Northern Lights: Bright Ideas in Canadian Research

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Dr. Stephen Naumann, director of the Rehabilitation Engineering Department at Bloorview MacMillan Children's Centre, Toronto, Ontario, discussed some current projects.

Electrical Elbow

Dr. Naumann's department is currently developing an electrical elbow for teens or petite women, designed to swing freely in full extension with no rotation.

In pursuit of a market debut early next year, Naumann is meeting regularly with clinical colleagues and engineers. He reported that the research itself is completed, but the mold-making process will likely require another six months of work. Consumer feedback will continue to be solicited during this period as well.

Variety Ability Systems, Inc. (VASI), Toronto, which manufactures and markets prosthetic and orthotic devices for children, was established in the early 70s to fill a need for production and consumer feedback. Although the market for these items was minimal and production on such a small scale was neither cost-effective nor profitable, VASI nonetheless began production, relying largely on donor funding for the benefit of children whose lives would be enriched by the possession of such a device. Today, VASI continues to serve as a manufacturing and marketing partner, supporting the research efforts of the Children's Centre and making their O&P advances more readily available to the public.

Soft UE Socket

Also in development is a soft silicone upper limb socket. Such sockets are already used for certain sports prostheses. They allow the socket to be simply peeled on and off the stump.

"We can't afford the hazard of exposed or broken wires," Naumann said. "In order to remotely detect what the muscle is doing, we place microphones at the distal end of the stump. Even at that distance, a tiny $10 microphone picks up the noise of the muscle contracting." The problems they have encountered have been created by the microphone's ability to hear too well and pick up too much interference-potentially allowing an inappropriate noise-like an unexpected jar or bump-to trigger it. Their solution is to electronically filter out this noise.

"We're about a year to a year and a half away from introducing this to the public," Naumann said. "We're trying to come up with a kit that prosthetists can easily incorporate."

Pediatric Knee Joint

There's also a knee joint for young children, in advanced development stages, which will possibly be available through VASI within the year. "Some such knees are already available," said Naumann, "but ours will be simple, more robust, and still retain the same features. It will be smaller and weigh less, so it can be fitted to smaller children."

Improved Standers

Naumann's group is active with research on the orthotic side, as well.

"Parapodiums or standers for children with spina bifida have been around since the 70s," he pointed out. "We're trying to get more weight-bearing-this not only helps to strengthen bone and potentially prevent osteoporosis, but it also prevents bladder problems and allows children to stretch and reach things better."

Current models allow a swing walk, but orthotists have concerns regarding the prohibitive expense of such standers, which lack adjustability to accommodate the child's growth. Most insurance plans will not cover the cost of replacement standers as the child outgrows them.

Naumann's three sizes of standers allow multiple modifications. "Just by loosening and tightening a few bolts you can make adjustments," he said. "Even if the child's knees are not at the same level, or if contractures prevent a child from straightening up, you can adjust for these conditions."

The new standers should be available from VASI in about six months.

New Materials for AFOs

New materials are also being developed for AFOs, Naumann said. Currently the fitting process for polypropylene AFOs is very labor-intensive, involving casting, molding, vacuum-forming, and custom heat-adjustments.

Naumann's researchers worked with Dr. Paul Santerre in the dentistry department at the University of Toronto and Dr. Shiping Zhu at McMaster University, Hamilton, Ontario, to develop a composite that can be cured by light rather than heat. This project has been underway for a number of years, but with a resin now available that "works very well," Naumann expects to complete the project within the next two years. "The materials we first used were toxic," he said. "What we have derived now is even safer than the materials dentists put in your mouth."

Myoelectric Controls Research

Cennet Iley, age 9, enjoys activities in her stander. Photo by Fraser Shein, PhD, PEng, Bloorview MacMillan

Bernie Hudgins, PhD, PEng, Director of the Institute of Biomedical Engineering at the University of New Brunswick, cites the Institute's venerable history of research concerning myoelectric control systems for powered upper-extremity prostheses-award-winning studies which have led to the Institute's current work from a new 14,000 sq ft on-campus facility, R.N. Scott Hall, just christened in ceremonies on May 24.

Although they were first designed before World War II, powered upper-extremity prostheses weren't introduced for popular use until around 1965, Hudgins said. At that time, the Institute was involved in the first all-Canadian fitting of myoelectric prostheses. The Institute also was first to develop the three-state system that allowed people with only one muscle control site to use varying amplitudes to control their prosthetic arm.

Today, the Institute has diversified its areas of investigation into telehealth, biological signal acquisition, and motion analysis, according to Greg Bush, BA, CP (c), research prosthetist at the Institute. Bush has also chronicled the Institute's current research activities in a story for Alignment, the Canadian Association of Prosthetists and Orthotists (CAPO) 2002 Yearbook.

Research prosthetist Greg Bush, BA, CP(c) demonstrates a new control system to client Daryl Arsenault.

According to Bush, the Institute's new facility is equipped with a VICON motional analysis system that allows closer examination of "various aspects of human motion, particularly upper limb function...the new six-camera system will allow 3-D tracking of these complex functions (and) ...permit comprehensive analysis of function and posture when using an upper extremity prosthesis."

An Institute research team has been working for eight years to perfect an "intelligent" control system for upper-limb prostheses which has three degrees of freedom, with elbow, hand, and wrist all operated myoelectrically. "Since 1997," Bush said, efforts "have focused on making the control more fluid and the control interface between the prosthesis and limb more natural. This will provide a dynamic cosmetic appearance to the prosthesis, so that it looks natural in function with the actions being less robotic."

Hudgins agreed, noting that the project's goal is to make the selection of prosthetic function more instinctive for the subject. The new controller uses a specialized computer embedded in the prosthesis which "learns" the characteristics of the myoelectric signals of an individual much as the brain recognizes familiar patterns. Recent advances in microprocessor technology have expedited their progress by delivering high performance while requiring minimal power.

"Our control systems have now progressed beyond the capabilities of the components currently available," he pointed out.

Hudgins observed that there are a limited number of above-elbow amputees available to test their sophisticated new control system. Cost has been another cause of delay; locating sources of funding has been a major stumbling block. For an above-elbow amputee, a typical cost of fitting a myoelectric prosthesis is in the $27,000 (Canadian) range. Additionally, "We can't fit the limb with an experimental control system until the patient has a duplicate backup system," said Hudgins-which further escalates the costs. And unfortunately, he pointed out, it is difficult to do a cost-benefit analysis without testing the system on a patient who can demonstrate those benefits.

"Funding is the only thing stopping us at this point. We're ready to fit the system on patients and pursue clinical trials; we've already tried an in-house fitting. But it still looks like a long way to our final destination. The control system is ready to go; it can now switch smoothly between sequential movements. Simultaneous movement-such as bending the elbow while rotating the wrist-is on the horizon, but won't be a reality for another five years."

The fact that not every upper-extremity amputee is a candidate for trial is another complication, Hudgins pointed out. "Depending on their injury, some amputees may have very little muscle remaining. And while some people are capable of making optimum use of even a small amount of muscle, some are unable to generate the differing signals necessary to utilize the controller."

Other factors may also disqualify a candidate: farmers and fishermen, for example, function in a myoelectrically unfriendly environment. Other Institute projects include innovative approaches to socket fitting, new comfort-conscious ideas regarding suspension systems, and an interactive "virtual arm"-brainchild of the Institute's associate director, Kevin Englehart, PhD, PEng.

A computer-generated model of the prosthesis and its environment can be simulated in order to evaluate control strategies prior to fabrication of the definitive prosthesis. The system allows researchers to evaluate how well a control configuration works for a patient, and to fine-tune it before actually making the costly limb.

The system may be a valuable aid in rehab therapy, as well, allowing new amputees the opportunity to learn to control the various functions of the on-screen virtual arm, thus getting a head start on training prior to being fitted with the prosthesis.

"We will be able to have the client doing active, daily living tasks in this virtual space," said Englehart in Alignment. "We'll also have the ability to explore things you'd never be able to test on existing prosthetic devices."

The virtual arm prototype already exists, and the system should be ready for widespread use within a year, Hudgins anticipates.

The Institute's latest developments will be examined at the Myoelectric Controls and Powered Prosthetics Symposium (MEC 2002), hosted by the University of New Brunswick August 18-23. For further information, visit www.unb.ca/bio-med

Judith Otto is a freelance writer based in Holly Springs, Mississippi.

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