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All right. So we're gonna kick off with cement. So uh what is cement? Anybody want to hazard a guess come up with a definition. Anybody it's gonna be a really long afternoon otherwise guys uh meet up to tackle it. Okay. So that's its chemical composure composition. And also on my slide, I've just minimized. Okay. Can have a go if you like it's Yeah, go ahead. Yeah. So there is uh a device that we use in orthopedics or, or a material rather that we create a interface between the implant and the bone. Uh Yeah. Good. Uh So apart from just being an interface, what other uses do we have for it? You can act as a spacer or as avoid filler. Yeah. Good. Fine. So uh the X ray here on, on the left of the screen is what we would call a cement omer. So filling a void with cement that might be after tumor surgery like a giant cell tumor curettage. Um We can use it for local delivery of antibiotics that might be as a cement spacer or it might be, for example, around a fusion nail for that local delivery of antibiotics and it's most common uses. Obviously, we use it as a grouch. So we so interdigitate with the cancellous bone around an implant. The most important things here is that it's a polymer and it is a, is a material that we're using in orthopedics and to be able to say that it is polymethyl methacrylate. So these are the kind of components of your answer for when you get asked what cement is, sometimes we don't just use it for local delivery of antibiotics, but we're actually using it to exploit the fact it produces heat. Okay. And that is one of the advantages of using it as avoid filler in a giant cell tumor because that heat will kill some of the residual tumor cells good. So it's made up of a powder which is a polymer and the liquid which is, it's monomer. Does anybody know what's in either component? Does somebody want to talk through what's in the powder? N E S T three S R S T four's have any ideas, Maria? Are you signed in anybody else doing their exam next week? That would like to hazard a guess that the answer. Ok, sorry, I'm not. It's Kemp. Hi, Kem. Have a record it. Thank you. I'm not sure which way around it is, but I know there's you need an initiator uh which I think is in the powder. Um And then I think if it's antibiotic confused, I think that's also within the powder. Uh mhm. Why is it green or usually green? Wasn't it makes it green? I can't remember. Oh, that's right dot Thanks. Uh okay. Would that be cute? Hi, Vicky. Vicky. Can you remember what else is in the liquid side? So the current is uh usually chlorophyll which is for the green ones. You remember any of the others, the initiators in this one, which is the bit that Ken was just speaking about. Yeah, I missed what you just said. I can't hear you mentioned an initiator which is in the liquid. Any anything else from the liquid that you can remember? Um No, I don't think so. So we know that overall um it is a polymer substitute that is making made, isn't it with cement? So a polymer has to be made up of lots of monomers. So the monomer is in the liquid and that's your methyl methacrylate which when you've got multiple of them becomes the polymer. And so then if you have polymethyl methacrylate, so that's your first part of the monomer liquid, then you have an initiator. And in this case, it's an N dimethyl pathology as much as I try to think of a way to help you guys remember that I can't other than the fact that it's the active ingredient, if you like TNT, um it needs a stabilizer and that is hydroquinone most likely. And then a colorant which can be chlorophyll in the powder, you can think of this if you've seen any of Queen Tang's videos and it's the way I used it for my exam is to remember it as Parker for the polymer and the monomer is misc okay. So the polymer side of things uh include some polymer already. So that is your polymethyl methacrylate and a pacifier because we want to be able to see, see it on the x rays. And that's usually a barium sulfate and then a catalyst to get the reaction going. And that's your benzoyl peroxide. And finally, uh not all cement contain antibiotics, but if they do it needs to be heat stable and it needs to be able to reach, reach therapeutic levels locally. Okay. So what are the properties of cement that we're exploiting cats? You signed in? Yeah. Anybody. So we, we use it because it's a strong in compression. Yeah. Absolutely. When you're chipping out cement, what's the easiest ways to get cement out or what's it there for a weekend? Uh hmm. So it's strong compression and weak intentions. So when you're taking out your cement, uh they're the properties that you're exploiting. Okay. Why is it that we're mixing cement in a vacuum? Anybody wonder why we connected up to a vacuum to mix? Okay. Well, we're mixing it in a vacuum because we're trying to reduce its porosity. Okay. And what we're doing is removing any bubbles are forming in the cement. So when we mix uh the idea is the picture on the left has got large and small pause. And the picture on the right has been mixed in a vacuum and has got much less of what we would call macro pause and also has slightly less micro pause. Now, the disadvantage of mixing in a vacuum is that you get less antibiotic illusion, but it does mean that you have a higher risk of fatigue fracture. Okay. So you're more likely to get a fracture propagate between two large pores. And so your cement can fail earlier. But saying that by having uh these pores in the cement, it does to some degree stop crack proper uh stop micro fractures propagating. So there's advantages and disadvantages of both using um cement that has been mixed in a vacuum, e less likely to fail early and not using a vacuum and perhaps having higher um antibiotic illusion. So just remembering that principle for, if you're wanting to substitute, not substitute but supplement a fusion nail in a knee for an infection with cement, then you might want to not mix it in a vacuum, for example. So you've got more local release. Um So cement has got curing process and the ambient temperature in the room is generally speaking about 21 degrees. And when it's first mixed, we've all had that very sandy and doughy phase of the cement where it gets stuck to your glove. And the point at which the cement stop sticking to your glove becomes what's known as the working phase. You can only lasts less than two minutes that doughy phase. And at this time, the temperature in the cement has an increased. So this is the time that you can do what you want with the cement or the working phase, you can work with it, how you want to work. And then all of a sudden we start getting the exit thermic reaction occurring. And as the temperature increases up to between half, which is 57 degrees between 100 degrees and you're 21 degree ambient temperature that becomes your setting time in case you're working phase has then stopped, you can't really position that cement in any different way, reaches a maximum temperature actually of around 93 94 degrees. Then we've got see quite quickly that the temperature starts to come back down again and we're sitting here around the 602nd point. But actually that cement will continue to cure for up to 24 hours after it's been mixed. So these are the phases that you would be talking about if you were asked how cement cures and you should be able to very quickly draw out this graph in a basic sciences station. Okay. So there's lots of things that affect how quickly your cement changes humidity we know is one of them, okay. Uh Something that we think about in theater design, for example, uh the type of cement itself actually affects how quickly it can change set as well. So some of you going through knowledge, for example, might have seen or used simplex, which is very runny and stays runny for a very long time. Or some of you may also have had some experience of using pala cost fast, which sets even quicker than standard polyp palacos and it's usually around the seven minute mark. So knowing what cement you're given is very important. We also know the temperature in theater affects how quickly the cement sets and how how this cement has been handled. So if the scrub nurse very rigorously mixes that cement, you'll notice that it sets faster than one that has just been mixed by standard means and probably notice that when you're handling cement while you're waiting for it to set around your stem, that the one that you've been holding in your hand and probably playing with sets faster than the one that's in and around the stem. Anyone want to hazard a guess between the two differences here in these charts? Okay. So these are the differences in your cement. So okay. So with a low viscosity cement, the doughy phase Edie Simplex um is much longer and overall the setting time takes much longer. Anyone you cement and nose as simplex cement and knows how long it takes to set using knowledge at the moment about 14 minutes. 14 15. Yeah. Yeah. So it can take quite a while, can't it, it means that you've, you've quite a long time to be able to use that cement. And then the high viscosity cements have a much shorter doughy phase. Um And so this, you might use, for example, if you're putting in a cemented cup, which is not something that's done as often down south is up north, uh good, right? Any questions there about cement. So the main things that you will need to do in the exam from a cement point of view is be able to talk about what it, what it's uses are and what it is, what it contains and how it cures. Okay. Um Are there any questions in the group chat? Um Iggy or Seb because they have admin rights and I can't see no. Okay. We're gonna move then on to Laminar Flow and then hopefully Nikki will be here from her clinic and uh Nicki's got a paper that she has produced, read about Laminar flow. So, uh where does the contamination in the air come from? From staff? Yep. Thanks Mike from the patient from the patient from the floor. Yeah, good. So the most common source or the predominant factor is the personnel that are in theater. So we actually shared anywhere up to 50,000 microorganisms every minute and 90% of that occurs from below the level of our neck. So we are the main source of contamination in theater. Okay, airborne contamination is responsible for about 95% of wound contamination. So, it's really important that we get this part of our theater design. Right, the first time around. So there's two different types of ventilation in theater. You have the plan, um, theaters that you see general for the, you know, in general surgery or emergency theaters, uh, and a laminar flow that you're seeing orthopedics. So, we should have a poll, uh, iggy or Seb whoever's on would be great if you can set the first poll up. How many air changes are there per hour? Oh, I'm giving you the answer of accident. Everybody answered Iggy. You have to read them out because I can't see 46%. 400 23% 200. Okay. Not far off. So the plan, um, in a plan, um, theater, the number of air changes is around the 20 mark and around 400 in a Laminar flow per hour. Ok. In Planum Theaters, the air generally either comes down from the roof of the theater, the ceiling even or from the sides and it will exit through events at the bottom of the theater around ground level. But what happens when you open a door in this plan, um, theater? How much air gets moved? Any, any guesses? Nope. So about two cubic meters of air gets transferred from whatever area, the dirty area into the Planet Theater every time a door opens and I'm sure you can all imagine how many times the door is opened and that air is transferred during a case. So Laminar flow itself, we're going to talk about the different ways that Laminar flow works. But it is initially air that comes in through the roof of the theater suite. Okay. And within theater will have a theater table in the center and the Laminar hood um above the bed. Now for some theaters, this is quite long and it might go down to the floor, but we don't see that very often anymore. Most of them are, you know, around a meter or less in height. Some theaters have very short Laminar Hood. Now when the air first comes in, it's not only filtered but it is called and humidified. Okay. So it's not sending in warm air into theater. Any ideas what this green block is that the air passes into before it comes into the theater? Sweet. Ahap. A filter. Fantastic, Mike. What does Hep a stand for? Great um high energy. What's this last bit? Hi. Hi. Phone a friend if you want uh I guess the piece dancing particles. Um and then I'll leave it to my friends. The in a nominate someone might cause I can't see and yeah. Um okay. Uh Right. So high efficiency particular air filters. Okay. You might if you have, have a look at your hoover's notice that you have a HEPA filter in your, in your hoover. Okay. Um I think there's a poll question Iggy setup on HEPA filters if you can trigger that one. Have you done it? A G I can't he or C thank you. I got to read the question now, Iggy. What size particles are filtered from the help of filter? Mhm. 11 responses. Oh, 14 responses. Now, 42% 420.5. And then it distributed evenly across 0.111 point five. Okay. So it filters out 99.7%. Uh and they're usually faltering it around the level of half a micron. Okay. So your air comes in, it goes through the HEPA filter and then there's three different ways that that can then pass through the theater suite. So if we take horizontal rather than air coming in through the ceiling, it comes through the side of the theater, okay. And it passes across the patient. Uh and you'll see there as it deflects around the bed and the surgeon, it should mean that in theory if you're doing a knee replacement that actually clean air blows over the knee, but what's the problem with this? It's set up who's generally speaking, standing at the end of the bed during a knee replacement? Yeah. Yeah. So then that deflect off of the scrub nurses back up over the patient and then the uh the contaminated air can then fall down onto your knee replacement. So horizontal um laminar flow was not great actually for knee replacements in particular, but a little bit better for hip replacements because actually the scrub nurse, generally speaking, wasn't standing at the end of the bed in these setups then, so we then move on to what became known as vertical laminar flow where you do operate within a laminar flow hood and the air comes down and deflect off the patient. But you then have your helpful uh team member that stands on the edge of the laminar flow. And so air gets different comes down and gets deflected off of them into your laminar flow hood, which is known as entrainment. Okay. So then you've got dirty air that is then caught in the laminar flow area. So then came X flows. This is the logical progression. So what's the difference between X flow and vertical laminar flow? Any thoughts from anyone? What do we use today? Do we use vertical flow or X flow? I hadn't heard of it all. Okay. So we mainly use ex flow, okay. So the air comes in, it goes through our HEPA filter and it comes down onto our patient on the bed and it gets deflected away from the laminar flow area. So this is our laminar flow hood, the air has been deflected out but then it is trapped by coming up being pulled up into these vents. So the air is uh what we call an inverted trumpets. So it is going down onto the patient being deflected out of the laminar flow and then back up through X flow vents. Okay. So actually, if somebody comes and stands here, I don't know. Hopefully you can see my cursor that air actually doesn't go into the Laminar floor. It's much less likely to go into the laminar flow area. So you don't get this entrainment where you get Eddie's of dirty air going into the Laminar flow area. So you need to be able to draw the explosive it up and be able to talk about how it works in a basic science forever. So how do you actually know the air and theater is clean? You're a new consultant in a department, there's a few infections. How do you know that that infection is not coming because of problems in the air and theater microbiology, set of battery dishes and the theaters and assess them? Yeah. So yes, yeah, there is uh we'll talk about how, how you go about doing that. Absolutely. So firstly is to check that the laminar flow is on and that there's no alert. So part of the theater checks in the morning is actually the theater team will check that there's no fault on the laminar flow set up. Okay. Air cleanliness has to be tested in theater and we'll talk about how you how you do that now. Okay. So this is known as a slit sampler and is using plates in theater and it draws in a set volume of air which is 70 liters per minute over, over the plate, they then incubate it at 37 degrees for two days and then count the number of colonies that form on it. So, does anyone know what the definition of ultraclean is? And I tell you, it's to do the number of colonies that formed? Okay. So in terms of frequency of testing in ultra clean environments, the be testing every three months in theaters. Okay. Um And I've never personally seen anyone actually testing it, but they do do it. So you could speak to the theater team and ask if you wanted to get involved with the next time it's being done so that you can see how these work particularly got your exam coming up. It might be quite useful to have seen one of them and how, how it how they go about doing it. Okay. So ultraclean theaters need to have less than 10 colony forming units in the central area of theaters and in the periphery, it should have less than 20 colony forming units. Now, that's a perfectly reasonable MCQ question is also um something that you'll be expected to talk about when you're talking about Laminar flow in the exam in your in your basic science forever. Uh In a plan um theater centrally, it should be less than 35 less than one former colony unit of Clostridium. Okay. Generally speaking in a plan um theater that is not being used at that specific time. So just a storage level, if you like, there should be less than 100 and 80 in an empty plan um theater. So again, whistlestop tour of Laminar Flow. Um Any questions about how you would go about answering a question about Laminar flow. How long do you need the lemon or flow on before it's like up and working? Usually 20 minutes. Uh Can I ask you a question about the efficiency of the laminar flow? I've seen people put a vertical drape starting at the patient and giving it to the anesthetist that, that goes against the diagram we've just seen. Right. Yeah, absolutely. So there's a lot of um data suggest that doing that actually creates more Eddie's in some ways, the advantage of doing it is that it is blocking the an anesthetist out. And so therefore, you don't get in any entrainment at the edge where the anesthetist is. But that I think has been uh if you like a residual left over from when we purely had vertical flow as opposed to ex flow. So it does depend on what laminar flow you're working within as to whether or not it will have an effect. So if you are in a vertical flow, then actually, in some ways, it might be protective because it will stop those eddy currents coming in. But if you're an ex flow, it's unnecessary to do MS basically, I remember during COVID we were, uh, sort of worrying a lot, weren't we about, about COVID? Uh, sort of spread around by laminar flow. Uh, so I didn't realize the air got changed that much because we were waiting ages between patient's, weren't we? And the COVID, um, virus is much, much larger than those HEPA filters take out and it falls to the floor much quicker and much more quickly as well. Yeah. Just in hindsight that looks a bit looks excessive, doesn't it? Yeah. Yeah, I think the problem with events like COVID that happened a lot of things, advice was rushed out, wasn't it? And was generalized to theaters. So, uh not authors had Laminar flow. So whether they went for the path, you know, the weakest chain and therefore opted to keep everyone safe at the weakest level. Um, but certainly in the Laminar flow theaters probably wasn't less relevant. Yeah, thank you. No worries. Uh Loving every is Nicki here has a clinic finished. If not, I'll do another one, Nicki. Are you here yet? Uh I can see. No, okay. Are in theaters but um about Baron theaters. So, yeah, so places like Washington have got banned theaters. Uh Iggy. What's a band to, uh? Oh, I don't know. Actually I think you've been in once. Well, you basically walk in. Uh, so in terms of theater design, you've got a clean corridor and a third corridor, but you exit the anesthetic room. Um, all the theater spaces connected in one large space, they still had a central, they still had a central X flow um type laminar flow. Um And they discourage people walking into the 30 corridor which is completely open um but not in between theaters. Yeah. So a barn theatre, if you imagine, just imagine the setup of one theater but one really long effectively barn where you have four LAMINAR flows or set up individually, for example, And then each theater or pod if you like has its own theater environment in that area and it's climate is controlled within degrees. Obviously, there's movement between them but it has its own laminar flow hood. It has its own HEPA filters its share in the air across all of the theaters that going through each individual HEPA filter. You then are having explode just in your pod and the pod next to you will have X low in their pod and there's nothing stopping people walking from one pod to the next pod. Although you try not to and the anesthetic room will come, the patient will be prepped in the anesthetic room have the first prep done patient. The theater team are already scrubbed, waiting for that patient to come in in spacesuits. You catch the patient with sterile drapes as the bed is brought into theaters, no one will step into that laminar flow. So the patient is effectively pushed into the laminar flow and caught by the surgeon bought into the center of the Laminar flow, they're then re prepped and draped and you are in your own pod at that point, but they are share ing air, they have the HEPA filters but it is just one big theater environment. It follows the same principles of uh clean, sterile and dirty. Does that answer your question, Nikki? I'm not sure. Hopefully it does. Um I don't think we've got any of them. Anything. That's one of the things. That's right. Do you have any comments on the position of the lights if you have a vertical flow? Yeah. So vertical light position, obviously anything in the in the laminar flow, it will bounce and create Eddie's so invertical flow, it's a problem because if you bounces off and goes dirty or something comes in and bounces onto it, um you're creating contamination of your field. But with the ex flow point of view, if it comes down and hits lights, it will deflect out of the laminar flow and be brought back up into the X flow system. So uh it's less of an issue with explode than it is with vertical flow. Thanks but not avoidable. Everyone happy there. Uh In that case, uh Iggy has already spoken to us about the design of stems. So what we're going to talk about next uh If I find my slide is how they become loose over time and how osteolysis occurs because it's a really common topic to get in your exam to talk about osteolysis. So I guess to start off with the question really is, is, well, what subsidence Vicky as I know you there? So when the stem kind of sinks or leaves without the summer symptom? Yeah, within the cement mentor, is it normal or abnormal? So it's a certain extent it is normal because that's the your ex descent, for example, is designed to subside a little bit, but obviously it's pathological as well a certain point. Okay. Good. So, exeter stems we've already heard from Iggy are polished tapered stems. And their whole principle is is that as you wait there, they subside. And so on the end of your extra stems, hopefully you'll put on a what would be called avoid centralizer or avoid central or a centralizer. And that gives a bit of gap at the bottom of the stem that your stem can then subside into when that person weight best. It's not just about making sure the stem goes down the center of the femur is giving space for the stem to go into. Now, if you're putting in a, a narrow stem, some of you will notice that they're not really centralizes because it hasn't got any wings on it. It's just an end cap that the stem can subside into. It's just a few millimeters. So the stem is not up against the cement. Okay. What think about these X rays, Mike. So uh these two explodes of left hips. Um, the X ray on the right, as we look at it just, um, has subsided into the femur leaving an area of lucency, um, medial to the greater trochanter to um, the cement mental on the left as we look at it appears to be a little bit fluffy, particularly around the distal end of the stem or areas of lucency in those grown zones. Yeah. Good. What, um, if you're looking at this implant, what do you think the implants are? Uh, oh, is this a total hip replacement? Oh, sorry. Okay. So total hip replacement with a cemented stem and then uh un cemented. That's tabular component with the metal. Yeah. Okay. Do you think that's a normal cut position if it's a cup? No. Okay. Uh What do you think? Do you think it's a couple? Do you think it's something else? Have I led you into something? Could it be a type of hemi? It could be. Yeah. Yeah. Uh This is bipolar head. So it's just point out for everybody. Okay. So you can see the inner head here. You can you get the impression that there's something there and the position of the head in the acetabulum? Okay. So the actual acetabulum itself hasn't been reamed this bipolar hemi. Okay. Now, does that account for what we would probably not, except as an elective cement mantle. So this is cement Mental. That hasn't been well pressurized. Okay. I'm going to tell you that this on the left is an initial POSTOP X ray after their hemi. So we know that that cement Mantel has not been good all along. And obviously, it's not doing any better over time. Why would it? But what we can see is that the shoulder of the exeter stem here has subsided compared to where it was to begin with. Okay. So we've got a few millimeters of subsidence there and it really becomes difficult as to whether or not this is pathological or if it's physiological subsidence. So, uh with physiological subsidence, you'd expect this to generally have occurred in the first six weeks, but up to six months after the surgery and then anything changing in that stem after six months is more likely to be pathological. Thanks, Mike. So, just a reminder that this is the space at the end of a centralizer in this situation or you can have a wingless end cap that still has that gap at the bottom for the stem to subside into. Okay. If you don't put one on, it's got no space to subside into because you'll just have stem cement. Okay. Is there an a miracle value of how much is acceptable? It's up to 55 millimeters for up to a year. Um So I would go with that mainly because anything more than five millimeters is more subsidence than what you've allowed for physiologically with your end cap. Thank you. Yeah. So the moment you see stem that has sunk more than the distance of your end cap, you know that something else has to be going on because then you've got the stem and the end cap moving as opposed to just the stem moving in the end cap. Happy, obviously, that might be slightly different for brands. So subsidence we've seen on that last X ray that the position of the shoulder had changed. And over time, you then see that your stem subsides down into the end cap and on serial X rays, you can sometimes see that the end, you'll see the air in the end cap is or less okay, early subsidence um is what we see subsides by six months and we expect it to have fully occurred in that six month window, but they do split it up into early and late. Um And obviously, you generally will see uh loosening around the shoulder. You don't really see very much loosening between the implant and the cement mantle itself. Okay. Over time, if you start to see that you're getting lucency between your cement and the cement and bone interface, that's obviously more worrying of loosening in general as opposed to subsidence, which is always obviously gonna be pathological. Oh, loosening is obviously a problem. But what kind of problems do the patient's notice when they have loosening of a of a femoral stem pain? Yeah. What kind of pain do they get? Panels I think this is something of pain in the proximal femur or fi pain generally. Yes. They often get typing. There's really, um, classical symptoms that they get. That you're, if you're very clear about in your exam, your show the higher order thinking in a, in an intermediate case that if you kind of specifically probe for it, any ideas startup pain. Yeah. What startup pain? It's pain when they start moving after a period of activity. So when they wake up the morning, the first few minutes, it's painful all of it when they're sitting for a while, um, it gets painful when they start to move. Yeah. So very clearly, it's that pain when they start weight bearing because basically the stem that is loose is impacting into that bone again. And once it's impacted, then the pain, the steps become much less painful. So they will have pain when they initially start moving after a period of rest and then it will settle down. Okay. Now, go about their activities. They might have some low background pain, but generally speaking, the pain, the pain that they're sharp pain settles okay. When, uh, implants become loose, they create debris. So you have an immune reaction locally, but it also therefore creates some synovitis, which in itself is also painful as they become loose, you might get component malposition. And I'm sure in COVID you've all seen cups that were loose that have now spun, for example, and then you can end up with catastrophic failure where your implants break, okay. The more debris that is produced, the more likely to you're going to start seeing osteolysis and having bone loss, which then obviously becomes a problem when it comes to revisions. So, pain in itself is an unreliable predictor of loosening. So you can have a loose implant and not have pain. You can have pain and not have a loose implants. but startup pain is generally reasonably accepted. Um, as the main symptom that people will have. Okay. So I think it took me a while as a junior reg to really when somebody said something was loose to really realize what they meant by that. So what areas can be loose in uh this, in this case, for example, what are the two areas that I'm particularly looking at? We'll just focus on the stem for now, stem cement interface, right? Yeah. So you can get loosening between the stem and the cement and you can get loosening between the cement and the bone. Okay. Now, when you start talking about revision of paraprosthetic fractures, it becomes, uh, that's the difference between fixing and replacing, okay. But if you just say loose in your exam, I would as an examiner question you more about what you actually meant, okay, because actually there is a fracture that is going through the bone and involving the cement. And you can see that there is lucent line between the implant itself and the cement okay. And again, you can see that there is a lucent line here around the shoulder between the stem and the cement. But actually when you look at the cement and the bone that's well fixed, okay, there's no significant lucent line between that, that cement and that bone. Okay. And again, distantly here, there's not really any significant loosening between the two and on serial x rays that might have always been there. But when you come up onto this medial side, you can see that there is a gap between the bone and the cement. Okay. So we've got a stem that is loose in it's cement and a stem that is a cement that is loose within the bone. So would you be thinking more along the lines of revision or fixation for this patient? Revision revision? Okay. So when would you think about just fixing? Oh, well fixed, well fixed them with good bone stock? Okay. If they're very, how do you know? So if, if the patient is very old and afraid or would you just consider fixing it? Mm. So what we're actually doing when we're fixing a paraprosthetic fracture around this uh around uh an exodus stem is that we've got a stem that is loose within cement, but a cement is well fixed to the bone. Yeah. And by reducing the fracture and holding it together, I'm tightening the cement back up around that stem and recreating the wedge that that stem has sat in. But actually that patient's going to be fine once a fracture heals because the cement is still fixed to the bone. Yeah. But if I try and fix a patient and put the cement back together again around that them and recreate the wedge, but all of the cement is loose within the bone and you fix them, that cement is still going to be able to piston within the bone because the bone and cement is loose. So it took me a while as a junior reg to really get my head around what people meant. And I think the Vancouver classification can sometimes be a bit confusing when it says a well fixed implant. But naturally, there has to be lucency when there's a fracture between the stem and the cement. Okay. So what you're looking at with these is what the loosening is like between the cement and the bone. Yeah. And for me here, this is a loose cement mantle and would likely do better with a revision depending on what the patient was like. Okay. And you might have to then counsel them if they're not well enough for a vision that you fix it. And if they're symptomatic of a loose stem later revise it, okay. Everyone clear on the differences between implant, cement and cement bone interface loosening. I'm gonna hope that silence means yes. But if not, you can have a chat with me later. Good. So don't underestimate the importance of the serial x rays because actually it might be that this was just a bad cement mantle all along and that, that it's not loose. Okay. Another example here, not a great X ray, it hasn't come out very well. Um What's your thoughts on this one, Mike? What components are of the femur are loose? So uh the stem cement interface, his issues um and on the lateral side, the bone cement interface appears loose as well. Yeah, both, both, both elements are loose, aren't they? So thoughts are you going to or if it, so this will require revision surgery as well? Okay. So Mike mentioned Gruen zones and uh for the acetabular component, there's the channel and delete zones as well. Okay. Uh These are classic papers that would be quite easy game for you to be able to discuss in the exam, plenty of opportunities to describe hip x rays um in basic science or in your adult path or in your trauma station. So you should be able to um real it off. You may want to draw it, for example, in a basic science station. So it looks at both the ap and lateral views of your stem and just uh the A P of your cup. Okay. So you should be able to go through those pretty quickly. If you haven't read the initial papers, they're quite nice papers to read. So I thought we could do some examples. Okay. Um any S T three signed in or S T fours, any five or six is. Yeah. Sorry. Ok, I'm here. Okay. Hi, Kem. Gone. Um um let's just focus on the hip on the right. Why don't we first talk about how the components are fixed in? Okay. Um So a p radiograph for the pelvis showing uh bilateral total hip replacement. Um on the right, you have a cemented stem and un un cemented, uh couple of cup with screw augmentation. Um There seems to be when you compare to the left hand side, there's lower quality cement mental. Um um and there's a degree of loosening. Well, yeah, there's definitely some subsidence compared at this, at the shoulder of the stem. Um And I say there's loosening between the bone cement interface. Yeah, absolutely. So you can see a line forming here, can't you coming down? And then here there's something suspicious going on, isn't it? And you can actually follow the cement mantle all the way around, can't you? And there's these areas where there's a line between the cement and the bones. So I would say that this stem is loose, agree with you. It's likely that there's been some subsidence, but unless we've got serial x rays, we probably can't entirely comment. Can we, what do you think the sources of this occurring camp? But you can phone a friend if you're not sure. Um It could be the cement mental. I know it looks like the femoral had this s centric. Yeah. What does that mean? Uh So as it's not in the center of the problem is probably somewhere of the uh the liner. Awesome, well done. Yeah, perfect. So the moment you see an E centric head in an on an X ray, you should be looking for the associated lucency with it. Okay. Uh For the loosening of the stem when you're describing that X ray in your F R C S, it's a hybrid construct with a cemented stem and an unscented cup. You've got s centric position of the femoral head to suggest that there's uh where in the polyethylene liner and this is associated with lucency is ingrown zones one all the way through to seven and potentially even some cow car resort option. Okay. Well done. Can you picked all of that nicely? Well, um any perry exam that would like to comment on any other components of this implant? One other thing that I would want someone to comment on F R C s about the implants themselves. Nothing to do with the, the wear side of things. Hi kid section here. Uh It looks like the couples bit open uh contributing to the eccentric where. Yeah. Uh Yeah. One more thing about this. If you compare the two femoral heads, do they look similar? No, they're different. Know what, what's there? What's the problem or what potential problems do you get with the femoral head that's been used on the left? I'm not sure about the potential problems with the femoral head but the offset seems a lot bigger than the, uh, the left side. Yeah. I'm not sure about the actual femoral head itself. Okay. Any parts of the femoral head that are not normal or do you, do you know what this bit is? Skirt? Yeah, it's a skirt. So, um, I'm not sure who said that then. But um, so yes, so this is a skirt. So what does a skirt? What is, who said skirt? They're right. Whoever said it? Yeah, I can't. Who, who is it? Uh Oh, okay, fine. Iggy. What's the skirt then? Uh, so in terms of increasing offset, a skirt is, is added onto the femoral head to allow for increased offset. So, therefore, in this situation, uh it's, it's, it's use is to increase all set as well as, uh, but the issue with that is that it's got increased risk of impingement, uh, any advances from anyone. So you're right, it increases offset. Okay. Roughly speaking, when do you start getting a skirt added onto your femoral head? Eight plus eight. Generally to be anything more than plus eight generally comes with a skirt. Okay. The problem with skirts is that it increases your head neck ratio and so you will impinge earlier in your range of movement and therefore you can leave out and dislocate. So the moment in the F R C S, you see a skirted head being used and in real life, generally speaking, something hasn't been quite right in that hip replacement. So, go looking for the problems, you know, features of abnormal wear that might be associated with recurrent dislocations and things like that. Okay. Good work guys. I've got another one here. Uh Another type of that stem. Can you explain the previous picture? Oh, it's a really old stem. So it just has a marker in the centralizer? Okay, Vicky. Do you want to describe these components? Yep. Let's say again it's an Ap Purvis radiograph. Um You have got unscented stem and unsub vented cups, a uncemented hip prosthesis with square augmentation. Yeah. Um your bearing surface. So, so is it ceramic on Polly? Yeah. Most likely ceramic and poly. What kind of ceramic do you reckon? It is. Uh is it highly crosslink know polly? So the ceramic head here is not modern ceramic because if you look at a ceramic heads now you can't see the so much see the difference between the trunnion and the head. This is the previous generation of ceramics. All right. Good. Uh Do you think there's any loosening on this stem? So it does look like there's a little bit of leasing probably in green zones. One too or maybe seven? Yeah. Good. So everyone see that. So you talk in this one, obviously, you don't talk about the cement bone interface because there isn't one. But actually the implant bone interface there is lucent line coming down here, isn't there. And again, coming up on this medial site. Great. Last one, anyone want to take this with them, I can give it a go Kate if that's okay. Yeah, go ahead. Go for it. So it's a radiograph. A PN lateral, right, total hip replacement. The most obvious abnormality is that the uh the, the cup is loose and has changed its position. It's dislocated. It is a cemented prosthesis. So both, both the femur and I think the cup are worse cemented. Um, there is also, uh, loosening of the cement bone interface that grown zones, one too, probably 345 as well on the AP view, looking at the lateral view. Um, it's not very clear here and, and to be honest, it's difficult to see on this, on the, on the computer as well. But again, you can see the dislocated, uh, liner. Is there another line of the cup? And, uh, I guess if you look really hard that you can see the lucency ease and zones 89, 10, probably 11, 12, 13 as well. Uh, so in conclusion, you have a cemented total hip with a dislocated cup and the loose, uh, stem. Yeah. Good. What's the investigations are you going to do? Um, so I'd like to rule out an infection first. Um, so I do full blood count. Um, e S R CRP. Um I would uh potentially do and potentially I would do aspiration of the hip uh to see if we could grow any, any, any bugs on culture and do uh the sign over short test as well. Um And uh then basically to the patient up for a full revision. Yeah. Would you get a CT? Yes, I would, I'd like to see the bone stock, especially on the acid tabular side um to, to plan the revision. Perfect. So um these kind of cases, if you've got them available, the serial X rays are really important are really quite useful because what you, the one thing that when I look at this, I, I wonder is why is the stem so undersized for this femur? So either it's been undersized all along or have they had a poorly cemented uh revision? So, you know, the serial X rays are actually quite useful. The stem itself is in various, isn't it? So that's another kind of uh higher order thinking just to, to mention there as well. Uh Biggest thing in these situations is to exclude infection. Okay. Uh Don't go down the route of aseptic loosening good. Uh So how does it become loose? Well, where produce debris and the number of uh debris particles is obviously inversion aly, inversely proportional to size. So if you have the same amount of debris that's produced or same volume of uh polyethylene that has been worn off uh the more particles you have, the smaller they're going to be okay for some reason. They word that very oddly. And Ramachandran and you can really get caught up over a paragraph in Ramachandran. But that is basically all they mean for the same volume of where, um, the more particles you have, they have to therefore be smaller. Okay. So, debris can become biologically active. And that's generally speaking around the 0.1 up to 10 microns in size. So if you remember one, that's quite easy, isn't it? Um And they're engulfed by macrophages. Okay. Now, the smaller particles are engulfed, but the big particles that are produced can't be engulfed by the macrophages. Okay. So it's a small particles that are biologically active and then these macrophages then become active and that's where osteolysis starts to occur. Okay. And the amount of active uh the number of active macrophages depends on the volume of where the number of particles and then obviously the size of the particles. So if you actually you had where there was just of some big particles, it wouldn't create a big osteolytic response. But if you've got lots of biologically active particles, you're going to have more of a response. Um So we're gonna come to the cellular side of how Australia this occurs in little while. Uh what I wanted to ask you though was what kind of stem this is, we're going to go through a series of X rays, you know what brand it is or not brand, what type of what, what you would refer to this as Iggy composite beam cemented mono block. What stem is it though? Why is it um on a block Charlie fixed off? Yeah. What's um on a block then? Mon block is where a stem is not modular, especially in terms of head as well as femoral stem. So it comes in one block. So it has a fixed head size and it has a fixed offset. Yeah. What head size is this? Yeah, 22.2 to 5. Good. So whenever you see a Charlie stem, like this always be worried when it comes to revision situations. If you're not revising the stem, you need to get small heads in. Okay. Uh Lovely. Uh There's one more pole I think looking at the number of particles are produced with each step which is why the 22.2 heads relevant. So is that 2225? Question? Right. Yeah. Yeah. Questions up. Lovely. Yeah. Okay. Most people put in 35,000. Okay. So yeah, that's roughly the right answer. So around 38,000 sub micron particles are produced with every step. It's just quite, I hadn't realized that's a lot, isn't it? Okay? Uh Okay. So what's the effective joint space? Slightly different principle here? But quite relevant for the exam if we come back to this initial X ray that we looked at any ideas on what effective joint spaces? It's the space that can be filled in with particles of where? Mhm. So where would be affected on, on this around this implant? So this space generated by the volume lost from the uh where on the polyethylene. Mhm. So anywhere that the little particles can get down, so they can get down around the implant of the step. Okay, they can get around the cup and the bit that often gets the gotten about is the effective joint space includes the interface between the screw and the bone of yes tabular component. Okay. So you will see austral icis occurring potentially all the way around your screw as well. So again, you something that to take your exam on to the next level is talking about the osteolysis around the stem and you're channeling delay zones. When you start seeing license around your uh screw, you can say that there's extension changes in the effective joint space. And then they might ask you, what is that okay? Uh So this is clearly not in the right animation format but the problem with this wear and the debris that has produces that it becomes self sustaining. So you have where it produces debris is biologically active, the macrophages take it up, the stem becomes loose, you get micromotion in the components which creates even more aware, which creates more debris becomes looser, creates even more micromotion, perhaps even getting into macro motion. When you start seeing these cups spinning. Okay. So this is how the process becomes self sustaining. So we're gonna go back to having our active macrophage. Okay. They produce cited kinds which are your TNF alpha interleukin one and your interleukin six. And then they obviously have effects on both your osteoblasts and your osteoclasts. And it's not uncommon for them to show you an S centric uh head on an X ray with lucency, these in the green zones, then ask you how it has happened. So you need to be able to describe these uh effects of these cytokines. Okay. So here we have an osteoblast and osteoblast will release rank ligand when they're stimulated. And TNF alpha will increase the amount of rank ligand that's produced. Okay. That rank ligand will bank bind to the rank receptor on your osteoclast, which will then activate them. And then you will go down the process of how the osteo class works, how the integrity uh allow the house ships look united to be sealed, the acidification and how the osteoclasts can then break down the bone. Okay. But there's other effects here. And that is that your interleukin one and your interleukin six can directly activate osteoclasts. Okay. But also that we have other factors uh like the monocyte lineage activation, which means that you produce even more osteoclasts than you have already. So, these are the processes that occur that allow the bone cement or the bone implant interface to show signs of lucency okay and become loose. So you need to be able to roughly draw these processes out. And it does come up as an MCQ question to talk about the effects of TNF alpha interleukin one interleukin six. OK, interleukin one in itself, in addition to its effect directly on osteo class is it has a direct effect on the osteoblast to switch them off. So the question is how much interleukin one and TNF alpha plays into this? I don't know, is my honest answer, but it can prevent bone being formed. And so therefore, you have the effect of re know remodeling potential at the bone implant interface. When this is occurring? Any questions about osteolysis? Anyone, how do you differentiate between physiological and pathological? Are there any criteria for that other than the time? So the physiological subsidence will only be seen around the shoulder of the stem? Okay. And you will see that your stem has sunk down into your end cap and it will only be a few millimeters. And it generally, as I said, happens up to about the six month mark, you might see it up to a year or two years following the primary surgery. Anything that happens later than that, that isn't already seen on the serial x rays is suspicious. Anything that's more than a few millimeters is suspicious because you've only got a few millimeters at the end of your end cap for it to subside into. So if it's actually that the stem and the end Kappa then subsiding it will be more than a few millimeters. That's pathological. If you have lucency between your cement boned face, that's pathological. Unless it's that it's been a poor cement technique to begin with. Yeah, just thinking about. So, basically, anything in zones 2 to 7 is basically be ecological by definition. Unless it's a poor cement, it need to begin with. Okay. I think we've got Nikki. But is that Alex things, Nicki's got a paper on uh Laminar Flow Heineke. Hope your clinic wasn't too bad. Sorry for the late joint. No worries. I'm gonna stop share. Ng left knee, you should be able to screen share. Yeah, I just uh relying on the NHS wifi no restaurant. Hopefully that's projecting perfect. Um So I've been asked to present the evidence on Laminar Flow. Um So I've take through that. So when I was first asked you this, the first thing that came to my mind was the sterile field and times as a medical student being asked to step back and that sort of thing. So um hopefully this is something that is not an uncommon image that's conscious of mind for many people and thinking about Laminar flow. So it's quite an interesting thing to look into. So I started by doing a general literature search and the thing to say about Laminar flow and the literature surround it is that many of the positive studies and the earlier studies focus on colony forming units and can contamination as a surrogate marker for infection. Rather than looking at the direct relationship between laminar flow and infection cases themselves. Um of the literature is out there and that is available, looking at the relationship between laminar flow and infection cases. Any of them are small studies with small numbers of patients recruited and low level level and observation studies mostly. Um that is probably because it's a difficult area to get high quality level. One evidence in purely because surgical site infections are relatively rare in their occurrence, so to speak. So large recruitment and adequately powering these studies is probably quite difficult. So as a result, looking at the general literature surrounding laminar flow, uh the take home message is there's still a lot of debate. So I'll take you through some of the key papers. So the t papers that I looked in detail at where the Bischoff 2017 lancet paper, which was a systematic review and meta analysis of the data available at the time. And then I also want to look at something a little bit more recent. So and I talked to you about the Morris paper from 2020 from the general Children. So the lancet systematic reviews done in 2017, um it's a high impact turn and I'm sure I don't have to tell you. Um it was a systematic analysis of um I think it ended up being 12 studies in total at the end. Um it spanned quite a big time period. So in 1919 to 2016, and crucially, it covered any study and included any study from any specialty, um looking at certain surgical site infection and the effect of laminar flow. So I think the groups of specialist is included, we're trauma orthopedics, vascular general surgery and a couple of other outlaws. The reason they um it did the systematic really was that they were prior studies prior large RCT suggesting that um laminar flow reduces uh the rate of surgical site infections, but these weren't reproducing larger studies. So they did they more detailed look into the available evidence um including a systematic review that was done in 2012, which found that uh laminar flow was associated with an increased risk of surgical site infection for orthopedic procedures in particular. So the question that was asked is, you know, does the use of a lemon, lemon airflow in the operating room reduce overall or deep social site infection? So the methodology that really clearly defined search strategy, they used a prisoner statement, they population to find inpatient and outpatient, any age, any operation. They didn't exclude pediatric studies from it. The comparator interestingly with any other airflow system for the studies. So uh didn't necessarily need to specify which alternate airflow system, just any other airflow system with or without hyper uh carried out lots of sensitivity analysis. Um and they excluded studies that went in the following languages, which I thought was interesting. So it went for French Germans fash and the primary outcome was the deep surgical site infection rate amongst the studies. Um It's worth saying that they did carry out sub specialty, specialty analysis and then again by different surgical procedures as well. And also that the majority of the the literature is orthopedic. So what they found was that there's lots, there's lots of studies out there, much of them are low quality and observational in nature. So of the 12 studies that included most of them were observational, but it is the best available ahead of time. They didn't, they commented they didn't have any publication bias and they found that there was a lot of heterogeneity between sort of clinical and statistical methods, the probability. So in their statement of results, they said that the probability of developing a deep stage of site infection following total hip replacement is higher with laminar flow, but that it wasn't statistically significant. And they also commented that the evidence available was inadequate. Comment on whether or not the probability of developing sort of site infection for other procedures, specialties was essentially insufficient. So they concluded that laminar flow based on their synthesis of the evidence does not reduce the risk of surgical site infections for orthopedic procedures, primarily hips and knees. And therefore it should not be used as a preventative measure to reduce the surgical site infections. There was lots of talk within the paper about uh recommendations, the impact of which I'll go into later on in talk. So the limitations of this study and probably most notably was that a lot of the evidence that was collected was from large databases or registries who's primary person is not to collect data on surgical site infections. So a big scope for misclassification Um and also, you know, it may well be that there was a laminar flow theater, whether or not it was functioning, we don't know the other thing to say is that the dates that they chose to look at the studies from, we're just arbitrary dates plucked out the air. I can't really see where or why they chose the interval that they did because there's a couple of large are CTS Prize in 1990 that sort of against the use of laminar flow, they were actually excluded. So I'm not sure why they chose a dates. Um And many, many of the studies they did include didn't specify what alternate airflow system was actually use. Again, a lot of studies not saying whether or not they use head path. And then just the vast propensity for confounding to be introduced with multiple studies, multiple surgeons, um multiple obviously practices between hospital, between surgeon and system used the other thing to stay and and that they did state within their sort of discussion was that the quality of the laminar flow systems being used between studies. So clearly, the the laminar flow in the 19 nineties is likely to be a little bit different from the laminar flow systems that were available in 2016. So then just wanted to briefly mention before we talk about the application to practice the Morice paper from 2020. So again, another high impact journal, this is a level one RCT double blinded prospective design. And they split it into two groups with 43 patient. So roughly 20 in each and they did a year's follow up specifically recording presence of the SSI again using registries. So they specifically looked at shoulders and they asked the question of whether a localized laminar flow device was effective at reducing colony forming units um rather than a generalized form. Okay. Um So again, they did a nice clear description of how they collected their data, including how the frequency of colony forming units and how they measured it. They also looked at microbial air contamination as well. They did robust analyses which is quite good and paranal icis prior to that, their primary outcome was colony forming units, but they did make a comment on the presence of surgical site infection as part of their results. And they suggested that laminar flow is associated with lower counts um in and around the wind. Uh So this study I thought was interesting and worth discussing because um surgical site, infection wasn't the primary outcome, but they did look into a year and they used the registries to kind of make that link. Um, the studies that design was good, but they did comment in there that they, you know, the blinding didn't really work. The surgeons pretty much worked out because it was a localized laminar places that they were using when they were using a diathermy. They could essentially see whether, you know, the change in the stream work. So they worked out which patient's did and didn't have it pretty quickly. Um The other thing too that that should be acknowledged here is that the most, one of the most common bugs that's associated particularly with surgical site infection in Children arthroplasty is, you know, a bug on the skin rather than an aerosol or an airborne bug. Um And therefore the likelihood of surgical site infections for upper limb procedures was being lower than lower, lower than lower limb procedures. Um It's going to be even lower than that when you're looking for a uh sort of bacteria. So um questioning sort of the applicability of this study. Um I mentioned the use of registries already. And then also the other thing that's not been mentioned yet, but it is worth introducing is the idea of warming devices, patient warming devices creating turbulent flow and therefore impacting potentially the results. So in that way, have, you know, this study was sort of selective in its reporting of the exposures. So there was I think analysis and someone else is done for a very various confounding variables, including things like the number of people coming I/O of theater. But haven't mentioned things like patient warming devices, which there is a reasonable body of evidence suggesting that it does affect the quality of laminar flow. So they were slightly selecting the way that they reported that. So looking up the systematic analysis and also the other studies, how can we apply that practice? Well, the first thing to say is mostly the many of the studies that were earlier to a lot of this where before routing patient warming devices we use, there's lots of hypothermia and that would have impacted on the rate of surgical site infections. Um whether or not the early a laminar flow systems were adequate. Um and maybe in that way, introducing positive bias in the earlier studies. Um Yeah, from the lancet paper, it would appear that there isn't much a strong evidence actually in favor of laminar flow and reducing surgical site infections. But the key thing to take away, I think from the synthesis of evidence is that there are few studies looking into the direct relationship between surgical site infection and air quality because it's a difficult thing to do. Um And also then just to raise this idea of the pain, the the effect of patient warming um devices on laminar flow and its efficacy and there is, there is stuff going on in relation to that now and and has been in the past. And so it leaves me to a question of where next and what else is going on and what else is relevant. So, um there has been a few attempts at looking at the association between air quality and surgical site infections. Um there is, I think that there was a trial done in 2017 looking into the effect of patient warming devices. Um So, you know, the like the bear huggers versus something that's been more like an electric blanket and therefore doesn't use turbine air pro um on surgical site infections within 90 days. And then a pilot published in 2017 and there's further trials and that I'm going. Um so, you know, raising question of whether or not, you know, we should be looking into um that as something that may have confounded the studies that have been done to date. So in summary, there isn't really a causal link that's been established Tween laminar flow and surgical site infections within the literature available at the moment. Most of the studies promoting laminar flow use colony forming units as a primary outcome rather than a direct link between um surgical site infections and their methods. So I think it's safe to say that there's insufficient high quality data suggests that lambda flow does reduce surgical site infections. But it's possible that there might be a role. If a role for it, if air quality presence of surgical site infections can be established and we can better control for confounding variables. Um But that would be difficult to do on a large scale uh for obvious reasons, just my references. And thanks to you, Hammad, you helped me find all this literature. That's great. Thanks Nikki. That was really useful. Actually, hopefully given quite a lot of kind of food for thought people, people sitting there part to use for answering the basic science question on that. So if you were asked how laminar flow works, you could then follow that up with some of this information. Can you try and take your answer to the seven or an eight? So, um why do you think that there's that discrepancy between people choosing to look at surgical site infections compared to looking at the CF US? I think because the C F U S are just something that's it's easier to measure, isn't it? And that, you know, there's lots of different ways to do it. There are people that have, have you looked at the different number of particles that you can measure? It's just something that you it's tangible and can yield results is probably easier to do and getting data useful data about surgical site infections without all of those confounding variables is nigh on impossible by the looks of things unless you are using a large registry, which I think is historically what people have done. Um, but they're probably, uh I think it just take a lot of doing, wouldn't it would take, you know, take an international effort? Um And specific focus on it also depends on what kind of SSI is, isn't it? Because actually the number of people that might get a superficial wound infection and get treated entirely in primary care won't necessarily flag on a registry, won't they? But they have had a surgical science infection. So there is a discrepancy isn't there of how you actually even look at the outcomes for these. That was really useful. Thanks Nikki. Any questions for Nikki from anybody? No, fabulous. Thank you Nikki. Uh What we're gonna do is we're going to finish off stems by talking about how they fail. Then we'll have coffee and we'll put up predominantly for a little while about cups. Okay. Uh So maybe 15 minutes and I'll have a break. Mm OK. Heavily. See the slides. So uh stems fail and actually around the region. Hopefully you guys will have the opportunity uh to assisting revisions and see how you can take out the broken stem. There's a reasonable size series of them out of knowledge that was published, I think the year before last. Um But there's different ways that stems can fail and that can very much be, you can describe it based on your X ray findings that you have in front of you. Um These are the modes of stem failure. This is a classic picture that everyone will see if you put Google stem femoral stem failure into Google images. Okay. And the first ones are mainly talking about piston ing. So this is either lucency between your implant and the stem implant and the cement serie or the cement and your bone interface. So this is the classic classic that we see where it's loose all the way around and actually the cement is pissed inning within the bone. Okay. Less likely that we just see that the implant itself is loose. But if you downsized a taper slip from say a three down to a two and you didn't put any extra cement in when you did a instrument revision, that's what it would look like on the X ray. All right, you see lucency is in all seven grune zones if it's an interface between the cement and the bone, and that's a pretty easy straightforward one to describe on your X rays. When you see it, the next three become a little bit harder uh in terms of thinking about how they happen. Okay. This is a classic example of lucency is in your group zones, one through to seven, there is a, a line between the cement and the bone all the way around the implant. Okay. And again, you can see that there's some changes in the Eurozone's one and maybe also in, in two and three. Okay. So this is entirely loose, pretty straightforward one to get in your exam, the kinds of problems that you would face when you come to revising, this is making sure that you get down the fairway. When you're removing a cement, the risk of a federal perforation here would be quite high and the risk of damaging what has become a slightly odd shaped trochanter and and a trochanteric fracture would be quite high when you look at this. Okay. Um So if we have a stem that has got medial migration and is pivoting around this central point and the distal end of the stem is going laterally because of the loss of support in the superior and medial aspect. This is known as your uh medial mid stem pivot. And because it's pivoting in the middle, you will end up with a cement line fracture in that level, but you may not see it on the X ray. And a response that you'll see on your X rays is that you'll get sclerosis on the lateral border where the stem is tipping into various. Okay. The body is a stress response, isn't it that it's having, it's thickening that lateral cortex. So this is medial, mid stem pivot. So the classic things you'll see on your X ray is your lucency. On the medial side, your loss of your superior medial support, you might see a cement fracture and you'll see that there's some sclerosis on the lateral side of the cortex. Okay. And so you could describe the X ray and you can say that this is consistent with medial mid stem pivot. It's not a very common one to see coming up in the exam. Okay. The next one you have is cow car pivot. Uh and is more commonly seen in uh collard stems. Again, I don't think there's very many people using collard stems in east of England. Um but on hysteric X X rays, you'll see it and sorry, I'm gonna sneeze in that you'll end up with lucency is in your distal zones and around the tip of the stem and it will pivot on the couch car itself. And in response to that, you'll end up with sclerosis on both the medial and lateral side of the femur if it's been there for a while as well, be modeling response again. And so you compare that up quite nicely on your X ray description and then to say that that's consistent with the calcar pivot. So you'll see a collard stem distantly, it's loose with sclerotic changes on both the medial and lateral sides of the distal femur. Okay. The one that we just spend a little bit more time talking about is bending cantilever because this is the one you're more likely to see in our region were also more likely to see it. I think in the exam. Okay. So what happens is you have a stem that is very well fixed distally, okay. But in the proximal zones of the femur, there is lucency between the cement and the bone interface. You end up with a stem that is well fixed distally and it can toggle at the top. Okay. What happens over time is is that the actual implant itself fracture? So you get a broke a prosthetic fracture as opposed to a peri prosthetic fracture. And the moment you see that broken femoral stem, you know, it has failed because of bending cantilever. Now, it might be that you've got a really good cement mantle and then it's loose. There's been wear and lucency at the top that caused this difference or it might be that the stems oversize and it's just really tight in a narrow isthmus, okay. And this is what you'll see on the X ray. So it might be very subtle and some of you may not be able to see it on the projection here, but there is an ever so slight step in the, in the femoral component and they will complain of pain and then at some point you'll do an interval, X ray and the stem will have broken. Now, this one's not so obvious that they haven't got a centric wear in the poly, but you can see that actually they are loose here at the top. Ok? Not so well supported. And there is lucency between the cement and the bone interface here medially as well. So we've got our changes in one and two and six and seven. But distantly, there's no loosening. So this is well fixed, distantly loose proximately and it breaks between the two. So how do you go about revising this implant? Any thoughts, any techniques anyone seen being used already? Anyone seen any broken stems? Is this one that would require an E T O? You may have to get to an E T A? Yeah, absolutely. Uh There's a few things that you can try beforehand. But yeah, E T O, if you can't get it out is the easiest way. But there's got more rehab difficulties for the patient because you've then got to wait for your osteotomy to heal more blood loss, et cetera. Okay. Can you reme into the, if you can take the proximal part up, can you remin to the distal um part of the stem and you something to extract? Yeah. So you can take the proximal bit here is quite easy to take out and then you'll be left with this broken stem down a tube that you can't quite reach. So one of the things that you can do is you can drill into it and do a reverse cut and you might be able to back slap it out. So that's one way any other, any other things people have seen being done, anyone seen this done at Norwich? So you can get a court Ing Rima or like a crown rima that's about 10 millimeters in diameter. You can over reme the metal implant that is left distantly with that rema and you end up taking away some of the cement over the top of it and you might be able to then get hold of it and, uh, and retrieve it that way. That's quite an easy way. Often. What happens when you over remit with those reamers is that the distal stem gets jammed in the remote. And as you take out, it comes out with the stem inside it. And then if that fails for you, what, what could you do before you get to the point of doing an E T O? Anyone heard of a lateral window? So you can make a little hole in the femur uh with a, with like a minus or expert. And then you can make with a little ridge within the implant itself and you can knock the implant back on itself. And I would make that lateral window where I want to make my E T O. So if it fails, I can join that up, okay. And you can redo one arm if you like of your E T O, which might just be enough to loosen up the bone cement interface that you can then retrieve the stem before you progress on to doing both passes of the E T O. So it's trying to keep the tube, a tube, the femur a tube. If you like for as long as possible. So that it means that the patient recovers quicker. So if you get faced with a broken stem in your F R C S, this is the sequence of events that I would run through when I was trying to revise it and just shows like a logical progression and uh severity of how that patient's going to recover if you like. So try and over remit or drill into it first, a lateral window to knock it back on itself. Uh I call it an episiotomy. It's not really an episiotomy. It's just the first part of your E T O. Okay. So you're only doing one cut in the femur. So effectively, it's just a tube with a line in it, a cutting it. And then if that fails, then an E T O to extract the distal part of the stem, this is an absolutely beautiful station to get in your F S E S because you can for very easy methods that to think of, but it shows higher order thinking. And then you can talk about austral isis, you can talk about your growing zones. You can talk about the mechanism of the way of which you're gonna go about revising this. And actually it, it is really a gift of a station if it comes up. Okay. So this is bending cantilever, okay. So where it breaks the actual implant itself, breaks any questions about that bit from anybody that is probably the quickest whistlestop tour that I could do on uh stem failure. Ultimately, it's pretty straightforward. You just about just about pattern recognition uh to understand why you will see those um X ray changes. Uh Denise has asked a question about, do we need to exclude infections for bending, cantilever? I think uh in life and in, in the exam, if you are going to do a revision for someone where there is loosening between the bone and cement interface, I personally would want to exclude infection before doing major surgery on that patient and putting new implants in without knowing for sure that or at least reducing the risk of uh missing an infection for that patient. So as a minimum CRP esr and a full blood count and if those are raised, I would aspirate those cases or if I have a suspicion in their previous history, uh you know, previous would affection or anything like that, I would aspirated them before revising, but I probably don't have any science space behind that other than uh if there is loosening, don't just assume it's a septic, any other questions? No. Uh let's have a coffee break then until 2 35. Okay. We'll finish up with some cup design and hopefully have an early, early finish. Okay. Thanks guys.