Upgrading the Prosthetic Hand

A lightweight prosthetic hand uses hydraulics to achieve more natural finger movement.

Freedom to move: The Fluidhand (above) uses lightweight miniature hydraulics to enable the wearer to move each finger individually. Credit: The Research Center, Karlsrühe/Forschungszentrum

A lightweight hydraulic hand with individually powered fingers could change the lives of amputees, say researchers in Germany. The Fluidhand, according to its developers, is lighter, behaves more naturally, and has greater flexibility than artificial hands that use motorized fingers.
The Fluidhand prototype, developed by a team led by Stefan Schulz at the Research Center in Karlsrühe, in partnership with the Orthopedic University Hospital, in Heidelberg, Germany, has flexible drives located in each of its finger joints, enabling the wearer to move each finger independently. Lightweight miniature hydraulics are connected to elastic chambers that can flex the joints of the fingers. As sensors on the fingers and palm close around objects, nerves in the amputation stump pick up muscular sensations so that the amputee can use a weaker or stronger grip. The prosthetic provides five different strengths of grip.
"It is so intuitive that learning to use the device only takes about 15 minutes," says Schulz.
Last September, 18-year-old Sören Wolf, who was born with only one hand, became the first person to use the Fluidhand. According to German press reports, Wolf was able to type on a keyboard with both of his hands for the first time in his life, and he told reporters that, when he's wearing the Fluidhand, he doesn't feel handicapped anymore.
International interest in the Fluidhand peaked late last month, when it was announced that the Orthopedic University Hospital is testing the device in comparison with the i-LIMB Hand. Wolf is the first amputee to use both prosthetics.
Produced by the Scottish company Touch Bionics, i-LIMB was the first prosthetic hand that enabled the movement of individual fingers. The prosthetic, released last summer, uses a different technical principle than the Fluidhand. With i-LIMB, movement is enabled by five small, battery-powered motors that are embedded in each finger. Schulz believes that the hydraulic system has some advantages over the motorized fingers. "In contrast to the movement with electric motors and transmissions, the Fluidhand remains soft and flexible," he says. "Articles can therefore be seized more reliably, and the hand feels more natural."
Both devices are significant improvements over conventional hand prostheses that only enable the wearer to pinch the thumb and forefinger to create a grip.
"There are many hand movements that require individual digit movements," says Hugh Herr, director of the Biomechatronics Group at the MIT Media Lab. "The development of individual finger movements in a prosthetic is a remarkable step forward."

One patient is currently wearing the Fluidhand to complete daily tasks, and a second is about to be fitted for the device. Some 250 people, including soldiers wounded in Afghanistan and Iraq, already use i-LIMB.
Stuart Mead, CEO of Touch Bionics, points out that the comparative study in Heidelberg is not a competitive one. "Many people have many different devices for different activities, and what works for one patient may not work for another," he says.
Comparative studies of this nature do have value for determining how well the device can meet amputees' needs. "They are probably testing each device's strength, power, and versatility," says Herr. "The prosthetics have to be able to pick up something very lightweight and fragile, like a piece of china, as well as something large and heavy."
Soon, people requiring a prosthetic hand with movable digits will have more options. "The German-Austrian company OttoBock will probably present a new hand with movable fingers in 2009," says Schulz.
Experts expect this rapid development in the field of prosthetic technologies to continue into the near future.
"I believe that there is a big push into wearable exoskeletons because the mechatronic technology has matured, becoming more cost effective, miniaturized, and powerful," says Thomas Sugar of Arizona State University, who works in robotic prosthetics. "Batteries and motors are smaller and more powerful. Microprocessors have been very fast and cheap. Lastly, I do think there has been a big push by NIH [National Institutes of Health] and the DOD [Department of Defense] into medical robots for stroke therapy, powered exoskeletons, and powered prosthetics."
The Biomechatronics Group's Herr agrees. "Typically, when you plot prosthetic innovations against time, you see a spike in innovation after every war, and that is certainly true today," he says. "In addition, we're also seeing a number of disciplines such as robotics, mechanical engineering, and biomechatronics mature to the point [where] we can merge to create truly remarkable systems."
There is still room for those remarkable innovations in prosthetic development.
"We find ourselves, as an industry, working to manage people's expectations," says Touch Bionics' Mead. "A prosthetic doesn't function like a real hand. We're still only able to replicate 5 to 10 percent of what a real hand can do."

A Gentler Way to Jump-Start the Brain

Scientists in Israel are testing a noninvasive method to electrically stimulate neurons deep in the brain.

Deeply affected: Patients with severe depression may find relief with the help of a wired helmet (above). A magnetic field generated by the helmet harmlessly induces electric currents deep in the brain, giving underactive neurons a much-needed jump start.

Electrically shocking the brain is often the only recourse for people suffering from severe, untreatable depression. While standard antidepressants have little effect on these patients, electroconvulsive therapy (ECT) can sometimes jump-start the brain, lifting people out of depression, at least for a while. But ECT can also carry some serious side effects, including seizures and memory loss.
Now researchers are exploring a gentler approach to electrically stimulating the brain. The technique, called transcranial magnetic stimulation (TMS), uses an external magnetic field to create electric currents within the brain. Until recently, researchers experimenting with TMS have only been able to stimulate superficial brain regions. Now a company in Israel called Brainsway has developed a TMS method that reaches deeper into the brain, to stimulate areas associated with depression and other neurological disorders. If successful, the therapy could provide a new alternative for the two-thirds of patients with major depression who fail to respond to antidepressants.
Brainsway's technology builds on traditional TMS methods, which involve placing an electromagnetic coil close to a patient's scalp. An external power source generates an electric current, which flows through the coil, which in turn creates a powerful magnetic field that travels through the skull, into the brain. Once in the brain, these electromagnetic waves generate electric current, stimulating nearby neurons, which then activate related networks, potentially strengthening connections within the brain.
However, a major limitation in TMS research has to do with the very nature of magnetic fields: electromagnetic waves decay rapidly after a short distance. This constraint has largely limited TMS's reach to brain areas one centimeter below the skull. In order to reach deeper regions, researchers would have to increase the intensity of the electric current flowing through the coil, which could induce painful side effects such as seizures and tissue damage.
Instead, Abraham Zangen, one of two inventors of Brainsway's deep TMS approach, and his colleagues designed a new coil configuration that is able to excite neurons at a depth of four centimeters, using the same intensity of current used in standard TMS coils. Instead of a single coil generating a single magnetic field through the brain, Zangen has outfitted a helmet with a number of small coils, each producing a separate magnetic field. As researchers run a standard current through the helmet, the coils, which are connected in a series, produce multiple fields that add up, generating a much stronger magnetic field that goes deeper into the brain before dropping off.
Zangen and his team have tested the helmet on a group of 50 people with severe depression, all of whom showed no improvement after taking antidepressants. During the double-blind clinical trial, half of the patients underwent deep TMS treatment at electrical intensities comparable to standard TMS for five days a week for four weeks, while the other half underwent similar treatments at lower intensities. Each treatment lasted about 20 minutes, during which patients wore the helmet while researchers periodically administered two-second electrical pulses. After the experiment, 50 percent of the patients who received the higher-intensity version reported significant improvements in sleep, appetite, and overall mood, while none of the others did. Most patients in the higher-intensity group also performed better on a standard cognitive test evaluating depression.

"We observed improved mood and optimism," says Zangen. "For example, people who before were just at home doing nothing were able to go back to work."
Brainsway is currently seeking approval in Europe and the United States for deep TMS as a therapeutic tool for depression and other brain-related diseases. Zangen anticipates that the technology will be approved in Europe within the next few months. Before it gains FDA approval, the company will have to test the technology on a much wider population. Zangen's team is now mobilizing clinical trials in a number of medical centers in the United States, including Johns Hopkins University and Harvard Medical School.
Meanwhile, Brainsway is designing different coils to tackle brain regions associated with other conditions, such as post-traumatic stress disorder, autism, and drug addiction. Zangen says that in addition to stimulating underactive areas of the brain such as those associated with depression, deep TMS can be used to inhibit brain regions that may be abnormally overactive, such as during addiction.
"The idea is, you want to reduce some connectivity that was established during addiction, and actually weaken some synapses in the reward system of the brain," says Zangen. "If you use lower-frequency stimulation, you can actually inhibit overactive neurons and reduce connectivity over the long term."
Alvaro Pascual-Leone, director of the Center for Noninvasive Brain Stimulation at the Beth Israel Deaconess Medical Center, says that while deep TMS may have beneficial effects on depression, it may not work for all patients, and researchers will have to find a way to tailor the technology to each individual.
"It's still unclear how to make TMS optimally antidepressant for any one individual," says Pascual-Leone. "Ultimately, you would have to individualize intervention. But this is the only successful attempt in generating a coil that can reach deep in the brain, and that's exciting."