The science of rebuilding humans after war has always delivered benefits to civilians sidelined by disability, and progress has accelerated in recent years with the introduction of bionics. This specialty – the merger of bioengineering, electronics and nanotechnology with sciences related to the nervous system – has shaped the design of human replacement parts so profoundly that expressions like “the disabled” and “the handicapped” could one day fade into obscurity.
Very little seems out of reach. A Swiss research team aims to recreate the intricacies of the human brain within a decade. The breakthrough would represent only a blip on a very long continuum. Excavations of ancient sites and documents show that prosthetic design was advanced as far back as the pharaohs: archeologists recently found a mummy with an artificial toe of wood and leather.
The chain of prosthetics breakthroughs includes the artificial pacemaker. Surgeons implanted the first electronic devices for stimulating or regulating contractions of the heart muscle in the 1950s, but they had been experimenting even earlier with pacemaker technology. The chain also records breakthroughs in the design of replacement limbs and appendages, and in the science of growing human organs and cells.
Building And Rebuilding Humans
Fictional bioengineers created the Cylons, the superhumans of the Battlestar Galactica era. Their real-life counterparts of today strive only to restore full functionality to impaired humans, yet the goal of a superhuman class is no longer fanciful. The tactical advantage of sending bionic soldiers into battle was recognized long before Cylons terrorized Earthlings. Funding from DARPA (Defense Advanced Research Projects Agency) helps to keep research into exoskeletons and orthoses moving at a military pace. These are devices, acting in series or in parallel to a human limb, that are designed to augment strength and endurance.
Soldiers won’t be the only beneficiaries. HAL (Hybrid Assistive Limb) and HULC (Human Universal Load Carrier) may one day help the infirm lift and carry and destroy the market for wheelchairs and walkers. HAL’s developers say they have received many requests for the devices from people with brain and spinal injuries.
HAL, a motor-driven metal exoskeleton strapped to the legs to power leg movements that was invented by Yoshiyuki Sankai of the University of Tsukuba in Japan, was featured in the April 2005 edition of New Scientist magazine. Two control systems interact to help the wearer stand, walk and climb stairs. Bioelectric sensors attached to the skin on the legs monitor signals transmitted from the brain to the muscles. When the user intends to stand or walk, the nerve signal to the muscles generates a detectable electric current on the skin’s surface. Sensors pick up the current and send it to a computer worn in a pouch. The computer translates the nerve signals into signals of its own for controlling electric motors at the hips and knees of the exoskeleton.
The system activates itself automatically once the user starts to move. HAL’s sensors record posture and pattern of motion during the first walk, and stores the information in an onboard database for later use. When the user walks again, sensors alert the computer, which recognizes the movement and regenerates the stored pattern to provide power-assisted movement. The actions of both systems can be calibrated according to a particular user’s needs, such as providing extra assistance for a weaker limb.
An upper part of HAL assists the arms, helping the user lift up to 80 pounds more than he or she could manage unaided. Hal’s weight and bulk are an issue, but the inventor is whittling down both with each model.
HULC, developed jointly by aerospace company Lockheed Martin and Berkley Electronics in California, gives a soldier the ability to carry up to 200 pounds without seriously impeding mobility. The hydraulic-powered exoskeleton has almost reached the market.
An End to Walkers and Wheelchairs?
The comprehensive history of prosthetics in the December 2007 issue of In Motion magazine noted several “firsts” on the continuum – Pieter Verduyn’s non-locking below-knee prosthesis of 1696, and Dr. Douglas Bly’s artificial leg with a curved ankle of 1868. The pegleg of hapless Captain Ahab, who was last seen in the maw of great white whale Moby Dick in the novel by the same name, is fairly representative of the level of sophistication of leg prosthetics before the mid 19th Century.
Some of today’s designs are so sophisticated that, like HAL and HULC, they give the wearer advantages. The 29 Jul 2008 edition of Wired magazine features Oscar Pistorious, a double amputee who is considered one of the fastest men in the world. He uses carbon fiber-composite legs with curved blade-shaped feet and doesn’t define himself as disabled. The International Association of Athletics Federations (IAAF) agrees, but when Pistorius requested to participate in the trials for the Beijing Olympics, he was flatly rejected. Why? According to a Time magazine article about Pistoriou, ‘more energy is returned to [his] upper legs from his blades than from ankles and calf muscles and . . . uses less oxygen.’ He was deemed too physically advanced to compete against ‘non-disabled’ men. The technology has allowed him to catch up with people with legs. In 2008, he challenged the IAAF ruling and won, giving him the right to compete against the non-disabled athletes.
The C-Leg, developed by Otto Bock Healthcare, a German company now established in North America, is a more natural-looking device than Pistorious’ blade runner. The product literature describes it as the first computer-controlled stance-and-swing phase prosthetic knee. “A microprocessor monitors and adapts to the patient’s gait, and various terrains 50 times per second. With traditional prosthetic knee joints, people have to think—and sometimes worry—about each step they take. With the C-Leg, patients move more naturally. They are able to speed up or slow down, cross slope, climbing stairs, or walking on uneven ground.”
Dr. André Seyfarth from the University of Jena pointed out in an article by German newsagency DPA in March 2009 that a giraffe cannot walk like a Dachshund. He wasn’t being facetious. He illustrated the need to give leg prosthetics the ability to mimic the variable and individual gait of the user. For a project named Locomorph, Seyfarth and an international team are researching how to “shape” movement. "We want to understand the mechanical and neuronal communication in the moving leg – in order to copy it," he said.
Researchers from the Biomechatronics Lab at MIT in the United States have patented a bionic foot and ankle. As described in New Scientist in April 2007, it attempts to match the biomechanical behavior of a normal human foot throughout the walking cycle and over a variety of terrain. The limb consists of an artificial shin and foot connected via a powered, rotating ankle joint. A motor within the ankle varies factors such as the angle of the foot, the stiffness of the joint and the force absorbed and released during each step. The prosthetic feet should feel more natural to a wearer and should also adapt to different terrain, such as a flight of stairs, without requiring extra effort.
And scientists from four countries have come together to create what is now being called the Cyberhand. Unlike existing prosthetics, Cyberhand’s five [fingers] will each have independent motors that can be controlled separately. According to team leader Paolo Dario at the Sant’Anna School of Advanced Studies in Italy, Cyberhand users should be sufficiently dexterous to use a pair of scissors. This is a great step forward as even the most elaborate hand prosthetics currently can do no more than grip something – flexing all the fingers at once. The sensors give the user the capacity to feel pressure in the hand. The feedback on the strength of the grip prevents objects from being crushed or dropped.
The Scottish firm Touch Bionics launched the i-LIMB hand in July 2007, describing it as the world’s first commercially-available bionic hand. It is a multi-articulating hand, meaning each finger has its own motor. It has subtle abilities, like a credit-card grip for grasping narrow objects and a power hold for larger objects like coffee mugs. Research on the device began in the United Kingdom’s national health system back in the 1960s.
A prosthetic wrist unit, prosthetic fingers and a full bionic arm are under development at the company.
ITAP (Intraosseous Transcutaneous Amputation Prosthesis), which has reached the clinical trial stage, marks another direction in prosthetics design. Developed by British researchers, it achieves a higher-level of neural interfacing by attaching prosthetics directly to bone. The technique eliminates the chafing, which often comes with the conventional socket prosthetics. According to a BBC news feature about ITAP in July 2006, the special ability of deer to grow antlers directly through their skin inspired the concept. Epidermal tissue anchored to a connecting rod, creating a seal that helps prevent infection.
Advances in subminiturization and high-speed low-power communications have led to various “bed-of-nails” approaches to improving the neural interface between prosthetic devices and amputated or impaired body parts. The Mann Medical Research Organization in California describes itself as a leader in the field, and is developing a device that is set directly into a nerve in an amputee’s stump, allowing the user to control and feel it as if it were his or her own.
Nanotechnology takes miniaturization to the cellular and molecular level, opening ways to even closer cooperation between living tissue and manufactured parts. The ARC Centre for Excellence for Electromaterials Science in Australia is using linked polymer filaments to conduct electricity into living tissues, the cells of which feed back information to microprocessors. The laboratory is also growing nerve cells, an essential part of the effort to restore mobility to people who have been paralyzed by spinal cord injuries and to paraplegics and quadriplegics.
Thinking and Doing
Even more sophisticated neurosensing devices are in development. They enable a user to think an action. In other words, the user thinks and the device does.
In previous research, monkeys and even quadriplegic people people have controlled the movement of cursors on computer screens through electrodes implanted in their brains. Animals have also learned to open and close a simple robotic hand.
Andrew Schwartz and his colleagues at the University of Pittsburgh and Carnegie Mellon University in Pittsburgh describe themselves as the first to use animals’ brain activity to manipulate a physical object that moves in complex ways. Schwartz’s team implanted an array of tiny electrodes in a region of the monkeys’ brains called the motor cortex, which controls voluntary movement, to see how patterns of electrical activity in this region associated with the monkeys’ desire to reach toward pieces of food. Software interpreted where the monkeys wanted to reach – and whether they wanted to open or close the hand–based on that brain activity. The computer did the rest, calculating the specific movements of the robotic arm’s shoulder and elbow joints to perform the task. The computer’s rapid interpretation of the monkeys’ brain signals helped the robotic arm to move in a natural way and almost as quickly as a real arm.
"The thing that struck me was how naturally the animals interacted with the device," comments John Kalaska, a neuroscientist from the University of Montreal who wrote a commentary that appeared with the research online May 28 in the journal Nature. "It’s a further proof of principle that, down the line, we will be able to develop all the hardware necessary to allow paraplegic or quadriplegic patients to have prosthetic limbs that they can control in a natural way with their thoughts."
The brain could power equipment like a wheelchair if researchers at Brown University (BU) in Providence, RI, continue to progress with BrainGate. As of June 2009, the system was about to enter its second clinical trial. A microchip implanted in the brain of victims of multiple sclerosis and paralysis to help them convert electrical impulses in neurons into signals that control computers, cursors and wheelchairs.
“If someone wants to move their wheelchair back and forth,” explained BU Associate Professor of Engineering Leigh Hochberg in a BU news release, “the relevant brain area would send a signal to the hands, regardless of the fact that the hands cannot move.”
The April 2009 issue of Wired magazine featured the brain-to-device message sent by University of Wisconsin biomedical engineer Adam Wilson. Instead of using his hands to type, Wilson used his brain. "USING EEG TO SEND TWEET," he thought.
"We’re more interested in the applications," said Justin Williams, head of the University of Wisconsin’s Neural Interfaces lab. "How do we actually make these technologies useful for people with disabilities?"
The researchers built upon the BCI2000, a software tool pioneered by Williams and Wadsworth Center neural injury specialist Gerwin Schalk. The software translates thought-induced changes in a scalp’s electrical fields to control an on-screen cursor.
The work is special because it meets the immediate needs of locked-in people, said Purdue University biomedical engineer Kevin Otto, who was not involved in the project. Patients with this condition are aware and awake but unable to move or communicate due to paralysis.
The researchers regard email as a relatively difficult and inefficient task for someone on a brain-computer interface. The shorthand nature of Twitter is might have been invented just for tasks like sending a brain message. "It’s difficult enough to be able to spell words, much less find an address book and select names,” said Otto. Twitter, by contrast, “handles all the things that we’ve been struggling to make easy for a patient to do. It puts messages where people can find them. Let the world know how you’re doing, what you’re thinking, and they’ll find you.”
Even as man is Twittering with brain power alone, millions of the underprivileged people around the world who were born with impairments or maimed by war or disease are forced to cope without prosthetics or with designs from the Middle Ages – simple leather cups over amputated limbs or peg legs as primitive as Captain Ahab’s. They are a reminder that the job of conquering disability and handicap is unfinished until the advances are shared.
Sources: Wired; Time; Otto Boch Healthcare; SPA; In Motion; New Scientist; Cyberhand; iHand; BBC; Mann Medical Research Organization; ARC; Nature; Brown University
This article originally appeared in The Ergonomics Report™ on 2009-09-02.