impressive when we corrected for all those factors, the benefits of spinal anaesthesia over general anaesthesia with a very controlled
weighted model. I agree. I I think that that was the thing that struck me when I read this paper is I think I, I totally agree with you that I think the first thing you think of, well, there's just a natural bias there with the general anaesthesia. They're gonna be the sicker patients, like you say, or more complicated procedures.
And when you, you, by using that inverse probability of treatment weighting model and that approach, it has controlled for all those factors to [00:08:00] actually give us a proper, a proper comparison or two. And I think that was the, the real, one of the real big strengths o of, of this, of this study. Yeah. And if I compare it to other, there's data on this topic, of course, yeah.
But if I compare it, it's the fidelity and completeness of the data set in large numbers combined with this model that accounts for everything you could think about. I mean, we're talking even about the actual operative time, not I think it's gonna be a longer case. Give it a general, we actually had the operative time and the tourniquet time and matched those and weighted them so that we were looking specifically at the only variable what we
we hadn't controlled for, which is the type of anaesthesia. Absolutely. And I think that's the, that's the thing, isn't it? A lot of the particularly registry database out there just don't have that granularity of data that the, that your joint registry has. So you can't control for all those factors that you have done.
I think that was, that was a real striking point for me. So if you move on to the results just to iterate, there were just a 70,000 primary TKAs over the study period. The baseline characteristics as will come to a very similar between the cohorts with an overall mean age of 68 years, 50, [00:09:00] 57% were female and the mean BMI
was just over 30. So Matt, could you maybe give us a list, listeners a brief overview? I think one of the first interest things, and we've alluded to it already, how the use of of the general responses are changed over the study period. Yeah, it's a, it's a really good question, Andrew. And what, what we did novelly in this paper is we actually grafted out, we said, cuz I was intrigued.
I wanted to see are we using it more or less? When was the transition period? Yeah. And we saw, interestingly, it was kind of, Down, up, down, up, down. But in 2014, there was a very set inflection point when we started utilizing spinal way more than general anaesthesia in our surgical practice. And I think a couple of reasons for that.
I think number one, the technique by our. Our, an anaesthesiologist got better. They were so used to doing spinal anaesthesias, number one. Number two, medi different medications were available that mitigated the risk of transient neurologic symptoms. So they were more comfortable with the medications we're using.
And finally, and maybe most importantly. We as orthopaedic surgeons, particularly knee [00:10:00] arthroplasty surgeons, got so refined at executing the procedure in a set period of time with contemporary techniques and contemporary implants that we, the anaesthesiologists had a very cognizant and logical time period.
They knew that reproducably and reliably these procedures would take a set point of time. So spinal anaesthesia took off. Yeah. And now, as you could see in our paper, it's 60, 65, approaching 70% of our primary knee arthroplasty patients at Mayo Clinic, Rochester are getting a spinal anaesthetic. And the ones that are contraindicated are hard contraindicated.
Robust boney, lumbar spine fusion with instrumentation where there's nowhere to place the needle. Yeah, exactly. No, absolutely. And I think like, as you say in, in figure one, I think is very telling. There's just that real cross and change, isn't it? About 2000 12, 11, 12, and they, they, they just completely, almost flip almost instantaneous over the following years.
And so in, in terms of your outcomes, Matt, what I suppose what we'll sort of take it sort of chronologically, what did you find in terms of sort of the in-hospital pain scores and the type of analgesia that was required? [00:11:00] Yeah, it's, it's really timely. A couple of things I mentioned earlier, the Covid pandemic and us wanting to free up the hospital beds.
Yeah. But I should also say that we have an opioid crisis and the whole world is work working on mitigating opioids. Yeah. And we're also full in our ICU beds and so we're trying to mitigate ICU admissions. And so I thought to myself, my goodness. The largest volume procedure done at the Mayo Clinic and a one intervention doing a spinal versus a general mitigates substantially and significantly oral morphine equivalents.
Checkbox. Mitigates ICU admissions and altered mental status. Checkbox. Decreases our 30, 90 day readmission rates we showed in the study. Checkbox. Mitigates gives better pain control to our, to our patients. Checkbox. And so this is one intervention in which you could free up hospital resources.
You can give better patient care, you can mitigate the use of opioids and what most hip and knee arthroplasty surgeons think about; decrease 30, 90 day readmission rates, as well as any revision and any [00:12:00] reoperation. Which is remarkable to me. Absolutely. And like you say, the implications, you know, particularly looking at something for like our system as, as much as yours, but the, the cost savings there is just, you know, and particularly with that being the high, the high volume procedure that it is, like you say, must be, must be so large.
And so it, it, and, and so related to that, you, you also found differences as well in terms of sort of length of stay in hospital comp, in hospital complications as well, didn't you. Yeah. We found both. Now you might say, well, significantly decreased length of stay cuz the stats showed that, was it clinically relevant?
Well, it was less, yeah. But you know, but it was, you know, half a day, a quarter of a day there. Yeah. And then the in-hospital complications were decreased as well. Yeah. And so these are things we're talking about in the early post-operative period, the first 30 days. And the first 90 days we're able to mitigate.
And maybe Andrew, we haven't talked about it, nothing was worse. Yes, yes. We found substantial list of things that were significantly improved, but definitively nothing was worse. Yeah, absolutely. Yeah, absolutely. And in terms of sort of complications, revision, there was all, you know, amazingly there was still, [00:13:00] there was also a difference in that as well, wasn't there?
Yeah, there was. And so you might in A critique of the paper might be like, yeah, you have this beautiful model if you have count for everything, but still you have not captured the ethos that some of the worst sickest patients got a general, and I, I, I'm cognizant of that limitation. Yeah. But the fact remains that I think there is a physiologic
imbalance that occurs with postoperative nausea, vomiting, syncable events, orthostasis, falls. Yeah. Weakness and a stress on the system, cardiopulmonary system that may lead to syncable events, falls, and thus orthopaedic complications or may lead to cardiopulmonary demise in the early postoperative period, giving you that ICU admission and other things like that.
Yeah, so I think there's probably both a little bit of bias to the. But real physiologic changes that happen with that general anaesthesia that our spinal patients do not receive. Absolutely. Absolutely. So I think maybe if we go into, into the sort of the, put it into context, Matt, you know, the strengths of the study.
I, I agree with you. There are a really clear, you know you know, a very large [00:14:00] single institution study very robust analysis. And I think that like we've, we've said that again, but I think it's worth saying. You know, it, the, that robustness of that analysis and controlling for all those factors has really added a lot of weight, I think, to, to the data that's already out there.
And it, and as you say, it clearly demonstrates the advantages of spinal over general anaesthesia and like, say nothing was worse. They were all, they may not be significantly or maybe clinically relevant, but they're better. And whether that be improved subjective pain scores, reduced inpatient opioid utilization as and as well as complications.
So, Matt, What do you feel are the key take home messages moving forward? And, and, and how do you feel it fits with the current literature? I feel like with contemporary literature, it fits and in fact, I would say it leads a charge on contemporary literature due to the fidelity completeness of the data and the modelling.
And I'd say what has it done for the practice? I'd say three things. Number one. Most of us now in the preoperative consultation will actually educate the patient, not about the hip or knee replacement in this study, the knee replacement that we're doing in the surgical technique and the [00:15:00] complication profile.
But I'll often say to them, you're gonna meet with your anaesthesiologist in the morning. My strong preference if the anaesthesiologist agrees and sees no strong contraindication is for spinal anaesthetic, and it is amazing to me, Andrew, how many patients are scared because 30 or 40 years ago that an epidural spinal for something that was totally unrelated with archaic techniques and that specialty in itself has evolved.
And so I give them some education that, these patients do much better from altered mental status, ICU admission, 30 day, 90 day readmission. All of the different or oro morphine equivalents. And it makes the job for the anaesthesiologist the next morning. So I have taken that on myself as a risks, benefits, alternatives to do in the consultation with the patient.
Number one. Nice. Number two, I have seen. My patients post-operative in rounds and they're happier. Post-operative nausea, vomiting, decreased haemodynamic changes, decrease that, thus less fluid overload, less urinary retention. They love feeling controlled, not institutionalized, not like [00:16:00] a sick patient.
But they feel like a healthy patient. Waist above they feel good. They're with their family. They're conversing. Yeah. And now we use mepivacaine spinals and we publish that as well. That's wrap it on. Wrap it off. They have motor sensation. People like to feel their legs. They do not like that sensation of the total motor blockade.
With the wrap it on and wrap it off. And so those have been the big things that I've taken away from this. Yeah, no, I think that's, and it's really nice to see how it's put in context of your practice, Matt, and how that has evolved. That's really interesting. Well, I mean, but go moving on from that.
So you alluded it to, to already, what do you. What do you feel the, the limitations though are of the, of the study that you would particularly would want to highlight? Yeah. The, the main limitation is the fact that even though we did this robust model with innumerable variables that we controlled for, with the model, there is still that
anecdotal surgeon sense this patient an anaesthesiologist sense that the sickest, most complex patients may need that. [00:17:00] So maybe those, that kind of general are the ones that had hardware that was being removed that we didn't capture in the registry, although we're pretty crisp on that. Or the surgeon was worried about some portion of the procedure, like dual incisions or, or something.
Something of that nature. Or the patient was medically frail on the way in. Although we tried to control that with ASA and Charleston Comorbidity and actually, I think as much as we've controlled for it, there's probably a touch of a bias still left in there. That's number one. And number two, we're very fortunate at Mayo Clinic our, and I'm not talking about the surgeons, I'm talking about our anaesthesiologist.
We have a very skilled group of anaesthesiologists that can deliver spinal anaesthetics. Very expeditiously and for a very controlled period of time. So there's not a lot of variability. They know how long the surgery's gonna last. The spinal lasts that period of time with minimal complications.
So we have a little bit of a bias and our other proceduralists in the room are anaesthesiologist. Yeah. No, absolutely. And that's very fair Matt, and a very fair balance of of, of how you interpret the findings. And I suppose maybe, [00:18:00] maybe my final question I think, you know, the, the paper speaks for itself, certainly for primary knee arthroplasty.
What are your thoughts in relation to revision knee arthroplasty? That's a really good question, Andrew. So we are, and have looked at the revision knee. I'll tell you, the hardest group is the revision hip because there is a bias on big surgery in the decubitus position. Yes. For revision knee. The data is very compelling as well.
Very compelling. Now, there are some, some, a little more deviation in that one because that's very hypers selected. Are you gonna do one component polyethylene exchange, two stage exchange? Is it gonna be a distal femur replacement versus just a simple revision? So there's much more variability in the surgical procedure itself, but we controlled by operative time.
So that's number one. And number two, again, the patients are in this supine position, so we had a little more bias to do it more recently, knowing that we had great control of the airway if we needed to do it. Yeah. But the data is very impressive in the revision knee setting as well. Maybe more impressive.
That's in interesting. And like you say there e even more probably comorbid and more elderly difficult [00:19:00] group to, to sort of to consider. So that's really interesting. We look, I look forward to reading more about that in, in the future, Matt, but, well, Matt, I think, I think that's all we have time for today.
So thank you so much for taking the time to join us and, and congratulations on a really outstanding study that has without doubt added to substantially to literature in this area. And it was, it was great to have you back with us. Yeah, it's great to be back, Andrew. Thank you very much and I hope you all enjoyed it.
Thank you. Thanks Matt. And to our listeners, we do hope you've enjoyed joining us, like Matt says, and we encourage you to share your thoughts and comments through social media and the like. Feel free to tweet or post about anything we've discussed here today. And thanks for joining us again. Take care everyone.