Good afternoon, I'd like to acknowledge my co-authors from the University of Pittsburgh. We don't have any relevant financial disclosures. Rotatory knee instability may persist after ACL reconstruction. We've discussed it a lot at this meeting, with many proposing possibly injury to the anterolateral knee structures as a cause. Therefore, we've had a recent insurgence, just as we heard in the previous talks, of lateral extra-articular tenodesis procedures in combination with ACL reconstructions. However, there are some concerns regarding over-constraint and overload of the soft tissues and ligaments after these lateral extra-articular procedures. The purpose of our study was to quantify the effects of lateral extra-articular tenodesis on in-situ forces in the ACL and the anterolateral capsule, as well as the lateral extra-articular tenodesis graft. We hypothesized that lateral extra-articular tenodesis will decrease the in-situ force in the ACL back to the intact knee state, and as well as the in-situ force in the lateral extra-articular tenodesis graft would be increased compared to the native anterolateral capsule. We used nine fresh frozen cadaveric knees with a mean age of 66 years, and we utilized a robotic testing system with six degrees of freedom and utilized a universal force and moment sensor. We performed two loading conditions, both with 200 newtons of compression, which is about 45 pounds, and applied an anterior tibial load as well as internal tibial torque, and tested the knees at 0, 30, 60, and 90 degrees. To simulate anterolateral capsule deficiency, we took a 2-centimeter strip from the anterolateral capsule and the IT band, as we previously described, and then our lateral extra-articular tenodesis procedure was a semitendinosus allograft and fixed with interference screws, as described by LaPrade's group, and we evaluated kinematics at three different knee states, the intact anterolateral capsule deficient state and lateral extra-articular tenodesis state, which we fixed at 30 degrees of knee flexion with 20 newtons of force on the graft. We then measured the in-situ forces in the ACL, lateral extra-articular tenodesis graft, and the anterolateral capsule. In regards to our results, the in-situ force of the ACL under an anterior tibial load, you can see here in the graphs between the yellow and green at 60 and 90 degrees, we saw a significant decrease in the in-situ force in the ACL. We didn't see any difference between the intact and lateral extra-articular tenodesis. In response to an internal tibial torque in the force in the ACL, we saw that decrease as well at 60 degrees after lateral extra-articular tenodesis, and again, if there was no injury to an anterolateral capsule, we didn't see any difference between force there and after lateral extra-articular tenodesis. When comparing the intact knee, the intact anterolateral capsule, and the lateral extra-articular tenodesis graft, under an anterior tibial load, we saw no difference between the graft and the capsule. In response to an internal tibial torque, we saw a significant increase in force in the lateral extra-articular tenodesis graft at 30, 60, and 90 degrees between, again, the lateral extra-articular tenodesis and the intact knee. So the in-situ force in the ACL was significantly lower after lateral extra-articular tenodesis compared to the ACL, I'm sorry, the anterolateral capsule deficient state at the deeper knee flexions of 60 and 90 degrees. So that makes this question that maybe the lateral extra-articular tenodesis could be protective for the ACL, but if the lateral capsule is damaged, because again, we didn't see any difference if that structure was intact after lateral extra-articular tenodesis. And again, the lateral extra-articular tenodesis graft force was significantly higher with internal rotation compared to the intact capsule, and again, makes this question maybe this does help the ACL. So in conclusion, in our in vitro robotics study, we found that the lateral extra-articular tenodesis reduced the in-situ force in the ACL if we had an injury to that area, so there could be a protective effect. I know there's been studies before comparing if that capsular structure is intact if you perform a lateral extra-articular tenodesis, if we would have over-constraint, and that study showed that it did. We didn't study that here. And the in-situ force in the lateral extra-articular tenodesis graft was significantly higher with internal rotation compared to the intact anterior lateral capsule, and again, this could lead to possibly offloading other structures. We didn't find any difference in knee kinematics and over-constraint in our study, but obviously clinical applications and studies need to look at midterm and long-term outcomes on these structures before we can recommend doing them all together. Thank you.

lateral extra-articular tenodesis

ACL reconstruction

rotatory knee instability

in-situ forces

protective effect