Design, Modeling, and Evaluation of the Eddy Current Sensor Deeply Implanted in the Human Body

Abstract

Joint replacement surgeries have enabled motion for millions of people suffering from arthritis or grave injuries. However, over 10% of these surgeries are revision surgeries. We have first analyzed the data from the worldwide orthopedic registers and concluded that the micromotion of orthopedic implants is the major reason for revisions. Then, we propose the use of inductive eddy current sensors for in vivo micromotion detection of the order of tens of μm. To design and evaluate its characteristics, we have developed efficient strategies for the accurate numerical simulation of eddy current sensors implanted in the human body. We present the response of the eddy current sensor as a function of its frequency and position based on the robust curve fit analysis. Sensitivity and Sensitivity Range parameters are defined for the present context and are evaluated. The proposed sensors are fabricated and tested in the bovine leg.

Development of a Multi-Sensor Array for Non-Radiographic Micromotion Detection of Joint Prostheses

“…There have been new developments in implant motion detection that are comparable to this system. Two notable examples are the use of eddy current sensing, reporting a resolution of 0.15 mm [15] and the use of nanoparticles in cement with simulation modelling highlighting a resolution of 0.3 mm [40] . However, these systems are still at their early development stage and require further work to address issues of proximity and biocompatibility [15,29].…”

“…More recently, other sensor-based implant displacement techniques have emerged such as eddy current sensors [15] and piezoelectric nanoparticles [29] that can theoretically achieve sub-millimeter resolution. However, they are still in the experimental or theoretical stage with further development needed to address issues such as biocompatibility.…”

“…The outcomes are also poorer than primary surgery [14]. The ratio of primary surgery to revision surgery, known as the revision burden, ranges from 6 to 30 % across different national joint registries [15]. These rates are up to 3 times higher than hip, knee, and shoulder arthroplasty (5-11 %).…”

A Modified Wireless Power Transfer System for Medical Implants

“…According to (6), for the parallel-secondary circuit, the reflected impedance is expressed as the reflected resistance and the reactance, at the resonance…”

“…For this reason, technology is always looking for a solution to make powering implants easier, safer, more efficient, and more comfortable. According to the literature, there are multiple attempts and proposals for powering implants like electric wires, batteries, energy recovery through the human body (piezoelectricity, magnetic induction generators, and electrostatic generators), and energy recovery from the environment (thermal energy, infrared radiation, and wireless power transfer (WPT)) [6,7]. WPT is the transfer of electrical power from a transmitter point to a consumer power device through the air, vacuum or another environment without the use of wires or any intermediate material.…”