Wireless Measurements Using Electrical Impedance Spectroscopy to Monitor Fracture Healing

Abstract

There is an unmet need for improved, clinically relevant methods to longitudinally quantify bone healing during fracture care. Here we develop a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy (EIS) to provide real-time data on tissue composition within the fracture callus. To validate our technology, we created a 1-mm rabbit tibial defect and fixed the bone with a standard veterinary plate modified with a custom-designed housing that included two impedance sensors capable of wireless transmission. Impedance magnitude and phase measurements were transmitted every 48 h for up to 10 weeks. Bone healing was assessed by X-ray, µCT, and histology. Our results indicated the sensors successfully incorporated into the fracture callus and did not impede repair. Electrical impedance, resistance, and reactance increased steadily from weeks 3 to 7—corresponding to the transition from hematoma to cartilage to bone within the fracture gap—then plateaued as the bone began to consolidate. These three electrical readings significantly correlated with traditional measurements of bone healing and successfully distinguished between union and not-healed fractures, with the strongest relationship found with impedance magnitude. These results suggest that our EIS smart bone plate can provide continuous and highly sensitive quantitative tissue measurements throughout the course of fracture healing to better guide personalized clinical care.

The application of impantable sensors in the musculoskeletal system: a review

“…These applications include forces in joints, displacement during fracture healing, forces acting on dental implant prostheses, and bladder pressure ( Kim et al, 2012 ; D'Lima et al, 2013 ; Cho et al, 2014 ; Pelham et al, 2017 ). Fukase et al (2022) developed a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy to provide real-time data on tissue composition within the fracture callus. The sensor is wireless and can take readings up to 3 m from the implanted bone for up to 8 weeks.…”

Powering implanted sensors that monitor human activity using spider‐web coil wireless power transfer

“…These findings suggest that the MEMS sensor can evaluate the present stage of fracture healing and be used to anticipate fracture healing. Numerous works have discussed wireless data and power transfer in other biomedical applications, such as smart contact lenses [36], monitoring fracture healing [37], and other applications.…”

Electrical impedance detects early stages of bone healing: An in vivo explanatory study of tibial fractures in rabbits

“…Over time, changes in the resistive and capacitive properties occur as the bone heals resulting in change in the electrochemical nature of the tissue [ 23 ]. A limited number of studies have applied electrical impedance spectroscopy to in vivo animal bone fracture models [ 7 , 8 , 10 , 12 , 13 , 14 , 16 , 20 , 25 , 26 ]. All studies reported a consistently increased impedance over time across a range of frequencies, except one study [ 7 ].…”

“…All studies reported a consistently increased impedance over time across a range of frequencies, except one study [ 7 ]. Of these, only two in vivo studies measured impedance at low frequencies [ 8 , 27 ]. The animals chosen for the studies varied between mice and rabbits.…”