Análisis, diseño y construcción de una nueva alternativa de fijación interna para el quinto metacarpiano empleando un polímero biodegradable

Abstract

Intramedullary devices for treatment of bone fractures are an effective available method. A new intramedullary locked nail for the fifth metacarpal bone, using a degradable and biadsorbable polyester Poly(p-dioxanone (PPDX) reforzed with boron nitride (BN), has been designed in order to reduce the immobilization time of the injured zone, enabling faster bone tissue healing and avoiding further surgery. Therefore, this nail allows for earlier functional ability of the bone. The name of the selected polymer is polydyoxanone PPDX ó PDS. When it is nucleated with Boron Nitride BN, it́s mechanical and biomedical properties improve, which fulfil design requirements. PPDX belongs to the aliphatic polyesters family approved by the FDA (Food and Drug Administration) and it is bio inert. Intramedullary nail design were 3Dgeometricly modelled through Computer Aided Design (CAD), which allowed the analysis of the prototypes when submitted to static charges by element finite method (EFM). These loads like bending, tension, and compression simulate habitual hand movement forces, reaching solution values approximate to the real system. The EMF results show that both devices fulfil design requirements and the necessary strength provides a total fracture stability BN-reinforced PPDX but not reduce the immobilization time as pretend. However, PPDX/BN guaranty clinical observation during biodegradation and bioadsortion time. Finally, the new intramedullary locked nail mold matrix for the fifth metacarpal bone was manufactured with 1020 steel and injection transference mold was made, by polyurethane for laboratory scale. Then proceed to inject the melted biopolymer into the mold and obtained the intramedullary device. © Springer-Verlag Berlin Heidelberg 2007.