Affordable prosthetic knee joint

Jan Andrysek balances a prosthetic leg on the arm of his chair, then applies downward pressure to make the front of the foot push forward, causing a joint in the device to bend just like a natural knee.

TORONTO — Jan Andrysek balances a prosthetic leg on the arm of his chair, then applies downward pressure to make the front of the foot push forward, causing a joint in the device to bend just like a natural knee.

The prototype black metal knee joint may look like some kind of automobile part, but the biomedical engineer hopes the simple device will give the gift of mobility to untold numbers of people in developing countries who have lost a leg to amputation.

Cost is the reason.

With an estimated target price of $50 to $100, the joint is an affordable component that will allow a static prosthesis — made up of a socket, a metal post called a pylon and an artificial foot — to move in a rhythm that more closely mimics that of a natural leg.

There’s a need “for an inexpensive knee joint — inexpensive sort of equates to accessibility — because in many countries people don’t have the money nor are there funding systems in place to allow them to be able to purchase these devices,” says Andrysek of Holland Bloorview Kids Rehabilitation Hospital in Toronto.

“And in countries such as Canada, these devices can cost typically, to put a prosthesis together, you’re looking in excess of $5,000 — and it can go up to $50,000.

“So these are very expensive devices. We’re fortunate in Canada to have funding systems in place that cover most of those costs for the individuals. But that is not the case for most countries around the world.”

Haiti is one glaring example of a country desperate for affordable, functional prostheses to help the tens of thousands of amputees who suffered traumatic injuries in the 2010 earthquake.

“In counties such as Cambodia and Myanmar, you have many postwar injuries resulting from landmines that haven’t been cleared or are even still being laid,” he says. Blast and other injuries in such war-torn countries as Afghanistan have also left a population of amputees in need of prosthetics.

Andrysek has spent about six years developing the knee joint with a team at the Bloorview Research Institute. He was recently awarded a $100,000 grant by the non-profit organization Grand Challenges Canada after being named one of its “Rising Stars in Global Health.”

“This work really came from some of the initial work we did with the children here to try to develop a little joint for kids,” he says. “At that time, our two criteria were to make it very functional, because these are active kids and they want to be able to do a lot of things, but at the same time it has to be very durable.

“And it turned out similar criteria (would be needed) for developing countries. These are generally healthy individuals who can be very active and they require devices that would allow them that function.”

One key consideration is environment: the knee joint controlling the movement of the prosthesis must be able to withstand the kinds of walking surfaces that are common to many developing countries.

That could mean mountainous terrain, rock-strewn surfaces or pitted and uneven ground that can be problematic even to those who aren’t amputees.

“The challenge in that is you’re trying to design the prosthesis to have the same type of control that our human muscles have,” says Andrysek, explaining that a built-in locking and unlocking mechanism in the joint automatically responds to pressure, or “loading patterns,” exerted through the foot.

“And that control means that the leg is stable. If the person puts weight on it, it’s securely underneath them, but at the same time it can easily go into the natural motion that we see walking, which is the knee bending.”

For now, Andrysek says he is focusing on a knee joint for adults because those for children would have to be made in several sizes to match different ages, although his team plans modified versions that are smaller and lighter for kids as part of their future research.

“We think that the technology will serve both children and adults well.”

During the design phase, which followed a lengthy period studying the mechanics of the human gait, the team produced three different prototypes. The current one is what he calls “something between a prototype and a product.” The researchers have invested money in making moulds, so the knee joints can be make out of plastic, he says.

“That allows us to make these parts very inexpensively, so we can injection-mould the three main parts of the knee for about $15, and that’s a large part of our ability to make these knees affordable.” Andrysek says Bloorview hopes to team with a manufacturer to produce the knee joint. “We’re just getting to the stage of trying to work with partners who could facilitate that part of it. And the big thing is the distribution — how to get these knees to those different countries.”

The knee joint is now being tested by the International Red Cross, which has project sites in about 60 countries, he says. “They will be evaluating it over a year, and depending how it goes, they would be a very good partner to get this technology out there to those who need it.

“As a researcher, one of the most rewarding things is when you can actually take a project from the beginning, with the conceptualization, and actually get to a point where it gets out and starts having an impact on people’s lives and people’s health.”

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