Electrical Impedance Characterization of Bone Fracture

Background: Differences in electrical characteristics of different tissues can provide information of the tissue composition at the fracture region. Real-time monitoring of bone healing with electrical impedance spectroscopy might pro- vide information for an individualized treatment of fracture patients. However, electrodes must be placed at a distance to the fracture site in order not to in- terfere with bone healing.
Purpose / Aim of Study: We investigated whether electrical impedance mea- surements from electrodes placed at a distance to a bone defect can detect differences between intact bone and bone defects in vivo.
Materials and Methods: Approval was granted from the Inspectorate of the Animal Experimentation of Danish Ministry of Justice. 6 rabbits were anaesthe- tized, and a fracture protocol was subjected to both tibias. Electrical impedance was measured in frequencies from 10 Hz to 1 MHz at each step: 1) intact bone, 2) medial defect, 3) medial and lateral defect, 4) complete 2 mm bone defect. One electrode was placed in the medullary canal and two electrodes extracorti- cal (lateral and posterior) 2 mm from the defect. For each rabbit, one tibia had measurements with a free inner electrode and the other tibia had measure- ments both with a nail and an isolated nail.
Findings / Results: For all tibias, the intact bone resulted in higher impedance compared with the complete defect, and this difference was most pronounced in the frequency range of 1kHz to 100 kHz. This applied for all types of elec- trodes including electrode, nail, isolated nail. The isolated nail showed the big- gest impedance difference between the intact bone and the complete defect. Incomplete bone defects had lower impedance compared with intact bone, but no consistent pattern for differences in impedance was observed between the different applied defects.
Conclusions: Consistent impedance differences between intact bone and complete defects were detected in-vivo in rabbits. Further research is needed to explore whether the presented method can be used to characterize bone healing over time.