TMR surgery enhances use of virtual arms

Chicago, February 11: Latest surgery, named as targeted muscle reinnervation (TMR) can prove to be boon for people with an amputated arm, as it permits amputees to manage many parts of an artificial limb at one time.

Prostheses available at present do not help in reinstating proper functioning of the arm and hand. Almost all the prostheses are body-powered. This means that they control the movement of the shoulder with a harness, which is then further transferred with the help of a cable and ultimately the hand, wrist or elbow moves. But this procedure enables movement of only one joint at a specific time.

When any body part of a person is amputated, the access to nerve-control information perishes.

But the latest technology carries the rest of the arm nerves to chest or upper-arm muscles. When nerve function goes back to normal with the help of surgery, these muscles give the right electrical signals so as to manipulate the functioning of elbow, wrist and hand.

In order to determine how effective TMR is, researchers led by Todd Kuiken, MD, PhD, from the Rehabilitation Institute of Chicago, took into account five amputees who had undergone surgery. These people were compared to five people who had not had amputation.

In order to conduct the study, volunteers were made to perform different arm movements between the time period of January 2007 and January 2008. Researchers determined how well they were able to control an artificial prosthetic arm.

It was discovered that non-amputees were quicker than TMR patients. But the times were approximately close. For example, TMR patients were able to perform elbow and wrist movements in an average of 1.29 seconds. On the other hand, non-amputee participants were able to complete the same movements in 1.08 seconds.

The researchers wrote, “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.”

Gerald Loeb, MD, Chief Executive of SynTouch, wrote in an editorial that the agility and exactness of the movements of TMR patients “represent substantial improvements over previous myoelectric syatems.”