Healing after bone fracture is assessed by frequent radiographs, which expose patients to radiation and lacks behind biological healing. This study aimed to investigate whether the electrical impedance using electrical impedance spectroscopy correlated to quantitative scores of bone healing obtained from micro-CT and mechanical bending test. Eighteen rabbits were subjected to tibial fracture that was stabilized with external fixator. Two electrodes were positioned, one electrode placed within the medullary cavity and the other on the lateral cortex, both three millimeters from the fracture site. Impedance was measured daily across the fracture site at a frequency range of 5 Hz to 1 MHz. The animals were divided into three groups with different follow-up time: 1, 3 and 6 weeks for micro-CT (Bone volume/tissue volume (BV/TV, %)) and mechanical testing (maximum stress (MPa), failure energy (kJ/cm3), young modulus (Mpa)). There was a statistically significant correlation between last measured impedance at 5 Hz frequency immediately prior to euthanasia and BV/TV of callus (−0.68, 95%CI: (−0.87; −0.31)). Considering the mechanical testing with three-point bending, no significant correlation was found between last measured impedance at 5 Hz frequency immediately prior to euthanasia and maximum stress (−0.35, 95%CI: (−0.70; 0.14)), failure energy (−0.23, 95%CI: (−0.63; 0.26)), or young modulus (−0.28, 95%CI: (−0.66; 0.22)). The significant negative correlation between impedance and BV/TV might indicate that impedances correlate with the relative bone volume in the callus site. The lack of correlation between impedance and mechanical parameters when at the same time observing a correlation between impedance and days since operation (0-42 days), might indicate that the impedance can measure biological changes at an earlier time point than rough mechanical testing.
Home-based monitoring of fracture healing has the potential of reducing routine follow-up and improve personalized fracture care. Implantable sensors measuring electrical impedance might detect changes in the electrical current as the fracture heals. The aim was to investigate whether electrical impedance correlated with radiographic fracture healing. Eighteen rabbits were subjected to a tibial osteotomy that was stabilized with an external fixator. Two electrodes were positioned, one electrode placed within the medullary cavity and the other on the lateral cortex, both three millimeters from the osteotomy site. Transverse electrical impedance was measured daily across the fracture site at a frequency range of 5 Hz to 1 MHz using an Analog Discovery 2 Oscilloscope with Impedance Analyzer. Biweekly x-rays were taken and analyzed blinded using a modified anterior-posterior (AP) radiographic union score of the tibia (RUST). Each animal served as its own control by performing repeated measurements from time zero until the end of follow-up.Introduction and Objective
Materials and Methods
