December 12, 2012

Vanderbilt Developing a Multigrasp Myoelectric Hand

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The test subject models the VMG Hand. Photograph courtesy of Vanderbilt University.

Researchers at the Vanderbilt University Center for Intelligent Mechatronics (CIM), Nashville, Tennessee, have developed what they say is a multigrasp myoelectric prosthetic hand and control structure that enables intuitive control from a standard, two-electrode electromyogram (EMG) interface.

The hand provides three precision grasps (tip grasp, lateral pinch, and tripod), three whole-hand grasps (cylindrical, spherical, and hook), and two postures (point and platform) as well as movement between these grasps and postures. It also has nine degrees of freedom (joints). Hand movement is triggered by the action of polyethylene tendons, which spool onto pulleys affixed to the shafts of motors that are housed in the palm. The current version of the Vanderbilt Multigrasp (VMG) hand—the third major version—is battery-powered, contains embedded electronics, and has been tested by two individuals with amputations at this point in time, according to lead investigator Michael Goldfarb, PhD, the H. Fort Flowers Chair in mechanical engineering and professor of mechanical engineering and of physical medicine and rehabilitation.

“We believe our control interface, which is unique in this field, enables a user to easily access multiple grasps, and the early [test] results appear to support this assertion,” Goldfarb said.

He offered results from a case study in which an individual with bilateral transradial amputations used the VMG and multigrasp myoelectric controller (MMC) interface on his left hand to perform the Southampton Hand Assessment Procedure (SHAP). The VMG Hand scored an 81 on the SHAP, versus a 74 and 52, respectively, for other myoelectric hands, Goldfarb said. He added that it is important to note that the results are preliminary and involve a single subject; additional testing is pending.

“We are currently recruiting additional subjects and performing more testing, so that we can report (in 2013) the averaged results from several subjects,” Goldfarb said.

Although the hand is still in development and testing stages, Goldfarb said the technology has been licensed to Orthocare Innovations, headquartered in Oklahoma City, Oklahoma. A specific timeline has not been set to bring the hand to market, but talks are expected to commence in early 2013.

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