Monday, October 12, 2009

Not Just For Cellphones: Prosthetics Get Bluetooth

If you were asked what a pair of prosthetic legs has in common with a cellphone, you would probably say “nothing.” And you would have been right—until recently.

Prosthetic legs have been made from every material from wood to plastic to metal. With each generation prosthetics experts try to make the limbs look and behave more naturally. At the same time the devices have become more complex. Now an Iceland-based orthopedics and prosthetics company, Ossur, has significantly raised the bar. Two factors make the company’s new prosthetic different from any of their predecessors. Their power knee uses artificial intelligence to sense and make adaptations for pressure and angle changes as the amputee moves. In itself computerization isn’t a giant leap away from where other prosthetics were headed. But add this to the Bluetooth device on the ankle, and now we’re dancing a new step. This Bluetooth device coordinates the movements of one leg with the movements of the other.

The technology was originally designed to be used on single leg amputees. In its originally conceived configuration, the 10-pound prosthetic would mimic the movements of a flesh-and-blood leg. In the case of a double amputee, the Bluetooth devices need to “sync up” with each other. In either case, the first step or two the user takes is usually pretty sloppy.

Users of older forms of prosthetic tire easily. It takes a great deal of effort, and a good bit of contraction from potentially damaged thigh muscles, to move a hunk of wood or a shaft of metal. But motors built into these new Bluetooth devices do much of the work. As a result, users can do more than ever before without expending nearly as much energy. There are, of course, challenges that need to be addressed with any new technology and these new prosthetics are no different. Cost is chief among the hurdles. Up until now, a top-of-the-line set of prosthetic legs ran about $20,000. The Ossur device comes with a price tag hovering around $120,000. That’s outside the price range affordable by the typical user. Furthermore, it’s been difficult to adjust the strength of the motors that help to propel the leg.

While these motors do save the user much-needed energy, on several occasions they have produced undesirable effects. Current users have reported such things as excessively strong knee jerks when trying to stand. And, because of the built-in power supply, this new device has to be charged overnight. That means going out for a long night on the town may mean either taking off the device at some point in time or leaving it at home altogether.

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