Prosthetic Hand Provides Real-Time Sense of FeelingProsthetic Hand Provides Real-Time Sense of Feeling

Developing prosthetic limbs that can feel has long been a goal of bionics researchers. Now, in "Restoring Natural Sensory Feedback in Real-Time Bidirectional Hand Prostheses," a paper published February 5 in the journal Science Translational Medicine, researchers at the Swiss Federal Institute of Technology (Lausanne, Switzerland) have added to recent advances in prosthetics that can convey sensation. The team was led by Silvestro Micera, PhD, of The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy and the Center for Neuroprosthetics and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne, Switzerland.

The paper, which lists 21 authors from nine different institutions in six EU countries, describes how the experiment provided "near-natural" sensory information by inserting electrodes into the patient's ulnar and median nerves. Grasping forces detected by sensors embedded in the fingertips of an artificial hand were translated into electrical stimuli delivered to the electrodes. In the abstract of their paper, the scientists say, "This feedback enabled the participant to effectively modulate the grasping force of the prosthesis with no visual or auditory feedback." Three different levels of force were distinguished and consistently used by the subject, a man who had lost his left hand in a fireworks accident nine years ago.

The subject, Dennis Aabo Sørensen, said "It was quite amazing, because suddenly I was able to feel something I hadn't been feeling for nine years," in an English language YouTube video provided by the Swiss institute. "I could feel round things and hard things and soft things," he said. "The feedback was totally new to me. Suddenly, when I was doing the movements, I could feel what I was doing, instead of looking at what I was doing."

The researchers worked with Sørensen for 30 days of testing. They report that their results demonstrate that high complexity of perception can be obtained, which allows "the subject to identify the stiffness and shape of three different objects by exploiting different characteristics of the elicited sensations." They now hope to continue their experiments with additional subjects and intend to reduce the size of the electronics for the hand. Further plans include improving the sensitivity of the sensors in the fingers.

We also reported in December the case of Igor Spetic, a 48-year-old Ohio man who had been fitted by a research team from Case Western Reserve University and the Cleveland Veterans Affairs Medical Center with a prosthetic hand equipped with a neural interface that also conveys a sense of touch.