Low-Intensity Pulsed Ultrasound Accelerates Traumatic Vertebral Fracture Healing by Coupling Proliferation of Type H Microvessels

Objectives-Patients with traumatic vertebral fractures often have major associated postoperative morbidities such as healing failure and kyphosis. Low-intensity pulsed ultrasound (US) has been found to promote bone fracture healing. The objectives of our study were to determine whether low-intensity pulsed US could promote traumatic vertebral fracture healing and to explore its inner mechanisms. Methods-A rat model of traumatic vertebral fracture was created and treated with low-intensity pulsed US after surgery. At 4 weeks after surgery, radiographic, micro-computed tomography, and 3-dimensional reconstruction were used to assess the radiologic healing status; a histologic analysis was performed to evaluate the pathologic process and relationship between osteogenesis and type H microvessels. Results-Well-remodeled trabecular meshworks were found in the low-intensity pulsed US treatment group compared to the control group. Micro-computed tomography and 3-dimensional reconstruction revealed more and thicker trabeculae after low-intensity pulsed US treatment. Abundant chondrocytes, a newly formed bone marrow cavity, trabeculae, and microvessels were formed at the fracture sites. More osterix-positive osteoblasts were circling the newly formed bone meshwork and were situated at the interface of chondrocytes in the low-intensity pulsed US treatment group. Type H microvessels were spreading around the newly formed trabecula, bone marrow cavity, osteoblasts, and interface of chondrocytes, with a larger mean vascular density in the low-intensity pulsed US group. Conclusions-Low-intensity pulsed US could accelerate traumatic vertebral fracture healing by temporally and spatially increasing chondrogenesis and osteoblast-induced osteogenesis coupled with angiogenesis of type H microvessels in a rat model of traumatic vertebral fracture.