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Fracture Related Infection: Principles of Diagnosis
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Fracture Related Infection: Principles of Diagnosis
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Segment:0 .
IAN KENNEDY: we are into the second session in the BAJIS webinar series. I'm Ian Kennedy. I'm the BAJIS educational lead, and I would encourage you all to join the society. It's currently free of charge. It'll keep you updated and all our other upcoming educational events. If you've got any questions for the speakers, please type these into either the Q&A box or the chat box at the bottom of your screen and I will go through these at the end of the talk.
IAN KENNEDY: So our session today is going to focus on fracture related infection, and joining me as co-host, someone with a vast amount of experience in this area, it's current BAJIS President Elect, Mr. Bilal. Jamal, so over to you, Bilal.
BILAL JAMAL: Thanks, Ian.
BILAL JAMAL: Good evening and thank you to everyone for joining in today and hopefully some people can join us via recording after the fact.
BILAL JAMAL: It's always fun to do these things because you get to pick your friends and ask them to speak, and I always find that I learn a huge amount from that. Deepa is going to be speaking, first of all, and I'd like to take a minute just to introduce her. So Deepa is a consultant in Birmingham at the Queen Elizabeth Hospital. She's trained in Wales initially and then has had fellowship at the Nuffield Orthopedic Centre, which is the only dedicated infection unit in the United Kingdom in the form of the Oxford Bone Infection Center that has gone on to form a large part of our practice going forward.
BILAL JAMAL: But in addition to that, Deepa also has a significant interest in education, and in advancing orthopedics more globally. She's been past chairman of World Orthopedic Concern and in addition to that is currently the chairperson of the Specialist Advisory Committee. So there's a huge amount of wealth of knowledge there available from Deepa and I'm hugely grateful to her for agreeing to speak on fracture related infection and principles of diagnosis.
BILAL JAMAL: So over to you, Deepa.
DEEPA BOSE: Thanks very much, Bilal. It's a very, very kind introduction. Thank you and thank you for inviting me to speak. So I'm just going to see if I can share my slides with you. OK. And hopefully that's gone on to a slideshow that someone could just give me.
DEEPA BOSE: Yeah is that OK? OK lovely. Thank you. So, yes, thank you very much for inviting me to speak. And the focus of my talk will be diagnosing fracture related infection. So the incidence of infection after trauma varies quite widely in the literature from 6 to 15%, depending on which papers you read,
DEEPA BOSE: but there are certain conditions that it seems to be associated with, such as the injury site and complexity. So the more complex the injury, the higher the risk of getting an infection. This particularly applies to things like open fractures. Then it is also related to the patient's comorbidities, the number of operations et cetera. So it's related to patient factors and injury factors really.
DEEPA BOSE: And we all know that it is common after open fractures. So why is bone infection in general a problem and I'd like to introduce you to this concept of the orthopedic ostrich if you haven't heard me speak of it before. So bone infection is a problem because it's difficult to diagnose and it's difficult to treat and so we're going to talk a little bit about the relationship of the orthopedic ostrich.
DEEPA BOSE: So it's difficult to diagnose because of several reasons. So first of all, if you look at the clinical photograph on the left, I think it's fairly obvious that anyone would say that that's infected. There's a sinus that's discharging pus. The surrounding skin is macerated and erythematous, and there is underlying fracture and fixation. So not difficult in that case to say that this is infected.
DEEPA BOSE: But if you look at the clinical photograph on the right hand side of the screen, you can see that there's a surgical wound, there eclipsed in situ. It's a little bit red. There's a little bit of a discharge and you're wondering, you know, is this infected or is it just post-surgical changes. So clinically can often be difficult to spot especially in the early stages.
DEEPA BOSE: So my rule of thumb is that if you have an underlying metal work, then you can't assume that an infection is superficial. So there's no such thing as a superficial infection if you have underlying metal work because if you've got a wound infection, you have to imagine that hat leads straight down to whatever fixation you have underneath. So the orthopedic ostrich approach is, if I were to say oh well, that's just a superficial wound infection.
DEEPA BOSE: But in fact, if you think about it, how could it not be connected to the underlying metalwork? So if you can't rely on the clinical picture, then what about tests? Well, white cell count, neutrophil count, ESR and CRP, things that we rely on to give us a steer when it comes to other infections, like, for example, a soft tissue abscess. They all may be normal in implant related infection or they may be elevated for other reasons.
DEEPA BOSE: So it's not always easy to tell if you go by lab tests whether there's an infection or not. So if you can't rely on lab tests, then you have to say that a negative tests don't equate to an absence of infection. So the orthopedic ostrich approach would be if I were to say, well, the white cells are normal. The CRP is normal, so it's not infected. But that isn't the case.
DEEPA BOSE: So if we can't rely on lab tests and clinical picture, then we move to imaging. And I just want to run through some terminology here to do with imaging, because people do sometimes find it a bit confusing. So if you look at the X-ray on the left hand side, you can see certain pieces that I've labeled. So the old cortex, which has died is the sequestrum. And you can see that it's been sequestered.
DEEPA BOSE: That's why it's called the sequestrum, because it's been isolated and sequestered within the new cortex, which is called the involucrum. Now, the involucrum often has an opening in it, which we call the cloaca, and the hole in the skin, which we call the sinus, normally leads down to the cloaca, either by a straight or by a tortuous route. So it's easy to get confused between those two
DEEPA BOSE: but the hole in the skin is the sinus, the one that's discharging, but it's usually connected to the hole in the bone, which is called the cloaca. So that's just a little bit about terminology when we're talking about bone infection. So if we look at how we can diagnose bone infection, we have various modalities of imaging apart from plain films.
DEEPA BOSE: So you have anatomical imaging, which is your CT scans or MRIs scans, which show you the anatomy. You have functional imaging such as isotope bone scans and white cell labeled scans, which will show you the physiology. It will show you what is happening to the area, whether the scan is being taken up by white cells et cetera so that it shows you more about the function.
DEEPA BOSE: And then there are combination scans that show you both. So you can have a white cell labeled SPECT scan, which will not only show you the anatomy, but it will show you what's happening at the cellular level. And then you have a FDG labeled PET scans, which do the same thing. So it's a combination of an anatomical and a functional scan. But the problem with those is none of them are entirely conclusive because you can get high signal in any area where white cells accumulate.
DEEPA BOSE: So, for example, if something is inflamed, how can you tell the difference between inflammation and infection. And experienced radiologists probably can do that too, with a certain degree of reliability, but it's by no means a conclusive piece of evidence. So you can't always rely on imaging. So if you can't rely on imaging, well, where do we go next? What about microbiology?
DEEPA BOSE: Now I say this and my colleagues may or may not back me up, but I say this with absolute certainty. Surface swabs are not useful. They're not useful because if you swap a sinus, then more than likely you will pick up a skin contaminant and that's not necessarily related to the organism that's causing the infection. So surface swabs are not useful and I don't do them at all. What is better is multiple samples taken at the time of surgery with clean instruments.
DEEPA BOSE: So we use clean instruments to take each sample and it's best to take the samples around the implant or the fracture or a clean image guided biopsy, and then the samples have to be plated up as soon as possible to avoid the risk of cross-contamination. So what you want to do is to minimize the number of times that the tissue has to go through a change in location and the way you do that is by putting it straight into your culture bottles and then having those taken straight to the lab where they're plated up immediately so you reduce the risk of cross-contamination.
DEEPA BOSE: In addition to that, it's a little bit more complex because if you take your samples from, let's say, a necrotic area, then you won't necessarily grow anything because dead organisms don't form a culture. You can also get fastidious non culture forming organisms, although that's rare in bone infection, but you can still get them and the organism grown may not be the causative organism
DEEPA BOSE: as I've said, if there is a risk of cross-contamination, which is why when you take your samples, you have to use clean instruments and you have to be very careful not to touch the skin on the way in or the way out to reduce that risk of cross-contamination with skin commensals. There are culture independent methods like a PCR, which you can use, but they don't necessarily give you the correct antibiotic sensitivities
DEEPA BOSE: so you have to be a little bit careful with that. So culture negative, if you fail to grow something, it doesn't mean there's no infection. It just means that you haven't identified the organism and in my practice, in fracture related infection, I would say about 15% to 20% of our infections are culture negative. So that's infections that we are clinically sure they're infected, but they are culture negative.
DEEPA BOSE: So the orthopedic ostrich approach would be if I were to say, well, we haven't grown anything, so it's not infected and that's not the case. Now the international group consensus group for FRI have come up with certain complementary criteria for bone infection, and those are. So fistula, sinus or wound breakdown that is in direct communication with the bone or the implant.
DEEPA BOSE: So if you have a discharging sinus, for example. Purulent drainage from the wound or the presence of pus during surgery. Phenotypically indistinguishable pathogens from at least two separate tissue cultures. So these are deep tissue samples that are taken in the manner I've described, using clean instruments for each, being careful not to touch the skin on the way in or the way out
DEEPA BOSE: and that's another confirmatory criteria so phenotypically indistinguishable pathogens from two or more samples. And then the presence of micro-organisms in deep tissue as confirmed by histological examination or more than five polymorphonuclear cells per high power field. So when we take samples, we take samples not only for microbiology but also for histology, and we specifically write on the histology request form.
DEEPA BOSE: Please comment on the presence of polymorphs because that's what we want to know. So having said all of those things, we realize that the diagnosis of fracture related infection is not easy because there isn't one conclusive criteria apart from the confirmatory signs. I'll just go back. I'll just. Sorry, I seem to be moving ahead.
DEEPA BOSE: I'll just pop back to that. So apart from these confirmatory criteria for bone infection, there isn't one particular sign and in a lot of cases you aren't going to get these signs and you're left wondering how you can tell whether something's infected or not because your evidence has to be cumulative. So I'll just explain to you what I do. So the clinical picture is really quite important. So if you see redness around the wound or you've got a history of discharge or a leaking sinus, even if the wound is currently dry, you have to assume that that's infected unless proven otherwise.
DEEPA BOSE: There are softer signs such as redness and inflammation with underlying metalwork but as I've explained to you, I don't believe that there is any such thing as a superficial infection if you have underlying metalwork. You have to assume that it communicates with the metalwork or with the fracture. The only caveat to that is that you can get wound breakdown because of ischemia or poor skin,
DEEPA BOSE: but essentially, if you have underlying metalwork, that is an academic distinction because as soon as the wound breaks down, the metalwork or the fracture is exposed to the outside world and I have heard people saying things like oh well, it's covered with healthy muscle, so there's no risk of infection. I'm afraid that just isn't true. The skin is the only impermeable barrier,
DEEPA BOSE: muscle is not impermeable. So as long as you've got a communication between the outside world and whatever's going on inside, then you have to assume that that's infected. So what about tests? We've said that you can't always rely on lab tests, especially in the immediate post-operative phase because they can be elevated.
DEEPA BOSE: So I have to say, for chronic infections, I don't routinely check bloods. What about imaging? So my, this is how our practice has evolved in Birmingham. So we always get plain x-rays as a baseline because it can give you a lot of information. So it can show you the fracture configuration. It can show you how much healing there is, the position of the implant, whether it's loose or not
DEEPA BOSE: and then for advanced imaging, what do we do is if there's no metalwork. So if let's say you have chronic osteomyelitis with the metalwork has previously been removed, then we will get an MRI and that's our workhorse, really. If we have metalwork in situ, then the MRI is less useful because of the scatter and so then we get a white cell labeled SPECT because SPECT on its own, from what I understand from our radiologists, is not so useful
DEEPA BOSE: so you need a white cell labeled SPECT. If we want to look at the extent of the disease, not just to confirm the infection. So let's say we've got a patient with a discharging sinus, we know that that's infected so I don't need an MRI to confirm the diagnosis, but I need an MRI to show me the extent of the disease and to provide me with a surgical map.
DEEPA BOSE: The other thing that we would get if we want to look at fracture healing so let's say we're considering removing an implant, then you want to know whether the fracture is healed and if that isn't obvious on the plain films, then I would get a CT scan because that then will allow me to understand whether I need to provide additional stability after my debridement or not.
DEEPA BOSE: So this is our sort of algorithm for how we use imaging. What about microbiology? Well, the yield from culture is only ever as good as two things; how you take the sample and how you process it. And as I've said, we need to try and reduce the number of steps between taking the sample and plating it up in the lab to reduce the risk of cross-contamination.
DEEPA BOSE: You can use PCR. The evidence for PCR is stronger in prosthetic joint infection compared to FRI. The other thing you can do is sonication and again, the evidence for this is a bit stronger in PJI where you take the implant, you immerse it in a sonication bath and then once you've applied the ultrasound, you take the fluid and culture that. In a lot of FRI, that may not apply if we've retained the implant
DEEPA BOSE: so if we've done a DAIR where we've done debridement and implant retention, then you haven't got anything to put into the sonification bath. And there is evidence to show that it's inferior to tissue samples. So what we do is we take, as I've described, clean tissue samples from around the implant or the fracture, making sure that you're not touching the skin on the way in or the way out.
DEEPA BOSE: They go straight into the culture bottles and then we ring the lab and we get a porter to take them down so they're plated up immediately because if you take a sample, let's say on a Friday afternoon, you may find it doesn't get to the lab until Friday evening and then it will sit around in a box until Monday morning when it gets plated up, by which time it is a desiccated shred of tissue and you'll never grow anything from it.
DEEPA BOSE: So you have to be proactive in getting it down to the lab and plated up as soon as possible. And as I've said, we don't send swabs and definitely don't send the sinus because that will just give you skin organisms. So those are my tips and tricks for diagnosing. If you want to read a bit more about it, do read about the work of the International Consensus Group on FRI and again, if you've got any questions, I'm more than happy to take them.
DEEPA BOSE: Thank you.
BILAL JAMAL: Thanks, Deepa. That was phenomenal. I wanted to ask something around what I find to be a relatively a common scenario whereby a patient presents and they've had, say, internal fixation of a pilon fracture, for example, and you're seeing evidence of early metalwork, fatigue and the bone morphologically looks abnormal on radiographs and perhaps on CT as well
BILAL JAMAL: if you've had a chance to get that and radiologically, the concerns are around infection. There may or may not have been a concern around early wound discharge, which never really amounted to anything. And in that circumstance, to my mind, it's difficult to know how to proceed because surgical intervention in that case, to my mind, would involve resection of infected bone and if there's a significant area of morphological change that could be segmental excision of bone, which clearly has a morbidity in terms of the treatment provided, but missing that and treating them in a lesser fashion may bring its own problems.
BILAL JAMAL: [Yeah.]. And I find that a difficult, a difficult decision to make as to when to go big and when to be conservative, and also to convey all of that to a patient who is often absolutely terrified, and so how do you approach that situation?
DEEPA BOSE: It's very challenging, Bilal, as you said. You know, these because these situations are so nuanced, it is very difficult to explain that to the patient because as you said, on the one hand, if you risk missing an infection, you could end up in a situation later on where you're having to do a much bigger resection, a much more complex reconstruction.
DEEPA BOSE: But if you, you know, if you jump in, then you may end up doing a bigger resection than you need so it is very challenging. I mean, so if, again, I would go back to your patient factors and your injury factors, and if you, you know, if you've got a diabetic patient with neuropathy and you've got loosening implants, then you kind of know where you are, don't you
DEEPA BOSE: and you know that that's a situation where you are more than likely going to have to go back in if the implants are failing. But if you've got implants that are sound, then that's a much more nuanced and tricky situation. My default is actually, if I'm concerned, to wash it out and get samples because that gives me something at least. Yeah but then you can get patients who aren't very fit and you don't necessarily want to give them another anesthetic.
DEEPA BOSE: You know, if your suspicion is low. So I haven't got a straight answer for you, I'm afraid. I think it's a very challenging situation and very difficult to explain to the patients as well. And I think, you know, as I go along in my career, I think that's literally when it comes to dealing with infection and limb reconstruction, the most challenging thing is how you have those conversations with the patient and, and what you explain to them and how you explain it to them.
DEEPA BOSE: Yeah, sorry, I haven't answered.
BILAL JAMAL: You know, I think you have in the sense that misery loves company and those are my challenges hugely, and it's nice to hear that even you face the same problems as it were, around reaching that diagnosis and the implications for treatment. And I think that's the strength of the MDT, really. It's when you want to have your colleagues around you so that you're, you know, whatever you do is based on robust discussion and documentation.
BILAL JAMAL: Absolutely. Thanks, Deepa.
Segment:0 .
IAN KENNEDY: we are into the second session in the BAJIS webinar series. I'm Ian Kennedy. I'm the BAJIS educational lead, and I would encourage you all to join the society. It's currently free of charge. It'll keep you updated and all our other upcoming educational events. If you've got any questions for the speakers, please type these into either the Q&A box or the chat box at the bottom of your screen and I will go through these at the end of the talk.
IAN KENNEDY: So our session today is going to focus on fracture related infection, and joining me as co-host, someone with a vast amount of experience in this area, it's current BAJIS President Elect, Mr. Bilal. Jamal, so over to you, Bilal.
BILAL JAMAL: Thanks, Ian.
BILAL JAMAL: Good evening and thank you to everyone for joining in today and hopefully some people can join us via recording after the fact.
BILAL JAMAL: It's always fun to do these things because you get to pick your friends and ask them to speak, and I always find that I learn a huge amount from that. Deepa is going to be speaking, first of all, and I'd like to take a minute just to introduce her. So Deepa is a consultant in Birmingham at the Queen Elizabeth Hospital. She's trained in Wales initially and then has had fellowship at the Nuffield Orthopedic Centre, which is the only dedicated infection unit in the United Kingdom in the form of the Oxford Bone Infection Center that has gone on to form a large part of our practice going forward.
BILAL JAMAL: But in addition to that, Deepa also has a significant interest in education, and in advancing orthopedics more globally. She's been past chairman of World Orthopedic Concern and in addition to that is currently the chairperson of the Specialist Advisory Committee. So there's a huge amount of wealth of knowledge there available from Deepa and I'm hugely grateful to her for agreeing to speak on fracture related infection and principles of diagnosis.
BILAL JAMAL: So over to you, Deepa.
DEEPA BOSE: Thanks very much, Bilal. It's a very, very kind introduction. Thank you and thank you for inviting me to speak. So I'm just going to see if I can share my slides with you. OK. And hopefully that's gone on to a slideshow that someone could just give me.
DEEPA BOSE: Yeah is that OK? OK lovely. Thank you. So, yes, thank you very much for inviting me to speak. And the focus of my talk will be diagnosing fracture related infection. So the incidence of infection after trauma varies quite widely in the literature from 6 to 15%, depending on which papers you read,
DEEPA BOSE: but there are certain conditions that it seems to be associated with, such as the injury site and complexity. So the more complex the injury, the higher the risk of getting an infection. This particularly applies to things like open fractures. Then it is also related to the patient's comorbidities, the number of operations et cetera. So it's related to patient factors and injury factors really.
DEEPA BOSE: And we all know that it is common after open fractures. So why is bone infection in general a problem and I'd like to introduce you to this concept of the orthopedic ostrich if you haven't heard me speak of it before. So bone infection is a problem because it's difficult to diagnose and it's difficult to treat and so we're going to talk a little bit about the relationship of the orthopedic ostrich.
DEEPA BOSE: So it's difficult to diagnose because of several reasons. So first of all, if you look at the clinical photograph on the left, I think it's fairly obvious that anyone would say that that's infected. There's a sinus that's discharging pus. The surrounding skin is macerated and erythematous, and there is underlying fracture and fixation. So not difficult in that case to say that this is infected.
DEEPA BOSE: But if you look at the clinical photograph on the right hand side of the screen, you can see that there's a surgical wound, there eclipsed in situ. It's a little bit red. There's a little bit of a discharge and you're wondering, you know, is this infected or is it just post-surgical changes. So clinically can often be difficult to spot especially in the early stages.
DEEPA BOSE: So my rule of thumb is that if you have an underlying metal work, then you can't assume that an infection is superficial. So there's no such thing as a superficial infection if you have underlying metal work because if you've got a wound infection, you have to imagine that hat leads straight down to whatever fixation you have underneath. So the orthopedic ostrich approach is, if I were to say oh well, that's just a superficial wound infection.
DEEPA BOSE: But in fact, if you think about it, how could it not be connected to the underlying metalwork? So if you can't rely on the clinical picture, then what about tests? Well, white cell count, neutrophil count, ESR and CRP, things that we rely on to give us a steer when it comes to other infections, like, for example, a soft tissue abscess. They all may be normal in implant related infection or they may be elevated for other reasons.
DEEPA BOSE: So it's not always easy to tell if you go by lab tests whether there's an infection or not. So if you can't rely on lab tests, then you have to say that a negative tests don't equate to an absence of infection. So the orthopedic ostrich approach would be if I were to say, well, the white cells are normal. The CRP is normal, so it's not infected. But that isn't the case.
DEEPA BOSE: So if we can't rely on lab tests and clinical picture, then we move to imaging. And I just want to run through some terminology here to do with imaging, because people do sometimes find it a bit confusing. So if you look at the X-ray on the left hand side, you can see certain pieces that I've labeled. So the old cortex, which has died is the sequestrum. And you can see that it's been sequestered.
DEEPA BOSE: That's why it's called the sequestrum, because it's been isolated and sequestered within the new cortex, which is called the involucrum. Now, the involucrum often has an opening in it, which we call the cloaca, and the hole in the skin, which we call the sinus, normally leads down to the cloaca, either by a straight or by a tortuous route. So it's easy to get confused between those two
DEEPA BOSE: but the hole in the skin is the sinus, the one that's discharging, but it's usually connected to the hole in the bone, which is called the cloaca. So that's just a little bit about terminology when we're talking about bone infection. So if we look at how we can diagnose bone infection, we have various modalities of imaging apart from plain films.
DEEPA BOSE: So you have anatomical imaging, which is your CT scans or MRIs scans, which show you the anatomy. You have functional imaging such as isotope bone scans and white cell labeled scans, which will show you the physiology. It will show you what is happening to the area, whether the scan is being taken up by white cells et cetera so that it shows you more about the function.
DEEPA BOSE: And then there are combination scans that show you both. So you can have a white cell labeled SPECT scan, which will not only show you the anatomy, but it will show you what's happening at the cellular level. And then you have a FDG labeled PET scans, which do the same thing. So it's a combination of an anatomical and a functional scan. But the problem with those is none of them are entirely conclusive because you can get high signal in any area where white cells accumulate.
DEEPA BOSE: So, for example, if something is inflamed, how can you tell the difference between inflammation and infection. And experienced radiologists probably can do that too, with a certain degree of reliability, but it's by no means a conclusive piece of evidence. So you can't always rely on imaging. So if you can't rely on imaging, well, where do we go next? What about microbiology?
DEEPA BOSE: Now I say this and my colleagues may or may not back me up, but I say this with absolute certainty. Surface swabs are not useful. They're not useful because if you swap a sinus, then more than likely you will pick up a skin contaminant and that's not necessarily related to the organism that's causing the infection. So surface swabs are not useful and I don't do them at all. What is better is multiple samples taken at the time of surgery with clean instruments.
DEEPA BOSE: So we use clean instruments to take each sample and it's best to take the samples around the implant or the fracture or a clean image guided biopsy, and then the samples have to be plated up as soon as possible to avoid the risk of cross-contamination. So what you want to do is to minimize the number of times that the tissue has to go through a change in location and the way you do that is by putting it straight into your culture bottles and then having those taken straight to the lab where they're plated up immediately so you reduce the risk of cross-contamination.
DEEPA BOSE: In addition to that, it's a little bit more complex because if you take your samples from, let's say, a necrotic area, then you won't necessarily grow anything because dead organisms don't form a culture. You can also get fastidious non culture forming organisms, although that's rare in bone infection, but you can still get them and the organism grown may not be the causative organism
DEEPA BOSE: as I've said, if there is a risk of cross-contamination, which is why when you take your samples, you have to use clean instruments and you have to be very careful not to touch the skin on the way in or the way out to reduce that risk of cross-contamination with skin commensals. There are culture independent methods like a PCR, which you can use, but they don't necessarily give you the correct antibiotic sensitivities
DEEPA BOSE: so you have to be a little bit careful with that. So culture negative, if you fail to grow something, it doesn't mean there's no infection. It just means that you haven't identified the organism and in my practice, in fracture related infection, I would say about 15% to 20% of our infections are culture negative. So that's infections that we are clinically sure they're infected, but they are culture negative.
DEEPA BOSE: So the orthopedic ostrich approach would be if I were to say, well, we haven't grown anything, so it's not infected and that's not the case. Now the international group consensus group for FRI have come up with certain complementary criteria for bone infection, and those are. So fistula, sinus or wound breakdown that is in direct communication with the bone or the implant.
DEEPA BOSE: So if you have a discharging sinus, for example. Purulent drainage from the wound or the presence of pus during surgery. Phenotypically indistinguishable pathogens from at least two separate tissue cultures. So these are deep tissue samples that are taken in the manner I've described, using clean instruments for each, being careful not to touch the skin on the way in or the way out
DEEPA BOSE: and that's another confirmatory criteria so phenotypically indistinguishable pathogens from two or more samples. And then the presence of micro-organisms in deep tissue as confirmed by histological examination or more than five polymorphonuclear cells per high power field. So when we take samples, we take samples not only for microbiology but also for histology, and we specifically write on the histology request form.
DEEPA BOSE: Please comment on the presence of polymorphs because that's what we want to know. So having said all of those things, we realize that the diagnosis of fracture related infection is not easy because there isn't one conclusive criteria apart from the confirmatory signs. I'll just go back. I'll just. Sorry, I seem to be moving ahead.
DEEPA BOSE: I'll just pop back to that. So apart from these confirmatory criteria for bone infection, there isn't one particular sign and in a lot of cases you aren't going to get these signs and you're left wondering how you can tell whether something's infected or not because your evidence has to be cumulative. So I'll just explain to you what I do. So the clinical picture is really quite important. So if you see redness around the wound or you've got a history of discharge or a leaking sinus, even if the wound is currently dry, you have to assume that that's infected unless proven otherwise.
DEEPA BOSE: There are softer signs such as redness and inflammation with underlying metalwork but as I've explained to you, I don't believe that there is any such thing as a superficial infection if you have underlying metalwork. You have to assume that it communicates with the metalwork or with the fracture. The only caveat to that is that you can get wound breakdown because of ischemia or poor skin,
DEEPA BOSE: but essentially, if you have underlying metalwork, that is an academic distinction because as soon as the wound breaks down, the metalwork or the fracture is exposed to the outside world and I have heard people saying things like oh well, it's covered with healthy muscle, so there's no risk of infection. I'm afraid that just isn't true. The skin is the only impermeable barrier,
DEEPA BOSE: muscle is not impermeable. So as long as you've got a communication between the outside world and whatever's going on inside, then you have to assume that that's infected. So what about tests? We've said that you can't always rely on lab tests, especially in the immediate post-operative phase because they can be elevated.
DEEPA BOSE: So I have to say, for chronic infections, I don't routinely check bloods. What about imaging? So my, this is how our practice has evolved in Birmingham. So we always get plain x-rays as a baseline because it can give you a lot of information. So it can show you the fracture configuration. It can show you how much healing there is, the position of the implant, whether it's loose or not
DEEPA BOSE: and then for advanced imaging, what do we do is if there's no metalwork. So if let's say you have chronic osteomyelitis with the metalwork has previously been removed, then we will get an MRI and that's our workhorse, really. If we have metalwork in situ, then the MRI is less useful because of the scatter and so then we get a white cell labeled SPECT because SPECT on its own, from what I understand from our radiologists, is not so useful
DEEPA BOSE: so you need a white cell labeled SPECT. If we want to look at the extent of the disease, not just to confirm the infection. So let's say we've got a patient with a discharging sinus, we know that that's infected so I don't need an MRI to confirm the diagnosis, but I need an MRI to show me the extent of the disease and to provide me with a surgical map.
DEEPA BOSE: The other thing that we would get if we want to look at fracture healing so let's say we're considering removing an implant, then you want to know whether the fracture is healed and if that isn't obvious on the plain films, then I would get a CT scan because that then will allow me to understand whether I need to provide additional stability after my debridement or not.
DEEPA BOSE: So this is our sort of algorithm for how we use imaging. What about microbiology? Well, the yield from culture is only ever as good as two things; how you take the sample and how you process it. And as I've said, we need to try and reduce the number of steps between taking the sample and plating it up in the lab to reduce the risk of cross-contamination.
DEEPA BOSE: You can use PCR. The evidence for PCR is stronger in prosthetic joint infection compared to FRI. The other thing you can do is sonication and again, the evidence for this is a bit stronger in PJI where you take the implant, you immerse it in a sonication bath and then once you've applied the ultrasound, you take the fluid and culture that. In a lot of FRI, that may not apply if we've retained the implant
DEEPA BOSE: so if we've done a DAIR where we've done debridement and implant retention, then you haven't got anything to put into the sonification bath. And there is evidence to show that it's inferior to tissue samples. So what we do is we take, as I've described, clean tissue samples from around the implant or the fracture, making sure that you're not touching the skin on the way in or the way out.
DEEPA BOSE: They go straight into the culture bottles and then we ring the lab and we get a porter to take them down so they're plated up immediately because if you take a sample, let's say on a Friday afternoon, you may find it doesn't get to the lab until Friday evening and then it will sit around in a box until Monday morning when it gets plated up, by which time it is a desiccated shred of tissue and you'll never grow anything from it.
DEEPA BOSE: So you have to be proactive in getting it down to the lab and plated up as soon as possible. And as I've said, we don't send swabs and definitely don't send the sinus because that will just give you skin organisms. So those are my tips and tricks for diagnosing. If you want to read a bit more about it, do read about the work of the International Consensus Group on FRI and again, if you've got any questions, I'm more than happy to take them.
DEEPA BOSE: Thank you.
BILAL JAMAL: Thanks, Deepa. That was phenomenal. I wanted to ask something around what I find to be a relatively a common scenario whereby a patient presents and they've had, say, internal fixation of a pilon fracture, for example, and you're seeing evidence of early metalwork, fatigue and the bone morphologically looks abnormal on radiographs and perhaps on CT as well
BILAL JAMAL: if you've had a chance to get that and radiologically, the concerns are around infection. There may or may not have been a concern around early wound discharge, which never really amounted to anything. And in that circumstance, to my mind, it's difficult to know how to proceed because surgical intervention in that case, to my mind, would involve resection of infected bone and if there's a significant area of morphological change that could be segmental excision of bone, which clearly has a morbidity in terms of the treatment provided, but missing that and treating them in a lesser fashion may bring its own problems.
BILAL JAMAL: [Yeah.]. And I find that a difficult, a difficult decision to make as to when to go big and when to be conservative, and also to convey all of that to a patient who is often absolutely terrified, and so how do you approach that situation?
DEEPA BOSE: It's very challenging, Bilal, as you said. You know, these because these situations are so nuanced, it is very difficult to explain that to the patient because as you said, on the one hand, if you risk missing an infection, you could end up in a situation later on where you're having to do a much bigger resection, a much more complex reconstruction.
DEEPA BOSE: But if you, you know, if you jump in, then you may end up doing a bigger resection than you need so it is very challenging. I mean, so if, again, I would go back to your patient factors and your injury factors, and if you, you know, if you've got a diabetic patient with neuropathy and you've got loosening implants, then you kind of know where you are, don't you
DEEPA BOSE: and you know that that's a situation where you are more than likely going to have to go back in if the implants are failing. But if you've got implants that are sound, then that's a much more nuanced and tricky situation. My default is actually, if I'm concerned, to wash it out and get samples because that gives me something at least. Yeah but then you can get patients who aren't very fit and you don't necessarily want to give them another anesthetic.
DEEPA BOSE: You know, if your suspicion is low. So I haven't got a straight answer for you, I'm afraid. I think it's a very challenging situation and very difficult to explain to the patients as well. And I think, you know, as I go along in my career, I think that's literally when it comes to dealing with infection and limb reconstruction, the most challenging thing is how you have those conversations with the patient and, and what you explain to them and how you explain it to them.
DEEPA BOSE: Yeah, sorry, I haven't answered.
BILAL JAMAL: You know, I think you have in the sense that misery loves company and those are my challenges hugely, and it's nice to hear that even you face the same problems as it were, around reaching that diagnosis and the implications for treatment. And I think that's the strength of the MDT, really. It's when you want to have your colleagues around you so that you're, you know, whatever you do is based on robust discussion and documentation.
BILAL JAMAL: Absolutely. Thanks, Deepa.
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