It's a pleasure to be here, good afternoon. Happy to present this paper on behalf of our co-authors, as you can see. This paper was accepted for publication in AJSM in May. These are my disclosures, which are available on the Academy website. As we're all aware, adolescent athletes represent a high-risk population with higher ACL revision rates compared to older athletes. This is a paper we published a couple of years ago. We looked at 324 athletes following an ACL reconstruction under the age of 20. As you can see, the three groups were based upon skeletal age. The first and third groups, the youngest and oldest, did pretty well with 6% revision rates. However, the group two population, comprising predominantly eighth and ninth graders with complete transphysiol hamstring reconstructions, had an unacceptably high failure rate. As a result of this study, we made two changes. We transitioned from a hamstring autograph to an all-soft-tissue quadriceps autographed in this population of skeletally immature athletes. And we added an LET within a subgroup of this cohort based upon several factors. We're going to focus on this issue, which is the quadriceps. And in this population, we routinely obtained post-op MRIs at 6 months, 12 months, 18 months, and 2 years, or until skeletal maturity. MRI signal intensity has been used to evaluate cross-sectional area, vascularity, biomechanical properties of healing ACL grafts and repairs. We can see the group at Boston Children's, Martha Murray's group, and Andreas Weiler's in Berlin, as well as the Pittsburgh group under Freddie Fu, have looked at this specifically. And they found that lower signal intensity ratios have been found to correlate with increased tensile strength, load to failure, and vascularity of grafts in animal studies. And on the clinical side, lower SIR is predictive of high scores on single-leg hop tests, as well as patient satisfaction and outcomes measures. The purpose of our paper was to determine if there's a statistically significant difference in ratios between quad and hamstring at 6 and 12 months post-ACL reconstruction in skeletally immature athletes, and to determine if ratios change significantly within each group over time. Our hypothesis was that quad tendons would have a lower ratio as compared to hamstrings at both 6 and 12 months. To our knowledge, this is the first study of its kind to look at MRI signal intensity as a surrogate for graft maturation, and to compare all soft tissue quad and hamstring grafts, both at 6 months and 1 year. We had 70 skeletally immature athletes, 37 hamstrings and 33 quads, and the MRIs were obtained as noted. The surgical technique was an all-epiphyseal reconstruction in 38 with 23 hamstrings and 15 quads, and complete transphysial in 32 athletes with 14 hamstrings and 18 quads. These techniques have been published previously with respect to both the hamstring and the quadriceps, and they both use the same type of fixation, all-inside suspensory fixation with adjustable loop buttons. Sim and colleagues in Korea calculated graft signal intensity ratios by dividing the signal intensity of the ACL with that of the PCL in a region of interest. These circular regions of interest, or ROIs, were used to determine the signal intensity at three points along the ACL and at the tibial insertion of the PCL, as opposed to the paper we just heard, which used the patellar tendon. More on that later. So we measured graft ratios by dividing the ACL graft signal intensity by the PCL signal intensity. On the results side, the demographics related to age, sex, laterality, and type of surgery were not different between groups, nor were they associated with differences in signal intensity. At six months, there was no significant difference in signal ratio between the groups. At 12 months, quads had a significantly lower ratio than hamstrings, and hamstrings had no significant difference between six and 12 months. And finally, quads had a significant decrease in ratios between six and 12 months. This is from a qualitative standpoint, just looking at respective images in two patients with these grafts at 12 months. Our preliminary quad autograft experience to date includes 60 athletes with a mean follow-up of 2.6 years, minimum two years. You can see 39 complete transphysials, 21 all epiphyseals. KT and SANE data is respectable. No revisions to date, but it's obviously early in follow-up in this high-risk group. We did have contralateral ACL injuries in 5%, and return to sport and return to sport at the same level were respectable. There are several limitations to this paper. The first and foremost is the issues related to MSK radiology and the highly variable nature of signal intensity measurements on different MRI slices and reconstruction algorithms. As I've mentioned, other investigators, particularly the group in Pittsburgh, used signal-to-noise quotients. Our MSK radiology team deemed this technique to be unreliable in their hands. Other investigators have used an area anterior within the patellar tendon to compare to the ACL ROIs. And once again, our radiology team assessed this, but preferred the tibial aspect of the PCL as reported by Sim and colleagues in Korea. This was a retrospective study, and post-op MRI times were not precisely noted at 6 and 12 months due to scheduling constraints and COVID, actually, with the older, meaning the cohort that was further along in their follow-up. There were age differences between the hamstring and quad athletes, although these were not statistically different, excuse me. And there was a slight variation in surgical techniques between the all-epiphyseal and the complete transphysial. We also had a small number of athletes within the core cohort that had LETs, but they were not large enough to evaluate statistically. So in conclusion, our hypothesis was partially correct. The quads had lower ratios than the hamstrings at 12 months, but not 6 months. The quads had a significant decrease in ratios between 6 and 12 months, whereas the hamstrings did not. And these findings suggest improved graft maturation, remodeling, and structural integrity of the quad compared to the hamstring. This provides evidence that at one year post-op, quads may have a superior rate of incorporation and synovialization compared to hamstrings. And until we have longer-term clinical follow-up on quad ACL reconstructions in athletes in this age group to compare graft failure rates and patient-reported outcomes, this study supports the ongoing use of quads in pediatric and adolescent athletes. Thank you for your attention. Thank you.

ACL reconstruction

adolescent athletes

hamstring autografts

quadriceps autografts

MRI signal intensity