In-silico modeling of induction heating of hip endoprostheses for facilitated intentional removal

In OECD countries, infections and loosening are the main reasons for revision surgeries in total hip arthroplasties (THA), accounting for about 10% of all THA procedures. The traditional method for implant removal is purely mechanical, involving chiseling and grinding to remove bone cement, which subjects the surrounding tissue to significant stress and poses a high risk of femoral fractures. A novel approach to tissue-conserving hip arthroplasty removal is the use of induction heating to weaken the interface between metallic implants and bone cement. An alternating electromagnetic field is applied transcutaneously, heating the implant's surface. For cemented arthroplasties, this heat softens the thermoplastic bone cement, releasing the metallic implant and allowing the cement to detach from the bone, facilitating removal. Precise control of the heat input and its duration are essential to minimize thermal damage to surrounding tissues. To predict the surface temperatures resulting from inductive heating of the paramagnetic implant material Co-28Cr-6Mo, an in-silico model was developed using Ansys Mechanical. This model will assist in designing inductors and heating strategies for precise and homogeneous heating at the implant-to-bone-cement interface. For this model, electromagnetic and thermal properties of the metallic implants were characterized, measuring thermal conduction coefficients and specific heat capacities.