Color Doppler ultrasound visualizes early post-traumatic heterotopic ossification in animal model

Objective To validate the role of color Doppler ultrasound in an animal model to detect early heterotopic ossification (HO) after brain-traumatic/burn/tenotomy. Methods Forty-four rats were randomly divided into two groups. Rats in experimental group (n=22) were operated to build brain-traumatic/burn/tenotomy model and others in control group (n=22) underwent only skin incision injury. Color Doppler ultrasound, X-ray film examination at 2, 3, 4, 6, 8 and 10 weeks post-injury were performed to follow up the progression of HO in both groups respectively. Histology was used to confirm bone formation. Results In the experimental group, disorder structure with a hypoechoiccore in treated Achilles tendon was visualized using color Doppler ultrasound in the 2nd week. Additional tiny hyperechoic foci were observed in the 3rd week, which increased in the fourth week and fused into a mineralized island in the sixth week. No obvious abnormality was found in control group at the aforementioned time point. X-ray could detect heterotopic bone tissue in the sixth week in the experimental group but not in the control group. X-ray and HE stainning had confirmed bone formation in the tenth week in the experimental group. Conclusions Color Doppler ultrasound can detect early HO and continuously follow up the progression of HO. Key words: Ultrasonography; Heterotopic ossification; Animal model; X-ray