image: (A) Overview of the proposed socket type and fixation of the socket; and (B) control system.
Credit: Yuki Inoue, Graduate School of Informatics and Engineering, The University of Electro-Communications.
A research paper by scientists at The University of Electro-Communications developed a new socket and prosthetic hand control system that does not interfere with the wrist joint motion. This allows individuals with hand defects who previously used prosthetic hands with fixed wrist joints to freely use their remaining wrist functionality.
The new research paper, published on Jul. 15 in the journal Cyborg and Bionic Systems, established a methodology and verified the effectiveness of a myoelectric prosthetic hand that could be used while maintaining the function of the residual wrist.
In recent years, the functionality of myoelectric prosthetic hands has improved as motors have become smaller and controls have become more advanced. Attempts have been made to reproduce the rotation and flexion of the wrist by adding degrees of freedom to the wrist joint. However, it is still difficult to fully reproduce the functionality of the wrist joint owing to the weight of the prosthesis and size limitations. “In this study, we proposed a new myoelectric prosthetic system for individuals without fingers, focusing on 2 aspects: mechanism and control. Mechanically, we proposed dividing the socket into a hand part and a sensor measurement part while preserving wrist joint functionality. In terms of control, we separated the wrist joint signals from the hand signals to ensure that wrist movements did not inadvertently affect hand movements. This allows users to easily and unconsciously achieve their desired joint angles, significantly reducing compensatory movements.” explained study author Yuki Inoue, a professor at The University of Electro-Communications. In the pick-and-place experiment, where blocks were moved from higher to lower locations, the author confirmed that the proposed system resulted in a lower elbow position compared with the traditional prosthesis, and the number of blocks transported increased. This significantly reduced the compensatory motion of the elbow and improved the user’s performance compared with the use of a conventional prosthetic hand. “This study established a methodology and verified the effectiveness of a myoelectric prosthetic hand that could be used while maintaining the function of the residual wrist.” said study authors.
The use of conventional sockets often results in compensatory movements, and this phenomenon is observed even in participants with symbrachydactyly who retain partial wrist functionality. Such movements increase the stress on the user. In this field, a myoelectric prosthetic hand that is suitable for patients with residual wrist function has not been developed. The aim of this study was to develop a socket optimized for participants with symbrachydactyly, capitalizing on their residual wrist capabilities. “We conducted a quantitative evaluation comparing the ease of the grasping motion using our newly designed separate type socket with that of the conventional socket. The innovative design of the developed socket facilitates unobstructed wrist movement by separating the sections for hand attachment from the EMG sensor, thereby minimizing the need for compensatory elbow movements.” said study authors. In view of the above findings, this study demonstrates the usefulness of a new myoelectric prosthetic hand that utilizes the residual functions of people with hand deficiencies, which have not been utilized in the past, and the direction of its development.
This study established a methodology and verified the effectiveness of a myoelectric prosthetic hand that could be used while maintaining the function of the residual wrist. Future studies should include a larger cohort of participants with symbrachydactyly and develop training methods that better leverage the advantages of these innovative sockets.
Authors of the paper include Yuki Inoue, Yuki Kuroda, Yusuke Yamanoi, Yoshiko Yabuki, and Hiroshi Yokoi
This work was supported by JSPS KAKENHI (grant numbers JP18H03761, JP21K14125, and JP23H00166), the New Energy and Industrial Technology Development Organization (NEDO), and the Ministry of Health, Labor and Welfare (MHLW) in Japan.
The paper, “Development of Wrist Separated Exoskeleton Socket of Myoelectric Prosthesis Hand for Symbrachydactyly” was published in the journal Cyborg and Bionic Systems on Jul 15, 2024, at DOI: 10.34133/cbsystems.0141.