Assessment of Non-Contact Induction Heating Characteristics of Metallic Biomaterials

Implant-associated infections are a severe concern affecting 1− 3 % of patients undergoing primary joint arthroplasty [1]. Magnetic hyperthermia, which can be non-invasively induced by applying an alternating magnetic field (AMF) around a metallic implant, is a new approach with great potential.

This research project explores the application of non-contact induction heating (IH) of metallic implants
in orthopedic surgery. It focuses on the heating behavior of paramagnetic biomaterials relevant to this
application in alternating magnetic fields.

Empirical testing plays an inherent role in research. However, it is often very time-consuming, especially when assessing many specimens. With in silico simulations, data can be yielded much faster. An analytical model simulating the heating dynamics of paramagnetic materials in the AMF was constructed to provide a tool for faster suitability assessment of metallic biomaterials for magnetic hyperthermia. The model was then compared with empirical data obtained in a controlled environment.

The empirical data showed a quadratically increasing temperature rise with the field amplitude and a linearly growing temperature rise with the frequency. The constructed analytical model confirmed that the heat generated in the materials increases quadratically with the increasing AMF amplitude.

Additionally, increasing the frequency of the AMF also affects heat generation. The model predicted different trends depending on what domain a material is assigned to. However, empirical data indicates a consistent linear relationship across several assessed frequencies and materials. Based on the obtained knowledge of the material’s behavior in AMF, a new hip implant intended for magnetic hyperthermia treatment was designed. It utilized a coating on the neck of the femoral stem, designed to enable targeted IH, particularly to regions most susceptible to bacterial infections.

The experiment featured a multi-material specimen consisting of Ti Gr. 23 and ST. 37, which mimicked
the neck of a hip implant, the proof of concept was successfully demonstrated, showing a significant temperature increase for specimens with coating compared to the ones without at high magnetic field
strength and frequency. However, targeted IH was not detected. Better computational models can further explore the obtained knowledge and the proof-of-concept can be further tested to investigate its contribution to treating resistant bacterial biofilms.

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