Revolutionising implants: Infection-resistant, 3D-printed metals

Researchers at Washington State University have created a groundbreaking surgical implant that demonstrated 87% effectiveness in destroying the bacteria responsible for staph infections in laboratory trials

The implant, detailed in the International Journal of Extreme Manufacturing, exhibited robustness and compatibility with surrounding tissues, comparable to existing implants.

This innovation holds the potential to significantly enhance infection control in routine surgeries like hip and knee replacements, addressing a major factor contributing to implant failures and adverse post-surgery outcomes.

Enhancing bacterial elimination efficiency

“Infection is a problem for which we do not have a solution,” said Amit Bandyopadhyay, corresponding author on the paper and Boeing Distinguished Professor in WSU’s School of Mechanical and Materials Engineering. “In most cases, the implant has no defensive power from the infection. We need to find something where the device material itself offers some inherent resistance — more than just providing drug-based infection control. Here we’re saying, why not change the material itself and have inherent antibacterial response from the material itself?”

“In most cases, the implant has no defensive power from the infection.”

The materials employed in hip and knee replacements and other surgical implants were developed over 50 years ago using titanium and are not well-equipped to combat infections.

Performance considerations

Despite preemptive antibiotic treatments by surgeons, life-threatening infections can arise shortly after surgery or manifest weeks or months later as secondary infections. In cases where infections form a fine film on the implant, systemic antibiotics are the primary treatment approach.

Approximately 7% of implant surgeries require revision surgery, involving the removal of the implant, thorough cleaning, antibiotic application, and inserting a new implant. Addressing these challenges, Washington State University researchers utilised 3D-printing technology to incorporate 10% tantalum, a corrosion-resistant metal, and 3% copper into the standard titanium alloy used in implants.

Utalising 3D printing

The copper surface of the material causes the rupture of almost all bacterial cell walls upon contact. The tantalum promotes healthy cell growth in the surrounding bone and tissue, accelerating patient healing. The researchers conducted an extensive three-year study of the implant, evaluating its mechanical properties, biological aspects, and antibacterial response in both laboratory settings and animal models. Additionally, they examined wear to ensure that metal ions from the implant do not wear off and migrate into nearby tissue, potentially causing toxicity.

“The biggest advantage for this type of multifunctional device is that one can use it for infection control as well as for good bone tissue integration,” said co-author Susmita Bose, Westinghouse Distinguished Professor in the school.

“Because infection is such a big issue in today’s surgical world, if any multifunctional device can do both things, there’s nothing like it.”

Maintaining performance

The research team is persisting in enhancing the bacterial death rate to exceed the standard 99%, all while ensuring optimal tissue integration. Their focus is on maintaining excellent performance under real-world loading conditions that patients may encounter, such as those involved in hiking, particularly in knee replacements.

Collaborating with WSU’s Office of Commercialisation, the researchers have taken steps to protect their innovation by filing a provisional patent. The project received financial support from the National Institutes of Health and involved collaboration with researchers from Stanford University and experts from WSU’s College of Veterinary Medicine.