Posts tagged prosthetic arm
Articles and news from the latest research reports.
Amputees discern familiar sensations across prosthetic hand
Even before he lost his right hand to an industrial accident 4 years ago, Igor Spetic had family open his medicine bottles. Cotton balls give him goose bumps.
Now, blindfolded during an experiment, he feels his arm hairs rise when a researcher brushes the back of his prosthetic hand with a cotton ball.
Spetic, of course, can’t feel the ball. But patterns of electric signals are sent by a computer into nerves in his arm and to his brain, which tells him different. “I knew immediately it was cotton,” he said.
That’s one of several types of sensation Spetic, of Madison, Ohio, can feel with the prosthetic system being developed by Case Western Reserve University and the Louis Stokes Cleveland Veterans Affairs Medical Center.
Spetic was excited just to “feel” again, and quickly received an unexpected benefit. The phantom pain he’d suffered, which he’s described as a vice crushing his closed fist, subsided almost completely. A second patient, who had less phantom pain after losing his right hand and much of his forearm in an accident, said his, too, is nearly gone.
New prosthetic arm controlled by neural messages
This design hopes to identify the memory of movement in the amputee’s brain to translate to an order allowing manipulation of the device.
Controlling a prosthetic arm by just imagining a motion may be possible through the work of Mexican scientists at the Centre for Research and Advanced Studies (CINVESTAV), who work in the development of an arm replacement to identify movement patterns from brain signals.
First, it is necessary to know if there is a memory pattern to remember in the amputee’s brain in order to know how it moved and, thus, translating it to instructions for the prosthesis,” says Roberto Muñoz Guerrero, researcher at the Department of Electrical Engineering and project leader at Cinvestav.
He explains that the electric signal won’t come from the muscles that form the stump, but from the movement patterns of the brain. “If this phase is successful, the patient would be able to move the prosthesis by imagining different movements.”
However, Muñoz Guerrero acknowledges this is not an easy task because the brain registers a wide range of activities that occur in the human body and from all of them, the movement pattern is tried to be drawn. “Therefore, the first step is to recall the patterns in the EEG and define there the memory that can be electrically recorded. Then we need to evaluate how sensitive the signal is to other external shocks, such as light or blinking.”
Regarding this, it should be noted that the prosthesis could only be used by individuals who once had their entire arm and was amputated because some accident or illness. Patients were able to move the arm naturally and stored in their memory the process that would apply for the use of the prosthesis.
According to the researcher, the prosthesis must be provided with a mechanical and electronic system, the elements necessary to activate it and a section that would interpret the brain signals. “Regarding the material with which it must be built, it has not yet been fully defined because it must weigh between two and three kilograms, which is similar to the missing arm’s weight.”
The unique prosthesis represents a new topic in bioelectronics called BCI (Brain Computer Interface), which is a direct communication pathway between the brain and an external device in order to help or repair sensory and motor functions. “An additional benefit is the ability to create motion paths for the prosthesis, which is not possible with commercial products,” says Muñoz Guerrero.
The U.S. Food and Drug Administration (FDA) today allowed marketing of the DEKA Arm System, the first prosthetic arm that can perform multiple, simultaneous powered movements controlled by electrical signals from electromyogram (EMG) electrodes.
EMG electrodes detect electrical activity caused by the contraction of muscles close to where the prosthesis is attached. The electrodes send the electrical signals to a computer processor in the prosthesis that translates them to a specific movement or movements.
The EMG electrodes in the DEKA Arm System convert electrical signals into up to 10 powered movements, and it is the same shape and weight as an adult arm. In addition to the EMG electrodes, the DEKA Arm System contains a combination of mechanisms including switches, movement sensors, and force sensors that cause the prosthesis to move.
“This innovative prosthesis provides a new option for people with certain kinds of arm amputations,” said Christy Foreman, director of the Office of Device Evaluation at the FDA’s Center for Devices and Radiological Health. “The DEKA Arm System may allow some people to perform more complex tasks than they can with current prostheses in a way that more closely resembles the natural motion of the arm.”
The FDA reviewed clinical information relating to the device, including a 4-site Department of Veterans Affairs study in which 36 DEKA Arm System study participants provided data on how the arm performed in common household and self-care tasks. The study found that approximately 90 percent of study participants were able to perform activities with the DEKA Arm System that they were not able to perform with their current prosthesis, such as using keys and locks, preparing food, feeding oneself, using zippers, and brushing and combing hair.
The DEKA Arm System can be configured for people with limb loss occurring at the shoulder joint, mid-upper arm, or mid-lower arm. It cannot be configured for limb loss at the elbow or wrist joint.
Data reviewed by the FDA also included testing of software and electrical and battery systems, mitigations to prevent or stop unintended movements of the arm and hand mechanisms, durability testing (such as ability to withstand exposure to common environmental factors such as dust and light rain), and impact testing.
The FDA reviewed the DEKA Arm System through its de novo classification process, a regulatory pathway for some novel low- to moderate-risk medical devices that are first-of-a-kind.
The DEKA Arm System is manufactured by DEKA Integrated Solutions in Manchester, N.H.
Paralyzed Patient Moves Prosthetic Arm With Her Mind
It sounds like science fiction, but researchers are gaining ground in developing mind-controlled robotic arms that could give people with paralysis or amputated limbs more independence.
The technology, known as brain-computer (or brain-machine) interface, is in its infancy as far as human use — though scientists have been studying the concept for years. But experts say that people with paralysis or amputations could be using the technology at home within the next decade.
It basically boils down to people using their thoughts to control a robot arm that then performs a desired task, like grasping and moving a cup. That’s done via tiny electrode “grids” implanted in the brain that read the movement signals firing from individual nerve cells, then translate them to the robot arm.
"We have the ability to capture information from the brain and use it to control the robotic arm," said Dr. Elizabeth Tyler-Kabara, who presented her team’s latest findings on the technology Tuesday, at the annual meeting of the American Association of Neurological Surgeons, in New Orleans.
However, she stressed, “we still have a ton to learn.”
Right now, the robot arm is confined to the lab. After getting their electrodes implanted, study patients come to the lab to work with the robotic limb under the researchers’ supervision. So far, Tyler-Kabara and her colleagues at the University of Pittsburgh School of Medicine have tested the approach in one patient. Researchers at Brown University in Providence, R.I., have done it in a handful of others.
One of the big questions, Tyler-Kabara said, is “how much control is enough?” That is, how well does the mind-controlled arm need to work to bring real everyday benefits to people?
At the meeting on Tuesday, Tyler-Kabara presented an update on how her team’s patient is faring. The 53-year-old woman had long-standing quadriplegia due to a disease called spinocerebellar degeneration — where, for unknown reasons, the connections between the brain and muscles slowly deteriorate.
Tyler-Kabara performed the surgery, where two tiny electrode grids were placed in the area of the brain that would normally control the movement of the right hand and arm. The electrode points penetrate the brain’s surface by about one-sixteenth of an inch.
"The idea is pretty scary," Tyler-Kabara acknowledged. But her team’s patient had no complications from the surgery and left the hospital the next day. There’ve been no longer-term problems either, she said — though, in theory, there would be concerns about infection or bleeding over the long haul.
The surgery left the patient with two terminals that protrude through her skull. The researchers used those to connect the implanted electrodes to a computer, where they could see brain cells firing when the patient thought about moving her hand.
She was quickly able to master simple movements with the robotic arm, like high-fiving the researchers. And after six months, she was performing “10-degrees-of-freedom” movements, Tyler-Kabara reported at the meeting.
That includes not only moving the arm, but also flexing and rotating the wrist, grasping objects and affecting several different hand “postures.” She has accomplished feats like feeding herself chocolate.
The researchers initially used a computer in training sessions with the patient, but after that the robot arm is directly linked to the electrodes — so there is no need for “computer assistance,” according to Tyler-Kabara.
Still, before the technology can ultimately be used at home, she said, researchers have to devise a “fully implanted” wireless system for controlling the robot arm.
Another expert talked about the new technology.
"This is one more encouraging step toward developing something practical that people can use in their daily lives," said Dr. Robert Grossman, a neurosurgeon at Methodist Neurological Institute in Houston, who was not involved in the research.
It’s hard to put a time line on it all, Grossman said, since technological advances could changes things. He also noted that several research groups are looking at different approaches to brain-computer interfaces.
One, Grossman said, is to do it noninvasively, through electrodes placed on the scalp.
Study author Tyler-Kabara said that noninvasive approach has met with success in helping people perform simple tasks, like moving a cursor on a computer screen. “But I don’t think it will ever be good enough for performing complicated tasks,” she said, noting that it can’t work as precisely as the implanted electrodes.
A next step, Tyler-Kabara said, is to develop a “two-way” electrode system that stimulates the brain to generate sensation — with the aim of helping people adjust the robot’s grip strength.
She said there is also much to learn about which people will ultimately be good candidates for the technology. There may, for example, be some brain injuries that prevent people from benefiting.
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
(Source: health.usnews.com)
New metric to track prosthetic arm progress
A new validated and reliable measure of how well an adult amputee is able to perform everyday tasks with a prosthetic arm will help physical and occupational therapists, prosthetists, and doctors assess the progress that patients make during training with their new limb.
Amputees with a new prosthetic arm must learn how to use their device to perform everyday tasks that were once second nature. Taking off a shirt becomes a conscious, multistep effort: grasp the shirt, lift the shirt over the head, pull arms through the sleeves, place the shirt on the table, let go of the shirt.
In the best cases of treatment, patients work with teams of doctors, prosthetists, and therapists to learn how their new limbs can help them regain function and quality of life. But clinicians have had few tools to assess whether that crucial teaching/learning process is going well, because of a lack of standardized measurements to use with adults with upper limb amputations. To change that, a research team has unveiled a new index that clinicians can use to assess their patients’ progress. They describe the Activities Measure for Upper Limb Amputees (the AM-ULA) in an article published online Oct. 19 in the Archives of Physical Medicine and Rehabilitation.