New surgical technique shows promise for improving function of artificial arms

Feb 10, 2009

A surgical technique known as targeted muscle reinnervation appears to enable patients with arm amputations to have improved control of functions with an artificial arm, according to a study in the February 11 issue of JAMA.

Currently available prostheses following upper-limb amputation do not adequately restore the function of an individual's arm and hand. The most commonly used prostheses are body-powered, which capture remaining shoulder motion with a harness and transfer this movement through a cable to operate the hand, wrist, or elbow. With this control method, only one joint can be operated at a time, according to background information in the article.

Improving the function of prosthetic arms remains a challenge, because access to the nerve-control information for the arm is lost during amputation. With the surgical procedure, targeted muscle reinnervation (TMR), remaining arm nerves are transferred to chest or upper-arm muscles that are no longer biomechanically functional due to loss of the limb. The goal of this procedure is to improve control of prostheses that use electromyogram (EMG) signals (the electrical signals generated during muscle contraction) from residual limb muscles to control motorized arm joints. Once reinnervated (restore nerve function), these muscles provide physiologically appropriate EMG signals for control of the elbow, wrist, and hand. It is unknown whether reinnervated muscles can stably and accurately provide myoelectric (electrical impulses in muscle) signals for real-time control of multifunction prostheses.

Todd A. Kuiken, M.D., Ph.D., of the Rehabilitation Institute of Chicago, and colleagues assessed the performance of five patients with upper-limb amputation who had undergone TMR surgery. The study, conducted between January 2007 and January 2008, also included 5 control participants without amputation. All participants were instructed to perform various arm movements, and their abilities to control the virtual prosthetic arm were measured.

The average motion selection times for elbow and wrist movements (elbow flexion/extension, wrist rotation, and wrist flexion/extension) were 0.22 seconds for TMR patients and 0.16 seconds for control participants. The average motion completion rate for elbow and wrist movements was high (96.3 percent for TMR patients and 100 percent for control participants). The average motion completion times for elbow and wrist movements were 1.29 seconds for TMR patients and 1.08 seconds for control participants. For both groups, hand grasps took longer to complete than arm movements; the average motion completion times for hand grasps were 1.54 seconds for TMR patients and 1.26 seconds for control participants.

Three of the patients were able to demonstrate the use of the control system in advanced prostheses, including motorized shoulders, elbows, wrists, and hands.

"These early trials demonstrate the feasibility of using TMR to control complex multifunction prostheses. Additional research and development need to be conducted before field trials can be performed," the authors write. "The prosthetic arms tested in this study performed very well as early prototypes. Further improvements are needed and have been planned, including reducing the size and weight and increasing the robustness of these advanced prostheses."

Article: JAMA. 2009;301[6]:619-628.

Source: JAMA and Archives Journals

Explore further: Experts call for higher exam pass marks to close performance gap between international and UK medical graduates

add to favorites email to friend print save as pdf

Related Stories

Put the brakes on using your brain power

Jul 29, 2011

German researchers have used drivers' brain signals, for the first time, to assist in braking, providing much quicker reaction times and a potential solution to the thousands of car accidents that are caused by human error.

Recommended for you

What are the chances that your dad isn't your dad?

Apr 16, 2014

How confident are you that the man you call dad is really your biological father? If you believe some of the most commonly-quoted figures, you could be forgiven for not being very confident at all. But how ...

New technology that is revealing the science of chewing

Apr 15, 2014

CSIRO's 3D mastication modelling, demonstrated for the first time in Melbourne today, is starting to provide researchers with new understanding of how to reduce salt, sugar and fat in food products, as well ...

After skin cancer, removable model replaces real ear

Apr 11, 2014

(HealthDay)—During his 10-year struggle with basal cell carcinoma, Henry Fiorentini emerged minus his right ear, and minus the hearing that goes with it. The good news: Today, the 56-year-old IT programmer ...

User comments : 0

More news stories

Chronic inflammation linked to 'high-grade' prostate cancer

Men who show signs of chronic inflammation in non-cancerous prostate tissue may have nearly twice the risk of actually having prostate cancer than those with no inflammation, according to results of a new study led by researchers ...

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...