Non-contact electromagnetic induction heating for eradicating bacteria and yeasts on biomaterials and possible relevance to orthopaedic implant infections

Abstract

ObjectivesInfection of implants is a major problem in elective and trauma surgery. Heating is an effective way to reduce the bacterial load in food preparation, and studies on hyperthermia treatment for cancer have shown that it is possible to heat metal objects with pulsed electromagnetic fields selectively (PEMF), also known as induction heating. We therefore set out to answer the following research question: is non-contact induction heating of metallic implants effective in reducing bacterial load in vitro?MethodsTitanium alloy cylinders (Ti6Al4V) were exposed to PEMF from an induction heater with maximum 2000 watts at 27 kHz after being contaminated with five different types of micro-organisms: Staphylococcus epidermidis; Staphylococcus aureus; Pseudomonas aeruginosa; spore-forming Bacillus cereus; and yeast Candida albicans. The cylinders were exposed to incremental target temperatures (35°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C) for up to 3.5 minutes.ResultsThere was an average linear heating rate of 0.39°C per second up to the target temperature, and thereafter the target temperature was maintained until the end of the experiment. At 60°C and higher (duration 3.5 minutes), there was a 6-log reduction or higher for every micro-organism tested. At 60°C, we found that the shortest duration of effective induction heating was 1.5 minutes. This resulted in a 5-log reduction or higher for every micro-organism tested.ConclusionNon-contact induction heating of a titanium disk is effective in reducing bacterial load in vitro. These promising results can be further explored as a new treatment modality for infections of metal orthopaedic implants.Cite this article: B. G. Pijls, I. M. J. G. Sanders, E. J. Kuijper, R. G. H. H. Nelissen. Non-contact electromagnetic induction heating for eradicating bacteria and yeasts on biomaterials and possible relevance to orthopaedic implant infections: In vitro findings. Bone Joint Res 2017;6:323–330. DOI: 10.1302/2046-3758.65.BJR-2016-0308.R1.

Synergy between induction heating, antibiotics, and N-acetylcysteine eradicates Staphylococcus aureus from biofilm

“…To validate the IR temperature measurements a Ktype thermocouple was used to compare the temperature measured with the IR sensor to the temperature measured with the thermocouple. These measurements were taken after the PEMF had been switched off, because the PEMF can affect the thermocouple measurements [7][8][9][10].…”

“…Titanium alloy coupons with biofilm were heated to temperatures of 50 C, 60 C, 70 C, 80 C, and 90 C for 3.5 min. The duration of 3.5 min was chosen to allow comparison to previous results of induction heating planktonic micro-organisms [9]. Experiments were repeated at least 5 times unless otherwise indicated.…”

“…Non-contact induction heating (NCIH) of metal implants is a new and emerging treatment for infected metal implants [7][8][9][10]. NCIH uses pulsed electromagnetic fields (PEMF) to induce so-called 'eddy currents' within metal objects which causes them to heat up.…”

“…Presently, several studies have shown the effectiveness of NCIH on metal implant in the reduction of bacterial load in vitro [7][8][9][10]. However, it is currently unknown whether NCIH can reduce or even eradicate S. aureus from the biofilm on a titanium alloy, which is commonly used for joint implants.…”

Remote acoustic sensing as a safety mechanism during exposure of metal implants to alternating magnetic fields

“…Although proof-of-concept studies demonstrate the ability of AMF to eradicate biofilm in vitro [ 14 , 15 ], there is a legitimate safety concern of potential thermal damage to surrounding tissues when considering heating implanted metal objects. This risk of thermal damage does not arise from direct AMF heating of tissues when the applied AMF has a relatively low frequency (hundreds of kHz), but rather heat conduction into tissue from the heated implant.…”