Dr. Andrew Sheean: Welcome to the Arthroscopy Association's Arthroscopy Journal Podcast. The views expressed in this podcast do not necessarily represent the views of the Arthroscopy Association or the Arthroscopy Journal. Welcome everybody, I'm Dr. Andrew Sheean from the San Antonio Military Medical Center. Today I'm excited to be talking to Dr. Aravind Athiviraham, who's an orthopedic sports medicine specialist at the University of Chicago. Incidentally, Aravind and I met each other, as we were both AANA traveling fellows last year. It's nice to reconnect with him this evening and talk about his paper entitled Pharmacologic Thromboprophylaxis Other Than Aspirin is Associated With an Increased Risk of Procedural Intervention for Arthrofibrosis After ACL Reconstruction. It was just published online in October of 2020. That was a mouthful of a title, Aravind, but thanks for coming on the podcast this evening.
Dr. Aravind Athiviraham: Yeah, thank you very much for having me back, Andy. I appreciate it.
Dr. Andrew Sheean: Before we get into the specifics of the study, this is a question that I like to ask guests of the podcast when they are here talking about interesting nonclinical studies, whether they be anatomic studies or registry-based studies, but I want you to take a moment to explain to the listeners how your group executed your study. This is not one of the first studies like this that you've published, and so obviously you have an infrastructure, or a machine for lack of better words, in place. How did you set this up in a way that allowed you to perform this study in an effective and expeditious way?
Dr. Aravind Athiviraham: It's a great question. I'd say probably the most significant factor is I have a great group of residents I work with at University of Chicago that are interested in sports medicine. I think just nurturing that interest has been really helpful. I'd like to acknowledge my co-authors on this, Charles Qin and Hayden Baker, who are both residents at the University of Chicago, who've done a great job with this and other studies.
On top of that, I think asking the right question is really important for any of these database studies. One really needs to understand the limitations of the database to avoid going down a rabbit hole, that you can do several weeks of research on a specific topic only to find out that maybe the database isn't the ideal method to do that. For example, I would say big picture concepts like overall surgical procedure trends or occurrence of rare but clinically significant complications such as blood clots, infections or complications, those are great things to look at in these database studies, versus when you're maybe looking at more patient reported outcome measures would be more ideal. Those are not as well suited. I'd say just understand the limitations and asking the right question would be important factors outside of having a great team around me.
Dr. Andrew Sheean: It seems like this is a fairly specific question that you guys set out to ask. What exactly got you interested in this topic specifically and compelled you to actually get into this registry and answer the question?
Dr. Aravind Athiviraham: I think one of the questions that came to me is, for example, I use aspirin in my own ACL group. As you know Andy, I also do total joint replacement as well. We recently converted from using oral factor Xa inhibitors with my total joint patients to using just aspirin. What I noticed is that there was a decrease in my rate of manipulation. Then that got me intrigued and I tried to see if there was something similar in the ACL literature just based on just overall rates of using thromboprophylaxis and whether or not using thromboprophylaxis was associated with increased risk of manipulation or stiffness. I didn't really find much information on that, so that was one of the factors that motivated us to look into this topic.
Dr. Andrew Sheean: Why don't you give us an overview of exactly how you went about investigating this topic, and then tell me and the listeners what are the one or two main take-home points that you want us walking away from at the end of this podcast about your paper?
Dr. Aravind Athiviraham: Sounds good. We looked at this database called the PearlDiver database, which had access to these large Humana claims dataset. We tried to identify patients that used thromboprophylaxis as opposed to patients that are already on anticoagulation preoperatively. Once we identified that, we followed these patients out to about 18 months after their surgery. What we're trying to figure out is which of these patients that had thromboprophylaxis or had increased risk of manipulation under anesthesia or lysis of adhesion when they underwent ACL surgery. In our database that we looked at, about 14,000 patients, and about 13,000 of these patients did not have any thromboprophylaxis. Of the about 500 patients that actually were prescribed pharmacological prophylaxis, what we found is that patients that had any factor other than aspirin, so for example, low molecular weight heparin, oral factor Xa inhibitors or warfarin were 2.6 times higher rate of manipulation under anesthesia compared to either having no prophylaxis or using aspirin alone.
Dr. Andrew Sheean: Interesting. What, if anything, surprised you about these findings? Anything got you scratching your head?
Dr. Aravind Athiviraham: One thing I was a little surprised was the low rate of thromboprophylaxis overall nationally for ACL surgery, which makes sense because the incidence of DVT/PE and those sorts of complications are pretty low, about 0.5%, but that did surprise me slightly. The other thing that surprised me is I was expecting to find a similar rate for aspirin and the other agents for thromboprophylaxis. We were surprised that we had such a stark difference between the two groups, where aspirin was more comparable to not having prophylax in terms of rate of manipulation versus there was an over two and a half fold increase when using a thromboprophylactic agent other than aspirin. I was surprised that there was a significant difference in the rate between aspirin and the other agents.
Dr. Andrew Sheean: What do you think is going on there? Do you think it's the people that are on the medications other than aspirin are setups, they've got something about their biology or their knee homeostasis, for lack of better words, that predisposes them to having these episodes of arthrofibrosis postoperatively?
Dr. Aravind Athiviraham: I think that's a good point. I mean, we did try to control for some of that by a regression analysis. For example, we try to control the Charlson Comorbidity Index, which is an index that has a variety of different factors like diabetes, cardiac disease, lung disease. We took that into account. We also took into account factors that have been shown to have a risk factor of [inaudible] manipulation under anesthesia such as a concurrent meniscal repair, time from surgery, whether it was within three weeks or after three weeks, as well as postoperative infection. We try to control for some of these factors, but again, within these database type studies, it's hard to control every factor.
Certainly there might be a confounder that we weren't able to control, but that being said, based on this study, I think one thing they could potentially take away is that a thromboprophylactic agent other than aspirin may potentially increase the incidence of postoperative hematoma, which in turn could increase the pro-inflammatory milieu, which is necessary for arthrofibrosis to develop. Maybe it is just the increased incidence of the hematoma that's contributing, but unfortunately there's no way to be certain with this design, but it does suggest that possibility, given that we've controlled for as many factors as we could in this study.
Dr. Andrew Sheean: What are you doing in your practice in 2020 right now? You do a fair amount of total knees, like you mentioned. Do the results of this study affect the way that you think about thromboprophylaxis in these patients in general, or maybe just in the high risk patients?
Dr. Aravind Athiviraham: Yeah, I think from the standpoint of my total joints, for example, I think that certainly it is my belief that we did the right transition, because like I said, I found that we decreased our incidence of MUAs without increasing the risk of DVT/PE complication. For example, for my ACL group, I continue to use aspirin. The study was suggested there's not an increased risk for MUA, so I'm going to continue doing the same scenario. Yeah, I think I'll continue doing the same thing, but for high risk patients, we usually consult with our anesthesia clinic and hematologists and try to get solicited advice from them as to what to do, but yeah, certainly for low risk patients, I think aspirin is a good approach, certainly for total joints, and in cases where surgeons already use aspirin, I think it's safe to do.
Dr. Andrew Sheean: How much aspirin are you using and for how long after surgery?
Dr. Aravind Athiviraham: I use a baby aspirin, 81 milligrams, usually just til the first post-op appointment, about two weeks after surgery, so usually just for the first couple weeks.
Dr. Andrew Sheean: Great. Well, Aravind, I really appreciate you taking the time out of your busy schedule to talk about this interesting study with me. This thromboprophylaxis after orthopedic surgical procedures continues to be a hot topic. I think that we're getting better and we're getting to a place where I think we're more accurately balancing the risks and the benefits of those types of medications. I think this study goes a long way for helping us knee surgeons that do ACLs figure out the best way to treat these patients. Thanks a lot. We appreciate it.
Dr. Aravind Athiviraham: It was my pleasure. Thank you very much for having me.
Dr. Andrew Sheean: Dr. Athiviraham's paper entitled Pharmacologic Thromboprophylaxis Other Than Aspirin is Associated With Increased Risk for Procedural Intervention for Arthrofibrosis After ACL Reconstruction was just recently made available as an article and press online and can currently be accessed at www.arthroscopyjournal.org. Thank you all for joining us and have a nice evening.