Washington State Develops Infection-Resistant Metal Implants with Additive Manufacturing

A surgical implant has been developed by researchers at Washington State University (WSU), Pullman, Washington, that is able to kill 87% of staph infections bacteria in laboratory tests, while remaining strong and compatible with surrounding tissue.

The research, reported in the International Journal of Extreme Manufacturing, could lead to better infection control in common surgeries, such as hip and knee replacements. Bacterial colonization of the implants is one of the leading causes of their failure after surgery.

“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?”

Titanium materials have stood the test of time for surgical implants but are not well suited to overcoming infections. Although antibiotics are used preemptively, life-threatening infection can occur right after surgery or months later as a secondary infection. In about 7% of implant surgery cases, doctors have to perform a revision surgery, removing the implant, cleaning the area, adding antibiotics and putting in another implant.

The WSU researchers used a metal AM process and added 10% tantalum, a corrosion-resistant metal, and 3% copper to the typical implant titanium alloy. When bacteria meet the material’s copper surface, almost all cell walls rupture. The tantalum encourages healthy cell growth with surrounding bone and tissue leading to expedited healing for the patient. The researchers also studied its wear to make sure that metal ions from the implant won’t wear off and move into nearby tissue causing toxicity.

The researchers are continuing the work, hoping to improve the bacterial death rate to the standard of more than 99% without compromising tissue integration. They also want to make sure that the materials offer good performance under real-world loading conditions that patients might use, such as for hiking in the case of a knee replacement.