Computer generated transcript

Warning!
The following transcript was generated automatically from the content and has not been checked or corrected manually.

So I'm Rachel for those of you I've not met before. I was in the region up until 18 months ago. Now, I'm a consultant in Northwich shoulder and elbow and Charlie and I have been working together on this term like he said, it's um elbow trauma, which there isn't a huge amount that you can cover. But the stuff that you do need to know, you need to know in quite a lot of detail because it comes up in every exam and certainly in my exam in the trauma stations and in basic sciences, I got asked about elbow pathology. So it's worth just kind of getting to grips with the basic sciences, being able to apply that to a clinical situation and then knowing all the kind of trauma stuff that we're going to cover over the next few weeks, I'm not being completely lazy and using an orthopedic research UK presentation. I'm putting it on there because I am on the faculty for the Basic Science course for or UK. And this is the stuff that they want you to know. So if you glean anything from this talk, you'll be absolutely fine when it comes to the exam for those of you who are coming up to it. And if you're in a more junior point in your training, then if you grasp any of this, you'll be way ahead of where I was. So it's not me just being really lazy. So, what we're going to cover is the basic anatomy, the stabilizers of the elbow. And then we're going to talk a little bit about prosthetic design because elbow replacements aren't something that you see every day. And there's a few little nuances about them. If you've got questions, if you put them in the little chat or if there's like a little hello button, then we'll try and answer them as we go through. But otherwise we can talk about things at the end. I'm not going to pick on anyone because I can only see four people at the bottom. So I don't want to be too mean to those people who have shown up. But um during the next few weeks, we will do a bit more kind of vi practicing. We'll ask you a few questions, but this is pretty dull to ask you questions about. So sorry. So the elbow, it's not a hinge joint. That's the first thing you need to take away from this. It's not a single joint. There's multiple parts to the elbow that are all interacting to create a really complex joint, which is why nobody particularly likes them and why people are hand wrist and elbow surgeons or shoulder and elbow surgeons. And there are very few people who would put elbow first. It's kind of our secondary um, joint, I guess. Um, so three joints you need to know about the ulnar humeral joint. So you've got the greatest sigmoid knot and the trochlear. And that one is a hinge joint and that's a highly congruent joint. So that's the one that dislocates when people say they've got an elbow dislocation and it's your kind of bond or elbow joint. The radiohumeral joint is a radial head and the Capelle, that one is ap joint. So it's less congruent because it has a smaller arc. The captum has a smaller arc than the radial head and it allows your rotational movement. Then the proximal radial ulnar joint is another pivot joint. So the radial head is rotating within the lesser sigmoid notch and that's stabilized by the annular ligament which will come on to a little bit later. So you've got the three joints, two of which are pivoting, one of which is just a hinge and they're working in unison to allow that kind of complex movements that you get. Nobody just flexes and extends their arm. There's always a little bit of rotation involved in that nobody just purely supernate or pronate from the radiohumeral joint. There's always going to be the proximal radial ulnar joint involved as well. Um Oscar's managed to say he can't talk, don't worry, Oscar, I'm not going to pick on you. Um So you've got the muscles and they're forming the joints, but you can't move joints unless you've got the muscles there. So, anteriorly you've got your flexors. Um So biceps, brachioradialis and brachialis at the back, you've got your extensors. So, triceps and anconeus and then pronators which are all attached media, um pronator, teres, pronator, quadratus and flexo radialis and then your supers and hopefully all of you when you see somebody with a distal biceps rupture, tell them that actually flex, no sense, strength isn't the main thing that you worry about about the super. So biceps are an important super and then we've also got super that does what it says on the tin and brachy Raia, this gets involved there as well. So um Mr Sbg will be teaching later on in the term and he'll go on about the importance of biceps. And I think most elbow surgeons get a little bit irritated when people come back to clinic because they've been seen in fracture clinic and told, oh, you won't be able to lift anything heavy. No, it's all about. Can they open doors? Can they use a screwdriver if that's what they do with a manual job? That's why biceps are so important. Click the button. So your range of motion, we've got Nicky, one of our specialist physios talking later on about rehab to do with elbow function. But it's important to know what your full range of motion is. So neutral is with your hand pointing straight like this. And then you should be able to supernate up to 90 degrees and pronate 90 degrees anywhere in between. That is your normal arc. But neutral is where they're pointing straight ahead. Then you've got a flexion and extension arc depends how big the patient is. Obviously, if they've got really, really big biceps or they've got no biceps and lots of fat, then it might be difficult to flex their elbow any further than 100 and 40 degrees. But most people who can do 100 and 50 to 160 degrees. And that's when you're getting your hand flat on your shoulder. Although I don't seem to be able to do that, but never mind. And then full extension, some people will have a little bit of hyperextension. So it's always important to look at both arms. When we're looking at people who have suffered a fracture in the past or particularly Children with supracondylar, you want to look at their carrying angle as well. Everybody has a slightly different carrying angle with girls having slightly more than boys, 14 degrees compared to 11. And so again, that's an individual thing where you need to compare and contrast one side to the other. Those are the things that we look at when we're looking at somebody's normal morphology and what their movements like, you'll then look in the books and you can look at um, like skeletal bones to look at all of these things. But in terms of the alignment of your arm, it's, the distal humerus is 40 degrees or flexed anteriorly. So it's not a straight up and down. You've always got a slight bow going anteriorly, which is to allow for that increased range of motion. If you just had it as a completely straight line, you wouldn't be able to flex to that degree. So you always have to have a slight anterior bow, which is 40 degrees and it's hollow at the back with your electron on fo so that you can accommodate for the extension. And then anteriorly, it's got that dip just above the calf. So that when you flex up, the radial head will kind of go into that divot, the truckle axis is six degrees off the long axis. So it's not completely flat. It's got a slight inclination to it. That's quite important if you have a horrible distal humerus fracture that you're trying to fix, because you don't want to create a completely straight line. There has to be a slight tilt in it. And then we talked about the various angulation more in girls than boys. The center of rotation, which will come into be important when we're talking about the ligament complexes is through the center of the radial head and the Capello. So it's not smack bang in the middle, it's off to one side. So then we talk about the stabilizers and this is where in basic sciences in the exam, they love to start talking about things. So there's lots of different ways to think about it. And I've broken it down into two different ways of talking about it. But actually, it's the same stuff just being phrased in slightly different ways in the same way that when you talk about any joint, you've got static and dynamic stabilizers, that's what you have in the elbow. But within the static um group, you have primary and secondary stabilizers. So the most important ones in terms of primary stability in your elbow are the ulnar humeral joint. So where the um humerus is embedding into the ulnar that we talked about as a hinge joint and then the ligament complexes. So the medial collateral ligament and the lateral collateral ligament complexes secondary to that you've then got the radiocapitellar joint, the joint capsule, which is mostly anterior in the elbow. And then the common flexor in extensor origin, they're going to be really big groups of muscles that are going to hold the elbow in a equilibrium between the two. So they're the static stabilizers of your elbow. But then the dynamic ones are all the muscles that cross the joint. So they're the ones that are gonna pull and um relax to allow movement, either inflection or extension or supination pronation. Um So primary static joint stabilizers, ulnar humeral joint, we already looked at the original picture highly congruent. The majority of the muscle action around the elbow is causing a posterior joint reaction force. We're not going to go into huge, we're not going to go into joint reaction forces around the elbow at all actually, because it's very unpleasant and I think that's a bit too much to hit you with on the first session. It might be something that we talk about on the face to face day. But rather than dragging the humerus down onto the ulnar or trying to push it forward against the coronoid, everything's moving in a posterior fashion so that it's trying to embed the humerus further down and make it more stable in its concavity. The coronoid at the front acts as a buttress to prevent a knee dislocation. Um and it locks into the coronoid fossa in deep flexion. So where we talked about around the front of the coronoid with the radial head being able to come up. Oh, sorry, capitellum with the radial head being able to come up, the coronoid will flex into that fossa just to prevent any ability for the elbow to pop out the back. Um You'll hear o'driscoll and Regan Murray talked about a lot on the elbow. They're like two big American elbow surgeons who basically have coined all of the um different ways of classifying things or managing things around the elbow and they both have their own different classification system for coronoid fractures. Um The most simple one, I think other people might think differently. I like the ra mari because it's just type 12 and three. And it's basically talking about whether it's the tip, whether it's in the middle or whether it's at the base of the coronoid. And to me that makes more sense just from a very clear picture on an X ray or a CT scan, the more bone you lose, the more likely you are to have an unstable elbow. The o'driscoll classification talks more about your anteromedial facet, whether it's the tip, whether it's down at the base. And that when you're getting into a little bit more complexity as to whether ligament involvement is there, then that's when that's really useful. And you can talk about either you in an exam, don't need to specify what you're talking about just about how you would potentially classify it. And you can just say by the proportion of the coronoid that's missing. Um When we talk about the anteromedial facet and the ligament attachments, it's because the medial collateral ligament is involved in that side. So if you've got an anteromedial fracture, you're more likely to have instability around the elbow, even if it's only a small fragment. Um just kind of put that on there, but it'll become more obvious in a minute. Um There's a lot of words, sorry. But um the next primary static joint stabilizers are the ligaments So we talked about the lateral collateral ligament complex and the medial collateral ligament. So, lateral collateral ligament complex is made up of four parts. Um In general, we talk about three and then there's the accessory one that there's a lot of controversy over whether it's a real part or not. But for the point of this, we'll say that it is. Um So the three main parts that we need to talk about are the lateral ulnar collateral ligament. If I move this, no, you can't see my pointer. Can you? No? OK. That's pointless then. Um So the lateral ulnar collateral ligament um is the most important structure when we're talking about postural lateral rotatory instability. Um uh It's the primary restraint to a various force. So um we'll talk about postural lateral rotatory instability later on as well when we talk about ligament injuries and you'll see the importance as to its use as its primary restraint to various force um if it's deficient. So if you've had to do a repair or you've got somebody who's had a dislocated elbow and they've got a little bit of a drop sign, you're a little bit worried about them. If you put them in supination, they'll be more stable if you pronate. If you put anybody who's got a previous elbow dislocation or ligament instability and you put them in pronation, the risk is that they'll further dislocate. So, um one thing to take away from this I guess just as a really simple thing is anybody you're worried about if you plaster them, I don't like plaster, but if you put them in a sling and ask them to keep their hand fully supinated, they're going to be more stable. Um The radio collateral ligament works synergistically with the lateral and the collateral ligament. So it's not particularly useful by itself, but it's really, really useful when it's working in conjunction with the lateral and the collateral. Um there there, when we're talking about doing repairs, if we're going to then try and repair the ligament complex onto the side of the CAPELLA. Um What we need to do is to find that central point and that's the isometric point through the lateral condyle. So sometimes you'll see some people are a little bit more panicky than others will use X ray and we'll try and get a true lateral and we'll try and see that you're right in the middle of it because that's the isometric point of your elbow. If you manage to offset that slightly superiorly posteriorly anteriorly, then the whole biomechanics of your elbow might change, it might create an unstable elbow as you're going through a full range of motion. So sometimes we eyeball it, sometimes we use X rays. Um but the isometric point is in the center of that. Um Then the annular ligament we mentioned a little bit very briefly, but that's essentially the most important stabilizer of the radial head. If your annular ligament um has been disrupted in any way as you start to pronate, supinate the forearm. What can happen is the radial head can dislocate out when we do um terrible triad injuries or really distal humerus fractures. Sometimes we detach the annular ligament in order to get access to where we need to be. Um and it's really important to repair that to increase the stability of the elbow. The risk is you can do a beautiful fixation, get everything back where it's meant to be. But if you don't repair that annular ligament, it can just dislocate and then you'll look really sad or really silly when you find that the radial head is dislocated later on. Um So that's the lateral side and the medial side, you've got the medial collateral ligament and it has three parts to it as well, which is kind of helpful if you just remember there's an accessory one on the outside, but otherwise there's three important ones and three important ones on the medial side. Um They have different importance depending on the position of the elbow. So the anterior bundle, if you're between naught and 90 degrees of flexion. So back to that, that's where it's the most important um primary straight against valgus stress, it's tight and extension and loose in flexion. So the more you extend, the tighter it will become, the more you sorry, the more you flex, the t it will come, the more you extend the looser it is. So um between nt and 90 that's when it kicks in, when you get past 90 the posterior bundle takes off. And so that becomes tight in further extension. And it also is loosen extension. So they're flipping around and then the transverse bundle is the kind of bit at the bottom which is just purely attached to the ulnar and it inserts into the sublime tubercle and that's called cooper ligament. The reality is when you look at these in real life, it just looks like a big band of tissue. So when you're doing a medial sided repair, it's not quite the same as doing a lateral, you basically want a nice big footprint so that this web can stick back on. It doesn't have an isometric point. It doesn't matter if you're not exactly in the right place. The most important thing is that you've got it reattached and it does tend to be a big web that holds everything where it's meant to be. So we don't go searching with X ray for the best place to put it. Um So they're the primary stabilizers and then secondary stabilizers, we've said there were kind of three important ones. So the radial capitella joint, it's your restraint to valgus force. Um So if you have a medial collateral ligament injury and it's disrupted the radial head then has to take over. So if the medial side is gone and you're starting to go into valgus, then the radial head um is stopping it by hitting up against the cell. So it can't go any further. Obviously, if you've then gone on and we'll talk about it in a second to create that full circle, then what can happen is that you can bypass the radial head and the whole thing will just dislocate out. But that's the next step that we'll get to the capsule like we talked about is right at the front and it's holding everything in the position that it's meant to be. It's most important in a distraction or hyperextension or valgus stress. So when you see people and they've gone and landed with their arm behind their back and they've kind of hyper extended in that position. They will undoubtedly have disrupted the anterior capsule of their elbow and then the common flexor and extensor origin, it's very dependent on the position of the arm and they're, they can then interfere with the dynamic stabilizers of the elbow. So, whilst the flexors and extensors of the forearm aren't particularly involved in flexion extension pronation, supination. They all haven't linking part into the stability of your elbow. If one side like your common extent is gone, then your flexors are going to be working over time and you'll have an imbalance. There won't be this synergistic relationship between the two. So you can end up with more pull in a valgus stress. Um which then goes on to the dynamic stabilizers. And we mention that there's the four groups. So the flexors and extensors, the pronators and supers and what they're working is together to create a force couple that prevents their elbow from being distracted or dislocating. So the flexes and the extensors work against each other and the pronators and the super natives and the whole idea is that they're balancing to get everything to stay in the normal alignment. Um They do, there are a few that have specific constraints and Anconeus um is really useful for Varus in the posterolateral rotatory instability pattern. Um The medial flexors resist a valgus force and the lateral extensor resist a varus force. And you can think about those from where they all attach. If you detach things off the medial side, then you're going to be able to open up more in valgus stress. If you take things off the lateral side, you're going to be opening up in a V stress. So it's pretty self explanatory wherever they're attaching to if they detached and then the things that are working in opposition are still attached and you're going to get a force that pulls you from one direction to the other. So we've talked about primary secondary stabilizers and we've talked about static and dynamic, but we talked about a Driscoll being the man who has coined everything to do with the elbow. And he made this fortress of stability and if you can talk about fortress of stability, everybody's very excited around the elbow. But essentially, all that's done is taking your primary stabilizers to your ulnar humeral joint, your medial collateral ligaments, and your lateral collateral ligaments and created the big triangle. So that's your main fortress. So they're the main stabilizers of your elbow and then internally you've got your radiohumeral, which is your radiocapitellar joint. You've got your flexor and extensor origin, which we've already said are our secondary static stabilizers of the elbow. So all he's done is taking your primary and primary and secondary static stabilizers and created this fortress. Um It's a fortress because you need all sides to be in contact. So if you break something, so if you detach your lateral and a collateral ligament complex, then suddenly you don't have that equilibrium between the three. So then your lesser stabilizers or your secondary stabilizers need to take over. So you can lose one thing and be able to take over with the things in the middle. But if you lose more than two, you can't. So it's a process of stability that goes from everything being lovely to losing one, but having to overtake from the, from the secondary stabilizers or if you lose two, then the secondary stabilizers are going to be struggling. And that's when you get an unstable elbow and can go into a dislocation. And then this picture on the right hand side where it says 123, that's the circle of hurry. So that's basically where if you are going to dislocate, you take out one part, two parts, three parts. And the most likely chain of events is that you take out the lateral side, take out the capsule and then take out the medial side and then it will come around the back and that's when you'll dislocate. Um So it's a step wise approach. It's not something that just goes with, you know, you don't just tear your lateral on the collateral ligament and dislocate your elbow. It has to go through a process where you're taking out all of these corners from the poss of stability. Um And then these pictures down here are just about what a dislocated elbow looks like. So you can have a normal elbow, which is zero, then a poster lateral rotatory instability, which is where you've taken out some of the ligament complex. And it started to perch on top of the radial head and then that goes further where the whole humerus comes out and perches and then you have a full dislocation. Um I'm not going to go into detail about posture, lateral rotatory instability or about dislocations because that's something that will be covered when we talk about ligament injuries. Um This is just like the background as to why these things happen. So don't worry if it doesn't make sense yet, it might never make sense, but that's also OK. Um but we will go in more detail. This is just a brief overview of everything and why if you can get in your head, what the normal anatomy is, what the normal function of these things are, then it should make it easier to understand when we start talking about the pathologies. Ok. Um, elbow arthroplasty. So, has anybody seen an elbow replacement? 000, that's impressive. Ok. There's at least two out of the three people I can see which is more than I was expecting, I think as a register, I didn't see very many at all. I think maybe I saw four or five and considering I wanted to be an upper limb surgeon, that's kind of depressing, but now I'm expected to do it. Um, but they're pretty rare and nowadays they're even rarer because the rarer even more because the people with I be doing were rheumatoids and rheumatoids now have such better medical management that the people who needed joint replacements in the past don't. So they are few and far between, which is why be the British Elbow and shoulder society are working and have been working towards for quite some time setting up elbow hubs. And the idea is that the volume isn't that high. So we need to make sure that the right people are doing the right operations and certainly we don't want people just dabbling in one or two a year because it's not the kind of operation that you dabble in. Um, there's also outlines that it should be a dual consultant operation because again, it's not something that any of us would be able to generate huge numbers in. There's maybe two or three people in our region who would have their own independent volume. Um, but certainly for the majority of us, it's not something that we'll see very many of we are doing more and more hemiarthroplasties, certainly for trauma. And so we'll talk a little bit about that and then radial head replacements fall into this category as well. And I'm sure most of you will have seen a radial head replacement for an unconstructive radial head fracture. So that's something that, yes, it's a form of elbow arthroplasty. It's not obviously a full joint replacement, but it's something um there still guys on n so elbow arthroplasty, the same principles as for any other joint. So you want to relieve pain, restore mobility and restore stability. We also want to restore the functional mechanics of the elbow, which is where the problems come in because we've talked about it's not a hinge joint, it's not a pivot joint. It's all of the above and there's three different joints involved. So it's quite a complicated thing to try and mimic, which is why it isn't a good operation. It's not straightforward like a hip. All right, it is complicated. It's an elbow. There's also a high risk of failure due to excessive blow through the prosthesis, we will limit people to 6 kg of weight in that hand for the rest of their life. That's not very much, that's a bag of shopping. So it's not an operation that I would want any of you guys to have to have full stop. But certainly anybody who's high functioning, anybody who's using their elbow, anybody who's got any kind of demand on it, it's not going to be a useful operation for them, which is where the hemi might come in handy, especially in the trauma situation. So the indications the problem with doing this as a PDF is that you see everything, I can't surprise you with the next section. But the indications are end stage rheumatoid arthritis, really severe osteoarthritis. But most people who have end stage osteoarthritis, they're not too keen on the idea of an elbow replacement and then then unconstructive fractures in low demand patients. So it's a little bit like with shoulder arthroplasty, the older you are, the more likely you are to get a full joint replacement, um kind of conversely to hips. So high demand young person is going to get a hemi arthroplasty rather than the total elbow because actually they'll be able to function a lot better with that. And it will have a better longevity than a, a full elbow replacement. Same as with a hemiarthroplasty for proximal humerus fractures is better for a young person than an old person. I had to bring in the shoulder. I told you I'm a shoulder surgeon who does elbows. Um And then this is a really busy slide again. Sorry. But um elbow arthroplasty comes in the form of a total elbow or a partial arthroplasty in which if we talk about partial first. So hemi arthroplasty. So half of the joint being replaced, you can do a radial head replacement, we can do a distal humerus which is a the hemi standard hemi we would talk about and then we can have unicompartmental, which is a radial capella replacement. I have never seen one of those in my life, but it looks kind of cool. I think it would be a little bit unusual to have very isolated lateral disease which warranted a radial head replacement and a capella replacement. Most of the time you can get away with just the radial head replacement. Whether that's, I mean, this might happen to somebody who's had either an acute traumatic injury and you just didn't think it was reconstructable to sort out the c tell him or it might be for somebody who's had a radial head replacement and who's gone on to develop quite significant wear from that. And it's not something that I think you would ever be asked any serious questions about because I honestly don't know anybody who's doing them, but they're there anyway. Um And then total elbow replacements and total elbow replacements come in three different types just to add more complexity to it. So a constraint device which is essentially a hinge where it's the humoral component and the ulnar component are locked together and it's got a cement fixation and they have a high failure rate due to loosening around the prosthesis because of the amount of stress that's going through it and breakage at the linking point, a semiconstrained device which is either two or three parts, which normally has a polyethylene insert and has some kind of a snap fit. So it's not necessarily completely linked, but it's a little bit like when you talk about a dual mobility cup in the hip, that one part is clicked into the other, but it does have the potential that it can dislocate. Um They're what we refer to as a sloppy hinge. So they aren't a fixed hinge like the constraint device would be, but they will only allow a certain degree of, of movement and they generally allow up to five degrees of various valgus strain. And then you have an unconstrained device and we don't really use these because they're two separate prostheses that require you to have intact ligaments and a static alignment. So to have intact ligaments that are going to be reconstructable, I'd question who that would be suitable for because a rheumatoid everything is going to be questionable. Anyway, they've got significant bone disease, they're going to have significant soft tissue involvement. They're not going to have the greatest bone quality to have anything that's still attached in trauma, you're unlikely to find that you've got a really nice chunk of bone with good intact ligaments. I just don't think there are that many people. So the vast majority that we use are either semiconstrained or constraint devices. And then um so constraint versus linked, they're not interchangeable terms, although they are linked just to make life even more complicated. So the amount of constraint is um determines the risk of loosening and the risk of instability. So a linked prosthesis is something that has a hinge. Um So that can be either the uh the constraint device that we talked about or the semi constraint, they're both um linked devices because they have a hinge. Um the sloppy hinge that's in a um that's uh OK. Oh yeah, sorry Charlie's talking to me. So the linked device, they have a hinge. It can be the sloppy hinge or it can be the one where we've put a bolt across and made it a complete fixed angle device. So they all have a degree of constraint if they're linked. Um The more constrained they are is the higher the risk of loosening because of the amount of stress that's then going through that interface, the lower the degree of constraint, the higher the risk of instability. So if you put a hinge and you've got one piece of metal, one piece of metal and a bolt between the two, that's really quite constrained. That's not going anywhere. If one part fails, it's going to transfer into the other part. Whereas if you have a lower constraint, like a sloppy hinge, then that allows for that various valgus twist. So you've got more movement between the two devices so they can fail independently. So they're both linked devices, they've both got a hinge, but one is more constrained than the other. Does that make sense? I know it's a bit waffle. Um When they're unlinked, the stability is dependent on the conformity of the prosthesis. So that's when we're talking about those um the unconstrained ones at the bottom where there's two different parts, they're not linked in any way. So you have to get them bang on, they need to be in exactly the right place and you need the soft tissue balancing that will allow it to function normally. So that's an unlinked, unconstrained device. So the first two are both linked with very constrained, less constrained and then the bottom one's got unlinked and unconstrained. Um elbow replacements aren't great. We, I kind of don't know how many times I can say that, but they're fraught with complications, they can be unstable. So we've literally just said the lower the constraint, the more reliant you are on the anatomy. So what you don't want is something that's really, really fixed because that's when you get loosening because of the amount of stress that's going through the interface. But the less constraint you have, the more movement there is and therefore the, the more unstable your prosthesis can be. And that can occur in up to 9% in the literature of prostheses that are put in the ones that have got a semi constraint. And we've put in a polyethylene link somewhere like in the latitude elbows that we use or the Conrad Murray, which are used as well. You can get polyethylene wear and it can be from point loading if they haven't been put on in, in a completely anatomical position, or if the patient's got more of a v or valgus angle, um or if they just try and do too much with that elbow and so you can get an increased amount of wear and they call it the intersection. So basically, if you've put it in in more than seven degrees of varus or valgus or rotation, then that's when you start getting that point where the more wear you get, the more debris that forms, the more increased risk you have of loosening around the prosthesis. And certainly you'll see x rays of people who've had elbow replacements in for the last 20 years, they've created huge amount of debris and they get this ballooning around the cement mantle and it can go right up into the proximal element of the humerus and down into that ulnar as well. So it can be quite catastrophic, the amount of loosening that you then develop the amount of bone that you lose to, then go on to do a revision operation can be technically very, very difficult with very high risk of periprosthetic fracture. And so with the polyethylene where it kind of goes on to the next two parts where you've got the osteolysis we've talked about and the aseptic loosening. Um I've already said these things. So it's increased if you're high functioning and you do more and increased with the amount of constraint in the prosthesis because you've got more wear her caring and more you do. Um infection is high risk because of the patient selection. The vast majority of these are people who are rheumatoids or have steroids for whatever reason or maybe are in acute trauma who had an open distal humerus fracture. So they tend to be quite a poor patient selection in terms of the risk of infection. And they can be people who present years and years down the line with some kind of indolent and you know, low virulence infection, but it's causing significant osteolysis and loosening around the prosthesis and then fractures. There is a may classification of the fractures and it's basically 12 or three. So one is around the most distal aspect to the humerus or proximal aspect of the ulnar two is around the stem and then three is either proximal or distal to the stem. Um Most of the time we see type twos, they tend to be the more common ones. And that's when you've had the prosthesis in a nice position. You've developed the osteolysis, it's then started to toggle and then it breaks through. And thankfully, we don't see huge amounts of fractures because people tend to come and see us with the osteosis before that happens. But it still means if they go on to have a revision operation, there isn't a huge amount of bone stock to then perform their revision arthroplasty through and you're using huge amounts of cement and they still have an increased risk of fracture. And I think that's it. So, so there was a bit of a whistle stop tour. It's a lot of me waffling but we kind of covered the basic anatomy. The most important part, which is the stabilizers of the elbow. It doesn't matter whether you talk about them in primary static, primary and secondary or dynamic stabilizers or whether you want to talk about it in terms of Driscoll's fortress of stability, I think during my basic science, I threw both things out because of just like verbal diarrhea and said everything, but they are essentially the same thing and you're just putting them in a different order. Um All you need to know is that if you lose one, you can just about manage with the other, um lesser ones taking over or the secondary stabilizers taking over. But if you lose two, that's when you're in real difficulty and at risk of having a dislocated joint. Um It is just a brief overview. Nothing I've said today is groundbreaking or rocket science. It's literally out of books and the usual things, but hopefully it's just a bit of a grounding for all of the stuff that comes in the next few sessions. If you understand the stability of the elbow, you can understand why things go wrong and how we don't fix it.