Development of Separate Exoskeleton Socket of Wrist Joint on Myoelectric Prosthetic Hand for Congenital Defects with Symbrachydactyly

People with adactyly (symbrachydactyly) have difficulty grasping objects with only the remaining palm because all fingers are not fully formed. Myoelectric prosthetic hands can reflect the user intention and can effectively improve activities of daily living. Unlike in forearm defect, the existing wrist joint can be performed who have remaining palm. When the wrist is immobilized by a socket or other means, compensatory shoulder movements, such as raising the elbow to realize the function of the lost wrist, are involved. Such compensatory movement can result in joint deformity and joint contractures due to unnatural postures. The development of a prosthetic hand that can discriminate between the wrist joint and the opening and grasping of the hand can will enable actions to be performed in various positions without compensatory movements, such as those of the shoulder joint. Therefore, in this study, a myoelectric prosthetic hand was developed which that does not interfere with the wrist joint movements in adactyly. A socket shaped prosthetic separating the hand from the myoelectric sensor was adopted to avoid interfering with the wrist motion. MediaPipe was employed to verify whether the use of a separate hand decreases compensatory movements during grasping. The prosthetic hand was tested on healthy males. A reduction in the compensatory movement of the shoulder joint and an improvement in performance over 30 s were observed compared to the case in which the conventional myoelectric prosthetic hands were used. The proposed myoelectric prosthetic hand for adactyly can therefore reduce compensatory movements and alleviate the burden on the user. In addition, the advantages of sockets that can utilize the wrist for compensatory movements were demonstrated.