Well, welcome everyone to our third session on our AAP Menor Pediatric Lecture Series on gait review with Dr. Carollo. Thank you again for providing us with this valuable information and building off of each of the prior lectures. So with that, I'll pass it on to Dr. Carollo. Thanks again. Great. Thanks, Dinesh. And thanks everyone for joining us again today. So, so far what we've discussed is we have gone over Perry's critical events, the phases, and we ended up last time with this particular summary slide. And so this is a good summary slide that allows us to be able to go ahead and look at the critical events, the periods, stance and swing, tasks associated with these, weight acceptance and single limb support that are part of the stance period, and then the swing limb advancement, which is includes both stance period and swing period. The phases as defined by Dr. Perry, the temporal events that mark the beginning and end, and then the 13 critical events. So as we were going through this, I was slowly introducing some of the instrumented gait analysis features that we are associated and help us be able to determine whether these observational critical events are really there. And so today's lecture, we're going to go through the instruments that we kind of introduced during that with a little bit more detail, and then we're going to wrap up with a short case to be able to illustrate how we use it in our decision-making. So we need to think about this as clinical tools for quantifying gait performance. And this is a shot of our laboratory at Children's Hospital Colorado, the Center for Gait and Movement Analysis. First of all, I want to point out that instrumented gait analysis and observational gait analysis work hand in hand. The tools that we've just described from Dr. Perry were developed for observational movement analysis, but instrumented gait analysis is not a replacement for observational gait analysis, but rather it augments observational gait analysis with quantitative evidence to help you distinguish between these different critical events and identify whether they are present or absent. And that then dictates the intervention that is the dominant or important priority in this movement analysis. And so through this, I'll be using examples from our own laboratory. And so I'll just introduce our laboratory, the Center for Gait and Movement Analysis at Children's Hospital Colorado. We've been open for a long time. We opened in July of 1999 as the first and only instrumented gait analysis facility for clinical referral in Colorado. It's a high-tech motion capture facility. We had the good fortune of being able to build this laboratory in the original hospital, but when the hospital moved in 2007 to a new facility, we completely redesigned it and were able to go ahead and take the strengths and save those and then work on the things that still needed. So I'll be showing instrumented gait analysis within the context of the tools that are there, but I want to really point out that clinical movement analysis is inherently a multidisciplinary team that includes PTs, kinesiologists, biomedical engineers, and, of course, physiatrists and orthopedic surgeons. And this team works together to be able to look at movement from different points of view, weigh in on the individual requirements and the individual personalized medicine necessary to improve their gait and is really an essential feature of that, that it's both the team and it's the technology that work together to be able to make these decisions. And in fact, we believe it was perhaps one of the important early adopters of personalized medicine. In 2009, we became accredited by the Commission for Motion Laboratory Accreditation, and when you're looking for a laboratory, we would ask that you think about mowing to laboratories or referring to laboratories that are CMLA accredited because they've had peer review for all their procedures in terms of, and they have a focus on quality. We were the second one referred, accredited by the Commission for Motion Laboratory Accreditation and the first one in the Rocky Mountain region. Our laboratory is available to both children and adults. We're in a pediatric hospital, so we are biased toward our kids, so we're about 90% children and adults, and we evaluate any neuromuscular or musculoskeletal disorder, although cerebral palsy is the dominant diagnosis in our laboratory. Now, the critical measurements that all instrumented gait analysis laboratories require, and certainly it's required for accreditation. We've touched on all these as we are introducing the critical events. The first is temporal spatial measurements. This is the stride length, cadence, and speed, and we believe that gives you an understanding of overall gait performance. It's independent of the gait pattern, but it tells you how well you're performing the bipedal gait task. A second important piece is what we were really focusing on in the last couple of lectures, and that's the slow motion movement analysis, and we use observational biplane video so we can see both the front and the side view at the same time. We have 3D motion kinematics. This is probably the meat of an instrumented gait analysis. It's the hardest to get, the most expensive to get, but it also is the information that often tells us the most about the overall pattern. When we have, and this involves joint angles, velocities, and accelerations, moments, and the moments and powers, which are also an important part, are a part of the next category. I just introduced that we showed this gait deviation index briefly, and I'll talk a little bit more about that, but the gait deviation index is a composite, normalized score that we use to go ahead, and that involves all the joint angles, velocities, and accelerations, and it tells us more about the pattern of movement as opposed to the overall gait performance. As I mentioned, moments and powers, these are all part of 3D motion kinetics, and 3D motion kinetics are the principal direct measurement is the ground reaction force. This is the force that you make contact with the floor and produce a, with every foot strike you have an impact, and that impact produces a vector quantity that resists the force that you hit the floor with, and it's measured using force platforms. The final important and fundamental piece of any instrumented gait analysis is the dynamic electromyography, and its purpose is to really look at synchronized muscle activity. It's different from the electromyography that you use for diagnostic purposes that all physiatrists are familiar with, because we're really looking at motor control from the standpoint of muscle timing. We use both surface and fine wire electrodes, but we usually minimize the use of fine wire electrodes because of the concerns about altering the gait pattern with the invasive procedure, and also, fine wire electrodes sample from a smaller number of motor units and may not fully represent the entire muscle. Hence, surface electromyography is the dominant tool here used for dynamic electromyography, and this illustration right here is the case that we've visited before, and let's look at more extensively at the end of this lecture, and it's showing a video combined with the EMG to be able to really look at the timing of the different muscles during the motion task. So, temporal spatial measurements. In general, temporal spatial measurements, we've already introduced these graphs about cadence, walking speed, and step and stride length, as well as the timing of muscle activity. Here's a blow-up of that particular, and we showed this earlier in the lectures. This was the comparison of the AFO and walk aid and the individual who had lack of dorsiflexion in swing period. In particular, it was a drop foot deformity. So, the blue, all the blue that we had in here as a refresher are the quantities that are not unique to one side or the other. The green is right, red is left, and those graphs are associated with looking at, in particular, step length, stance and swing proportion, and initial, single, and final double support. All of these timing parameters can be calculated on either side, so you can compare them to each other, as well as to a normal reference. Now, how do we get this information? Well, in the clinic, there are a number of ways to be able to do it, and probably the most popular way is using mat-based systems. At CGMA, we don't use that because we have 3D kinematics, which allows us to be able to calculate that as a result of our effort to get joint angles, velocities, accelerations. But in the clinic, you can actually get very accurate temporal distance measures, cadence, walking speed, step length, and stride length in clinic-based systems. And there's a number of mat systems. This is a gait-right system, this is a protokinetic system, and this is a stride way from TechScan that also gives you some pressure distribution underneath the bottom of the foot. And all of these are relatively inexpensive in the scheme of movement analysis, but they also give you temporal distance measures. So if you're looking to measure overall gait performance, you can do it in a manner just with tools that you can use specifically for this purpose. And many laboratories that are not interested in kinematics or do not have a full instrumented kinematic laboratory can provide quantitative information quite successfully on overall gait performance using these mat-based systems. There are other tools that can be used, but the mat-based systems are probably the most widely used. But this brings us to kinematics, which again, as I mentioned, is probably the dominant feature that you think about when you think about an instrumented gait analysis laboratory or a clinical motion laboratory. And kinematics are looking, again, joint angles, velocities, and accelerations. So it's important to distinguish between kinematics and kinetics. And I've already mentioned this, but I just want to reiterate that kinematics is how you describe the pattern of movement without consideration for the cause of the forces involved. Linear and angular displacements, velocities, and accelerations of individual limb segments and joints, as opposed to kinetics, which is focusing more on the forces that are associated with that. And we'll talk a little bit more about that after I've discussed the kinematics. But it is important to see that while both of these are three-dimensional, kinematics is associated with the positions, and kinetics is associated with the forces or moments, which is equivalent to an angular force or torque. To be able to get this, the dominant devices that are used for this are going to be non-contacting kinematic systems. And these are camera-based systems that track markers. In our laboratory, we're using a Vicon system, and these are some specifications about it. We utilize a 13-camera system with A-to-D converters that allow us to collect force platform data and EMG data at the same time. It's all governed under software systems. Again, we use Vicon, but frankly, all the manufacturers that provide instrumented gate analysis systems have developed to a point where it's less important which system you have. That was how it was at the beginning. There was some significant differences between the accuracy and precision of the various systems. But technology has moved it along that most of the kinematic systems that are out there that are measuring the displacement of markers all have the potential to have accurate and precise measurements. And all of the systems that utilize markers could be used for CMLA accreditation. And so this is because these tools have become more affordable as well as become more accurate. And so these are the various manufacturers that are often the leaders in this. Vicon, Motion Analysis, Qolsys, Optitrack. So CODA Motion is an older system that is probably not as prevalent anymore that utilized a different approach to motion capture. And then some of the newer systems that are based on markerless motion capture really are becoming more useful. And we can discuss that as a separate entity in the future. But today, as of right now, the marker-based systems are the de facto standard. Regardless of how you collect this data, however, they all work under a very similar principle. And they use passive marker that you apply to the body. And then the cameras reflect using a ring light, either infrared or near-infrared LEDs. And they reflect off of each of these markers. And they give you an opportunity to locate those markers within three-dimensional space. They don't necessarily give you an image of the subject. They really are focusing as coordinate detectors. And they're really just detecting the location of these reflected markers that are being worn. And they are passive in that they don't generate their own signal. There are some systems that use active markers as well. And it's just a different approach. But dominantly, passive marker systems are the de facto standard. And the reflective markers are eliminated by these light sources that are coming from the camera. And then the basic rule that is necessary for this is that all these markers that are on the body have to be seen by at least two cameras. So probably the question comes to mind, well, if all you need are two cameras to be able to do 3D instrumented gain analysis, why do we have so many? And it has to do with obstructing markers as someone moves. As an arm swings across the body, you may obstruct some of the markers that are on each limb segment. So there has to be two cameras seeing the markers. And then you have to have three markers per limb segment to define its location in three-dimensional space. Those markers may be actual markers, or they could be virtual markers that are extracted from the markers that are being tracked. But in the end, you need to be able to define a plane of motion. And to define that plane of motion, you need three markers to define that plane. So once you have the ability to identify where markers are in three-dimensional space, then it's necessary to be able to apply a gate model so that you have a certain location, fixed location, for placing those markers. And there are a variety of models that can be utilized. The most common is called the conventional gate model, or CGM. And this is a description of the kind of layout for that conventional gate marker. Essentially, you have tracking markers that are on the surface of the skin, and they are being related to joint, to the actual joint centers that are, obviously we can't put a marker on the joint center. So we utilize surface markers for tracking, and the surface markers have a model that defines where the location of each of the hip joint, knee joint, and ankle joint in particular are relative to those surface markers, as well as identifying the location of the pelvis in three-dimensional space, and the location of the foot in three-dimensional space. That's referred to as the foot progression angle. This is describing it as a lower extremity model, which is the most common. And what I'm showing here is the typical layout that we have in our laboratory and most laboratories around the country that utilize the normal 3D kinematics. And it's typically three degrees of freedom, pelvic tilt, pelvic obliquity, and pelvic rotation. Hip in three dimensions, hip flexion extension, hip abduction, adduction, hip rotation. The knee in three dimensions, knee flexion extension, knee varus valgus, and then the knee rotation. In this case, we actually are calculating distal shank rotation, so we are looking at the knee rotation, but we're doing it relative to the distal shank, so that we include the tibial torsion calculation in our measurements. And then ankle dorsi planar flexion and ankle rotation. This is less common, but we include that. However, because the ankle rotation really doesn't align with the subtalar joint axis, so it's a model-specific rotation as opposed to a truly anatomical rotation. And then foot progression angle is the angle, it's the toe in and toe out angle. Or in other words, the description of the foot progression, the angle of the foot relative to the direction of progression. And that's relative to the global coordinate system just like the top of the chain is, the pelvis is relative to the global coordinate system. Then this is for a lower extremity model. We have full body models as well, but I'm going to focus on the lower extremity model because that's often the most relevant for movement analysis. And as you notice, in these normal 3D kinematics, which is important to have the other planes of motion, oftentimes the pelvic tilt, the hip flexion extension, the knee flexion extension, and the ankle dorsi planar flexion, these are often the ones that you are most interested in. And they're also the ones that have the greatest displacement, so I'll focus on those from a normal standpoint right now. So in general, if you take a look at the overall pattern, the sagittal plane angular displacements are larger than the other planes, excluding the pelvis, which is a low amplitude two-time sinusoid over the gait cycle. Typically, these graphs are going to be introduced from zero to 100% of the gait cycle, which means from ipsilateral initial contact until that same foot makes contact with the floor again. These are most easily observed without measurement equipment, and they have these characteristic shapes during the normal and normal walking. The pelvis is a low amplitude sinusoid. The hip flexion extension cycle is a single flexion extension cycle or one sinusoid over the gait cycle. The knee has two sinusoids with a loading response peak during a loading response and a initial swing peak that's associated with the knee flexion as we pass it directly underneath us. And then the ankle is the three rockers that we've talked about. First rocker as you lower the foot to the floor, second rocker as you control tibial advancement, and third rocker where the power is being generated that we'll talk about in just a moment. And then finally, dorsiflexion back to neutral to accomplish the critical events in mid-swing and terminal swing. And it's important to point out that limitations at any joint affect all the others. And we saw that in the examples we've shown during the first two lectures. So a limitation at one joint that might be a direct problem, a primary deficit, can have secondary or compensatory changes at any of the other joints up the kinematic chain on the same side or on the contralateral side to accommodate that joint limitation. And we have already shown this one previously, so I'll run through this one relatively quickly. But this was our Crouchgate patient that we saw with the DFEO, the Distal Femoral Extension Osteotomy. And this shows the pre- and post-value. And I've already introduced this, but again, just to reiterate this, if you look in this portion of the screen right here, this is the pre-op knee flexion extension, where we are up close to 80 degrees of knee flexion pre-operatively. And we had a significant improvement in the upright posture as well. And we also had a improvement in the ankle kinematics. And the beauty of this is that we can really quantify the difference between before and after and identify those critical events that are missing and then also show the improvement and the kinematics as well. Now, I've been talking about GDI, and I'll just go ahead and just quickly define this. The GDI calculation is a normalized and validated measure of gait performance. It describes the overall gait pattern. It's calculated using the difference between a subject's 3D kinematics and a normal reference. And these that have a red border around them are the kinematic joint motions that are used in the calculation of the GDI. So it's a analytical technique called principal component analysis that allows you to take these individual deviations and then put them on a 0 to 100 scale, which makes it easier for clinical interpretation. You calculate them separately on both sides. So the overall GDI is the average of both sides. It's on a 100-point scale, where normal is 90 to 100. And each 10 points represents one standard deviation away from the normal on these nine kinematic curves that make up the GDI. So that's where it comes from. Again, the GDI has been a very useful tool that most laboratories that are doing clinical work utilize in having a composite measure of the kinematic difference for each of their subjects. There's an additional feature that we include in this. And this is how we present our GDI. And in this particular case, you can see that this subject, this, again, is that drop foot individual. And as we've mentioned before, the GDI improves on the side when an AFO is used. And so the red bar improves and pushes up into that normal range. But to the right are the individual contributions, where the GDI is bigger is better. The movement analysis profile is something that was developed in a separate laboratory. And it's actually looking at the RMS difference. And for the movement analysis profile, it's bigger is worse, because it's talking about the RMS difference between the normal reference and the subject's pattern. And so this way, you can go ahead and point out that in this particular patient's case, the ankle dorsi plantar flexion on the red side, the left side, was significantly improved with the AFO and the walk aid. And that's why the overall GDI improved. And it allows you a quick location to be able to look at those nine curves that make up the GDI. And it helps us understand better where the deviation is and points us in the right direction. This isn't a replacement for looking at the individual curves. But it is a way to be able to pinpoint what needs to get the most attention, because there is a lot of data when you're looking at kinematics for an individual. Looks like I have that slide in there twice. So this moves us over to kinetics. And so I want to just point out how we get kinetics. I've already introduced what kinetics are. The critical feature that's added, so you need 3D kinematics to be able to calculate the kinetic parameters. But the critical new piece of information is the ground reaction force. And this is a schematic diagram of the forces. So it's a reaction force, which means it's three-dimensional. So when you make contact with the floor, it's a single 3D force resolved into three components. And those three components are, as shown, the fore and aft shear, the medial lateral shear, and then the vertical component. These are orthogonal components of the impact with the floor. It's important to point out that the force platform measures the net result of all forces of moment. It's not just the gravitational force that is associated with your weight. But rather, it also includes the muscle forces that are associated with the contractions and the timing of the muscle during movement. So that adds an additional force. And it's measured in the composite single 3D force. So the single 3D force is representing all these forces. It doesn't distinguish between gravitational force, muscle force, or this last force, the F sub i, which is the inertial force. And that's basically the impact and the force associated with the mass of the body making contact or moving during its contact with the floor. These are all measured with a device called the force platform. In our particular case, we have a large force platform array. The red area in this schematic diagram is where our force platforms are. And then we actually have another device, a plan of pressure measurement system, that is also in the gate lane. And it's at the end of the gate lane when you're moving from left to right. And that does not measure the 3D vector quantity of force. It measures just the scalar pressure distribution, the normal pressure to the floor. It does not include shear forces. And so these are both embedded in there. And I just include this picture to go ahead. And within our laboratory, the installation of force platforms is a more complicated activity. This is some pictures from when we installed our system. And the force platforms are at the top of the upper left diagram. There's the force platforms that are there. And you'll see this large structure. This is a structure that holds all of the surrounding floor and holds this pressure plate here in the foreground. The force platforms are all mounted to this concrete slab that are underneath it. And you see this thin line. It's actually mechanically isolated from the rest of the building. This is why many motion laboratories are in the basement, because it's much easier to isolate the force platforms from the surrounding structure. When you're in upper floors for a force platform, it becomes more complicated. Because you then have to go to great extremes to isolate those force platforms, because they're highly sensitive. They pick up any vibration that might be induced by walking on the floor around it or elevators that are close by or other things that might be going on in the building. So being in the basement, it makes it a lot easier for everyone to have an accurate measurement of the ground reaction forces. So what do you get when you have a force platform? This is an example of the three components of the ground reaction force. And the most characteristic one is the vertical component of the ground reaction force. And in this diagram, you see that there's 0% to 100%. It's scaled in percentage of body weight. And the feature that's really important to understand with a ground reaction force is the fact that this 100% kind of goes through. And when you're in full weight bearing right after loading response in the beginning of mid stance, you see that you actually weigh one point. In normal walking, you weigh about 1.2% or 120% of body weight. And so your body weight is right here. And it's not at the maximum. The reason for that is so you have a peak here during loading response, during weight acceptance, where you weigh greater than 100% body weight. And then you have a second peak here during pre-swing when you're actually generating greater force and body weight again. This first loading response peak is the result of the fact that the ground, remember, the ground reaction force measures not only the gravitational force but also the muscle force and the inertial force. And so the inertial components that are associated with the center of mass, basically the center of mass is accelerating toward the floor. And that inertial component adds as well as the co-contraction of all the muscles that occur are all generating force in preparation for this impact of weight bearing. So you weigh greater than 100% of body weight. And then the second peak is associated with also the power generation with push off, which also adds to your body weight here. What is perhaps not as obvious is that you weigh less than 100% in mid stance and terminal stance. And you reach a force minimum in the middle. This is because, again, the inertial forces at this point in time, the center of gravity is moving up. And that's subtracting force from your body weight. And this is also the period when most of the muscles, except for the gastrocnemius, are silent. And so both muscle forces is being reduced. And the inertia is traveling away from the floor, which subtracts that. So the net result is you weigh less than body weight. I should point out that these peaks get greater and greater with faster and faster walking speeds. And certainly, they can reach two and three times body weight during running where these peaks are very much exaggerated. But also, this trough in the middle also gets exaggerated. The medial lateral shear components, the characteristic of this is that you have a zero crossing right in the middle. This is the fore-aft shear. So when the body passes over the stance limb, those shear components go to zero. And they cross over. So initially, the ground reaction force is resisting the forward motion. As the center of gravity goes over the base of support, it's actually going with. It's pointed in the same direction as the direction of progression. That's why it becomes higher. And notice that the medial lateral force is the smallest of them. It's about 1 quarter of what the maximum fore-aft shear component is. So this is the smallest shear component. But it's influenced by your base of support. When you walk with a wide base of support, the magnitude of the medial lateral shear gets greater. When you walk with a narrow base of support, it gets less. So those are just some features of the ground reaction force. Now, why do we want the ground reaction force? Well, the business end of this is that you use it in an inverse dynamics model. And this is where Newton's second law comes in. And force is equal to mass times acceleration. And so we sum the way you calculate this. The simplest way is to start at the floor. You have the location of this ground reaction force from the force platforms, its location, and its magnitude in three dimensions. And then you successfully sequentially use Newton's second law. And you calculate the ground reaction force. And you shift and find the impact of that ground reaction force at the ankle. So you calculate both the linear force and the moment of force, which is using the moment of inertia times the angular acceleration produces the moment calculation. You do it first at the ankle. Then you use that solution to solve for the knee. And then you use that solution to solve for the hip. And as a result of that, you work up the chain. And it allows you then to go ahead and calculate the normal moments and powers as a result of this application of Newton's second law. And so I'll just blow this up as an example. And this is the kinematics that we showed you earlier, the normal single sinusoid, the loading response, and knee flexion peak that follows. And then three rockers at the ankle. Notice that the moments, it's hard to read in this slide. But this is a hip extension moment that you start off with and has a characteristic shape. The knee moment, you see, oscillates around zero as you go through there. So that's first a knee extension moment, and then a flexion moment, and then an extension moment again. And then the dorsi plantar flexion moment is a smooth, increasing plantar flexion moment all the way through as the calf muscles have to increase their torque, their force generation that produces the plantar flexion torque that contains the center of gravity as it moves forward. But it's important to see this hip joint power, knee joint power, and ankle joint power, which is the joint power is the product of joint angular velocity and the joint moment. And so as we go ahead and have this information, it allows us to calculate that from zero, the upper portion of the curve is zero to one and two normalized in watts per kilo in this particular case. But that's the power generation is above the line. Power absorption is below the line. And it's the power generation curves, as I mentioned earlier, that the power generation at the hip and the power generation at the ankle are the reason that you have passive knee flexion in the absence of any hamstring activity. And so that's power absorption right there. This is the evidence from the power curves that you can use and the way we discovered that the knee flexion is a passive movement because the hamstrings are unnecessary as long as you have good power generation above the knee and good power generation below the knee while the foot is still in contact with the floor. And that closed kinematic chain leads to power absorption at the knee that causes it to passively flex because of the two power generators above and below. So these are the normal power curves. It's important during instrumented gait analysis to generate and look at the power. If someone's walking with a calcaneal gait pattern, you often see a reduced ankle joint power. And if someone's walking with a slow cadence, they often have a very reduced hip power generation. But the kinematics and looking at these curves and becoming familiar with what the normal curves are, comparing them to the normal curves, allows you to be able to make the decision, is their power generation appropriate, normal, or is it deficient, which would then suggest looking at interventions to restore the normal power generation so you can have a more normal gait pattern. OK, that was a fast run through for the kinematics and kinetics. I'm also going to go very quickly through the dynamic EMGs. We've talked a little bit about this within the context of that previous case, and we'll show that in more detail in just a moment. In this particular case, this is the dynamic electromyogram. And we can see if this is going to play. This one in particular doesn't play. It's just an example of the dynamic EMG that we see and where we have six muscles on the left and six muscles on the right. And we look at the general timing of those during the cycle. Now, how do we get dynamic EMG? It's with some type of EMG sensor. These are some of the original EMG sensors that we used in the laboratory when we first moved. We've been through several generations of these and now use wireless EMG sensors. These EMG sensors actually had to be wired to the individual and use separate electrodes. And this one is the configuration for the rectus femoris. But in general, we're measuring muscle activation patterns during a dynamic or function activity. It uses electrodes and an amplifier to record the pattern. Greater amplitudes correspond to more activity is the general rule. And so we're really looking at the amplitude of these signals relative to normal and the timing of those signals. We are now using wireless transmitters that have some very interesting characteristics, including this double differential bar arrangement. Many laboratories around the country have used DELSIS, but there are excellent products from many manufacturers. This particular system makes it much easier, and it cuts down significantly on the time it takes to record these EMGs because the placement is so much easier with a wireless transmitter. And most laboratories are migrating to wireless EMG technology. I talked about the timing of all the muscles, and this is a normal EMG timing reference from Sutherland, 1984. And this is an important reference that most laboratories use as their normal reference guide. But in most laboratories, and certainly if you're going to achieve clinical accreditation, you always collect your own normal data in each laboratory, and then you compare it to this normal timing. And if the normals that you have might be the start and stop of each muscle may be a little bit different. But in general, it's important to go ahead and see this. This particular book is more difficult, or this original book, this 1984 reference, is a little hard to find at this point. It's reproduced in Chris Kirtley's book, and it's a good book to have if you're going to be investing time in clinical movement analysis. You've seen this one before. We talked about this from Inman. And again, the general consensus on the muscle timing is that most muscles are active at the beginning and end of swing and stance period. There's minimal muscle activity in mid-stance and mid-swing despite this being a period of maximum angular displacement. We saw how that could be represented in the power generation curves. And then the principal action of muscles is to accelerate and decelerate these. So it's important to go ahead and have both the general understanding of muscle timing and those normal references when you're comparing the timing for an individual with a gait pathology. OK. So now I'm going to stop this share and bring up a different share if I can. So bear with me for a second. Hopefully this will work. I'm going to share this screen. We can see it. It looks good. Good. Thank you for the feedback. This particular patient is the one that we have seen here. It should be familiar now. This is our Stifnegate patient, and so the bottom line on this is that we have now gone ahead and introduced the core measurements and instrumented gait analysis, and then the question is, this is a lot of information to look at. We utilize a tool that's a proprietary tool from Vicon called Vicon Polygon, and that's what I'm going to be showing you here. And so Vicon Polygon allows us to take all this information together and then put it together into an animated screen so that I can click on the various aspects of the gait analysis to be able to look at this. Now, you'll notice that this particular polygon, this first case, as I had mentioned before, this is that Stifnegate patient, and this is how we utilize all of this information to make this decision. And so if you see here, what we're doing is that we have our biplane video, so we can see both views of the subject. You'll notice that this young lady is using the original system for EMG that has wired, and usually they carry this backpack, but in this particular case, the backpack was a bit encumbering to the patient, so we're walking behind, our therapist is walking behind and carrying it. There's the real-time EMG, but then here are the 3D kinematics. And the important thing I wanted to point out, we've already seen this curve, where green is right, red is left, the blue band is the normal reference. And if you take a look at this, you can see that the knee flexion, we pointed this out before, is very limited, and this is what defines it as Stifnegate. Now, the information that I didn't show as much is the fact that there are other abnormalities, and our job is to go ahead and sort and identify the primary deficits from the compensatory deficits and focus on addressing the primary deficits. And you can see that she has an increased anterior pelvic tilt, along with a forward trunk lean. She has a reduced amount of hip extension at terminal stance, bilaterally. If we look in the frontal plane, if we look in the coronal plane, her pelvic obliquity on her affected side, her pelvis is down, her pelvic obliquity on her less affected or more normal side is up. And then this pelvic retraction is important because here we can see that she's retracted, on average, about 20 degrees on that side, and that allows her to be able to go ahead and take a little bit more time to try to do limb advancement and also do all the compensatory factors of circumduction, et cetera. And so you can see that, so we can take a look at that in three dimensions. The beauty of this tool is we can also go ahead and rotate this so that we can look at it from dimensions and positions that we didn't otherwise see. This view, I think, is especially useful for being able to understand the value and the necessity for the retraction on this side. And that retraction is really an important piece of this. It also highlights, here's the foot, this is ankle rotation, and there's our foot progression angle. And you can see that as a result of this, slide it over so we're looking more directly over it. The result of this is that she's retracted because she has stiff knee gait, but the retraction also leads to external, a large external foot progression angle. Typically, we're close to pointing in the direction of progression. The right side is also a bit externally rotated, but it starts from the pelvis. So in her particular case, the EMGs are important, and critical to making this decision. And so the EMGs that we have, we can bring those up to look at them in time series. And as you see here, this is the rectus femoris, this is the vastus lateralis on the left, and this is the medial hamstring on the left. And we can see that there are some, there's prolonged activity. I'll play this forward. There's prolonged activity out of the vastus lateralis. The vastus lateralis does not cross the hip joint. So as a result of that, there is activity here during loading response. And we can see that it's a little bit prolonged on the left side. But the important feature that we see, oh, we also see that the hamstrings, there's kind of co-contraction with the hamstrings, perhaps because of the stance period stiff knee gait, there's a little bit of stretch in the hamstrings that she has during weight acceptance. But the really critical piece here is this rectus femoris. And if you look at this step after step after step, the rectus femoris does cross the hip joint. And so the loading response peak that we see right here, this loading response peak is there. We have a second peak that's associated with the rectus operating as a hip flexor. But what I wanna point out is see how prolonged this is afterward. So she can turn it on, albeit a little bit late, but she cannot turn it off in time. And that's the prescription for rectus femoris transfer. And I introduced some of this during that, but it's important to go ahead and actually look at these comparisons together. And it's loading. It wants me to normalize it. And we can see very easily here as we go forward that as a result of that rectus transfer. And so now we see this in three dimensions. We can see how the pre-op and the post-op from the model standpoint have been altered. Here is the pre. And here is the retraction has been eliminated because there's no longer the need for it. And the solid line corresponds there's that improved post-operative knee flexion. And then the pelvic rotation has been restored back to neutral. And here's the evidence that we have. So we have observational information, but we also can see that some of these other deviations have been modified. Here is the improvement in the hip extension at terminal stance. And here is some, no real improvement on the right side, but the important improvement is on the left side we have. So we're at the top of the hour or we're close to the top of the hour. So I think the main point of this was to try to show how we can take all this information together, use instrumented movement analysis to go ahead and identify the best solution, identify where critical events are missing, use instrumented gait analysis to help us with our decision-making, and then provide the evidence to show where improvement has happened, but also to steer the interventions. So let me stop this share if I can. Okay. All right. So I think that that's as much as we have time for today. I think we've covered all the important pieces. This was a very fast introduction to instrumented movement analysis, but I tried to go ahead and put it within the context of what we covered in the previous two lectures. And so I guess we have just a couple of minutes for any questions that may come up. Nash, have I left anything out here that I think that we tried to cover it all? I apologize that it has to be very quick with this instrumented piece. I hope it's a good introduction for everyone. If you have any questions about this that come up, I think my email address is available or you can look for me on the web through Children's Hospital Colorado, and I'm happy to help and answer any questions related to this. I hope I've given you enough of an introduction so that you can go ahead and be a good consumer of instrumented gait analysis. I would encourage you to find an instrumented laboratory that's close to you if you don't already have one in your organization, and see if you can incorporate it into your clinical decision making, because we believe that having the information only allows you to make better clinical choices. Thank you so much, Dr. Carollo, for all that you've done for us over these past three sessions. We do have one question, which is roughly how much does it cost when it comes to the lab cost these days? In terms of how much does it cost for a full instrumented gait analysis for the client? Is that the question? To set up a full lab. Oh, to set up a full laboratory. Good, that's an easier question to answer. The question that I was suggesting is really a very regional question. The prices change, the insurance coverage is challenging. I can tell you that more insurance companies are beginning to approve clinical motion analysis so it can be available to everyone, and some of the newer technologies are making it more accessible. But it's still an expensive proposition for everyone that's there. In terms of how much does it cost to set up a laboratory? Those prices have come down substantially. The first laboratory I built that was a full instrumented gait analysis laboratory at Texas Scottish Rite Hospital, the costs were upwards of half a million dollars. The more recent laboratories I've designed, and our most recent upgrade, you can really have an extremely functional instrumented gait laboratory for under $150,000. It still sounds like a lot of money, but it's come down to about a third of where it was when we started. This is the promise of the new technology. Markerless motion capture gives the opportunity to really reduce the initial cost. But I should point out that the initial cost of the laboratory itself is really the smallest part of the big picture. It's the people, the technical specialty, the specialized training that you need from engineering, kinesiology, physical therapy. Most physical therapists understand movement analysis but may not be as skilled with instrumented gait analysis, so it's really important for you as the provider to understand how to use it so you can guide and utilize the information. It's an expensive initial investment but very manageable within the modern healthcare system. The ongoing costs are challenging for a hospital because of the very specialized personnel. I hope that answers the question in general. Can you speak a little bit to the posterior tib fine wire individual assessments? I know that when I was a fellow, that was something that the rehab medicine team performed for select few patients specifically. Can you speak to that procedure added into the instrumented gait analysis? Absolutely. Again, the reason we use surface electrodes is to get information from a larger muscle, more motor units, so we get more of a characterization of the total muscle, whereas a needle or fine wire electrode is looking at fewer motor units. Having said that, obviously surface electrodes are limited in that if you are interested in a muscle that is underneath layers of muscle, it's a deeper muscle, you just can't get a muscle like the posterior tibialis from a surface electrode. You're going to get crosstalk from tibialis anterior or gastrocnemius or peroneals. All of those will interfere because you can't isolate it. In that circumstance, for any muscle that's not directly under the surface of the skin, you need to use a fine wire EMG technique. That fine wire EMG technique are basically it's two 50 micron platinum wires that are inside of a 25 gauge cannula. You use the cannula to locate it. There are very specific instructions from normal anatomy in terms of the placement. Our therapists and our PMNR physicians are both trained in that technique and you actually insert that into the posterior tib and then you connect it to these external amplifiers and we look at the timing. Posterior tib is a dominantly a stance period muscle and in circumstances where you may see a at pre-swing and going into initial swing, you see a medial whip, those patients are going to be, we would probably want to see if the posterior tib is contributing to that. Sometimes the posterior tib is no longer a stance period muscle and may in fact have pre-swing and initial swing timing so it's functioning. So basically it's maybe turning on at the correct time as during mid stance, terminal stance, but it's not turning off at pre-swing. And if it's continuing to contract, it can contribute to that internal equinovarus foot posture that we sometimes see. But even in the absence of seeing that equinovarus posture, posterior tib is sometimes important if you find yourself where you're loading the foot on the lateral side, you have a more supinated foot during stance period, the posterior tib may be interfering. And the possible interventions for the posterior tib are either a posterior tib lengthening or a posterior tib transfer, which can go help balance the foot. And in that circumstance, when we see that kind of foot position or we're questioning the activity of the posterior tib, we do ask, and we often have a referral requirement to study that with a fine wire electrode. You can use fine wire electrodes in any muscle. In adults, they use quite a few more fine wire electrodes than they do in children. And that's really just the challenge. If you ask a kid, what's the worst thing about coming to the hospital? It's generally speaking, I think 90% on some studies, if not higher, it's, are we going to get a shot? And so we minimize that since we're dominantly a kid's lab, but there are all adult facilities that routinely use multiple fine wires during an assessment. And that's just a different instrumentation issue. But in many cases, the specificity and the lack of crosstalk, fine wire electrodes really improve on that. Thank you so much. Are there any other questions? Okay. Well, thank you again, Dr. Curlow, really grateful for the time and everything that you've presented. This will be recorded and posted onto our pediatric lecture series for people to view. Thank you again.

gait analysis

observational methods

instrumented methods

Children's Hospital Colorado

motion capture

biomedical engineering

temporal spatial measurements

3D motion kinematics

dynamic electromyography

personalized medicine