I'm R4 at UCLA, thank you for having me here. So I'm going to be talking about blood flow restriction training in Division I athletes following ACL reconstruction. So quick background, as we all know, ACL injuries are common injuries that can lead to anterior and lateral rotatory instability in the knee. Patients with ACL injuries can have 20 to 33% loss in quadricep volume, following from the time of injury to up to three weeks postoperatively. And additionally, persistent weakness after surgery can lead to functional deficits lasting up to three years postoperatively. To address these issues of muscular atrophy, blood flow restriction training, or BFRT, has been gaining popularity over the last several years, mostly because early studies have shown a positive benefit in terms of muscle bulk with this sort of modality. So BFRT essentially involves putting an extremity tourniquet and then performing a certain set of exercises where the tourniquet occludes venous outflow and restricts arterial inflow, creating an anaerobic environment that ultimately upregulates cell signaling, leading to increased protein synthesis and myogenic proliferation, ultimately causing muscular hypertrophy. And BFRT, in conjunction with low-load resistance training, has actually been shown to have similar hypertrophic effects on muscle bulk compared to isolated high-load resistance training, which is part of the reason why it's gaining so much popularity. So the current literature, in terms of effectiveness of BFRT, is essentially variable in terms of type of injury, type of surgery, implementation timing of BFRT, as well as exercises performed. So there's no real established protocol in terms of how people are doing this. So our primary aim, and sorry, so essentially what we realize is that within the literature right now, even though there is a positive sort of effect on muscle bulk, the clinical outcome of this in terms of return to sport isn't really elucidated or reported. So for that reason, our primary aim was to compare the overall time for return to sport in Division I athletes at UCLA using a standardized physical therapy program that ended up having BFRT or not following ACL reconstruction. And our secondary goal was to determine specific time points in the post-op period where BFRT may be most effective. Next slide. So we did a retrospective chart review of all D1 athletes at UCLA that had knee injuries between 2000 and 2020, inclusion criteria as any primary ACL reconstruction in a UCLA athlete, followed by subsequent rehab at UCLA with or without BFRT, and execution criteria included any revision ACL reconstructions, concomitant, multi-ligament disease knee injuries, treatment or rehab at outside facilities, and delay for return to sport for unrelated reasons. And the rehab protocol essentially is a traditional rehab protocol based on the moon panel, and then the patients either had or did not have BFRT. And as far as data analysis, again, our primary outcome was return to sport time, and secondary outcome was measuring handheld dynamometry, strength testing of the quadriceps at various times post-operatively. And these HHD spores are essentially percent strength compared to the contralateral or the normal side. And for the BFRT group in particular, we calculated the average absolute change in HHD per four-week interval with respect to the initial HHD measurements taken during weeks five through eight post-operatively. This is kind of just a flowchart of our study, but the biggest thing to look out for here is out of 2,377 patients, we narrowed it down to 55 that had ACL reconstruction that met our inclusion criteria, 22 of which were in the BFRT cohort, and out of those 22, 17 had return to sport data available, and 18 had quad HHD data available, whereas in the non-BFRT cohort of 33, only three had quad HHD data available. Next slide. So in terms of results, comparing the two groups, in terms of injuries, gender, sport, and graft type, they're pretty similar, but the main takeaway here is that the return to sport for BFRT was 409 days, as opposed to the non-BFRT group was only 332 days. So pretty significant difference. Next slide. And when plotting these out in four-week intervals, looking at each month in the post-operative period, we find that week 13 through 16 was really the first time point, or month time point, where there was a significant increase in strength at 10%. And plotting these points over time, we looked at, we did multiple comparison studies between the two slope of each interval, and we found no real difference. And the main reason for that was we're trying to elucidate if there's a particular time point where BFRT is especially effective. Next slide. And then lastly, we performed Kaplan-Meier failure analysis, looking at probability of 50% HHD, 70%, and 90%, 70 being when we let athletes start to get on the Alter-G, and 90 being when we start to think of a return to play. And what's interesting here is, only 50% of patients got to 90% HHD or higher at the 52-week mark, which is one year, which is what we typically tell patients in terms of return to sport expectations. So that was significantly less than anticipated for us. Next slide. So main takeaways is that BFRT does not include return to sport time in our Division I athlete cohort. Our data wasn't necessarily suggestive of a particular post-operative time frame where BFRT is most effective. Ultimately, we think it's a matter of finding a balance between BFRT and traditional rehab exercises. Talking to our physical therapists and trainers, it seems like a lot of these athletes are enamored with BFRT, and so a lot of their rehab is focused on that, and they kind of get away from the traditional rehab exercises, and so maybe that's one possible reason. And just due to the inherent nature of our study being retrospective, we had some limitations, the main one being we didn't have a comparative non-BFRT cohort for HHD measurements, which would have been really nice to compare the two groups, but that's something that we're working on for a possible prospective study. And then we also didn't have a standardized BFRT protocol, but that seems kind of up to par. No one really seems to know exactly what the gold standard is. So with that, thank you for your time.

blood flow restriction training

ACL reconstruction

muscle atrophy

functional deficits

Division I athletes