This paper presents the design methods followed in order to overcome the limits of the current prosthetic hands. The prosthesis biomechatronic approach arises from the knowledge of the biological system, assumed validated by its natural evolution. Nevertheless, the state of the art of technology, actuators, sensors, electronics and software, forces some trade-off in the implementation of the prototypes. The current hand prototype constitutes the platform used to direct all efforts of the prosthesis designer to the final goal: the cybernetic hand directly connected to the nervous system.