Institute and thanks for coming to the talk on biomechanical role of deltoid ligament. I'd like to thank my co-authors. We have nothing to disclose. So a little bit of background on the deltoid ligament. It's on the medial side of the ankle and connects the medial malleolus to multiple of the different bones. It has quite a few strands. So we've got the tibial calcaneal, the tibial spring, and the tibial navicular that form up the anterior portion of the deltoid ligament. And then there's also an anterior deep portion that goes underneath these that's not shown here. And then for the posterior portion of the ligament, we've got the superficial posterior and the deep posterior aspects. The deltoid ligament is frequently ruptured in association with ankle fractures and syndesmotic injuries. Surgical repair is not always the current practice due to the belief that non weight-bearing during recovery of the ankle fracture can leave time for the ligament to heal. But poor outcomes have been shown with conservative treatment with the development of osteoarthritis and also acutely. The contribution of the deltoid ligament to ankle stability remains unknown, specifically the anterior and posterior portions of it. So the purpose of this study was to determine the biomechanical role of the ankle deltoid ligament and also to determine the efficacy of ankle deltoid repair and repair with augmentation. As far as our methods went, we used 10 cadaveric specimens and mounted them to 6 degrees of freedom robot and we tested them in eight consecutive states. So the first one was native with everything intact. The second one was an anterior deltoid cut where we cut the tibio-coccaneal, tibio-spring, and tibio-navicular ligament and also the deep anterior deltoid which isn't shown here. This third state was a simple repair with double-loaded suture anchors and then we went into our first augmentation. So we used suture tape to augment the tibio-coccaneal ligament and then used another suture tape to augment the deep anterior tibio-tailor ligament. After that, we cut the posterior aspect, both the superficial and the deep part, and then we repaired it. And for our final state, we got rid of all the repairs and the augmentations and tested the complete deltoid cut. As far as biomechanical testing, each specimen was mounted and rigidly clamped to a 6 degrees of freedom robotic arm and three tests were performed, an anterior drawer, an eversion test, and an external rotation test. Each of these tests was repeated at zero degrees and 25 degrees of planar flexion, so a total of six tests on each angle. Going into our results, we'll start with eversion. So the y-axis is eversion in degrees and the x-axis is the states that we looked at earlier. The first thing to note on this graph is that the complete deltoid cut was completely unstable. The pound sign represents a significant difference from every other state on this graph. And the complete cut was plus 33.6 degrees compared to native. So this angle in eversion was just completely lax. No restraint whatsoever. The second thing to note is that all of the states, all of the repair states were significantly different from intact. So that's denoted by the star on all these graphs that shows difference from native. So none of our repairs completely restored native biomechanics. The anterior cut showed a small increase in laxity of 2.9 degrees. And the tibio-coccaneal augmentation, while it did not restore native, it did show a significant decrease in laxity from the anterior deltoid cut and the anterior deltoid repair states, which are symbolized by the at symbol and the chevron symbol above that graph. So that one, it did help even though it didn't restore native. The tibio-taylor augmentation that we did second showed no increased benefit compared to the tibio-coccaneal augmentation. And the posterior deltoid cut and the posterior deltoid repair showed no changes either. So in terms of our purpose here, going back to one of our questions, which was the role of the anterior and posterior bundles, we see kind of two different results on this slide. The first one is that while we cut the anterior deltoid, we got plus 2.9 degrees. And then the posterior deltoid got plus 33.6 degrees. So obviously the posterior aspect is very important in that sense as a secondary stabilizer. But when the anterior portion was repaired and we cut the posterior deltoid, which is this graph here, we saw no increase in laxity whatsoever with the cut or the repair. So as long as the anterior portion is repaired and augmented, the posterior deltoid has a lesser role in that setting. Moving on to external rotation. So the results here were pretty similar with the complete deltoid cut being very lax. The anterior deltoid cut had an increase of only 1.5 degrees in external rotation, which was a significant increase, but not a large magnitude. And the anterior deltoid repair and the augmented repair were both not statistically significant from native. So we were able to restore aversion with those surgeries. In conclusion, so for the take-home points here, our most important finding was that with the complete deltoid tear, that caused major instability of the ankle joint. So it's important to repair it in that case, we believe. And the optimal treatment we found for that was an anterior repair with tibial calcaneal and tibial tailor augmentation. In the setting of an anterior deltoid tear only, which is more common clinically, we did note that there was some increased instability, but not a lot. So that could be treated either way. And if it is decided to go surgical, we found that the best treatment was an anterior repair with a tibial calcaneal augmentation. Thank you.

biomechanical role

deltoid ligament

ankle stability

surgical repair

augmentation