for that introduction. I'm Sai Tamal, I'm a PGY-4 resident at the Mayo Clinic in Arizona. I also work with Phoenix Children's and the title of our paper today, Increased Knee Valves and Hip Abduction Moments After Hamstring Autographed Compared to Quadriceps Autographed in Adolescents Six Months After ACL Reconstruction. The authors have no relevant disclosures for this talk. So in terms of the background for this, it's well known there's over 250,000 ACL injuries each year in the United States alone. And as Dr. Webster just mentioned and has previously been cited, the majority of these are happening in younger patients between the ages of 15 to 25. When you look at the risk factors for ACL tears, it's really multifactorial. Some of them are modifiable, some of them are not. Environmental, anatomic, hormonal, and neuromuscular. But when you think about the modifiable risk factors, they really fall in this neuromuscular realm and they're defined by biomechanics. So the purpose of our study was to compare the biomechanical outcomes during a dropped vertical jump between common autograft types six months after ACL reconstruction in an adolescent population. We looked at four different graft types overall. Hamstring, quadriceps with and without bone block, and then BTB grafts. And we hypothesized that there would be differences in post-operative biomechanical profiles between the patients depending on the autograft type that was utilized. So in terms of the methods, we had a prospective evaluation of patients aged eight to 18 years old with a first time ACL tear six months after reconstruction. We had two board-certified orthopedic sports medicine surgeons and then we used the four autograft types that I previously mentioned. In terms of the motion analysis itself, we had the patients go to our gait lab at Phoenix Children's and perform a dropped vertical jump utilizing a 3D computerized marker system. And then we evaluated biomechanical variables after this analysis. In terms of the data analysis itself, we compared the operative limb to the non-operative limb and any force-related variables were really standardized per mass. And we looked at specific time points during that evaluation. So now moving on to the results. So in terms of the patient clinical characteristics overall, we included 155 patients in the analysis with a mean age of roughly 16 years old with the only significance between the groups was in the height. When you look at knee extension moment particularly, you see that the quadriceps autografts with and without bone block had significantly decreased knee extension moment averages and maximums when compared to the hamstring. And then when you look at the knee valgus moment, you see that the hamstrings autograft were significantly associated with larger knee valgus moments at initial contact compared to the quadriceps autograft without bone block. And finally, when you look at hip adduction and tibial internal rotation, see that the hamstrings autograft was significantly associated with larger hip adduction maximums and knee internal rotation average moments compared to the quadriceps with bone block. And you can see that here in this table. So now moving on to the discussion. I think the first main finding of our study was looking at the hamstring autograft and noticing that its utilization was associated with increased hip adduction maximums, knee valgus at initial contact and tibial internal rotation average. I think the most significant of those was the knee valgus at initial contact. When you look at the literature on hamstrings, I think over the past 10 years or so, there's been a lot of these large registry studies that have come out of Europe showing that hamstrings have consistently shown to have a higher revision risk. So, you know, out of Norway, 2.3 times, Denmark, 1.4 times, and New Zealand, 2.5 times. And this is even higher in that younger patient cohort between 15 and 19. So this led to AAOS this past year putting out these new guidelines suggesting that surgeons actually may favor the BTB over the hamstring to reduce the risk of graft failure. But I think the question continues to be why. When you look at the potential reasons for graft failure, there's really a lot of different ones that have been cited in the literature. Graft size, tensile strength, laxity, patient age, activity level, fixation strategy. But, you know, I think we'd postulate that post-operative biomechanical profile is something to consider and something to address in this patient cohort. When you look at the research on ACL biomechanics, this is one of the original studies published by Dr. Markoff out of UCLA in 1995. And they looked at the different positions of the knee that increased stress or force across the ACL. And three main positions kind of came about, knee extension, knee valgus, and internal tibial rotation. And then when you look at the clinical studies that have been done in the 2000s, particularly evaluating drop vertical jump and initial landing, you see that positions of knee valgus and knee extension have been associated not only with ACL tear, but also ACL re-tear. So when you put those findings in the clinical context of some of the data that we've got looking at our patients, you see that the hamstring autograft is associated with knee valgus moment of initial contact. And that, you know, could likely play a role in their increased risk of ACL re-tear, explaining some of these repeated studies showing higher revision rates in that particular autograft utilization. The other main finding that we had is not particularly novel, but it's still important nonetheless in suggesting that quadriceps autograft is associated with decreased extensor mechanism moments compared to the hamstring. And you can see this kind of, really with any of the extensor mechanism graphs in general, that they seem to have a decreased extensor mechanism moment when you look at that six-month post-operative period. So in conclusion, each autograft type after ACL reconstruction has a unique post-operative biomechanical profile of altered movement after ACL reconstruction. The way I think to think about this is kind of like robbing Peter to pay Paul. When you take an autograft from one location, there's biomechanical deficits that are associated with that, and that surgeons should be thoughtful about the graft choice based on these expected biomechanical deficits, and that they should target these early in rehabilitation. Thank you for your time.

ACL reconstruction

biomechanical outcomes

autograft types

knee valgus moments

graft type selection