It’s not always easy to walk in someone else’s shoes. It’s even more difficult if those shoes belong to a person with an artificial leg. However, that’s exactly what a group of scientists, engineers, and clinicians at Orthocare Innovations are doing to help engineer prostheses that respond better to the physical needs of amputees.

Fig. 1 – Vicon markers are placed on test subject wearing a boot cast with the Magellan prosthetic foot attached to quantify the movement and forces related to the prosthesis and the person’s body.

Orthocare is a small R&D company in Mountlake Terrace, WA, that develops smart prosthetic components with microprocessor controls for people who have lost a limb, particularly a leg or foot. These technical advances have resulted from scientific studies conducted at the company’s gait lab, where cutting edge technologies are being used to conduct intricate motion research that has led to the company’s prosthetic advancements.

“We have a number of experts in our group who examine the critical components of joint movement during walking, say from their ankle or knee, and then they try to re-create the missing element in a computer-controlled device,” says Michael Orendurff, senior scientist and director of the biomechanics laboratory at Orthocare, which, in addition to R&D, provides integrated clinical prosthetics care to patients through its sister company, Seattle Orthotics and Prosthetics (O&P).

In general, the prosthetics industry has approached technical innovation with baby steps, mostly due to the decades-old health care coverage structure that leaves little incentive for innovation. “We saw there was a big need on the research side of prosthetics,” says Orendurff.

Innovative Gait Lab

Prosthetics historically has been more of an art than a science, particularly when it comes to fitting an amputee with a new limb. However, various technologies are making that process more of an exact science thanks to the use of 3D techniques, such as digital scanning.

Orthocare conducts its product R&D at its gait lab—one of only three such laboratories in the world operated by prosthetics companies, and the only one located in the US. Here, scientists, engineers, and clinicians conduct gait studies while developing new prosthetic devices, including Orthocare’s latest device: the Magellan microprocessor-controlled foot. As Orendurff explains, the key to analyzing a person’s gait is to look at how their entire body moves, not only as they walk, but also as they are in a restive state. To this end, the researchers use a Vicon motion-capture system to quantify the movement and forces related to the prosthesis and the person’s body.

The gait lab was built two years ago, and the researchers continually incorporate new, relevant technologies and updates to its existing equipment. The lab contains a capture volume, a space that is approximately 8 meters long by 2 meters wide by 2.5 meters tall, where the person’s motions are recorded. Surrounding the capture volume are 8 16-megapixel Vicon T160 cameras that track 40 tiny markers strategically placed on the subject’s body (head, torso, upper arms, thighs, lower legs, feet, and so forth) in 3D space. The cameras stream each marker’s x and y coordinates in real time to a workstation running Vicon’s Nexus 2 software, which post-processes the data and presents it as an animated skeleton on a computer screen. (See Figure 1)

Orthocare researchers also use Vicon’s Plug-in Gait, a biomechanical model for the lower limbs that accurately shows the anatomical placement of the joints. “Sometimes the joints are not quite healthy and they violate the model, leaving it up to the person applying the markers to find the center of the joint,” says Orendurff. A series of patterned movements help determine the location of the joints and whether the markers are placed correctly before proceeding with the testing.

The group additionally uses Vicon Polygon reporting and presentation tools to review and analyze the data. With this software, the researchers can view native video overlay in the 3D workspace, and create graphs and visuals that represent their data, making the results easier to understand and discuss.

Working in conjunction with the Vicon system are two forcesensing platforms on top of which a person walks. The platforms use sensors to measure the person’s weight in all directions and then feed that information into the biomechanics software suite to provide the researchers with an accurate picture of what each joint is doing as the person walks.

How It Works

Fig. 2 – The Magellan prosthetic foot by Orthocare Innovations.

When the researchers at the gait lab set out to create a microprocessor-based prosthetic foot that mimicked the movement of a human foot as closely as possible, no one told the group they were about to attempt the impossible, or nearly such, as it turned out. “The foot was impossible to make, but we didn’t know that, so we just built it,” says Michael Orendurff, senior scientist and director of the biomechanics laboratory at Orthocare Innovations.

The Magellan prosthetic foot contains a microprocessor and Bluetooth LE technology. But what is truly revolutionary are the hydraulics, built to withstand 50 times the pressure of construction equipment, like a backhoe, without leakage. “The ankle gets compressed while supporting seven times a person’s body weight,” explains Orendurff.

Still, nothing can replace the human muscle, Orendurff points out. A powered prosthetic, for instance, would require an excessively large battery to come even close to achieving the necessary propulsion to move a person forward. “We built a glider, an unpowered device you can control and one that does precisely what you would like it to do,” he says. “It’s a stable, low-energy, adaptive hydraulic system that moves the prosthetic ankle and makes it more functional.” (See Figure 2)

Moreover, the group has incorporated connectivity into the foot, linking it to the user and the user’s healthcare providers, enabling both to make necessary adjustments to the limb through a HIPAA-compliant smartphone app.

Feet First

Fig. 3 – Testers in the gait lab wear a walking boot that can be fitted with any prosthetic foot.

The researchers have focused their developments mainly on the foot at this point and are in the initial stages of devising a solution for the upper body. They first began kicking around the idea of developing new prosthetic components approximately five years ago. They spent nearly 12 months on theorem and 48 months on R&D before building a prototype of what would become the Magellan microprocessor foot/ankle system. Then came a loop of testing and refinement in the lab.

The Magellan is a prosthesis that mimics key features of a human ankle essential to normal gait. What’s so unique about the prosthesis is that it adjusts and reacts to changes in surfaces and motion (sitting, running, walking uphill, walking downhill, and so forth). The foot uses a complex control algorithm with sensor criteria to answer questions to determine various states of motion. Is the person standing upright because the load pressure is nearly equal to the person’s body weight? Is the person sitting because there is no load pressure and, therefore, the foot relaxes? The engineers developed the algorithms that determine those states by using the various information obtained in the gait lab. In fact, the very engineers responsible for the design of the Magellan foot occasionally serve as test pilots in the gait lab, wearing a walking boot that can be fitted with any prosthetic foot. (See Figure 3) In this way, the engineers get a feel for what the objective Vicon data defines as the motions and forces on the foot.

The researchers now can obtain information to inform the control algorithm in just five steps, literally. This works equally well with someone with limb loss as it does for the engineer wearing the microprocessor-controlled foot attached to the walking boot. Their action propagates parameters into the control algorithm, which maneuvers the foot just as the person would like it to move. “It’s very consistent, and you can predict what the foot is going to do,” says Orendurff. The researchers then verify the five-step data by examining the gait lab biomechanical data from the Vicon system as a sort of check and balance, analyzing the way the person walks with the prosthetic in question.

Using the gait lab information in this way, the Orthocare group is able to generate scientific studies to show that the device is safe, reliable, and effective. “We create a template so that data from every person who comes in during testing gets fed into the template and we can use that information for analysis,” explains Orendurff. Trials using the gait lab setup produce the vital, scientifically accurate data Orthocare needs.

To this end, Orendurff calls his team an “evidence-based group,” meaning it just doesn’t develop technology for technology’s sake; rather it also puts that technology through its paces in the gait lab, so it has clinical evidence to back up the claims that its devices function once the product is developed, tested, and refined. “The setup enables us to back up our claim that our component works well, that it helps the person walk better, and does what we expected it to do, and what it is supposed to do,” he explains. “If there are supposed to be certain forces, the Vicon system tells us we have those forces present.”

The researchers are continuing this extensive data-gathering process for a peer-reviewed scientific publication that offers further evidence that the innovative prosthesis is indeed safe and effective. Insurers need this published evidence, Orendurff points out. Patients from Seattle O&P often volunteer to participate in product development tests or in formal scientific studies with protocols. The research group now can obtain a complete gait analysis by the time a volunteer is ready to leave the building. Not long ago, it would have taken hours to post-process the information, but advances in the technology at the laboratory have made the procedure faster, better, and more accurate.

“We could not have gotten to the point we are at now without the precise data from the gait lab,” says Orendurff. “It would have taken us much longer to validate the information in the testing phase. We don’t use anywhere near the same amount of information [for the validation stage]; the data here is a small sliver of what is available from the gait lab, but it is enough to validate that the sensors are working and the device is performing as it should. And now that the motion capture technology has helped us validate that the data collected by the prosthetic foot in the lab is correct, we can collect data from real-world settings and be confident the real-world data is valid.”

Even though all this intricate data is produced through technical means, the process still requires a human touch—experts, such as clinicians, engineers, and gait pathology experts—to interpret the information and know what it means. And for many people suffering the loss of a limb, what this means is finding a better way to walk.

The concept of the Magellan microprocessor foot/ankle system was acquired by Ottobock and will be available in the near future. It may have taken 25 prototypes, but the researchers finally are ready to take their best foot forward.

This article was written by Jeffrey Ovadya, Sales Director, Vicon LA, Los Angeles, CA. For more information on Vicon, visit http://info.hotims.com/55588-166 . For more information on Orthocare Innovations LLC, Mountlake Terrace, WA, visit http://info.hotims.com/55588-167 .


Medical Design Briefs Magazine

This article first appeared in the April, 2015 issue of Medical Design Briefs Magazine.

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