Wound Ballistics Lecture Notes

Well thank you very much for the introduction, it really is a great pleasure to be here. I was, 20 years ago, I was Sir Keith Porter's House Officer in Seliac Hospital as it was then, the venerable successor to the accident hospital in Birmingham and I think it's fair to say that Sir Keith set me on my path to becoming a trauma surgeon and that's currently my full-time job, employed by the Royal Navy but working most of my time within the NHS. So before I get on to the normal disclaimers, I'd just like to give a quick overview of what we'll be covering tonight. So first of all, we'll start off with explaining the slightly weird title of my talk, and then we're going to cover wound ballistics. So look at some of the science behind the physics of the interaction between projectiles and the human body. We're then going to look at how tissue behaves when it's struck by bullets. And then we're going to look at some of the treatment algorithms. And I apologize, it gets a little bit... a little bit surgical a bit orthopedic but that's what you'd expect from me I guess. Finally we're going to allow a bit of time for discussion and I'll talk about ways that you can find out more and I'm going to be a little bit self-indulgent and talk about some of the research that myself and some colleagues are doing down at Porton Down. So let's get on with the usual disclaimers. So as I said before I'm a regular commissioned officer in the Royal Navy but In between deployments I'm working at Oxford in the major trauma centre there and I'm actually just taken over as the clinical lead of the Oxford trauma service which is interesting to get to see all the datex forms about my colleagues which I enjoy. I'm also the consultant advisor in trauma and orthopaedics to help to advise commanders to any issues that pertain to trauma and also help to supervise and assist the next generation of surgeons which is probably the most interesting part of my additional roles. Obviously got to emphasize anyone who knows me will realize that this really is quite an important part of the talk definitely my own views I don't represent or speak for the Royal Navy Her Majesty's Government or the Oxford University Hospitals Trust and in terms of conflict of interest I think it's a good time to say that I have one and I would like you all to buy my book. If you're interested in ballistic trauma it's a great way to sort of learn a little bit more and if you're just financially savvy if you note that the used price is currently about a third greater than the new price this book represents an excellent return on your investment as well so I urge you to do that do that as soon as we finish this talk. So why the title? A few people have got in touch with me and asked about my interest in Welsh hip-hop. People might not realise this, but this was a title that I've plagiarised from an early noughties Newport hip-hop band. One of their tracks was Guns Don't Kill People, Rappers Do. The reason I've chosen this talk is because I think when medics start talking about ballistics, we focus immediately on the wrong thing. There's far too much discussion about the firearms, the small arms that are involved. You hear things on the news about people being shot with a high velocity rifle and I think the focus is very wrong. Guns obviously are important but it's the bullets and the bullet design and how bullets interact with the body which is far more important to us as clinicians. The other reason I've chosen this title is because all the good ones were already chosen by the people in the past. So I pulled out three fairly significant reviews from the literature. And if you look there's a common theme amongst the titles so lies, damn lies or ballistics, my personal favourite, wound ballistics a review of common misconceptions and applied wound ballistics what's new and what's true. The implication of the last title being there's an awful lot out there that's false and this is certainly my experience so as somebody who's spent a lot of time researching in this area you find a lot of stuff that's misleading and confused And I think this is because of the influence of politics and money. So as an example, in the 70s, there were a lot of research papers coming out of Sweden that were talking about the brutal and inhumane wounding patterns from M16 rounds. And this was to do with their government's opposition to the... Vietnam War and the US military's new adoption of an M16 firing 5.56 rounds. In actual fact, the wounds produced by a 5.56 NATO bullet, the SS-109, are just broadly similar to military rifle rounds that have been used for some time and in fact, if anything, they're a fair bit lighter. The other influence is money and particularly this is true in America. So the distortion of the gun lobby and non-scientists who are influential in that field have unfortunately sort of distorted the way we talk about it and the way we study it. So as a consequence there is a lot of misconception out there so hopefully at the end of this talk we'll have got to a bit better place. Having stressed the importance of bullets over firearms I think it's worth quickly just looking at some of the um some of the features of a firearm. So this is a rifle, so it's a long barreled weapon. And just so we understand some of the basics of what's going on, the bullet ends up being fed up through a magazine here, ends up in a breech which is just here, which is sealed by the bolt where that slides forward. That then creates essentially a tube with only one opening at the business end. The bullet when you pull the trigger is ignited or the propellant behind the bullet is ignited and the bullet is then forced down as the propellant gas expands. The bullet's enforced down the barrel, it accelerates and when it leaves the end of the barrel here that's the muzzle velocity or the velocity it has is the muzzle velocity which is the fastest speed that it's going to be traveling at through the entire course of its path. The inside of the barrel has a spiral groove. and that confers a spin to the bullet which um confers stability and that's um that's the only time we'll be talking about um uh about firearms really in this in this talk so why is it relevant well they're common there's an estimation of about a billion serviceable firearms around the um around the world and the thing that would surprise us for those of us dialing in from the uk um we live in a country where the state has a near total monopoly on firearm usage. Obviously, it licenses under strict conditions and private owners to own firearms, like the one I just showed you. But we would assume that the majority of firearms around the world are held by police and militaries. In actual fact, that's not true. Globally, only about 15% of them are. So there is a lot of sort of fairly loosely controlled firearms around the world. and the United Kingdom is not really representative of the worldwide situation. I don't think anyone would be shocked to learn that in terms of private ownership, the United States is way, way ahead of most other countries. But you can see going down the list, actually, there's a lot of countries where private firearm ownership is entirely normal, and it's not a weird thing at all. And unfortunately, this is the truth of why this is relevant to all of us. So outside of the low-level criminality that's occurring in a lot of, increasingly a lot of urban centres in the UK, what we are preparing as clinicians at work across the country is to respond and to be resilient against the rewarding terrorist firearms attacks. Fortunately, still quite rare in the UK, but obviously Oslo, France, Mumbai, and sadly even just yesterday in Boulder in Colorado. These events happen entirely predictably and entirely regularly unfortunately and as those of us who work in the emergency trauma pre-hospital and hospital environments this is something we need to make sure our systems are able to cope with. So not just firearms casualties but potentially large simultaneously numbers of firearms casualties. Obviously I'm in the military so we'll talk a very little bit about military firearms and This often surprises people that military, in a conflict situation, firearms are actually a relatively small course of casualties. It's normally about three to one of explosive weapons to firearm weapons in terms of casualty generation. And that's remarkably consistent amongst the graph here shows the 10 years of the Iraq and Afghanistan wars, but that's remarkably consistent with Vietnam. and World War II and even World War I, where it was if anything it was skewed even greater in favour of explosive weapon causing injuries. So let's get on to some of the science. Before we get into the Newtonian physics of this, it's worth stating that wound ballistics are entirely unpredictable. If we think about the ballistics that occur inside a firearm, these are known as internal ballistics, where there is an explosion of a set amount of propellants. That propellant confers a certain amount of energy into a bullet and the bullet travels down the gun. When it leaves the gun, it becomes the study of external ballistics. And that, again, is incredibly reproducible. If you think about the accuracy of modern firearms. with sub 1 MOA accuracy that will allow a sniper or marksman to reproducibly hit a very small target at ranges 800 meters plus. These are very precise machines, very precise tools and the ballistics, the science behind it is very predictable. As soon as that bullet contacts tissue, everything gets a little bit weird. So the first thing I'd like to say is although I'm going to be offering some rules of thumb in this talk Wound ballistics are incredibly unpredictable. One of the difficulties that I'll talk about at the end is actually they're so unpredictable that trying to make a reproducible standardized model even under laboratory conditions is extremely difficult and that's basically why I've lost all my hair. So the first rule I'd use is that you've got to think about this in terms of energy. So remembering going back to our sort of school physics kinetic energy in the context of ballistics is the ability to damage tissue that's what you've got to think about kinetic energy is a potential to damage tissue the key concept to understand here is the rate that that kinetic energy is transferred into the tissue is related to drag and it's the this rapidity that our tissue slow down projectiles slow down bullets relates very closely to the severity of the wounds that are produced so a quick uh A quick rehearsal. Kinetic energy is proportional, or sorry, in this sense, equal to mass times the square of velocity halved. So the key take-home to that is velocity is far more significant than mass in terms of the amount of energy that a bullet possesses, and we'll talk a little bit about that later on. So if you've got kinetic energy, that's a big bold KE, before you... is possessed by a bullet before it strikes a limb and this is probably now a good point to give a trigger warning this is the first of a series of x-rays and clinical photographs that are all used with the permission of the patient but certainly are graphic and if this isn't your cup of tea first of all you're probably in the wrong webinar and secondly I apologize if that did cause any distress but the kinetic energy on the left of the screen is what's possessed by the projectile before it strikes a limb it strikes a limb and then it carries on through. You can see from the x-rays that there's no retained bullet or fragments and that's because the bullets transited all the way through the limb. So it still has kinetic energy, it's still moving as it hits the other side. The delta or the difference between the two kinetic energies is what's been transferred into the tissue and that's what creates this tissue damage that we're going to see. So that is conceptually, broadly how kinetic energy relates to wounding but... it gets a lot more complicated than that because it's all about drag it's all about the rapidity that the um the the bullet is slowed down and the amount of energy it it deposits into the wound so there is um a beautifully elegant equation looking at that um but the uh there's not going to be a test at the end you'll be pleased to know the key things to pull out of this equation though is the drag force and the retarding effect on the bullet is uh proportional to the both the density of the fluid in inverted commas so the fluid in this case in the arm here was the ulnar bone so the the round contact of the ulnar bone and that's an incredibly dense fluid it's not a fluid I know it's incredibly dense tissue and that had a massive retardant effect on the bullet and essentially stopped it the other thing that's proportional to is the is the surface area of the front of the bullet so I've got a you a half inch round here and it's a spitzer design so it's got a um i'll put it up so you can see the contrast it's got a a nice sharp point and it's got a little boat tail on the back so it's a very aerodynamic stable design um that will that has a lot less resistance when it's traveling in this direction and forward than if it starts tumbling and it presents its side uh side on to the direction of travel so when a bullet tumbles like this it there's a huge amount more drag and consequently there's a much quicker, it slows down much quicker if that's not an oxymoron and the amount of energy that deposits into the tissues is much greater for a given time. and that translates into a much more severe wound. So I'd like to delve into some of the history now because it's quite a useful illustration at this point and I'm also I'm a bit of a nerd as well so I do love the history of it. So back in the late 19th century the British military had just adopted a new weapon and as part of the new Lee-Metford weapon system, they probably didn't call them weapon systems back then, but as part of the new weapon system was a shift. from black powder or gunpowder, which created a lot of smoke, to smokeless powders. Now the reason to do this was to get rid of the smoke. If you had a large body of soldiers all lined up together firing their weapons, after three or four rob volleys there was so much smoke around they couldn't actually see anything to aim at and also their own position became very obvious. So it became a military requirement to switch over to smokeless powders. And that was when these nitrocellulose and cordite family of propellants came along, became available. Now not only were these burning without smoke, but they also were much, much, much more powerful. So the military transitioned from lead rounds, the advantage of which is they're very dense and so they're very heavy and they have a lot of momentum, to what they call jacketed rounds or full metal jacketed rounds. The reason they did this was when soft lead rounds were used with the new much more powerful propellant, as they were accelerated down the length of the barrel with a lot greater energy, they would shed their skins. I think of lead pencils. So the outer surface of the lead would foul the barrel and the barrels would have to be cleaned out between a few rounds. Then that was causing stoppages and it was causing potentially breach explosions as well. So to solve that problem, they jacketed the rounds with a copper material. So then you had the core was made of a heavy... dense lead so you've got the mass but then the copper coating meant that the bullets slipped down the barrel nice and quickly and you got the extra velocity as well so if you think of the kinetic energy equation you had the mass of the lead you had the velocity of the new propellant plus the copper jacketing and this is what we mean when we're talking about fully metal jacketed rounds and on the screen here we can see our original rounds but As so often with technology, there's an unforeseen consequence. And this is from a BMJ article in 1896. And I've got to be honest, if the BMJ still had a military and naval section, I might renew my subscription. But it is quite an extraordinary article because it's talking about the difficulties with the new type of bullet. And again, if BMJ articles were this interesting, they wouldn't stay in their cellophane. If we look at some of it, we're talking about that the new rounds were traversing the soft parts of the body without smashing them, even piercing through bones without splitting them. It's reported that one tribesman who'd been hit by six bullets was treated in hospital and made a good recovery. I love the way the BMJ is reporting this as an undesirable outcome. In consequence, the military authorities tended to turn their attention to the task of making a Lee-Metford bullet, which, without losing its ranging power, still inflicted a wound sufficient to... sufficiently severe to stop a rush. What they meant was a charge of people at British forces. The correspondent of the Times states that such a bullet has been devised by Captain Bertie Clay, superintendent of the Dum Dum ammunition factory. So Dum Dum is a small town in India, and there was a large British military ammunition factory there. And dum-dum is where the expression dum-dum bullets comes from, because Captain Bertie Clay had the brilliant idea that you only need the copper jacketing of the round in the part of the bullet that contacts the inside of the barrel. So that's the bit where you don't want the lead fouling the barrel. But actually, if you think about the lead at the front of the barrel, sorry, the front of the bullet, if you keep the copper jacket off that, what happens is you still get the... you still get the effect of the lead hitting the tissues and deforming. So I've got a, this is a soft nose round here and as you can see the tip of it is exposed lead and the side is copper there and when that strikes a deer for example it distorts and what we call expands and dumps its energy so instead of it having a nice a nice sharp tip like this round here it will deform and slow down very quickly as it passes through the tissues and then transfer most of the energy or transfer its energy very rapidly into the tissues and so these became known as soft nose rounds or because of the fact that they were first developed dum-dum bullets and example of a couple of couple of types here you can get a similar effect by having a hollow nose point on the tip of the bullet as well and you can see a clearer diagram there of how that peels back when it strikes tissue. And I got a clinical photograph of, this was a police nine millimetre round that struck that ulna. And police around the world, our police officers as well, the live rounds they carry are, they practice with fully metal jacketed rounds, but the rounds that they carry on operations are soft-nose deforming rounds. So if you see someone in your practice that's been shot by a police officer, First of all, it's likely that they need the other kind of specialist doctor, the one that works in the basement. But secondly, they're likely to have been injured by these particularly damaging bullets that are soft nose and transfer a lot of energy. So the wounds are expected to be more severe than perhaps you were anticipating. These expanding rounds were outlawed in the first of the Hay conventions by... by European powers together with America and the first Hague Convention. They're outlined for military use only and it's perfectly legal for hunters to use them and it's perfectly legal for police forces to use them. So let's have a look at some of the wounded interactions. With all the caveats I mentioned before of the difficulties in predicting the behavior of bullets when they contact tissue We can, with some generality, divide the components of a wound into three main types, of which two are relevant and the last one's a bit of a included for completeness, is quite controversial. So the first bit's the permanent cavity or the wound tract. So this is, conceptually, as the projectile passes through the body it crushes and lacerates and tears the tissue and essentially what it does is behaves a bit like an arrow if you like. So if you had a nine millimeter arrow passing through you, you'd expect to end up with a nine millimeter hole in your body and that's similar to the permanent cavity or the wound tract of the the bullet. It's roughly going to be the same size as the bullet and in theory if you have an entry wound and an exit wound in a limb you can look at the direct line between the two and one would anticipate, again this is not consistent, and these rounds aren't predictable, but one would expect that there'd be a line of tissue damage between those two wounds. It gets a bit more complicated when we start talking about temporary cavities and the effect that's sometimes described a little bit inaccurately as cavitation. So a temporary cavity is a bit more complicated. When there's very rapid transfer of kinetic energy into the tissues, the kinetic energy The kinetic energy causes an acceleration of tissue away from, radially away from the path of the bullet. And that interestingly causes stretch and damage to the tissues. And I'll show you some photos of that in a moment. But that also generates a sub-atmospheric pressure because the tissues are pushed away. There's essentially a vacuum in the path of the bullet and that can cause small amounts of debris. to be dragged into the wound which can increase the contamination. Cavitation is a pretty odd phenomena. Part of the large areas of misconception arise because cavitation is one of the more eye-catching and impressive phenomena associated with ballistics. So with high-speed cinematography there was an awful lot of very cool, very impressive looking slow motion footage of bullets traversing ballistic gelatin, soap blocks, that sort of thing, even underwater, and you create these very impressive looking bubble and cavity effects. And people were mentally looking at these gelatin blocks and transferring those images into a wound and imagining that's the amount of damage that was done. And so they got some significant danger of overestimating the severity of wounds if you think too much about those techniques. If you look at the depth a normal bullet has to travel before it becomes unstable and starts tumbling and starts creating a very large cavity that's normally far wider than the average person's limb. body. The final thing is shockwave. Now this is very controversial. The American firearms industry talks an awful lot about this, this idea of stopping power and this idea that you can shoot someone and although you don't hit any major organs they drop because of some kind of semi-mystical shockwave. There is a shockwave, it generates quite low energies and it can There have been a couple of animal studies that have measured an effect on the central nervous system but I think in a lot of literature it is overstated. This is a quite a nice little picture that demonstrates the, you've got a handgun being fired, you can see the shadow of the bullet, it's black and white high-speed photography, and you can look at the ripples in the polarised light demonstrating the shockwave is in front of the path of the bullet. So a shockwave is analogous to a supersonic sound wave so a sound wave traveling faster than the um speed of sound most um unless you're buying specifically buying subsonic rounds most uh most ammunition is supersonic um so my rifle's got a modifier a suppressor on it a moderator um but it still makes a loud noise because the bullet is supersonic so there's a sonic boom from the bullet um sonic booms are um are literally a shockwave being formed and so that shockwave precedes the path of the bullet and this occurs schematically in the, represented by the black lines moving in front of the bullets on the diagram on the top left of the screen. It's very low energy compared to the bullet itself. It does very little tissue damage, but as I said, in theory, the central nervous system can be affected by this, but in clinical practice, I would ignore this. Okay, so another one of my slightly late trigger warnings. The other thing to start thinking about is tissues are not homogeneous, and tissues behave differently to stretch. So tissues like skeletal muscle and lung tissue, for example, tolerate stretch very well. They're stretched all the time in their normal function. Other tissues don't tolerate stretch at all. So in the bottom left, we've got some sorry, that's skin demonstrating. You see the cracks where it's been torn, but actually overall tissue is elastic and tolerates stretch well. Lung, you've got a bone strike of a round hitting a rib and it's fragmented. But the lung tissue itself, although you can see it looks like slightly edematous, it doesn't look very happy. It's contused, but it's clearly tolerated. There hasn't been a massive tearing and disruption of the lung parenchyma. Muscle tissue as well. This is another fragmented round that went through them. This patient's right lateral thigh out of the right medial thigh and entering the left medial thigh. But again the tissue itself is looking actually pretty healthy and because it tolerates skeletal muscles looking pretty healthy because it tolerates stretch very well. I think you can see from that clinical photo things could have been a lot lot worse if they're a little bit higher. Going into this fairly gruesome picture I'm not a hepatologist but I can conclude from looking at this picture that liver tissue does not tolerate stretch very well so this is a completely destroyed liver because liver just tears. So let's look at things that can likely make, so looking in a lab-based theoretical concept first. Let's think about what things would be likely to aggravate wounds and it's all about the drag equation on the top right of the screen there. So what's likely to increase drag and increase energy transfer into the tissues? So instability. So if a round's unstable, if we look at the top left of this round here is tumbling and so as it passes sideways, as it tumbles over on itself, it presents a very large surface area and so the energy is going to be imparted at a much faster rate and that's going to cause tissue stress stretch and tissue instability and this is going to give a shout out to surgeon lieutenant commander tom stevenson who's done a lot of good work at cranfield university looking at the effect of what happens when bullets pass through clothing before they go on to strike tissue and the effect of increasing um wound severity when a bullet does pass through clothing, essentially because it causes it to destabilize and so you get a lot more of this tumbling effect and a lot more energy imparting into the tissues. and I'm pleased to say that he published that around the world, but he's also got a PhD for that, so nice one Tom. Getting into the pathophysiology now, so the biological response to this, it's worth thinking about how the tissues are going to be responding. So the first thing to say is the amount of energy or the potential kinetic energy available in gunshot wounds is enormous. So if we think of falls and falls and motor vehicle collisions as being on a spectrum. So ground level falls are on one end of that sort of low energy spectrum. As we're getting onto road traffic collisions we can get a lot higher and that sort of starts to approach in the sort of energies that are involved in gunshot wounds. So they do tend to involve greater amounts of tissue disruption and destruction than we're used to seeing in our normal conventional practice. I'm talking predominantly here about higher energy weapons that you'd see on a battlefield, so more rifle rounds, so again more sort of, there's a comparison here, so more in my right hand, I had to think about that, a rifle bullet much bigger, heavier and fired with greater velocity than a handgun bullet here, so one would expect a far greater amount of energy transfer. from rifle rounds. So what are the injuries we see? Well the primary injury is the immediate tissue destruction that happens within either instantaneously or within the first few minutes which is the shearing tearing laceration that results in tissue necrosis. There's tissue that's been traumatized often that's been stretched that will undergo a slightly more programmed apoptotic cellular death process. and that tends to occur in the first 48 hours or so and that's a bit more organised but that is also predictable and that will happen in a ballistic wound. Then we've got tertiary injury and we could talk about this as being the stuff that we as clinicians are supposed to prevent. So if we keep the patient in a shocked and hypovolemic state they're going to be hypoperfusing their damaged tissues and that can cause more destruction. If we allow them to develop a compartment syndrome and the pressure in their muscular compartments increases, that can cause, again, late tissue death. And similarly, if we allow unclean wounds to become septic, you can get unnecessary late destruction from infective causes. I think what I'm trying to say here is... Gunshot wounds behave differently from conventional, even conventional high energy fractures. So if I see a peel on, a nasty peel on, on day zero that it presents, we're going to take them to theatre. We're going to wash it out. We're going to put an external fixator on it and we're going to put a wound back on it. And the next day we're going to take them back to theatre and together with our... plastic surgical collies, we're going to unwrap the wound and the wound will more than likely, if we've done our jobs right, be clean and that will allow us to put the plates and screws in to fix it, move the three muscle flaps, the gracilis flaps or the ALTs to cover the wound and then we can do the definitive procedure. You cannot do that with a gunshot wound, it will still be evolving, the tissues will still be responding. You can do a very good job of wound excision. on day one, and we'll talk about that in a moment, or day zero, sorry, but the wound will continue to evolve. It's not that you haven't done a good job, it's that tissue that looked healthy and viable on day zero won't look healthy and viable on day one or two. So wounds will evolve and you've got to treat them with respect. Which brings us on to management protocols. And again, I apologise, this is a little bit more surgical orientated, a little bit more hospital-based orientated, but you shouldn't give a... you shouldn't give a presenter link to a surgeon because they're just going to hold the mic I'm afraid. So we divide this up into decision, incision, excision and I'll talk about a few pearls, a few ticks and trips at the end. So decision is assessing the amount of energy being transferred into the wound and we'll talk a bit about how you can do that with fairly basic technologies and approaches. Incision, so I separate, some people talk about debridement, I think that gets a bit ambiguous. I don't like it when people pronounce it in the French way as well, that's a bit pretentious, I'm saying that someone who works in Oxford and drinks lattes, but I think it's more useful to divide debridement into incision which essentially is extending a wound, making a surgical incision. opening skin, opening fascia, and that allows you to do two things. That decompresses a muscular compartment and allows you to explore and then proceed with the next steps of the operation. As distinct from excision, which is removable of non-viable tissue and gross contamination. So together, those essentially are the two components of debridement. But I think it's worth dividing the two up because they serve two different purposes. So let's talk about decision making. And you have another QR code here. a rather naughtily apologies injury but I made this an open access paper somewhere so if you want to download this this talks a lot about our experience from the last two conflicts of managing gunshot wounds and it did allow us to develop some rules of thumb again I'm contradicting myself I said there are no rules but there are some guidelines that you can sort of follow to assess these wounds so First of all, any high energy transfer wound or those with neurovascular injury need to be surgically explored. So if you've got an obvious, complex, large wound with a lot of obvious tissue damage, in other words, a big hole, that needs to be surgically explored. A lot of tissue has been destroyed and you need to know what's going on. You need to actually perform an excision. If there's neurovascular injury, in other words, distal to the wound, if there's a neurovascular deficit, then clearly that needs to be explored. And these are right off the bat, these guys, these injuries need to go to theatre. So having said that, if you've got a wound which doesn't involve a large amount of obvious destruction and there's neurovascular intact, you can start to think about what are possible features of high energy transfer. So the first one is fracture, and that's predictable from our sort of blackboard theoretical discussion. If a bullet strikes a bone, it's like to impart that energy quite quickly. And so it's like to be a more severe, high energy wound. Secondly, if there's been retention of the bullet or indeed fragmentation of the bullet, all of the kinetic energy held by that bullet has been dumped into the tissue if the bullet's retained whole. If a bullet's fragmented, the concern is that each of those components of the bullet, it's going to be big. the jacket, the outer lining of the bullet that is retained in the tissue. All of those individual pieces of fragments will have essentially become secondary projectiles and they will have caused their own permanent tract and permanent cavity. So one would anticipate a more complex severe amount of tissue damage deep in the wound. And that's also true of fracture actually. When a bone fractures or shatters as it often does when it's struck by a bullet, you create multiple small amounts of bone splinters. that themselves behave as secondary missiles. So again looking back to this unfortunate or fortunate, depending on your perspective, casualty you can see the large amounts of the bullet fragment. I'm very confident to know, I had a paper reviewed by someone that very snookily said that this was a blast injury, but we happen to know how this guy was injured because his mate standing next to him that accidentally shot him was charged with the negligent discharge of his 5.56 FN Minimi machine gun. So we're very confident this is a gunshot injury. But you can see on the CT scanogram on the left of the screen how the bullets fragmented and been deposited throughout his thighs and that's how we know it was a high energy transfer wound. You can see the very ragged wounds which also indicate that a lot of tissue loss. But as we said before the muscle itself has coped with that stretching pretty well. pretty healthy. So that wound is after debridement and evacuation back, that's not what a gunshot wound looks like at first presentation obviously. So again going back to this tibia X-fix that's been, sorry tibia gunshot wound and open fracture that's been stabilised in an external fixator, you can see large amounts of multi-fragmentary damage to the bone itself and this is going to be a 25 year old, almost certainly male. um quite probably Fijian uh leg this guy's cortices are going to be rock solid so the amount of energy to shatter them is enormous and that energy would have been dumped into the limb there's no sign of the bullet or fragment so we imagine there's been a near and there's been some kinetic energy retained by the by the round itself but not a lot of that has been transferred okay so the experience of the Americans with handguns and lower energy transfer wounds is that not all gunshot wounds need surgery and with low energy transfer wounds you do not need to take these all to theatre. You can treat them with antibiotics, you don't close them primarily. Always split limb, that's important to kind of allow the tissues to recover and drain freely, but not all of them need surgical treatment and that can be very important if you're in a mass casualty situation and your hospital resources are being stretched. If you triage these patients, assess their wounds properly, you can potentially avoid taking unnecessary theatre cases and using up your valuable theatre resources. So this heel wound that we saw before is a calcaneal fracture. but it's very neat. The other side looked a bit like that as well, it's impossible to say which was entry which was exit. X-rays showed a nice neat little hole through the calcaneum and there was no surgical treatment required, that's healed up nicely. So we're going to get on to a slightly controversial area as we wrap up, we get towards the end of the talk. Textbooks on the top left have all argued for quite an aggressive approach to laying open all gunshot wound tracks and this has been quite aggressively taught, certainly to me, in military surgical courses. But interestingly if we look at the most experienced group of surgeons for dealing with gunshot wounds and particularly high energy gunshot wounds they were the senior surgeons of the second world war. And the reason why they were so experienced is they spent the years of the First World War as junior surgeons learning their trade. And this was pre-antibiotic years as well. So these people were very good at treating and preventing infection with surgical treatment, with incision and excision. And one of the most experienced was Olga V, who was a fairly angry general who experienced both world wars and wars in the Balkans as well. and as you can see he was quite adamant that unnecessary operations on through and through wounds affecting the soft parts are completely unnecessary and can potentially, his concern was the surgeon can do more damage in the bullet. He emphasizes that too much skin is being removed, skin is the most, of all structures, is the most viable, the most resistant to infection and the most irreplaceable as my plastic surgical colleagues would agree. It can split it to give access but never excise except just in the edges of the wounds. Circumcision of entry and exit wounds is the hallmark of a novice. Just imagine this guy shouting at his junior surgeons. And again, point three, which is almost the same as point one, wide excision of muscle, especially transverse section of muscle groups to expose a tract. I have been told to do this, which is quite interesting. So the Second World War and First World War surgeons were very anti. So is there any science to back this up? Well these are two experimental papers, both of which came, so they're animal-based studies, but they came from two groups of surgeons that had both been in previous military conflicts on the left. We've got Martin Fackler, arguably the granddaddy of ballistics research in the modern era, and he'd been in Vietnam as a naval surgeon, transferred over to the army and started doing research for them, and he proved with modern assault rifle wounds they uh that he somehow caused to dogs and they healed up fine with that surgical treatment and ditto a um paper on sheep by a couple of british surgeons that both served in korea came to a very similar conclusion that simple straightforward uncomplex wounds did not require aggressive radical surgery so i'm going to skip ahead now and I think we're getting close to time so forgive me I'm going to leave some of the um um leave some of the more surgical uh minutiae and um I will get on to I do love an x-ray that's the same I'm gonna skip past these um I'll talk about the options for um if you were interested in learning more about this subject um if you want something that's more clinically orientated this is another um blatant plug but please feel free to um buy the book. I don't get any money from it. I think we donated all the royalties to, I think it was Blesma. But that's very clinically orientated. If you want a much more of a deep dive into the science of wound ballistics, the Coupland, Rothschild and Newball book, which is, I think it's 2004 from Springer, called Wound Ballistics, Basics and Application, I've got on the screen. That's a really good, it's pretty science heavy. but it's the definitive text if you like if you want to know more about this subject. There is ongoing research, this is my bigger of my two rifles, this is the one that's bolted to the floor and ported down and we use this for some of the ongoing work and although I promised earlier there'd be no slow motion footage. is something that everyone really wanted to see. That is a bull bearing being accelerated into a sheep tibia and the reason I love it because it shows how hard it is to get it right. You can see the little plastic sabot crashing into the wound afterwards so completely voided the experiment. It's a good job we're getting a good deal on sheep legs. that is a good point for me to open a beer and us to um open this up to any questions or discussion so thank you very much for being so patient and uh and listening

We're then going to look at how tissue behaves when it's struck by bullets. And then we're going to look at some of the treatment algorithms. And I apologize, it gets a little bit...

a little bit surgical a bit orthopedic but that's what you'd expect from me I guess. Finally we're going to allow a bit of time for discussion and I'll talk about ways that you can find out more and I'm going to be a little bit self-indulgent and talk about some of the research that myself and some colleagues are doing down at Porton Down. So let's get on with the usual disclaimers. So as I said before I'm a regular commissioned officer in the Royal Navy but In between deployments I'm working at Oxford in the major trauma centre there and I'm actually just taken over as the clinical lead of the Oxford trauma service which is interesting to get to see all the datex forms about my colleagues which I enjoy. I'm also the consultant advisor in trauma and orthopaedics to help to advise commanders to any issues that pertain to trauma and also help to supervise and assist the next generation of surgeons which is probably the most interesting part of my additional roles.

Obviously got to emphasize anyone who knows me will realize that this really is quite an important part of the talk definitely my own views I don't represent or speak for the Royal Navy Her Majesty's Government or the Oxford University Hospitals Trust and in terms of conflict of interest I think it's a good time to say that I have one and I would like you all to buy my book. If you're interested in ballistic trauma it's a great way to sort of learn a little bit more and if you're just financially savvy if you note that the used price is currently about a third greater than the new price this book represents an excellent return on your investment as well so I urge you to do that do that as soon as we finish this talk. So why the title?

A few people have got in touch with me and asked about my interest in Welsh hip-hop. People might not realise this, but this was a title that I've plagiarised from an early noughties Newport hip-hop band. One of their tracks was Guns Don't Kill People, Rappers Do.

The reason I've chosen this talk is because I think when medics start talking about ballistics, we focus immediately on the wrong thing. There's far too much discussion about the firearms, the small arms that are involved. You hear things on the news about people being shot with a high velocity rifle and I think the focus is very wrong.

Guns obviously are important but it's the bullets and the bullet design and how bullets interact with the body which is far more important to us as clinicians. The other reason I've chosen this title is because all the good ones were already chosen by the people in the past. So I pulled out three fairly significant reviews from the literature. And if you look there's a common theme amongst the titles so lies, damn lies or ballistics, my personal favourite, wound ballistics a review of common misconceptions and applied wound ballistics what's new and what's true. The implication of the last title being there's an awful lot out there that's false and this is certainly my experience so as somebody who's spent a lot of time researching in this area you find a lot of stuff that's misleading and confused And I think this is because of the influence of politics and money.

So as an example, in the 70s, there were a lot of research papers coming out of Sweden that were talking about the brutal and inhumane wounding patterns from M16 rounds. And this was to do with their government's opposition to the... Vietnam War and the US military's new adoption of an M16 firing 5.56 rounds.

In actual fact, the wounds produced by a 5.56 NATO bullet, the SS-109, are just broadly similar to military rifle rounds that have been used for some time and in fact, if anything, they're a fair bit lighter. The other influence is money and particularly this is true in America. So the distortion of the gun lobby and non-scientists who are influential in that field have unfortunately sort of distorted the way we talk about it and the way we study it. So as a consequence there is a lot of misconception out there so hopefully at the end of this talk we'll have got to a bit better place. Having stressed the importance of bullets over firearms I think it's worth quickly just looking at some of the um some of the features of a firearm.

So this is a rifle, so it's a long barreled weapon. And just so we understand some of the basics of what's going on, the bullet ends up being fed up through a magazine here, ends up in a breech which is just here, which is sealed by the bolt where that slides forward. That then creates essentially a tube with only one opening at the business end.

The bullet when you pull the trigger is ignited or the propellant behind the bullet is ignited and the bullet is then forced down as the propellant gas expands. The bullet's enforced down the barrel, it accelerates and when it leaves the end of the barrel here that's the muzzle velocity or the velocity it has is the muzzle velocity which is the fastest speed that it's going to be traveling at through the entire course of its path. The inside of the barrel has a spiral groove.

and that confers a spin to the bullet which um confers stability and that's um that's the only time we'll be talking about um uh about firearms really in this in this talk so why is it relevant well they're common there's an estimation of about a billion serviceable firearms around the um around the world and the thing that would surprise us for those of us dialing in from the uk um we live in a country where the state has a near total monopoly on firearm usage. Obviously, it licenses under strict conditions and private owners to own firearms, like the one I just showed you. But we would assume that the majority of firearms around the world are held by police and militaries. In actual fact, that's not true. Globally, only about 15% of them are.

So there is a lot of sort of fairly loosely controlled firearms around the world. and the United Kingdom is not really representative of the worldwide situation. I don't think anyone would be shocked to learn that in terms of private ownership, the United States is way, way ahead of most other countries.

But you can see going down the list, actually, there's a lot of countries where private firearm ownership is entirely normal, and it's not a weird thing at all. And unfortunately, this is the truth of why this is relevant to all of us. So outside of the low-level criminality that's occurring in a lot of, increasingly a lot of urban centres in the UK, what we are preparing as clinicians at work across the country is to respond and to be resilient against the rewarding terrorist firearms attacks. Fortunately, still quite rare in the UK, but obviously Oslo, France, Mumbai, and sadly even just yesterday in Boulder in Colorado.

These events happen entirely predictably and entirely regularly unfortunately and as those of us who work in the emergency trauma pre-hospital and hospital environments this is something we need to make sure our systems are able to cope with. So not just firearms casualties but potentially large simultaneously numbers of firearms casualties. Obviously I'm in the military so we'll talk a very little bit about military firearms and This often surprises people that military, in a conflict situation, firearms are actually a relatively small course of casualties.

It's normally about three to one of explosive weapons to firearm weapons in terms of casualty generation. And that's remarkably consistent amongst the graph here shows the 10 years of the Iraq and Afghanistan wars, but that's remarkably consistent with Vietnam. and World War II and even World War I, where it was if anything it was skewed even greater in favour of explosive weapon causing injuries.

So let's get on to some of the science. Before we get into the Newtonian physics of this, it's worth stating that wound ballistics are entirely unpredictable. If we think about the ballistics that occur inside a firearm, these are known as internal ballistics, where there is an explosion of a set amount of propellants. That propellant confers a certain amount of energy into a bullet and the bullet travels down the gun.

When it leaves the gun, it becomes the study of external ballistics. And that, again, is incredibly reproducible. If you think about the accuracy of modern firearms.

with sub 1 MOA accuracy that will allow a sniper or marksman to reproducibly hit a very small target at ranges 800 meters plus. These are very precise machines, very precise tools and the ballistics, the science behind it is very predictable. As soon as that bullet contacts tissue, everything gets a little bit weird.

So the first thing I'd like to say is although I'm going to be offering some rules of thumb in this talk Wound ballistics are incredibly unpredictable. One of the difficulties that I'll talk about at the end is actually they're so unpredictable that trying to make a reproducible standardized model even under laboratory conditions is extremely difficult and that's basically why I've lost all my hair. So the first rule I'd use is that you've got to think about this in terms of energy. So remembering going back to our sort of school physics kinetic energy in the context of ballistics is the ability to damage tissue that's what you've got to think about kinetic energy is a potential to damage tissue the key concept to understand here is the rate that that kinetic energy is transferred into the tissue is related to drag and it's the this rapidity that our tissue slow down projectiles slow down bullets relates very closely to the severity of the wounds that are produced so a quick uh A quick rehearsal.

Kinetic energy is proportional, or sorry, in this sense, equal to mass times the square of velocity halved. So the key take-home to that is velocity is far more significant than mass in terms of the amount of energy that a bullet possesses, and we'll talk a little bit about that later on. So if you've got kinetic energy, that's a big bold KE, before you... is possessed by a bullet before it strikes a limb and this is probably now a good point to give a trigger warning this is the first of a series of x-rays and clinical photographs that are all used with the permission of the patient but certainly are graphic and if this isn't your cup of tea first of all you're probably in the wrong webinar and secondly I apologize if that did cause any distress but the kinetic energy on the left of the screen is what's possessed by the projectile before it strikes a limb it strikes a limb and then it carries on through. You can see from the x-rays that there's no retained bullet or fragments and that's because the bullets transited all the way through the limb.

So it still has kinetic energy, it's still moving as it hits the other side. The delta or the difference between the two kinetic energies is what's been transferred into the tissue and that's what creates this tissue damage that we're going to see. So that is conceptually, broadly how kinetic energy relates to wounding but...

it gets a lot more complicated than that because it's all about drag it's all about the rapidity that the um the the bullet is slowed down and the amount of energy it it deposits into the wound so there is um a beautifully elegant equation looking at that um but the uh there's not going to be a test at the end you'll be pleased to know the key things to pull out of this equation though is the drag force and the retarding effect on the bullet is uh proportional to the both the density of the fluid in inverted commas so the fluid in this case in the arm here was the ulnar bone so the the round contact of the ulnar bone and that's an incredibly dense fluid it's not a fluid I know it's incredibly dense tissue and that had a massive retardant effect on the bullet and essentially stopped it the other thing that's proportional to is the is the surface area of the front of the bullet so I've got a you a half inch round here and it's a spitzer design so it's got a um i'll put it up so you can see the contrast it's got a a nice sharp point and it's got a little boat tail on the back so it's a very aerodynamic stable design um that will that has a lot less resistance when it's traveling in this direction and forward than if it starts tumbling and it presents its side uh side on to the direction of travel so when a bullet tumbles like this it there's a huge amount more drag and consequently there's a much quicker, it slows down much quicker if that's not an oxymoron and the amount of energy that deposits into the tissues is much greater for a given time. and that translates into a much more severe wound. So I'd like to delve into some of the history now because it's quite a useful illustration at this point and I'm also I'm a bit of a nerd as well so I do love the history of it.

So back in the late 19th century the British military had just adopted a new weapon and as part of the new Lee-Metford weapon system, they probably didn't call them weapon systems back then, but as part of the new weapon system was a shift. from black powder or gunpowder, which created a lot of smoke, to smokeless powders. Now the reason to do this was to get rid of the smoke. If you had a large body of soldiers all lined up together firing their weapons, after three or four rob volleys there was so much smoke around they couldn't actually see anything to aim at and also their own position became very obvious. So it became a military requirement to switch over to smokeless powders.

And that was when these nitrocellulose and cordite family of propellants came along, became available. Now not only were these burning without smoke, but they also were much, much, much more powerful. So the military transitioned from lead rounds, the advantage of which is they're very dense and so they're very heavy and they have a lot of momentum, to what they call jacketed rounds or full metal jacketed rounds.

The reason they did this was when soft lead rounds were used with the new much more powerful propellant, as they were accelerated down the length of the barrel with a lot greater energy, they would shed their skins. I think of lead pencils. So the outer surface of the lead would foul the barrel and the barrels would have to be cleaned out between a few rounds.

Then that was causing stoppages and it was causing potentially breach explosions as well. So to solve that problem, they jacketed the rounds with a copper material. So then you had the core was made of a heavy...

dense lead so you've got the mass but then the copper coating meant that the bullets slipped down the barrel nice and quickly and you got the extra velocity as well so if you think of the kinetic energy equation you had the mass of the lead you had the velocity of the new propellant plus the copper jacketing and this is what we mean when we're talking about fully metal jacketed rounds and on the screen here we can see our original rounds but As so often with technology, there's an unforeseen consequence. And this is from a BMJ article in 1896. And I've got to be honest, if the BMJ still had a military and naval section, I might renew my subscription. But it is quite an extraordinary article because it's talking about the difficulties with the new type of bullet. And again, if BMJ articles were this interesting, they wouldn't stay in their cellophane.

If we look at some of it, we're talking about that the new rounds were traversing the soft parts of the body without smashing them, even piercing through bones without splitting them. It's reported that one tribesman who'd been hit by six bullets was treated in hospital and made a good recovery. I love the way the BMJ is reporting this as an undesirable outcome.

In consequence, the military authorities tended to turn their attention to the task of making a Lee-Metford bullet, which, without losing its ranging power, still inflicted a wound sufficient to... sufficiently severe to stop a rush. What they meant was a charge of people at British forces. The correspondent of the Times states that such a bullet has been devised by Captain Bertie Clay, superintendent of the Dum Dum ammunition factory.

So Dum Dum is a small town in India, and there was a large British military ammunition factory there. And dum-dum is where the expression dum-dum bullets comes from, because Captain Bertie Clay had the brilliant idea that you only need the copper jacketing of the round in the part of the bullet that contacts the inside of the barrel. So that's the bit where you don't want the lead fouling the barrel.

But actually, if you think about the lead at the front of the barrel, sorry, the front of the bullet, if you keep the copper jacket off that, what happens is you still get the... you still get the effect of the lead hitting the tissues and deforming. So I've got a, this is a soft nose round here and as you can see the tip of it is exposed lead and the side is copper there and when that strikes a deer for example it distorts and what we call expands and dumps its energy so instead of it having a nice a nice sharp tip like this round here it will deform and slow down very quickly as it passes through the tissues and then transfer most of the energy or transfer its energy very rapidly into the tissues and so these became known as soft nose rounds or because of the fact that they were first developed dum-dum bullets and example of a couple of couple of types here you can get a similar effect by having a hollow nose point on the tip of the bullet as well and you can see a clearer diagram there of how that peels back when it strikes tissue.

And I got a clinical photograph of, this was a police nine millimetre round that struck that ulna. And police around the world, our police officers as well, the live rounds they carry are, they practice with fully metal jacketed rounds, but the rounds that they carry on operations are soft-nose deforming rounds. So if you see someone in your practice that's been shot by a police officer, First of all, it's likely that they need the other kind of specialist doctor, the one that works in the basement. But secondly, they're likely to have been injured by these particularly damaging bullets that are soft nose and transfer a lot of energy. So the wounds are expected to be more severe than perhaps you were anticipating.

These expanding rounds were outlawed in the first of the Hay conventions by... by European powers together with America and the first Hague Convention. They're outlined for military use only and it's perfectly legal for hunters to use them and it's perfectly legal for police forces to use them. So let's have a look at some of the wounded interactions.

With all the caveats I mentioned before of the difficulties in predicting the behavior of bullets when they contact tissue We can, with some generality, divide the components of a wound into three main types, of which two are relevant and the last one's a bit of a included for completeness, is quite controversial. So the first bit's the permanent cavity or the wound tract. So this is, conceptually, as the projectile passes through the body it crushes and lacerates and tears the tissue and essentially what it does is behaves a bit like an arrow if you like. So if you had a nine millimeter arrow passing through you, you'd expect to end up with a nine millimeter hole in your body and that's similar to the permanent cavity or the wound tract of the the bullet.

It's roughly going to be the same size as the bullet and in theory if you have an entry wound and an exit wound in a limb you can look at the direct line between the two and one would anticipate, again this is not consistent, and these rounds aren't predictable, but one would expect that there'd be a line of tissue damage between those two wounds. It gets a bit more complicated when we start talking about temporary cavities and the effect that's sometimes described a little bit inaccurately as cavitation. So a temporary cavity is a bit more complicated. When there's very rapid transfer of kinetic energy into the tissues, the kinetic energy The kinetic energy causes an acceleration of tissue away from, radially away from the path of the bullet.

And that interestingly causes stretch and damage to the tissues. And I'll show you some photos of that in a moment. But that also generates a sub-atmospheric pressure because the tissues are pushed away. There's essentially a vacuum in the path of the bullet and that can cause small amounts of debris. to be dragged into the wound which can increase the contamination.

Cavitation is a pretty odd phenomena. Part of the large areas of misconception arise because cavitation is one of the more eye-catching and impressive phenomena associated with ballistics. So with high-speed cinematography there was an awful lot of very cool, very impressive looking slow motion footage of bullets traversing ballistic gelatin, soap blocks, that sort of thing, even underwater, and you create these very impressive looking bubble and cavity effects.

And people were mentally looking at these gelatin blocks and transferring those images into a wound and imagining that's the amount of damage that was done. And so they got some significant danger of overestimating the severity of wounds if you think too much about those techniques. If you look at the depth a normal bullet has to travel before it becomes unstable and starts tumbling and starts creating a very large cavity that's normally far wider than the average person's limb.

body. The final thing is shockwave. Now this is very controversial.

The American firearms industry talks an awful lot about this, this idea of stopping power and this idea that you can shoot someone and although you don't hit any major organs they drop because of some kind of semi-mystical shockwave. There is a shockwave, it generates quite low energies and it can There have been a couple of animal studies that have measured an effect on the central nervous system but I think in a lot of literature it is overstated. This is a quite a nice little picture that demonstrates the, you've got a handgun being fired, you can see the shadow of the bullet, it's black and white high-speed photography, and you can look at the ripples in the polarised light demonstrating the shockwave is in front of the path of the bullet.

So a shockwave is analogous to a supersonic sound wave so a sound wave traveling faster than the um speed of sound most um unless you're buying specifically buying subsonic rounds most uh most ammunition is supersonic um so my rifle's got a modifier a suppressor on it a moderator um but it still makes a loud noise because the bullet is supersonic so there's a sonic boom from the bullet um sonic booms are um are literally a shockwave being formed and so that shockwave precedes the path of the bullet and this occurs schematically in the, represented by the black lines moving in front of the bullets on the diagram on the top left of the screen. It's very low energy compared to the bullet itself. It does very little tissue damage, but as I said, in theory, the central nervous system can be affected by this, but in clinical practice, I would ignore this. Okay, so another one of my slightly late trigger warnings.

The other thing to start thinking about is tissues are not homogeneous, and tissues behave differently to stretch. So tissues like skeletal muscle and lung tissue, for example, tolerate stretch very well. They're stretched all the time in their normal function.

Other tissues don't tolerate stretch at all. So in the bottom left, we've got some sorry, that's skin demonstrating. You see the cracks where it's been torn, but actually overall tissue is elastic and tolerates stretch well. Lung, you've got a bone strike of a round hitting a rib and it's fragmented. But the lung tissue itself, although you can see it looks like slightly edematous, it doesn't look very happy.

It's contused, but it's clearly tolerated. There hasn't been a massive tearing and disruption of the lung parenchyma. Muscle tissue as well.

This is another fragmented round that went through them. This patient's right lateral thigh out of the right medial thigh and entering the left medial thigh. But again the tissue itself is looking actually pretty healthy and because it tolerates skeletal muscles looking pretty healthy because it tolerates stretch very well.

I think you can see from that clinical photo things could have been a lot lot worse if they're a little bit higher. Going into this fairly gruesome picture I'm not a hepatologist but I can conclude from looking at this picture that liver tissue does not tolerate stretch very well so this is a completely destroyed liver because liver just tears. So let's look at things that can likely make, so looking in a lab-based theoretical concept first.

Let's think about what things would be likely to aggravate wounds and it's all about the drag equation on the top right of the screen there. So what's likely to increase drag and increase energy transfer into the tissues? So instability.

So if a round's unstable, if we look at the top left of this round here is tumbling and so as it passes sideways, as it tumbles over on itself, it presents a very large surface area and so the energy is going to be imparted at a much faster rate and that's going to cause tissue stress stretch and tissue instability and this is going to give a shout out to surgeon lieutenant commander tom stevenson who's done a lot of good work at cranfield university looking at the effect of what happens when bullets pass through clothing before they go on to strike tissue and the effect of increasing um wound severity when a bullet does pass through clothing, essentially because it causes it to destabilize and so you get a lot more of this tumbling effect and a lot more energy imparting into the tissues. and I'm pleased to say that he published that around the world, but he's also got a PhD for that, so nice one Tom. Getting into the pathophysiology now, so the biological response to this, it's worth thinking about how the tissues are going to be responding. So the first thing to say is the amount of energy or the potential kinetic energy available in gunshot wounds is enormous.

So if we think of falls and falls and motor vehicle collisions as being on a spectrum. So ground level falls are on one end of that sort of low energy spectrum. As we're getting onto road traffic collisions we can get a lot higher and that sort of starts to approach in the sort of energies that are involved in gunshot wounds.

So they do tend to involve greater amounts of tissue disruption and destruction than we're used to seeing in our normal conventional practice. I'm talking predominantly here about higher energy weapons that you'd see on a battlefield, so more rifle rounds, so again more sort of, there's a comparison here, so more in my right hand, I had to think about that, a rifle bullet much bigger, heavier and fired with greater velocity than a handgun bullet here, so one would expect a far greater amount of energy transfer. from rifle rounds.

So what are the injuries we see? Well the primary injury is the immediate tissue destruction that happens within either instantaneously or within the first few minutes which is the shearing tearing laceration that results in tissue necrosis. There's tissue that's been traumatized often that's been stretched that will undergo a slightly more programmed apoptotic cellular death process. and that tends to occur in the first 48 hours or so and that's a bit more organised but that is also predictable and that will happen in a ballistic wound. Then we've got tertiary injury and we could talk about this as being the stuff that we as clinicians are supposed to prevent.

So if we keep the patient in a shocked and hypovolemic state they're going to be hypoperfusing their damaged tissues and that can cause more destruction. If we allow them to develop a compartment syndrome and the pressure in their muscular compartments increases, that can cause, again, late tissue death. And similarly, if we allow unclean wounds to become septic, you can get unnecessary late destruction from infective causes. I think what I'm trying to say here is... Gunshot wounds behave differently from conventional, even conventional high energy fractures.

So if I see a peel on, a nasty peel on, on day zero that it presents, we're going to take them to theatre. We're going to wash it out. We're going to put an external fixator on it and we're going to put a wound back on it. And the next day we're going to take them back to theatre and together with our...

plastic surgical collies, we're going to unwrap the wound and the wound will more than likely, if we've done our jobs right, be clean and that will allow us to put the plates and screws in to fix it, move the three muscle flaps, the gracilis flaps or the ALTs to cover the wound and then we can do the definitive procedure. You cannot do that with a gunshot wound, it will still be evolving, the tissues will still be responding. You can do a very good job of wound excision. on day one, and we'll talk about that in a moment, or day zero, sorry, but the wound will continue to evolve.

It's not that you haven't done a good job, it's that tissue that looked healthy and viable on day zero won't look healthy and viable on day one or two. So wounds will evolve and you've got to treat them with respect. Which brings us on to management protocols. And again, I apologise, this is a little bit more surgical orientated, a little bit more hospital-based orientated, but you shouldn't give a...

you shouldn't give a presenter link to a surgeon because they're just going to hold the mic I'm afraid. So we divide this up into decision, incision, excision and I'll talk about a few pearls, a few ticks and trips at the end. So decision is assessing the amount of energy being transferred into the wound and we'll talk a bit about how you can do that with fairly basic technologies and approaches.

Incision, so I separate, some people talk about debridement, I think that gets a bit ambiguous. I don't like it when people pronounce it in the French way as well, that's a bit pretentious, I'm saying that someone who works in Oxford and drinks lattes, but I think it's more useful to divide debridement into incision which essentially is extending a wound, making a surgical incision. opening skin, opening fascia, and that allows you to do two things. That decompresses a muscular compartment and allows you to explore and then proceed with the next steps of the operation. As distinct from excision, which is removable of non-viable tissue and gross contamination.

So together, those essentially are the two components of debridement. But I think it's worth dividing the two up because they serve two different purposes. So let's talk about decision making.

And you have another QR code here. a rather naughtily apologies injury but I made this an open access paper somewhere so if you want to download this this talks a lot about our experience from the last two conflicts of managing gunshot wounds and it did allow us to develop some rules of thumb again I'm contradicting myself I said there are no rules but there are some guidelines that you can sort of follow to assess these wounds so First of all, any high energy transfer wound or those with neurovascular injury need to be surgically explored. So if you've got an obvious, complex, large wound with a lot of obvious tissue damage, in other words, a big hole, that needs to be surgically explored.

A lot of tissue has been destroyed and you need to know what's going on. You need to actually perform an excision. If there's neurovascular injury, in other words, distal to the wound, if there's a neurovascular deficit, then clearly that needs to be explored.

And these are right off the bat, these guys, these injuries need to go to theatre. So having said that, if you've got a wound which doesn't involve a large amount of obvious destruction and there's neurovascular intact, you can start to think about what are possible features of high energy transfer. So the first one is fracture, and that's predictable from our sort of blackboard theoretical discussion. If a bullet strikes a bone, it's like to impart that energy quite quickly. And so it's like to be a more severe, high energy wound.

Secondly, if there's been retention of the bullet or indeed fragmentation of the bullet, all of the kinetic energy held by that bullet has been dumped into the tissue if the bullet's retained whole. If a bullet's fragmented, the concern is that each of those components of the bullet, it's going to be big. the jacket, the outer lining of the bullet that is retained in the tissue.

All of those individual pieces of fragments will have essentially become secondary projectiles and they will have caused their own permanent tract and permanent cavity. So one would anticipate a more complex severe amount of tissue damage deep in the wound. And that's also true of fracture actually. When a bone fractures or shatters as it often does when it's struck by a bullet, you create multiple small amounts of bone splinters.

that themselves behave as secondary missiles. So again looking back to this unfortunate or fortunate, depending on your perspective, casualty you can see the large amounts of the bullet fragment. I'm very confident to know, I had a paper reviewed by someone that very snookily said that this was a blast injury, but we happen to know how this guy was injured because his mate standing next to him that accidentally shot him was charged with the negligent discharge of his 5.56 FN Minimi machine gun. So we're very confident this is a gunshot injury.

But you can see on the CT scanogram on the left of the screen how the bullets fragmented and been deposited throughout his thighs and that's how we know it was a high energy transfer wound. You can see the very ragged wounds which also indicate that a lot of tissue loss. But as we said before the muscle itself has coped with that stretching pretty well. pretty healthy.

So that wound is after debridement and evacuation back, that's not what a gunshot wound looks like at first presentation obviously. So again going back to this tibia X-fix that's been, sorry tibia gunshot wound and open fracture that's been stabilised in an external fixator, you can see large amounts of multi-fragmentary damage to the bone itself and this is going to be a 25 year old, almost certainly male. um quite probably Fijian uh leg this guy's cortices are going to be rock solid so the amount of energy to shatter them is enormous and that energy would have been dumped into the limb there's no sign of the bullet or fragment so we imagine there's been a near and there's been some kinetic energy retained by the by the round itself but not a lot of that has been transferred okay so the experience of the Americans with handguns and lower energy transfer wounds is that not all gunshot wounds need surgery and with low energy transfer wounds you do not need to take these all to theatre. You can treat them with antibiotics, you don't close them primarily. Always split limb, that's important to kind of allow the tissues to recover and drain freely, but not all of them need surgical treatment and that can be very important if you're in a mass casualty situation and your hospital resources are being stretched.

If you triage these patients, assess their wounds properly, you can potentially avoid taking unnecessary theatre cases and using up your valuable theatre resources. So this heel wound that we saw before is a calcaneal fracture. but it's very neat. The other side looked a bit like that as well, it's impossible to say which was entry which was exit. X-rays showed a nice neat little hole through the calcaneum and there was no surgical treatment required, that's healed up nicely.

So we're going to get on to a slightly controversial area as we wrap up, we get towards the end of the talk. Textbooks on the top left have all argued for quite an aggressive approach to laying open all gunshot wound tracks and this has been quite aggressively taught, certainly to me, in military surgical courses. But interestingly if we look at the most experienced group of surgeons for dealing with gunshot wounds and particularly high energy gunshot wounds they were the senior surgeons of the second world war.

And the reason why they were so experienced is they spent the years of the First World War as junior surgeons learning their trade. And this was pre-antibiotic years as well. So these people were very good at treating and preventing infection with surgical treatment, with incision and excision.

And one of the most experienced was Olga V, who was a fairly angry general who experienced both world wars and wars in the Balkans as well. and as you can see he was quite adamant that unnecessary operations on through and through wounds affecting the soft parts are completely unnecessary and can potentially, his concern was the surgeon can do more damage in the bullet. He emphasizes that too much skin is being removed, skin is the most, of all structures, is the most viable, the most resistant to infection and the most irreplaceable as my plastic surgical colleagues would agree.

It can split it to give access but never excise except just in the edges of the wounds. Circumcision of entry and exit wounds is the hallmark of a novice. Just imagine this guy shouting at his junior surgeons. And again, point three, which is almost the same as point one, wide excision of muscle, especially transverse section of muscle groups to expose a tract.

I have been told to do this, which is quite interesting. So the Second World War and First World War surgeons were very anti. So is there any science to back this up?

Well these are two experimental papers, both of which came, so they're animal-based studies, but they came from two groups of surgeons that had both been in previous military conflicts on the left. We've got Martin Fackler, arguably the granddaddy of ballistics research in the modern era, and he'd been in Vietnam as a naval surgeon, transferred over to the army and started doing research for them, and he proved with modern assault rifle wounds they uh that he somehow caused to dogs and they healed up fine with that surgical treatment and ditto a um paper on sheep by a couple of british surgeons that both served in korea came to a very similar conclusion that simple straightforward uncomplex wounds did not require aggressive radical surgery so i'm going to skip ahead now and I think we're getting close to time so forgive me I'm going to leave some of the um um leave some of the more surgical uh minutiae and um I will get on to I do love an x-ray that's the same I'm gonna skip past these um I'll talk about the options for um if you were interested in learning more about this subject um if you want something that's more clinically orientated this is another um blatant plug but please feel free to um buy the book. I don't get any money from it. I think we donated all the royalties to, I think it was Blesma. But that's very clinically orientated.

If you want a much more of a deep dive into the science of wound ballistics, the Coupland, Rothschild and Newball book, which is, I think it's 2004 from Springer, called Wound Ballistics, Basics and Application, I've got on the screen. That's a really good, it's pretty science heavy. but it's the definitive text if you like if you want to know more about this subject. There is ongoing research, this is my bigger of my two rifles, this is the one that's bolted to the floor and ported down and we use this for some of the ongoing work and although I promised earlier there'd be no slow motion footage. is something that everyone really wanted to see.

That is a bull bearing being accelerated into a sheep tibia and the reason I love it because it shows how hard it is to get it right. You can see the little plastic sabot crashing into the wound afterwards so completely voided the experiment. It's a good job we're getting a good deal on sheep legs. that is a good point for me to open a beer and us to um open this up to any questions or discussion so thank you very much for being so patient and uh and listening

Transcript for:Wound Ballistics Lecture Notes

Transcript for:
Wound Ballistics Lecture Notes