Trans-radial prosthesis with three opposed fingers

There are body-powered hooks and myoelectric prosthetic hands that trans-radial amputees can use for work. Though the body-powered hooks have good workability for complex operations, the design of the hook is unappealing and the harness is cumbersome. The myoelectric prosthetic hand has a natural appearance similar to the human hand and intuitive operability using a myoelectric control system. However, it is expensive and heavy. Because of these problems associated with prostheses for work, many amputees use cosmetic prostheses. In this paper, we report a lightweight, low-cost electric trans-radial prosthesis with three opposed fingers. A simple mechanism to control the fingers by a linear actuator contributes to its good workability, lightweight, and low-cost. An operation system using an inexpensive distance sensor allows intuitive operability equivalent to the myoelectric control system. A socket makes the prosthesis easily removable. The total weight of the hand and socket is 300 g, and both can be produced with a 3D printer. An evaluation using the Southampton Hand Assessment Procedure (SHAP) demonstrated that an amputee was able to operate abstract objects which require six types of grasps with the developed prosthesis.