Hi, my name is Bettina Henkel and I'm going to talk about ACL repair and why we should say yes to an ACL repair. First thing we want to know is does it work? And we can get our studies that will show us a failure rate of 0 to 20% and we would say no. But we can also get our studies that will give us a failure rate of 0 to 8% and in that case we would say yes. After being pretty much abandoned in the 90s, the interest in ACL repair has grown exponentially in the last few years, driven by the better results achieved with more modern techniques. It is important to recognize that not all ACL repairs are the same. There are many different tear characteristics, different patient characteristics in regards to age and level of activities, and there are many surgical techniques. So when we place all these different cases in the same bucket and try to assess what is going to be the failure rate of an ACL repair, we are going to have a very wide range that it's going to be saying that it's between 0 to 40%. So what is the ideal tear? Well, this is going to follow basic orthopedic principles. So we want to have no to minimal tissue loss so we can have an adequate reduction, and we also want to have good tissue quality so we can have a stable fixation. And that has been shown to be more frequent in the proximal femoral avulsions. An ACL tear is more likely to be repairable when surgery is performed less than four weeks from the injury in patients who are older than 35 and have BMI less than 26. On the other hand, it's less likely to be repairable when there is an associated lateral meniscus tear. Can we predict from MRI which tears are going to be repairable? Well, in the MRI, we can see the quality of the ACL stem. We can see the location of the tear, so proximal avulsions in which you have more than 90% of the ACL on the tibial stem. The proximal tears in which you have the tibial stem with 75 to 90% of the total ACL. And mid-substance tears in which you have a 25 to 75% of the ACL in the tibial stem. Using those parameters, it was noted that 93% of patients with the combination of tears type 1 and 2 in good quality tissue could be repaired. Then the next question is, is the repair stable? And in this biomechanical study evaluating a complete ACL section in the femur as seen is in a proximal femoral avulsion, they observed that both ACL repair with an internal brace and a PTB reconstruction provided the same AP stability. Next, we want to know if after being stable, will this ligament heal? And in this MRI study, having the physical exam as the gold standard, it showed that the MRI can show with 86% accuracy which are the cases that are stable versus unstable. And it also demonstrated that is between one to two years and especially over two years that the ACL is going to have a normal signal. And with a more narrow selection with including only acute cases, the morphology and the signal intensity can have even better results with almost all patients showing normal ACL morphology and signal intensity. So let's take a closer look on the factors that influence ACL repair results so we can have a better improvement in our results. In regards to timing, an animal study demonstrated that the load to displacement ratio was lower when there was a delay in the repair. However, in a clinical study, the failure rate was similar in patients operated before three weeks from the injury and the patients after three months from the injury. In addition, there were no differences in the patient reported out. The tear location has been recognized as a very important factor and revisions can go from 0 to 33% when you include tears from all locations and it's going to decrease to 0 to 12.9% when you only include the proximal lesions. In addition, as the number of patients with proximal tears increase, so does the AP stability and on the contrary, there is a decrease of revision rates. The number of tear parts and the synovial coverage have also been shown to be important. And the patients with a one part tear and intact synovial have much low failure rates of 4% compared to almost 27%. When looking at age, animal studies have shown that juvenile and adolescents form a much robust scar with a higher load to failure rate. And the cause of that might be that the fibroblast concentration, osteoclast concentration and blood vessels concentration that are needed for healing are much higher in the immature and adolescent animals and possibly humans. In the clinical setting, repair in very young patients, if they mean 12.9 years old, ACL repair and internal brace of a good tibial stump with excellent ACL quality have been shown to provide good patient reported outcomes in two years. And in addition, there were no leg length discrepancies. ACL repair healed when evaluated in arthroscopy in three months and there were zero re-tears. However, when evaluating a slightly older population of young patients, so patients under 21, but when most of them were between 16 to 18, the failure rate was observed to be 33%. And in patients who were over 35, when using an internal brace, the re-tear was 0%. The bare procedure has been evaluated in the only randomized control trial to date, comparing ACL repair to autograft ACL reconstruction. It evaluated patients with complete ACL tear in which surgery was performed in less than six weeks from injury. All patients had close vises and all of them had more than 50% length of the ACL attached to the tibia. All the other demographics were very similar between the two groups. And the re-tear rate was 14% in the bare group, noting that the ACL reconstruction led to similar results to primary ACL reconstruction. And the re-tear rate was 6% in the ACL reconstruction group. In addition, the IQDC and the AP nelexity was similar between the two groups. Another patient factor that has been shown to be relevant is the patient activity. And patients who have a Tegner score of more than 7 or more than 5 have higher rates of re-tear. Many techniques have been proposed for the ACL fixation, including anchors and cortical buttons. The adjustable loop has been shown to have the less gap formation and less displacement, therefore, better stability. Trying to further increase the stability, the concept of augmentation with tape has been proposed. And the PET augmentation device protected the ligaments from necrosis and ligamentization. And that was probably through increasing the cross-sectional area and decreasing the fibroblasts, lymphocytes and plasmacytes per area. With a similar concept of augmentation with tape, mostly known as internal brace, the failure rate have been between 7 to 14%. And in a comparative study, it was 7.4% with the internal brace and 13.8% without the internal brace. However, the differences were not statistically significant and a higher number of patients might be needed to show a statistically significant difference. Trying to improve healing, also biological augmentation has been introduced. And it seems to improve histologic and mechanical properties. As well, no adverse effects have been seen and high healing and ligamentization rates have been observed. So in summary, case selection is key and ACL repair can be successful in the right patient with the right technique, with most favorable results occurring in patients with proximal tears, with good quality tissue, good synovial coverage. And we should also consider suture tape and biological augmentation. We should expect a higher failure rate in patients who are playing competitive high-risk sports. But that's also the case for ACL reconstruction. And maybe better for acutely injuries, but that's not a contraindication. And younger patients, whether they are likely to heal better, they might still have a higher risk of free tear, which can be multifactorial and have also been seen in ACL reconstruction. Thank you.

ACL repair

failure rates

tear location

biological augmentation

patient selection