Impact of a Titanium Tibial Implant on the Wireless Charging of a Biomedical Knee Sensor

Wireless Inductive Power Transfer (WIPT) technology is well suited for biomedical devices as it enables non-invasive charging. This lengthens the operating lifespan of biomedical implants and eliminates the need for further surgeries to remove implants to change their batteries. This paper proposes a magnetic coupler to wirelessly charge a Ligament Balance Measuring System (LBMS) for Total Knee Arthroplasty (TKA) and examines the impact of using a titanium tibial (TiT) component as opposed to a full plastic tibial (PT) component in TKA on the inductive power transfer system. A curved structure is used in the magnetic coupler to utilize the geometry of the knee and sensor. The proposed coupler achieves a coupling coefficient of 0.0286, a 0.2°C temperature increase in biomedical implant due to eddy current heating, a maximum magnetic field strength of 8.5A/m, a peak average SAR of 83 mW/kg and theoretical coil-to-coil efficiency of 88.6% with TiT components. However, with a PT component, the coupling coefficient increases marginally to 0.032, the temperature increase in the biomedical implants due to eddy current heating remains the same at 0.2 °C, the maximum magnetic field strength drops to 4.3 A/m, the peak average SAR drops to 51 mW/kg, and theoretical coil-to-coil efficiency increases to 89.7%. Therefore, the performances of the proposed couplers with the PT outperform the coupler with TiT.