Good evening. My name is Yimeng Yan, and I'm here today to talk to you about bridge enhanced ACL repair, the update in 2022. I have no relevant disclosures for this presentation. For those of you who are unfamiliar with the Bayer ACL repair procedure, briefly, this is the use of a biologic collagen sponge that's interposed between the torn ends of a mid-substance ACL rupture. As you can see here, the ACL is torn in the middle. What we do is insert a collagen sponge that's infused with the patient's own blood. The ends of the ACL are whip stitched and inserted through the middle of the sponge. The ACL is pulled up tight towards the implant, and gradually over time, the Bayer scaffold is replaced with healing ACL tissue. The biologics behind the collagen sponge has been the brainchild and the work of my partner, Dr. Martha Murray. She's developed a sponge which is shown life size, which is essentially inert, and encourages ACL ingrowth. The collagen scaffold was first validated in pig models. Subsequently, Bayer 1 was performed, which was a 10-patient cohort looking at the safety and efficacy of this collagen scaffold in humans. Once Bayer 1 was completed, the Bayer 2 trial was begun. This was a double-blind randomized control trial with three surgeons looking at augmented ACL repair versus ACL reconstruction using AutoGraft. This opened in 2016, and we have 99% follow-up at two years. This is an example of one of my patients who has a mid-substance ACL tear that you can see on the left, and this is her two-year MRI follow-up after using the bridge-enhanced ACL repair technique. This is a summary of our findings from the Bayer 2 clinical trials. We had no patients that had any infection or rejection, and at two years, the augmented ACL repair subjects had comparable patient-reported outcomes and knee stability. They had increased muscle strength compared to the controls, and their re-injury rate was similar to that of the controls. We also found that patients who failed the Bayer surgery that underwent a revision reconstruction actually were more similar to primary reconstructions than to revision reconstructions. If we look at the re-tear rates for our patients in the Bayer trial, 14% of the patients failed, which is comparable to what is reported in the literature for failure of ACL reconstructions using AutoGraft tissue in adolescents. We have just taken a deeper dive into re-tear rates in the Bayer 2 trial. What we found was that the risk factors for re-tear actually are younger age. If they had a higher medial tibial slope, and if they had a contact injury at the time of the ACL tear. As you can see in the graph, patients above the age of 22 had no re-tears, whereas the greatest number of re-tears were in patients under the age of 16. If we compare revisions of the Bayer failures to a standard revision ACL reconstruction, the Bayer failures actually did significantly better than historical controls and were more comparable to primary ACL reconstruction. So if we look at where we're at with augmented ACL repair, we first have to actually prove that the model worked. We had to look at the safety of the biologic scaffold, and then we had to do a randomized control trial in humans. Since this has all been completed in December of 2020, we received FDA approval for the Bayer scaffold. We have shown that the Bayer technique is a viable alternative to standard AutoGraft ACL reconstruction. However, there may be improvements in surgical technique and sport-specific rehabilitation that could strengthen outcomes from the surgery. Adolescent patients remain a particular challenge, and while Bayer can be considered for this population, there does not exist a one-size-fits-all solution for this particular group. Thank you very much for listening.

Yimeng Yan

bridge-enhanced ACL repair

BEAR procedure

biologic collagen sponge

ACL ingrowth