View of the residual limbs with the connected six optimal (P1, left), respectively initial twelve (P2, right) pair of electrodes.
Photograph courtesy of the study authors. © 2018 Jarrassé, de Montalivet, Richer, Nicol, Touillet, Martinet, Paysant and de Graaf.
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Researchers from the National Center for Scientific Research (Centre national de la recherche scientifique/CNRS), Paris, and Aix-Marseille University, Marseille, France, have developed a device capable of detecting movements made within the residual limb of transhumeral amputees that can provide intuitive control of a myoelectric prosthesis, without training or surgery. The open-access study was published November 29 in Frontiers in Bioengineering and Biotechnology.
The execution of movements of the phantom limb among people with transhumeral amputations, such as pinching, making a fist, or wrist rotation and flexion, are associated with specific muscle contractions in the residual limb, which research shows most people with amputations can perform. In people with transhumeral amputations, the contractions concern muscle groups that are not associated with the joints used before the amputation, as if muscle reinnervation had spontaneously occurred, without surgery, according to the researchers.
The objective of the study was to evaluate the possibility for transhumeral amputees to use a Phantom Limb Mobilization (PLM)-based control approach to perform more realistic functional grasping tasks. For the prototype, the research team created algorithms capable of recognizing muscle activity generated by mobilization of the phantom limb and reproduction of the detected movement by the prosthesis.
In the tests, two people with transhumeral amputations were asked to repeatedly grasp one of three objects using an unworn eight-active-degree-of-freedom prosthetic arm and release the object in a dedicated drawer. The prosthesis control was based on PLM and myoelectric pattern recognition techniques, using only two repetitions of each PLM for training. The results showed that the task could be successfully achieved, even if the completion time was increased in comparison with the performances of a control group and the control strategies required numerous corrections.
The authors of the study note that while limitations of the technique still exist, the preliminary results encourage further exploration and deeper understanding of the phenomenon of natural residual myoelectric activity related to PLM.
Editor’s note: This story was adapted from materials provided by CNRS.
