An implantable, battery-free sensing system for monitoring of spinal fusion

In this study, we investigate the feasibility of a self-powered Fowler-Nordheim (FN) sensor-data-logger for postoperative monitoring of spinal fusion progress. The FN sensor-data-logger self-powers itself using the energy harvested by a piezoelectric transducer attached to the spinal fixation device. The same signal is then used by the sensor to infer the fusion progress. We perform experimental studies using corpectomy models to evaluate the performance of the proposed monitoring system. Data measured from the bench-top experiments is used to obtain time-evolution curves representing each spinal fusion state. This feasibility study shows that the obtained curves are viable tools to differentiate between conditions of osseous union and assess the effective fusion period.