Magnetic Fields Kill Bacteria Infecting Medical Implants

Annually, millions of orthopedic devices are implanted in patients for various conditions, including skeletal trauma, joint injuries, and osteoarthritis. These devices, such as prosthetic joints, bone fixation hardware, and dental implants, are often made of metal. One of the most serious complications arising from metal prostheses is bacterial infection, affecting 1–3% of prosthetic joints and up to 30% of orthopedic trauma implants. Bacteria that produce biofilm on the surface of these implants make the infections particularly stubborn, often necessitating multiple surgeries and significantly limiting patient mobility for extended periods. Now, a novel, non-invasive method has been developed to eliminate biofilm from metal implants using intermittent alternating magnetic fields (iAMF) to generate targeted heating of the implant surface.

It's been known for over a century that alternating magnetic fields (AMF) can produce electrical currents in metal, generating heat. When the direction of the magnetic fields is rapidly changed back and forth at a high frequency, these electrical currents only flow along the metal's outer edge, a principle utilized in induction cooktops to heat skillets. Researchers at UT Southwestern Medical Center (Dallas, TX, USA) have applied this same technology used in induction cooktops to reduce bacterial presence in prosthetic joint infections. They combined this approach with antibiotics in a mouse model to further advance the concept developed by them in 2017 that showed AMF could kill biofilm-producing bacteria on metallic medical implants.

Image: Researchers have demonstrated potential for saving infected prosthetic joints in human patients (Photo courtesy of 123RF)

In their latest study, the team explored the effectiveness of this method in a more complex live animal environment. They cultured two types of biofilm-forming bacteria on stainless-steel balls and tested them in mouse models. Their findings indicated that combining the highest doses of AMF with antibiotics was more effective in reducing bacterial numbers than using AMF or antibiotics alone. Remarkably, even with these high doses, heat damage to surrounding tissues remained minimal, confined to about a millimeter around the implant. Future research will focus on understanding the synergistic action of AMF and antibiotics and aim to replicate these promising results.

“We previously demonstrated that AMF can reduce bacterial biofilm in the test tube. This study is the first to show that AMF can reduce bacterial biofilm in an animal model, which is an important next step in trying to get this technology into human clinical trials,” said study leader David Greenberg, M.D. “Our hope is that this year, we will be performing our first human studies to test the safety and tolerability of the AMF device followed by a pivotal clinical trial where we will measure both safety and efficacy.”

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UT Southwestern Medical Center