Effect of Low-intensity Pulsed Ultrasound on Healing of Bone Defects in Rat Tibia as Measured by Reconstructed Three-dimensional Analysis of Micro CT Images

Abstract

Background/Aim: The aim of this study was to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on bone metabolism during the healing period in rat tibiae bone defects using micro-computed tomography (micro CT) imaging for three-dimensional morphological evaluation. Materials and Methods: The right tibia received ultrasound exposure (US group) every day, whereas the opposite side served as a control (Control group). At 1, 2, and 3 weeks after the operation, micro CT was performed, and the volume and surface area of new bone formation in the bone defects was evaluated three-dimensionally. Results: Bone volume (BV) and bone surface (BS) in the tibiae of both the US and Control groups demonstrated the highest values 1 week after the operation, with no significant differences between the groups. At 2 weeks after the operation, the BV and BS values in both groups had decreased, but the decrease was smaller in the US group than the Control group. At 3 weeks after the operation, the BV and BS values in the Control group were significantly lower than those in the US group. Conclusion: LIPUS stimulation can prevent bone loss during the healing of bone defects.The healing of the extraction socket influences subsequent treatment in clinical situations such as severe alveolar bone resorption caused by periapical cysts, root fracture, or severe periodontal disease. Shortening the bone healing period while preserving bone quantity would be of benefit to patients as well as clinicians. Therefore, accelerating bone healing is clinically important.It is well known that the application of mechanical stress stimulates bone metabolism. This is supported by Wolff's law, which states that bone can adapt to the load under which it is placed and that mechanical stress promotes bone metabolism (1). Recent studies have demonstrated that bone metabolism can be controlled by mechanical stress, which stimulates not only bone resorption but also bone formation (2). From a clinical point of view, it is more important to investigate the mechanism of how mechanical stress affects bone metabolism. However, the detailed mechanism remains unclear.Considerable attention has focused on the application of low-power ultrasonic pulses (low-intensity pulsed ultrasound: LIPUS) as a non-invasive treatment approach (3). LIPUS is used in a variety of clinical applications, such as bone fracture treatment, treatment of periodontal disease, peri-implantitis, and ultrasonic irrigation in endodontics (4). For these reasons, we used LIPUS to analyze the effect of mechanical stress on bone metabolism.Micro-focus computed tomography (micro CT) is very useful for investigating the fine structure of bone, and some studies have used micro CT imaging to analyze bone structure in the XY, YZ, and YZ section planes. However, CT generates only two-dimensional images. In order to analyze the precise structure of bone tissue, threedimensional (3D) images must be constructed using micro CT imaging data.

Musculoskeletal Biomaterials: Stimulated and Synergized with Low Intensity Pulsed Ultrasound

“…In addition to the effective promotion of fracture repair, including new fractures, the method may also be of use in delayed union or nonunion and bone defects [84][85][86][87]. Meanwhile, LIPUS therapy may be a useful means to ensure successful spine fusion (Table 2).…”