Anti-bacterial silver lining for implants and 3D printed prosthetics

Prosthetic implants with enhanced resistance to bacterial infection could improve patient safety while reducing the use of antibiotics.

Most prosthetics carry a low risk of infection of below one per cent. But where implants are inserted following an accident, or must be produced at the hospital, the risk of infection can increase significantly, to up to 50 per cent.

Treating an infection involves removing the prosthetic and implanting a material that releases high levels of antibiotics to the site. This not only threatens the health of the patient, but risks adding to the rise of antibiotic-resistant bacteria.

Now, in an EPSRC-funded project, researchers at Birmingham University are developing implant designs and 3D printing techniques to produce surfaces that are resistant to bacterial contamination.

The team will combine technology to embed silver into the material used to build implants, with additive layer manufacturing to produce the prosthetics, according to Birmingham’s Prof. Liam Grover.

Using selective laser melting, they will use lasers to fuse powders together layer by layer, creating a porous structure to which the bacterial-resistant silver can be added.

Their first target for the technology will be to reduce infections following the implantation of metal plates into the skull.

These cranial implants must be refined to fit the patient. As a result, they are typically produced in hospital by bending a titanium sheet over a 3D printed model of the defect. They are then polished and dipped in acid, before being sterilised at over 100 degrees Celsius.

While this process typically kills most bacteria, the plates still carry a much higher risk of infection than other implants produced off-site.

“Obviously, if you have an infection near the brain, it can be really dangerous,” said Grover. “We think we can have a significant impact into reducing infection in this particular class of patients.”

The researchers also aim to alter the structure of the implants to allow them to be imaged by MRI scanners. They will use a technique known as topological optimisation to minimise the mass of titanium used while maintaining its mechanical properties.

The researchers will be working with clinicians at University Hospitals Birmingham and the Royal Orthopaedic Hospital NHS Foundation Trust, as well as companies such as Accentus Medical and Johnson Matthey, to develop the technology.

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