Feasibility analysis of wireless power delivery to implanted sensors of XLIF patients

Abstract

The paper aims to aid in developing a monitoring system for surgery patients who have undergone lumbar interbody fusion (LIF). The present body of work functions as a comprehensive analysis of relevant available literature along with our investigation regarding techniques for power delivery; both energy harvesting and wireless power transfer (WPT) alike. In addition, biological considerations are taken into account as they strongly influence the design and testing methodology of an implanted medical device (IMD). This study proposes using inductive coupling as a power delivery method. This was chosen due to the robust nature of the technology, with the IMD being deeply situated and encased in bone and tissue. Three types of receiver coil architectures were explored and designed around the geometry of a polyether ether ketone (PEEK) Extreme lateral interbody fusion (XLIF) Nuvasive Coroent XL interbody cage. With the use of off-the-shelf components, functionality was only attainable for the V3 coil design featured with 0.4 mm wire windings around horizontal and vertical beams present on the implant. The secondary coil was resonantly tuned and optimized for a 141 kHz working frequency. At a 100 mm coupling distance, it was demonstrated that a power delivery load (PDL) of 3.94 mA was able to be induced resulting in a power output of 7.21 mW. The recorded PDLs are capable of powering a high pressure P122 sensor, EFM8BB52 microcontroller, and Ultra-wideband (UWB) data telemetry link, and demonstrate the feasibility of this WPT technique for in vivo monitoring of bone fusion post XLIF surgery.