 Welcome, I want to focus a little bit on pivot shift injuries and menisci again. We're drilling into menisci pretty hard and I'm starting out with an axial T2 weighted image from a just a standard 1.5 Tesla machine using T2 fast spin echo. I'm sure many of you already noticed that there is a pretty large fluid collection here and it's a blood fluid level. At this point, meniscal tears don't give you blood fluid levels so there has to be something else wrong although that's not why we're showing the case but as we scroll it we see the reason for the blood fluid level. There's a fracture back here which means something pretty pretty violent happened which leads me to the focus of this discussion which is pivot shift injuries and meniscal pathology. I don't so much care about the ACL tear I'm going to show you or the PCL spraying that you're going to see. What I'm interested in is the menisca but before we get to the case I'm going to practice my drawing skills a little further and I'm going to make you a meniscus kind of in a 3D here I'm even going to try and make it have some depth yeah so this is the this is the height of the meniscus right here and as we discussed before we have an inner third, a middle third and an outer third. Now when you have a pivot shift injury and I think most of you can see me what what actually happens is the femur is going to go the the femur is going to go backwards and it's going to slam down on the back of the tibia so when it does that and and sometimes there's a twist with it sometimes it's just direct and when it does that it crunches not only the bone because that's why we have the fracture here but it also crunches the meniscus. So when that meniscus gets crunched it often cracks and that crack is usually a vertical crack in the outer third it happens in almost every single person. Now if we look at the meniscus from the side here's our side view or a sagittal view this would be the back so we'll call this posterior with a P and this is the back where the crunching happens right here so we get this crunch and then we get our crack and that crack could be a partial crack which we do nothing about by the way that crack could be a crack all the way through pardon my lack of a steady hand here a linearity that is still most often not a surgical situation what would you call that you would call that a longitudinal vertical tear as opposed to another kind of radial alert vertical tear we're going to learn about which is the radial vertical tear so that longitudinal vertical tear even though it goes top to bottom we say it's full thickness the first one I showed you as partial thickness is almost never operated on now what do we mean by length if that vertical tear goes from here to here and we're able to measure it from here to there that would be its length now how would we measure it we would measure it by I'm gonna have to change colors here for a moment let's say we have a coronal we'd measure on the coronal from here to here because that's the part of the tear that would show up let's say that's two centimeters and now the tear is going forward see here's the tear right here so the next slice is going to be here we just start adding slices so we started out on foster parallel to the tear two centimeters and now we add a four millimeter cut 2.4 another four millimeter cut 2.8 and another four millimeter cut 3.2 so the length of this vertical tear is going to be 3.2 centimeters would we operate on it probably not if it's not gapped if it's in the outer third we're still gonna leave it alone which is counter to prior teaching where most of these very very long vertical tears used to get so now occasionally if somebody's in there you will see them put a stitch in it but characteristically this type of pivot shift tear is not surgical now let's take that one step further so now that I've done my very manually dexterous erasure let's go back to our view of the meniscus from the side and our three dimensional view and we'll give the meniscus a little bit of depth here I think I did a better job on this one so sometimes the meniscus gets crunched but also remember if and I think you can see me the femur is going backwards right the tibia is going forwards like this so there's got to be some crunching but maybe there's a little less crunching and a little more stretching because the meniscus has to be attached to something remember from our our first series we said the meniscus was attached peripherally and at the roots but it's inner free tip in other words right here is free it's floating free so now we are stretching maybe we're crunching maybe we're not so maybe we have the vertical tear maybe we don't we're stretching and as we stretch stretch stretch we get a strain or a bleed or a micro bleed that's really common we call that a menisco capsular strain or a menisco capsular hemorrhagic strain occasionally if it's really violent this will break off its attachments and it'll flip over on itself it'll tumble that's a true menisco capsular separation those are really uncommon in fact they're rare now on the medial side it looks a lot different than the lateral side because on the medial side these attachments which are going to make a little different color they're kind of like fats domino a pool player they're kind of like short little stubby things so you don't really see them all you see is a bucket of blood we'll make we'll make that red because I'm trying to be a little clever here so you'll see some kind of fuzzy stuff here and if the patient's a little bit unlucky then maybe we also happen to have a little vertical tear here as well so you might have two things this is an extremely common scenario it happens in almost every pivot shift now sometimes what actually happens is you get this and I'm going to make my line if I can through some limited manual dexterity I'm gonna make my line a little thinner a lot there and instead of having bleeding back here instead of having a pretty good obvious fairly thick vertical tear over here we have something very very thin right next to the capsule which a lot of times our friends misconstrue as the capsule itself but it's not it's in front of the capsule and so I refer to that it's my own terminology I call that a sliver tear because it's a tiny little thin line vertical tear vertical longitudinal tear right next to the capsule and this little tear frequently co-exist with that bleed in fact it's the majority of pivot shifts and the minority of them but not an insignificant minority will have pretty pretty thick vertical tears but still in the outer third all of these tears almost uniformly are non-surgical and heal because of the vascularity of the red zone in the outer third