Muscle- and Nerve-Controlled Prosthetic Arm Unveiled
February 22, 2013
An operation has been conducted-said to be the world's first-at Sahlgrenska University Hospital (SU), Gothenburg, Sweden, where electrodes have been permanently implanted in the nerves and muscles of a transhumeral amputee's residual limb to allow him to directly control an osseointegrated prosthetic arm. The result allows control of an advanced robotic prosthesis with motions more similar to that of a natural limb.
By using implanted electrodes, rather than electrodes positioned on the skin, more signals can be retrieved and therefore more movement control is possible. It is also possible to provide the patient with feeling through neural stimulation.
The surgical team was led by Rickard Brånemark, MD, MSC, PhD, the director of the Centre of Orthopaedic Osseointegration at SU and associate professor at the Sahlgrenska Academy, University of Gothenburg. The operation was possible thanks to new technology developed by Chalmers University of Technology (Chalmers), Gothenburg, industrial doctoral student Max Ortiz Catalan, who was supervised by Brånemark and Bo Håkansson, PhD, a professor and leader of the biomedical signals and systems research group at Chalmers.
"The new technology is a major breakthrough that has many advantages over current technology, which provides very limited functionality to patients with missing limbs," said Brånemark. He added that by combining a bone-anchored prosthesis with implanted electrodes, the technology overcomes two issues associated with the advancement of robotic prostheses-how to firmly attach a prosthesis to the human body and how to intuitively and efficiently control the prosthesis in order to be truly useful and regain lost functionality.
Brånemark, who, in 1990 along with his colleagues, became the first to achieve clinical success with osseointegration for prosthetic limb attachment, also developed the bone anchor system used in this operation-the Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA) titanium implant system. Using the implant system over a traditional socket prosthesis "allows complete degree of motion for the patient, fewer skin-related problems, and a more natural feeling that the prosthesis is part of the body," said Brånemark.
The first patient to be treated with this technology was a prior robotic hand user who had 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 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...," said Brånemark. "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."
Editor's note: This story was adapted from materials provided by Chalmers University of Technology.