Get a Grip
Monday January 23, 2012
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After Roger Thomas lost his right hand 30 years ago while serving in the U.S. Marine Corps, he kept recalling a scene in "The Empire Strikes Back" in which Luke Skywalker receives an artificial hand. Thomas was using a body-powered prosthesis that served him well enough but looked "like a lobster claw."
"I thought, 'I need to keep the muscles in my arms in shape'" in preparation for when "Star Wars" visions would become reality, said Thomas, 49, who lives in Tampa, Fla. In the meantime, he has the closest thing current technology can give him — the I-limb Ultra, a myoelectric prosthesis made by Scottish company Touch Bionics.
Using electrodes that transmit signals from remaining muscles in the wrist or arm, motorized bending digits, a rotating thumb and software that allows users to program different positions, the device comes the closest of any prosthesis so far to mimicking the motion and abilities of a real human hand, said Danny Sullivan, communications manager for Touch Bionics. "It's mechanical, electronic and software engineering all coming together," he said. The prosthesis can be covered with a silicon glove that comes in clear, black or 10 different skin shades.
"It looks so lifelike — it really looks like a hand," said Laura Reed PT, CHT, a clinical coordinator for Touch Bionics who lives in Arlington Heights, Ill.
Myoelectric prostheses, first introduced in 1964, use electrical impulses from remaining muscles in an amputated limb to control movement. Electrodes in a socket rest against the skin of the remaining arm, and the prosthesis is plugged into the socket. By imagining they are moving their hands, users control muscle movements to send electrical messages to a small motor in the prosthesis, telling it what to do.
New era in prostheses
For many years, electronic prostheses resembled claws, with a pincer between the thumb and forefinger and a three-fingered grip that allowed the user to open and close the device, Sullivan said. The fingers didn't bend, and the thumb did not rotate. The grip was awkward and didn't allow for small-motor tasks. It had only one strength setting, which could shatter delicate objects.
"It was difficult to do things like hold a coffee cup," said Lee C. Keneston Jr. of Albany, N.Y., who used one of the earlier myoelectric prostheses until he got an I-limb several years ago. "The hand didn't seem to be able to open wide enough." There were no fingers to curl around and support the mug, he said.
In 2007, Touch Bionics launched its first I-limb Hand, with a rotating thumb, palm and five bendable, motorized digits. The new device mimicked some of the movements of an actual hand and allowed a much greater range of gripping options, Sullivan said. Users train their muscles to trigger up to four grips, allowing them to point a finger to type on a keyboard, hold a wine glass, pick up small objects in a precision grip or manually rotate the thumb to push against a forefinger to turn a key. Sensors in the fingers automatically stop when they have applied enough pressure, but a pulsing feature introduced in a later version allows users to gradually increase their grip strength to carry a heavy bag or hold a shoelace more tightly.
Thomas, whose hand was severed near the wrist in a mortar explosion, did not use a myoelectric limb because it required a battery too large to fit into a socket that would fit his arm. He also did not believe the myoelectric models offered any great improvement over his body-powered prosthesis, which he wore attached to a shoulder harness. But when his shoulder started showing signs of repetitive stress injury about four years ago, a prosthetist suggested an I-limb device, which had just come out with a smaller battery.
Thomas said he finds it easier to hold a bottle or a can of soda and remove heavy objects from overhead shelves. Keneston said he likes that he can hold a wine glass, easily push his hand through a sleeve and carry a mug of coffee while opening a door.
The new software also offers a variety of games and exercises for users to learn to use and control the hand. The greatest challenge in learning to use the hand was mastering the muscle patterns needed to form various grips, Thomas and Keneston said. The most difficult command for both was the co-contract, which is sometimes described as a finger-flicking motion.
Therapist learning curve
For therapists, the greatest challenge often is developing confidence using the technology, Reed said. "They might not feel confident in training the patient." Touch Bionics offers support, education and protocols for any therapist working with patients who use its products, she said. "We want this to be a positive outcome for the patient."
The prosthesis is designed for everyday living tasks, not for jobs involving heavy equipment, such as farming, nor extreme sports such as rock climbing, Sullivan said. It can't be submerged in water — when Thomas goes sailing, he uses his body-powered hand. Though a user can push a single set of keys on a piano or keyboard simultaneously — useful for computer commands such as control-alt-delete — the fingers can't move independently at once to play sonatas or type with more than one digit.
The cost of the hand varies widely from patient to patient, depending on socket manufacturer, fitting and training, Sullivan said, but the entire package can run about $100,000. Most insurance companies cover most of the cost, but the hand is not covered by Medicaid.
The I-limb still is a long way from matching the function of a real human hand, its users and developers say. Prosthesis engineers are working on ways to make fingers move together and independently, increasing the degree of control and range of motion, and to connect it to neural pathways to allow sensation and feedback. Other companies have introduced their own versions of realistic myolelectric hands with five moveable fingers and rotating thumbs. Researchers in Europe are working on a prosthesis called the SmartHand, which they say offers users some sensation.
"I will not be happy with the hand until it's the Luke Skywalker hand," Thomas said. "The saddest part for me is that I'm older and I may not get to see it." But he's certain the technology will be there for those who now lose a hand at the same age he did — 21. "They'll get to see or wear a Luke Skywalker hand." •
Cathryn Domrose is a staff writer.
"I thought, 'I need to keep the muscles in my arms in shape'" in preparation for when "Star Wars" visions would become reality, said Thomas, 49, who lives in Tampa, Fla. In the meantime, he has the closest thing current technology can give him — the I-limb Ultra, a myoelectric prosthesis made by Scottish company Touch Bionics.
Using electrodes that transmit signals from remaining muscles in the wrist or arm, motorized bending digits, a rotating thumb and software that allows users to program different positions, the device comes the closest of any prosthesis so far to mimicking the motion and abilities of a real human hand, said Danny Sullivan, communications manager for Touch Bionics. "It's mechanical, electronic and software engineering all coming together," he said. The prosthesis can be covered with a silicon glove that comes in clear, black or 10 different skin shades.
"It looks so lifelike — it really looks like a hand," said Laura Reed PT, CHT, a clinical coordinator for Touch Bionics who lives in Arlington Heights, Ill.
Myoelectric prostheses, first introduced in 1964, use electrical impulses from remaining muscles in an amputated limb to control movement. Electrodes in a socket rest against the skin of the remaining arm, and the prosthesis is plugged into the socket. By imagining they are moving their hands, users control muscle movements to send electrical messages to a small motor in the prosthesis, telling it what to do.
New era in prostheses
For many years, electronic prostheses resembled claws, with a pincer between the thumb and forefinger and a three-fingered grip that allowed the user to open and close the device, Sullivan said. The fingers didn't bend, and the thumb did not rotate. The grip was awkward and didn't allow for small-motor tasks. It had only one strength setting, which could shatter delicate objects.
"It was difficult to do things like hold a coffee cup," said Lee C. Keneston Jr. of Albany, N.Y., who used one of the earlier myoelectric prostheses until he got an I-limb several years ago. "The hand didn't seem to be able to open wide enough." There were no fingers to curl around and support the mug, he said.
In 2007, Touch Bionics launched its first I-limb Hand, with a rotating thumb, palm and five bendable, motorized digits. The new device mimicked some of the movements of an actual hand and allowed a much greater range of gripping options, Sullivan said. Users train their muscles to trigger up to four grips, allowing them to point a finger to type on a keyboard, hold a wine glass, pick up small objects in a precision grip or manually rotate the thumb to push against a forefinger to turn a key. Sensors in the fingers automatically stop when they have applied enough pressure, but a pulsing feature introduced in a later version allows users to gradually increase their grip strength to carry a heavy bag or hold a shoelace more tightly.
Thomas, whose hand was severed near the wrist in a mortar explosion, did not use a myoelectric limb because it required a battery too large to fit into a socket that would fit his arm. He also did not believe the myoelectric models offered any great improvement over his body-powered prosthesis, which he wore attached to a shoulder harness. But when his shoulder started showing signs of repetitive stress injury about four years ago, a prosthetist suggested an I-limb device, which had just come out with a smaller battery.
Thomas said he finds it easier to hold a bottle or a can of soda and remove heavy objects from overhead shelves. Keneston said he likes that he can hold a wine glass, easily push his hand through a sleeve and carry a mug of coffee while opening a door.
The new software also offers a variety of games and exercises for users to learn to use and control the hand. The greatest challenge in learning to use the hand was mastering the muscle patterns needed to form various grips, Thomas and Keneston said. The most difficult command for both was the co-contract, which is sometimes described as a finger-flicking motion.
Therapist learning curve
For therapists, the greatest challenge often is developing confidence using the technology, Reed said. "They might not feel confident in training the patient." Touch Bionics offers support, education and protocols for any therapist working with patients who use its products, she said. "We want this to be a positive outcome for the patient."
The prosthesis is designed for everyday living tasks, not for jobs involving heavy equipment, such as farming, nor extreme sports such as rock climbing, Sullivan said. It can't be submerged in water — when Thomas goes sailing, he uses his body-powered hand. Though a user can push a single set of keys on a piano or keyboard simultaneously — useful for computer commands such as control-alt-delete — the fingers can't move independently at once to play sonatas or type with more than one digit.
The cost of the hand varies widely from patient to patient, depending on socket manufacturer, fitting and training, Sullivan said, but the entire package can run about $100,000. Most insurance companies cover most of the cost, but the hand is not covered by Medicaid.
The I-limb still is a long way from matching the function of a real human hand, its users and developers say. Prosthesis engineers are working on ways to make fingers move together and independently, increasing the degree of control and range of motion, and to connect it to neural pathways to allow sensation and feedback. Other companies have introduced their own versions of realistic myolelectric hands with five moveable fingers and rotating thumbs. Researchers in Europe are working on a prosthesis called the SmartHand, which they say offers users some sensation.
"I will not be happy with the hand until it's the Luke Skywalker hand," Thomas said. "The saddest part for me is that I'm older and I may not get to see it." But he's certain the technology will be there for those who now lose a hand at the same age he did — 21. "They'll get to see or wear a Luke Skywalker hand." •
Cathryn Domrose is a staff writer.
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Monday January 23, 2012