2012 PRORP Investigator Vignette

Title: Development of a Mobile Gait Analysis System for Military Lower Limb Amputees

Investigators: Boyd Evans, PhD and John Mueller, PhD; Oak Ridge National Laboratory

Evans: Our project is the development of a mobile gait analysis system for military populations with lower limb prosthetics.

Mueller: So basically what we're trying to do is take the gait lab out of the gait lab, so a clinician has access to it.

Evans: As of May 3, 2012, there were 775 soldiers with major limb amputations in Operation Iraqi Freedom and another 581 associated with Operation Enduring Freedom. Our military amputees are different from those in the general population in that they're in top physical health. They're warrior athletes. They expect full rehabilitation and want to return to fully functional lifestyles following their injury.

Mueller: So one of the problems that these young men and women face is that they put more stress on their healthy limb and what that results in is overuse injuries, chronic injuries, chronic disease like osteoarthritis, and they're wearing their joints out essentially. And they're getting osteoarthritis earlier than a normal patient would. So the goal of this project is to give the prosthetist a tool to bring that number down to take that asymmetric gait and drive it down and make it more symmetric so the patient isn't putting you know too much force on their healthy limb.

Evans: Typically, biomechanics and gait, the measurement of walking motion, is measured in a video gait laboratory. Part of the process of measuring the biomechanics of any subject in a gait lab is to collect the forces from the foot. This process is typically used with plates hidden in the floor that can collect the-the forces, we call them ground reaction forces, as the subject walks over the plates in the floor. So what we've done in the shoe here is we've taken the technology of the force plate and we've made a device that fits right on the bottom of the shoe that incorporates a very accurate method of both isolating those forces and measuring them.

Mueller: The heel has seven force sensors in it. The toe has nine force sensors in it. We'll have what's called an inertial measurement unit or an IMU on the trunk, on each one of the thighs, on the actual prostheses and then all down the healthy leg. So now we can collect all of the forces and the moments that we need to get a full picture of what's happening in the patient on both the affected and unaffected limb.

Evans: So the data in this device can be recorded and stored inside the device using an SD card. We can also transmit the data wirelessly using Bluetooth or Wi-Fi.

Mueller: So one of the advantages of our system is that you can take it anywhere; it could be used in a doctor's office, you could take it out and use it in the street. So what that allows you to do is to take a look at how some of these patients are doing in their everyday life, how they're doing when they walk down the street. They're trying to manage curbs-some of the things that can't be replicated in a controlled environment like the gait lab.

Evans: They can do high level activities like basketball, jumping, running-anything they want to do they could do that activity. We even have a limited amount of weatherproofing to the system so that it would survive wet weather even.

So in the process of our research we have validated the technology using a robot that has similar motions and dimensions to a human leg.

Mueller: We've collected inertial measurement unit data. We put it through our data fusion algorithm and then compared the results from our algorithm and the results from what the robot actually did.

And if you look here, the red line is what came from our data fusion and the black dotted line is what the robot actually did. So you can see here; this is for one gait cycle that we're following the trend pretty closely. So it's working.

Evans: And then our next step is to test in a clinical setting on subjects in a video gait lab so we can compare the results we get with the results of a video gait lab.

Mueller: The challenge is going to be when we actually go to Center for the Intrepid, we're not going to be using robots; we're going to be using real people. So we have to strap these on to someone who has big muscles and skin that's moving around so we're going to have to deal with things like that. They're going to be moving across the room whereas the robot was just sitting there. The robot had smooth motion; people aren't that smooth. You know they change things up. They, you know, trip and things like that. And the robot was moving pretty slow.

But, we're thinking looking at this data, we're thinking that we'll be able to make adjustments and-and end up with results that we're really happy with.