The i-LIMB: Revolutionizing the Evolution

John German, MEd, opens his hand. He makes a fist. He rotates his thumb. He lifts only his middle finger. The crowd laughs.

This group of people has gathered to watch German, a medical device representative from Altoona, Pa., show off his new hand, the i-LIMB Hand from Touch Bionics. He has grown accustomed to people reacting to his prosthesis in this way.

“I have two daughters, 12 and 14, and … they think it is amazing, and they will show their friends,” he said. “They will say, ‘Check out my dad’s new hand,’ and their friends will be freaked out because they didn’t know it was an artificial hand to begin with.”

O&P Business News takes a look at this new technology to enter the prosthetic industry.

The device

i-Limb HandThe i-LIMB Hand is a myoelectric prosthetic device for upper extremity amputees – the first fully articulating hand with five individually powered digits. According to information from Touch Bionics, the i-LIMB Hand uses a traditional myoelectric signal, generated by muscles in the patient’s residual limb, to open and close the device. Each finger is controlled by software that enables it to stall when a defined level of resistance has been reached, providing a natural grip posture.

The prosthesis runs on a standard rechargeable lithium ion battery and lasts for 2 to 3 days when fully charged.

In late January, company officials announced the incorporation of the company in the United States as Touch Bionics Inc. Currently basing operations in Boston, the announcement followed the company’s opening of its new headquarters and development and manufacturing facility in the United Kingdom earlier in the month. More than 70 patients around the world have received this new device since its introduction, and that number is rising – the company expects to reach its 100 patient milestone by the end of February. Both new and veteran amputees, like German, are eager to try out the technology.

“With 20 years of using the old technology, I saw a lot of the changes in that technology over time, and really, there were only a few changes – for example, wrist rotation and proportional control,” German said. “That is pretty much all that evolved over that period of time, so there wasn’t a lot going on in the field.”

German considers the advanced technology to be the difference between evolution and revolution.

“There were some evolutionary changes [in the past], but the i-LIMB Hand is clearly a revolutionary change,” he said.

The need for this type of revolution is not new, however.

Stuart Mead, chief executive officer of Touch Bionics, said the requisite for a device such as the i-LIMB Hand dates back to the thalidomide disaster in the 1960s, in which mothers taking thalidomide for morning sickness had babies who experienced a host of birth defects, especially those affecting the limbs. The Scottish government put aside funds to develop solutions for these young patients as they grew up. In 2003, the United Kingdom’s National Health Service created a spinoff company for the intellectual property that had accumulated over the years – and Touch Bionics was born.


i-LIMB Hand
The i-LIMB is a myoelectric prosthetic device for upper extremity amputees – the first fully articulating hand with five individually powered digits.
All images reprinted with permmission of Touch Bionics.

The other devices German used over the years were unable to accommodate certain tasks because of their limitations. He is accustomed to devices with the first two fingers attached to each other, only meeting the thumb in opposition, and two “dummy tagalong” fingers.

“The i-LIMB Hand can fit the task or fit the object of what you are doing, [whereas] with the older hand, you had to make your body or your arm or shoulder kind of move to meet the task, because there was only one grip available,” German said. “Now the grips are infinite. There are an unlimited number of grips that you can perform with the i-LIMB Hand.”

The key to this new technology, Mead said, is the motor inside each finger, where a human finger bone is located.

“Each digit is powered, including the thumb, and we have powered two articulations,” he said. “The motor directly powers the first articulation in the MCP knuckle, and the second articulation is powered by a belt, driven by that articulation much in the same way as a tendon works in our own hand.”

This allows patients the ability to wrap the prosthetic hand around objects, unlike existing technology. Another feature new to the i-LIMB Hand, the thumb rotates through different grip positions in the same way a human thumb does.

“What makes human beings so dexterous is we have an opposing thumb, and we have managed to replicate that with our hand,” Mead said.

Patients choose from a key grip, a power grip, a precision grip and an index point.

“All those grips are available with our hand, as much as they are with a human hand, because you can move the [i-LIMB] thumb through different positions,” he said.

The i-LIMB Hand also contains a computer in the back of the hand, which continuously monitors all of the digits and senses when one finger has stalled, signaling its grasp on an object. At that point, it shuts down power to that finger, but allows the other fingers to continue until they also come to stall.

“Which means it will conform to whatever shape of object you put into it,” Mead said. “It shapes around a ball, or it shapes around a cup, or it shapes around any object like our own hand does. This hand will shape to it, even though you’re only using two inputs from the myoelectric signal.”


The i-LIMB Hand has a human shape.

“Anatomical accuracy is important to amputees,” Mead told O&P Business News. “The fact it actually looks like a hand, rather than a mechanical object, and moves like a hand is important to the user. Whatever the professional community is looking for in a new device, it is our experience with users wearing the hand for the first time that tells us we are on the right path – the emotional reaction is compelling. The challenge we face now is articulating the psychological benefits to the insurance community.”

German agrees, and enjoys the hand’s subtlety.

“The older hands were not physiologically shaped properly,” he said. “They didn’t move like a real hand does.

“There is a component of concept, I would say, especially for people who are concerned about how they might look or appear to others.”

For this reason, Touch Bionics set out to create a prosthesis that closely resembles a human hand with or without cosmetic covering.

The i-LIMB skin is a thin layer of semi-transparent material that covers the device, protecting it from dust and moisture. This covering provides a grip surface for patients, but still reveals the mechanical aspects of the hand.

In addition, Touch Bionics has partnered with cosmesis companies LIVINGSKIN and ARTech Laboratory for patients who want a more natural looking prosthesis.

“This hand can help a lot with the external accuracy of reinstating the look and function of a missing hand, but also the internal part of how a person might feel about themselves, because they have something that looks more normal and real,” German said.

Future technology

i-LIMB Hand
Patients have the ability to wrap the prosthetic hand around objects. Also, the thumb rotates through different grip positions in the same way a human thumb does.

“Think about what you do in the day, and how much you use your hand,” said German. “It is incredible to think how many times you open and close your hand, things that you grab, things that you do. It is a breakthrough to know that, whatever it is that you are doing, there is a grip that will work for that task.”

Like other O&P manufacturers, Touch Bionics sees where the technology is headed. But the biggest limitation of the i-LIMB Hand, according to Mead, is that the number of inputs from the amputee restricts the number of actions the limb can complete.

“The mechanics are limited at the moment by the input signals,” he said. “That is an area that we are working on, and that is a critical area for us to get right for the future.”

He expects a number of improvements in this type of technology over time, however.

“We are already trying to do things with software, but we also have constraints above what nature gave us to work with. Direct interaction with nerves is a tough challenge,” Mead said.

Patients may be the best means of furthering that technology. German urges patients to research the available prostheses, request the technology that will best help them and, most important, he said, not to settle for less.

“Because an insurance company or another type of payer is not going to pay for X product – that is not good enough,” German said. “People need to appeal and they need to fight and they need to demand the technology that is going to make them most functional, because the whole purpose of having a prosthesis is to restore a person to the highest level of physical function possible.

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Stephanie Z. Pavlou is a staff writer for O&P Business News.

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