Evaluating Bone Fracture Healing in a Rabbit Model Using Doppler Imaging Modes, Shear Wave Elastography, X-Ray, and Dual-Energy X-Ray Absorptiometry.

Objective: This study investigated methods of evaluating the bone fracture healing process using superb microvascular imaging (SMI; two modes color SMI [cSMI] and monochromeSMI [mSMI]), and shear wave elastography (SWE), relative to X-ray, dual-energy X-ray absorptiometry (DXA), and platelet endothelial cell adhesion molecule 1 (PECAM-1) also know as cluster of differentiation 31 (CD-31) staining in a rabbit model.

Methods: This IACUC-approved study involved eight rabbits that underwent a bilateral fibula osteotomy and were followed for 7 or 21 days (Groups 1 and 2 with 4 rabbits in each). Ultrasound examinations using cSMI, mSMI, and SWE were performed on Days 0, 4, 7, 14, and 21 post-surgery. At the final time point, rabbits had X-ray imaging followed by euthanasia and DXA scan. Finally, the fracture areas underwent decalcification, and specimens were stained with CD-31 for pathological analysis. Ultrasound and X-ray findings were compared using ANOVAs or paired t-tests with CD-31 stains and DXA was used as a reference.

Results: Comparing SMI ultrasound images between the last time points for Group 1 (Day 7) and Group 2 (Day 21) showed no statistical significance difference for cSMI (P = .14) and mSMI (P = .06), similarly when compared with CD-31 stains there was no statistical significance difference for cSMI in Group 2 (P = .13). The SWE ultrasound images from the last time points in Groups 1 and showed no statistical significance difference (P = .33), the same results were then compared with DXA and also showed no statistical significance difference (P = .14). When comparing results of the X-ray images from the last time points for Groups 1 and 2 a statistical significance difference was found (P = .01), and when X-ray images were compared with DXA there was a statistical significance difference (P < .001).

Conclusion: Compared with CD-31 stains cSMI on Day 21 was not statistically significant (P = .13). Results comparing SWE with DXA were also not statistically significant (P = .14). These results indicate the potential of using certain ultrasound imaging techniques to monitor the bone fracture healing process.