2020 journal article
An Implantable Wireless Inductive Sensor System Designed to Monitor Prosthesis Motion in Total Joint Replacement Surgery
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, 67(6), 1718–1726.
Currently, the most common method for detecting prosthetic implant loosening is imaging. Unfortunately, imaging methods are imprecise in detecting the early signs of implant loosening. This paper describes a new wireless inductive proximity sensor system for detecting early implant loosening. The loosening of the implant is accurately detected by analyzing the electromagnetic field generated by the passive sensors located around the implant. The sensor system was modeled and simulated using COMSOL, and then tested experimentally. The inductive proximity sensor and the metallic implant form a coupled circuit is tuned to oscillate at a designed frequency. The circuit's integrated controller measures and records specific sensor's parameters such as resistance and inductance of the sensor that are directly related to the distance between the sensor system and the implant. A prototype has been developed and the results show that the designed proximity sensor is capable of measuring the loosening of the hip implant at 50 μm resolution at distances of less than 8 mm, and of 100 μm resolution at a distance of 15 mm. Furthermore, there is a good correlation between the simulated and experimental results.