As prosthetic devices get more advanced thanks to new materials, designs, and sensors, their abilities are quickly outpacing how they interface with the human body. In particular, strap-on prosthetic arms that are worn like mittens over a stump can never match the strength of rigid bone. In addition, the signal gathered through skin electromyography is both noisy and quiet, limiting devices that can actually be rather dexterous if supplied with a high resolution signal.
To overcome both problems in one sweep, scientists from Sahlgrenska University Hospital and Chalmers University of Technology in Sweden outfitted an arm amputee with a bone anchored prosthesis that is controlled by electrodes implanted directly onto the nerves. Because the electrodes can be used to send signals up the arm in addition to reading those coming down, the team hopes to be able to induce a sense of touch or something resembling it in the next step of the project.
The first patient has recently been treated with this technology, and the first tests gave excellent results. The patient, a previous user of a robotic hand, reported major difficulties in operating that device in cold and hot environments and interference from shoulder muscles. These issues have now disappeared, thanks to the new system, and the patient has now reported that almost no effort is required to generate control signals. Moreover, tests have shown that more movements may be performed in a coordinated way, and that several movements can be performed simultaneously.
“The next step will be to test electrical stimulation of nerves to see if the patient can sense environmental stimuli, that is, get an artificial sensation. The ultimate goal is to make a more natural way to replace a lost limb, to improve the quality of life for people with amputations,” says [Dr Rickard Brånemark, Sahlgrenska University Hospital].
Chalmers press release: World premiere of muscle and nerve controlled arm prosthesis