Bioabsorbable Bone Screw with Iron Oxide Nanoparticles for X-ray Detection

The patent creates a composite material by incorporating iron oxide nanoparticles into the PLA matrix. This composite approach achieves X-ray detectability through the iron oxide content while maintaining biocompatibility, as iron oxide is naturally occurring and non-toxic unlike barium sulfate or bismuth bromide. The composite structure allows the bone screw to be both radiographable and safe for implantation in human bone.

The patent changes the type of radiopaque additive from conventional radiopaque materials (barium sulfate, bismuth bromide) to iron oxide nanoparticles. This parameter change in the additive composition maintains the desired X-ray detectability while fundamentally improving biocompatibility. The iron oxide nanoparticles provide sufficient radiopacity at concentrations that do not compromise the biodegradability or biocompatibility of the PLA matrix.

The patent transforms pure PLA into a composite material by dispersing iron oxide nanoparticles throughout the PLA matrix. This composite structure maintains the biocompatible and biodegradable properties of PLA while adding X-ray detectability through the iron oxide component. The nanoparticle dispersion ensures uniform radiopacity without compromising the material's ability to degrade naturally in the body.

The patent applies local quality enhancement by concentrating iron oxide nanoparticles in specific regions or at controlled concentrations within the PLA matrix. The cap member and screw member contain 0.5 to 40 weight percent iron oxide nanoparticles, creating localized radiopacity that provides sufficient X-ray detectability while maintaining overall biocompatibility. This localized approach allows optimization of radiopacity in critical areas without uniformly compromising biodegradability throughout the entire implant.

The patent applies preliminary action by pre-mixing the iron oxide nanoparticles with the PLA material before the injection molding or 3D printing process. The nanoparticles are incorporated into the PLA matrix in advance, creating a homogeneous composite material that can then be directly processed using conventional manufacturing techniques. This preliminary mixing step simplifies the overall manufacturing process compared to attempting to add nanoparticles during or after the forming process.

The patent changes the manufacturing approach to accommodate nanoparticles by using injection molding or 3D printing processes that can handle nanoparticle-containing materials. These processes allow for controlled heating and mixing that ensures uniform nanoparticle distribution throughout the PLA matrix during the forming process itself, rather than requiring separate mixing steps. The parameter changes in processing temperature and method enable seamless integration of nanoparticle incorporation with the manufacturing process.