The prosthesis of hands in some of the cases allow to reach the same functionality that has a real hand. For this reason, in the development of this document we present a functional hand and forearm prosthesis, which allows providing a replacement option to those who, due to lack of development of this part of the body or an amputation, do not have this limb. To design this prototype, first some calculations of forces and torques that the proposed system can support are made. Then, with the support of a model designed in the software of Autodesk, simulations are found in which the design is subjected to external forces, giving as results the forces, deformations, tensions, among others, to which the prototype can operate.