Assessment of distraction callus in rabbits by monitoring of the electrical impedance of bone

Abstract

Background and purposeEvaluation of distraction callus is important for determination of the optimal time for removal of external fixation. We attempted to determine whether there might be a relationship between the electrical impedance of bone and callus maturation, with a view to using impedance as a way of knowing when to remove a fixator.MethodsWe applied an external lengthener to the right tibia of 24 rabbits and performed distraction at 1 mm/day for 10 days. Radiographs were taken and measurement of overall impedance between fixation pins was performed weekly after distraction. At weeks 2, 4, 6, and 8 after distraction (n = 6 each), resistivity of the bone to electrical conductivity was measured before killing. Cross-sectional area of the conduction pathway in callus and maximum bending stress were measured after excision of the tibia.ResultsThe overall impedance increased statistically significantly from 1 to 6 weeks after completion of distraction. The resistivity of bone decreased over 4 weeks and the cross-sectional area of callus decreased significantly over 6 weeks, while the maximum bending stress increased significantly over the same time. We observed a negative correlation between the cross-sectional area of callus and maximum bending stress.InterpretationThe impedance values, which are related to changes in electrical conductivity and the conduction pathway, increased due to the changes in the cross-sectional area of callus, despite the reduction in bone resistivity. Since the cross-sectional area of callus was correlated with maximum bending stress and the impedance values increased with the callus-remodeling process, we suggest that temporal increases in overall impedance reflect callus maturation.

New opportunities for fracture healing detection: Impedance spectroscopy measurements correlate to tissue composition in fractures

“…Our results are consistent with previous findings that describe an increase in |Z| over healing time . However, our study provides more comprehensive information about the behavior of θ as a function of frequency and time.…”

“…Because EIS can capture changes in dielectric properties and a healing fracture is dominated by different tissues, it may be able to uniquely complement a technique like X‐ray that relies on tissue mineralization by providing quantitative local information about the fracture callus, particularly at early stages. In addition, prior work has used EIS to track differences over healing time between fracture and control groups . While these data are promising, these studies are limited to fractures treated via external fixation using long metal pins as electrodes.…”

“…In addition, prior work has used EIS to track differences over healing time between fracture and control groups. [18][19][20][21][22] While these data are promising, these studies are limited to fractures treated via external fixation using long metal pins as electrodes. These results as well as other work involving noninvasive measurements [23][24][25] suffer from limited dynamic range due to noise from surrounding soft tissue.…”

Muscle Force Measurement System for Long-Term Monitoring During Distraction Osteogenesis

“…[1,2,15,21] As to tensile force measurement, devices with strain gauges have been used in several studies in different animal species. [1,[3][4][5][6] However, the structures were not distinctly revealed, and several designs were for oral surgery or the effects of the measured forces were not presented.…”

“…The bone healing was examined by X-ray, histology, impedance analysis, or force measurement. [1,[3][4][5][6][7][11][12][13][14][15] Post-operative complications involving circumferential soft tissues are the most common concern in distraction osteogenesis. Both the invasive wound and the tension force from the distractor affect the muscles, ligaments, tendons, and nerves.…”