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Gait Analysis for Postgraduate Orthopaedic Exams
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Gait Analysis for Postgraduate Orthopaedic Exams
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Language: EN.
Segment:0 .
The I want to welcome everyone today. It's a very warm July day, and we're going to have a talk today by Mr. Stephen Cook from University hospitals, Coventry and Warwickshire. Who's going to talk to us about the gait cycle? Now, just a few things beforehand. I will just want to mention about another course that's coming up.
That would be. On the 28th of August, case discussions for your orthopedic exam just to get whether the advent of the sort of novel clinical stations being virtual, we're trying to get a few more courses where people can have a chance to practice going through how you go for a case based discussions. So hopefully this will be helpful towards the clinical parts of the exam.
And there's, of course, being run through the orthopedic Academy on the 28th of August. OK, we just stop shared. Right and just to. A few words to say about Mr. cook. So he's trained in Edinburgh and have been working as a consultant at Coventry hospitals since 2011.
And in the pediatric department with special interest in cerebral palsy and has been running a gait lab at GW for some time, I was very lucky when I was doing my pediatric fellowship to work with Mr Cook and the valuable experience. He explained the cycle very well. I just wish I'd had the chance to use it in the exam. Unfortunately, didn't ask me about it. He also has been the National vitiligo trainer of the year in 2012.
I took forever to do, I'll pass it on to Mr Cook. OK um, Thanks very much, David. That was a very generous introduction, so and and Thanks for inviting me to chat to you guys. So as David said, that my main subspecialty interest is cerebral palsy, and as part of that, as most of you are aware, gait analysis forms a fairly integral part. So I've designed this talk in sort of two or three sections. The first pictures, a little bit of fun, really just background of gait and a little bit about why I find it so interesting.
And then we'll get into the nitty gritty about the gait cycle, and then we'll hopefully end on a bunch of cases. You guys get used to talking about gates, particularly for the exam, but also it's useful for your practice in the long term. All right. So bipedal walking is actually surprisingly recent. So it's been a couple of million years or so since by Peter walking started.
And compare that with quadrupedal walking, which is sort of like nearly $460 million years ago was the first quadruped on land. So there have been some evolutionary adaptations to our anatomy and physiology to allow for bipedal walking, but it's nowhere near as well adapted as quadrupedal walking. And these are a few of them. So we have a wider pelvis. We have much longer lower limb bones, great, great and deeper arms.
They're thicker and knee joints in particular are much thicker. Same with ankles. And we've got adapted feet and so forth to accommodate it. However, there are some things that are particularly unusual. So in order for us to walk upright, if we didn't have this large thoracic kyphosis, all of our organs and heavy bits would be too far forwards or center of mass would be too far forwards, and we'd be constantly toppling forwards or using muscles to keep ourselves erect.
So we've developed this big thoracic kyphosis to keep the chest back and keep the center of mass over the hips. But then, because that's got a kyphosis, you then need to have a lower doses in your neck and the lower doses in your lumbar spine. And this is probably the origin of most back pain problems in humans. Now compare that to a great ape that's just got this die straight back from head to coccyx completely straight.
So that's how you would design it back if you could. But because we now work on all fours, we've got these adaptive adaptations. So some are good, like the big legs and the big knees and the long muscles and the long lever arms. Some aren't so good like that. The three curves we've now got in our spine, but also some non skeletal adaptations. So our muscles, particularly our lower limb and our anti-gravity muscles, are much stronger.
The muscle composite composition is different. So whereas great apes got a much more higher percentage of fast twitch fibers for explosive power, we've got a lot more of the sort of slow twitch fibers for strength and endurance, and we've also got a number of neurological changes to allow this to work. Um, we're also incredibly good at it, takes a baby around about a year to walk and buy around about age six to eight.
We work like adults. We can run, hop, skip, jump. We can climb up and down things. We can go with just about any terrain and we can do it for ages. We can walk and walk and walk. But we don't really know how it works. There's a surprisingly little amount we know. So this is the stuff we do know, we know about the anatomy.
We know every bone is. We know wherever we joint is. We know where every muscle is. I know the knee surgeons come up with a new structure and the posture or posterolateral corner every year. But generally speaking, we know where everything is. We know where the nerves are. We know where the muscles and tendons are.
We know how these things work in fairly intimate, intimate detail. And we've actually got some fairly good models of how human humans work, and it's the so-called double inverted pendulum. So that's a pendulum. That's an inverted pendulum. There's a double pendulum and there's a double inverted pension.
This is your foot down here, your knee, your hip, and then obviously got head arms above that. So actually, we're not a double pigeon, we're a triple pendulum. And so this is a triple pendulum in action. And one of the things to notice is how chaotic the movement of the points below the single pendulum are. So the single pendulum arc is utterly predictable as a mathematical equation that would describe that with perfect precision and any point of time in the future.
You know exactly where that's going to be. But now, if you look at the absolutely crazy movement, particularly of the little bottom ball on the right hand, it just goes all over the shop. It's inherently chaotic. Chaos isn't random. We'll talk about that in a second, but it is very, very, very hard to predict. And that is that we're not just a normal pendant with an inverted pendulum, and it's more complicated than that.
So this model, for example, models the head, arms and trunk is a single bar, but we're not as fine moves, our arms move, our head moves on our neck. This is obviously a sagittal plane. And this equation up here on the top right is just the equation of State for the movement at the ankle. And that's only in two planes. That's only in the sagittal only one plane so of to plane.
We haven't even thought about coronal or axial planes yet, so it's insanely complex. And remember, chaos isn't random. Chaos is a deterministic system system, but where arbitrarily small perturbations lead to great, huge, huge differences in the eventual outcome. So just go back to that triple pendulum model. You can change the initial state of the pendulum by orders of the width of an atom, and it will have a magnet, a large effect on the movement of the distal part.
So it is deterministic but very unpredictable. There are some quite I said, these are some quite good models of how things work. Most of you will be familiar with azimo, the Honda model. They've kind of retired that now and more recently, this dude Atlas Boston Dynamics and these robots can do phenomenal things. This thing can run.
It can jump. It can do all sorts of acrobatics. It can get up. If if it's knocked over, it can do all sorts of quite cool things and you sort of think, all right, we must we must have sorted how we want them, because if we can make something that does this and surely we know must know everything about walking, there's lots and lots of problems.
And the big problem is we just don't know how the control mechanism works in humans. We don't know how all everything everything puts is put together. And this is just a given illustration of why we don't know why it's so complicated. So in medical school, we're taught that muscles can effectively pull and they're kind of on or off.
But muscles are much, much more complex than that. So let's take the gas drop, which is a fascinating muscle so originates above the knee on the back of the femur passes behind the knee. It's got a muscular portion. It's got a neurotic portion. It's egawa neurosis, then turns into a tendon which inserts onto the tendon or the aponeurosis of another completely different muscle.
Then it goes down and performs the conjoined Achilles tendon, which then passes behind the ankle joint and behind the subtalar joint before it inserts into the calcaneus. So this muscles got incredibly complex anatomical arrangement crossing three joints. It's got two different parts medial and lateral on each of those parts can be activated in a myriad of different ways.
You can activate it with incredible precision. One of the quite cool things to do. So if those of you who drive next time you go for a drive, please make sure there is no one behind you. But try breaking with your left foot compared to your right. It's really, really hard to do. So you've trained your gas stroke over the years to answer Yes. To a certain extent, it's to provide a perfect, really exquisite control over the pressure it can do.
That's how it works during walking. So the muscle isn't just on or off. Different parts of it can be on or off. Different parts of it can activate at different rates. Different fibers within the muscle can be activate activated at different times. And this is one of the things I'll hopefully try and convince you all how this works by the end of the teaching session, even though this muscle passes behind me.
So you think it should flex it? It is one of the most potent extenders during gait. And that's part, and it's mainly because of momentum, the ground reaction vector and the fact, it depends upon the state of the other joints it passes and the other muscles. So I'm going to go over that again, because that's really, really important towards the end. It's also mind numbingly any energy efficient and just to illustrate this.
Humans take around about two, 2 and 1/2 joules per kilogram per meter of walking. So if you take an 80 kilo person, I pick that because that's roughly what Atlas robot weighs weighs a little bit more, actually. So you take an 18 80kg person walking it about standard walking pace. We use around about a millijoules an hour, whereas Atlas uses over 13 millijoules for the same hour of walking.
So it's about it's over an order of magnitude more efficient as human walking, so around about 15 times more efficient. And again, just to put that into a sort of real-world example, imagine those of you who have Teslas about 300 miles per charge. So if Tesla's batteries were as efficient as humans, you'd go 5,000 miles on a charge. There's a big Gulf in understanding between sort of robotic walking, if you like in human walking.
This is what our lab looks like. So it's a long, thin room with a bunch of motion detecting cameras around the ceiling, some force plates in the middle that measure the ground reaction force. This is my son, Harry, all when we were opening up the lab, we had to get a bunch of inverted commas, normal patients in the lab to walk around and provide our normal data set.
So he's got a number of markers which are placed on the bony prominences, and these are placed in very specific ways. It takes our therapists quite a while to learn exactly how to put these markers on and where to put them. Because if you think about it, we're trying to build a skeletal model based upon the skin, and so we have to put these on in the right place.
There are some places that easy. Like ASIS and easy to find them that easy to find that it may be a natural ally. Much harder, actually to find the center of the new joints, particularly on the lateral. So it it isn't easy to do, but that and that's one of the drawbacks I think of getting as this is getting the markers on in the right place. But anyway, that's what we do.
And then we get them walking up and down the laps. So we just found out this works better, actually if I'm not in presentation mode. All right. So this is Harry walking up and down the lab. And you can see he's got a bunch of markers on the little Black boxes that you see. If I pause it, these are surface emg, so we can pick up very crude just on the flexor and extensor compartments so we can pick up a bit of EMG data as well.
We walk up and down the lap. Then next thing you want to do is pick up the ground reaction force. So this is Newton's third law in action. So Newton's third law, every action has an equal and opposite reaction. So as Harry walks across the lab, if I do to say mid stance here, this arrow is his ground reaction force.
The way it's set up in the lab is that the size of the arrow is the magnitude of the force. Remember, a force is a vector, so that that's the size. And obviously the direction of the arrow is the direction of the force, and you can see how it moves throughout the gait cycle from initial contact through to towel off. And if you think don't think like a surgeon for a bit, just think like a physicist or an engineer, it's this force that is responsible for the external moments around your legs.
So this force times the distance there is at the moment around the need. This force times the distance there is the moment around the ankle. If you chase that up towards the hip, that's the moment there. So this data. This ground reaction force is what's allowing us allowing the computer to calculate the moments.
And from that, we can also calculate the power. So this is going through it. So I'm just going spend a little bit of time on this bit, just going through the bits of the gait cycle. So you've got initial contact, initial contact is a point in time and the initial contact should be with the heel. So you can see how he's got a normal heel strike then. You've got low response, the knee bending and the foot becoming flat.
So it's very, very quick. This is 25 frames a second, so literally only got two frames between heel strike and foot flat. So it's very, very, very, very quick. And this is a so-called first rocker in terms of ankle movement, or it's called load response in terms of the gait cycle. It's also called first double support because it's got you've got both feet on the ground.
And at this point here your ankle, your foot is allowed to contact to the ground in a controlled way under the eccentric control of TBE n.s.a. and toe extensive. So this EMG here will be firing like crazy as Harry's tabun is firing eccentrically, allowing the foot to hit the ground in a controlled way. Without that, you get kind of a foot slapping.
I've unmuted myself somewhat, said the host muted me, somewhat muted me anyway, I hope that wasn't personal. Maybe, maybe, maybe the claw palsy shit so far and they decided, that's it. Anyway, assuming I'm unmuted now, I'll carry on someone. Please tell me if they can't hear. All right. So first rocket or load response, then, as the foot is now flat on the ground.
And obviously as the foot's flat, the tibia is advancing across the foot and so the foot, the ankle is also flexing. So from that point there to that point where the ankle is dorsal flexing. And the ankle is Dorsey flexing in a controlled way? We don't want this to happen too quickly because otherwise you can get all sorts of great problems. So gastroc here now is Tim and is now turned off and conciliate are now firing so this EMG would be starting to register a response and again, it's eccentrics at gas rock is contracting, contracting, contracting.
Loading up that Achilles tendon look at Harry's Achilles tendon is under a lot of tension. They're building up all that elastic potential energy, preventing the tibia, folding forward to rapidly and at this point, near. So look, look here. So at this point here, the ground reaction vector is behind me, but at this point here, it's now in front of the knee, and that's now causing it extending moment.
I'm going to go through this again because this is really important. The knee is now extending. That's happening passively. Just to this point here, so let's go over that again, so foot flat ankle is now Dorsey flexing, just rock is contracting like crazy to prevent there to be a moving forward to fast ground reaction, vector moves through the center and then in front of the knee.
Knee starts extending to this point here. And you can just see it now. The origin of the ground reaction vector right at the front, right up between first and fifth metatarsal head. All of Harry's weight now is through the forefoot. The heel is just about to lift off, lift off the ground and then you get this explosive plunger flexion of the ankle to push the limb forwards.
All the textbooks say this is concentric contraction of your saliers, and you should say that in the exam because all the examiners believe that too. But actually, this is actually mostly passive in normal, working at normal speed, partly because during this phase of gait cycle, you're building up, the elasticity in your gas, in your Achilles tendon. And actually in this at this point here in normal, working at normal speed, not running, not jumping, it's just elastic.
Recall that causes that frontal of flexion and the forward propulsion that's actually isn't very isn't very active there. But generally speaking, the textbooks third rocker or the end or terminal stance pretty swing is concentric contraction of your that pushes that leg forward for swing phase, so you don't really need your hip flexors much in swing phase, it's just all propulsion from the gastric.
Right so I'm going to go through this again. Let's just go to slap presentation, which this is just a little word about how the ground reaction, how one of the ways you can think about the ground reaction better. So imagine this leg of this person's leg would just suspended in the air if I push on the little foot in that direction. I think you'll all agree that's going to extend the knee.
So if I push that way and he's going to straighten and the magnitude of the moment is the force, whatever that force is, times the perpendicular distance. So not this distance and not that distance there, the perpendicular distance to the center of rotation of the knee. So force times, distance moment Newton meters. And as long as that arrow is in front of the knee, it will always try and straighten.
It doesn't even matter how close it would get. Obviously, that distance is much less so that force times distance is much, much less than movement is less, but that's still an extending moment. So if I push on the foot in that direction, it will try and straighten the knee. Not as much as if I pushed on it with in that direction, but it's still going to straighten the knee.
And as soon as that ground reaction vector goes behind the knee, it becomes a flexing moment. And now Harry or whoever's white bag, if you stand like that, that's a flexing moment, and it's that force times that distance. OK, so ground reaction vector in front of the knee is an extending moment. Ground reaction vector behind the knee is a flexing moment. So this is where I'm going to try and convince you how Gus extends the knee, right?
So remember we said in second rocker, it's your gastrocnemius and your Soler's is firing like crazy to stop your tibia going forward. So if you've got momentum taking your body forwards but your tibia is being kept in check, then it stands to reason your knee is going to extend. And the way we can map that is by showing where the ground reaction vector. So look at Harry's knee at the end of load response, the knee is relatively bent around about 30 degrees or so.
The ground reaction vector at this point is behind the needs a flexing moment. So the only thing that's going to stop that flexing is quite so at this point. In load response, quads is active. It's surprisingly not active that much or anything around about 10% to 15% your maximum contraction of your quads in normal walking. But there is a little flicker of quads activity.
Then you get to this point here in. That mid stuns, so in mid starts now. Harry's ground reaction, but you're right through the center of the knees, there is no moment, there is zero moment because there is no distance. They can't be a moment if there's no distance. So at this point here. Knee flexion is now stopped. And as soon as I go one frame forwards, it's now an extending moment.
It's a tiny moment because that distance is very small, but it's an extending moment. And if I go through a few more frames, it gets a little bigger, a little bigger. Now watch what happens to Harry's knee. Knee flexion. Knee extension. Knee flexion. The extension?
Not because quads is extending. The knee quads is completely off. Now this is a normal gait. This EMG will be silent. This is an entirely due to the ground reaction vector being in front of the knee. And the only thing that controls that is your. So your gas stroke is extending your knee, even though the heart is behind your knee.
It's a potent knee extender, and this is something called the plantar flexion knee extension couple key couple. So your ankle plantar flexes that are controlling your knee extensively and it's incredibly important concept. And when we're prescribing orthotics. For gait improvement and tuning them, this is one of the primary things on. The first things I'm looking at is where is this line going during stance phase?
And I'll show you, I've got plenty of examples of pathological gait where that's been disordered plantar flexion, knee extension, couple mid stance to terminal stance knee is going from flexion to extension. Quadriceps is completely off. Gas stroke is firing, extending the knee right. If anyone doesn't understand that, put it in a question and we'll go over it again at the end.
This is one of the most important concepts when you're prescribing orthotics. All right, let's skip on a phase. So this is now the next phase of gait analysis. And now we've got Harry walking and we've got the ground reaction vector. The computer can build up a wire model and then we can dispense with Harry altogether. And now we've got the y model and the advantage of this.
I can't see on this because this is just a static video, but in the gait loud, we can rotate this around. We can look in any plane from top to bottom, side to side. There's an entirely computer representation of where those dots are, why those dots are. And from this, we can calculate joint ranges, moments, powers and all the other stuff that you'd have seen when you've seen gait graphs. So this is the raw data, if you like, but obviously we need to get that into a form that we can understand.
So let's just go to this, and you guys may have seen graphs like graphs like this, and this is how we present it in the lab. So on the left hand column, here you've got our kinematics. So this is just the movement of the joints and we've got various conventions. So in our lab, red is left, blue is right like the political spectrum, but other labs do it differently.
So you have to do a little bit careful. If you're in the exam, it will be labeled, you will be told which is which. Most almost all gait graphs I've ever seen have got a gray bar. This is our normal values and our laps remember to hurry through my lab. We had 20 kids to the lab of varying different ages and this is our normal. So you should in the exam, also get a normal, a normal bar.
And that's the gray bar. What normally happens? So that gives you a bit of a step up in terms of interpreting these graphs because you already know what's normal. And then, as I said, these are usually averages and then this is the kinematic, just the movement. These are our moments. These two sets of graphs are on the right hand side are the next two columns on the moment.
This is the kinetics. These are now the joint forces. And this is moment and this is power. So moment, as we said, you all know what moments are there force times perpendicular? This force times perpendicular distance. What most people don't understand, and I won't spend too long on it because I don't think it's important for the exam is what Power means.
So when we talk about power in orthopedics, we often talk about muscle strengthening. I've got power 3 out of five or power 4 out of five. That's not what we mean by power in gait analysis. This is true physical power joules per second watts. And those of you who are familiar with cars and so forth will know that the way you calculate the power output of a car is the talks at the moment multiplied by the angle of the turning speed of the crankshaft, and that's exactly the same in these graphs.
So it's your moment. So the magnitude of this graph multiplied by the angular velocity effect with the slope, the gradient of these graphs. So if I pick an area here where there is a large moment and a relatively fast rate of moment, you see a big large amount of power. Or if you take this graph, for example, this patients need barely moving at all. In stance.
Phase no movement zero gradient, 0 power. OK, so that's just a moment. This isn't strength. This is mechanical power. True mechanical power joules per second or what? They're normalized for weight. All right. So but we won't talk too much about powers powers because it's unlikely to come up in the example.
And then we can create some date reports which look very cool and we can send these to parents and physios and make recommendations on various different things, so that's kind of what we do in the lab. So this is a quick. How are we doing for time? 25 minutes. OK, so this is some pathological gait now. So this actually just go back.
Like I said, it works slightly better in this review. So this is a gentleman with cerebral palsy. I'll play it full speed. Start off with and you can see he's got this. So definitely something wrong with that foot, particularly the right side. So he's got deeply. It's asymmetrical to the right side's worth and there's left. There's a few things that we look at when we're trying to describe gait and in the exam and also in your clinical practice, when you don't have access to a gait lab, you're really going to only see gates do visual gait analysis.
Some of you might do a video, I suppose, but very few of you will actually go through and get 3D gait analysis. So the most of the rest of this talk is going to be generally about the visual interpretation of gait. And there's a few things that we look at, and I'm going to go through these a few times as well, because it kind of gives you a structure about how to look at gait.
So the first thing is initial contact. So let's do a right foot gait side, right foot gait cycle. So what hits the ground first? You can see on this case, actually, let's go to Sanjay tools for him. I think it's better. Let's go to a right. OK, let's go back a few. OK to do just spin on fight up note to fast.
Look good, all right, so no, no ground reaction to yet, and nothing's touch the ground and you can see that as soon as the ground, but actually that's initial contact, so initial contact in his cases with the forefoot. In fact, it's almost entirely with the fifth 3 four foot contact. And then it's been on. Now watch look at his look at his knee.
Remember, I showed you with Harry, my son when it got to mid stance, the ground reaction vector was through the middle of the knee. See with this chap his ground reaction, but it's always behind the knee, so that is causing a flexion moment. And the only thing that can stop the knee buckling is now his quads. This lad has already weak because of cerebral palsy, has to use his quadriceps to keep his knee straight during mid starts and even as dance progresses.
Flexion flexion flexing movement flexing movement never gets that ground reaction vector in front of the knee always stays behind it. So then for these person, we say the plantar flexion extension coupled is impaired or even in this case, absent. He cannot get his ground reaction vector in front of the knee and therefore cannot get that extending movement. And therefore, the only thing that's going to keep his knee straight is his quads, which is going to increase the energy expenditure it's going to pull on his patella, given that patella to stretch out his knee ligament, his patellar tendon.
If I ask any of you healthy individuals to stand or walk with your knees bent like this for a long period of time, you're going to get your quads, are going to stop burning, it's going to get really uncomfortable. And this kid's already weak because of his cerebral palsy. So this is what you mean by an absent punch flexion extension. A couple and the knee just stays bent, stays bent, stays bent and then carries on. So that's kind of.
And then if we look at his graph, let's go to this one. So look at this, so this is his new flexing moment, so we can we've just shown you on the video how he never gets the knee extension moment as the normal one. It just stays flexing and his knee is obviously there without the knee, extending moment can't extend. This is where they should go. They should go.
Your knees should go almost to full extension by mid stance and terminal stance. But in his case, they just stay bent. My statement? Now what's really interesting about this lad is that clinically so you examine him on the couch, his knees come fully straight. So this is not fixed flexion contractors. Each each grid line here is 10 degrees, that's 10, 20, 30, between 30 and 40 degrees.
This is not fixed knee flexion contracted on the couch, his knees fully extend. So why is this happening? Why is he getting? Why can't he do that? It's entirely because he cannot get his ground reaction vector in front of the knee. OK, so what do we do? So we come along and we prescribe them and orthotic.
And unfortunately, I don't have the overlay of this, but it's still fairly convincing. So now look at his let's get his right foot. So right foot initial contact. So now he gets a heel strike. Previously, his right foot, it was the forefoot. They hit the ground first, so he's now got a first rocket. Now watch what happens to his knee now. So now the neatest shorts get slightly away, but now the knees straight and straight and straight and straight and straight and straight and straight and straight and straight.
And so almost out to full extension at toe off. So we've taken him from being in a crouched position to getting his knees straight, and that's just because of the orthotic prescription. No surgery has happened here. No botox, nothing else. Just by controlling the punter flexion, the extension couple. This is an AFO with some wedging. He's got a little bit of a rocker on his.
It's also just by orthotics. We've transformed his gait. And so if you walk, watch him walk. Now is now watch that needs they need just extends really nicely during the stance phase now. Bang much more natural gait, definitely still abnormal, but completely different to this gait. And because now he doesn't need to use his quads is quadriceps muscles.
It will be much more energy efficient for him, so he doesn't need to now burn his quadriceps every time he stands. And it will hurt less because he's not pulling on his patellar tendon every time and causing patellofemoral pain. So that's how orthotics can be used, right? And some just got just to finish off this part of the chat. I've got just a few tips for the fastest thing.
So most examiners are not gait lab trained Peter Potts, who treat the kids with sleep. Most will be like a foot and ankle surgeon or a knee surgeon or hip surgeon, so you do have to play a little bit to your crowd. And if you see an obvious gait abnormality, then just say so. So if you see a tendon and bone gait or an antalgic gait or a short leg gait or a high stepping or the classical gait, just say so.
I don't think there's any necessity to go through the sort of details of gait analysis if it's a fairly obvious gait abnormality. But this is sorry. I'm telling me to finish. But if you do see a really obvious, if you don't see an obvious abnormality, then you do need a structure for how to visually describe someone's gait.
And this is how I would propose that you do it. So get used to watching a patient walk away from you and looking at their right hand side. So that's looking at their right hip, knee, foot and ankle, then get the patient to turn around and walk back towards you, but carry on looking at the right hand side from your point of view. So now you're looking at the patients, the left hand side, so you're watching their right leg as they walk away, watching their left leg as they walk back towards you.
But you're always looking to the right, see what hits the ground first. So initial contact is with the whatever it is. Then the next thing to look at is stability and stance phase, so are they are they wobbling from side to side? Do they need to use a stick or a cane? Or, God forbid, do they fall or have to use the wall? So what's the stability like in stance phase? Are they clearing and swing plays and there's two things you need to clear, you need to clear the floor and your other leg.
So is clearance adequate? Then is there is an order for you to progress through and what you have to have a step length and the step should be either normal, increased or reduced, some people try and dramatically increase their step length to make up for poor cadence. They effectively can't walk as many steps per minute, but take a longer steps. Most people with great problems actually have a reduced slap length.
They don't progress as much, and it is a judgment. You can't say definitely what's normal and only sort of say if you think, think it's really abnormal. And then so you can bring bill the epimysium into one sentence, you say, as they said, this patient's initial contacts were healed, which good stability and starts phase adequate clearance and swing, and there appears to be normal slap.
Then one sentence and you describe those four bits of the gait cycle. You needed that for each leg left and right. And then the last thing to comment on is something called energy conservation. So energy conservation is a somewhat nebulous term or it's not nebulous. It's actually physically defined in terms of oxygen consumption, but you can't do that in the visual analysis.
So you have to kind of just sort of cap it off with a statement of what you think the patient's energy energy expenditure of walking would be like. Generally speaking, the energy expenditure of walking is to accelerate your center of mass. You have to accelerate your center of mass forwards to progress anywhere. But you shouldn't really have to accelerate left, right or up and down or accelerations in forwards and backwards in the sort of transverse plane.
So if you do see big trunk sways from side to side or the patient's going hiking up and down, so they've got, you know, they've got a foot drop on the other side, step to lift their leg up high. Then you can sort of say, actually, there appears to be increased energy energy expenditure or reduced energy conservation. So just to go back, initial contact is with the field.
Usually, there is good stability in stance. Phase adequate clearance and swing increased at length and there appears to be good energy conservation. And that gives you something to say if you cannot obviously see an abnormal gait pattern. And it sounds intelligent. And certainly if you're speaking to someone who's used to looking at gates, it's kind of the sentence that I want to hear those five things.
So initial contact clearance and swing stability and sense energy conservation and statment, they're the kind of five things that you want to kind of bring into your gait discussion from visual gait analysis. All right. We'll get a chance to practice that when we do some of the questions. This is the next hop tip is just not to get too muddled with the gait phases.
There are lots of different ways of describing gait changes. Most gait labs and gait analysts use spaces Jacqueline Perry, who described these back in the 60s and 70s and their low response, mid stance, terminal stance pre-spring and then initial mid and terminal swing and generally speaking, low responses. Your first 10% and mid stance and terminal stance at 20% each. And then pretty swing is your last 10% each.
Dance phase and stance phase accounts for 60 to 62% of this cycle and then initial mid and terminal swing 13% for each of them. And that's your 40% of swing swing phase. So these are they're the phases that most analysts use. However, most of the time, certainly if you're doing foot and ankle clinical vivas or with a non gait surgeon, they talk about rockets. And we've kind of mentioned these already.
So you've got your first rocker, which is during maintenance, actually only the first half of the load response. And that's your ankle going from neutral to punter flexion eccentric contraction to your second rocker, which is a big chunk 40% This is your foot flat to the ground. We've got tibia advancing over the top to your ankle is dorsal flexing, eccentric contraction of gastric sleeve and then the third rocker pretty swing, which is your ankle plantar flexion concentric contraction of mattress sutures or elastic recoil.
But I probably just stick to concentric contraction and then swing phase initial mid and terminal just split into thirds. So these are kind of how a lot of sort of non gait analysis, all the parts will talk about things. And the other thing you might come across is double support, single support. So you've got first double support, which is load response and you've got both feet on the ground and first single support.
So that one, for instance, phase the other foot in swing phase, then you've got second level support. So this is in pretty swing. Two the end of stance phase for one limb and the other. The other limb is now in low response and then your second single support during swing phase. So sometimes you'll see these phases described double spot, single squat, double support, single support. And another way.
So there are different ways of describing gait, probably from your point of view in the exam. Most people, certainly non gait surgeons, none. Gait analysis of the pods will talk about the ankle rockers to describe the phases of stance stance phase. So again, play to play to your pediatric liver and you know it, then go to these. But I wouldn't spend too much time learning these unless you're particularly interested, right then.
So I'm going to I think I'm going to stop yakking there because that's most of the gait chat. So, David and honey, I don't know if there's been any questions so far. Let me just stop sharing. And no other questions, I can just tell in the chat group have their honey. No, no.
OK David, you are a muted. Only one question here. So what's happening in running? Yes I can't see I can't see a chapter, so I don't know, I can't see it that way. So what happens in running a store? Muted, I can't hear you. What's happening in running? You hear me?
Oh, wait a second. I've got the I've got the I've got the. OK, I see. So one question about running and one question about crouch gait. I'm going to slightly gloss over running. So it's not that it's not important. It's just I've never seen a game. I've never seen a question about running.
It is a very sort of specialist topic. One one of important things to remember is that for the normal walking, you need surprisingly little muscle, muscle strength. So all of the reserve you've got, so you'll need 15% of your maximum voluntary contraction strength of your gluteus, for example, to walk. So that's only really equates to strength throughout. Out of five, it's just anti-gravity.
Strength is enough for walking in on flat, even ground at a normal pace. So running is where you need all that reserve force. That's when you really do need your quads and your glutes to be functioning. So kids with cerebral palsy might just be able to walk but can't do anything. I can't run, for example, because that just takes way too much muscle strength.
We do sometimes do get runners in that gait lab, but it is fairly rare, so I'm not going to say too much more about running. Next question can you explain crouch gait? Yes, I can explain gait, right? Let's just go back to this lad because it's not far off. This chap on his was his OK. So crouch gait is quite a malignant gait pattern, and there's usually three things wrong during crouch gait.
The hip is too flexed, the knee is too flexed and the ankle is flexed. Now the interesting thing about this chap is if you've seen the videos already, actually, to be fair, it was just like it was this slide here. Someone should have unmute themselves and shouted at me, all right, never mind. So this chap, so just going back to crouch gait because it's quite important, not just repeat myself a little bit.
So this chap that we saw before. So midfoot break, so forefoot in contact with the ground hind foot knots, that's that rubber crowbar. He hasn't got a rigid foot. So even though his heels lifting is forfeits in contact with the ground reaction back to behind the knee knee flexion moment here. And if you trace that up, new source, it would be in front of the hips and knee flexing, hip flexing moment.
Look at the graphs. We've got a hip flexing moment, double or triple normal. And look at his knee graph and we've got negras massive knee flexing moment where it should be an extending moment. So this is crap. This is crouch gait in a nutshell. Knee flexion, hip flexion, ankle Dorset flexion. Although in his case, it's not ankle dorsiflexion midfoot. Dorsal flexion is midfoot is broken, it's failing.
And that will get worse and worse and worse with time. Quads will get weak, knee will bend more, movement gets bigger, quads up to work even harder, and you get this vicious circle of progressive knee flexion until eventually you can't stand. Can't stand anymore. So I'm really sorry. I forgot I served yakking on about crouch gait without sharing my screen, but I think that hopefully you've got the gist.
Let me go back to the Zoom thing. We can see how it's a bit of a blur. Can you hear us, by the way, steve? I can't hear you, David. I can see that you're talking, David, but I can't hear you. A system. Oh, maybe they can hold on. So can you, David, can you stick your hand up if you can hear me?
Yeah, I can hear you. I can hear you. If I accidentally muted the audio. David, say something. Hello oh, that's better. Oh shit, I must, I must have. I must have muted my audio, so I literally couldn't hear you or see you.
What it. All right. Never mind. OK, so let's get it done that. Yeah, common gates in clinical relevance. So, yeah, so common. So the common gates you're going to get in your exam. And Teldrick is probably the commonest so short and shortened stance phase.
Then you might see Trump, Trendelenburg and I don't think I need to explain that to you because you all know what an antalgic gait looks like. So someone is trying to get their weight off the affected sides of shortens that stance phase on that side. And I think you all know what a Trendelenburg gait looks like to think, oh, this is a fantastic question. So Trump may not work for crouch gates.
So right? Let's just I'm going to share my screen again before I forget otherwise. So let's go back to this. So this is why this is used to be called iatrogenic. So let's go back to this chap here because he's quite a good example of this. So let's just go to initial contact. OK, so initial contact, so initial contacts there was the fault is with the four-foot and its heel just transiently, transiently hits the ground.
The only thing now at this stage that's going to try and keep that ground better in front of the knee is gastric pulling like crazy, effectively retarding the forward progress of your tibia? Keeping that ground reaction better in front of me and causing the extension? So initially, a tiptoe walking gait is an adaptive response. OK, so imagine if he had a flat footed gait. The origin of the ground reaction vector.
Let's get back of three Mason we can go forward a bit. So initial contact with the foot, right? OK, so at this stage, in the normal gait cycle, it should be a heel strike. OK, and then coming down to the origin of the ground reaction vector in normal gait will be dat back here somewhere. At this point, the gait cycle going up that way. That's a spin on a traject. So because of his because he can't straighten his knee, a adaptive response to early crouch gait is to go up onto your toes.
And that's to try and get the origin of your ground as forward as possible, so you can see at this point here is just going through maybe just in front of the news that is helping initially to keep in front of his knee. Now he fails because he's got that midfoot brakes who just kind of collapses. But the initial toe walking gait, if you've got crouch, is a protective response.
It's part it's almost like exaggerating your plan to flexion the extension couple. I remember we said the plant effectors is what's extending your knee. So by going up onto tiptoes, it's exaggerating that response. It's getting your ground reaction going to as forward as possible. So if I then as a surgeon, go, oh, wait a second, this kid's walking on his toes and go and cut their Achilles tendons, I've just put them into iatrogenic crouch, so I've just now taken away their adaptive response.
And it's a bit like this. This chap here, he hasn't. He hasn't got his Achilles cut, but he's broken at the midfoot. So I've taken away their adaptive response and put them into iatrogenic count. So it's incredibly important in early crouch gait. If you see a toe Walker to find out whether or not that's a genuine severe tightness, or whether it's due to early crouch gait, and you need a careful clinical examination, so you need to do silver skull test to see what that genuine range of motion is at the ankle and some of these kids that go up onto their tiptoes, they've got a fantastic range of ankle motion.
When you examine them clinically, they haven't got any tightness or spasticity, but you examine their quads and they've got quads, so they've got a hip flexion contract or an early knee flexion contract. And then in those ones, if you cut the Achilles tendon, you take away their adaptive response and you put them into crouch, get the so-called iatrogenic couch.
And it was done quite a lot by orthopedic surgeon in days of yore before we had gait analysis, and we really understood this concept. So you've got to be careful with cutting people's Achilles tendons. You've got to make sure you're doing it for the right reasons. Now, lots of kids do have genuine tightness and Achilles tendon contraction, and for them, releasing their gastritis or muscle lengthening or tendon lengthening is the right thing to do.
You've got to be sure, and that's what gait analysis is useful for what you're looking for. Crutch, gait, we've done that. The lengthening the length of questions are about AFO. So can you explain the biomechanical basis of an AFO in different pathological gates? Yeah OK, so there are a number. Afo is a complicated so another statistics. 3 is a three year degree.
You're not expected to details of ankle, foot or so since you are expected to know some principles. And there are lots of different types of and good Porthos is the commonest ones in cerebral palsy or gait improvement are a fixed ankle AFO and literally just a rigid device that goes behind the ankle below the knee and behind the ankle and down the foot, and it goes around the back.
And that's the kind of simplest type of ankle. For those poses. And the idea is, and remember, we talked about this plantar flexion, the extension couple. So we go to share my story. Let's Zoom on. I should just keep as my screen sharing names. All right, so let's talk, let's look at this guy with his AFO.
So he's got an answer for his efforts was the one with his iPhone, but it was not on the a-list line. So he's got a fairly standard his AFO from where you look at it as a posterior shell goes inside the shoe and it's got a shoe on top with a rocker, solid rocker soul on it. And as a general rule of thumb affairs and footwear are prescribed in combination, so you don't really prescribe one without the other, except in the most simple terms, aren't it?
And a lot of it is about controlling the punter flexion, the extension couple. So in his case, we've just prescribed that AFO to control his ankle movement to stop that midfoot break. So he's got a rigid AFO. It's got if you saw it in a distal trim lines going in front of the mattioli, he's got a double laminate sole plate, so his sole is absolutely rigid.
From there, all that dorsiflexion there is happening through the rocket rocker sole that we provided him. So it's a rigid afo, so we've now taken away his ankle movement. We're controlling it for him and tuning of these. lot of this is about setting up the angle here so you can put little wedges in. You can set the angle of the ankle in the air so the ankle of the bench, ankle and so forth, so you can set various angles to try and tune it.
And we tune those in the lab to get it. Get it right. So that's the simplest type of AFFO someone mentioned in the chat about gyros, a ground reaction, authorities. So this is kind of a next step up for crouch gait. So if you've got someone who's cramped can't be controlled with a simple afo, the next thing you tend to prescribe as a ground reaction. So you guys will have seen them.
They've got a front shell, so they've got a rigid thing around the front as well as the back is usually that kind of Clamshell design, so you bring it over and then the straps to hold it in place. And this is now an even more rigid way of stopping that tibia falling forwards. So to try and keep the tibia back during stance phase, that's in barefoot. So effectively, you've got a front shell here push that tibia back, getting that knee straight, getting that ground reaction back to start going in front of the knee.
But if you think about it, you can only push on the, you know, this is the pretibial area, but bone right under there. You only push on there so hard before you'll start causing pain and discomfort, and then you are limited to how hard you can push on the skin. So eventually, people with grouch often becomes indispensable. But ground reaction both doses is kind of the next step up after an AFO predominantly for crouch gait.
So this chap, for example, if that AFO wasn't so, so effective, then grow would be the next thing. And he's only young that he's new 9 or 10. As he grows in the next three or four years, he's going to go through puberty. He's going to get a lot heavier. And you can imagine that then no longer becoming sufficient, that strap will just give up. The Velcro will, will, will, won't be sufficient.
And then a group may actually well be well, be required for him. So AFO and the next type is hinged hinge splints. So these are often prescribed in prescribed in cerebral palsy because we normally need to take over the patient's ankle movement. But they are sometimes prescribed for things like these, like our foot drop frame, for example. So a foot drop splint, you want to stop the foot plantar flexing and swing phase, but you want to still allow it to Dorset legs.
See the different ways of doing it kind of hinges here. You can have what's called a leaf spring, so you have the cutaways behind the early, so it allows it to allows it to move. You can also, if patients don't have a midfoot break, you don't have to have quite have quite a rigid sole plate. You can just have a single laminate sole plate and so forth. So there's lots of different options.
And again, you aren't you guys aren't orthotics and you're not expected to be orthotics. And when we do our gait, when we do our tuning in the gait lab, we have just there. I don't know enough and I do this all the time. I don't know enough to the intricacies of all the different materials, all the different designs, all the different sort of tuning options you can have. It's not just tuning in the sagittal plane, but posting and so forth, the tuning, the coronal plane and all sorts of things that the arthritis can do.
And you're not really expected to know that. Remember, there was the quote for the exam your test is a day one consultant in the generality of the specialty. Detailed knowledge of orthotics is not required, just general principles. By any other questions, David, I think you actually answered all the other question, both of them were about a race in the spring.
Spring one, as you said, we're not expected to know that in that much detail as we're not all egawa test. And it is, as you showed, it's a multi-disciplinary approach because you're there working with your egawa test. And that's often the case with a lot of subspecialties. We we have to work with our other colleagues and all to get the right solution. I think that's the key thing to stake in the exam.
So I think knowing some things they can and can't do is helpful. So as a general rule of thumb, if by the time you start getting fixed contracts, you need 60 more than 10 degrees. There's almost no point in prescribing orthotics to try and improve knee movement because because, you know, just fixed, you can't know what it's going to be able to suddenly straighten a fixed flexion contract.
And then I suppose the other thing to just be aware of is the accommodative orthotics. So sometimes when your foot is so bad or your knee is so bad, you kind of building this splint around the patient's own different fixed deformities. So we've got some kids with their really bad feet that aren't really candidates for surgery, but you just want to give them a stable platform to walk on, walk on.
So we give them a generally an accommodative affair. We build a splint around the foot and then make a special soul so that the foot is then to the sole of this shoe is flat to the ground, even though the foot inside the shoe might be in sort of profound doesn't acquire. And so forth. So the kind of a to is just to try and make life easier. We're not trying to correct anything.
We're not tuning it in the lab to get ground reaction vectors in the right place or anything like that, but just trying to make the patient's life a little bit easier. So I suppose an accommodative versus a corrective AFO might be another sort of general principle if it's only. Um, let me think one question from is, how often do you recommend tenodesis for children with cerebral palsy?
So I do it all the time because I've got a great lab and I enjoy it, so I don't. It's difficult to. OK, so let's talk about a bit of other NIPE talk about this. It's horrible, but all the drawbacks of data analysis, there are lots of drawbacks of data analysis. So like I said, we don't really understand how humans work. So all the interpretation we do sounds very clever, but we're operating from quite a poor general knowledge point of view.
So the interpretation of gait analysis is really quite different. There's a lovely study done in Toronto where they looked at gait analysis from lots of different laboratories. So the same gait data, same video sent to different laboratories, and they come up with different, different conclusions, different recommendations.
They also did quite a nice study. This was a McMaster again in Canada, where they looked at. So they looked at people. They showed they randomized trials. So they showed some surgeons. Sorry, no. So they randomized people to the surgeon can see all of the patient's gait data, or the surgeon could only see the video and then obviously recommendations made and they found lots of differences there as well.
Then they did another one. This wasn't. This was a North American study where they showed the same. They did an intra observer reliability to the same surgeon. So the same data data data six months apart. And it was and they get different interpretations. Different labs have different normal, normal data sets. So it's not.
Unfortunately, it's not standardized like an MRI. So generally speaking, an MRI is the same as a CT scan is the same more or less as if you do it in one hospital. There's another gait analysis isn't different. Different labs have different setups, different models. The musculoskeletal model we use is different to some other labs use. Some use treadmills, for example.
Others use. Others use gait labs like we've got. Some use inertial measurement units. These are basically things you strap onto the muscles without 3-d, without motion capture. There there's lots of problems with the variability of how gait analysis is done and how it's interpreted, which makes customized recommendations of how it should be used difficult. However, there are some general principles and certainly in slap surgery.
If you're proposing level surgery, there are very, very few people that I around the country who will be happy to do that without gait analysis. Also from monitoring responses, it really is the only objective way of measuring gait. So if I do an intervention in cerebral palsy, whether it's Botox or orthotics or surgery, one of the best ways I can find out if it's made any difference is gait analysis.
So I use it sort of preoperatively for decision making and then post-operatively to monitor outcomes. And I use it a lot because I've got a date lab and I'm interested other people might use it less, but there are no absolute indications. But the closest I can get to an absolute indication is single event, multi-level surgery and stupid. And a few sources, straightforward ones, I hope so.
Do we always need few modifications for AFO and Graf and gruffalo splints? Mostly so certainly if you are, if you are using a rigid AFO where you're effectively taking away the patient's own ankle movement or foot movement, then it's a bit like having an ankle fusion. And if you give someone an ankle fusion, you need to change their shoe, particularly providing some kind of rocker.
And there's lots and lots of different rockers you can appoint loading rockers. You can have rounded rockers. You can choose the part of the foot that the rocker occurs in. You can even have rockers in front of the forefoot if you like, without without, with flare UPS and so forth. So, yeah, so generally speaking, if you're prescribing an AFO that takes away the patient's own ankle movement, then you need to prescribe a shoe to go with it.
Otherwise, they're not. If they just buy an off the shelf, trainer is not going to work very well. So the vast majority of our patients get AFO footwear combination AFO FC. OK and can a simple AFO work for idiopathic walkers, or is it just effective for crouch or jump the gate? So that's a really good question, actually. So idiopathic toe walking is a difficult topic.
So if you look carefully enough, probably up to 70% 0 of patients you've labeled as idiopathic walking's do have some pathology, and it's usually a very mild cerebral palsy or something like that. However, I would strongly advise you not to go hunting for it. If you've got a kid who's effectively functionally normal but just walks on their toes. You're going hunting for cerebral palsy or any other thing is probably not really going to help their life.
So it's not really beneficial for insurance or future job prospects. So if you've got cerebral palsy in your notes, particularly if it has really no meaningful effect on you. So first thing things is a lot of idiopathic walkers aren't idiopathic. Let's say about idiopathic. Tobruk is probably their best left alone as much as possible. You know, physiotherapy might be helpful.
Teaching them a few ankle 2 reflecting exercises and so forth might be useful. Serial castings sometimes you can do it for 4 to six weeks, just gradually stretching them out, particularly when they go through growth spurts. But actually, if you put a kid who's functionally normal into an affair, you'll make them worse. And then also, if you think about it, if you take again, take a kid who's neurotypical and you put them in a rigid airflow.
Not only does that control the sagittal plane, also the coronal plane, so it means you're taking away their own proprioception, you're taking away the ability for their ankle to develop, particularly at the young years. So I'm very, very against using avos Willy nilly. It's original air is like ankle fusion. I could well, it's like almost like an entire pan subtalar fusion.
You're taking away everything from the home foot, not only in the plane but also in the corona plane. And so, yeah, be very, very careful now. If you're really struggling and you've got a really bad toe walk and then maybe some kind of hinged leaf spring airflow to allow them to move. I would try and not. And if they're really bad, that if they're so bad, that's such high up on a tip toe, then it probably should go looking for another diagnosis, refer them to a developmental pediatrician or something like that, something like that, because often a lot of them aren't.
OK and I think last one of only a type of pathologies where you found gait lab analysis useful. OK, yes, a couple so in the adult world, so we've used it a few times now in Parkinson's and stroke. So gait velocity is quite a good predictor of severity of Parkinson's disease. Typical slow shuffling gait. You can actually use that to quantify the severity and response to treatment.
We've used it in diabetics, particularly in diabetic feet, where the patients don't have their own sensations. So getting their orthotics tuned properly, particularly with plans of pressures and foot pressures. So we can use the aponta pressure plate, which we've got in our lab to see where patients see where the patients stand on it, and it gives you a pressure map of the sole of the foot.
And so these patients don't have any of their own sensations. So we can say actually put all the pressure is over the lateral base of fifth metatarsal, something like that. And then the other disk can go away and make a total contact orthotic or something like that to try and account for that. Used it to the things like that. The other thing we've used it for more in the research concept is in hip and knee replacement.
So we've got a guy called Andy Metcalf who's got an interest in his knee surgeon by trade academic knee surgeon, but also got a history of Game of working gait maps. So we've used it. We're trying to develop models of how the knee works, so we can obviously indicate that we can model the knee in 3 planes at 100 frames a second and see really what the knee is doing during stance phase pre and post knee replacements.
So stuff like that, that's more of a research context rather than a general use. And then the other time is in foot and ankle surgery, particularly particularly people perfusion. So trying to work out what orthotics are best for best for them? So again, it's somewhat niche and it depends on your access. So if you've got an if you've got a gait lab in your hospital and you've got someone who's interested, then go and chat to them.
There's all sorts of other avenues. And as I said before, gait analysis is one of the only objective ways of measuring gait. And so if you're doing most of what we do in orthopedics, certainly lower limb orthopedics affects gait and we're hoping to make people walk better. And if you want to show that definitively, then gait analysis can help with that. So yes, if you've got research ideas and so forth and speak to your local gait, that.
Fantastic thank you very much, sir.
Segment:0 .
The I want to welcome everyone today. It's a very warm July day, and we're going to have a talk today by Mr. Stephen Cook from University hospitals, Coventry and Warwickshire. Who's going to talk to us about the gait cycle? Now, just a few things beforehand. I will just want to mention about another course that's coming up.
That would be. On the 28th of August, case discussions for your orthopedic exam just to get whether the advent of the sort of novel clinical stations being virtual, we're trying to get a few more courses where people can have a chance to practice going through how you go for a case based discussions. So hopefully this will be helpful towards the clinical parts of the exam.
And there's, of course, being run through the orthopedic Academy on the 28th of August. OK, we just stop shared. Right and just to. A few words to say about Mr. cook. So he's trained in Edinburgh and have been working as a consultant at Coventry hospitals since 2011.
And in the pediatric department with special interest in cerebral palsy and has been running a gait lab at GW for some time, I was very lucky when I was doing my pediatric fellowship to work with Mr Cook and the valuable experience. He explained the cycle very well. I just wish I'd had the chance to use it in the exam. Unfortunately, didn't ask me about it. He also has been the National vitiligo trainer of the year in 2012.
I took forever to do, I'll pass it on to Mr Cook. OK um, Thanks very much, David. That was a very generous introduction, so and and Thanks for inviting me to chat to you guys. So as David said, that my main subspecialty interest is cerebral palsy, and as part of that, as most of you are aware, gait analysis forms a fairly integral part. So I've designed this talk in sort of two or three sections. The first pictures, a little bit of fun, really just background of gait and a little bit about why I find it so interesting.
And then we'll get into the nitty gritty about the gait cycle, and then we'll hopefully end on a bunch of cases. You guys get used to talking about gates, particularly for the exam, but also it's useful for your practice in the long term. All right. So bipedal walking is actually surprisingly recent. So it's been a couple of million years or so since by Peter walking started.
And compare that with quadrupedal walking, which is sort of like nearly $460 million years ago was the first quadruped on land. So there have been some evolutionary adaptations to our anatomy and physiology to allow for bipedal walking, but it's nowhere near as well adapted as quadrupedal walking. And these are a few of them. So we have a wider pelvis. We have much longer lower limb bones, great, great and deeper arms.
They're thicker and knee joints in particular are much thicker. Same with ankles. And we've got adapted feet and so forth to accommodate it. However, there are some things that are particularly unusual. So in order for us to walk upright, if we didn't have this large thoracic kyphosis, all of our organs and heavy bits would be too far forwards or center of mass would be too far forwards, and we'd be constantly toppling forwards or using muscles to keep ourselves erect.
So we've developed this big thoracic kyphosis to keep the chest back and keep the center of mass over the hips. But then, because that's got a kyphosis, you then need to have a lower doses in your neck and the lower doses in your lumbar spine. And this is probably the origin of most back pain problems in humans. Now compare that to a great ape that's just got this die straight back from head to coccyx completely straight.
So that's how you would design it back if you could. But because we now work on all fours, we've got these adaptive adaptations. So some are good, like the big legs and the big knees and the long muscles and the long lever arms. Some aren't so good like that. The three curves we've now got in our spine, but also some non skeletal adaptations. So our muscles, particularly our lower limb and our anti-gravity muscles, are much stronger.
The muscle composite composition is different. So whereas great apes got a much more higher percentage of fast twitch fibers for explosive power, we've got a lot more of the sort of slow twitch fibers for strength and endurance, and we've also got a number of neurological changes to allow this to work. Um, we're also incredibly good at it, takes a baby around about a year to walk and buy around about age six to eight.
We work like adults. We can run, hop, skip, jump. We can climb up and down things. We can go with just about any terrain and we can do it for ages. We can walk and walk and walk. But we don't really know how it works. There's a surprisingly little amount we know. So this is the stuff we do know, we know about the anatomy.
We know every bone is. We know wherever we joint is. We know where every muscle is. I know the knee surgeons come up with a new structure and the posture or posterolateral corner every year. But generally speaking, we know where everything is. We know where the nerves are. We know where the muscles and tendons are.
We know how these things work in fairly intimate, intimate detail. And we've actually got some fairly good models of how human humans work, and it's the so-called double inverted pendulum. So that's a pendulum. That's an inverted pendulum. There's a double pendulum and there's a double inverted pension.
This is your foot down here, your knee, your hip, and then obviously got head arms above that. So actually, we're not a double pigeon, we're a triple pendulum. And so this is a triple pendulum in action. And one of the things to notice is how chaotic the movement of the points below the single pendulum are. So the single pendulum arc is utterly predictable as a mathematical equation that would describe that with perfect precision and any point of time in the future.
You know exactly where that's going to be. But now, if you look at the absolutely crazy movement, particularly of the little bottom ball on the right hand, it just goes all over the shop. It's inherently chaotic. Chaos isn't random. We'll talk about that in a second, but it is very, very, very hard to predict. And that is that we're not just a normal pendant with an inverted pendulum, and it's more complicated than that.
So this model, for example, models the head, arms and trunk is a single bar, but we're not as fine moves, our arms move, our head moves on our neck. This is obviously a sagittal plane. And this equation up here on the top right is just the equation of State for the movement at the ankle. And that's only in two planes. That's only in the sagittal only one plane so of to plane.
We haven't even thought about coronal or axial planes yet, so it's insanely complex. And remember, chaos isn't random. Chaos is a deterministic system system, but where arbitrarily small perturbations lead to great, huge, huge differences in the eventual outcome. So just go back to that triple pendulum model. You can change the initial state of the pendulum by orders of the width of an atom, and it will have a magnet, a large effect on the movement of the distal part.
So it is deterministic but very unpredictable. There are some quite I said, these are some quite good models of how things work. Most of you will be familiar with azimo, the Honda model. They've kind of retired that now and more recently, this dude Atlas Boston Dynamics and these robots can do phenomenal things. This thing can run.
It can jump. It can do all sorts of acrobatics. It can get up. If if it's knocked over, it can do all sorts of quite cool things and you sort of think, all right, we must we must have sorted how we want them, because if we can make something that does this and surely we know must know everything about walking, there's lots and lots of problems.
And the big problem is we just don't know how the control mechanism works in humans. We don't know how all everything everything puts is put together. And this is just a given illustration of why we don't know why it's so complicated. So in medical school, we're taught that muscles can effectively pull and they're kind of on or off.
But muscles are much, much more complex than that. So let's take the gas drop, which is a fascinating muscle so originates above the knee on the back of the femur passes behind the knee. It's got a muscular portion. It's got a neurotic portion. It's egawa neurosis, then turns into a tendon which inserts onto the tendon or the aponeurosis of another completely different muscle.
Then it goes down and performs the conjoined Achilles tendon, which then passes behind the ankle joint and behind the subtalar joint before it inserts into the calcaneus. So this muscles got incredibly complex anatomical arrangement crossing three joints. It's got two different parts medial and lateral on each of those parts can be activated in a myriad of different ways.
You can activate it with incredible precision. One of the quite cool things to do. So if those of you who drive next time you go for a drive, please make sure there is no one behind you. But try breaking with your left foot compared to your right. It's really, really hard to do. So you've trained your gas stroke over the years to answer Yes. To a certain extent, it's to provide a perfect, really exquisite control over the pressure it can do.
That's how it works during walking. So the muscle isn't just on or off. Different parts of it can be on or off. Different parts of it can activate at different rates. Different fibers within the muscle can be activate activated at different times. And this is one of the things I'll hopefully try and convince you all how this works by the end of the teaching session, even though this muscle passes behind me.
So you think it should flex it? It is one of the most potent extenders during gait. And that's part, and it's mainly because of momentum, the ground reaction vector and the fact, it depends upon the state of the other joints it passes and the other muscles. So I'm going to go over that again, because that's really, really important towards the end. It's also mind numbingly any energy efficient and just to illustrate this.
Humans take around about two, 2 and 1/2 joules per kilogram per meter of walking. So if you take an 80 kilo person, I pick that because that's roughly what Atlas robot weighs weighs a little bit more, actually. So you take an 18 80kg person walking it about standard walking pace. We use around about a millijoules an hour, whereas Atlas uses over 13 millijoules for the same hour of walking.
So it's about it's over an order of magnitude more efficient as human walking, so around about 15 times more efficient. And again, just to put that into a sort of real-world example, imagine those of you who have Teslas about 300 miles per charge. So if Tesla's batteries were as efficient as humans, you'd go 5,000 miles on a charge. There's a big Gulf in understanding between sort of robotic walking, if you like in human walking.
This is what our lab looks like. So it's a long, thin room with a bunch of motion detecting cameras around the ceiling, some force plates in the middle that measure the ground reaction force. This is my son, Harry, all when we were opening up the lab, we had to get a bunch of inverted commas, normal patients in the lab to walk around and provide our normal data set.
So he's got a number of markers which are placed on the bony prominences, and these are placed in very specific ways. It takes our therapists quite a while to learn exactly how to put these markers on and where to put them. Because if you think about it, we're trying to build a skeletal model based upon the skin, and so we have to put these on in the right place.
There are some places that easy. Like ASIS and easy to find them that easy to find that it may be a natural ally. Much harder, actually to find the center of the new joints, particularly on the lateral. So it it isn't easy to do, but that and that's one of the drawbacks I think of getting as this is getting the markers on in the right place. But anyway, that's what we do.
And then we get them walking up and down the laps. So we just found out this works better, actually if I'm not in presentation mode. All right. So this is Harry walking up and down the lab. And you can see he's got a bunch of markers on the little Black boxes that you see. If I pause it, these are surface emg, so we can pick up very crude just on the flexor and extensor compartments so we can pick up a bit of EMG data as well.
We walk up and down the lap. Then next thing you want to do is pick up the ground reaction force. So this is Newton's third law in action. So Newton's third law, every action has an equal and opposite reaction. So as Harry walks across the lab, if I do to say mid stance here, this arrow is his ground reaction force.
The way it's set up in the lab is that the size of the arrow is the magnitude of the force. Remember, a force is a vector, so that that's the size. And obviously the direction of the arrow is the direction of the force, and you can see how it moves throughout the gait cycle from initial contact through to towel off. And if you think don't think like a surgeon for a bit, just think like a physicist or an engineer, it's this force that is responsible for the external moments around your legs.
So this force times the distance there is at the moment around the need. This force times the distance there is the moment around the ankle. If you chase that up towards the hip, that's the moment there. So this data. This ground reaction force is what's allowing us allowing the computer to calculate the moments.
And from that, we can also calculate the power. So this is going through it. So I'm just going spend a little bit of time on this bit, just going through the bits of the gait cycle. So you've got initial contact, initial contact is a point in time and the initial contact should be with the heel. So you can see how he's got a normal heel strike then. You've got low response, the knee bending and the foot becoming flat.
So it's very, very quick. This is 25 frames a second, so literally only got two frames between heel strike and foot flat. So it's very, very, very, very quick. And this is a so-called first rocker in terms of ankle movement, or it's called load response in terms of the gait cycle. It's also called first double support because it's got you've got both feet on the ground.
And at this point here your ankle, your foot is allowed to contact to the ground in a controlled way under the eccentric control of TBE n.s.a. and toe extensive. So this EMG here will be firing like crazy as Harry's tabun is firing eccentrically, allowing the foot to hit the ground in a controlled way. Without that, you get kind of a foot slapping.
I've unmuted myself somewhat, said the host muted me, somewhat muted me anyway, I hope that wasn't personal. Maybe, maybe, maybe the claw palsy shit so far and they decided, that's it. Anyway, assuming I'm unmuted now, I'll carry on someone. Please tell me if they can't hear. All right. So first rocket or load response, then, as the foot is now flat on the ground.
And obviously as the foot's flat, the tibia is advancing across the foot and so the foot, the ankle is also flexing. So from that point there to that point where the ankle is dorsal flexing. And the ankle is Dorsey flexing in a controlled way? We don't want this to happen too quickly because otherwise you can get all sorts of great problems. So gastroc here now is Tim and is now turned off and conciliate are now firing so this EMG would be starting to register a response and again, it's eccentrics at gas rock is contracting, contracting, contracting.
Loading up that Achilles tendon look at Harry's Achilles tendon is under a lot of tension. They're building up all that elastic potential energy, preventing the tibia, folding forward to rapidly and at this point, near. So look, look here. So at this point here, the ground reaction vector is behind me, but at this point here, it's now in front of the knee, and that's now causing it extending moment.
I'm going to go through this again because this is really important. The knee is now extending. That's happening passively. Just to this point here, so let's go over that again, so foot flat ankle is now Dorsey flexing, just rock is contracting like crazy to prevent there to be a moving forward to fast ground reaction, vector moves through the center and then in front of the knee.
Knee starts extending to this point here. And you can just see it now. The origin of the ground reaction vector right at the front, right up between first and fifth metatarsal head. All of Harry's weight now is through the forefoot. The heel is just about to lift off, lift off the ground and then you get this explosive plunger flexion of the ankle to push the limb forwards.
All the textbooks say this is concentric contraction of your saliers, and you should say that in the exam because all the examiners believe that too. But actually, this is actually mostly passive in normal, working at normal speed, partly because during this phase of gait cycle, you're building up, the elasticity in your gas, in your Achilles tendon. And actually in this at this point here in normal, working at normal speed, not running, not jumping, it's just elastic.
Recall that causes that frontal of flexion and the forward propulsion that's actually isn't very isn't very active there. But generally speaking, the textbooks third rocker or the end or terminal stance pretty swing is concentric contraction of your that pushes that leg forward for swing phase, so you don't really need your hip flexors much in swing phase, it's just all propulsion from the gastric.
Right so I'm going to go through this again. Let's just go to slap presentation, which this is just a little word about how the ground reaction, how one of the ways you can think about the ground reaction better. So imagine this leg of this person's leg would just suspended in the air if I push on the little foot in that direction. I think you'll all agree that's going to extend the knee.
So if I push that way and he's going to straighten and the magnitude of the moment is the force, whatever that force is, times the perpendicular distance. So not this distance and not that distance there, the perpendicular distance to the center of rotation of the knee. So force times, distance moment Newton meters. And as long as that arrow is in front of the knee, it will always try and straighten.
It doesn't even matter how close it would get. Obviously, that distance is much less so that force times distance is much, much less than movement is less, but that's still an extending moment. So if I push on the foot in that direction, it will try and straighten the knee. Not as much as if I pushed on it with in that direction, but it's still going to straighten the knee.
And as soon as that ground reaction vector goes behind the knee, it becomes a flexing moment. And now Harry or whoever's white bag, if you stand like that, that's a flexing moment, and it's that force times that distance. OK, so ground reaction vector in front of the knee is an extending moment. Ground reaction vector behind the knee is a flexing moment. So this is where I'm going to try and convince you how Gus extends the knee, right?
So remember we said in second rocker, it's your gastrocnemius and your Soler's is firing like crazy to stop your tibia going forward. So if you've got momentum taking your body forwards but your tibia is being kept in check, then it stands to reason your knee is going to extend. And the way we can map that is by showing where the ground reaction vector. So look at Harry's knee at the end of load response, the knee is relatively bent around about 30 degrees or so.
The ground reaction vector at this point is behind the needs a flexing moment. So the only thing that's going to stop that flexing is quite so at this point. In load response, quads is active. It's surprisingly not active that much or anything around about 10% to 15% your maximum contraction of your quads in normal walking. But there is a little flicker of quads activity.
Then you get to this point here in. That mid stuns, so in mid starts now. Harry's ground reaction, but you're right through the center of the knees, there is no moment, there is zero moment because there is no distance. They can't be a moment if there's no distance. So at this point here. Knee flexion is now stopped. And as soon as I go one frame forwards, it's now an extending moment.
It's a tiny moment because that distance is very small, but it's an extending moment. And if I go through a few more frames, it gets a little bigger, a little bigger. Now watch what happens to Harry's knee. Knee flexion. Knee extension. Knee flexion. The extension?
Not because quads is extending. The knee quads is completely off. Now this is a normal gait. This EMG will be silent. This is an entirely due to the ground reaction vector being in front of the knee. And the only thing that controls that is your. So your gas stroke is extending your knee, even though the heart is behind your knee.
It's a potent knee extender, and this is something called the plantar flexion knee extension couple key couple. So your ankle plantar flexes that are controlling your knee extensively and it's incredibly important concept. And when we're prescribing orthotics. For gait improvement and tuning them, this is one of the primary things on. The first things I'm looking at is where is this line going during stance phase?
And I'll show you, I've got plenty of examples of pathological gait where that's been disordered plantar flexion, knee extension, couple mid stance to terminal stance knee is going from flexion to extension. Quadriceps is completely off. Gas stroke is firing, extending the knee right. If anyone doesn't understand that, put it in a question and we'll go over it again at the end.
This is one of the most important concepts when you're prescribing orthotics. All right, let's skip on a phase. So this is now the next phase of gait analysis. And now we've got Harry walking and we've got the ground reaction vector. The computer can build up a wire model and then we can dispense with Harry altogether. And now we've got the y model and the advantage of this.
I can't see on this because this is just a static video, but in the gait loud, we can rotate this around. We can look in any plane from top to bottom, side to side. There's an entirely computer representation of where those dots are, why those dots are. And from this, we can calculate joint ranges, moments, powers and all the other stuff that you'd have seen when you've seen gait graphs. So this is the raw data, if you like, but obviously we need to get that into a form that we can understand.
So let's just go to this, and you guys may have seen graphs like graphs like this, and this is how we present it in the lab. So on the left hand column, here you've got our kinematics. So this is just the movement of the joints and we've got various conventions. So in our lab, red is left, blue is right like the political spectrum, but other labs do it differently.
So you have to do a little bit careful. If you're in the exam, it will be labeled, you will be told which is which. Most almost all gait graphs I've ever seen have got a gray bar. This is our normal values and our laps remember to hurry through my lab. We had 20 kids to the lab of varying different ages and this is our normal. So you should in the exam, also get a normal, a normal bar.
And that's the gray bar. What normally happens? So that gives you a bit of a step up in terms of interpreting these graphs because you already know what's normal. And then, as I said, these are usually averages and then this is the kinematic, just the movement. These are our moments. These two sets of graphs are on the right hand side are the next two columns on the moment.
This is the kinetics. These are now the joint forces. And this is moment and this is power. So moment, as we said, you all know what moments are there force times perpendicular? This force times perpendicular distance. What most people don't understand, and I won't spend too long on it because I don't think it's important for the exam is what Power means.
So when we talk about power in orthopedics, we often talk about muscle strengthening. I've got power 3 out of five or power 4 out of five. That's not what we mean by power in gait analysis. This is true physical power joules per second watts. And those of you who are familiar with cars and so forth will know that the way you calculate the power output of a car is the talks at the moment multiplied by the angle of the turning speed of the crankshaft, and that's exactly the same in these graphs.
So it's your moment. So the magnitude of this graph multiplied by the angular velocity effect with the slope, the gradient of these graphs. So if I pick an area here where there is a large moment and a relatively fast rate of moment, you see a big large amount of power. Or if you take this graph, for example, this patients need barely moving at all. In stance.
Phase no movement zero gradient, 0 power. OK, so that's just a moment. This isn't strength. This is mechanical power. True mechanical power joules per second or what? They're normalized for weight. All right. So but we won't talk too much about powers powers because it's unlikely to come up in the example.
And then we can create some date reports which look very cool and we can send these to parents and physios and make recommendations on various different things, so that's kind of what we do in the lab. So this is a quick. How are we doing for time? 25 minutes. OK, so this is some pathological gait now. So this actually just go back.
Like I said, it works slightly better in this review. So this is a gentleman with cerebral palsy. I'll play it full speed. Start off with and you can see he's got this. So definitely something wrong with that foot, particularly the right side. So he's got deeply. It's asymmetrical to the right side's worth and there's left. There's a few things that we look at when we're trying to describe gait and in the exam and also in your clinical practice, when you don't have access to a gait lab, you're really going to only see gates do visual gait analysis.
Some of you might do a video, I suppose, but very few of you will actually go through and get 3D gait analysis. So the most of the rest of this talk is going to be generally about the visual interpretation of gait. And there's a few things that we look at, and I'm going to go through these a few times as well, because it kind of gives you a structure about how to look at gait.
So the first thing is initial contact. So let's do a right foot gait side, right foot gait cycle. So what hits the ground first? You can see on this case, actually, let's go to Sanjay tools for him. I think it's better. Let's go to a right. OK, let's go back a few. OK to do just spin on fight up note to fast.
Look good, all right, so no, no ground reaction to yet, and nothing's touch the ground and you can see that as soon as the ground, but actually that's initial contact, so initial contact in his cases with the forefoot. In fact, it's almost entirely with the fifth 3 four foot contact. And then it's been on. Now watch look at his look at his knee.
Remember, I showed you with Harry, my son when it got to mid stance, the ground reaction vector was through the middle of the knee. See with this chap his ground reaction, but it's always behind the knee, so that is causing a flexion moment. And the only thing that can stop the knee buckling is now his quads. This lad has already weak because of cerebral palsy, has to use his quadriceps to keep his knee straight during mid starts and even as dance progresses.
Flexion flexion flexing movement flexing movement never gets that ground reaction vector in front of the knee always stays behind it. So then for these person, we say the plantar flexion extension coupled is impaired or even in this case, absent. He cannot get his ground reaction vector in front of the knee and therefore cannot get that extending movement. And therefore, the only thing that's going to keep his knee straight is his quads, which is going to increase the energy expenditure it's going to pull on his patella, given that patella to stretch out his knee ligament, his patellar tendon.
If I ask any of you healthy individuals to stand or walk with your knees bent like this for a long period of time, you're going to get your quads, are going to stop burning, it's going to get really uncomfortable. And this kid's already weak because of his cerebral palsy. So this is what you mean by an absent punch flexion extension. A couple and the knee just stays bent, stays bent, stays bent and then carries on. So that's kind of.
And then if we look at his graph, let's go to this one. So look at this, so this is his new flexing moment, so we can we've just shown you on the video how he never gets the knee extension moment as the normal one. It just stays flexing and his knee is obviously there without the knee, extending moment can't extend. This is where they should go. They should go.
Your knees should go almost to full extension by mid stance and terminal stance. But in his case, they just stay bent. My statement? Now what's really interesting about this lad is that clinically so you examine him on the couch, his knees come fully straight. So this is not fixed flexion contractors. Each each grid line here is 10 degrees, that's 10, 20, 30, between 30 and 40 degrees.
This is not fixed knee flexion contracted on the couch, his knees fully extend. So why is this happening? Why is he getting? Why can't he do that? It's entirely because he cannot get his ground reaction vector in front of the knee. OK, so what do we do? So we come along and we prescribe them and orthotic.
And unfortunately, I don't have the overlay of this, but it's still fairly convincing. So now look at his let's get his right foot. So right foot initial contact. So now he gets a heel strike. Previously, his right foot, it was the forefoot. They hit the ground first, so he's now got a first rocket. Now watch what happens to his knee now. So now the neatest shorts get slightly away, but now the knees straight and straight and straight and straight and straight and straight and straight and straight and straight.
And so almost out to full extension at toe off. So we've taken him from being in a crouched position to getting his knees straight, and that's just because of the orthotic prescription. No surgery has happened here. No botox, nothing else. Just by controlling the punter flexion, the extension couple. This is an AFO with some wedging. He's got a little bit of a rocker on his.
It's also just by orthotics. We've transformed his gait. And so if you walk, watch him walk. Now is now watch that needs they need just extends really nicely during the stance phase now. Bang much more natural gait, definitely still abnormal, but completely different to this gait. And because now he doesn't need to use his quads is quadriceps muscles.
It will be much more energy efficient for him, so he doesn't need to now burn his quadriceps every time he stands. And it will hurt less because he's not pulling on his patellar tendon every time and causing patellofemoral pain. So that's how orthotics can be used, right? And some just got just to finish off this part of the chat. I've got just a few tips for the fastest thing.
So most examiners are not gait lab trained Peter Potts, who treat the kids with sleep. Most will be like a foot and ankle surgeon or a knee surgeon or hip surgeon, so you do have to play a little bit to your crowd. And if you see an obvious gait abnormality, then just say so. So if you see a tendon and bone gait or an antalgic gait or a short leg gait or a high stepping or the classical gait, just say so.
I don't think there's any necessity to go through the sort of details of gait analysis if it's a fairly obvious gait abnormality. But this is sorry. I'm telling me to finish. But if you do see a really obvious, if you don't see an obvious abnormality, then you do need a structure for how to visually describe someone's gait.
And this is how I would propose that you do it. So get used to watching a patient walk away from you and looking at their right hand side. So that's looking at their right hip, knee, foot and ankle, then get the patient to turn around and walk back towards you, but carry on looking at the right hand side from your point of view. So now you're looking at the patients, the left hand side, so you're watching their right leg as they walk away, watching their left leg as they walk back towards you.
But you're always looking to the right, see what hits the ground first. So initial contact is with the whatever it is. Then the next thing to look at is stability and stance phase, so are they are they wobbling from side to side? Do they need to use a stick or a cane? Or, God forbid, do they fall or have to use the wall? So what's the stability like in stance phase? Are they clearing and swing plays and there's two things you need to clear, you need to clear the floor and your other leg.
So is clearance adequate? Then is there is an order for you to progress through and what you have to have a step length and the step should be either normal, increased or reduced, some people try and dramatically increase their step length to make up for poor cadence. They effectively can't walk as many steps per minute, but take a longer steps. Most people with great problems actually have a reduced slap length.
They don't progress as much, and it is a judgment. You can't say definitely what's normal and only sort of say if you think, think it's really abnormal. And then so you can bring bill the epimysium into one sentence, you say, as they said, this patient's initial contacts were healed, which good stability and starts phase adequate clearance and swing, and there appears to be normal slap.
Then one sentence and you describe those four bits of the gait cycle. You needed that for each leg left and right. And then the last thing to comment on is something called energy conservation. So energy conservation is a somewhat nebulous term or it's not nebulous. It's actually physically defined in terms of oxygen consumption, but you can't do that in the visual analysis.
So you have to kind of just sort of cap it off with a statement of what you think the patient's energy energy expenditure of walking would be like. Generally speaking, the energy expenditure of walking is to accelerate your center of mass. You have to accelerate your center of mass forwards to progress anywhere. But you shouldn't really have to accelerate left, right or up and down or accelerations in forwards and backwards in the sort of transverse plane.
So if you do see big trunk sways from side to side or the patient's going hiking up and down, so they've got, you know, they've got a foot drop on the other side, step to lift their leg up high. Then you can sort of say, actually, there appears to be increased energy energy expenditure or reduced energy conservation. So just to go back, initial contact is with the field.
Usually, there is good stability in stance. Phase adequate clearance and swing increased at length and there appears to be good energy conservation. And that gives you something to say if you cannot obviously see an abnormal gait pattern. And it sounds intelligent. And certainly if you're speaking to someone who's used to looking at gates, it's kind of the sentence that I want to hear those five things.
So initial contact clearance and swing stability and sense energy conservation and statment, they're the kind of five things that you want to kind of bring into your gait discussion from visual gait analysis. All right. We'll get a chance to practice that when we do some of the questions. This is the next hop tip is just not to get too muddled with the gait phases.
There are lots of different ways of describing gait changes. Most gait labs and gait analysts use spaces Jacqueline Perry, who described these back in the 60s and 70s and their low response, mid stance, terminal stance pre-spring and then initial mid and terminal swing and generally speaking, low responses. Your first 10% and mid stance and terminal stance at 20% each. And then pretty swing is your last 10% each.
Dance phase and stance phase accounts for 60 to 62% of this cycle and then initial mid and terminal swing 13% for each of them. And that's your 40% of swing swing phase. So these are they're the phases that most analysts use. However, most of the time, certainly if you're doing foot and ankle clinical vivas or with a non gait surgeon, they talk about rockets. And we've kind of mentioned these already.
So you've got your first rocker, which is during maintenance, actually only the first half of the load response. And that's your ankle going from neutral to punter flexion eccentric contraction to your second rocker, which is a big chunk 40% This is your foot flat to the ground. We've got tibia advancing over the top to your ankle is dorsal flexing, eccentric contraction of gastric sleeve and then the third rocker pretty swing, which is your ankle plantar flexion concentric contraction of mattress sutures or elastic recoil.
But I probably just stick to concentric contraction and then swing phase initial mid and terminal just split into thirds. So these are kind of how a lot of sort of non gait analysis, all the parts will talk about things. And the other thing you might come across is double support, single support. So you've got first double support, which is load response and you've got both feet on the ground and first single support.
So that one, for instance, phase the other foot in swing phase, then you've got second level support. So this is in pretty swing. Two the end of stance phase for one limb and the other. The other limb is now in low response and then your second single support during swing phase. So sometimes you'll see these phases described double spot, single squat, double support, single support. And another way.
So there are different ways of describing gait, probably from your point of view in the exam. Most people, certainly non gait surgeons, none. Gait analysis of the pods will talk about the ankle rockers to describe the phases of stance stance phase. So again, play to play to your pediatric liver and you know it, then go to these. But I wouldn't spend too much time learning these unless you're particularly interested, right then.
So I'm going to I think I'm going to stop yakking there because that's most of the gait chat. So, David and honey, I don't know if there's been any questions so far. Let me just stop sharing. And no other questions, I can just tell in the chat group have their honey. No, no.
OK David, you are a muted. Only one question here. So what's happening in running? Yes I can't see I can't see a chapter, so I don't know, I can't see it that way. So what happens in running a store? Muted, I can't hear you. What's happening in running? You hear me?
Oh, wait a second. I've got the I've got the I've got the. OK, I see. So one question about running and one question about crouch gait. I'm going to slightly gloss over running. So it's not that it's not important. It's just I've never seen a game. I've never seen a question about running.
It is a very sort of specialist topic. One one of important things to remember is that for the normal walking, you need surprisingly little muscle, muscle strength. So all of the reserve you've got, so you'll need 15% of your maximum voluntary contraction strength of your gluteus, for example, to walk. So that's only really equates to strength throughout. Out of five, it's just anti-gravity.
Strength is enough for walking in on flat, even ground at a normal pace. So running is where you need all that reserve force. That's when you really do need your quads and your glutes to be functioning. So kids with cerebral palsy might just be able to walk but can't do anything. I can't run, for example, because that just takes way too much muscle strength.
We do sometimes do get runners in that gait lab, but it is fairly rare, so I'm not going to say too much more about running. Next question can you explain crouch gait? Yes, I can explain gait, right? Let's just go back to this lad because it's not far off. This chap on his was his OK. So crouch gait is quite a malignant gait pattern, and there's usually three things wrong during crouch gait.
The hip is too flexed, the knee is too flexed and the ankle is flexed. Now the interesting thing about this chap is if you've seen the videos already, actually, to be fair, it was just like it was this slide here. Someone should have unmute themselves and shouted at me, all right, never mind. So this chap, so just going back to crouch gait because it's quite important, not just repeat myself a little bit.
So this chap that we saw before. So midfoot break, so forefoot in contact with the ground hind foot knots, that's that rubber crowbar. He hasn't got a rigid foot. So even though his heels lifting is forfeits in contact with the ground reaction back to behind the knee knee flexion moment here. And if you trace that up, new source, it would be in front of the hips and knee flexing, hip flexing moment.
Look at the graphs. We've got a hip flexing moment, double or triple normal. And look at his knee graph and we've got negras massive knee flexing moment where it should be an extending moment. So this is crap. This is crouch gait in a nutshell. Knee flexion, hip flexion, ankle Dorset flexion. Although in his case, it's not ankle dorsiflexion midfoot. Dorsal flexion is midfoot is broken, it's failing.
And that will get worse and worse and worse with time. Quads will get weak, knee will bend more, movement gets bigger, quads up to work even harder, and you get this vicious circle of progressive knee flexion until eventually you can't stand. Can't stand anymore. So I'm really sorry. I forgot I served yakking on about crouch gait without sharing my screen, but I think that hopefully you've got the gist.
Let me go back to the Zoom thing. We can see how it's a bit of a blur. Can you hear us, by the way, steve? I can't hear you, David. I can see that you're talking, David, but I can't hear you. A system. Oh, maybe they can hold on. So can you, David, can you stick your hand up if you can hear me?
Yeah, I can hear you. I can hear you. If I accidentally muted the audio. David, say something. Hello oh, that's better. Oh shit, I must, I must have. I must have muted my audio, so I literally couldn't hear you or see you.
What it. All right. Never mind. OK, so let's get it done that. Yeah, common gates in clinical relevance. So, yeah, so common. So the common gates you're going to get in your exam. And Teldrick is probably the commonest so short and shortened stance phase.
Then you might see Trump, Trendelenburg and I don't think I need to explain that to you because you all know what an antalgic gait looks like. So someone is trying to get their weight off the affected sides of shortens that stance phase on that side. And I think you all know what a Trendelenburg gait looks like to think, oh, this is a fantastic question. So Trump may not work for crouch gates.
So right? Let's just I'm going to share my screen again before I forget otherwise. So let's go back to this. So this is why this is used to be called iatrogenic. So let's go back to this chap here because he's quite a good example of this. So let's just go to initial contact. OK, so initial contact, so initial contacts there was the fault is with the four-foot and its heel just transiently, transiently hits the ground.
The only thing now at this stage that's going to try and keep that ground better in front of the knee is gastric pulling like crazy, effectively retarding the forward progress of your tibia? Keeping that ground reaction better in front of me and causing the extension? So initially, a tiptoe walking gait is an adaptive response. OK, so imagine if he had a flat footed gait. The origin of the ground reaction vector.
Let's get back of three Mason we can go forward a bit. So initial contact with the foot, right? OK, so at this stage, in the normal gait cycle, it should be a heel strike. OK, and then coming down to the origin of the ground reaction vector in normal gait will be dat back here somewhere. At this point, the gait cycle going up that way. That's a spin on a traject. So because of his because he can't straighten his knee, a adaptive response to early crouch gait is to go up onto your toes.
And that's to try and get the origin of your ground as forward as possible, so you can see at this point here is just going through maybe just in front of the news that is helping initially to keep in front of his knee. Now he fails because he's got that midfoot brakes who just kind of collapses. But the initial toe walking gait, if you've got crouch, is a protective response.
It's part it's almost like exaggerating your plan to flexion the extension couple. I remember we said the plant effectors is what's extending your knee. So by going up onto tiptoes, it's exaggerating that response. It's getting your ground reaction going to as forward as possible. So if I then as a surgeon, go, oh, wait a second, this kid's walking on his toes and go and cut their Achilles tendons, I've just put them into iatrogenic crouch, so I've just now taken away their adaptive response.
And it's a bit like this. This chap here, he hasn't. He hasn't got his Achilles cut, but he's broken at the midfoot. So I've taken away their adaptive response and put them into iatrogenic count. So it's incredibly important in early crouch gait. If you see a toe Walker to find out whether or not that's a genuine severe tightness, or whether it's due to early crouch gait, and you need a careful clinical examination, so you need to do silver skull test to see what that genuine range of motion is at the ankle and some of these kids that go up onto their tiptoes, they've got a fantastic range of ankle motion.
When you examine them clinically, they haven't got any tightness or spasticity, but you examine their quads and they've got quads, so they've got a hip flexion contract or an early knee flexion contract. And then in those ones, if you cut the Achilles tendon, you take away their adaptive response and you put them into crouch, get the so-called iatrogenic couch.
And it was done quite a lot by orthopedic surgeon in days of yore before we had gait analysis, and we really understood this concept. So you've got to be careful with cutting people's Achilles tendons. You've got to make sure you're doing it for the right reasons. Now, lots of kids do have genuine tightness and Achilles tendon contraction, and for them, releasing their gastritis or muscle lengthening or tendon lengthening is the right thing to do.
You've got to be sure, and that's what gait analysis is useful for what you're looking for. Crutch, gait, we've done that. The lengthening the length of questions are about AFO. So can you explain the biomechanical basis of an AFO in different pathological gates? Yeah OK, so there are a number. Afo is a complicated so another statistics. 3 is a three year degree.
You're not expected to details of ankle, foot or so since you are expected to know some principles. And there are lots of different types of and good Porthos is the commonest ones in cerebral palsy or gait improvement are a fixed ankle AFO and literally just a rigid device that goes behind the ankle below the knee and behind the ankle and down the foot, and it goes around the back.
And that's the kind of simplest type of ankle. For those poses. And the idea is, and remember, we talked about this plantar flexion, the extension couple. So we go to share my story. Let's Zoom on. I should just keep as my screen sharing names. All right, so let's talk, let's look at this guy with his AFO.
So he's got an answer for his efforts was the one with his iPhone, but it was not on the a-list line. So he's got a fairly standard his AFO from where you look at it as a posterior shell goes inside the shoe and it's got a shoe on top with a rocker, solid rocker soul on it. And as a general rule of thumb affairs and footwear are prescribed in combination, so you don't really prescribe one without the other, except in the most simple terms, aren't it?
And a lot of it is about controlling the punter flexion, the extension couple. So in his case, we've just prescribed that AFO to control his ankle movement to stop that midfoot break. So he's got a rigid AFO. It's got if you saw it in a distal trim lines going in front of the mattioli, he's got a double laminate sole plate, so his sole is absolutely rigid.
From there, all that dorsiflexion there is happening through the rocket rocker sole that we provided him. So it's a rigid afo, so we've now taken away his ankle movement. We're controlling it for him and tuning of these. lot of this is about setting up the angle here so you can put little wedges in. You can set the angle of the ankle in the air so the ankle of the bench, ankle and so forth, so you can set various angles to try and tune it.
And we tune those in the lab to get it. Get it right. So that's the simplest type of AFFO someone mentioned in the chat about gyros, a ground reaction, authorities. So this is kind of a next step up for crouch gait. So if you've got someone who's cramped can't be controlled with a simple afo, the next thing you tend to prescribe as a ground reaction. So you guys will have seen them.
They've got a front shell, so they've got a rigid thing around the front as well as the back is usually that kind of Clamshell design, so you bring it over and then the straps to hold it in place. And this is now an even more rigid way of stopping that tibia falling forwards. So to try and keep the tibia back during stance phase, that's in barefoot. So effectively, you've got a front shell here push that tibia back, getting that knee straight, getting that ground reaction back to start going in front of the knee.
But if you think about it, you can only push on the, you know, this is the pretibial area, but bone right under there. You only push on there so hard before you'll start causing pain and discomfort, and then you are limited to how hard you can push on the skin. So eventually, people with grouch often becomes indispensable. But ground reaction both doses is kind of the next step up after an AFO predominantly for crouch gait.
So this chap, for example, if that AFO wasn't so, so effective, then grow would be the next thing. And he's only young that he's new 9 or 10. As he grows in the next three or four years, he's going to go through puberty. He's going to get a lot heavier. And you can imagine that then no longer becoming sufficient, that strap will just give up. The Velcro will, will, will, won't be sufficient.
And then a group may actually well be well, be required for him. So AFO and the next type is hinged hinge splints. So these are often prescribed in prescribed in cerebral palsy because we normally need to take over the patient's ankle movement. But they are sometimes prescribed for things like these, like our foot drop frame, for example. So a foot drop splint, you want to stop the foot plantar flexing and swing phase, but you want to still allow it to Dorset legs.
See the different ways of doing it kind of hinges here. You can have what's called a leaf spring, so you have the cutaways behind the early, so it allows it to allows it to move. You can also, if patients don't have a midfoot break, you don't have to have quite have quite a rigid sole plate. You can just have a single laminate sole plate and so forth. So there's lots of different options.
And again, you aren't you guys aren't orthotics and you're not expected to be orthotics. And when we do our gait, when we do our tuning in the gait lab, we have just there. I don't know enough and I do this all the time. I don't know enough to the intricacies of all the different materials, all the different designs, all the different sort of tuning options you can have. It's not just tuning in the sagittal plane, but posting and so forth, the tuning, the coronal plane and all sorts of things that the arthritis can do.
And you're not really expected to know that. Remember, there was the quote for the exam your test is a day one consultant in the generality of the specialty. Detailed knowledge of orthotics is not required, just general principles. By any other questions, David, I think you actually answered all the other question, both of them were about a race in the spring.
Spring one, as you said, we're not expected to know that in that much detail as we're not all egawa test. And it is, as you showed, it's a multi-disciplinary approach because you're there working with your egawa test. And that's often the case with a lot of subspecialties. We we have to work with our other colleagues and all to get the right solution. I think that's the key thing to stake in the exam.
So I think knowing some things they can and can't do is helpful. So as a general rule of thumb, if by the time you start getting fixed contracts, you need 60 more than 10 degrees. There's almost no point in prescribing orthotics to try and improve knee movement because because, you know, just fixed, you can't know what it's going to be able to suddenly straighten a fixed flexion contract.
And then I suppose the other thing to just be aware of is the accommodative orthotics. So sometimes when your foot is so bad or your knee is so bad, you kind of building this splint around the patient's own different fixed deformities. So we've got some kids with their really bad feet that aren't really candidates for surgery, but you just want to give them a stable platform to walk on, walk on.
So we give them a generally an accommodative affair. We build a splint around the foot and then make a special soul so that the foot is then to the sole of this shoe is flat to the ground, even though the foot inside the shoe might be in sort of profound doesn't acquire. And so forth. So the kind of a to is just to try and make life easier. We're not trying to correct anything.
We're not tuning it in the lab to get ground reaction vectors in the right place or anything like that, but just trying to make the patient's life a little bit easier. So I suppose an accommodative versus a corrective AFO might be another sort of general principle if it's only. Um, let me think one question from is, how often do you recommend tenodesis for children with cerebral palsy?
So I do it all the time because I've got a great lab and I enjoy it, so I don't. It's difficult to. OK, so let's talk about a bit of other NIPE talk about this. It's horrible, but all the drawbacks of data analysis, there are lots of drawbacks of data analysis. So like I said, we don't really understand how humans work. So all the interpretation we do sounds very clever, but we're operating from quite a poor general knowledge point of view.
So the interpretation of gait analysis is really quite different. There's a lovely study done in Toronto where they looked at gait analysis from lots of different laboratories. So the same gait data, same video sent to different laboratories, and they come up with different, different conclusions, different recommendations.
They also did quite a nice study. This was a McMaster again in Canada, where they looked at. So they looked at people. They showed they randomized trials. So they showed some surgeons. Sorry, no. So they randomized people to the surgeon can see all of the patient's gait data, or the surgeon could only see the video and then obviously recommendations made and they found lots of differences there as well.
Then they did another one. This wasn't. This was a North American study where they showed the same. They did an intra observer reliability to the same surgeon. So the same data data data six months apart. And it was and they get different interpretations. Different labs have different normal, normal data sets. So it's not.
Unfortunately, it's not standardized like an MRI. So generally speaking, an MRI is the same as a CT scan is the same more or less as if you do it in one hospital. There's another gait analysis isn't different. Different labs have different setups, different models. The musculoskeletal model we use is different to some other labs use. Some use treadmills, for example.
Others use. Others use gait labs like we've got. Some use inertial measurement units. These are basically things you strap onto the muscles without 3-d, without motion capture. There there's lots of problems with the variability of how gait analysis is done and how it's interpreted, which makes customized recommendations of how it should be used difficult. However, there are some general principles and certainly in slap surgery.
If you're proposing level surgery, there are very, very few people that I around the country who will be happy to do that without gait analysis. Also from monitoring responses, it really is the only objective way of measuring gait. So if I do an intervention in cerebral palsy, whether it's Botox or orthotics or surgery, one of the best ways I can find out if it's made any difference is gait analysis.
So I use it sort of preoperatively for decision making and then post-operatively to monitor outcomes. And I use it a lot because I've got a date lab and I'm interested other people might use it less, but there are no absolute indications. But the closest I can get to an absolute indication is single event, multi-level surgery and stupid. And a few sources, straightforward ones, I hope so.
Do we always need few modifications for AFO and Graf and gruffalo splints? Mostly so certainly if you are, if you are using a rigid AFO where you're effectively taking away the patient's own ankle movement or foot movement, then it's a bit like having an ankle fusion. And if you give someone an ankle fusion, you need to change their shoe, particularly providing some kind of rocker.
And there's lots and lots of different rockers you can appoint loading rockers. You can have rounded rockers. You can choose the part of the foot that the rocker occurs in. You can even have rockers in front of the forefoot if you like, without without, with flare UPS and so forth. So, yeah, so generally speaking, if you're prescribing an AFO that takes away the patient's own ankle movement, then you need to prescribe a shoe to go with it.
Otherwise, they're not. If they just buy an off the shelf, trainer is not going to work very well. So the vast majority of our patients get AFO footwear combination AFO FC. OK and can a simple AFO work for idiopathic walkers, or is it just effective for crouch or jump the gate? So that's a really good question, actually. So idiopathic toe walking is a difficult topic.
So if you look carefully enough, probably up to 70% 0 of patients you've labeled as idiopathic walking's do have some pathology, and it's usually a very mild cerebral palsy or something like that. However, I would strongly advise you not to go hunting for it. If you've got a kid who's effectively functionally normal but just walks on their toes. You're going hunting for cerebral palsy or any other thing is probably not really going to help their life.
So it's not really beneficial for insurance or future job prospects. So if you've got cerebral palsy in your notes, particularly if it has really no meaningful effect on you. So first thing things is a lot of idiopathic walkers aren't idiopathic. Let's say about idiopathic. Tobruk is probably their best left alone as much as possible. You know, physiotherapy might be helpful.
Teaching them a few ankle 2 reflecting exercises and so forth might be useful. Serial castings sometimes you can do it for 4 to six weeks, just gradually stretching them out, particularly when they go through growth spurts. But actually, if you put a kid who's functionally normal into an affair, you'll make them worse. And then also, if you think about it, if you take again, take a kid who's neurotypical and you put them in a rigid airflow.
Not only does that control the sagittal plane, also the coronal plane, so it means you're taking away their own proprioception, you're taking away the ability for their ankle to develop, particularly at the young years. So I'm very, very against using avos Willy nilly. It's original air is like ankle fusion. I could well, it's like almost like an entire pan subtalar fusion.
You're taking away everything from the home foot, not only in the plane but also in the corona plane. And so, yeah, be very, very careful now. If you're really struggling and you've got a really bad toe walk and then maybe some kind of hinged leaf spring airflow to allow them to move. I would try and not. And if they're really bad, that if they're so bad, that's such high up on a tip toe, then it probably should go looking for another diagnosis, refer them to a developmental pediatrician or something like that, something like that, because often a lot of them aren't.
OK and I think last one of only a type of pathologies where you found gait lab analysis useful. OK, yes, a couple so in the adult world, so we've used it a few times now in Parkinson's and stroke. So gait velocity is quite a good predictor of severity of Parkinson's disease. Typical slow shuffling gait. You can actually use that to quantify the severity and response to treatment.
We've used it in diabetics, particularly in diabetic feet, where the patients don't have their own sensations. So getting their orthotics tuned properly, particularly with plans of pressures and foot pressures. So we can use the aponta pressure plate, which we've got in our lab to see where patients see where the patients stand on it, and it gives you a pressure map of the sole of the foot.
And so these patients don't have any of their own sensations. So we can say actually put all the pressure is over the lateral base of fifth metatarsal, something like that. And then the other disk can go away and make a total contact orthotic or something like that to try and account for that. Used it to the things like that. The other thing we've used it for more in the research concept is in hip and knee replacement.
So we've got a guy called Andy Metcalf who's got an interest in his knee surgeon by trade academic knee surgeon, but also got a history of Game of working gait maps. So we've used it. We're trying to develop models of how the knee works, so we can obviously indicate that we can model the knee in 3 planes at 100 frames a second and see really what the knee is doing during stance phase pre and post knee replacements.
So stuff like that, that's more of a research context rather than a general use. And then the other time is in foot and ankle surgery, particularly particularly people perfusion. So trying to work out what orthotics are best for best for them? So again, it's somewhat niche and it depends on your access. So if you've got an if you've got a gait lab in your hospital and you've got someone who's interested, then go and chat to them.
There's all sorts of other avenues. And as I said before, gait analysis is one of the only objective ways of measuring gait. And so if you're doing most of what we do in orthopedics, certainly lower limb orthopedics affects gait and we're hoping to make people walk better. And if you want to show that definitively, then gait analysis can help with that. So yes, if you've got research ideas and so forth and speak to your local gait, that.
Fantastic thank you very much, sir.
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