by
Olga Deshchenko, DOTmed News Reporter | April 15, 2011
From the April 2011 issue of HealthCare Business News magazine
If the MPL successfully reaches the market through the Innovation Pathway, the FDA is likely to see more applicants from the prosthetics field. Engineers at institutions like Vanderbilt University are continuously working on advancing mobility and functionality for amputees.
Researchers at the Nashville, Tenn.-based university’s Center for Intelligent Mechatronics have been working on a transradial (below the elbow) multi-grasp prosthesis since 2005.
Michael Goldfarb, professor of mechanical engineering with institution, says there are currently two options for upper-limb amputees, a body powered or a myoelectric prosthesis.
The body powered prosthesis is the most common and has been around since World War II. It consists of split hooks connected to a harness an amputee wears around the shoulders. The shrugging motions of the shoulders open and close the hooks, enabling people to pick up and put down objects.
The myoelectric prosthesis came about in the 1970s and works by reading the electrical activity in the muscles from the skin. These devices are molded to look like hands with real fingers, which is an important factor for amputees, says Goldfarb.
But the current offerings have their drawbacks – despite differences in price and fragility, both types of prostheses offer the same, limited functionality to the amputee – opening and closing of the device. A myoelectric user cannot point a finger or hold out a flat hand. And with body powered prosthesis, an amputee cannot reach above the head or shoulders.
There is also a problem of sensory feedback. Unlike healthy people, amputees lack a sense of proprioception, or knowing where their limbs are without looking at them. Force feedback, or knowing how hard something is squeezed, for instance, is also largely absent.
Some of the sensory information is retained with the body powered prosthesis, but the more expensive option fares worse. “The only sensory feedback amputees have from a myoelectric prosthesis is visual,” says Goldfarb. “If you have to stare at your hand the whole time you’re using it, then it’s really not that useful.”
Beyond functional aspects of the prostheses, there are also psychological effects. Amputees may not feel like a prosthetic device is a part of their body but rather “just kind of this artificial appendage,” says Goldfarb.
To overcome the limitations of today’s typical devices, Goldfarb’s team is working on a multi-grasp prosthesis that offers a lot more dexterity. Rather than having a device that just opens and closes, the fingers of Goldfarb’s invention perform nine common grasps that people use in their every day lives. (Examples include pointing, a tip grasp and a tripod grasp, used to hold a writing utensil.)
