Abstract
Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin. Finite element analysis (FEA) simulations demonstrate that intermittent AMF exposures can achieve uniform surface heating of a prosthetic knee joint. In vivo studies confirm thermal damage is confined to a localized region (<2 mm) around the implant, and safety can be achieved using acoustic monitoring for the presence of surface boiling. These initial studies support the hypothesis that AMF exposures can eradicate biofilm on metal implants, and may enhance the effectiveness of conventional antibiotics.
Highlights
Each year in the United States, over one million total knee and hip replacement procedures are performed[1], and these numbers are projected to increase by 673% and 174%, respectively, by the year 2030 with current population trends and increases in the rates of obesity and diabetes[2,3,4]
There was a statistically significant reduction in colony-forming units (CFU) observed after 2 minutes (p < 0.01), and a greater than 3-log reduction (p < 0.0001) observed after 5 and 7 minutes for P. aeruginosa and S. aureus respectively
The observed trends were very similar for both PA01 and JE2, suggesting that the mechanism of bacterial killing is a direct physical effect of the heat produced by the alternating magnetic fields (AMF)
Summary
Each year in the United States, over one million total knee and hip replacement procedures are performed[1], and these numbers are projected to increase by 673% and 174%, respectively, by the year 2030 with current population trends and increases in the rates of obesity and diabetes[2,3,4]. The gold standard in the US for treating PJI is a two-stage revision arthroplasty[6] In this procedure, the infected implant is removed in a first surgery, the patient is placed on antibiotics for weeks to months to ensure complete eradication of bacteria, a new prosthesis is implanted via a second surgery[6]. Since biofilm is attached to the surface of implants and is less than 1 mm thick, rapid thermal destruction should be achievable while avoiding significant thermal damage to surrounding tissues since only a small fraction of the total volume of a metal implant is heated, and the low electrical conductivity of tissue causes negligible direct heating in these regions This treatment strategy is only targeted at the biofilm associated with metal implants, but could be used in concert with traditional antimicrobials to treat planktonic bacteria and achieve complete treatment of PJI
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