Development of a Novel Carbon-Fiber Mono-Lateral External Fixator

This paper reports the design of an innovative mono-lateral external fixator made of carbon fiber composite materials. The designed system can be easily assembled in comparison with commercial fixators and follows orthopedic requirements with sufficient stability and stiffness. The change of operation mode between distraction and fixation is achieved with a wedge that blocks axial translation in one position, while allows sliding with a 90o rotation. The prototypes were produced by the method of molding by compaction. A mold was developed for each part; the rail, the clamp and the cover. Each mold consisted of a cavity that gave form to the piece and a piston that exerted pressure on the composite. Mechanical tests were performed to determine the stiffness under axial compression, and anteroposterior and mediolateral bending. For comparison, tests were also performed on two Orthofix commercial systems, one with the rail made of carbon fiber and the other with an aluminum rail. The axial compression, anteroposterior and mediolateral bending stiffness of the developed system were 200.7, 13.4 and 87.0 N/mm, respectively, which were 38%, 35% and 27% lower than those obtained for the Orthofix system. However, these values were in the range of other similar systems reported in the literature. Therefore, the developed system presented promising results and may be clinically evaluated.