Effect of Low-Intensity Pulsed Ultrasound on Bone Formation During Mandible Distraction Osteogenesis in a Canine Model—A Preliminary Study

Abstract

To make a preliminary study of the effect of low-intensity pulsed ultrasound on new bone formation during mandible distraction osteogenesis in dogs. Bilateral surgical cuts were made in mandibles of 7 dogs between the first and second premolar regions. Anterior mandibles were lengthened by 20 mm at the rate of 1 mm/day twice a day. During the distraction period 1 lateral distraction gap was irradiated by low-intensity pulsed ultrasound for 10 minutes twice a day and the other side was sham irradiated as control. After distraction was completed, the dogs were sacrificed at 0, 1, 2, 4, 6, 8, and 12 weeks. Before sacrifice, dynamic bone imaging with technetium (99)m-methylene diphosphonate ((99)mTc-MDP) single-photon emission computed tomography was performed. Mandible samples were harvested. Then plain x-ray, dual-energy x-ray bone mineral density measurement, 3-dimensional computed tomography, and regular histologic examination were performed. The (99)mTc-MDP bone imaging showed that uptake of (99)mTc-MDP in the experimental side was higher than in the control side at the early period of the consolidation time, but the outcome was later reversed. Plain x-ray showed that new bone of the experimental side was mature sooner than that of the control side. Bone mineral density in the experimental side was higher than that of the control side. Volume of new bone of the 2 sides had no significant difference. Histologic examination showed that trabeculae of the experimental side were more numerous and thicker than those of the control side at the early period of the consolidation time. Endochondral bone formation was observed in the experimental side. Low-intensity pulsed ultrasound could accelerate bone formation during mandibular distraction osteogenesis and increase bone mineral density but had no effect on the volume of new bone.