Employing direct electromagnetic coupling to assess acute fracture healing: An ovine model assessment

Abstract

Objectives: This study explored the efficacy of collecting temporal fracture site compliance data via an advanced direct electromagnetic coupling (DEC) system equipped with a Vivaldi-type antenna, novel calibration technique, and multi-antenna setup (termed maDEC) as an approach to monitor acute fracture healing progress in a translational large animal model. The overarching goal of this approach was to provide insights into the acute healing dynamics, offering a promising avenue for optimizing fracture management strategies.

Methods: A sample of twelve sheep, subjected to ostectomies and intramedullary nail fixations, was divided into two groups, simulating normal and impaired healing scenarios. Sequential maDEC compliance or stiffness measurements and radiographs were taken from the surgery until euthanasia at four or eight weeks and were subsequently compared with post-sacrifice biomechanical, micro-CT, and histological findings.

Results: The results showed that the maDEC system offered straightforward quantification of fracture site compliance via a multiantenna array. Notably, the rate of change in the maDEC-measured bending stiffness significantly varied between normal and impaired healing groups during both the 4-week (p = 0.04) and 8-week (p = 0.02) periods. In contrast, radiographically derived mRUST healing measurements displayed no significant differences between the groups (p = 0.46). Moreover, the cumulative normalized stiffness maDEC data significantly correlated with post-sacrifice mechanical strength (r² = 0.80, p < 0.001), micro-CT measurements of bone volume fraction (r² = 0.60, p = 0.003), and density (r² = 0.60, p = 0.003), and histomorphometric measurements of new bone area fraction (r² = 0.61, p = 0.003) and new bone area (r² = 0.60, p < 0.001).

Conclusions: These data indicate that the enhanced maDEC system provides a non-invasive, accurate method to monitor fracture healing during the acute healing phase, showing distinct stiffness profiles between normal and impaired healing groups and offering critical insights into the healing process's progress and efficiency.

Keywords: Acute fracture healing; Biomechanical monitoring; Direct electromagnetic coupling (DEC); Fracture compliance; Ovine model; Radiographic union score for tibia (mRUST).