Demonstrating the feasibility of monitoring bone fracture healing using electromechanical impedance spectroscopy – a comparison between three different inputs in Ward’s hierarchical clustering method

Abstract

Current methods for monitoring the progression of bone fracture healing require large, complex, and expensive imaging technology and, if used repeatedly, can expose patients to harmful ionizing radiation. Recent development of miniaturized, implantable, inexpensive microelectronic sensing technology now makes it possible to continuously monitor fracture healing non-invasively at the patient's bedside. This proof-of-concept study demonstrates a novel, smart, implantable medical device based on electromechanical impedance spectroscopy. The setup consists mainly of a piezoceramic disk (PIC255 from PI Ceramics), an impedance chip (AD5933 from Analog Devices) and an inductive battery recharging system. The system operates autonomously for 24 hours of measurements. Every 20 minutes, the health state of the bone is measured. To test the setup, 20 tibia bones of sheep limbs obtained from a butcher's shop are used. By drilling five holes into the bone one after another, different defects mimicking bone fractures of different sizes are created. This simulates an inverse bone healing process. The collected data is transmitted via Bluetooth LE to a portable device that displays the impedance spectra. After the results have been reviewed, the data is transferred to a computer for statistical evaluation, such as the Root Mean Square Deviation (RMSD). Preliminary results have shown an increasing trend in RMSD with increasing number of holes in the bone. Based on these observations, an in-vivo study is planned.