Low cost knee bionic prosthesis based on polycentric mechanisms

Introduction. This work, explains the process carried out to make a design of mechanism of knee of polycentric type of 4 bars with mechanical actuator for modular prosthesis. The goal, emulate behavior and functioning of the knee for flexion and extension covering the basic needs of people with trans-femoral amputation of external prostheses modular with a low cost of production. Materials and methods. The development of polycentric knee mechanism was conducted in 2 phases. The first was in the design and construction of the mechanism of 4 bars; It was constructed of 6063 aluminum, bronze and stainless steel, corrosion resistant, of machining relatively simple and whose total mass is 690 g; We used software design SolidWorks® and COMSOL Multiphysics® for analysis of efforts, also machines and tools for machining such as conventional lathe and the milling machine. In the second phase re-engineering was applied to the mechanism of 4 bars and built a device with better ergonomics; added a mechanical actuator based on a spring; tested in three patients: one nursing home, one of 16 years, both female and a third with medical history of diabetes, hypertension and heart problems; the two previous phases are described in this document. Results and discussion. At the end of the development of this design we obtain a mechanism for external type polycentric knee, according to the phases of movement, speed, ergonomics, shapes, sizes and weights significant of Mexican patients. Tested for stress analysis using finite element and concluded that the device met with the feature to modify its center of rotation depending on the angle of flexion of the knee and can be considered a polycentric mechanism.